JPH02142219A - Oscillator - Google Patents

Abstract

PURPOSE:To improve the stability of an oscillating frequency by comparing the oscillating frequency of an oscillator with a reference signal, and controlling a bias voltage which is applied to the control terminal of a positive element for oscillation, by negative feedback operation. CONSTITUTION:The oscillating frequency to be induced to a first microstrip line 2 is supplied through a capacitor 20 for direct current block to a divider 21 and a divided frequency is compared with the reference frequency of a reference oscillator 22 by a phase comparator 23. The output of the phase comparator 23 is supplied to a low-pass filter 24 and a differential signal voltage to correspond to frequency dislocation is outputted and supplied to the microstrip line 2. When the oscillating frequency is dislocated, the differential signal voltage is outputted from the low-pass filter 24 and the bias voltage of the gate in an electric field effect transistor 4 is changed in a direction to cancel the dislocation of the oscillating frequency. Thus, regardless of the temperature change or the voltage fluctuation of a power source, etc., the oscillating frequency is maintained constant and the stability is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an oscillator whose oscillation frequency is extremely stable.

(Prior Art) As a high Q oscillator, there is one using a dielectric resonator. FIG. 4 is a circuit diagram of an example of a conventional oscillator using a dielectric resonator. In FIG. 4, a dielectric resonator 1 and a first microstrip line 2 are arranged on a dielectric substrate (not shown) so as to be magnetically coupled. Further, a second microstrip line 3 is arranged so as to be orthogonal to the first microstrip line 2 and magnetically coupled to the dielectric resonator l. One end of the first microstrip line is connected to the gate as a control terminal of a field effect transistor 4 as an oscillation active element, and the other end is grounded via a resistor 5. Further, one end of the second microstrip line 3 is connected to the drain of the field effect transistor 4, and the other end is open. Furthermore, the drain of the field effect transistor 4 is connected to the power source B via the choke coil 6. The source is connected to an output terminal 8 via a DC blocking capacitor 7, and
It is grounded through a choke coil 9 and a bias resistor IO in series. The connection point between choke coil 9 and bias resistor 10 is grounded via capacitor 11.

In such a configuration, an oscillation frequency is induced in the first microstrip line 2 at a frequency that largely depends on the dielectric resonator 1, and is amplified by the field effect transistor 4,
appear in the source. Further, due to the impedance change of the field effect transistor 4 due to this frequency, the same frequency appears on the second microstrip line 3, and positive feedback is applied to the dielectric resonator 1 by magnetic field coupling. Therefore, the oscillation operation is performed at a frequency that largely depends on the dielectric resonator l. An oscillator using this dielectric resonator 1 is characterized by a high Q of the oscillation frequency, and requires sufficient selectivity and sensitivity, and a local oscillation circuit for a satellite communication transceiver that handles finely stripped radio waves. It is widely used as, etc.

(Problems to be Solved by the Invention) However, in the conventional oscillator using the dielectric resonator 1 described above, the characteristics of the dielectric resonator 1 change due to temperature changes and the bias voltage due to voltage fluctuations of the power element B. There was a problem that the oscillation frequency was shifted by one oscillation frequency due to such changes, and the stability of the oscillation frequency was poor.

By the way, as shown in FIG. 5, when the bias voltage v0 of the field effect transistor 4 is varied between +Δv1 and -Δv2, the oscillation frequency f0 becomes -Δf.

It is known that the value varies by +Δf2. This is because the depletion layer capacitance between the gate and the drain changes as the bias voltage changes, and the oscillation frequency changes due to this capacitance change.

Therefore, the inventors focused on the fluctuation of the oscillation frequency caused by the fluctuation of the bias voltage, and came up with the idea of actively utilizing this effect to improve the stability of the oscillation frequency.

An object of the present invention is to provide an oscillator with a highly stable oscillation frequency based on the above idea in order to improve the problems of the conventional oscillator.

