JP2910015B2 - Microwave oscillator - Google Patents

Description

The present invention relates to a variable frequency magnetostatic oscillator using YIG magnetic spin resonance, and realizes a variable frequency microwave oscillator highly stable against temperature changes. It is.

[Conventional technology]

A liquid phase epitaxially grown YIG (yttrium, iron, garnet) thin film is processed into the required shape on a GGG (gadolinium, gallium, garnet) non-magnetic substrate.
Various types of microwave devices that excite, propagate, and resonate a magnetostatic wave in a magnetic film using a microwave by a microstrip line or the like have been proposed.

Such a microwave device has very high selectivity (Q)
There is a feature that the resonance frequency can be changed widely by changing the intensity of the bias magnetic field.

As a microwave device with high selectivity, a device using spin resonance of a YIG single crystal sphere has been used conventionally,
When the ambient temperature is lowered, there is a disadvantage that the resonance point disappears, and it is necessary to prevent the temperature from being lowered by placing it in a thermostat, which has been a serious obstacle in practical use.

Further, it was difficult to process a YIG single crystal into a spherical shape, and the processing cost was high, so that the practical field was limited.

On the other hand, a magnetostatic wave device using a YIG thin film can be used even at a low temperature due to its resonance mechanism, and may be relatively inexpensive because the device is manufactured by a photolithography technique.

As described above, the magnetostatic microwave element has excellent characteristics. On the other hand, as is well known, a change in resonance frequency with respect to temperature is large, and a permanent magnet for generating a bias magnetic field is used.
Alternatively, compensation is performed by adjusting the temperature characteristics of the magnetic circuit.

[Problems to be solved by the invention]

However, as a practical problem, the types of permanent magnet materials obtained industrially are limited, and it has been extremely difficult to precisely match the temperature characteristics of both materials over a wide range. For this reason, the temperature characteristics of the magnetostatic wave element cannot be sufficiently corrected, and there has been a shortage in terms of long-term stability of the oscillation frequency.

For example, in the case of a 3 GHz band oscillator, the change in the oscillation frequency with respect to temperature near room temperature is approximately + 0.37% / ° C. To cancel this, a neodymium iron boron magnet is used as a permanent magnet with a negative temperature coefficient. In this case, the temperature coefficient of the oscillation frequency near room temperature remains at + 0.05% / ° C,
Since the temperature coefficient of the oscillation frequency and the second order term of the temperature coefficient of the magnet are different, it has been difficult to effectively compensate over a wide temperature range.

An object of the present invention is to provide a microwave oscillator that can obtain a stable oscillation frequency over a wide temperature range.

[Means for solving the problem]

In order to achieve the above object, the present invention comprises a temperature compensating means based on the temperature characteristics of the permanent magnet, and a practical means for comparing the output of the oscillator with reference to a highly stable frequency source and correcting the oscillation frequency. It is a thing.

That is, the microwave oscillator of the present invention is used to apply a bias magnetic field to a magnetostatic wave element having a magnetic thin film on a non-magnetic substrate, a yoke of a soft magnetic material, and the magnetostatic wave element, and apply a fixed magnetic field. A permanent magnet to be applied and a coil wound around the yoke for applying a variable magnetic field; means for controlling the current of the coil; and a variable frequency high frequency circuit connected to the magnetostatic wave element and oscillating a microwave. Means for compensating the temperature characteristic of the oscillation frequency of the variable frequency microwave oscillator,
The first means is a temperature compensating means based on the temperature characteristic of the saturation magnetization of the permanent magnet, and the first means is a permanent magnet whose temperature characteristic of the saturation magnetization has a negative temperature coefficient. The second means compares the frequency of the microwave reduced by the frequency divider with the frequency of the crystal oscillator by an FM demodulation circuit, feeds back a current corresponding to the error signal to the coil, and It is a means for correcting a bias magnetic field applied to the magnetic wave element, and the means for setting the oscillation frequency of the microwave oscillator is a selection of a frequency division ratio of the frequency divider.

Embodiment 1 The present invention will be described below with reference to embodiments.

FIG. 1A is a diagram showing a configuration of an embodiment according to the present invention, and FIG. 1C is a diagram showing a configuration according to a conventional technique.

Permanent magnets 2 are installed at both ends of a U-shaped yoke 3. A gap between the permanent magnets is used to form a YIG thin film formed on a GGG substrate by LPE and a strip line and a resonance structure for letting microwaves in and out. The magnetostatic wave element 1 is placed. The output of the chip is connected to the high-frequency amplifier 6, and microwave power is extracted from the output terminal of the amplifier 6. The coil 4 is for varying the oscillation frequency depending on the magnitude of the current flowing from the coil power supply 5.

