DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0062] For the description to follow, the same reference numerals are utilized in the Figures to refer to the same or similar components in the drawings. Referring now to FIG. 1, a base station or cell site 10 includes at least one and typically multiple antennas 12 , which radiate and receive radio frequency signals to support wireless communications. The antennas or antenna arrays 12 are mounted in a conventional manner on a base station tower 14 or similar functioning structure such as a building. As utilized herein, an antenna array is an assembly of antenna elements with dimensions, spacing, and illumination sequence such that the fields for the individual radiator elements combine to produce a maximum intensity in a particular direction and minimum field intensities in other directions. The term array antenna can be used interchangeably with antenna array in describing such an assembly.

[0063] Each of the base station antenna arrays 12 provides coverage to a cell of a mobile or fixed communication system (not illustrated), such as for cellular transmissions operating at approximately 800 MHz, Personal Communication Services (PCS) transmissions operating at approximately 1900 MHz in the United States (US) or other wireless communication applications with fixed or mobile users of the system, such as within one or more coverage areas 16 . The coverage of the base station 10 may not include all of the coverage area 16 . For example, a structure or building may interfere with the signal strength at a building 18 , illustrated as being on the periphery of the coverage area 16 , but which could be most anywhere in the coverage area 16 . Sufficient signal strength may be available, however, for signal enhancement to support the delivery of communications services to the user. Another service coverage problem can be the service available to the user within a structure or building 22 , even though the building is within the coverage area 16 . This can be caused by any number of problems, such as the construction of the building 22 or other sources of blockage or multi-path signal interference, which can again cause the signal strength to be insufficient for use by the user without enhancement of the signal.

[0064] Another limitation on the service coverage of the base station 10 is the interference by natural or manmade structures, such as a hill or mountain 24 , as illustrated in FIG. 2 . The hill 24 causes interference with the signal radiated from the base station 10 in an area 26 , called shadowing. The signal which reaches the shadow area 26 again will not be sufficient for use by a user, such as in a building or location 28 , without enhancement of the base station signal.

[0065] One solution to providing sufficient signal coverage in the shadow area or zone 26 is illustrated in FIG. 3 . A repeater 30 generally is mounted on a tower 32 or similar functioning structure. The tower is typically positioned either in the cell coverage area of the base station 10 or close enough that the signal strength received on a donor antenna 34 is sufficient to be amplified and retransmitted by a reradiation or server antenna 36 to a mobile station 38 , such as a cellular phone in the shadow zone 26 . The mobile station 38 , also described as a subscriber unit or terminal, can be inside a building (not illustrated) within the zone or can be a location within the zone 26 .

[0066] Another solution for the communication problem of the limited cell coverage area 16 is illustrated in FIG. 4 . Again, the repeater 30 is located either at the edge of the coverage area 16 , as illustrated, or outside the area 16 , but where the signal from the base station 10 is sufficient to be amplified for retransmission. Here, an area 40 of desired coverage is not a shadow area but is wholly or partially beyond the coverage area 16 . The area 40 can be selected to cover any permanent location of the user or users, such as the building or location 20 in FIG. 1 .

[0067] As illustrated in FIG. 5 , the repeater 30 generally is mounted on the tower 32 in a fixed location. The donor antenna 34 faces the base station 10 and generally is physically isolated from the server antenna 36 , by being spaced away from one another along the length of the tower 32 . The repeater 30 requires electronics 42 to amplify and retransmit the signals to and from the user station 38 . The electronics 42 include at least a pair of amplifiers 44 and 46 , one to amplify the downlink signal from the base station 10 and one to amplify the uplink signal from the user station 38 .

[0068] The conventional solution for extending service coverage, as illustrated in FIG. 4 and 5 , generally involves extending the service coverage to a relatively wide area of coverage. In contrast, exemplary embodiments of the present invention, as described below, provide signal enhancement in a comparatively more confined area or space that is typically indoors and has a coverage area of typically up to five thousand (5,000) square feet based on the use of a single, portable signal enhancement unit.

[0069] A block diagram of a conventional repeater 30 is illustrated in FIG. 6 . The repeater 30 includes the donor antenna 34 , which couples a downlink signal from the base station 10 through a duplexer filter 48 into a forward band or downlink path 50 . The downlink signal can be, for example, in the frequency band of 1930 to 1990 MHz. The downlink signal is amplified by the amplifier 46 and then coupled through a duplexer filter 52 to the server antenna 36 for transmission to the user. Transmission signals from the user are received by the server antenna 36 and coupled through the duplexer filter 52 into a reverse band or uplink path 54 . The uplink signal can be, for example, in the frequency band of 1850 to 1910 MHz, separated from the downlink signal frequency band by 20 MHz for isolation between the signals. The uplink signal is amplified by the amplifier 44 and then coupled through the duplexer filter 48 to the donor antenna 34 for transmission to the base station 10 .

