JPS5915401B2 - Frequency variable microwave generator - Google Patents

Description

Detailed Description of the Invention The present invention provides a method for electrically varying the oscillation frequency without using a variable reactance element for varying the oscillation frequency in a microwave generator equipped with an oscillation circuit and a frequency multiplier circuit. The present invention relates to a microwave generator.

Generally, conventional microwave generators of this type include an oscillation circuit,
It is composed of three circuits: a frequency multiplication circuit and an oscillation frequency variable circuit (or frequency modulation circuit), and a variable reactance element for frequency multiplication and a variable reactance element for variable oscillation frequency are used separately.

In addition, in this device, when connecting the oscillation circuit and the frequency multiplier circuit, a circulator, an isolator, etc. It is common practice to separate both circuits in terms of impedance using a constant impedance source and a constant impedance load.

However, insertion loss occurs in these circulators, isolators, etc., and the output power decreases.

Furthermore, in this type of device, since the oscillation circuit and the frequency multiplier circuit are separated in terms of impedance, it is impossible to change the oscillation frequency by changing the impedance of the frequency multiplier element of the frequency multiplier circuit.

An object of the present invention is to provide a frequency multiplication circuit with both a frequency multiplication function and an oscillation frequency variable function in a frequency multiplier element without using a variable reactance element dedicated to changing the oscillation frequency. Another object of the present invention is to provide a variable frequency microwave generator that is inexpensive.

There are various performance requirements when using a microwave generator as a local source for microwave communication equipment.
Good oscillation frequency stability, as well as meeting telephone signals,
One of the required performances is the possibility of frequency modulation with signals such as line control signals.

In the case of microwave direct oscillation, the oscillation frequency stability is 2
fo(1±5X10-')(fo
is the oscillation frequency), and if greater stability is required, use a high stability signal (crystal controlled oscillation signal, etc.)
It is necessary to stabilize the oscillation frequency using an automatic frequency control device based on .

When using an automatic same wave number control device, a variable frequency microwave generator that can electrically change the oscillation frequency is required.

As mentioned above, as a local oscillator for microwave communication equipment, automatic frequency control is used to realize a local oscillator whose frequency can be modulated by meeting telephone numbers, line control signals, etc., and a local oscillator with good oscillation frequency stability. The present invention is used as a frequency variable microwave source when using a device.

The present invention provides a microwave generator having an oscillation circuit and a frequency multiplier circuit, wherein the oscillation circuit includes a resonant circuit that determines an oscillation frequency, and the oscillation circuit and the frequency multiplier circuit are connected via the resonant circuit. The frequency multiplier circuit includes a frequency multiplier element, the frequency multiplier element is a constituent element of the resonant circuit, and the frequency multiplier element has a frequency multiplier function as well as a function of changing the supplied bias voltage. A variable frequency microwave generator is characterized in that it has an oscillation frequency variable function that varies the oscillation frequency of the oscillation circuit. Since a variable reactance element for frequency multiplication is used for frequency multiplication and frequency variation without requiring a special variable reactance element (varactor diode, etc.), the circuit configuration is simple and the number of semiconductor elements used is smaller than that of the conventional method. Since there are fewer components, it is possible to realize a variable frequency microwave generator that is inexpensive and highly reliable.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a diagram showing an example of the configuration of a conventional frequency variable microwave generator.

Referring to FIG. 1, this device includes an oscillation circuit 1, a frequency multiplication circuit 2, and an impedance separation device 3 such as an isolator or a circulator for separating both the oscillation circuit 1 and the frequency multiplication circuit 2 in terms of impedance. and a frequency variable circuit (or modulation circuit) 4 for electrically varying the oscillation frequency, and the oscillation circuit 1 and the frequency multiplier circuit 2 are connected via an impedance separation device 3.

The oscillation circuit 1 includes a transistor 5 as an oscillation active element,
and a resonator 6 that determines its oscillation frequency.

The frequency multiplier circuit 2 includes a variable reactance element 7 for frequency multiplication, and its output power is taken out from a terminal 11 as the output of the device.

