JPH10209752A - Oscillation circuit configured as microwave integrated circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optimum oscillating state at a selected frequency, even when a resonance frequency of a resonance circuit is selected over a wide frequency range. SOLUTION: An externally mounted terminal 2 is placed to a gate of a control FET 3, and a resonance circuit 16 is connected to the terminal 2. A series connection circuit of a 1st feedback capacitor 6(C1 ) and a 1st switch FET 17, and a series connection circuit of a 2nd feedback capacitor (C2 )18 and a 2nd switch FET 19 are connected in parallel between a source of the FET 3 and a ground. Thus, the switching FETs 17, 19 are turned on/off with gate control voltages VG2 , VG3 to change, e.g. the feedback capacitance values to be 3 types and the oscillating state optimal for the 3 kinds of resonance frequencies is obtained. Furthermore, number of feedback capacitors and switch FETs is arbitrary.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave integrated circuit oscillating circuit, and more particularly to an oscillating circuit formed as a microwave monolithic IC (MMIC) having an externally mounted resonance circuit. The present invention relates to a microwave integrated circuit oscillating circuit to which a resonant circuit can be connected.

[0002]

2. Description of the Related Art Microwave integrated circuits (Microwave I)
C) As an oscillation circuit, for example, MMIC (Microwave Mono)
There is a lithographic IC (oscillator) circuit, which is an integrated circuit of an oscillator circuit on a gallium arsenide (GaAs) chip.

FIG. 5 shows an example of a conventional MMIC oscillation circuit. In FIG. 5, a resonance circuit 1 having a resonance frequency f0 is externally connected via a terminal 2 and a gate (G) of an oscillation FET 3 is provided. Connected to. A gate bias terminal 5 is arranged at the gate of the FET 3 via a choke coil 4, and a gate bias VG is supplied from the gate bias terminal 5. A feedback capacitor 6 having a capacitance value C1 is connected to the source (S) of the FET 3 and the ground, and a choke coil 7 is connected to the ground.

On the other hand, the drain (D) of the FET 3
A drain bias terminal 10 is arranged via a choke coil 9, and a drain bias VD is supplied from the drain bias terminal 10. Also, this drain
A load resistor 13 is connected via a matching circuit 11 and a DC preventing capacitor 12.

According to the above configuration, a Colpitts basic oscillation circuit shown in FIG. 6 is formed. That is, the gate width (W1) of the FET 3 is determined so as to have a sufficient oscillation capability in the required oscillation frequency band of the microwave band.
The internal capacitance 14 having the capacitance value Cgs shown in FIG. 5 is provided between the gate and the source substantially in proportion to the gate width. Therefore,
As shown in FIG. 6, a Colpitts-type oscillation circuit includes the internal capacitance (Cgs) 14 and the feedback capacitance (C1) 6. This oscillation circuit oscillates at the resonance frequency f0 obtained by the external resonance circuit 1.

[0006]

However, in the conventional MMIC oscillation circuit, if the resonance frequency of the resonance circuit 1 can be selected in a wide range, the feedback capacitance 6
Is a fixed value, there is a problem that an optimum oscillation state cannot be obtained. That is, as described above,
From the balance with the internal capacitance (Cgs) 14 determined by the gate width (W1) of the oscillation FET 3, the resonance frequency fo is determined.
Is arbitrarily selected in a wide range in the upper and lower bands, it is necessary to increase or decrease the capacitance value of the feedback capacitor 6 accordingly.

For example, when the resonance frequency is lower than the above f0, the capacitance value of the feedback capacitor 6 is increased. So that it will oscillate
The capacitance value of the feedback capacitor 6 must be changed. Therefore, it is difficult to obtain the optimum oscillation frequency in a wide range with the feedback capacitor 6 having the fixed capacitance value C1.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to obtain an optimum oscillation state at a selected frequency even when a resonance frequency of a resonance circuit is selected in a wide frequency range. It is an object of the present invention to provide a microwave integrated circuit oscillating circuit.

[0009]

In order to achieve the above object, the present invention provides an oscillation field effect transistor to which a resonance circuit is connected, and a feedback capacitor disposed on the source or drain side of the field effect transistor. And a switch for changing the feedback capacitance value by conducting or not conducting between the drain and the source on the drain side or the source side of the oscillation field effect transistor. A transistor is provided.