[0070] The conventional repeater 30 illustrated in FIG. 6 uses duplexer filters 48 and 52 to separate the uplink 54 and downlink 50 path signals for amplification. The conventional repeater 30 uses a single donor antenna and a single server antenna and each antenna has a single characteristic polarization for reception and transmission of signals. In contrast, exemplary embodiments of the present invention do not use duplexer filters 48 and 52 . As described in more detail below, these exemplary embodiments typically use a single donor antenna and single server antenna, where each antenna has two characteristic polarizations: one characteristic polarization for reception of signals and one characteristic polarization for transmission of signals. Further, the characteristic polarization used for transmission of signals from the donor antenna is not the same as the characteristic polarization for reception of signals by the server antenna. Similarly, the characteristic polarization used for reception of signals by the donor antenna is not the same as the characteristic polarization for transmission of signals from the server antenna.

[0071] One of ordinary skill in the art will recognize that the aforementioned scenarios for coverage enhancement and coverage extension for communications can be for two-way communications and the description of service coverage can apply to the signal conditions for uplink signals as well as for downlink signals. One of ordinary skill in the art also will recognize that imbalances in the communication link design or local propagation conditions can result in temporary or long-term imbalances in the up and down communication links that favor one signal path more than the other. Therefore, a repeater may operatively improve the signal coverage on one of the links or bi-directionally on both links.

[0072] Referring to FIG. 7, a conventional coupled interference cancellation system (CICS) repeater 60 is illustrated, such as described in U.S. Pat. No. 6,385,435 B1. In addition to the elements described with respect to the repeater 30 , the repeater 60 provides circuitry to reduce the feedback or coupled interference signals in the repeater 30 . The repeater 60 includes a downlink or forward CICS circuitry block 62 and an uplink or reverse CICS circuitry block 64 . The CICS circuitry blocks 62 and 64 are not shown in any detail, but each includes a pilot signal generator and detector, which are utilized to detect the presence and amplitude of the respective interference signal and to inject a cancellation signal at the input of the respective duplexer filter 48 and 52 . The duplexer filters 48 and 52 and the CICS circuitry blocks 62 and 64 add undesired cost, group delay and complexity to the signal enhancement.

[0073] The conventional repeater 60 illustrated in FIG. 7 uses CICS circuitry blocks 62 and 64 to cancel all or a portion of unwanted feedback or coupled interference signals in the repeater 30 . In contrast, exemplary embodiments of the present invention, as described herein, do not use CICS circuitry or similar circuitry to combat or cancel unwanted feedback or coupled interference signals in a signal enhancer unit.

[0074] One of ordinary skill in the art will recognize that a duplexer filter and a diplexer filter are fundamentally the same type of filter having three ports. A duplexer or diplexer filter is a specific case of the more general multiplexing filters having a common port and having an operational pass band that encompasses two or more ports having operational pass bands that are subsets of the operational pass band of the common port. The terminology duplexer filter is conventionally used when the two ports corresponding to subset operational bands are specifically used for transmitting and receiving RF signals, respectively. The diplexer filter terminology can be used more generally for two band separated RF signals where both band separated RF signals are for receive or transmit purposes. The terminology duplexer filter can be equivalently used to describe a diplexer filter.

[0075] Referring to FIG. 8, a conventional adaptive cancellation repeater 70 is illustrated, such as described in PCT Publication No. WO 01/52447 A2. The repeater 70 includes a donor transmitting (Tx) and receiving (Rx) antenna 72 , which feeds the received downlink signal F 2 to a duplexer filter (D) 74 , which in turn couples the downlink signal F 2 to an adaptive cancellation circuit block (AC BLOCK) 76 . The AC BLOCK 76 generates a negative signal, which is combined with the signal F 2 to cancel the feedback signal or component from the signal F 2 . The signal F 2 is also amplified in the AC BLOCK 76 and then coupled to a filter (F) 78 , typically a band pass filter. The AC BLOCK 76 and the filter 78 form the active components in a downlink signal path 80 . The filter 78 protects the amplifier in the AC BLOCK 76 from the signal power on the uplink path. The filter 78 couples the signal F 2 to a duplexer filter (D) 82 , which in turn couples the signal F 2 to a second server transmitting (Tx) and receiving (Rx) antenna 84 . The antenna 84 transmits the amplified downlink signal F 2 to the user.

[0076] The user transmits a signal F 1 for transmission to the base station, which is received by the antenna 84 and coupled to the duplexer filter 82 , which in turn couples the signal F 1 to an adaptive cancellation circuit block (AC BLOCK) 86 in an uplink path 88 . The AC BLOCK 86 acts in the same manner as the AC BLOCK 76 . The filter 90 , typically a band pass filter, protects the amplifier in the AC BLOCK 86 from the signal power on the downlink path. The filter 90 couples the signal F 1 to the duplexer filter 74 , which in turn couples the signal F 1 to the donor transmitting (Tx) and receiving (Rx) antenna 72 . The antenna 72 transmits the amplified uplink signal F 1 to the base station.

[0077] The operation of the AC BLOCK 76 is illustrated in FIG. 9 . The downlink signal F 2 is combined at a summing junction 92 with a modulated signal constructed in the AC BLOCK 76 . The modulated signal is designed to destructively interfere with the feedback signal portion of the signal F 2 . The signal F 2 is digitally sampled and further processed by a digital signal processor (DSP) 94 . The DSP 94 computes an intermediate signal and couples it to a modulator (MOD) 96 . The MOD 96 also is input a sample of the signal F 2 after the signal has passed through a filter (F) 98 and has been amplified by an amplifier (A) 100 . The MOD 96 creates the destructive modulated signal from the two inputs and couples it to the junction 92 .

