JP2700015B2 - Microwave oscillation circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave oscillation circuit for local oscillation such as a low noise block down converter (LNB) for satellite broadcasting and satellite communication shared reception.

[0002]

2. Description of the Related Art FIG. 2 shows a microwave oscillation circuit diagram of a conventional low noise block down converter (LNB) and the like. The field effect transistor 1 is operated with the drain D grounded, and a dielectric resonator 10 having a resonance frequency equal to the oscillation frequency is coupled to a resonance circuit 4 such as a microstrip line at a position of an electrical length L from the gate G terminal, and has a high Q. It is an oscillation circuit.
On the other hand, an output matching circuit 3 is provided at the source S terminal, and a microwave oscillation circuit including a feedback circuit 2 whose impedance when viewed from the output terminal to the field effect transistor 1 side shows a negative resistance at a predetermined oscillation frequency. Oscillation output 13 from end
Get. Therefore, an LNB that receives satellite broadcasting BS and satellite communication CS, etc., requires a plurality of local oscillation frequencies, that is, a plurality of microwave oscillation circuits, and a dielectric resonance to obtain a stable oscillation state. It requires a certain amount of space such as the position of the device 10 (the distance from the resonance circuit 4 and the distance L from the field-effect transistor 1) and the distance from the shield case that shields the oscillation circuit. And the like.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above conventional example, and aims at miniaturization and cost reduction having a plurality of oscillation frequencies for shared reception of satellite broadcasting BS and satellite communication CS. Provided is a microwave oscillation circuit for local oscillation.

[0004]

According to the present invention, a single gate field effect transistor is used as an oscillating element, and a plurality of resonance circuits formed by branched microstrip lines having different resonance frequencies are coupled to a gate circuit of the field effect transistor. In addition, a switch circuit operation of oscillating at the resonance frequency of one resonance circuit and short-circuiting and grounding the other resonance circuit at a high frequency, and oscillating and outputting a plurality of oscillation frequencies with one oscillation element.

[0005]

The oscillation element 1, the drain D side feedback circuit 2, the source S side output matching circuit 3, and the microstrip line resonance circuit 4 (4a, 4) shown in FIG.
b), coupling capacitors 5a and 5b, switching diodes 6a and 6b, microwave short-circuit capacitors 7a and 7b, bias resistors 8a and 8b, high-frequency choke coils 9a and 9b, dielectric resonance having a resonance frequency equal to the oscillation frequency Vessels 10a, 10b
, The terminating resistors 11a and 11b of the resonance circuits 4a and 4b, the oscillation frequency selection switch circuit 12, and the like. Switch circuit 12
Is switched to the a side and the switching power supply B1 is applied, the switching diode 6b is turned on, and the capacitor 5b, the diode 6b, and the microwave short-circuit capacitor 7b
The resonance circuit 4b is short-circuited at high frequency by the bypass circuit of
An oscillation output 13 having a stable resonance frequency of the other resonance circuit 4a is obtained from the output terminal of the matching circuit 3. Also, the switch circuit 12
Is switched to the b side, the switching diode 6a is turned on, the resonance circuit 4a is short-circuited at a high frequency, and an oscillation output 13 having a stable resonance frequency of the resonance circuit 4b is obtained from the output terminal of the matching circuit 3.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a local oscillation microwave oscillation circuit such as a low noise block down converter (LNB) for receiving satellite broadcasting BS and satellite communication CS and the like in common. In FIG. 1, reference numeral 1 denotes an oscillation element formed by a field-effect transistor having a drain D grounded and a single gate G.
The resonance circuit of the gate G by the branched microstrip line having a and 11b, and 10a and 10b respectively represent the gate G
Electrical lengths L1 + (input 1 wavelength / 2) and L2 + from terminal
A dielectric resonator having a resonance frequency equal to the emission frequency equivalent to a microwave oscillating circuit having an equivalently high Q by combining with the resonance circuits 4a and 4b at (2 wavelength / 2) distant positions; Coupling capacitors connected at positions (in 1/4) and (in 2/4) away from the gate G of each of 4a and 4b
5a, 5b, switching diodes 6a, 6b, microwave short-circuit capacitors 7a, 7b, and bias resistors 8a, 8b circuit respectively connect the resonance circuits 4a, 4b to a switching power supply Bl.
Circuit, 9a, 9b that short-circuits at high frequency by applying
Is a choke coil for cutting off high frequency, 12 is an oscillation frequency selection switch circuit by a switching power supply Bl, 2 is a series feedback circuit of a drain D ground by a microstrip line or the like, 3 is a field effect transistor 1 from a source S terminal.
A matching circuit such as a microstrip line for the oscillation output 13 that satisfies the condition that the impedance anticipated at the predetermined oscillation frequency indicates a negative resistance characteristic. In addition, the electric length L1
+ (Incoming 1 wavelength / 2) , L2 + (Incoming 2 wavelength / 2) is the distance at which the S parameter of the field effect transistor 1 is converted into the S parameter when the drain D ground is used, and the calculated negative resistance becomes maximum. It depends on the oscillation element 1 and the frequency. For example
The S parameter of the oscillation element 1 is
As typical values, S11 = 0.404 + 1.306j, S12 = 0.450-0.384
j, S21 = 0.405 + 1.394j, S22 = 0.083-0.266j
Wave number corresponding to satellite broadcasting BS and satellite communication CS respectively
Assuming 10.5 GHz and 11.0 GHz,
When the patient's length is calculated, the above L1, L2 for BS and CS are
Approximately 3.88mm and 0.77mm respectively. Note that this value is
0.564mm, thickness 0.01 on Teflon substrate with relative dielectric constant 2.60
The above microstrip line was composed of 8mm copper foil
Is the case. In this case, the wavelength in the line is BS, CS
Are approximately 19.38 mm and 18.49 mm, respectively.
Therefore, the above (input 1/4) and (input
2/4) are about 4.85 mm and 4.62 mm, respectively .