The variable frequency circuit 4 is coupled to a resonator 6 that determines the oscillation frequency of the oscillation circuit 1, and includes a variable reactance element 8, a modulation signal input terminal 9, and a DC input terminal 10 for automatic frequency control.
It is equipped with

In this conventional device, since the oscillation circuit 1 and the frequency multiplier circuit 2 are connected via the impedance separation device 3, the oscillation frequency of the oscillation circuit 1 changes due to the input impedance fluctuation of the frequency multiplier circuit 2. There is no fluctuation in power, etc., and stable oscillation operation is performed.

However, it is impossible to change the oscillation frequency of the oscillation circuit 1 using the reactance change of the frequency multiplication variable reactance element 7.

Therefore, in this type of device, as shown in FIG. 1, in order to electrically vary the oscillation frequency of the oscillation circuit 1, a variable reactance element 8 for varying the oscillation frequency is required. It is connected to a resonator 6 that determines the oscillation frequency of the circuit 1, and is configured to change the resonant frequency of the resonator 6 by changing the reactance of the variable reactance element 8, thereby making the oscillation frequency variable.

In the conventional configuration shown in FIG. 1, in order to use the impedance separation device 3, a variable reactance element for frequency multiplication and a variable reactance element for variable oscillation frequency must be used separately, and an isolator is used as the impedance separation device. , circulators, etc. are used,
This is expensive.

Additionally, varactor diodes are mainly used as variable reactance elements, but these are also expensive.

Furthermore, since a semiconductor element dedicated to this function is required for frequency variation, the circuit configuration becomes complicated.

FIG. 2 is a diagram showing an embodiment of the variable frequency microwave generator according to the present invention, and parts having the same functions as those in FIG. 1 are designated by the same numbers as in FIG. 1.

Referring to FIG. 2, this embodiment has an oscillation circuit 1 and a frequency multiplier circuit 2, and the oscillation circuit 1 includes a resonator 6 that substantially determines the oscillation frequency.
and the frequency multiplier circuit 2 are directly coupled.

The resonator 6 is composed of a coaxial resonator with one end short-circuited and the other end open.
is provided, and the base of the oscillation transistor 5 is connected to this.

Further, another coupler 15 provided close to the center conductor is connected to the anode of the frequency multiplication varactor diode 7.

This connection point is connected to terminal 9 via DC blocking capacitor 11.
connected to.

Terminal 9 is a modulation signal input terminal when it is necessary to frequency modulate a meeting telephone signal, line control signal, or the like.

Furthermore, the connection point between 15 and 7 is connected to the terminal 10 via an AC blocking resistor 18.

A terminal 10 is a terminal for supplying a bias voltage to the varactor diode 7, and a control DC voltage for automatic frequency control is connected to this terminal.

Furthermore, when not used in combination with an automatic frequency control device, a constant DC voltage may be supplied to the terminal 10 to operate the varactor diode in a fixed bias manner.

Furthermore, it is also possible to ground the terminal 10 and operate the varactor diode in a self-excited bias manner using the resistor 18.

The connection point between the varactor diode 7 and the coupler 15 is further connected to the output terminal 11 through an output impedance matching circuit 16.

Feedback capacitors 12 and 13 are connected between the pace and emitter of the transistor 5 and between the collector and emitter, respectively, to form an oscillation circuit.

These capacitors include the base of transistor 5 and
The emitter-to-emitter capacitance and the collector-to-emitter capacitance may be used respectively.

Furthermore, the resonator 6 may be constructed of a cylindrical cavity resonator, a square cavity resonator, a helical resonator, or the like.

The oscillation circuit is not limited to the Colpitts type shown in Figure 2, but other oscillation circuits such as the Bartley type may also be used, and the oscillation active element is not limited to transistors, but two-terminal active elements such as Gunn diodes and Inbat diodes can also be used. An oscillation circuit may be configured using the same.

Furthermore, the multiplier varactor diode is not limited to being connected in parallel with the circuit as shown in FIG. 2, but can also be configured to be connected in series with the circuit.

