FM signal receiver and wireless communications device using same

An FM signal receiver, comprising:

• a differential-type bandpass filter for selecting a received burst signal;
• a differential-type frequency-demodulation circuit for converting the burst signal selected by the bandpass filter from a frequency to a voltage;
• a differential-input, single-output amplifier for amplifying the burst signal converted from the frequency to the voltage by the frequency-demodulation circuit;
• an analog-to-digital converter circuit for converting to digital the burst signal fed via the amplifier for demodulation;
• a control circuit for adjusting frequency characteristics of the differential-type bandpass filter and the differential-type frequency-demodulation circuit through an identical control signal immediately before a receiving operation;
• a reference voltage source for generating a reference voltage;
• a switch for switching an input to the amplifier between an output signal of the differential-type frequency-demodulation circuit and the reference voltage fed from the reference voltage source;
• and
• a memory for recording an output of the analog-to-digital converter circuit,
• wherein the control circuit, in an adjusting operation, switches the switch to the reference voltage so as to record the output of the analog-to-digital converter circuit made in response to application of the reference voltage in the memory;
• and subsequently switches the switch to the frequency-demodulation circuit so as to generate the control signal based on the output value of the analog-to-digital converter circuit as recorded in the memory and adjust the frequency characteristics of the bandpass filter and the frequency-demodulation circuit through the identical control signal.

A wireless communications device, including an FM signal receiver comprising:

• a bandpass filter for selecting a received burst signal;
• a frequency-demodulation circuit for converting the burst signal selected by the bandpass filter from a frequency to a voltage;
• an amplifier for amplifying the burst signal converted from the frequency to the voltage by the frequency-demodulation circuit;
• an analog-to-digital converter circuit for converting to digital the burst signal fed via the amplifier for demodulation;
• a control circuit for adjusting frequency characteristics of the bandpass filter and the frequency-demodulation circuit through an identical control signal immediately before a receiving operation;
• and
• a shorting circuit provided between input and output terminals of the amplifier, the shorting circuit being opened during the receiving operation and shorted during an adjusting operation,
• wherein said wireless communications device further includes a high frequency amplifier, a mixer, an oscillator, an analog-to-digital converter, a digital-to-analog converter, and a logic circuit, and uses the digital-to-analog converter as a reference signal generator circuit.

A wireless communications device, including an FM signal receiver comprising:

• a differential-type bandpass filter for selecting a received burst signal;
• a differential-type frequency-demodulation circuit for converting the burst signal selected by the bandpass filter from a frequency to a voltage;
• a differential-input, single-output amplifier for amplifying the burst signal converted from the frequency to the voltage by the frequency-demodulation circuit;
• an analog-to-digital converter circuit for converting to digital the burst signal fed via the amplifier for demodulation;
• a control circuit for adjusting frequency characteristics of the differential-type bandpass filter and the differential-type frequency-demodulation circuit through an identical control signal immediately before a receiving operation;
• a reference voltage source for generating a reference voltage;
• a switch for switching an input to the amplifier between an output signal of the differential-type frequency-demodulation circuit and the reference voltage fed from the reference voltage source;
• and
• a memory for recording an output of the analog-to-digital converter circuit,
• wherein the control circuit, in an adjusting operation, switches the switch to the reference voltage so as to record the output of the analog-to-digital converter circuit made in response to application of the reference voltage in the memory;
• and subsequently switches the switch to the frequency-demodulation circuit so as to generate the control signal based on the output value of the analog-to-digital converter circuit as recorded in the memory and adjust the frequency characteristics of the bandpass filter and the frequency-demodulation circuit through the identical control signal,
• wherein said wireless communications device further includes a high frequency amplifier, a mixer, an oscillator, an analog-to-digital converter, a digital-to-analog converter, and a logic circuit, and uses the digital-to-analog converter as a reference signal generator circuit.