JP2943480B2 - Semiconductor phase shifter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor phase shifter, and more particularly to a semiconductor phase shifter having a wider band and a higher frequency.

[0002]

2. Description of the Related Art FIG. HOPFE
R, "Analog Phase Shifter f
or 8-18 GHz "MICROWAVE JOU
RNAL, March, 1979 PP. FIG. 48 is an equivalent circuit diagram showing an example of the configuration of the conventional semiconductor phase shifter shown at 48-50. In the figure, a varactor diode 4 having one end grounded is connected to each of a first output terminal 2 and a second output terminal 3 of the hybrid circuit 1. A bias is applied to the varactor diode 4 from the outside, but a bias circuit and the like for that purpose are not shown here.

Next, the operation will be described. The signal incident from the input terminal 5 is equally distributed and appears at the first output terminal 2 and the second output terminal 3, is reflected by the diode 4 and appears at the third output terminal 6. At this time, when the bias applied to the varactor diode 4 is changed, the impedance exhibited by the varactor diode 4 changes and functions as a variable impedance circuit. As a result, when the biases applied to the two varactor diodes 4 are simultaneously changed, the phase of the signal reflected from these varactor diodes 4 and appearing at the third output terminal 6 changes, so that the phase shifter can be operated. it can.

FIG. 17 is an equivalent circuit diagram for explaining the operation in more detail. The varactor diode 4 is used by applying a reverse bias. At this time, since the resistance component of the varactor diode 4 is sufficiently small, the varactor diode 4 can be equivalently represented by a capacitor. Thus, here, the varactor diode 4 when the applied bias is changed is represented by capacitors C1 and C2, respectively.

FIG. 18 shows reflection coefficients Γ1 and Γ2 exhibited by C1 and C2 when C1 and C2 are selected so as to realize a required phase shift amount Φ at the center frequency, where C1> C2. is there. The difference between the phase shift θ1 of Γ1 and the phase shift θ2 of Γ2 is Φ. Next, consider the frequency characteristics of # 1 and # 2.
First, a case where the frequency changes to a lower frequency side than the center frequency will be described. At low frequencies, the impedances presented by C1 and C2 both become high impedance and the phase advances. At this time, the change in θ1 is larger than the change in θ2,
Reflection coefficients Γ1L, に お い て 2 exhibited by C1 and C2 in the low frequency range
L is as shown in FIG. 19, and the phase shift amount ΦL is smaller than Φ. On the other hand, when the frequency changes to the higher frequency side from the center frequency, the impedances presented by C1 and C2 are both low impedance, and the change of θ1 is smaller than the change of θ2. The reflection coefficients Γ1h and Γ2h exhibited are as shown in FIG. Also in this case, the phase shift amount Φh is smaller than Φ. As a result, as shown in FIG. 20, the frequency characteristic of the amount of phase shift of this type of conventional phase shifter becomes a single-peak characteristic with a large change in the amount of phase shift within the band when the band is wide. In addition, since a unique semiconductor process is required to use a varactor diode as a semiconductor element, it cannot be formed integrally with an amplifier using an element having an amplifying function such as a field effect transistor, which is a factor preventing mass production. Had become.

[0006]

Since the conventional semiconductor phase shifter is configured as described above, the frequency characteristic of the phase shift amount becomes unimodal.
There is a problem that the phase shift amount sharply decreases near both ends of the low frequency range, and the phase shift amount error increases. Further, when a field-effect transistor that can be formed by the same process as an amplifier is used instead of a varactor diode to improve mass productivity, there is a problem that it is difficult to realize an appropriate capacitance as compared with a varactor diode. In addition, there is a problem that a small-sized field effect transistor having unnecessary small parasitic reactance suitable for high frequency cannot be used. Further, in the field effect transistor, there is a problem that a loss change is large because a resistance change accompanying an impedance change is large.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has been made to improve the mass productivity of semiconductor phase shifters.
It is another object of the present invention to increase the bandwidth of a semiconductor phase shifter using a field effect transistor to improve mass productivity. It is another object of the present invention to obtain a semiconductor phase shifter using a field effect transistor having good performance up to a high frequency.

