Maeda, Minoru (Hachioji, JA)
Ikushima, Ichiro (Kokubunji, JA)

05/372937

09/17/1974

06/25/1973

Download PDF 3836874       PDF help

Click for automatic bibliography generation

Hitachi, Ltd. (Tokyo, JA)

333/1.100

333/238

H01P1/387; H01P1/32; H01P1/32

333/1.1

Gensler, Paul L.

Craig & Antonelli

What we claim is

1. In a lumped element circulator including:

2. An improved circulator as defined in claim 1, wherein said first reactance element is composed of a second capacitive element, and said second reactance element is composed of a first inductive element.

3. An improved circulator as defined in claim 2, wherein said second capacitive element is a beam lead type capacitor.

4. The circulator as defined in claim 2, wherein said first inductive element is composed of a coiled wire.

5. An improved circulator as defined in claim 2, wherein a second inductive element and a third capacitive element are connected in series with said second capacitive element.

6. An improved circulator as defined in claim 1, wherein said first reactance element is composed of a first inductive element, and said second reactance element is composed of a second capacitive element.

7. An improved circulator as defined in claim 6, wherein said first inductive element is composed of a spiral inductor.

8. An improved circulator as defined in claim 6, wherein said first inductive element is composed of a coiled wire.

9. An improved circulator as defined in claim 6, wherein said second capacitive element is composed of a beam lead capacitor.

10. An improved circulator as defined in claim 6, wherein said first inductive element is composed of a narrow part formed at said input end of said each line conductor.

11. An improved circulator as defined in claim 6, further comprising a third capacitive element connected between the end of said first inductive element opposite its connection with the end of a respective line conductor and said conductor plate.

12. An improved circulator as defined in claim 11, wherein said third capacitive element comprises a beam lead capacitor.

13. An improved circulator as defined in claim 12, wherein said first inductive element is composed of a narrow part formed at said input end of said each line conductor.

14. An improved circulator as defined in claim 13, wherein said second capacitive element includes a dielectric substance layer interposed between said conductor plate and said outer conductor.

15. In a lumped element circulator including:

16. In a lumped element circulator including:

BACKGROUND OF THE INVENTION

The present invention relates to lumped element circulators and, more particularly, to a lumped element circulator which compensates for parasitic reactances.

DESCRIPTION OF THE PRIOR ART

Lumped element circulators have hitherto been constructed on the basis of a structure as shown, by way of example, in FIG. 1. On the surface of a ferrimagnetic substrate 31, three line conductors 11-11', 12-12' and 13-13' are formed. The respective line conductors are separated into two parallel conductor lines 21 and 22, 23 and 24, and 25 and 26, and define cross angles of 120° with respect to one another. In order to provide electrical insulation a technique such as deposition and electroplating is employed in the formation of the line conductors. The three line conductors are connected at the terminating end parts 11', 12' and 13' to a conductor plate which is provided on the back of the ferrimagmetic substrate. A DC magnetic field is applied perpendicularly to the plane of the ferrimagnetic substrate 31. Then, an equivalent circuit with the substrate side viewed from the input terminals 11, 12, and 13 is as shown in FIG. 2 and includes nonreciprocal inductive elements 41, 42 and 43. A prior-art lumped element circulator is constructed, as shown by its equivalent circuit in FIG. 3, with suitable capacitive elements 44, 45 and 46 connected between the respective input terminals and an outer conductor. The nonreciprocal inductive elements 41, 42 and 43 shown in FIG. 2, however, generally contain not only components contributing to the nonreciprocal operation of the circulator, but also components functioning as mere reciprocal elements. The latter components manifest themselves in the form of parasitic reactance components. As a consequence, the circuit arrangement shown in FIG. 3 is disadvantageous in that the reciprocal components cannot be compensated and sufficiently good circulator characteristics cannot be attained.

Further, it is often the case that the static coupling capacitance between the line conductors at the crossing parts and the series inductance attributable to the line conductor at each input terminal part cannot be neglected. For this reason, the circuit arrangement shown in FIG. 3 has the disadvantage that parasitic reactance components due to the coupling capacitance and the series inductance cannot be compensated, which leads to unsatisfactory circulator characteristics.

SUMMARY OF THE INVENTION

An object of the present invention is to eliminate the disadvantages of the prior-art lumped element circulator, and to provide a lumped element circulator which compensates for parasitic reactances.

In order to accomplish the object, the present invention compensates reciprocal components contained in nonreciprocal inductive elements which conduct the circulator operation.

