Abstract: The invention presents a high efficiency linear power amplifier of plural frequency bands reduced in the number of parts and elements, simplified in the circuit construction, and saved in the circuit space, and in FIG. 1, signals entering from a common input terminal 1 in frequency bands A and B are matched in both frequency bands A and B in a wide band matching network 2, amplified in a pre-amplifier 3, put into a common terminal 4a of a switch circuit 4, and the signal in frequency band A is put into a changeover terminal 4b, matched in a matching network 5 and amplified in a post-amplifier 6, and its output is matched in a post-matching network 7 and sent out into an output terminal 8, while, similarly, the signal in frequency band B is put into other changeover terminal 4c of the switch circuit 4, matched in a matching network 9, amplified in a post-amplifier 10, and its output is matched in a post-matching network 11 and is sent out into an output terminal 12.

Abstract: A mobile station has a transmission/reception antenna, a reception antenna, external connector terminals, and transmitter and receiver circuits. Only the switch circuit, which includes a plurality of switch elements, is interposed between the antennas and external connector terminals, and the transmitter and receiver circuits. The switch circuit switches among modes of connection between the antennas and external connector terminals, and the transmitter and receiver circuits by switching the plurality of switch elements. A control circuit controls the switch circuit so that a signal passes through only one of the plurality of switch elements, by supplying a control signal to the switch circuit.

Abstract: A receiver comprises; an input TERM (11) for receiving a radio wave signal including at least one of 1st and 2nd radio wave components from an antenna; a 1st SW (12); a 1st BPF (13) for extracting the 1st radio wave component; a 2nd BPF (14) for extracting the 2nd radio wave component; a 2nd SW (17), the 1st and 2nd SW to selectively forming 1st and 2nd SIG passages through the 1st BPF in a 1st mode and the 2nd BPF in a 2nd mode respectively; a 1st LO (19) for generating 1st and 2nd LO SIGs (30a, 30b) in the 1st and 2nd modes respectively; a 1st mixer (18) for mixing an output of the 2nd SW with the 1st and 2nd LO SIGs in the 1st and 2nd modes respectively; a 1st FLT (21) for filtering an output of the 1st mixer to output 1st and 2nd IF SIGs having the same FRQ; a 2nd LO (22), 2nd mixer (23), a 2nd FLT (25) for generating 3rd and 4th IF SIGs corresponding to the 1st and 2nd radio wave components from an output of the 1st FLT in the 1st and 2nd modes, respectively.

Abstract: An unnecessary wave suppressing means suppresses unnecessary waves included in a reception high frequency signal in a frequency band that is changed in accordance with a switching signal. The unnecessary wave suppressing means changes the pass band by inserting a notch into a pass band at a range where a signal is to be suppressed, changing the pass band width so as to exclude a suppression band, retaining a plurality of narrow pass bands for respective frequency bands used and switching among those narrow pass bands in accordance with a frequency band of a receiving signal, or continuously changing the pass band by using a tuning filter.

Abstract: In a transmission circuit, part of the output signal of the transmission circuit is diverted by an output monitor circuit and subjected to envelope detection by an output detector circuit. The output signal of the output detector circuit is inputted to a peak hold circuit successively holding the peaks of the input signal, so that varying amplitude components are removed, and a DC value is detected. An error detector circuit compares the detected value with a reference signal from a reference signal generator circuit, and the error signal is used as a gain control signal to control the gain of a power amplifier circuit.

Abstract: A power amplifier amplifies a modulated carrier signal having an amplitude modulation component and a phase modulation component to generate a transmission signal. Part of the transmission signal is extracted by a monitor circuit. The detection signal detected by an envelope detector is compared with a burst control signal by a differential amplifier. The resulting error signal is input to a gain control terminal of a power amplifier through a sample and hold circuit, thus forming a feed-back loop. The sample and hold circuit outputs a sample signal during the transmission signal ramping-up and ramping-down periods, thus effectively turning ON the feed-back loop to an ON to control the transmission signal ramping-up and ramping-down. The sample and hold circuit outputs the hold signal during a modulated data transmission period, effectively turning OFF the feedback loop. As a result, a burst transmission output with a stable transmission power level can be obtained.

Abstract: An audio/video recording and reproducing system having a discrete function unit such as tape deck, record player or tuner connected thereto includes a function selection circuit and a function specifying switch disposed in a main unit, such as a pre/main amplifier, and a control line, such as remote control line, for connecting the main unit and the discrete unit. By virtue of the function selection circuit, the selection of a desired discrete function unit can be carried out at the main unit. However, in addition to this, the system includes an arrangement for permitting selection of a desired discrete function unit at the discrete function unit itself, and, when this is done, for controlling the function selection at the main unit to select the output of the discrete function unit.

Abstract: In an audio recording and reproducing system comprising a combination of audio units including a record player, a tuner and a tape deck and an amplifier unit including a preamplifier, a function switching system comprises a control unit arranged in the amplifier unit including a signal selection circuit for selecting out one of outputs of the audio units to a speaker, a control circuit for controlling the signal selection circuit and function switches for supplying function selection signals to the control circuit, and control signal lines for coupling the control circuit of the control unit to the audio units. The signal selection circuit responds to the actuation of a start switch of the audio unit to assume the selected function mode through the control signal line and the control circuit and responds to the actuation of a function switch of the control unit to assume the selected function mode.

Abstract: A function presetting circuit for an audio/video stereophonic playback system for presetting a function and controlling operations by a microcomputer comprises a reset circuit for providing a reset signal to the microcomputer at a time of power-on, a delay circuit for receiving the reset signal and delaying the reset signal a predetermined time period, and a presettable function presetting switch connected between the delay circuit and a key input terminal of the microcomputer.