JPH10200333A - Transistor oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oscillator for a microwave with a small phase noise and high stability. SOLUTION: This oscillator is provided with a transistor 1 operating in a microwave band, a microwave line 2 connected with a base B of the transistor 1, and a dielectric resonator 3 provided connected with the microwave line 2. Then, the microwave line 2 is provided with a length which is 1/2 the wavelength of an oscillated frequency so that the end can be open-circuited, or this is provided with a length which is 1/4 the wavelength or the odd times as long as that so that the end can be short-circuited. Moreover, the dielectric resonator 3 is provided with a resonance frequency matching the above resonance frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oscillator in a microwave band, for example, used as a local oscillator of a converter for receiving satellite broadcasting. More specifically, the present invention relates to a microwave-band transistor oscillator using a combination of a microwave line and a dielectric resonator as a transistor.

[0002]

2. Description of the Related Art Conventionally, as an oscillator in the microwave band, for example, as shown in Japanese Patent Publication No. 60-48921 and Japanese Patent Publication No. 62-48925, a field effect transistor (hereinafter referred to as FET) is used. 2. Description of the Related Art Oscillators that oscillate at a resonance frequency of a dielectric resonator using a microstrip line and a dielectric resonator are used in various structures.

FIG. 4 shows an example of a microwave band oscillator using an FET and a dielectric resonator. In FIG. 4, Q ₁₁ is FET, to its drain D side, has a drain grounded type oscillation circuit for short-circuiting 1/4 open stub S ₁₂ is provided for wavelengths high frequency. Dielectric resonator 13 is provided to be coupled with the microstrip line S ₁₁ of the gate G side, by the position of the dielectric resonator 13 is adjusted, by remembering inductive reactance to the gate G side, the source It oscillates as a negative resistance element when viewed from the side. The other end portion of the microstrip line S ₁₁ of the gate G side is connected to ground via a resistor R _g of about 50 [Omega, the drain D side, the power supply Vd through the coil L ₁₁ to cut the high frequency is supplied to the source S, the source resistor R ₁₁ is connected to the source resistance R ₁₁
The output from is in the structure to be taken out through the capacitor C ₁₁ of the DC cut.

On the other hand, an oscillator using a transistor generally oscillates by providing a part of the output of the transistor by positive feedback using a parallel resonance circuit or the like.
For a high frequency such as a microwave band, it has not been put to practical use because the cutoff frequency of the transistor cannot be increased.

[0005]

The FET can easily oscillate in the microwave band, but generally has a problem that the phase noise is larger than that of the transistor and stable oscillation cannot be obtained.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a highly stable microwave oscillator having small phase noise.

[0007]

A transistor oscillator according to the present invention comprises a transistor operating in a microwave band, a microwave line connected to a base of the transistor, and a dielectric line provided to be coupled to the microwave line. The microwave line is provided with its tip open at a length of 1/2 wavelength of the frequency oscillated by the microwave line, or the tip is provided at a length of 1/4 wavelength or an odd multiple thereof. It is provided with a short circuit and has a resonance frequency that matches the oscillation frequency of the dielectric resonator.

Here, the microwave line means a line for transmitting microwaves, such as a microstrip line (line) or a coaxial line.

A microwave line slightly shorter than a half wavelength of the oscillating frequency and having an open end is connected to the collector side of the transistor, or a quarter wavelength or an odd number thereof. The fact that the microwave line whose length is slightly shorter than the double length and whose tip is short-circuited is connected creates an inductive reactance, and a dielectric resonator is provided between the collector side of the transistor and the base line via a dielectric resonator. Since an oscillation circuit can be formed, stable oscillation is preferably obtained.

[0010] Here, "slightly shorter than the length of 1/2 wavelength or 1/4 wavelength or an odd multiple thereof" means the length of 1/2 wavelength or 1/4 wavelength which is the boundary between the inductive reactance and the capacitive reactance. Rather, it means a state in which the length is reduced to the length at which the inductive reactance is formed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a transistor oscillator according to the present invention will be described with reference to the drawings.

FIG. 1 is a diagram illustrating the configuration of an embodiment of the transistor oscillator of the present invention. In FIG. 1, reference numeral 1 denotes a transistor, and a microstrip line 2 is connected to a base B of the transistor at a length of の of a wavelength of an oscillation frequency oscillated by the oscillator, and an end thereof is open. A dielectric resonator 3 is provided near the microstrip line 2. In order to oscillate at the resonance frequency of the dielectric resonator 3, the dielectric resonator 3 is selected according to a required oscillation frequency, and is provided so as to be coupled to the microstrip line 2. The base B of the transistor 1 has a bias resistor R ₁
And choke coil L for cutting microwave
_The power supply terminal 5 is connected via ₁ .