(Means for Solving the Problems) In order to achieve such an object, the oscillator of the present invention has a dielectric resonator and a microstrip line arranged on a dielectric substrate so as to be magnetically coupled to each other, and the microstrip line In an oscillator whose one end is connected to the control terminal of the active element for oscillation, the oscillation frequency of this oscillator is compared with the reference signal,
A bias voltage control circuit is provided to control the bias voltage applied to the control terminal of the oscillation active element by a negative feedback effect.

The bias voltage control circuit divides the oscillation frequency of the oscillator using a frequency divider, compares the divided frequency with a reference frequency using a phase comparator, and passes the output from the phase comparator through a low-pass filter. The signal may be configured to be applied to the control terminal of the oscillation active element via the oscillation active element.

In addition, 5 the bias voltage control circuit converts the oscillation frequency of the oscillator by mixing it with a local oscillation frequency in a mixer, extracts a converted frequency in a predetermined band from the mixed output using a band pass filter, and further divides the frequency. The frequency is divided by a frequency generator, the divided frequency is compared with a reference frequency by a phase comparator, and the output from the phase comparator is applied to the control terminal of the excitation active element via a low-pass filter. It's okay.

(Function) When the oscillation frequency of the oscillator tries to deviate from the reference signal,
Due to the negative feedback effect of the bias voltage control circuit, the bias voltage applied to the control terminal of the oscillation active element is controlled in a direction that cancels out the deviation.

Therefore, the oscillator of the present invention has a highly stable oscillation frequency regardless of temperature changes, power supply voltage fluctuations, and the like.

If the frequency obtained by dividing the oscillation frequency is compared with the reference frequency using a phase comparator, and the difference signal voltage corresponding to the difference in frequency is obtained using a low-pass filter, the bias voltage of the oscillation active element can be easily reduced. Feedback control is possible.

In addition, if the oscillation frequency is frequency-converted and the divided frequency is compared with the reference frequency, the configuration of a circuit that handles extremely high oscillation frequencies relative to the reference frequency can be simplified, and the sensitivity to deviations in the oscillation frequency can be improved. increases, and the oscillation frequency can be maintained accurately and stably.

(Example) Hereinafter, an example of the present invention will be described with reference to FIG. FIG. 1 is a circuit diagram of an embodiment of an oscillator of the present invention using a dielectric resonator. In FIG. 1, the same members as those in FIG. 4 are given the same reference numerals and redundant explanations will be omitted.

In FIG. 1, the oscillation frequency induced in the first microstrip line 2 is applied to a frequency divider 21 via a DC blocking capacitor 20. The frequency divided by the frequency divider 21 and the reference frequency oscillated by the reference oscillator 22 are applied to a phase comparator 23 for comparison. Then, the output of the phase comparator 23 is given to a low-pass filter 24, and a difference signal voltage corresponding to the frequency shift is outputted and passed through resistors 25 and 26 to the first microstrip line 2.
given to. Note that the connection point of the resistors 25 and 26 is grounded via a capacitor 27 to smooth the differential signal voltage.

In such a configuration, if the oscillation frequency shifts due to temperature changes or power supply voltage fluctuations, the low-pass filter 24
A difference signal voltage is output from the field effect transistor 4.
The bias voltage of the gate changes. This change in bias voltage is in the direction of canceling out the shift in oscillation frequency. Due to such a negative feedback effect, the oscillation frequency is maintained constant regardless of temperature changes, voltage fluctuations of the power supply +B, etc., resulting in high stability.

FIG. 2 is a circuit diagram of another embodiment of an oscillator using the dielectric resonator of the present invention. In FIG. 2, the same members as those in FIG. 1 are given the same reference numerals and redundant explanations will be omitted.

