JPS6231205A - Local oscillator - Google Patents

Abstract

PURPOSE:To adjust oscillation frequency and to suppress drift by forming an oscillation circuit using a dielectric resonator, a frequency adjusting circuit connected to the resonator, a terminal for inputting a voltage detecting the variation of the frequency to a part of the adjusting circuit, and a circuit for connecting a temperature compensating circuit to constitute the titled device. CONSTITUTION:The oscillation circuit 21 uses the dielectric resonator 26. The AFC circuit 22 has a current mirror type output circuit and an AFC center voltage is applied to its output terminal on the basis of the division of resistors 31, 32. A variable resistor is used as the resistor 32, a voltage is impressed to a variable capacitor diode 27 through the a resistor 30 to adjust the oscillation frequency and the voltage is also impressed to the anode side of the diode 27. On the other hand, a temperature compensating control voltage is impressed from the temperature compensating circuit 23 to the diode 27 side through a resistor 29. Even if a signal input is low and the AFC circuit 22 is not actuated, the device can be prevented from remarkable variation of oscillation frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to double super one-way tuners, CAT
This invention relates to a local oscillator used as a fixed local oscillator of a V converter.

Background of the Invention In recent years, systems using the SOO~1000 band have begun to be widely used for mobile communications such as car phones, and are used as local oscillators for these communication devices. It is conceivable to use a coaxial resonator using a dielectric ceramic as a fixed local oscillator for a double super one-way tuner suitable for this purpose.

As a conventional technology, for example, "National Technical V.
Boat, VO531, NO2, APR111985J
There is.

Hereinafter, a conventional local oscillation device as described above will be explained with reference to the drawings.

FIG. 8 shows a local oscillation device using a conventional coaxial resonator. In Fig. 8, 1 is a coaxial resonator using dielectric ceramic, 2 is a coupling capacitor between the coaxial resonator 1 and the oscillation circuit, 3 is a coupling capacitor between the coaxial resonator 1 and the varicap diode 4, and 4 is the oscillation frequency. Varicap diode for variable, 5 is oscillation transistor, 6
, 7゜9 is a return capacitor, 8 is a capacitor for grounding the base, 10 is a bypass capacitor, 11-1
4 is a resistor for supplying power to or biasing the transistor 5; 15 is a resistor for supplying voltage to the varicap diode 4;

The operation of the oscillation device configured as described above will be explained below.

This conventional example has a configuration of a base-grounded Clapp oscillation circuit, and numeral 1 is a λ/4 type coaxial resonator, which utilizes dielectricity (L component) in the vicinity of the concentric point. FIG. 7 shows the basic circuit of the Clapp oscillation circuit, and its oscillation frequency is expressed as follows.

In addition, a varicap diode 4 is connected to the coaxial resonator 1 in parallel.
is added, and its capacitance value is changed by a control voltage from point A in FIG. 8, and the resonant frequency of the resonator is equivalently changed to control the oscillation frequency. Also, the oscillation output is taken out from point B.

Problems to be Solved by the Invention However, in the case of the above configuration, as shown in equation (1), there are capacitors 2.6 and 7.9 in Fig. 8 as elements that determine the oscillation frequency. The change in oscillation frequency due to temperature change is greatly influenced by the temperature characteristics of the capacitor. Also, the coaxial resonator 1 itself has N10ppm/'C
However, for the entire oscillator including C, the curve has a width of several feet, so even if temperature compensation is performed, there will be a frequency error corresponding to the width. I'm going to go out.

Therefore, in general, when used in communication equipment, a frequency synthesizer method or the like is used to apply the control voltage to point A and control the oscillation frequency to be kept constant. However, in the case of a double super one-way tuner or converter, the voltage controlled by the frequency synthesizer is generally used for the first local oscillator (a local oscillator that varies depending on the input frequency), so the voltage controlled by the frequency synthesizer is generally used for the second local oscillator. The problem was that it could not be used for fixed local oscillators.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a device that can adjust the oscillation frequency and at the same time suppress the drift of the oscillation frequency.

