JPH0831772B2 - Phase synthesis / branch circuit - Google Patents

Description

TECHNICAL FIELD The present invention relates to a phase combining / branching circuit for combining two signals with a constant phase difference or branching one signal with a constant phase difference, and particularly to a high frequency It is intended to improve the characteristics.

"Prior Art" Fig. 7 shows a conventional 90-degree phase branch circuit. This was proposed in Japanese Patent Application No. 61-163676. The input signals from the input terminal 11 are supplied to the first and second phase shifters 12 and 13, respectively, and the output terminals 14 and 13 of the first and second phase shifters 12 and 13 are respectively supplied.
A signal with a phase difference of 15 to 90 degrees is branched and output. In the first and second phase shifters 12 and 13, the collectors of the transistors Q ₁ and Q ₂ are connected to the positive side of the power source 18 through resistors 16 and 17, respectively, and are grounded in an alternating current manner, and the emitters are respectively It is connected to the negative side of the power supply 18 through resistors 19 and 21 and is grounded in an alternating current manner. Each base is connected to the input terminal 11 and the power supply 1 is connected through the bias resistors 22 and 23, respectively.
It is connected to the positive side of 8, and is further grounded through biasing resistors 24 and 25, respectively. A series circuit of the resistance element 26 and the capacitance element 27 is connected between the collector and the emitter of the transistor Q ₁ , and the connection point of the resistance element 26 and the capacitance element 27 is connected to the output terminal 14. A series circuit of the resistance element 28 and the capacitance element 29 is connected between the collector and the emitter of the transistor Q ₂ , and the connection point of the resistance element 28 and the capacitance element 29 is the output terminal.
Connected to 15.

Set the resistances of resistors 16, 19, 17, and 21 to R ₇ , R ₈ , and
The resistance values of R ₉ and R ₁₀ and the resistance elements 26 and 28 are set to R ₁ , R ₂ , and
Let C ₁ and C ₂ be the capacitances of the capacitive elements 27 and 29, respectively, and let the angular frequency of the input signal at the input terminal 11 be ω, and let R ₇ = R ₈ and R ₉ = R ₁₀
, The phase of each output signal from output terminals 14 and 15 is Θ ₁ and Θ
₂ is expressed by the following equation.

Θ ₁ = 2tan ^-1 (1 / ωR ₁ C ₁ ) (1) Θ ₂ = 2tan ^-1 (1 / ωR ₂ C ₂ ) (2) Fig. 8 shows the phase-frequency of the output signal expressed by the above equation. It shows the characteristics, the difference between Θ ₁ and Θ ₂ in the operating frequency band
If R ₁ , C ₁ and R ₂ , C ₂ are set to be 90 degrees,
A 90 degree phase difference can be obtained over a very wide band. Ninth
The figure shows the frequency characteristic of the phase difference between both outputs of the output terminals 14 and 15 at this time.

"Problem to be solved by the invention" However, in the circuit having the conventional configuration shown in FIG. 7, the amplitude (frequency between the collector and the substrate) associated with the collectors of the transistors Q ₁ and Q ₂ causes the amplitude frequency in the high frequency band. There is a drawback that the characteristics deteriorate. FIG. 10 shows the basic circuit section of FIG. 7, including transistor Q ₁ and resistors 16, 19, 22, 24.
This is an example in which the insertion loss on the collector side of the single-ended amplifier consisting of (in the case of R7 = R8) was obtained by simulation calculation with the collector-substrate capacitance C _SUB of the transistor Q ₁ as a parameter. As the collector-substrate capacitance C _SUB increases, the amplitude frequency characteristic on the collector side deteriorates, and it can be seen that the collector-substrate capacitance C _SUB affects the frequency characteristic.

An object of the present invention is to provide a phase synthesizing / branching circuit that suppresses the above-described deterioration of frequency characteristics in the high frequency band and has a wide band in the high frequency band.

"Means for Solving the Problem" The present invention relates to the above-described phase-combining branch circuit between the collector and the emitter of at least one of the first and second phase shift circuits, or between the drain and the source of the FET. Is connected to the second capacitor element, and the capacitance between the collector or drain and the substrate is compensated for by the negative phase signal on the emitter or source side, thereby suppressing deterioration of frequency characteristics in the high frequency band.

[Embodiment] FIG. 1 shows an embodiment of the present invention, in which parts corresponding to those in FIG. 7 are designated by the same reference numerals. In this embodiment, second capacitive elements 31 and 32 are connected between the collectors and emitters of the transistors Q ₁ and Q ₂ , respectively. If R ₇ = R ₈ and R ₉ = R _{10 in} this circuit, signals of equal amplitude and opposite phase are extracted from the collectors and emitters of the transistors Q ₁ and Q ₂ , respectively. Therefore, the collector-substrate capacitance C _SUB of the transistors Q ₁ and Q ₂ can be compensated by the second capacitance elements 31 and 32, and thus the deterioration of the amplitude frequency characteristic in the high frequency band can be suppressed.