According to the above configuration, for example, the feedback capacitance is set to 2
By arranging two switching FETs so that these feedback capacitances can be switched, three capacitance values can be selected as the feedback capacitance. Therefore,
Even when a wide frequency range is used in a resonance circuit connected externally or the like, it is possible to obtain an optimum oscillation state for the selected frequency.

[0011]

FIG. 1 shows a configuration of a microwave integrated circuit (MMIC) oscillation circuit which is a first example of an embodiment of the present invention. This first example has two feedback capacitors. Can be used selectively. In FIG. 1, as in the conventional case, the external terminal 2 is connected to, for example, a resonance circuit 16, and the terminal 2 is connected to the gate (G) of the oscillation FET 3. A gate bias terminal 5 for applying a gate bias VG1 via a choke coil 4 is arranged at the gate of the FET 3, and a choke coil 7 is connected to the source of the FET 3 between the FET 3 and the ground.

On the other hand, a drain bias VD is applied to the drain (D) of the FET 3 through a choke coil 9.
And a load resistor 13 is connected via a matching circuit 11 and a DC preventing capacitor 12. The internal capacitance 14 having a capacitance value Cgs is provided between the gate and source of the FET 3 substantially in proportion to the gate width (W1) of the FET 3.

In the first example, the first feedback capacitor 6 having a capacitance value C1 and the first switch FET 17 are connected in series between the source (S) of the FET 3 and the ground.
A second feedback capacitor 18 having a capacitance value C2 (for example, C2 <C1) and a second switch FET 19 connected in series are arranged in parallel. That is, the switching FETs 17 and 19
Each of the feedback capacitors 6 and 18 is disposed on the drain side, the source side is grounded, and the gate of the first switch FET 17 is connected to the gate control voltage terminal 20 for supplying the gate control voltage VG2. The gate of the FET 19 is connected to a gate control voltage terminal 21 for supplying a gate control voltage VG3.

Further, each of the switching FETs 17, 19
As shown, choke coils 22 and 23 are arranged between the respective drains and the ground.

In the switching FETs 17 and 19,
By supplying the gate control voltages VG2 and VG3 of the ON voltage Von from the respective gate control voltage terminals 20 and 21, the transistors 17 and 19 are turned on, and the drains and sources of the FETs 17 and 19 are short-circuited. On the other hand, when the gate control voltages VG2 and VG3 of the pinch-off voltage Vp are supplied, the FETs 17 and 19 are rendered non-conductive and open between the drain and source of each of the FETs 17 and 19.

Accordingly, the above gate control voltage VG2
= Von, VG3 = Vp, the total feedback capacitance Cf between the source of the oscillation FET 3 and the ground is only the first feedback capacitance 6, and Cf = C1. In the above, when VG2 = Vp and VG3 = Von, only the second feedback capacitance 18 is effective, and the total feedback capacitance Cf is
If Cf = C2, and if VG2 = VG3 = Von, both are valid and Cf = C1 + C2.

In the embodiment, C1 and C2 are replaced by C2
<C1 <C1 + C2, and the resonance frequency of the resonance circuit 16 is, for example, f1, f2, f3 (f
If 1 <f2 <f3) is selected, Cf
= C1, frequency f2, and Cf = C2, frequency f3
, Cf = C1 + C2, the value is set so that the circuit oscillates optimally at the frequency f1. Thus, the first
In the example, the Colpitts basic oscillation circuit shown in FIG. 6 is formed.

According to the configuration of the first example, when the resonance frequency f2 is selected by the external resonance circuit 16, VG2 (gate control voltage) = Von, VG3 from the gate control voltage terminals 20 and 21. = Vp, and the frequency f2 due to the presence of the capacitance value C1 of the first feedback capacitor 6 and the internal capacitance value Cgs.
, An optimum oscillation state is obtained. When the resonance frequency of f3 is selected, the gate control voltage terminals 20, 2
1, VG2 = Vp and VG3 = Von are supplied, and the presence of the capacitance value C2 of the first feedback capacitor 18 and the internal capacitance value Cgs causes
When the optimum oscillation state is obtained at the frequency f3, and when the resonance frequency of f1 is selected, VG2 = VG3 = Von is supplied. A good oscillation state can be obtained.