Means for Solving the Problems In order to achieve the above object, the local oscillation device of the present invention has the following features:
An oscillation circuit using a dielectric resonator, a frequency adjustment circuit connected to the resonator, a terminal for inputting a voltage whose frequency fluctuation is detected by a frequency control device (hereinafter abbreviated as AFC) to a part of the circuit, and a temperature control circuit. It is constructed by providing a circuit for connecting a compensation circuit.

Effects The present invention has the above-described configuration so that an oscillator using a dielectric resonator has a frequency adjustment function, a control function for suppressing fluctuations, and a temperature characteristic compensation function at the same time, and uses a method such as a frequency synthesizer. This makes it possible to construct a simple and inexpensive oscillation device.

Embodiment Hereinafter, a local oscillation device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a local oscillation device in one embodiment of the present invention.

In FIG. 1, 21 is an oscillation circuit, 22 is an AFC circuit,
23 is a temperature compensation circuit, 24.25 is a coupling capacitor, 2
6 is a coaxial resonator using a dielectric, 27 is a varicap diode, 28 is a DC cut capacitor, 29.30 is a resistor for applying voltage to the varicap diode 27, and 31.32 is for determining the AFC center voltage. resistance. The resistor 32 is made up of a variable resistor.

The operation of the local oscillator device configured as described above will be described below with reference to FIGS. 1 to 3.

In FIG. 1, the oscillation circuit 21 is, for example, a Colpitts type oscillation circuit as shown in the conventional example. Also, AFC circuit 2
2 is an AFC circuit having a current mirror type output circuit, and a voltage is applied to the output terminal of a tube diode 27 of 31.32, and at the same time, the oscillation frequency is adjusted, and at the same time, the voltage is used as the AFCO center voltage and is used as a ripple cap. This is applied to the anode side of the diode 27. On the other hand, a control voltage for temperature compensation is applied to the varicap diode side via a resistor 29.

Next, the AFC circuit 22 of FIG. The blocks of the temperature compensation circuit 23 will be explained in detail. First, FIG. 4 is a block diagram of a system related to the present oscillation device. In FIG. 4, a mixer 51 mixes the input signal with the oscillation output from the local oscillation device 54, and outputs an intermediate frequency signal having a frequency that is the difference between the two.

This intermediate frequency signal is amplified by an intermediate frequency amplifier 62. The intermediate frequency signal taken out from a part of the intermediate frequency amplifier 52 is input to the AFC circuit 53, which detects deviation from the original intermediate frequency and supplies the detected voltage to the local oscillator S4.

Next, the operation of the AFC circuit 53 will be explained using FIG. 5. In Fig. 5, B is a curve showing AFC characteristics;
A indicates the controlled voltage. For example, if the intermediate frequency signal shifts to a higher side like fl due to a shift in the oscillation frequency,
The AFC operation pulls the frequency to f2. Therefore, the voltage characteristic of A must have a slope in the direction of increasing the intermediate frequency as the voltage is increased. Therefore, if the local oscillation frequency is set lower than the input signal frequency by the intermediate frequency, the change in the local oscillation frequency will be such that as the AFC control voltage increases, the frequency decreases. must be configured.

Next, an example of the AFC output circuit will be explained using FIG. 6. In Fig. 6, 61 indicates a part of the AFC detection circuit, terminals A and H carry switching carrier signals of opposite phases, and terminals C and DK carry carrier signals whose phase is shifted by 90°C from each other. Each signal is input to the double-balanced differential amplifier to form an AFC detection circuit. Further, the output circuit constitutes a current mirror circuit by transistors 62 to 70 and resistors 71 to 77, and the DC potential at point E, which is the AFC output, can be set externally. That is, due to the mirror circuit, the collector current of transistor 62 becomes the collector current of transistor 67. equals and more tigers.

It is equal to the collector current I3 of the transistor 69. On the other hand, the collector current I4 of the transistor 64 is
is equal to the collector current I5 of . Therefore, if the differential amplifier block 61 is perfectly balanced, 11=I. Therefore, I3=E, and even if an external circuit is connected from point E, there is no exchange of current with the outside. Therefore, D at point E
The C potential, that is, the AFCO center voltage can be freely set.