In FIG. 2, a resonator 6 that determines the oscillation frequency of the oscillation circuit and a frequency multiplication varactor diode 7 are coupled by a coupler 15, and the impedance exhibited by the frequency multiplication varactor diode 7 is The varactor diode, which is a constituent element that determines the resonance frequency of the device, is a variable capacitance element, and when the bias voltage is changed, the capacitance value it exhibits changes.

Therefore, when the bias voltage of the frequency multiplication varactor diode T is changed, the capacitance value exhibited by the varactor diode 1 is changed.

Since the capacitance exhibited by the varactor diode 1 is one component that determines the resonant frequency of the resonator 6, when the capacitance value exhibited by the varactor diode 1 changes, the resonant frequency of the resonator 6 changes.

Since the oscillation frequency of the oscillation circuit is approximately equal to the resonant frequency of the resonator 6, if the resonant frequency of the resonator 6 changes, the oscillation frequency of the oscillator will change.

As described above, by changing the bias voltage of the frequency multiplication varactor diode 7, the oscillation frequency of the oscillator can be changed.

FIG. 3 shows a linear example of the variable frequency microwave generator obtained by the present invention, where the horizontal axis represents the bias voltage value of the frequency multiplication varactor diode, and the output power corresponding to each bias voltage and the output frequency. is taken on the vertical axis.

This actual value is obtained when the oscillation frequency is set to the 2 GHz band, the oscillation signal is multiplied by 3 using a frequency multiplication varactor diode, and the signal in the 6 GHz band is extracted as the output frequency signal.

Referring to Figure 3, both the output power and the output frequency change continuously in response to changes in the bias voltage of the varactor diode (from 0 to -10V), and the present invention makes the microwave generator stable. It turns out that it works.

The bias voltage at which the output power is maximum is approximately -6V,
The modulation sensitivity at this bias point is 3 MHz/V.

The modulation degree of meeting telephone signals etc. is usually up to 200KHz r
ms, and the modulation characteristics shown in FIG. 3 are sufficient for practical use.

Furthermore, when the characteristics shown in Fig. 3 are obtained, the oscillation frequency fluctuation due to temperature change of the variable frequency microwave generator is 50%.
0 KHz/25°C, and when the oscillation frequency is stabilized in combination with an automatic frequency control device, the bias voltage control range is about 0.3 V since the modulation sensitivity is 3 MHz/V, and the resulting output level fluctuation is Since it is 0.1 dB or less, it is sufficiently usable for practical use.

As is clear from the above description, according to the present invention, there is no need for a special variable reactance element to change the oscillation frequency, and the variable reactance element for frequency multiplication has a frequency multiplication function and an oscillation frequency variable function. It is possible to provide a variable frequency microwave generator that can have two functions at the same time and has a simple circuit configuration.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an example of a conventional frequency variable microwave generator, Fig. 2 is a block diagram showing an embodiment of a frequency variable microwave generator according to the present invention, and Fig. 3 is a block diagram showing an example of a variable frequency microwave generator according to the present invention. FIG. 3 is a diagram showing output level and output frequency characteristics. In addition, each reference numeral in the figure is as follows. 1: Oscillation circuit, 2: Frequency multiplier circuit, 3: Impedance separation device, 4: Frequency variable circuit, 5: Transistor, 6: Resonator, 7, 8: Variable reactance element, 9: Modulation signal input terminal, 10: DC input terminal for automatic frequency side leg, 11:
Output terminal, 12.13, 17, 19: Capacitor, 14
゜15: Connector, 16: Output impedance matching circuit,
18: Resistor, 6a: Center conductor.

Claims (1)

[Claims] 1. In a microwave generator having an oscillation circuit and a frequency multiplier circuit, the oscillation circuit includes a resonant circuit that determines an oscillation frequency, and the oscillation circuit and the frequency multiplier circuit are connected via the resonant circuit, The frequency multiplication circuit includes a frequency multiplication element, and the frequency multiplication element is a constituent element of the resonant circuit, and the frequency multiplication element has a frequency multiplication function as well as a function corresponding to changes in the supplied bias voltage. A variable frequency microwave generator characterized by having an oscillation frequency variable function that varies the oscillation frequency of the oscillation circuit.