[0078] The operation of the AC BLOCK 86 is illustrated in FIG. 10 . Like the AC BLOCK 76 , the AC BLOCK 86 generates a modulated signal in a modulator (MOD) 102 designed to destructively interfere with the feedback signal portion of the signal F 1 . The modulated signal is combined in a summing junction 104 with the signal F 1 . The signal F 1 is digitally sampled and further processed by a digital signal processor (DSP) 106 . The DSP 106 computes an intermediate signal and couples it to the MOD 102 . The MOD 102 also is input a sample of the signal F 1 after the signal has passed through a filter (F) 108 and has been amplified by an amplifier (A) 110 . The MOD 102 creates the destructive modulated signal from the two inputs and couples it to the junction 104 .

[0079] The repeater 70 includes the AC BLOCKS 76 and 86 coupled between the output of the duplexer filters 74 and 82 , respectively, and the output of the amplifiers 98 and 108 . The repeater 60 injects the cancellation signal before the duplexer filters 48 and 52 , whereas the repeater 70 injects the adaptive cancellation signal after the duplexer filters 74 and 82 .

[0080] Referring now to FIG. 11 , another conventional adaptive cancellation repeater 120 , similar to the repeater 70 , is illustrated. The repeater 120 includes a separate donor transmitting (Tx) antenna 122 for transmitting the uplink signal F 1 to the base station and a separate donor receiving (Rx) antenna 124 for receiving the downlink signal F 2 from the base station. The repeater 120 also includes a separate server transmitting (Tx) antenna 126 for transmitting the downlink signal F 2 to the user and a separate server receiving (Rx) antenna 128 for receiving the uplink signal F 1 from the user. With the exception of an absence of duplexer filters, the repeater 120 is in all other respects identical to the repeater 70 .

[0081] The conventional repeater 120 illustrated in FIG. 11 comprises four (4) antennas and two (2) completely separate RF paths. The conventional repeater 120 uses separate antennas for transmitting and for receiving at the donor end of the system and separate antennas for transmitting and for receiving at the server end of the system. As described in more detail below, exemplary embodiments of the present invention typically comprise two (2) antennas. For example, an exemplary embodiment uses a single donor antenna and single server antenna and each antenna has two defined characteristic polarizations: one characteristic polarization for reception and one characteristic polarization for transmission of signals. Further, the characteristic polarization used for transmission of signals from the donor antenna is not the same as the characteristic polarization for reception of signals by the server antenna. Similarly, the characteristic polarization used for reception of signals by the donor antenna is not the same as the characteristic polarization for transmission of signals from the server antenna.

[0082] A flat panel module 130 of the repeater 70 is illustrated in FIG. 12 . The module 130 includes a housing 132 into which the electronics of the repeater 70 are mounted. The antennas 72 and 84 are placed in a back-to-back orientation within the module 130 , although the antenna 72 is shown on the outside of the housing 132 for illustration purposes. Like the repeater 60 , the duplexer filters 74 and 82 (in the repeater 70 ) and the AC BLOCKS 76 and 86 add undesired cost, group delay and complexity to the signal enhancement of the repeater 70 .

[0083] A similar flat panel module 140 of the repeater 120 is illustrated in FIG. 13 . The module 140 includes a housing 142 into which the electronics of the repeater 120 are mounted. The pairs of antennas 122 , 124 and 126 , 128 are placed in a back to back orientation within the module 140 , although the antennas 122 and 124 are shown on the outside of the housing 142 for illustration purposes. The antennas 122 and 124 are the donor antenna pair and antennas 126 and 128 are the server antenna pair. The donor transmit (Tx) antenna 122 and the donor receive (Rx) antenna 124 are arranged in a side by side configuration. Likewise the server transmit antenna 126 and server receive antenna 128 are arranged in a side by side configuration.

[0084] An illustration of the coverage area improved by signal enhancement supported by an exemplary embodiment of the present invention is illustrated in FIG. 14 . A base station tower 150 transmits a signal that a user would like to receive by using a subscriber unit inside of a building or structure 152 . The base station signal is too weak, for any one or more of the reasons previously enumerated, when received at the building 152 for the user to receive and use inside the building 152 with the desired quality of service. The signal is, however, still strong enough, at least on the order of about minus ninety (−90) to minus ninety-five (−95) dBm, to be received and enhanced by a signal enhancement unit 154 constructed in accordance with an exemplary embodiment of the present invention. The user can place the signal enhancement unit 154 , also described as a signal enhancer, on or adjacent a wall or window 156 of the building 152 . The user (not illustrated) can place the unit 154 adjacent an area of high RF transmission, such as a window (not illustrated), and then apply electric power to the unit 154 and observe if the signal can be received and amplified by the unit 154 for use inside the building 152 .