FIG. 2 shows an MMI according to a second example of the embodiment.
The configuration of a C-type oscillation circuit is shown. In the second example, three feedback capacitors can be selectively used. The basic structure is the same as that of the first example. In addition to the configuration of the first example, a third feedback capacitor 26 having a capacitance value C3 and a third switch are provided between the source of the oscillation FET 3 and the ground. F
ET27, other feedback capacitors 6, 18 and FE for switch
It is arranged in a parallel relationship with T17 and T19. And the third
A gate control terminal 28 for applying a control voltage VG4 is provided at the gate of the switching FET 27, and a choke coil 29 is arranged at the drain.

According to the configuration of the second example, the switch F
By the conduction / non-conduction operation of the ETs 17, 19 and 27, the total feedback capacitance Cf is reduced to C1, C2, C3, C1 + C2, C
It can be set to 7 values of 2 + C3, C1 + C3, C1 + C2 + C3, and an optimum oscillation state can be obtained at at least seven resonance frequencies. In the same manner as in the second example, the feedback capacitance and the switching FET
It is also possible to arrange more than one and obtain an optimum oscillation state for many frequencies.

FIG. 3 shows an MMI according to a third example of the embodiment.
The configuration of the C oscillation circuit is shown. In this third example,
The first feedback capacitor 6 and the second feedback capacitor 18 are provided. A switching FET 19 (and a choke coil 23) is disposed only in the second feedback capacitor 18, and the switching FET 19
Gate control voltage terminal 30 for applying gate control voltage VG2 to
Is provided.

According to the third example, the switching FET 1
9, the feedback capacitance Cf is changed to C1,
C1 + C2 can be set to two values, and an optimum oscillation state can be obtained at two resonance frequencies.

FIG. 4 shows a configuration of an MMIC oscillation circuit according to a fourth example of the embodiment. In this example, the first feedback capacitance 6 is directly grounded, and the first feedback capacitance 6 is switched. , A switching FET 31 and a gate control voltage terminal 32 are arranged.

According to this, when the switching FET 31 is non-conductive, it operates as an oscillator based on the capacitance C1, but when the switching FET 31 is conductive, the source of the oscillation FET 3 is directly grounded. As a result, oscillation stops.

In the above embodiment, the feedback capacitance (6, 18, 26) and the switching F
Although the example in which the ETs (17, 19, 27, 31) are arranged has been described, a configuration in which these members are arranged on the drain side of the oscillation FET 3 and the arrangement relation between the drain side and the source side is reversed. It is possible.

[0026]

As described above, according to the present invention,
In a microwave integrated circuit oscillating circuit that forms a feedback capacitance on the source side or the drain side of the oscillation field effect transistor, at least one switching transistor is arranged together with the feedback capacitance, and a gate control voltage is controlled to control the feedback capacitance. Since the value is changed, even when the resonance frequency is selected in a wide frequency range, an optimum oscillation state can be obtained at the selected frequency, and there is an advantage that stable oscillation can be realized in each resonance frequency band.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a microwave integrated circuit oscillation circuit according to a first example of an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration of an oscillation circuit according to a second example of the embodiment.

FIG. 3 is a circuit diagram showing a configuration of an oscillation circuit according to a third example of the embodiment.

FIG. 4 is a circuit diagram illustrating a configuration of an oscillation circuit according to a fourth example of the embodiment.

FIG. 5 is a circuit diagram showing a configuration of a conventional microwave integrated circuit oscillation circuit.

FIG. 6 is a circuit diagram showing a configuration of a fundamental oscillation circuit of Colpitts.

[Explanation of symbols]

 1, 16: resonance circuit, 2: external terminal, 3: oscillation FET, 6, 18, 26: feedback capacitance, 11: matching circuit, 14: internal capacitance between gate and source, 17, 19, 27, 31 ... FET for switch.

Claims (1)

[Claims] 1. A microwave integrated circuit oscillating circuit comprising: an oscillation field-effect transistor to which a resonance circuit is connected; and a feedback capacitor arranged on a source side or a drain side of the field-effect transistor. A switching transistor for changing the feedback capacitance value between the drain and the source by conducting or not conducting between the drain and the source of the field effect transistor for use in a microwave integrated circuit oscillation circuit. .