The principle of oscillation by a microstrip line is that, when a frequency component generated at the time of a transient phenomenon due to power-on of an oscillation circuit is transmitted through the microstrip lines 4a and 4b on the gate G side, the microstrip lines 4a and 4b are coupled to each other by an electromagnetic field. The same frequency components as the resonance frequencies of the dielectric resonators 10a and 10b are reflected and input to the field effect transistor 1, amplified, and then output from the matching circuit 3 on the source S side.
And the feedback circuit 2 on the drain D side to the gate G
It returns to the side microstrip lines 4a and 4b, further reflects at the dielectric resonators 10a and 10b, returns to the field effect transistor 1, amplifies again, becomes saturated, and oscillation is stabilized.

A bias power supply B2 for the drain D feedback circuit 2
When the switching circuit 12 is switched to the terminal a side and the switching power supply B1 is applied in the operation state of the oscillation circuit by the application of the
Is turned on by being biased in the forward direction (the diode 6a is in the reverse direction), and (λ 2/4) from the gate G of the resonance circuit 4b.
The distant position is short-circuited at a high frequency by the capacitor 5b, the diode 6b and the microwave short-circuit capacitor 7b, so that the resonance circuit 4b is in the oscillation stop state. Wave signal 13
Is output from the matching circuit 3. Further, when the switch circuit 12 is switched to the terminal b side, the switching diode 6a is biased in the forward direction (the diode 6b is in the reverse direction) by the grounding of the resistor 8a and is turned on, and (λ1 / 4) Separate positions are capacitor 5a and diode 6a
Also, by short-circuiting at a high frequency by the microwave short-circuiting capacitor 7a, the resonance circuit 4a is stopped from oscillating, and a microwave signal 13 at the frequency of the other resonance circuit 4b performing stable oscillation is output from the matching circuit 3. I do.

[0009]

As described above, according to the present invention, a single-gate field-effect transistor is used as an oscillation element, and a plurality of resonance circuits such as branched microstrip lines having different resonance frequencies are used in the gate circuit of the field-effect transistor. Coupled, oscillates at the resonance frequency of one of the resonance circuits, and switches the other resonance circuit to short-circuit and ground at high frequency. Provided is a microwave oscillation circuit for local oscillation that has a plurality of oscillation frequencies for shared reception of BS, satellite communication CS, and the like and that is reduced in size and cost.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram of a microwave oscillation circuit having a plurality of oscillation frequencies for receiving satellite broadcasting and satellite communication in a shared manner.

FIG. 2 is an electric circuit diagram of a conventional microwave oscillation circuit using a single oscillation frequency.

[Explanation of symbols]

 Reference Signs List 1 field effect transistor 2 feedback circuit 3 output matching circuit 4 resonance circuit 4a resonance circuit 4b resonance circuit 5a coupling capacitor 5b coupling capacitor 6a switching diode 6b switching diode 7a short-circuit grounding capacitor 7b short-circuit grounding capacitor 8a bias Resistor 8b Bias resistor 9a High-frequency choke coil 9b High-frequency choke coil 10 Dielectric resonator 10a Dielectric resonator 10b Dielectric resonator 11 Termination resistor 11a Termination resistor 11b Termination resistor 12 Oscillation frequency selection switch circuit B1 Switching power supply

Claims (2)

(57) [Claims] 1. A first and a second field-effect transistor connected to a gate terminal in a branched manner and connected to a grounded drain.
And the second microstrip line
Two dielectric resonators having a resonance frequency equal to the frequency
Coupled at each electrical length from the gate terminal
Oscillates two oscillation frequencies consisting of two resonance circuits
The two microstrip lines described above.
The inn, the switching times <br/> path alternately performing RF grounding at the quarter wave position of the respective resonant frequencies from the gate terminal is provided, by selecting one of the two oscillation frequencies < A microwave oscillation circuit characterized by outputting. 2. The switching circuit according to claim 1 , wherein the switching circuit includes :
A first coupling capacitor and a second coupling capacitor on each of the cross trip lines, and a first switching capacitor having the coupling first and second capacitors on the anode side.
And a second short-circuit grounding first capacitor and a second capacitor having a parallel resistance for biasing are sequentially connected, and an anode of the diode is connected to the second diode via a high-frequency choke coil. The cathode of the diode is connected to one terminal of the switch circuit, and the anode of the second diode is connected to the cathode of the first diode and the other terminal of the switch circuit via a second high-frequency choke coil. 2. The microwave oscillation circuit according to claim 1 , wherein the switching power supply is selectively supplied to one of the first diode and the second diode by the switch circuit.