[0085] The same or another user also may desire coverage or improve the quality of service resulting from marginal coverage in a larger building 160 illustrated in FIG. 15 . The user in the building 160 also receives a signal from the tower 150 , which is initially too weak to be used or becomes too weak to be used in interior locations of the building 160 for the desired quality of service. In this situation, the user can again place an exemplary signal enhancer unit 162 adjacent a wall or window 164 to receive and enhance the signal from the base station tower 150 . The user can use the enhanced signal inside the building 160 for a distance that is typically dependent upon many factors about the signal and the environment. For example, the enhanced signal coverage area can cover an area on the order of two thousand (2,000) square feet up to about five thousand (5,000) square feet. After that distance is exceeded or the user proceeds into another room or area, however, the signal may need to be enhanced again. The user can place one or more other enhancer units 162 ′ throughout the building to obtain reliable signal coverage where desired. The units 162 ′ are typically the same as the unit 162 and are placed within range of the first or primary unit 162 or another one of the units 162 ′. The units 162 and 162 ′ can be considered cascaded or sequentially linked in operation. The units 162 and 162 ′ are illustrated as being parallel in orientation to one another; however, the units 162 and 162 ′ also can be placed at an angle to one another to widen or redirect the enhanced signal coverage obtained.

[0086] Referring to FIG. 16, a simplified block diagram of a signal enhancer 170 constructed in accordance with an exemplary embodiment of the present invention is illustrated. The exemplary signal enhancer 170 includes a first donor dual polarized antenna 172 having a first antenna characteristic polarization portion 174 , which can be implemented by a vertically polarized characteristic. The antenna portion 174 receives the downlink signal F 2 and couples it to a downlink signal path 176 . The signal F 2 is coupled to an amplifier 178 , which forms a first part of a bi-directional amplifier (BDA) and which amplifies the signal F 2 and couples the signal F 2 to a second server dual polarized antenna 180 . A first server antenna 180 having a characteristic polarization portion 182 is cross-polarized relative to the donor antenna characteristic polarization 174 and is horizontally polarized in this example. The antenna portion 180 can transmit the amplified downlink signal F 2 to the user. A person of ordinary skill in the art will know that a second polarization that is cross-polarized relative to a first characteristic polarization has an orthogonal polarization characteristic relative to the first characteristic polarization.

[0087] A second antenna characteristic polarization portion 184 of the server antenna 180 is cross-polarized relative to the first characteristic polarization portion 182 and is vertically polarized. The antenna portion 184 receives the uplink signal F 1 from the user and couples it to an uplink signal path 186 . The signal F 1 is coupled to an amplifier 188 , which forms the second part of the bi-directional amplifier (BDA), amplifies the signal F 1 and couples the amplified signal F 1 to a second antenna characteristic polarization portion 190 of the donor antenna 172 . The antenna portion 190 is cross-polarized to the first portion 174 and is horizontally polarized in this example. The antenna portion 190 transmits the amplified uplink signal F 1 to the base station.

[0088] The downlink receiving polarization 174 is vertically polarized, which is orthogonal to the horizontal polarization 182 for the downlink transmitting portion for the signal F 2 . In a like manner, the uplink path has a receiving vertically polarized antenna portion 184 , which is orthogonal to the horizontally polarized transmitting antenna portion 190 for the signal F 1 . The downlink receiving polarization 174 could be horizontally polarized, but preferably is vertically polarized, since a majority of base stations transmit with a vertical polarization. Consequently, a vertical polarized portion 174 will receive more power for a base station than if it was horizontally polarized. The orthogonal polarization between the downlink receiving antenna 174 and uplink transmitting antenna 190 can provide sufficient isolation such that the enhancer 170 does not require the duplexer filters required by the conventional art. Further, the isolation is sufficient to provide amplification without any type of signal transformation or feedback cancellation circuitry. The enhancer 170 thus provides a cost savings, a reduction in the noise figure and a reduction in the group delay of the enhancer 170 over conventional repeaters. The signal enhancer 170 is designed, as will be further described, such that a duplexer filter is not required by the antenna 172 , even though only one first donor antenna 172 is used for both receiving from and transmitting to the base station and only one second server antenna 180 is used for both receiving from and transmitting to the user. The exemplary enhancer 170 is designed without conventional duplexer filters and can have lower signal losses or attenuation prior to the low noise receive amplifiers 240 and 276 as compared to the conventional art. The noise figure of the exemplary enhancer 170 is typically less than 6 dB.

[0089] Mobile positioning is an important emerging requirement for mobile wireless phone systems. The Federal Communications Commission (FCC) of the USA adopted a ruling in June 1996 (Docket no. 94-102) that requires all mobile network operators to provide location information on all calls to “911”, the emergency services or so called E911 capability. Group delay is the rate of change of the total phase shift with respect to angular frequency through the device or the transit time required for RF power, traveling at a given mode's group velocity, to travel a given distance. The exemplary enhancer 170 provides a typical group delay value of less than 50 nanoseconds (ns). Some location schemes such as Enhanced Observed Time Difference (E-OTD) rely on accurate time measurements and excessive group delay can cause the E-OTD system some difficulty in accurately determining the point in the signal to be measured by all receivers.