[0008]

According to a first aspect of the present invention, there is provided a semiconductor phase shifter, wherein one end is connected to each of a first output terminal and a second output terminal of the hybrid circuit. A circuit in which a first capacitor and an inductor are connected in parallel so as to exhibit reactance, a second capacitor having one end connected to the other end of each of the circuits, and a drain connected to the other end of the second capacitor A grounded source field effect transistor, and bias means for applying a bias voltage to the base of the field effect transistor. By switching the bias voltage between 0 V and a pinch-off voltage, a resistor and a capacitor are provided between the drain and source. And a reflection phase variable circuit for setting a binary impedance by switching to the second capacitance. The field effect transistor to be sufficiently smaller than the impedance presented by the a is obtained by selecting the second capacitor. A semiconductor phase shifter according to a second aspect of the present invention includes a hybrid circuit, a second capacitor and a first resistor each having one end connected to a first output terminal and a second output terminal of the hybrid circuit. A grounded first field effect transistor having a drain connected to the other end of the second capacitor, a grounded source second field effect transistor having a drain connected to the other end of the first resistor, Bias means for applying a bias voltage to the bases of the first field-effect transistor and the second field-effect transistor, and by switching the bias voltage between 0 V and a pinch-off voltage, Reflection position that sets the binary impedance by switching between the drain and source of the field-effect transistor between a resistor and a capacitor And a variable circuit, wherein the first field-effect transistor and the second capacitor are selected such that the resistance of the first field-effect transistor is sufficiently smaller than the impedance of the second capacitor. The second field-effect transistor is selected for switching. A semiconductor phase shifter according to a third aspect of the present invention is the semiconductor phase shifter according to the first aspect,
The capacitor is connected between the drain and the source of the field effect transistor.

[0009]

According to the first aspect of the present invention, since the inductive reactance is loaded in series with the capacitive reactance at a high frequency, the change range of the reflection phase in principle can be reduced by 18%.
It can be expanded from 0 degrees to 360 degrees. As a result, a decrease in the amount of phase shift at a high frequency can be suppressed, and a wider band can be achieved. According to the second aspect of the present invention, in a state where the phase is relatively delayed, a resistor is loaded in parallel with the circuit of the second capacitor and the first field effect transistor of the reflection phase variable circuit. The impedance is reduced and the phase is further delayed. As a result, it is possible to suppress a decrease in the amount of phase shift at a low frequency where the influence of the resistance loading is large, and to achieve a wider band. Further, according to the third aspect of the invention, a small-sized field effect transistor having small unnecessary parasitic reactance can be used, so that good performance can be realized up to high frequencies.

[0010]

[Embodiment 1] FIG. 1 is a circuit diagram showing one embodiment of the present invention. A first output terminal 2 and a second output terminal 3 of a hybrid circuit 1 such as a coupled line hybrid are connected to an inductor 7 and a first capacitor 8 so as to exhibit inductive reactance.
Are connected in parallel. The drain of a first field-effect transistor 11 is further connected to the circuit 9 via a second capacitor 10. The source of the first field-effect transistor 11 is grounded, and the gate is configured to apply a bias via a bias circuit (not shown). Here, a circuit including the circuit 9, the second capacitor 10, and the first field-effect transistor 11 and loaded on the first output terminal 2 and the second output terminal 3 is a reflection phase variable circuit 12 Call.

Next, the operation will be described. 2 and 3 are equivalent circuit diagrams for explaining the operation of the semiconductor phase shifter whose circuit configuration is shown in FIG. By switching the bias voltage applied to the gate of the first field-effect transistor 11 between 0 V and the pinch-off voltage, it is possible to switch between the drain and source of the first field-effect transistor 11 between a resistor and a capacitor. The resistance and the capacitor are represented by Ra and Ca, respectively. Here, assuming that the magnitude of the resistor Ra is sufficiently smaller than the impedance exhibited by the second capacitor 10, this resistor can be neglected. Therefore, it can be considered that the second capacitor 10 is directly grounded. Therefore, when the applied bias is 0 V, the circuit 9 is loaded with the second capacitor 10. On the other hand, when the applied bias is the pinch-off voltage, the circuit 9 is loaded with the second capacitor 10 and the equivalent capacitor Ca provided by the first field-effect transistor 11 in series. As a result, the reflection phase variable circuit 12 loaded on the first output terminal 2 and the second output terminal 3 functions as a variable impedance circuit by changing the bias applied to the first field effect transistor 11. Thus, the phase of the phase shifter can be changed.