Also, in order to accomplish the object the present invention compensates the series inductance existing at each input part of a line conductor or the electrostatic coupling capacitance between the line conductors.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view showing an example of construction of line conductors in lumped element circulators having hitherto been used;

FIG. 2 is an equivalent circuit diagram of the lumped element circuit as shown in FIG. 1;

FIG. 3 is an equivalent circuit diagram of a prior-art lumped element circulator;

FIG. 4 is an equivalent circuit diagram of an embodiment of the circulator according to the present invention;

FIGS. 5a and 5b are views of the embodiment realizing the equivalent circuit in FIG. 4;

FIGS. 6 and 7 are equivalent circuit diagrams of further embodiments of the present invention;

FIGS. 8a and 8b are equivalent circuit diagrams of intrinsic impedances with parasitic reactance components taken into consideration;

FIG. 9 is an equivalent circuit diagram of still a further embodiment of the circulator according to the present invention;

FIG. 10 illustrates an example of calculation of a frequency band characteristic;

FIG. 11 is a view showing the embodiment of the equivalent circuit in FIG. 9;

FIG. 12 is a view of an embodiment, showing the construction of an grounded capacitive element which constitutes the circulator according to the present invention;

FIG. 13 is a view showing an embodiment of an essential portion of the lumped element circulator according to the present invention, the portion employing a spiral inductance; and

FIG. 14 is a view showing another embodiment of the essential portion of the lumped element circulator according to the present invention, the portion employing a beam lead capacitor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As previously stated, in the lumped element circulator, there exists the parasitic reactance component due to the reciprocal reactances of the parasitic reactance component due to the reactance present at the input end of each line conductor and the reactance between the line conductors. Therefore, the reciprocal reactances contained in nonreciprocal inductive elements for effecting the circulator operation will be first explained with reference to equivalent circuits of the lumped element circulator.

The eigen-impedances of the structure in FIG. 1 for in-phase, positive-rotating and negative-rotating excitations are set at Z ₀ , Z ₁ and Z ₂ , respectively. The RF magnetic field within the ferrimagnetic substrate becomes almost zero for in-phase excitation, so that Z ₀ = 0. In the case of positive-rotating or negative-rotating excitation, positive and negative circular rotating fields are generated within the ferrimagnetic substrate and in a plane orthogonally intersecting with the DC magnetic field. The respective effects can be expressed by the impedances of (jωμ + Ln), and (jωμ - Ln). These are components which contribute to the nonreciprocal operation of the circulator.

In contrast, that component of the RF magnetic field which is parallel to the DC magnetic field does not contribute to the nonreciprocal effect, but it acts as a mere reciprocal component. It becomes the parasitic reactance component. Although the influence of the reciprocal component is small in case where the line conductors are fully embedded in the ferrimagnetic substrate it is not negligible in case where the line conductors are exposed to the air as shown by way of example in FIG. 1. Letting j ω Lr be the impedance of the reciprocal component, Z ₁ and Z ₂ can be expressed as follows:

Z ₁ = jωLr + jωμ + Ln (1)

Z ₂ = jωLr + jωμ - Ln (2)

Here, μ+ and μ- have the following relation with the component of the tensor permeability of the magnetic substance:

μ ₊ = μ + k (3)

μ _- = μ - k (4)

The impedance matrix (Z) of the rotationally symmetrical circulator is generally given by the following equation: ##SPC1##

The voltages V ₁ , V ₂ and V ₃ and currents I ₁ , I ₂ and I ₃ of the respective input terminals shown in FIG. 2, the impedance matrix has the following relation: ##SPC2##

On the other hand, the following relations hold between the elements Z ₁₁ , Z ₁₂ and Z ₂₁ of the impedance matrix (Z) and the intrinsic impedances Z ₀ , Z ₁ and Z ₂ :

Z ₁₁ = 1/3 (Z ₀ + Z ₁ + Z ₂ ) (7)

z ₁₂ = 1/3 (z ₀ + α ² z ₁ + α z ₂ ) (8)

z ₂₁ = 1/3 (z ₀ + α z ₁ + α ² z ₂ ) (9)

where

α = exp (- 2/3 π).