[0090] FIG. 17 illustrates a flat panel enhancer unit 200 constructed in accordance with another exemplary embodiment of the present invention. The unit 200 includes a housing 201 , which contains the circuitry (not illustrated) of the enhancer unit 200 . The housing 201 has a top side or edge 202 , a pair of sides or side edges 203 and 204 and a bottom side or side edge 205 . The donor antenna 172 can include a symmetrical array of four (4) patches 206 , 207 , 208 and 209 , with each patch dual polarized (see FIG. 36 ) to provide the receive portion 174 and the transmit portion 190 orthogonal to one another. For example, the patch 206 includes a vertical orientation portion 210 and a horizontal orientation portion 211 . Each of the other patches 207 , 208 and 209 also has the same orientation portions (not separately numbered), which operate in the same manner. In a like manner, the server antenna 180 on the reverse or back side of the housing 201 can include a similar array of four (4) patches 212 , 213 , 214 and 215 , with each patch dual polarized to provide the receive portion 184 and the transmit portion 182 orthogonal to one another in the similar manner as the patch 206 .

[0091] The exemplary enhancer unit 200 uses antenna polarization isolation to reduce feedback signals between the server antenna 180 and the donor antenna 172 and to reduce signals between the transmit and receive functions on the server antenna 180 and on the donor antenna 172 . These feedback signals are coupled through radiation means between the server antenna 180 and the donor antenna 172 . The use of linear polarization orientations 210 and 211 that are perpendicular to and parallel to the sides or edges 202 , 203 , 204 , and 205 of the housing 201 can mitigate cross coupling between the opposite or orthogonal polarizations of the server antenna 180 and the donor antenna 172 . Linear polarizations 210 and 211 are principally perpendicular to and parallel to the conducting and dielectric boundaries of the sides or edges 202 , 203 , 204 , and 205 and can minimize the coupling between a first antenna characteristic polarization portion 174 antenna 172 and a first characteristic polarization portion 182 that is cross-polarized relative to the antenna portion 174 . In a like manner, linear polarizations 210 and 211 are principally perpendicular to and parallel to the conducting and dielectric boundaries of the sides or edges 202 , 203 , 204 , and 205 and can minimize the coupling between a second antenna characteristic polarization portion 190 and a second characteristic polarization portion 184 that is cross-polarized relative to the antenna portion 190 .

[0092] Linear polarizations 210 and 211 are principally perpendicular to and parallel to the conducting and dielectric boundaries of the sides or edges 202 , 203 , 204 , and 205 and can minimize the coupling between a first antenna characteristic polarization portion 174 and a second characteristic polarization portion 190 that is cross-polarized relative to the antenna portion 174 . In a like manner, linear polarizations 210 and 211 are principally perpendicular to and parallel to the boundaries of the sides or edges 202 , 203 , 204 , and 205 and can minimize the coupling between a first antenna characteristic polarization portion 182 and a second characteristic polarization portion 184 that is cross-polarized relative to the antenna portion 182 .

[0093] The boundaries of the sides or edges 202 , 203 , 204 , and 205 of the exemplary enhancer unit 200 comprise conducting and/or dielectric materials that are substantially the same length. The housing 201 of the enhancer unit 200 is substantially a square shape in the plan view of the donor antenna 172 or the server antenna 180 . The antenna array radiators 206 , 207 , 208 , and 209 can be arranged with equal spacing in the donor antenna 172 . In like manner, the antenna array radiators 212 , 213 , 214 , and 215 can be arranged with equal spacing in the server antenna 180 . The antenna array radiators 206 , 207 , 208 , and 209 in the donor antenna 172 can be arranged in a back-to-back configuration relative to the antenna array radiators 212 , 213 , 214 , and 215 of the server antenna 180 . For this configuration, the primary directions of radiation of the donor antenna 172 and the server antenna 180 are substantially in opposite directions.

[0094] The exemplary flat panel enhancer unit 200 , in contrast to the conventional flat panel modules 130 and 140 illustrated in FIG. 12 and 13 , respectively, uses an antenna array of radiators having dual simultaneous characteristic polarizations 210 and 211 for the purpose of separating and isolating the uplink and downlink signals into two (2) paths. Exemplary embodiments of the present invention can use a single donor antenna array and single server antenna array, where each antenna array has two defined characteristic polarizations: one characteristic polarization for reception and one characteristic polarization for transmission of signals. Further, the characteristic polarization used for transmission of signals from the donor antenna array is not the same as the characteristic polarization for reception of signals by the server antenna array. Similarly, the characteristic polarization used for reception of signals by the donor antenna array is not the same as the characteristic polarization for transmission of signals from the server antenna array. Each characteristic polarization in the donor or server antenna array is for the single purpose of receiving a signal or for the single purpose of transmitting a signal. In other words, a characteristic polarization of an exemplary embodiment does not have the dual purpose or function of transmitting and receiving a desired signal, as shown by the enhancer unit 200 .

[0095] The frequency spectrum 220 for the PCS band, used by way of an example for the operation of exemplary embodiments, is illustrated in FIG. 18 . The base station (BS) receives in a band 222 of 1850 to 1910 MHz and transmits in a band 224 of 1930 to 1990 MHz. Although a perfect transmit (Tx) band 224 and a perfect receive (Rx) band 222 would have a rectangular band shape (illustrated in dashed lines) existing only in the frequency band, there is some spread and overlap between the frequency response of signal enhancer filters defining the actual bands 222 and 224 performance characteristics. The actual frequency bands are illustrated by solid lines 225 and 226 for the band 222 and solid lines 227 and 228 for the band 224 . The ideal bands have 20 MHz of separation, between 1910 and 1930 MHz. One critical point, however, is a crossover point 229 where the two bands actually overlap. The crossover point 229 will be discussed in further detail with respect to the filtering of the signals in FIG. 19 . Each of the bands 222 and 224 is also subdivided into a plurality of sub-bands A, B, C, D, E and F that are individually licensed to service providers of a service area or zone within the US. An exemplary signal enhancer unit typically provides operational coverage across all of the sub-bands and can be viewed as a ‘full-band’ device.

