Rohm Co., Ltd.

Rf Chips Technology Inc.

Hiroyuki Ashida

Yoshikazu Shimada

Tamotsu Suzuki

Yasuhiko Tsuji

Sadao Igarashi

Masatoshi Tsuji

Katsuya Ogura

A conventional receiver system has a filter circuit with unsatisfactory gain characteristics, and thus does not offer satisfactory reception performance. A receiver system of the invention has a filter circuit employing an equivalent inductor circuit including a capacitor, a gyrator composed of a plurality of operational transconductance amplifiers and having the capacitor as a load, and a resistor connected in series with the capacitor. A conventional receiver system has a band-pass filter circuit with a low third-order input intercept point, and thus does not offer satisfactory reception performance. The receiver system of the invention has, in the stage following a mixer, a band-pass filter circuit composed of a low-pass filter and a band-pass filter receiving the output signal of the low-pass filter, wherein the value obtained by dividing the higher cutoff frequency of the band-pass filter by the lower cutoff frequency thereof is smaller than 2, the center frequency of the band-pass filter is within a range of from about 1 to 3 MHz, and the cutoff frequency of the low-pass filter is higher than the center frequency of the band-pass filter.

Receiver system

The present invention provides an oscillation circuit which enables a further decrease of power consumption. The oscillation circuit comprises a piezoelectric oscillator, such as a quartz oscillator, for generating voltage that oscillates at a natural frequency, an inverter for amplifying this oscillation voltage, a Schmitt trigger circuit for shaping the waveform of the output of the inverter and outputting oscillation output signals, and a constant current source which is connected to a power supply line from a battery and supplies current to the power supply of the inverter and the Schmitt trigger circuit.

Oscillation circuit and electronic equipment comprising semiconductor integrated device with clock function including the oscillation circuit

The present invention provides a transceiver apparatus that permits miniaturization even when the antenna thereof is an unbalanced circuit and the transmitter circuit section and receiver circuit section thereof are balanced circuits. The transceiver apparatus is constituted comprising: a semiconductor integrated circuit device that mounts on the same semiconductor chip a balanced receiver circuitfor receiving a received signal as a differential input and balanced transmitter circuitfor outputting a transmitted signal as a differential output, and that has at least two terminalsconnected to connecting nodes that connect the balanced receiver circuitand the balanced transmitter circuit; first and second capacitors C,Cconnected to the terminalsrespectively; an external inductor Lconnected to the first and second capacitors C, C; a band pass filterand an antennacoupled to the first capacitor C; and a third capacitor Cconnected to the second capacitor C

Transceiver apparatus

A frequency modulating (FM) transmitter includes a reference frequency generator, a reference frequency divider, a stereo modulation circuit, an oscillator circuit, a program counter, and a PLL frequency synthesizer. The reference frequency generator is for generating a reference frequency. The reference frequency divider is for frequency dividing the reference frequency. The stereo modulation circuit is for frequency modulating audio signals by using one output of the reference frequency divider to supply resultant stereo modulated signals as FM signals. The oscillator circuit is for generating carrier waves to transmit the FM signals. The program counter is for frequency dividing the carrier waves into variable frequency components. The PLL frequency synthesizer has a phase comparator circuit for comparing the variable frequency components output from the program counter with another output of the reference frequency divider.

FM transmitter

The receiver includes a ceramic filter which is connected to the output side of a mixer circuit for limiting a band, an intermediate frequency amplifying circuit cascade connected to the output side of the ceramic filter in a plurality of intermediate frequency amplifying stages, and a plurality of passive band-pass filters connected between the respective intermediate frequency amplifying stages of the intermediate frequency amplifying circuit. Thereby, the receiver is able to reduce the size and costs thereof.

Growing community of inventors

Kyoto, Japan

Hiroyuki Ashida