JPH04133507A - High-frequency oscillation circuit - Google Patents

Abstract

PURPOSE:To enable this oscillation circuit to stably oscillate even when the impedance component of a load is fluctuated by cascade-connecting the transistor for the oscillation of a negative resistance circuit section and the transistor for the amplification of an amplifier circuit section and grounding the base of the transistor for amplification through a capacitor. CONSTITUTION:A negative resistance circuit section (b) is constituted of a 1st transistor Q1 for oscillation, capacitors C3-C5, resistance, etc., and adjusts the oscillating condition of this high-frequency oscillation circuit together with a resonant circuit section (a). An amplification circuit section (c) amplifies a prescribed frequency generated by the circuit sections (a) and (b). The base of a 2nd transistor Q2 for amplification of the circuit section (c) is grounded through a by-pass capacitor C6 and the transistors Q1 and Q2 are cascade- connected to each other. Therefore, the impedance on the emitter side of the transistor Q2 becomes lower even when the impedance component Z of a load is fluctuated, since the base of the transistor Q2 is grounded through the capacitor C6. Thus, such a state that the impedance component of the load is interrupted is realized for a high frequency.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention relates to, for example, an oscillation circuit suitable for high-frequency oscillation, and more specifically, to a high-frequency oscillation circuit capable of stable oscillation against changes in load impedance. It is related to.

[Prior art and its problems] Conventionally, oscillation circuits for mobile communication devices, typically car phones, include an M (mega) Hz band resonance circuit section, a negative resistance circuit section, and an amplifier circuit section. A high frequency oscillation circuit is used.

FIG. 2 is a circuit diagram of a conventional high frequency oscillation circuit.

The high frequency oscillation circuit includes a resonant circuit section a including a resonant element R;
The negative resistance circuit section consisting of active elements is composed of an amplifier circuit section C.

The resonant circuit section a includes a resonant element R consisting of a dielectric coaxial resonator or a microstrip line, a varicap diode Cv whose capacitance changes depending on the control voltage, a capacitor CI for determining the variable range of the oscillation frequency, and a clap capacitor C2. , microstrip line, etc.

The negative resistance circuit section is mainly the first transistor Q for oscillation.
1, a bypass capacitor 05, etc., and the collector of the first transistor Q is grounded via the bypass capacitor C2.

The amplifier circuit section C mainly includes a second transistor Q2 for amplification,
Bypass capacitor C3, microstrip line L2
Consists of etc. The base of the second transistor Q2 for amplification is connected to the emitter of the first transistor Q1 for oscillation of the negative resistance circuit section.

A signal of a predetermined frequency amplified by this second amplifying transistor Q2 is derived from the emitter side of the second transistor Q2.

"Problem to be Solved by the Invention" However, even in the above-mentioned oscillation circuit, there is a decisive problem that the oscillation characteristics become unstable due to the load impedance connected to the output terminal P of the second transistor Q2 for amplification. there were. The oscillation frequency is
Since it is the basis for determining the communication frequency, if the oscillation characteristics become unstable, calls may become impossible or interference may occur.

This is because the base-collector capacitance of the second transistor Q2 acts as a coupling capacitance between the load impedance component Z and the input impedance component Zin, and when the load impedance component Z changes, the input impedance component Zin also changes accordingly. This is because you end up doing it.

The present invention was developed in order to solve the above-mentioned problems, and its purpose is to provide a high frequency oscillation circuit capable of stable oscillation even when the load impedance component fluctuates.

"Means for Solving the Problems" The oscillation circuit of the present invention includes a resonant circuit section including a resonator, a negative resistance circuit section including an oscillation transistor, and an amplification circuit section including an amplification transistor.

The resonant circuit section and the negative resistance circuit section constitute an oscillation section,
The oscillation transistor of the negative resistance circuit section and the amplification transistor of the amplification circuit section are connected in cascade, and the base of the amplification transistor is grounded via a capacitor.

"Function" With the above configuration, even if the impedance component Z of the load connected to the emitter side of the amplification transistor fluctuates greatly, the base of the amplification transistor is grounded in terms of high frequency. The capacitance between collectors can be ignored.

Therefore, fluctuations in the load impedance component Z do not affect the input impedance component Zin.
The oscillation frequency created by the resonance circuit section and the negative resistance circuit section is stably supplied to the amplifier circuit section.

"Example" Hereinafter, the oscillation circuit of the present invention will be explained in detail based on the drawings.

FIG. 1 is a circuit diagram of an oscillation circuit according to the present invention.

The oscillation circuit is composed of a resonant circuit section a, a negative resistance circuit section and an amplifier circuit section C.

The resonant circuit part a includes the microstrip line 1 and the capacitance C.
0 and a haricap diode C.
V, capacitors 01 to C2, microstrip line, etc.

In the resonant circuit section a, an oscillation frequency is created at a desired resonant frequency by the capacitance of the paricamp diode Cv controlled by the applied voltage.