In the embodiment of the present invention shown in FIG. 1A, a part of the microwave power is compared with a frequency from a reference frequency source 9 made of quartz by a frequency comparator 8 through a frequency divider 7. , A current proportional to the error signal is output from the coil power supply 5 to the coil 4.

Using a YIG thin film with a saturation magnetization of 1750 gauss at room temperature, a magnetic field of about 2800 gauss is generated in the gap by a neodymium iron boron magnet, and the oscillation frequency is adjusted to 3 GHz by further adjusting the gap distance. I made it. FIG. 2A shows a change in the oscillation frequency f according to the time t according to the prior art when the ambient temperature is raised by 10 ° C. from the room temperature.

Next, a part of the microwave output is inputted to a frequency divider 7 having a frequency division number of 1/1000, and a frequency comparator 8 which is an FM demodulator is used as a reference based on a quartz oscillator. The coil current source 5 is controlled by an error signal which is compared with the frequency from the frequency oscillator 9 and is proportional to the difference.

Similarly, FIG. 2B shows a change in the oscillation frequency f at the time t when the ambient temperature is raised by 10 ° C. from the room temperature.

FIGS. 3 (a) and 3 (b) show stable oscillation frequencies f (MHz) at each temperature when the ambient temperature T (° C.) is changed from −30 ° C. to + 60 ° C. It can be seen that the stability against temperature changes has been significantly improved.

[Embodiment 2] In the following example, as shown in FIG. 1 (b), a phase delay circuit 10 is added to the configuration of the embodiment 1 shown in FIG. And the time integral of the error signal. 2 (c) and FIG. 3 (c)
As shown in (1), the stability of the oscillation frequency f (MHz) was further improved.

It can be easily understood that the same result as in this example was obtained when a phase detector was used as a frequency comparator and a low-pass wave was coupled.

The stability to ambient temperature obtained by the present invention is:
A frequency that can be set arbitrarily within the frequency range corresponding to the achievable magnetic field of the coil and permanent magnet by selecting the frequency divider of the frequency divider, not only at the initially set frequency of 3 GHz Needless to say, this is also achieved in

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to the present invention, in a microwave oscillator using a sex magnetic wave element, the temperature stability of the oscillating frequency can be made approximately the same as that of a reference source such as crystal with a simple circuit configuration at low cost, and high reliability is achieved. And a highly stable microwave oscillator having a variable frequency can be realized.

[Brief description of the drawings]

FIGS. 1 (a) and 1 (b) show a configuration according to the present invention, and FIG.
FIG. 2 (c) is a configuration diagram according to the prior art, FIG. 2 (a) is a diagram showing a change in frequency with time with respect to a temperature change in the prior art, and FIGS. 2 (b) and 2 (c) are time diagrams of the frequency according to the present invention. FIG. 3 (a) is a diagram showing a change in frequency with respect to temperature in the prior art, and FIGS. 3 (b) and 3 (c).
FIG. 4 is a diagram showing a frequency change with respect to temperature according to the present invention. 1: magnetostatic wave element, 2: permanent magnet, 3: yoke, 4: coil, 5: coil current source, 6: high frequency oscillation circuit, 7: frequency divider, 8: frequency comparator, 9: reference frequency source, 10: Phase delay circuit

Continuing from the front page (72) Inventor Shigeru Takeda 5200 Mikajiri, Kumagaya-shi, Saitama Hitachi Metals, Ltd. 56) References JP-A-62-11303 (JP, A) JP-A-53-83560 (JP, A) JP-B-56-26163 (JP, B2) JP-B-42-9603 (JP, B1)

Claims (1)

(57) [Claims] A magnetostatic wave element having a magnetic thin film on a nonmagnetic substrate, a soft magnetic yoke, a permanent magnet used to apply a bias magnetic field to the magnetostatic wave element, and applying a fixed magnetic field; A microwave oscillator comprising: a coil wound around the yoke for applying a magnetic field; means for controlling a current of the coil; and a variable-frequency high-frequency circuit connected to the magnetostatic wave element to oscillate a microwave. The means for compensating the temperature characteristic of the oscillation frequency of the variable frequency microwave oscillator comprises first and second means, and the first means comprises a temperature compensator based on the temperature characteristic of the saturation magnetization of the permanent magnet. Means, wherein the permanent magnet is a permanent magnet having a temperature characteristic of saturation magnetization having a negative temperature coefficient, and the second means is configured to reduce a frequency of the microwave reduced by a frequency divider and a frequency of a crystal oscillator. F Comparing with the M demodulation circuit, a current corresponding to the error signal is fed back to the coil, a means for correcting the bias magnetic field applied to the magnetostatic wave element, and a means for setting the oscillation frequency of the microwave oscillator, A microwave oscillator, wherein a frequency division ratio of the frequency divider is selected.