[0096] A more detailed block diagram of an exemplary signal enhancer unit is illustrated in FIG. 19 and is designated generally by the reference numeral 230 . The exemplary unit 230 includes a dual polarized donor antenna 232 with a downlink vertically polarized receiving portion 234 , which couples the downlink signal F 2 to a downlink signal path 236 . The signal F 2 is coupled to a first filter 238 , which is designed to have a center pass frequency of 1960 MHz and to pass the receiving band F 2 signal in the receiving band of 1930 to 1990 MHz (the transmitting band of the base station), while filtering out unwanted frequencies outside the band.

[0097] The preselector filter 238 and other filters of the unit 230 can be implemented by so-called “ceramic” band pass filters. For an exemplary embodiment, a conventional ceramic band pass filter can be used, where the filter has three (3) poles and is customized with a zero located at or near the adjacent band edge of the other operational transmit or receive band. The poles and zeros of the filter transfer function define locations of singularities within the s-plane conventionally used in filter analysis and design and are used as a measure of the complexity of the filter. Such filters are designed around the center frequency of 1960 MHz to pass the receiving frequency band of 1930 to 1990 MHz or around the center frequency of 1880 MHz to pass the transmitting frequency band of 1850 to 1910 MHz for uplink signals to the base station (BS), which leaves a separation of 20 MHz between the signals as illustrated in FIG. 18 . However, as described, the bands 222 and 224 are not ideal, as shown with the dashed lines in FIG. 18 , and there is an actual crossover point 229 between the responses of the bands 222 and 224 .

[0098] The conventional three (3) pole ceramic preselector bandpass filters can be implemented by part number C031880E manufactured by Microwave Circuits, Inc. located in Wash. DC for the transmitting frequency band of 1850 to 1910 MHz. The conventional three (3) pole ceramic bandpass filters can be implemented by part number C031960J manufactured by Microwave Circuits, Inc. for the receiving frequency band of 1930 to 1990 MHz.

[0099] The conventional three (3) pole ceramic bandpass filters have a performance characteristic near the crossover point 229 of approximately minus three (−3) dB relative to the peak signal level in the pass band regions 222 and 224 . The slope and shaped of the conventional three (3) pole ceramic filter response outside the pass band regions 222 and 224 are primarily determined by the pass band width and the number of poles. The BS transmit (Tx) filter on the lower frequency side 227 has a measurable response within the pass band of the BS receive (Rx) filter pass band 222 . This response represents the degree of isolation or rejection between the BS transmit (Tx) and BS receive (Rx) bands. Similarly, the upper frequency side 226 of the BS receive (Rx) filter has a measurable response within the pass band of the BS transmit (Tx) filter pass band 224 . This response represents the degree of isolation or rejection between the BS receive (Rx) and BS transmit (Tx) bands.

[0100] By adding a zero in the filter transfer function at or near the adjacent band edge of the other operational transmit or receive band, the crossover value 229 can be reduced from approximately minus three (−3) dB of the conventional ceramic filter design to approximately minus ten (−10) dB and the degree of isolation or rejection between the BS transmit (Tx) and BS receive (Rx) bands can be increased. For example, a zero can be added at or near 1932 MHz of the BS receive (Rx) band pass filter having an operational band of 1850 to 1910 MHz and a zero can be added at or near 1908 MHz for a band pass filter having an operational band of 1930 to 1990 MHz. This filter design provides a crossover 229 rejection or isolation value that is minus ten (−10) dB relative to the operational pass band response. Locating the zero closer to the operational band can improve the rejection at the crossover 229 frequency of 1920 MHz but the pass band of the operational band can have greater attenuation and group delay.

[0101] The custom ceramic three (3) pole band pass filter with zero can be supplied by ComNav Engineering in Portland, Me., which specializes in custom filters for wireless communication systems. A custom ceramic three (3) pole band pass filter with zero for the BS receive (Rx) band is part number 3BCR6C-1880/Z75-LX and for the BS transmit (Tx) band is part number 3BCR6C-1960/Z75-LX.

[0102] An additional advantage of the design and use of the three (3) pole ceramic bandpass filter with zero, is that the filters are relatively inexpensive and physically small in size. This design eliminates the need for additional filters or more complex filters with additional poles, which minimizes the size and cost of the filters as well as minimizes the group delay. By reducing group delay, as shown in the exemplary enhancer unit 230 , the capability of finding a user in a timely fashion under Emergency 911 location requirements can be satisfied. A greater delay will result in a less accurate user location and hence can interfere with finding the user in an emergency. Exemplary embodiments of the enhancer unit 230 offer the attractive features of low-cost, the capability of portable use, and reduced group delay.

