Rohm Co., Ltd.

Rf Chips Technology Inc.

Yoshikazu Shimada

Isoshi Takeda

Hiroyuki Ashida

Hiroo Mochida

Tamotsu Suzuki

Sadao Igarashi

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 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

An integrated circuit device as a first IC chip, a second IC chip, and a circuit board having a hole formed therein that is large enough to permit the second IC chip to be accommodated therein. The first and second IC chips are bonded together so as to be electrically connected together, and the first IC chip is mounted on the circuit board with the second IC chip accommodated in the hole formed in the circuit board. Here, one of the IC chips forming a chip-on-chip structure is accommodated in the hole formed in the circuit board, making further thickness reduction possible. Moreover, the obverse surfaces of the IC chips are located closer to the circuit board, making possible wireless mounting of the IC chips, despite forming a chip-on-chip structure, on the circuit board through connection using bumps. This helps reduce trouble due to inductance in a circuit that handles a high-frequency signal.

Integrated circuit device

An oscillation circuit is provided which is easily adjusted with a high degree of accuracy. The oscillation circuit including a filter having a time constant and an inverting amplifier which feeds back the output of the filter to the input side of the filter so that an oscillation condition is fulfilled. The filter includes a gm amplifier formed of a differential amplifier, and a capacitor. The constant current source of the differential amplifier is connected to a free running oscillation frequency adjusting circuit. The adjusting circuit includes a microcomputer, a decoder which decodes the output data of the microcomputer and a switching circuit driven by the output of the decoder and varying the current value according to the output of the decoder. A current in accordance with a current value depending on the setting of the switch flows through the constant current source.

Oscillation circuit

An FM signal phase-shifted by 90.degree. and an FM signal not phase-shifted are supplied to a multiplier to demodulate a stereo composite signal. A 90.degree. phase shifting circuit has a first oscillation circuit whose phase shift amount varies according to a timing at which the amount of a current flowing through a charging and discharging capacitor is changed. A multiplexer is provided to process the stereo composite signal to output left and right channel signals. The multiplexer has a second oscillation circuit for generating a signal multiplied by the stereo composite signal to extract the left and right channel signals from the composite signal. The first and second oscillation circuits each have a differential amplifier. The constant current of the constant current source of each differential amplifier is set by trimming-regulate it by a regulating circuit.

FM signal processor

A low-pass passive filter is inserted in the phase locked loop of a voltage-controlled oscillating circuit having a varactor diode. The filter has a first resistor, a capacitor and a second resistor connected in that order and the blocking characteristics of the filter are changed in accordance with a selected value of the second resistor. A push-pull output circuit in which the upstream transistor is connected directly to the supply voltage line receives the signal from a phase comparator circuit (which is indicative of the result of phase comparison) and outputs it to the low-pass passive filter. The low-pass passive filter controls the terminal voltage of the varactor diode in accordance with the terminal voltage of the capacitor and the value of the second resistor is selected depending on the desired blocking characteristics of the filter.

PLL circuit having a low-pass passive filter coupled to a varactor diode

A phase shifting circuit has an oscillation circuit. The oscillation circuit is provided with a charging and discharging capacitor at which the oscillation signal is generated. The oscillation signal has a constant level period and a saw tooth wave period. A valve of current flowing through the capacitor is changed in the middle of the saw tooth wave period by an input signal. An output of the phase shifting circuit is phase-shifted by 90.degree. with respect to the input signal.

Growing community of inventors

Kyoto, Japan

Yoshikazu Shimada