JPH052434U - Surface acoustic wave oscillator - Google Patents

Abstract

(57) [Summary] [Purpose] To obtain a surface acoustic wave oscillator in which fluctuations in the oscillation frequency due to environmental changes such as ambient temperature and humidity and fluctuations in the oscillation frequency due to changes over time are small. [Configuration] A frequency discriminator 7 is connected to the power distributor 3.
A temperature controller 8 is connected to the frequency discriminator 7. A heater 9 is connected to the temperature controller 8.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a method of constructing a surface acoustic wave oscillation with a small fluctuation in oscillation frequency.

[0002]

[Prior Art]

 FIG. 4 is a diagram showing a configuration of a conventional surface acoustic wave oscillator. In the figure, 1 is an elastic surface wave element, 2 is an amplifier, 3 is a power distributor, 4 is a phase shifter, and 1 to 4 are provided. A positive feedback circuit is made up of the components. Further, 5 is a buffer amplifier connected to the power distributor 3, 6 is an output terminal of the oscillator, and 9 is a heater for keeping the temperature of the surface acoustic wave element constant.

Next, the operation will be described. The gain of the amplifier 2 is adjusted so that the total gain of the positive feedback circuit composed of the surface acoustic wave element 1, the amplifier 2, the power divider 3, and the phase shifter 4 becomes 1 or more. If the phase shift amount of the phase shifter 4 is adjusted so that the total phase shift amount of the positive feedback circuit becomes an integral multiple of 360 degrees, this positive feedback circuit oscillates at the resonance frequency of the surface acoustic wave element. A part of this oscillation output is taken out from the power distributor 3 and output to the output terminal 6 through the buffer amplifier 5. Further, when the temperature of the surface acoustic wave element 1 changes, the resonance frequency changes, and therefore the oscillation frequency changes, so that the temperature of the surface acoustic wave element 1 is maintained by the heater 9.

[0004]

[Problems to be solved by the device]

 The conventional surface acoustic wave oscillator is configured as described above, but there are problems such as fluctuations in the oscillation frequency due to environmental changes such as ambient temperature and humidity, and changes over time in the oscillation frequency.

The present invention has been made in order to solve the above problems, and it is possible to reduce the fluctuation of the oscillation frequency with respect to the change of the surrounding environment and to reduce the change of the oscillation frequency with time. The objective is to obtain a surface acoustic wave oscillator that can be used.

[0006]

[Means for Solving the Problems]

 The surface acoustic wave oscillator according to the present invention detects a part of the oscillation output by the frequency discriminator, controls the heater temperature by the detection output, and controls the resonance frequency of the surface acoustic wave element.

Further, the phase shift amount of the phase shifter is controlled by the detection output of the frequency discriminator.

[0008]

[Action]

 When the oscillating frequency of the surface acoustic wave oscillator configured as described above fluctuates, the heater temperature changes depending on the detection output of the frequency discriminator. At this time, if the heater temperature is controlled so that the resonance frequency of the surface acoustic wave element changes in the direction in which the fluctuation of the oscillation frequency is canceled, the fluctuation of the oscillation frequency becomes small.

Further, if the phase shift amount of the phase shifter is controlled by the detection output of the frequency discriminator in such a direction as to cancel the fluctuation of the oscillation frequency, the fluctuation of the oscillation frequency becomes small.

[0010]

【Example】

 Example 1. An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 1 to 6 are the same as those of the conventional one shown in FIG. 7 is a frequency discriminator connected to the output of 1 of the power distributor 3, 8 is a temperature controller for converting the detection output of the frequency discriminator 7 into a temperature control signal of the heater, and 9 is a temperature controller 8. It is a heater whose temperature changes according to a signal.

Next, the operation will be described. In the following description, a surface acoustic wave oscillator in which each component has the characteristics shown in FIG. 2 will be taken as an example. 2a shows the characteristic of the frequency discriminator 7, FIG. 2b shows the characteristic of the temperature controller 8, FIG. 2c shows the characteristic of the heater 9, and FIG. 2d shows the temperature characteristic of the resonance frequency of the surface acoustic wave element 1.