[0103] After filtering, the signal F 2 is coupled to a low-noise amplifier (LNA) 240 for a first amplification stage for the signal F 2 , without significantly increasing the signal to noise ratio of the signal. The amplified signal F 2 then is coupled to a second filter 242 , which can be identical to the filter 238 , for filtering the frequencies outside of the receiving band to more closely match the ideal receiving band. The filtered signal F 2 is coupled to a variable gain amplifier 244 , which controls the output power of the downlink signal F 2 . The variable gain amplifier 244 acts as a preamplifier if the gain is greater than or equal to unity, which is 0 dB or greater. The variable gain amplifier 244 can also act as an attenuator when the gain is less than unity or less than 0 dB. The use of a variable gain amplifier 244 as a control device for the signal amplitude control can provide a resolution control of the signal amplitude in one-half (0.5) and one (1.0) dB step sizes and provides uniform control of the signal amplitude that can be achieved without calibration of each signal enhancer 230 . The exemplary variable gain amplifier 244 has a dynamic range of approximately 50 dB covering the range of output signal values having a gain of approximately minus twenty-five (−25) dB to plus twenty-three (+23) dB.

[0104] The output signal of the variable gain amplifier 244 is further amplified by a power amplifier (PA) 246 . The output of the PA 246 is coupled through a conventional directional coupler 248 , which samples a small but amplitude proportional portion of the signal F 2 as a measure of the output power of the PA. The directional coupler 248 can be a DC17-73 manufactured by Skyworks Solutions, Inc. in Woburn Mass. and can have an insertion loss of less than one (1) dB with a coupled port at a value of approximately minus eleven (−11) dB. Following the coupler 248 , the output signal is coupled through a third and final filter 250 , which can be identical to the filter 238 .

[0105] The signal F 2 , after the final filtering, is coupled to a dual polarized server antenna 252 for transmission to a user from a horizontally polarized portion 254 of the antenna 252 . The retransmission to the user from the antenna portion 254 provides the maximum isolation from the receiving portion 234 of the antenna 232 , which is vertically polarized or orthogonal to the portion 254 .

[0106] The variable gain amplifier 244 is controlled by a microcontroller 256 , which samples the output power of the signal F 2 from the directional coupler 248 at predetermined periodic intervals. The microcontroller can be a PIC16F873 device made by Microchip Technology, Inc. of Chandler, Ariz. The functions of the microcontroller 256 also could be performed by a custom application specific integrated circuit (ASIC), a complex programmable logic device (CPLD), a system-on-a-chip (SOC) integrated circuit, a field programmable gate array (FPGA), or a similar device.

[0107] The directional coupler 248 provides a sample portion of the signal F 2 to a RF power detector 258 . An exemplary embodiment uses a RF logarithmic detector and controller AD8313 manufactured by Analog Devices, Inc. in Norwood, Mass. The use of a RF logarithmic detector provides a relatively wide dynamic range of signal amplitude detection and can provide accuracies of plus or minus three (±3) dB over a 70 dB dynamic range or plus or minus one (±1) dB over a 62 dB dynamic range. Lower cost devices, such as a diode detector, can be used but the accuracy and repeatability in the present application would require a calibration of each diode detector in an exemplary signal enhancer 230 . Calibration of individual signal enhancers 230 would add significant cost to the unit in a high volume manufacturing operation. It is desirable to avoid the need for calibrating any aspect of the exemplary unit 230 after assembly.

[0108] The output signal from the RF power detector 258 is coupled to the microcontroller 256 through a buffer stage 260 . The buffer stage provides a lower impedance output than the RF power detector output. The buffered output of the detected signal is coupled to an analog-to-digital converter (ADC) portion 262 in the microcontroller 256 . The microcontroller 256 compares the RF detected power level of the signal F 2 and compares it to a predetermined or initialization power level, as will be described hereinafter. During normal operation, the microcontroller 256 will compare the output power to a predetermined operating output level or a range thereof. The microcontroller 256 will send a signal to a digital-to-analog converter (DAC) portion 264 to adjust the output of the variable amplifier 244 and hence control the output power level of the signal F 2 . The DAC portion 264 can be a LTC 1661 Micropower Dual ten- (10-) bit DAC from Linear Technology Corporation of Milpitas, Calif. The LTC 1661 DAC provides two accurate addressable ten- (10-) bit DACs in a small package that have a high degree of linearity and so one device can provide the DAC portions 264 and 262 .

[0109] The use of a variable gain amplifier 244 having a sufficient linear dynamic range control, a digital-to-analog converter (DAC) portion 264 to adjust the output of the variable amplifier 244 with a sufficient number of bits and a desired resolution over the control range, and a RF logarithmic power detector 258 with commensurate accuracy enables the implementation of signal amplitude control that can function without an individual calibration for each exemplary unit 230 . A signal enhancer 230 that does not require calibration is important to achieving a low manufacturing cost.