Substituting Z ₀ = 0 and Equations (1) and (2) into Equations (7), (8) and (9) we obtain:

Z ₁₁ = j 2/3 ωLr + j 1/3 ω(μ ₊ + μ _- )Ln (10)

Z ₁₂ = -j 1/3 ωLr + j 1/3 ω(α ² μ ₊ + αμ _- )Ln (11)

Z ₂₁ = -j 1/3 ωLr + j 1/3 ω(αμ ₊ + α ² μ _- )Ln (12)

Accordingly, using Equations (3) and (4), the impedance matrix (Z) reduces to: ##SPC3##

In Equation (13), the first term of the right-hand side is the reciprocal component, and the second term is the component contributive to the nonreciprocal operation of the circulator. Where the reciprocal component is negligible, that is, where Lr = 0, the impedance matrix (Z) is expressed by only the second term of the right-hand side of Equation (13). Then, the circulator can be constructed by connecting a capacitive element of appropriate value in parallel with each input terminal. Accordingly, it suffices that the first term in Equation (13) can be corrected. Now an inductive element (having an inductance Ls) is connected between the conductor plate on the back of the ferrimagnetic substrate and the outer conductor. Then, since all the currents flowing into the respective terminals pass through the element, the effect is equivalent to adding the following to the impedance matrix (Z) given by Equation (13): ##SPC4##

Accordingly, if the value of the element is selected so that Ls = 1/3 Lr, the sum between the above-mentioned term and the first term of Equation (13) becomes: ##SPC5##

That is, only the component of non-diagonal parts of the impedance matrix leading to the reciprocal component is corrected.

The remaining parts in Equation (14) depend only on the currents flowing through the respective terminals. Therefore, in order to correct them, capacitive elements (having a capacitance of Cs) are connected in series with the respective input terminals. Then, the effect is equivalent to adding the following to Equation (14): ##SPC6##

If the value of the elements is selected so that ωCs = 1/ωLr, (Zr) = 0. That is to say, the reciprocal reactance component indicated by the first term of Equation (13) can be corrected by connecting the capacitive elements in series with the respective input terminals and the inductive element between the conductor plate on the back of the ferrimagnetic substrate and the outer conductor.

Thus, the lumped element circulator according to the present invention takes the form shown in FIG. 4, when it is shown as an equivalent circuit. As seen in the figure, capacitive elements 51, 52 and 53 are connected to the respective input terminals, while an inductive element 54 is incorporated between the conductor plate and the outer conductor.

In FIG. 4, numerals 55-57 designate capacitive elements respectively corresponding to those 44-46 shown in FIG. 3.

As apparent from such an equivalent circuit, the lumped element circulator according to the present invention can, of course, be realized by employing, for example, known beam lead type capacitors as the capacitive elements and employing a coil as the inductive element and by connecting them in a conventional manner.

FIGS. 5a and 5b show an embodiment of the lumped element circulator which has been realized in such a way. As illustrated in FIG. 5a, beam lead type capacitors 51', 52' and 53' are connected to the circulator in FIG. 1 by thermally bonding each capacitor on both sides of a groove formed at each input end. As in the sectional view of FIG. 5b, a coiled wire 54' is connected between a conductor plate 58 on the back of the ferrimagnetic substrate 31 and the outer conductor (ground in the figure).

As described above, in accordance with the present invention, the parasitic reactances not contributing to the nonreciprocal operation in the circulator of the lumped element substrate can be perfectly compensated.

The circulator can be rendered to have a wide band width in such a way that, as shown in FIG. 6, a series resonance circuit consisting of a capacitive element 61 and an inductive element 62 is connected to each input terminal of the lumped element circulator illustrated in FIG. 4.

An alternative measure is illustrated in FIG. 7. Herein, the capacitive elements 55, 56 and 57 connected to the respective input terminals and the inductive element 54 connected to the conductor plate on the back of the ferrimagnetic substrate are mutually connected and a series resonance circuit consisting of a capacitive element 71 and an inductive element 72 is connected between the common connection point and the outer conductor.

Similarly, to the case of FIGS. 5a and 5b, the circulators of the equivalent circuits in FIGS. 6 and 7 can respectively be realized.

As described above, the parasitic reactance caused by the inductive component acting as the mere reciprocal reactance can be compensated. Description will now be made of the case of respectively compensating the parasitic reactance due to the electrostatic coupling capacitance at the crossing parts between the line conductors and the parasitic reactance due to the series inductance present at the input end of each line conductor.

The intrinsic impedances of the lumped element circulator shown in FIG. 1 and for the rotating excitation and the in-phase excitation are as shown by equivalent circuits in FIGS. 8a and 8b, respectively. In the figures, L _o at 64 is the series parasitic inductance at the input terminal part, while C _s at 65 is the parasitic capacitance attributable to the static coupling capacitance between the conductors. X ₊ and X _- at 63 are inductive reactances coupled between the conductor lines in the intrinsic impedances for the positive- and negative-rotating excitations, respectively. As is well known, in order to construct a circulator operating at a low magnetic field, intrinsic admittances Y _o , Y ₊ and Y _- for the in-phase, positive-rotating and negative-rotating excitations need satisfy the following conditions:

Y ₀ = ∞ (15)

y ₊ = -j 1/√3 Z _c (16)

Y _- = j 1/√3 Z _c (17)

where Z _c denotes the load resistance of the circulator. Equations (15)-(17) give the conditions concerning the circulator of the low magnetic field operation. In case of the high magnetic field operation, the suffixes of Y ₊ - may be replaced. Accordingly, the following explanation will be made in the case of the low magnetic field operation only.

