Nec Corporation

Matsushita Electric Industrial Co., Ltd.

Panasonic Corporation

Noriyuki Fujita

Masahiko Tanaka

Junichi Matsuura

Shigeo Masai

Masaharu Sato

Eiichi Kaminishi

An amplifying device for setting input impedance at several G&#x3a9; to several tens of G&#x3a9; and improving an ESD withstand current rating is provided. An ECM is connected to an input terminaland frequency characteristics become flat to a voice band by high input impedance of a CMOS amplifierand the input impedance is set at several G&#x3a9; to several tens of G&#x3a9; and thereby, response time after detecting a loud voice or turning on a power source of the ECM is speeded up and desired electrical characteristics are achieved. A path for releasing a surge voltage which occurs during assembly in the outside of an IC and intrudes from the input terminalto a power source terminal or an earth terminal without an influence on a signal (20 Hz to 20 kHz) of a voice band entering from the input terminalcan be constructed by connecting a P-channel MOS transistorand an N-channel MOS transistoras an ESD protective element.

Amplifying device

To provide a voltage controlled variable capacitor which can change a capacitance value thereof in a wide controlled voltage range and control the capacitance value easily with a high precision without complicating the circuit configuration thereof, and to provide a voltage controlled variable capacitor which can change a capacitance value thereof with a good linearity. The voltage controlled varactor is configured in a manner that varactors VCk, each formed by a series connection of a fixed capacitor Ck (k=1, 2, . . . , n) and a MOS transistor Mk of N channel type, are connected in parallel. The MOS transistors Mto Mn are configured in a manner that gate widths W are same but gate lengths Lto Ln are elongated sequentially (that is, L&#x3c;L&#x3c; . . . &#x3c;Ln) so that the threshold voltages thereof are differentiated from one another.

Voltage controlled variable capacitor

A radio cell station apparatus includes a plurality of transmitters and a controller. The plurality of transmitters can transmit signals to a personal mobile station. The controller selectively activates one of the plurality of transmitters based on a positioning data corresponding to a position of the personal mobile station, such that the activated transmitter communicates with the radio cell station apparatus using a transmission signal.

Mobile communication system with transmitting systems with different outputting power

Detection outputs 103 and 104 of phase-detection sections 9 and 19 of two reception circuits are input to phase difference detection sections 10 and 20, respectively. A detection output 103 indicating an instantaneous phase amount of each symbol as each phase output of a QPSK received signal is converted into phase difference detection outputs 105 and 106 each indicating a difference between the respective symbols. The output is input to a combination process section 23 where amplitude signals 101 and 102 are operated as weighting factors and vector combination so as to obtain a combination signal.

Method of combining received signal of diversity type radio device and

Disclosed is a transmitting diversity circuit for a TDMA radio unit which has: a plurality of antennas; a plurality of transmitting circuits; a plurality of receiving circuits; a first switch which is connected with one of the plurality of transmitting circuits and selects one of the plurality of antennas; a second switch which is connected with the first switch and selects the one or the other of the plurality of transmitting circuits; a third switch which is connected with the second switch and one or more of the plurality of receiving circuits and selects one of the plurality of transmitting circuits or the one or more of the plurality of receiving circuits; a judging circuit which controls the switching of the first and second switches according to a level of received field strength to be detected by the receiving circuit connected with the third switch; wherein the one of the plurality of transmitting circuits is connected through the first to third switches with the selected one of the plurality of antennas.

Transmitting diversity circuit for TDMA radio unit

A linear compensating circuit comprises a first level detection circuit for detecting the level of an input signal to an amplifier, a second level detection circuit for detecting the level of an output signal from the amplifier, an amplitude compensating circuit for controlling the amplitude of the input signal in accordance with the difference between the signal level detected by the first detection circuit and the signal level detected by the second level detection circuit for improving the linearity of an input-output characteristic of the amplifier, and a phase compensating circuit for controlling the phase of the input signal in accordance with the signal level detected by the second detection circuit. The linear compensating circuit compensates for both amplitude and phase and, as a result, the degradation of phase characteristic caused by amplitude compensation can be prevented, resulting in a reduction in the distortion of the output signal of the amplifier even when it is being operated in the vicinity of the saturation range. This linear compensating circuit is effective when applied to a power amplifier, particularly to a high frequency power amplifier.

Linear compensating circuit

In an amplifier comprising an FET (11) having a gate electrode and source and drain electrodes and a drain bias circuit (19) controlled by an output power control command to supply a drain bias to the drain electrode, a gate bias circuit (17) is controlled by the output power control command to supply the gate electrode with a controlled voltage as a gate bias. The gate bias circuit may have a voltage source terminal (25) given a predetermined voltage and comprises a gate bias control device (27) for controlling the predetermined voltage so as to develop the controlled voltage in accordance with the output power control command. Preferably, the device comprises a ROM for memorizing gate voltage data and a voltage producing section for converting the predetermined voltage to the controlled voltage in compliance with one of the gate voltage data that is selected by the command. Alternatively, the device comprises a voltage divider for dividing the predetermined voltage into divided voltages and a selector for selecting one of the divided voltages as the controlled voltage in accordance with the command.

FET amplifier with gate voltage control

A radio frequency (RF) amplifier for amplifying an RF signal with a high power efficiency and with a minimum of signal distortions by using a GaAs field effect transistor (FET). An idling current for class 'A' amplification is set in the FET. An output low pass filter is connected to the drain of the FET and provided with an impedance higher than a high gain impedance, so that the FET and a load may be matched in power during high RF signal operation, i.e., the dynamic impedance of the FET and the impedance of the load may be matched. A drain bias to the FET is turned on and turned off in synchronism with the ON/OFF of the input RF signal. The amplifier, therefore, not only performs class 'A' amplification with a minimum of signal distortions but also further saves power since it is turned off in the absence of a signal, thereby achieving a higher power efficiency.

Growing community of inventors

Saitama, Japan

Noriyuki Fujita