Next, the effect of the circuit 9 will be described. FIG. 4 shows the frequency characteristics of the reactance of the circuit 9 in which an inductor and a capacitor are connected in parallel by a solid line, and the frequency characteristics of the reactance of the inductor alone by a broken line. Fr in the figure
Is the resonance frequency of the circuit 9. By using the circuit 9, a large inductive reactance can be realized at a relatively high frequency near Fr without increasing the inductive reactance at a low frequency. Here, the capacity of the second capacitor 10 is made equal to the capacity of C1 shown in the conventional example, and the series capacity of the second capacitor 10 and the capacitor Ca is made the same as the capacity of C2 shown in the conventional example. When the second capacitor 10 and the first field effect transistor 11 are selected, the circuits shown in FIGS. 2 and 3 can be represented by the circuits shown in FIG. As an example, FIG. 6 shows the reflection coefficient of the reflection phase variable circuit 12 when the circuit constants are selected as described above. At the center frequency of the band, the inductive reactance loaded in series by the circuit 9 is small, so that the reflection coefficients Γ1 and Γ2 are almost the same as in the prior art. On the other hand, at high frequencies, a relatively large inductive reactance is C1,
It is loaded in series with the capacitive reactance exhibited by C2.
Here, the reflection coefficient と 1h in the state of loading C1 is made inductive, and the reflection coefficient Γ2h in the state of loading C2 is made capacitive, so that the inductor 7 and the first capacitor 8
FIG. 6 shows a case in which the values are selected. As a result of the phase change range of Γ1h being 180 degrees or more, a decrease in the phase shift amount is suppressed, and a phase shift amount similar to the center frequency is obtained even in a high frequency range. If the frequency is further increased, the reflection coefficient in both the C1 loading and the C2 loading becomes inductive, so that the phase shift amount decreases again, and the circuit 9
At the resonance frequency of, the first output terminal 2 and the second output terminal 3 are opened, and the phase shift amount becomes zero. Therefore,
The frequency characteristic of the phase shift amount of the phase shifter according to the present invention is bimodal as shown in the example of FIG.

Embodiment 2 FIG. FIG. 8 is a circuit diagram showing an embodiment of a semiconductor phase shifter having improved low-frequency characteristics according to the present invention. The drain of the first electric field transistor 11 is connected to the first output terminal 2 and the second output terminal 3 of the hybrid circuit 1 via the second capacitor 10. The source of the first field-effect transistor 11 is grounded, and the gate is configured to apply a bias via a bias circuit (not shown). The drain of a second field-effect transistor 14 is further connected to the first output terminal 2 and the second output terminal 3 of the hybrid circuit 1 via a first resistor 13 indicated by R1. Second field effect transistor 1
4 has a configuration in which a source is grounded and a gate is applied with a bias via a bias circuit (not shown). The second capacitor 10, the first resistor 13, the first field-effect transistor 11, and the second field-effect transistor 14 constitute a reflection phase variable circuit 12.

Next, the operation will be described. FIG. 9 is an equivalent circuit diagram for explaining the operation of the circuit configuration diagram shown in FIG. As described above, the first field-effect transistor 11 and the second field-effect transistor 14 are switched to a capacitor and a resistor according to the bias applied to the gate.
This resistance value is so small that the change in the phase shift amount can be ignored. Therefore, assuming that the second field effect transistor 14 connected in series to the first resistor 13 indicated by R1 has a small capacitance, the second field effect transistor 14 can be considered as an ideal switch. Therefore,
For example, assuming that the second capacitor 10 and the first field effect transistor 11 are the same as those in the description of FIG. 5, by switching the bias applied to the gate of the second field effect transistor 14, the first output terminal Reflection phase variable circuit 12 loaded on the second output terminal 3 and the second output terminal 3
Can be switched to a parallel circuit of the capacitor C1 and the resistor R1 and the capacitor C2.

