Abstract: To provide a high frequency switch capable of dealing with multiple frequency bands without having plurality of switch circuits. A first diode that conducts due to a bias current when a first switch is closed is interposed between a first signal terminal and a second signal terminal. A strip line with the electrical length L1 is connected to the cathode of the first diode, the other end being grounded. At a position with the distance L2 from one end of the strip line, a capacitor and a second switch are connected to be equivalently grounded when a second switch is closed. The strip line resonates with the electrical length L1 when the second switch is opened, and resonates with the electrical length L2 when the second switch is closed.

Abstract: To provide a high frequency switch capable of dealing with multiple frequency bands without having plurality of switch circuits. A first diode that conducts due to a bias current when a first switch is closed is interposed between a first signal terminal and a second signal terminal. A strip line with the electrical length L1 is connected to the cathode of the first diode, the other end being grounded. At a position with the distance L2 from one end of the strip line, a capacitor and a second switch are connected to be equivalently grounded when a second switch is closed. The strip line resonates with the electrical length L1 when the second switch is opened, and resonates with the electrical length L2 when the second switch is closed.

Abstract: To provide a high frequency switch capable of dealing with multiple frequency bands without having plurality of switch circuits. A first diode that conducts due to a bias current when a first switch is closed is interposed between first signal terminal and a second signal terminal. A strip line with the electrical length L1 is connected to the cathode of the first diode, the other end being grounded. At a position with a distance L2 from one end of the strip line, a capacitor and a second switch are connected to be equivalently grounded when the second switch is closed. The strip line resonates with the electrical length L1 when the second switch is opened, and resonates with the electrical length L2 when the second switch is closed.

Abstract: A quadrature demodulator 408? and a quadrature modulator 908? convert a reception intermediate frequency signal 151 into reception baseband signals 157 and 158, and also convert transmission baseband signals 657 and 658 into a transmission intermediate frequency signal 651, respectively. While local oscillation signals having frequencies suitable for the respective bands are outputted from a commonly used local oscillator 111, such a local oscillation signal obtained by shifting a phase thereof ?/2 by a phase shifter 412 is supplied to one mixer of quadrature mixers 109 and 609, and such a signal obtained by inverting, or not inverting the plurality of the local oscillation signal by an exclusive OR gate circuit 413 in response to a band switching signal 153 is supplied to the other mixer of quadrature mixers 110 and 610.

Abstract: To provide a high frequency switch capable of dealing with multiple frequency bands without having a plurality of switch circuits. A first diode (3) that conducts due to a bias current when a first switch (8) is closed is interposed between a first signal terminal (1) and a second signal terminal (5). A strip line (11) with the electrical length L1 is connected to the cathode of the first diode (3), the other end being grounded. At a position with the distance L2 from one end of the strip line (11), a capacitor (12) and a second switch (13) are connected to be equivalently grounded when a second switch (14) is closed.

Abstract: A portable radio device including a frequency synthesizer 5 for producing a local signal for radio section, a digital control circuit 6 for digitally controlling a portion of or the entirety of the radio device, and a reference signal generator 1 which operates the frequency synthesizer and the digital control circuit, wherein a buffer amplifier 2 is provided between the reference signal generator and the digital control circuit, and switching means 4 is provided in parallel with the buffer amplifier between the reference signal generator and the digital control circuit. When the frequency synthesizer is inactive, the switching means is activated, and a power supply 3 of the buffer amplifier is deactivated. As a result, the power dissipated by the buffer amplifier can be reduced without deteriorating the characteristics of the frequency synthesizer.

Abstract: A controllable-frequency oscillator has a first portion for generating a signal having a controllable frequency. The controllable-frequency oscillator has a second portion for controlling the frequency of the signal generated by the first portion in response to a first control signal. The controllable-frequency oscillator has a third portion for controlling the frequency of the signal generated by the first portion in response to a second control signal separate from the first control signal.

Abstract: A first mobile unit identification system having a interrogator and responder. The interrogator transmits a given magnitude of a spread spectrum coded signal in standby mode. The responder receives the spread spectrum coded signal and when the magnitude of received signal exceeds a given value, it reflects the transmitted spread spectrum coded signal with ID code when the magnitude of received signal exceeds the given value. The interrogator receives this and then, transmits data to the responder with amplitude modulating the spread spectrum coded signal with the data. The responder detects by amplitude demodulation and stores the detected data. The interrogator may transmit a mode change code. The responder may transmit an end code after transmission of a data train. A second interrogator informs the responder of the standby mode thereof by amplitude-modulated signal having a given cycle.

Abstract: A data receiving system comprising an I base-band signal and a Q base-band signal which are used in a quadrature demodulation operation. Zero-crossing points of respective base-band signals are detected and a control signal is generated in response to each zero-crossing point. A phase-shift switching circuit alternately selects either the I base-band signal or the Q base-band signal in response to the control signal to generate an I/Q base-band signal. And, a demodulation operation is executed on the basis of the I/Q signal.