In FIG. 2, the oscillation frequency (for example, 13.2 GH2) induced in the first microstrip line 2 is transmitted through a DC blocking capacitor 20 and then to the first amplifier 3.
The signal is amplified by 0 and applied to the mixer 31. This mixer 3
1 is given the local oscillation frequency (for example, 12.8 GH2) that has passed through the first bandpass filter 32. Then, a conversion frequency (for example, 400 MH2) within a predetermined band is extracted from the mixed output output from the mixer 31 by a second band-pass filter 33, and then the second amplifier 3
4 and is applied to the first frequency divider 21. The frequency divided by 1/8 by this first frequency divider 21 (for example, 5
0MH,) is applied to the first phase comparator 22. This first phase comparator 22 has a reference frequency (for example, 50 MHz) oscillated by a reference oscillator 23 using a crystal resonator.
is amplified by the third amplifier 35 and provided. and,
The frequency from the first frequency divider 21 and the reference frequency are compared by the first phase comparator 22, and the frequency from the first frequency divider 21 is compared with the reference frequency.
A difference signal voltage is output from the low-pass filter 24, and the bias voltage of the field effect transistor 4 is controlled by negative feedback as in the embodiment shown in FIG.

Here, the local oscillation frequency given to the mixer 31 is generated as follows. A frequency (for example, 6.25 MH2) obtained by dividing the reference frequency oscillated by the reference oscillator 23 to 1/8 by the second frequency divider 36 is applied to the second phase comparator 3.
7 is given. The output of this second phase comparator 37 is applied via a second low-pass filter 38 to a voltage controlled oscillator 39 having a free running frequency of, for example, 1.6 GH2. The frequency oscillated from this voltage controlled oscillator 39 is
The signal is amplified by the fourth amplifier 40 and provided to the third frequency divider 41. With this third frequency divider 41, the voltage controlled oscillator 39
The frequency oscillated from is divided by 1/256, and the frequency (for example, 6.25 MH2') is applied to the second phase comparator 37. Therefore, using the frequency obtained by dividing the reference frequency oscillated by the reference oscillator 23 by the second frequency divider 36 as the reference frequency, the second phase comparator 37, the second low-pass filter 3B, the voltage-controlled oscillator 39, and the second A 7-axis rotor loop (PLL) by a frequency divider 41 of 3
is configured. Further, the frequency oscillated by the voltage controlled oscillator 39 is amplified by the fifth amplifier 42, and further multiplied by 8 by the multiplier 43 (for example, 12.8 GH).
is applied to the mixer 31 as a local oscillation frequency via the first bandpass filter 32.

In this configuration, the oscillation frequency is frequency-converted to a lower frequency by the superheterodyne method, frequency-divided, and compared with the reference frequency, so that it is possible to easily control an oscillation frequency that is extremely high with respect to the reference frequency. Moreover, the oscillation frequency can be treated as a low frequency by frequency conversion, and the circuit configuration is easy. The local oscillation frequency for frequency conversion is extremely stable because it is controlled by a phase-locked loop that divides the reference frequency oscillated from the reference oscillator 23 and uses it as a reference frequency. Therefore, in the frequency converted by the mixer 31 and extracted by the second band-pass filter 33, the deviation of the oscillation frequency appears accurately, and the sensitivity to the deviation increases greatly. It can be maintained constant, and - layer stability is improved.

FIG. 3 is a circuit diagram of still another embodiment of the oscillator of the present invention using a dielectric resonator, in which a transistor is used as an active element for one oscillation.

In FIG. 3, circuit members that are the same as those in FIG. 1 are given the same reference numerals and redundant explanations will be omitted.

In FIG. 3, one end of the first microstrip line 2 is connected to the base of the transistor 50, one end of the second microstrip line 3 is connected to the collector, and the emitter is connected to the output terminal 8 via the capacitor 6. It is also grounded through the choke coil 9 and the resistor lO in series. Further, the other end of the first microstrip line 2 is grounded via resistors 51 and 52 in series, and the connection point between these resistors 51 and 52 is grounded via a capacitor 53. Furthermore, the other end of the first microstrip line 2 is connected to a frequency divider 21 via a capacitor 20. Then, the differential voltage from the low-pass filter 24 is applied to the connection point between the resistors 51 and 52 between the resistor 25 and the capacitor 27.
The signal is smoothed by the buffer amplifier 54 and then provided via the buffer amplifier 54. This M offset amplifier 54 has an appropriate offset voltage,
A bias voltage applied to the base of transistor 50 is formed by changes in the offset voltage and the difference signal voltage.