FIG. 9 is an equivalent circuit diagram showing a further embodiment of the lumped element circulator according to the present invention. At each input end port, a correcting inductive element L _t is added to the parasitic inductance L _o (the combined inductances are shown at 66 in the figure). A capacitive element 67 (having a capacitance C _t ) is added between an end of the inductances closer to the input end and the conductor plate on the back of the ferrimagnetic substrate. Further, a capacitive element 68 (having a capacitance C _o ) is added between the conductor plate and the grounded conductor. Using the equivalent circuit in FIG. 9, the intrinsic admittances for the in-phase, positive-rotating and negative-rotating excitations are evaluated as follows: ##SPC7##

Here ω denotes angular frequency. By substituting them into Equations (15) - (17), there will be evaluated C _t , C _o and L _t fulfilling the circulator conditions: ##SPC8## ##SPC9##

Herein, in order that the circuit can be realized, it is required that L _o + L _t > 0, that C _t > 0 and that C _o > 0. When conditions for the requirements are evaluated from Equations (21) - (23), the following is obtained: ##SPC10##

That is, in case where the inductive reactances at the rotating excitations as coupled between the line conductors meet Equation (24) and where the parasitic capacitance C _s caused by the electrostatic coupling between the line conductors meet Equation (25), the circulator can be constructed by adding L _t , C _t and C _o given by Equations (21)-(23) as illustrated in FIG. 9.

FIG. 10 illustrates an example of calculation of the reverse direction loss of the lumped element circulator according to the present invention. In the calculation,

X ₊ = ωL ₁ + ω(μ + k) L ₂ (26)

x _- = ωl ₁ + ω(μ - k) L ₂ (27)

k _f = L ₂ /L ₁ + L ₂ (28)

here, μ and k denote the diagonal and non-diagonal parts of the tensor permeability, respectively. L ₁ and L ₂ indicate inductances which are determined by the geometries of the ferrimagnetic substrate and the line conductors.

By way of example, FIG. 10 illustrates a case where L ₁ + L ₂ = 2.5 nH, C _s = 3.0 pF, the saturation magnetization M _s = 400 Gauss, the internal DC magnetic field H _in = 300 0e, and the nonreciprocal filling factor k _f = 0.5. The band characteristic varies in dependence on the value of (L ₁ + L ₂ ) and the value of C _s . The wide band characteristic shown in FIG. 10 is obtained by appropriately setting these values.

The lumped element circulator according to the present invention as depicted by the equivalent circuit in FIG. 9 can be realized as below. As the inductive element to be added to the input end of each line conductor, a narrow part whose length is shorter than a predetermined wavelength (for example, for a wavelength λ, the narrow part is desirably shorter than approximately λ/10) is formed at the input end of each line conductor as is illustrated in FIG. 11. In the embodiment shown in FIG. 11, the line conductors are changed in shape as shown at 81, 81' and 81", to construct the narrow parts at the input ends. As the capacitive elements 67, the known beam read type capacitors, for example, are connected as shown at 82, 82' and 82". The capacitive element to be added between the conductor plate on the back of the substrate and the grounded conductor can be realized in such way that, as depicted in a sectional view of the circulator in FIG. 12, a dielectric substance layer 60 is interposed between the conductor plate 58 and the grounded conductor 59.

Further, a known spiral inductor, coiled wire or the like may be employed as the inductive element to be added to each input end, while the conventional read beam capacitor may be employed as the capacitive element 68.

FIG. 13 illustrates the case where the spiral inductor is connected to the input end of each line conductor. In the figure, the spiral inductor 97 is shown only for the conductor 11. The line conductors, to which the spiral inductors are connected in the illustrated manner, are arranged as shown in FIG. 1 and form the lumped element circulator.

FIG. 14 is a sectional view of the lumped element circulator in the case where the beam lead capacitor is used as the capacitive element for the connection between the conductor plate on the back of the substrate and the grounded conductor. In the figure, 98 indicates the beam lead capacitor which is connected between the conductor plate 58 on the back and ground.