JPS626504A - Voltage controlled oscillator - Google Patents

Abstract

PURPOSE:To obtain a continuous change in an oscillating frequency at a microwave band by impressing switchingly a fixed voltage or a frequency control voltage to plural varactor diodes so as to switch the oscillating frequency band. CONSTITUTION:The oscillation circuit is constituted by connecting plural varactor diodes 23, 24 or a capacitive circuit including a varactor diode between mirostrip resonance lines 20, 21 and ground and connecting a negative resistance circuit to one of the microstrip lines 20, 21. A fixed maximum control voltage V2 is impressed to, e.g., the varactor diode D2 to minimize the capacitance of the diode D2, a variable control voltage is impressed to the diode D1 to change the capacitance of the diode D1 thereby varying the oscillating frequency at a high frequency region A. Further, the control voltage of the diode D1 is fixed to a low control voltage V1 to increase the equivalent capacitance of the diode D1 and to decrease the oscillating frequency region, further a variable turning voltage is fed to the diode D2 to vary the oscillating frequency at a low frequency region B.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a voltage controlled oscillator that switches oscillation frequency bands.

[Background of the invention]

As a means of obtaining oscillation frequencies over a wide range of microwave bands, one oscillation frequency band is divided.

Compensating for the small rate of change of variable capacitance diodes is being carried out. In Japanese Patent Application Laid-open No. 60-1904, the terminal capacitance of the positive input line is switched by a switching diode to obtain an oscillation frequency variation range of one octave or more. When switching the oscillation frequency band using such a switching diode, when used in the microwave frequency band, one oscillation frequency change becomes discontinuous due to the lead inductance of the switching diode, resulting in a region that cannot be covered by the oscillation frequency. Sufficient oscillation frequency switching may not be possible.

[Purpose of the invention]

The object of the present invention is to provide a voltage controlled oscillator that can switch the oscillation frequency favorably in the microwave band.

[Summary of the invention]

Therefore, the present invention uses a plurality of variable capacitance diodes and switches the oscillation frequency band depending on whether or not an oscillation frequency control voltage terminal is applied to the variable capacitance diodes.

[Embodiments of the invention]

EMBODIMENT OF THE INVENTION Below, one embodiment of the present invention will be described in detail based on the drawings.

FIG. 1 is a diagram showing an embodiment of a voltage controlled oscillator according to the present invention. In Figure 1, 1 is a transistor, 2 is a microstrip line 3 is a capacitor, and this series circuit forms a feedback impedance, and the impedance of the microstrip line 4 connected to the emitter of transistor 1 causes negative Causes resistance. 5,
6 has a line length equivalent to 1V1f wavelength in the oscillation frequency band.
- A bias line consisting of an impedance microstrip line, 9, to, 11.12 are bias resistors, 13 is a bus capacitor, and 8 is a coupling capacitor for outputting an oscillation signal. A power supply voltage is supplied to the transistor 1 from the 10B power supply voltage terminal via the negative line 5. 7 is a coupling capacitor, and 20 and 21 are resonant lines consisting of microstrip lines.

22 is a connecting capacitor for cutting DC between the resonant lines;
23 and 24 are variable capacitance diodes, 25 and 26 are bias lines consisting of high impedance microstrip lines corresponding to approximately + wavelength in the oscillation frequency band, 2
7, 28) -1 bias resistor, 29.30 is a bypass capacitor. Further, VTI is the oscillation frequency control chamber terminal of D1, and VT2 is the oscillation frequency control chamber terminal of D2.

The voltage controlled oscillator shown in FIG.
The oscillation frequency is determined by the resonant frequency of the resonant circuit terminated at Df). Figure @2 shows the oscillation frequency change characteristics with respect to the control voltage of the voltage controlled oscillator of Figure 1. In the A characteristic shown in FIG. 2, a fixed maximum control voltage v2 is applied to the variable capacitance diode D2 so that the capacitance of D2 is minimized. At this time, a variable control voltage is applied to D1 to change the capacitance of D1 and vary the oscillation frequency in a high frequency range. In the Be characteristic shown in Figure 2, the control voltage of Dl is fixed at a low control voltage vl, the equivalent capacitance of DI is reduced, the oscillation frequency region is lowered, and then D2 is switched to DI, and a variable tuning voltage is applied. In addition, the oscillation frequency is variable in the low frequency range. As explained above, the oscillation frequency band is switched by applying a fixed voltage within the control voltage range and switching the capacitance value, so in the embodiment of the present invention, there is no discontinuous region where oscillation does not occur, and the frequency is continuously changed. I'm jealous of that.

Further, in this embodiment, Dl is used as a frequency control element for a high oscillation frequency region, but when looking at the resonant line side from the coupling capacitor 7, the grounding position of Dl is closer than the grounding position of D2, and the line length of the resonant line is short. The maximum oscillation frequency can be increased by making contact with the ground at the paddle position.

FIG. 3 is a circuit diagram of a voltage controlled oscillator showing a second embodiment of the present invention. In FIG. 2, parts having the same functions as those in FIG. 1 are designated by the same numbers and their explanations are omitted. In FIG. 2, 31 and 32 are capacitors, 33 is a ground shorting bias line consisting of a microstrip green path with a line length approximately equivalent to a wavelength in the oscillation frequency band, and 34 is a resistor.
It operates as a damping resistor to prevent abnormal resonance in the bias line 33. capacitor 27,
32 is selected as appropriate depending on the oscillation frequency change range, but by using a large-capacity bypass capacitor, the same operation as in Figure 1 can be performed, and there is no discontinuous region even when the oscillation frequency band is switched. This can be determined by changing the oscillation frequency. This embodiment has the advantage that, compared to FIG. 1, one ten-wavelength bias line can be removed, making the circuit simpler.

FIG. 4 shows a voltage controlled oscillator showing a third embodiment of the present invention. Components having the same functions as those in FIGS. 1 and 3 are designated by the same numbers and their explanations will be omitted. In Figure 3, 40 and 41 are variable capacitance diodes, and variable capacitance diodes 23 and 40
, 24 and 41 are cathode common connected. This embodiment has the advantage that the minimum capacitance value can be reduced without changing the rate of change in capacitance of the variable capacitor connected between the IJ tube line and the ground, and the oscillation frequency range can be increased.

〔Effect of the invention〕

As described above, according to the present invention, continuous oscillation frequency changes can be obtained by switching one oscillation frequency band by applying a fixed voltage or a frequency control voltage to the variable capacitance diode.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a voltage controlled oscillator showing the first embodiment of the present invention, Fig. 2 shows the characteristics of the embodiment shown in Fig. 1, and Fig. 3 shows the @2 embodiment of the present invention. FIG. 4 is a circuit diagram of a voltage controlled oscillator showing a third embodiment. 7...Transistor, 20.21...Resonant line. 23, 24, 40, 41...variable capacitance diodes. Figure 1 Figure 2

Claims (1)

[Claims] 1. A capacitive circuit including a plurality of variable capacitance diodes or variable capacitance diodes is connected between the microstrip resonant line and the ground, and a negative resistance circuit is connected to one end of the microstrip line, thereby creating an oscillation circuit. 1. A voltage controlled oscillator comprising: an oscillation frequency band that is switched by applying an oscillation frequency control voltage or a fixed voltage to the variable capacitance diode.