[0110] The user sends a signal to be received by the antenna 252 , amplified and retransmitted to the base station by the antenna 232 in a manner similar to the downlink signal path 236 . A vertically polarized portion 270 of the antenna 252 receives the signal from the user. The uplink signal F 1 then is coupled to a first filter 272 on an uplink signal path 274 . The first filter 272 also is substantially identical to the filter 238 , except it is designed centered on 1880 MHz to filter the transmit band of 1850 to 1910 MHz. With the exception of the frequency band, each of the elements of the uplink F 1 signal path 274 is functionally identical to the corresponding element previously described with respect to the downlink signal F 2 path 236 . The filtered signal F 1 then is coupled to an LNA 276 and output to a second filter 278 . From the filter 278 , the signal F 1 is coupled to a variable gain amplifier 280 and output to a PA 282 . The signal F 1 then is coupled through a directional coupler 284 and a final filter 286 to a horizontally polarized portion 288 of the antenna 232 for transmission to the base station. As with the downlink signal F 1 , the output power level of the signal F 1 is sampled by the directional coupler 284 and fed to a RF power detector 290 . The RF power detector signal is coupled through a buffer 292 to an ADC portion 294 of the microcontroller 256 . The microcontroller 256 outputs an analog control signal through a DAC portion 296 to control the gain of the variable gain amplifier 280 and hence the output power level of the signal F 1 .

[0111] The desirable objectives of low-cost and portability for an exemplary signal enhancer support a need for an autonomous or automatic setup or initialization and monitoring routine. This automated setup routine is illustrated by a state diagram 300 in FIG. 20 and a timing and power diagram 302 illustrated in FIG. 21 . Upon the user applying power to a signal enhancer, such as the exemplary enhancer 230 , the microcontroller 256 compares the downlink signal F 2 power with a predetermined reference level or gain 304 (see FIG. 21 ) in an initial state (INIT State) 306 . If the sensed downlink power level of the signal F 2 is less (<) than the reference level 304 , then the microcontroller 256 increases the output power of both the downlink signal F 2 and the uplink signal F 1 . For example, the microcontroller 256 will increase the output power level at 1 dB per second, shown by a line 308 , until a power level 310 of minus ten (−10) dBm is reached that is also below the level 304 . The microcontroller 256 then will increase the output power level at 0.5 dB per second, shown by a line 312 , until the reference power level 304 of zero (0) dBm is reached. Alternatively, a maximum variable gain amplifier setting of +23 dB may be reached and the reference level 304 will be adjusted accordingly. At that operating or initialization reference level 304 , a lower level gain level 314 of five (5) dB less than the level 304 will be set. In other words, a lower level of a range of gain values to be set for maintaining the signal amplitude gain is minus five (−5) dB relative to the an upper level corresponding to the reference gain value.

[0112] The microcontroller 256 then will enter a MONITOR State 316 and a set of LED's or other visual indicating devices (see FIG. 25 ) will be set to indicate the status of the operating downlink power level 304 . In the monitor state 316 , the microcontroller 256 monitors the operation of the enhancer unit 230 for several conditions.

[0113] In a downlink EQUALIZE State 318 , the sampled downlink signal power F 2 is less than the reference gain 304 value and the gain valve of the variable gain amplifier 244 is less than the lower-window gain 314 value. The microcontroller 256 can increase both the uplink and the downlink gain until the F 2 signal power is within the window formed by the levels 304 and 314 or until the maximum allowable variable gain value or level is reached. The rate of signal gain increase is relatively slow, since the signal from the base station should be relatively consistent at a fixed distance.

[0114] In an uplink EQUALIZE State 320 , the sampled uplink signal power F 1 is less than the predetermined maximum uplink power level, for example plus twenty (+20) dBm, and less than the reference gain level 304 . The microcontroller 256 can increase the uplink signal power F 1 until either the predetermined maximum uplink gain level for the variable gain amplifier 244 or the reference gain level 304 is reached. In this case the rate of gain change is relatively fast since the user is free to move about in the building or other location, causing the uplink signal power level to fluctuate.

[0115] The use of downlink peak level and downlink overdrive level refer to a maximum signal amplitude value; both terms have the same meaning and the terms can be used interchangeably. Similarly, the use of uplink peak level and uplink overdrive level refer to a maximum signal amplitude value; both terms have the same meaning and the terms can be used interchangeably.

[0116] In a DOWNLINK OVERDRIVE State 322 , the sampled downlink signal power F 2 is greater than or equal to the predetermined monitoring level above the level 304 . The microcontroller 256 can decrease both the uplink and the downlink gain until the F 2 signal power is below the downlink overdrive reference monitoring level set at plus two (+2) dBm. In the State 322 , a visual indicator, such as a red LED, is flashed to indicate that the maximum downlink signal power 304 is exceeded. The enhancer unit 230 will return to the MONITOR State 316 when the F 2 signal power is again below the downlink overdrive reference monitoring power level of plus two (+2) dBm.

[0117] In an UPLINK OVERDRIVE State 324 , the sampled uplink signal power F 1 is greater than the uplink overdrive reference monitoring power level of plus twenty-one (+21) dBm. The microcontroller 256 can decrease the uplink gain only until the F 1 signal power is below the uplink overdrive reference monitoring power level. In the State 324 , a visual indicator, such as a red LED, is flashed to indicate that the maximum uplink signal power is exceeded. The enhancer unit 230 will return to the MONITOR State 316 when the F 1 signal power is again below the uplink overdrive reference monitoring power level.

[0118] An AUTO-OFF State 326 is reached when a predetermined timeout period expires with either or both of the downlink signal F 2 or the uplink signal F 1 being greater than the respective peak levels during the timeout period. Upon the expiration of a predetermined timeout period, for example, a time period of three hundred (300) seconds in duration, the microcontroller 256 can decrease both of the downlink and the uplink paths 236 and <