In this configuration, a change in the bias voltage applied to the base of the transistor 50 changes the collector capacitance between the base and the collector, thereby changing the oscillation frequency. Then, a difference signal voltage is output in response to the deviation in the oscillation frequency, the bias voltage is changed, and the oscillation frequency is maintained constant due to the negative feedback effect.

In the above embodiment, the bias voltage control circuit is configured to compare the oscillation frequency and the reference frequency, but the present invention is not limited to this. The bias voltage may be controlled by negative feedback by comparing this voltage signal with a reference voltage as a reference signal. It goes without saying that the oscillation frequency appearing at the output terminal of the oscillation active element 4.50 may be compared with a reference frequency.

(Effects of the Invention) Since the oscillator of the present invention is configured as described above, it produces the effects described below.

First, due to the negative feedback effect of the bias voltage control circuit, the bias voltage at the control terminal of the oscillation active element is controlled in a direction that cancels out the deviation in the oscillation frequency, so oscillation occurs regardless of temperature changes or power supply voltage fluctuations. Frequency is kept constant and stability is high.

If the oscillation frequency and the reference frequency are compared with a phase comparator to obtain a difference signal voltage corresponding to the frequency deviation, the bias voltage of the oscillation active element can be easily controlled according to the oscillation frequency deviation, and the dielectric A circuit including a resonator and an oscillation active element functions as a voltage-controlled oscillator, forming a so-called phase-locked loop, resulting in extremely high stability of the oscillation frequency.

Furthermore, if the oscillation frequency is frequency-converted and the divided frequency is compared with a reference frequency, it is possible to easily control an oscillation frequency that is extremely high compared to the reference frequency. Furthermore, the sensitivity to deviations in the oscillation frequency is good, and the stability of the oscillation frequency can be improved accordingly. Furthermore, since the oscillation frequency is converted to a lower frequency and handled, the circuit configuration is easier, which is extremely useful in terms of implementation.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of one embodiment of the oscillator of the present invention using a dielectric resonator, and FIG. 2 is a circuit diagram of another embodiment of the oscillator using the dielectric resonator of the present invention. FIG. 3 is a circuit diagram of still another embodiment of the oscillator of the present invention using a dielectric resonator, in which a transistor is used as the active element for oscillation, and FIG. FIG. 5 is a circuit diagram of an example of a conventional oscillator using a body resonator, and FIG. 5 shows that by varying the bias voltage of a field effect transistor,
FIG. 3 is a characteristic diagram showing that the oscillation frequency fluctuates. 1: Dielectric resonator. 2: First microstrip line, 4: Field effect transistor, 21: Frequency divider, 22: Phase comparator, 23: Reference oscillator, 24: Low-pass filter, 31: Mixer. 50: Transistor. Patent applicant Yokoo Seisakusho Co., Ltd. Agent Patent attorney Tetsuo Moriyama Bias Dongfeng

Claims (3)

[Claims] (1) In an oscillator in which a dielectric resonator and a microstrip line are magnetically coupled on a dielectric substrate, and one end of the microstrip line is connected to a control terminal of an oscillation active element, the oscillation frequency of this oscillator is 1. An oscillator comprising: a bias voltage control circuit for comparing the bias voltage with a reference signal and controlling the bias voltage applied to the control terminal of the oscillation active element by a negative feedback effect. (2) The bias voltage control circuit divides the oscillation frequency of the oscillator using a frequency divider, compares the divided frequency with a reference frequency using a phase comparator, and outputs the output from the phase comparator to a low-pass filter. 2. The oscillator according to claim 1, wherein the oscillator is configured to be applied to the control terminal of the oscillation active element via the oscillator. (3) The bias voltage control circuit converts the oscillation frequency of the oscillator by mixing it with a local oscillation frequency using a mixer, extracts a converted frequency in a predetermined band from the mixed output using a bandpass filter, and further The frequency is divided by a frequency divider, the divided frequency is compared with a reference frequency by a phase comparator, and the output from the phase comparator is applied to the control terminal of the oscillation active element via a low-pass filter. The oscillator according to claim 1, characterized in that: