Oki Electric Industry Co., Ltd.

Oki Electric Co., Ltd.

Tetsuo Onodera

Eiichi Nakanishi

Hefeng Wang

Hiroshi Shimizu

Haruhiko Akiyama

Output power control device

In a mobile radio transceiver, an antenna has a fixed element and a movable element. When the movable element is in an extended state, the movable element functions. On the other hand, when the movable element is in a retracted state, the fixed element functions. An impedance matching circuit preferentially performs impedance matching relative to the fixed element. A reactance element is further provided which is connected to the movable element when the movable element is in the extended state. On the other hand, the reactance element is out of connection to the movable element when the movable element is in the retracted state. With this arrangement, the impedance matching circuit and the reactance element cooperatively achieve impedance matching relative to the movable element when the movable element functions. Alternatively, if the impedance matching circuit preferentially performs impedance matching relative to the movable element, the reactance element is connected to the fixed element when the fixed element functions.

Antenna with fixed and movable elements

In a dual mode transmitter for modulating, in a digital mode, an input digital signal and transmitting a modulated digital signal and modulating, in an analog mode, an input analog signal and transmitting a modulated analog signal, a digital modulating section modulates the input digital signal to thereby generate the modulated digital signal, and outputs the modulated digital signal. An analog modulator/carrier generator modulates the input analog signal to thereby generate the modulated analog signal, and outputs it. Also, the analog modulator/carrier generator generates a carrier signal for up-converting the modulated digital signal. The up-converter up-converts, in the digital mode, the modulated digital signal by using the carrier signal and receives, in the analog mode, the modulated analog signal and passes it therethrough.

Dual mode transmitter

A linear receiver is disclosed which includes a linear receiver having: a preamplifier for amplifying linearly a modulated carrier signal (RF signal) having a first frequency trapped by an antenna; a mixer for converting the RF signal into an intermediate frequency signal having a second frequency less than the first frequency in accordance with a local oscillation signal; an IF stage for analogue delivering a demodulated output signal by saturatedly amplifying the intermediate frequency signal and for outputting an RSSI signal which indicates a level of the RF signal; an IF stage for digital incorporating therein an AGC input terminal for controlling an amplitude gain thereof for outputting an in-phase (I) signal and a quadrate (Q) signal, respectively, with the intermediate frequency signal by linearly amplifying the intermediate frequency signal; a first feed back loop circuit for providing a first feed back control signal to the AGC input terminal so as to keep demodulation levels of the I signal and the Q signal constant and not to be saturated; and a second feed back loop circuit for providing a second feed back control signal to the preamplifier and/or the mixer so as to keep the preamplifier and/or the mixer not to be saturated.

Linear receiver having dual automatic gain control loops

According to a first aspect, a portable electronic device has at least two load circuits which are independently powered by different batteries. According to a second aspect, the load circuits are powered by the same battery, but their power lines are branched from a node located close to the battery, thereby reducing common impedance. According to a third aspect, two power lines are coupled through switches to two independent batteries, and are mutually coupled through a third switch. The switches are controlled according to the discharge states of the batteries. According to a fourth aspect, a battery charger charges two or more batteries by supplying current to them for short intervals in turn, so that all batteries reach full charge at substantially the same time.

Portable electronic device and method for supplying current to different

A power control circuit having a saturation preventing control loop including a variable gain amplifier, an RF power amplifier, a directional coupler, a detecting circuit, a comparator, a switch, and an adder. When the signal level of an output signal of the comparator is low, the switch is turned on. When the signal level of the output signal of the comparator is high, the switch is turned off. A system power control loop includes a system power control terminal, the adder, and the variable gain amplifier. Since the saturation preventing control loop is provided with the switch, the saturation preventing control loop operates only when the signal level of the amplified signal is larger than a reference value. The system power control loop can properly operate according to a system power control signal supplied from the system power control terminal.

Power control circuit for use with transmitter

A quadrature phase-shift keying modulator produces a QPSK signal which is amplified by a power amplifier. The amplitude gain of the power amplifier is controlled in response to an amplitude difference between the QPSK signal output by the modulator and the amplified QPSK signal output by the power amplifier. A phase detector, connected in series between the modulator and the power amplifier, eliminates amplitude variations from the QPSK signal prior to amplification. A voltage-controlled phase shifter, connected in series between the phase detector and the power amplifier, shifts the QPSK signal in phase by an amount responsive to amplitude information in the QPSK signal.

QPSK power amplifier distortion correction system

A radio receiver for data communication of the type handing digital signals has a radio frequency (RF) section for receiving an RF signal having a predetermined frequency band from an electromagnetic wave which comes in through an antenna. A first frequency converting section converts the RF signal received by the RF section to a first intermediate frequency (IF) signal. A first IF filter filters the first IF signal and is implemented by a surface acoustic wave filter. A second frequency converting section converts the output signal of the first IF filter to a second IF signal. A data amplifying section picks up the above-mentioned frequency band from the output of the second frequency converting section and amplifies the resultant, picked-up band. A detector detects the output of the data amplifying section. An equalizer corrects a deviation of group delay time with each of respective frequencies of the output of the detector.

Radio receiver for data communication

A power amplifying apparatus according to the present invention can provide a stable electric power output with wide range by controlling both of the output amplifier for amplifying the electric power and the pre-amplifier disposed at the front of the output amplifier. Furthermore, in order to avoid the disadvantage that a transmission spectrum is expanded because of no supply of a stable voltage to be supplied to the electric power amplifier, thereby producing a cross-talk, a stabilizing power source circuit is provided to stabilize the voltage between the power amplifier and the power source for supplying the voltage.

Power amplifying apparatus for wireless transmitter

A power amplifier system suitable for a mobile radio receiver/transmitter is described. A wave form signal to be transmitted is made smooth during its rise and fall times, thereby making it possible to prevent a transmission spectrum from expanding and interfering with the adjacent channels. The power amplifier system compares an envelope signal of an inputted RF signal and that of an RF signal to be outputted, whereby the power amplifier system as a whole provides linear amplification.

Power amplifier system for radio transmitter and method for using the

In a linear amplifier circuit, an amplifier amplifies an input signal to produce an output signal, an input signal envelope detector detects the envelope of the input signal, and an output signal envelope detector detects the envelope of the output signal. The difference between the outputs of the envelope detectors is determined, and the amplifier is controlled in accordance with the difference so that the level of the output signal is linearly related to the input signal. Compensation circuits are provided for temperature compensation of the linearity in the characteristic of the envelope detectors.

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Tokyo, Japan

Tetsuo Onodera