Next, the effect of the first resistor 13 will be described. FIG. 10 shows the reflection coefficient of a circuit in which the resistor R1 is connected in parallel to the capacitor C1, together with the reflection coefficient of only the capacitor C1. In the drawing, Γ1L, Γ2L, and で 3L are reflection coefficients exhibited by C1, C2, and the parallel circuit of C1 and R1 in the low frequency range, respectively. Also, Γ1, Γ
2, and Γ3 are reflection coefficients exhibited by C1, C2, and the parallel circuit of C1 and R1 at the center frequency, respectively. In the low frequency range, the impedance exhibited by the capacitor C1 is relatively large, so that the reflection coefficient Γ3L of the circuit in which C1 and R1 are connected in parallel is greatly affected by R1, and the phase is delayed as compared with the case where only the capacitor C1 is used. As a result, the amount of phase shift increases as compared with the case without the resistor R1. On the other hand, at the center frequency, the impedance exhibited by the capacitor C1 becomes small, so that the impedance of the circuit in which C1 and R1 are connected in parallel is dominated by the impedance exhibited by the capacitor C1, and the influence of the resistor R1 becomes relatively small. As a result, the reflection coefficient Γ3 of the parallel circuit becomes Γ
1, and the change in the phase shift amount due to the resistor R1 is small. Furthermore, since the influence of the resistor R1 is further reduced in a high frequency range, the amount of phase shift is almost the same as when there is no resistor R1. Therefore, the phase shift amount characteristic of the phase shifter according to the present invention is such that the phase shift amount in the low frequency band becomes large as shown in FIG. it can.

Embodiment 3 FIG. In the first embodiment, the reflection phase variable circuit 12 includes the circuit 9,
The configuration in which the second capacitor 10 and the first field-effect transistor 11 are connected in series has been shown. However, the present invention is not limited to this, and as shown in FIG. 12, a configuration in which a third capacitor 15 is further connected in parallel with the first field-effect transistor 11 provides a degree of freedom in setting the capacitance of the first field-effect transistor 11. It is good also as composition which increases.

Embodiment 4 FIG. In the first embodiment, the configuration in which the second capacitor 10 and the first field-effect transistor 11 are connected in series has been described. However, the present invention is not limited to this. As shown in FIGS. 13 and 14, a fourth capacitor 16 can be further connected in parallel to use the small-sized first field-effect transistor 11 having a small unnecessary parasitic reactance. The configuration may be such that good performance can be realized up to high frequencies.

Embodiment 5 FIG. In the first embodiment, the reflection phase variable circuit 12 includes the second capacitor 10 and the first field-effect transistor 1.
1 is connected in series, but the present invention is not limited to this. As shown in FIG. 15, the first field-effect transistor 11 is further connected in parallel with a second resistor 17 as shown in FIG. The configuration may be such that the bias fluctuation applied to the gate of the field effect transistor 11 is changed to reduce the loss fluctuation when switching to the resistor and the capacitor.

The third, fourth, and fifth embodiments are described above.
In the above, an example of application to the semiconductor phase shifter having improved high-frequency characteristics shown in the first embodiment has been described. However, the present invention is not limited to this, and may be applied to the semiconductor phase shifter having improved low-frequency characteristics shown in the second embodiment. It goes without saying that it can be applied.

[0020]

As described above, according to the first aspect of the present invention,
A configuration in which inductive reactance is loaded in series with capacitive reactance, and the change range of the fundamental reflection phase has been expanded from 180 degrees to 360 degrees in the past, so that the amount of phase shift at high frequencies is suppressed. A semiconductor phase shifter using a field effect transistor having a wide band and good mass productivity can be obtained. According to the second aspect of the present invention, since the impedance is further reduced by lowering the impedance of the reflection phase variable circuit in the low frequency range by resistance loading, the decrease in the phase shift amount in the low frequency range is suppressed. A semiconductor phase shifter using a field effect transistor having a wide band and good mass productivity can be obtained. Furthermore, according to the third aspect of the present invention, since a small-sized field-effect transistor having small unnecessary parasitic reactance can be used, a wide-band and high-productivity field effect having good performance up to a high frequency is provided. A semiconductor phase shifter using a transistor can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of Embodiment 1 of the present invention.

FIG. 2 is an equivalent circuit diagram for explaining the operation of the first embodiment of the present invention.

FIG. 3 is an equivalent circuit diagram for explaining the operation of the first embodiment of the present invention.