When the oscillation frequency of the surface acoustic wave oscillator is the target frequency f _D , the frequency discriminator 7 and the temperature controller 7 are controlled so that the characteristic of each component becomes the value of point A in FIGS. 2a to 2d. Adjust 8.

Now, suppose that the oscillation frequency of the surface acoustic wave oscillator is higher than the target frequency (for example, when f _D changes to f _U in FIG. 2e). At this time, the detection output of the frequency discriminator 7 increases and the control voltage of the temperature controller 8 decreases. Therefore, the temperature of the heater 9 drops and the resonance frequency of the surface acoustic wave element 1 drops. The state at this time is shown by point B in FIGS. 2a to 2d.

When the oscillation frequency of the surface acoustic wave oscillator becomes lower than the target frequency (f _{L in} FIG. 2e), the operation reverse to the above is performed. The state at this time is shown by point C in FIGS. 2a to 2d.

The frequency discriminator 7, the temperature controller 8, and the heater 9 in the present invention change the resonance frequency of the surface acoustic wave element 1 to the oscillation frequency when the oscillation frequency of the surface acoustic wave oscillator fluctuates as described above. Operates in the opposite direction of the fluctuation of. Therefore, the variation of the oscillation frequency of the surface acoustic wave oscillator and the variation of the resonance frequency of the surface acoustic wave element 1 are

[0016]

[Equation 1]

If the relationship of is satisfied, the fluctuation of the oscillation frequency is canceled and the fluctuation of the oscillation frequency can be reduced.

Example 2. FIG. 3 shows another embodiment of the present invention. In FIG. 3, 4 is a phase shifter capable of controlling the phase shift amount from the outside, and 10 is a phase shift amount for converting the detection output of the frequency discriminator 7 into a signal for controlling the phase shift amount of the phase shifter 4. It is a controller. Others are the same as the conventional ones.

The characteristics of the frequency discriminator 7, the phase shift amount controller 10, the phase shifter 4, and the surface acoustic wave element 1 in the surface acoustic wave oscillator having the configuration of FIG. 3 are shown in FIGS. 4a to 4d, respectively.

In the embodiment of FIG. 3, each component operates as shown in FIGS. 4a to 4d with respect to the fluctuation of the oscillation frequency as shown in FIG. 4e. Therefore, the fluctuation of the oscillation frequency can be reduced as in the first embodiment.

[0021]

[Effect of the device]

 As described above, according to the present invention, the fluctuation of the oscillation frequency is detected by the frequency discriminator, the heater temperature is controlled by the detection signal, and the resonance frequency of the elastic surface element is changed to cancel the fluctuation of the oscillation frequency. With this configuration, there is an effect that the fluctuation of the oscillation frequency can be reduced.

Further, even if the phase shift amount of the phase shifter is controlled by the detection signal of the frequency discriminator, the fluctuation of the oscillation frequency can be reduced.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a surface acoustic wave oscillator according to a first embodiment of the present invention.

FIG. 2 is a diagram showing characteristics of each component of Example 1 of the present invention.

FIG. 3 is a configuration diagram of a surface acoustic wave oscillator according to a second embodiment of the present invention.

FIG. 4 is a diagram showing characteristics of each component of Example 2 of the present invention.

FIG. 5 is a configuration diagram of a conventional surface acoustic wave oscillator.

[Explanation of symbols]

 1 surface acoustic wave element 2 amplifier 3 power distributor 4 phase shifter 5 buffer amplifier 6 output terminal 7 frequency discriminator 8 temperature controller 9 heater 10 phase shift amount controller

Claims (1)

Claims for utility model registration: 1. A surface acoustic wave device, an amplifier connected to the surface acoustic wave device, a power distributor having a plurality of output terminals and connected to the amplifier, and a power distributor of the power distributor. The phase shifter connected to the first output end and the surface acoustic wave element, the frequency discriminator connected to the second output end of the power distributor, the temperature controller connected to the frequency discriminator, A surface acoustic wave oscillator comprising a heater controlled by the temperature controller and thermally coupled to the surface acoustic wave element.