A power supply terminal 5 is connected to the collector C of the transistor 1 via a coil L ₂ , so that power is supplied and microwaves are cut off. Then, through the capacitor C ₂ of the DC blocking output from terminal 6 is taken out. In the example shown in FIG. 1, the microstrip line 4 is also connected to the collector C, and its length is formed to be slightly shorter than １ ／ of the wavelength of the above-mentioned oscillation frequency. Open (open). The emitter E of the transistor 1 is connected to the ground.

A transistor oscillator having the structure shown in FIG.
FIG. 2 shows an equivalent circuit of the oscillation circuit of FIG. In FIG.
R of transistor 1_b, C_bIs the resistance and capacitance of the base
And R _e, C_eIs the resistance and capacitance of the emitter, C_cIs
The capacity of the collector is shown. Also, the dielectric resonator 3
Is the inductance component of X_L, The capacity component is X_CIndicated by
These components are in series resonance at the resonance frequency.
Is set to Note that L_Two, C_TwoIs for power supply
Choke coil and DC cut capacitor
Each is shown. This choke coil has a lumped constant
It may be a circuit or a 1/4 wavelength transmission line.

According to the transistor oscillator of the present invention, as described above, the base is connected to the microstrip line having a length of half the wavelength of the oscillation frequency, and the tip is open. Therefore, the impedance from the base increases for frequencies different from the oscillation frequency, and only when the frequency matches the oscillation frequency, the dielectric resonator 3
And low impedance. As a result, the base current flows, the transistor operates, and oscillation can be performed.
On the other hand, the base current hardly flows for other frequencies,
No oscillation occurs. Therefore, it operates as an oscillator that oscillates only at a desired frequency.

Next, the operation of the strip line 4 connected to the collector C will be described. Generally, as shown in FIG. 3, the impedance of a strip line having one open end changes from a capacitive reactance to an inductive reactance according to its length. When the length is a half wavelength, it is at the boundary between the inductive reactance and the capacitive reactance. By making the length slightly shorter than the half wavelength, the inductive reactance shown in FIG. , Together with the collector capacitance and the emitter capacitance of the transistor, constitute an oscillation circuit. As a result, resonance of the collector can be obtained, and matching with the output can be obtained.

In the example described above, the length of the microstrip line connected to the base and the collector is reduced by half.
Although the tip is open as the wavelength, the impedance on the line side viewed from the base and the collector may be increased (to infinity). The same is true if the tip is short-circuited. In addition, when the length is set to the above-mentioned half wavelength, it is needless to say that the same applies to an integral multiple thereof.

Further, although the microstrip line is used as the microwave line, another line such as a coaxial line may be used as long as the line is provided so as to be coupled to the dielectric resonator.

[0019]

According to the present invention, an FET is used as an oscillation element.
Instead, phase noise can be suppressed because a transistor is used. Therefore, for example, when used as a local oscillator of a receiving converter for satellite broadcasting, the phase noise is small and the CN ratio can be increased, so that the performance of the receiving converter can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a transistor oscillator of the present invention.

FIG. 2 is an equivalent circuit diagram of the oscillation circuit having the configuration of FIG.

FIG. 3 is a diagram showing a relationship between a length of a strip line and a change in impedance.

FIG. 4 is a diagram showing an example of an oscillator using a conventional FET.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transistor 2 Strip line 3 Dielectric resonator 4 Strip line

Claims (3)

[Claims] 1. A microwave line, comprising: a transistor operating in a microwave band; a microwave line connected to a base of the transistor; and a dielectric resonator provided to be coupled to the microwave line. A transistor oscillator having a resonance frequency that is equal to the oscillation frequency of the dielectric resonator, the oscillation frequency being provided at an end of a half wavelength of the oscillation frequency of the dielectric resonator. 2. The transistor oscillator according to claim 1, wherein said microwave line has one of said oscillating frequencies.
A transistor oscillator having a length of / 4 wavelength or an odd multiple thereof and whose tip is short-circuited. 3. A microwave line slightly shorter than a half wavelength of the oscillating frequency on the collector side of the transistor and having an open end, or a 波長 wavelength of the oscillating frequency or 3. The transistor oscillator according to claim 1, wherein a microwave line slightly shorter than an odd multiple thereof and having a short-circuited end is connected.