FIG. 4 is a reactance characteristic diagram for explaining the operation of the first embodiment of the present invention.

FIG. 5 is an equivalent circuit diagram for explaining the operation of the first embodiment of the present invention.

FIG. 6 is a characteristic diagram illustrating a reflection coefficient of the reflection phase variable circuit according to the first embodiment of the present invention.

FIG. 7 is a characteristic diagram showing a phase shift amount according to the first embodiment of the present invention.

FIG. 8 is a circuit configuration diagram of Embodiment 2 of the present invention.

FIG. 9 is an equivalent circuit diagram for explaining the operation of the second embodiment of the present invention.

FIG. 10 is a characteristic diagram for illustrating an effect of a loading resistance according to the second embodiment of the present invention.

FIG. 11 is a characteristic diagram showing a phase shift amount according to the second embodiment of the present invention.

FIG. 12 is a circuit configuration diagram of Embodiment 3 of the present invention.

FIG. 13 is a circuit configuration diagram of Embodiment 4 of the present invention.

FIG. 14 is a circuit diagram showing the application of the fourth embodiment of the present invention to the third embodiment.

FIG. 15 is a circuit configuration diagram of Embodiment 5 of the present invention.

FIG. 16 is a circuit configuration diagram of a conventional semiconductor phase shifter.

FIG. 17 is an equivalent circuit diagram for explaining the operation of a conventional semiconductor phase shifter.

FIG. 18 is a characteristic diagram for explaining the operation of a conventional semiconductor phase shifter.

FIG. 19 is a characteristic diagram for explaining the operation of a conventional semiconductor phase shifter.

FIG. 20 is a characteristic diagram showing a phase shift amount of a conventional semiconductor phase shifter.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 hybrid circuit 2 first output terminal 3 second output terminal 4 varactor diode 5 input terminal 6 third output terminal 7 inductor 8 first capacitor 9 circuit 10 second capacitor 11 first field effect transistor 12 reflection Phase variable circuit 13 First resistor 14 Second field effect transistor 15 Third capacitor 16 Fourth capacitor 17 Second resistor

Continuation of the front page (72) Inventor Shuji Urasaki 5-1-1, Ofuna, Kamakura City Mitsubishi Electric Corporation Electronic Systems Laboratory (56) References JP-A-54-124655 (JP, A) 70341 (JP, U) Japanese Utility Model 1-110501 (JP, U) Japanese Utility Model 2-60319 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01P 1/185 H03H 7 / 20

Claims (3)

(57) [Claims] A hybrid circuit and a first capacitor and an inductor having one ends connected to a first output terminal and a second output terminal of the hybrid circuit, respectively, so as to exhibit inductive reactance. second calibration of circuits formed by the parallel connection, one end to the other end of the respective circuits being connected
Pasta, drain connected to the other end of the second capacitor
Grounded source field effect transistor
A bias for applying a bias voltage to the base of the transistor
With bias means and pinch off the bias voltage to 0V
By switching to the voltage, the drain-source
Switch to resistance and capacitor
And a variable reflection phase circuit for setting the resistance.
Compared to the impedance exhibited by the second capacitor.
The field effect transistor and the second
A semiconductor phase shifter characterized by selecting a capacitor . 2. A hybrid circuit, a second capacitor having one end connected to a first output terminal and a first resistor connected to a first output terminal of the hybrid circuit, and
Source connected with the drain connected to the other end of the capacitor
A first field-effect transistor of the other end of the first resistor
Grounded second field-effect transistor with drain connected to
A transistor, the first field-effect transistor and the second
Apply bias voltage to the base of the second field-effect transistor
And a bias means for applying the bias voltage to 0V.
By switching to the pinch-off voltage,
Field effect transistor and second field effect transistor
Switch between resistance and capacitor between drain and source
Reflection phase variable circuit to set binary impedance by
Comprising the above-mentioned first field-effect transistor
The resistance is equal to the impedance of the second capacitor.
The first field-effect transformer
Select the resistor and the second capacitor, and
A semiconductor phase shifter, wherein a field effect transistor is selected for switching . 3. The semiconductor phase shifter according to claim 1, wherein
A semiconductor phase shifter comprising a capacitor connected between a drain and a source of a field effect transistor.