The coaxial resonator 26 is equivalently considered to be a parallel resonance of LC, and therefore, as the parallel capacitance due to the varicap diode 27 increases, the oscillation frequency changes to a lower side. Therefore, if the connection is made as shown in Figure 1, as described above (as the AFC voltage increases, the capacitance of the varicap diode 27 increases, the oscillation frequency decreases, and therefore the intermediate frequency increases, as shown in Figure 6A). You can get a lot of changes.

Next, the temperature compensation circuit 23 will be explained. Regarding the temperature characteristics of the dielectric resonator itself, as the temperature of the resonator itself increases, the resonant frequency increases, and the change is linear at about 1° to 20 ppm/°C. As a means to compensate for this, the second
If we take advantage of the temperature change in vBE of the transistor amplifier as shown in the figure and take it out from the collector, the change in output voltage with respect to temperature will be as shown in Figure 3. In FIG. 2, the temperature at which the voltage is changed can be set by resistors 41 and 42, and the voltage change with respect to temperature can be adjusted by resistors 43 and 44.

Therefore, if this voltage is supplied to the cathode side of the varicap diode 27, the voltage applied to both ends of the varicap diode 27 will decrease as the temperature rises.
Since the capacity increases, it works in the direction of lowering the number of waves for support. In this way, frequency fluctuations with respect to temperature of the dielectric resonator 26 can be compensated for.

As described above, according to this embodiment, the varicap diode 27 is connected to the oscillator using the dielectric resonator 26,
The oscillation frequency can be adjusted by connecting the output end of the AFC to the anode side, applying the AFCO center voltage to the same point by dividing the resistors, and making one of the resistors a variable resistor. Furthermore, by applying a voltage for temperature compensation to the cathode side of the varicap diode 27, even if the signal input is weak (AFC circuit 2
2 stops operating, extreme fluctuations in the oscillation frequency can be avoided and stable oscillation can be maintained.

Effects of the Invention As described above, according to the present invention, in a local oscillation device using a dielectric resonator, the control function by AFC, the frequency adjustment function by a variable resistor, and the temperature compensation function are all performed by a single varicap diode anode. - can be connected between the cathode and the oscillation frequency to stabilize the oscillation frequency. Moreover, it can be constructed easily and inexpensively, and its practical effects are outstanding.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a local oscillator according to an embodiment of the present invention, Fig. 2 is a circuit diagram of an example of its temperature compensation circuit, Fig. 3 is a characteristic diagram of its temperature compensation, and Fig. 4 is a diagram of its temperature compensation circuit. A block diagram of the related system, Fig. 5 is a characteristic diagram of AFC, Fig. 6 is a circuit diagram showing one embodiment of the AFC output circuit, Fig. 7 is a basic circuit diagram of a Clapp oscillator, and Fig. 8 is a conventional circuit diagram. FIG. 1 is a circuit diagram showing an example of a local oscillation device using a coaxial resonator. 1...Oscillation circuit, 2...AFC circuit,
3... Temperature compensation circuit, 4, 5... Coupling capacitor, 6... Dielectric resonator, 7...
...Varicap diode, 8...DC cut capacitor, 9 to 11 resistor, 12...variable resistor. Name of agent: Patent attorney Toshio Nakao and 1 other person21
-...Oscillation circuit z (25...Mixed capacitor Fig. 2 Fig. 30 Fig. 4 Fig. 5■ Fig. 6 Fig. 7 Fig. 8)

Claims (2)

[Claims] (1) An oscillator using a dielectric coaxial resonator, a varicap diode whose anode side is connected to the center conductor of the resonator through a capacitor, and an oscillator connected to the anode side of the varicap diode directly or through a first resistor. Connect the output end of the frequency control circuit (AFC), apply voltage from the power supply to this connection point by resistor division, make one of the division resistors variable, and ground the cathode side of the varicap diode in an alternating current manner. and a local oscillation device connected to a temperature compensation circuit via a second resistor. (2) The local oscillation device according to claim 1, characterized in that a current mirror type output circuit is connected as the AFC output circuit.