CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Phase of International Patent Application No. PCT/JP2019/032388 filed on Aug. 20, 2019, which claims priority benefit of Japanese Patent Application No. JP 2018-178376 filed in the Japan Patent Office on Sep. 25, 2018. Each of the above-referenced applications is hereby incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present technology relates to an oscillator circuit and a radio receiver, and more particularly to a technology for improving the operability of an analog tuning radio.

BACKGROUND ART

In a case of listening to a radio broadcast by use of a radio receiver, a frequency of a broadcasting station may be adjusted manually.

In this case, even if the frequency of the broadcasting station is manually adjusted, the radio broadcast may not be listened to due to a change in the temperature of the radio receiver. For example, in a case of receiving the radio broadcast for a long time, the reception sensitivity may deteriorate or the radio broadcast may not be listened to properly in the middle of the radio broadcast even though the radio broadcast can be received at first.

Here, in order to prevent the frequency from fluctuating due to a temperature characteristic of an oscillator circuit of the radio receiver, a technology for reducing a temperature fluctuation of the oscillator circuit has been studied (see, for example, Patent Document 1 and Patent Document 2).

CITATION LIST

Patent Document

Patent Document 1: Japanese Patent Application Laid-Open No. 2004-312080Patent Document 2: Japanese Patent Application Laid-Open No. 2015-527848

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

Incidentally, in a manual analog tuning radio that uses a free-run oscillator circuit without using a phase locked loop (PLL), a local oscillation frequency fluctuates due to the temperature fluctuation. In this case, the reception performance deteriorates, and it may be necessary to tune the radio again.

The present technology has been made in view of such a situation, and a main purpose thereof is to provide an oscillator circuit and a radio receiver capable of reducing a frequency fluctuation of an oscillation frequency to a small extent.

Solutions to Problems

As a result of diligent research to solve the above-described object, the present inventor has succeeded in reducing the frequency fluctuation of the oscillation frequency to a small extent, and has completed the present technology.

That is, in the present technology, first, there is provided an oscillator circuit including

an LC oscillator circuit,

an amplitude detection circuit, and

a bias generation circuit, in which

the LC oscillator circuit includes an inductor and at least one variable capacitance element,

the amplitude detection circuit detects an oscillation amplitude of the LC oscillator circuit and converts the oscillation amplitude into a DC voltage, and

the bias generation circuit compares the DC voltage with a voltage for generating a bias signal, the voltage changing on the basis of a temperature fluctuation of the bias generation circuit, calculates a difference between the DC voltage and a voltage after the change, and generates, on the basis of the difference, a bias signal that reduces a fluctuation in the oscillation amplitude, to control the oscillation amplitude.

In the oscillator circuit according to the present technology, the LC oscillator circuit may include a capacitor bank and a temperature compensation varicap,

the capacitor bank may include a MOS switch, and

the temperature compensation varicap may prevent a capacitance value of the capacitor bank from fluctuating due to a temperature fluctuation of the MOS switch. In this case, temperature dependence of the temperature compensation varicap may be different from temperature dependence of the capacitor bank.

Furthermore, the temperature compensation varicap may include a MOS varicap and,

a bias voltage may be applied to the MOS varicap to prevent the capacitance value of the capacitor bank from fluctuating.

In this case, the bias voltage may be generated by a bias circuit including a resistor and a diode.

In the oscillator circuit according to the present technology, the bias signal may be a voltage.

In the oscillator circuit according to the present technology, a cross couple of n-type MOS transistors may further be included,

sources of the cross couple of the n-type MOS transistors may be commonly connected, and a constant current source may be connected between a point where the common connection is made and a ground. In this case, each of drains of the cross couple of the n-type MOS transistors may be connected to the inductor and the variable capacitance element, and

a current value of the constant current source may be controlled to control the oscillation amplitude.

In the oscillator circuit according to the present technology, a cross couple of n-type MOS transistors may further be included,

sources of the cross couple of the n-type MOS transistors may be commonly connected, and a resistor may be connected between a point where the common connection is made and a ground. In this case, a capacitance element may be connected between the sources of the cross couple of the n-type MOS transistors.

Furthermore, in the present technology, there may be provided a radio receiver equipped with an oscillator circuit including

an LC oscillator circuit,

an amplitude detection circuit, and

a bias generation circuit, in which

the LC oscillator circuit includes an inductor and at least one variable capacitance element,

the amplitude detection circuit detects an oscillation amplitude of the LC oscillator circuit and converts the oscillation amplitude into a DC voltage, and

the bias generation circuit compares the DC voltage with a voltage for generating a bias signal, the voltage changing on the basis of a temperature fluctuation of the bias generation circuit, calculates a difference between the DC voltage and a voltage after the change, and generates, on the basis of the difference, a bias signal that reduces a fluctuation in the oscillation amplitude, to control the oscillation amplitude.

According to the present technology, it is possible to provide an oscillator circuit and a radio receiver capable of reducing the frequency fluctuation of the oscillation frequency to a small extent, so that the operability of an analog tuning radio receiver can be improved. Note that the effect of the present technology is not necessarily limited to the above effect, and may be any effect described in the present technology.