Here, the resonant element R of the resonant circuit section a is composed of a microstrip line 1 and an additional capacitor CX. In particular, the microstrip line 1 is minimized in both line length and width. In order to obtain the same characteristics as the conventional one only in the resonant element R, the line length must be 6.2 m and the line width must be 1.0 m.
It can be formed by m. In the miniaturized microstrip line 1, the natural resonant frequency of the microstrip line 1 increases by about six times, to, for example, 4.7 GHz.
This lowers the intended resonance frequency of the resonance circuit section a to 900MHz.

The negative resistance circuit section is composed of a first transistor Q for oscillation, which is an active element, capacitors 03 to C5, resistors, and the like. This negative resistance circuit section is a resonant circuit section a.
At the same time, it also prepares oscillation conditions, and provides an oscillation output to the amplifier circuit section C. The collector of the first oscillation transistor Q is grounded via a capacitor C5, but the capacitance of this bypass capacitor C5 is selected to such an extent that it is not completely grounded at high frequencies. As a result, the oscillation conditions of the oscillation section consisting of the resonant circuit section a and the negative resistance circuit section 2 are satisfied. Furthermore, if the capacitance of the capacitor C3 is too large, the signal level will be greatly attenuated.

Therefore, the capacitance of the capacitor C is selected within a range that satisfies the oscillation conditions and has a small degree of attenuation.

The amplifier circuit section C is composed of a second amplifying transistor Q2, a bypass capacitor C6, a microstrip line L2, capacitors C1 to C8, resistors, and the like.

The amplifying circuit section C amplifies the desired frequency generated by the resonant circuit section a and the negative resistance circuit section A.
A predetermined oscillation signal is derived from a terminal P extending from the collector side of the transistor Q2.

In particular, the base of the second transistor Q2 for amplification in the amplification circuit section C is grounded via the bypass capacitor C6, and the emitter of the second transistor Q2 for amplification is the first transistor for oscillation of the negative resistance circuit section C. The collector of transistor Q1 is grounded.

That is, the first transistor Q and the second transistor Q2 are connected in cascade.

As a result, even if the impedance component Z of the load connected to the terminal P fluctuates, the base of the second transistor QZ is grounded by the bypass capacitor C4, so the impedance on the emitter side of the second transistor Q2 becomes low. In terms of high frequency, the impedance component Z of the load is cut off.

That is, since the variation in the load impedance component Z has almost no effect on the input impedance Zin when looking at the amplifier circuit section C, since the variation in the load impedance component Z is caused by the negative resistance circuit section.

Therefore, no matter what kind of load is connected to the terminal P, the high-frequency oscillation circuit becomes a high-frequency oscillation circuit in which stable start is achieved without fluctuations in the desired oscillation frequency determined by the resonant circuit section a and the negative resistance circuit section. .

In addition, the first transistor Q1 and the second transistor Q
2 are connected in cascade, and only the resistor r on the emitter side of the first transistor Q serves as a current bias, making it possible to reduce current consumption.

Moreover, this cascade connection simplifies the circuit between the negative resistance circuit section and the amplifier circuit section C, and improves the degree of freedom in circuit pattern design.

In addition, as the resonator R of the above-mentioned resonant circuit part a, preferably, as surrounded by a dotted line, a miniaturized microstrip line 1 and a microstrip line 1 connected in parallel to one end of the microstrip line 1 are used. A circuit combining the additional capacitance component CX may also be used. By using this resonator R, the size of the resonator R itself can be made extremely small compared to those using a dielectric coaxial resonator or a normal microstrip line. Can be made smaller.

"Effects of the Invention" As described above, in the present invention, an amplifier circuit section is provided in the oscillation section of the resonant circuit section and the negative resistance circuit section, and a transistor of the negative resistance circuit section and a transistor of the amplifier circuit section are provided. Since they are configured to be connected in cascade and the transistors in the amplifier circuit section are grounded to the base, the high frequency oscillation circuit can stably oscillate even in response to fluctuations in the impedance component of the load.

It also simplifies the circuit, increases design freedom, reduces size,
It becomes an inexpensive high frequency oscillation circuit.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a high frequency oscillation circuit of the present invention, and FIG. 2 is a circuit diagram of a conventional oscillation circuit. 1...Microstrip line Ql...First transistor Q2...Second transistor C5 to C7...Capacitor CX...Additional capacitance a...Resonant circuit part b...Natural resistance Circuit part C... Amplifier circuit part Applicant: Kyocera Corporation

Claims (1)

[Claims] (1) A resonant circuit section having a resonator, a negative resistance circuit section having a first transistor that adjusts oscillation conditions together with the resonant circuit, and a second transistor for amplifying the oscillation output of the negative resistance circuit section. In a high frequency oscillation circuit consisting of an amplifier circuit section having a transistor, the second transistor of the amplifier circuit section and the first transistor of the negative resistance circuit section are continuously connected, and the base side of the second transistor is connected to a capacitor. A high-frequency oscillation circuit characterized by being grounded through.