2 and 3 show the improvement effect of the frequency characteristic by the capacitance compensation, which is actually clarified by the simulation calculation. In FIG. 2, before the amplitude frequency characteristic of the output terminal 14 is compensated by the capacitive element 31. Fig. 3 shows before and after compensating the amplitude frequency characteristic of the output terminal 15 with the capacitive element 32, and Fig. 4 shows the phase difference between both outputs of the output terminals 14 and 15 in the same manner. 2 shows before and after compensation by the capacitive element. Center frequency of design is 500MHz
Is. From FIGS. 2 and 3, it can be seen that the output amplitude frequency characteristic is improved in the high frequency band by compensating with the second capacitive element. The improvement effect is larger in FIG. 2, and the improvement in FIG. 3 is smaller than that in FIG. Therefore, at least the first phase shifter 12 should be compensated. Also,
From FIG. 4, it can be seen that the frequency band in which the output phase difference is 90 ° ± 2 ° is from 350 MHz to 800 MHz, and a wide band characteristic of 1 octave or more is obtained. Regarding the wide band property of the phase difference, a slight improvement effect can be seen by including the second capacitive element for compensation.

In the above description, a branch circuit with a fixed phase difference is explained, but at least one of the capacitive elements 27, 28, 31, 32 in FIG. 1 is a variable capacitance formed by a junction capacitance of a transistor, or in parallel therewith. Consists of a fixed capacitance element connected to
It is also possible to make the phase difference between both output signals variable. FIG. 5 shows an example of the circuit configuration in that case, in which the base and collector of the transistor Q ₃ are connected in the second phase shifter 13, and the connection point is connected to the emitter of the transistor Q ₂ . The emitter is connected to the output terminal 15 through the capacitive element 33, and the emitter is connected through the resistor 34 to the control terminal 35.
, And the junction capacitance between the base and emitter of the transistor Q ₃ forms a variable capacitance. The base-emitter junction capacitance of the transistor Q ₃ is changed by changing the voltage applied to the control terminal 22. In addition, a capacitive element 36 is connected between the emitter and collector of the transistor Q _{3 and} the capacitive element 36
Is for increasing the value of the entire capacitance that enters the emitter side of the transistor Q ₂ and thereby preventing the resistance element 28 from becoming extremely large, thereby suppressing the deterioration of the amplitude frequency characteristic of the output of the output terminal 15. Is. FIG. 6 is a circuit configuration example when the present invention is applied as a 90-degree phase synthesizing circuit. The first and second phase shifters 12 and 13 have input terminals 37,
Two signals are input from 38 and the first and second phase shifters 12 and 13 are input.
The respective outputs of the above are combined by the combining circuit 39 with a constant phase difference and output to the output terminal 41.

In the above description, the case of a bipolar transistor has been described, but the present invention can also be configured by using another device such as a FET. Further, the phase difference is not limited to the case of a phase difference of 90 degrees, but can be applied to a circuit of an arbitrary phase difference such as a 45 degree phase difference circuit.

[Advantages of the Invention] As described above, the phase synthesizing branch circuit according to the present invention can suppress the deterioration of the amplitude frequency characteristic in the high frequency band by compensating for the capacitance on the collector side of the transistor or the drain side of the FET. There is.

[Brief description of drawings]

FIG. 1 is a connection diagram showing an embodiment of a 90-degree phase branch circuit according to the present invention, and FIG. 2 is a diagram obtained by simulating pass characteristics to an output terminal 14 for a conventional configuration and a case of the present invention. FIG. 3 is a similar diagram of the pass characteristic of the output terminal 15, and FIG. 4 is a diagram similarly showing the output phase difference of the 90-degree phase branch circuit in the case of the conventional configuration and the case of the present invention. 5 is a connection diagram showing another configuration example of the 90-degree phase branch circuit according to the present invention, FIG. 6 is a connection diagram showing an example of the 90-degree phase synthesizing circuit of the present invention, and FIG. 7 is a conventional 90-degree phase branch circuit. Circuit configuration diagram, Fig. 8 is the frequency characteristic diagram of the output phase of the conventional 90-degree phase branch circuit, Fig. 9 is the frequency characteristic diagram of the output phase difference of the conventional 90-degree phase branch circuit, and Fig. 10 is the collector- It is a figure showing an example in which the effect on the frequency characteristics due to the capacitance between the boards was obtained by simulation. That.

Claims (2)

[Claims] 1. An input signal is supplied to a first phase shifter and a second phase shifter to be branched with a constant phase difference, or first and second input signals are respectively fed to a first phase shifter and a second phase shifter. Are supplied to the first and second phase shifters, and the outputs of the first and second phase shifters are phase-synthesized,
In the phase shifter, the collector and the emitter of the transistor, or the drain and the source of the FET are AC-grounded in such a manner that a DC voltage can be applied through different resistors, respectively, and between the collector and the emitter, or the drain and the source. A phase combining / branching circuit in which a series circuit of a resistance element and a capacitance element is connected between, the base of the transistor or the gate of the FET is used as an input terminal, and the connection point of the resistance element and the capacitance element is used as an output terminal. In the phase synthesizing method, the second capacitive element is connected between the collector and the emitter of at least one of the first and second phase shifters or between the drain and the source of the FET. Branch circuit. 2. The capacitance element and / or the second capacitance element is composed of a variable capacitance element formed by a junction capacitance of a transistor or a FET, or a fixed capacitance element connected in parallel with the variable capacitance element. The phase synthesizing / branching circuit according to claim 1, wherein: