Abstract: An amplifier capable of lowering an electrical current flowing in a peak amplifier before a carrier amplifier becomes saturated to thereby improve the efficiency of an entirety of the amplifier is provided. The amplifier includes a carrier amplifier circuit having an amplifying element operable in class-AB or class-B, and a plurality of peak amplifier circuits which have amplifying elements operating in class-B or class-C and which are arranged to start an operation in stages in response to an input level. An output of the carrier amplifier circuit and outputs of the peak amplifier circuits are combined together for signal output. One of the peak amplifier circuits which is rendered operative at the lowest input level is smaller in saturation output than the carrier amplifier circuit.

Abstract: A high frequency power amplifier includes an amplifying device for amplifying an input high frequency signal, a harmonic reflection circuit for reflecting a harmonic outputted from the amplifying device, and a harmonic generating circuit provided at an input terminal of the amplifying device, the harmonic generating circuit including a divider for dividing an input signal of a fundamental wave into two parts, a harmonic generator for generating a second harmonic from one part of the fundamental wave signal, and a combiner for combining the second harmonic generated from the harmonic generator with the other part of the fundamental wave signal to offer a combined signal to the amplifying device, wherein the harmonic reflection circuit reflects the second harmonic.

Abstract: An amplifier capable of lowering an electrical current flowing in a peak amplifier before a carrier amplifier becomes saturated to thereby improve the efficiency of an entirety of the amplifier is provided. The amplifier includes a carrier amplifier circuit having an amplifying element operable in class-AB or class-B, and a plurality of peak amplifier circuits which have amplifying elements operating in class-B or class-C and which are arranged to start an operation in stages in response to an input level. An output of the carrier amplifier circuit and outputs of the peak amplifier circuits are combined together for signal output. One of the peak amplifier circuits which is rendered operative at the lowest input level is smaller in saturation output than the carrier amplifier circuit.

Abstract: The performance of an amplifying system is improved by achieving adequate matching. The amplifying system for amplifying signals includes distributing means 1 that distribute a signal, a carrier amplifier 2 that amplifies the distributed first signal in Class AB, a peak amplifier 4 that amplifies the distributed second signal in Class B or Class C, a first transmission line having a given electric length and being connected to an output of the carrier amplifier, a second transmission line having a given electric length and being connected to an output of the peak amplifier, and a combining end 18 for combining an output of the first transmission line and an output of the second transmission line.

Abstract: A distortion compensation apparatus includes distortion generating means for generating distortions to compensate for a distortion generated in an amplifier 2. The distortion generating means includes a nonlinear circuit 13 having an input/output expansion characteristic as a circuit which generates a distortion of the lowest odd order as a compensation target and also includes a nonlinear circuit 18 having an input/output saturation characteristic as a circuit which generates a distortion of another odd order as a compensation target.

Abstract: In an apparatus for measuring absorbed power including an electromagnetic field probe 1 fixedly mounted within a head simulation phantom 2 which simulates the configuration and the electromagnetic characteristics of a head of a human body, and wherein the strength of an electric field or a magnetic field of a radio wave externally irradiated upon the head simulation phantom 2 is measured by the electromagnetic field probe 1, and the power of the radio wave absorbed by the head is estimated on the basis of measured values, the head simulation phantom 2 comprises a solid dielectric 10? which simulates the configuration and the electromagnetic characteristics of a head of a human body or a liquid dielectric 10 which simulates the electromagnetic characteristics of a head of a human body and which is filled in an enclosed vessel 10 which simulates the configuration of a head of a human body. The volume of the solid dielectric 10? or the volume of the enclosed vessel 11 is equal to or less than 5×105 mm3.

Abstract: A high frequency power amplifier includes an amplifying device for amplifying an input high frequency signal, a harmonic reflection circuit for reflecting a harmonic outputted from the amplifying device, and a harmonic generating circuit provided at an input terminal of the amplifying device, the harmonic generating circuit including a divider for dividing an input signal of a fundamental wave into two parts, a harmonic generator for generating a second harmonic from one part of the fundamental wave signal, and a combiner for combining the second harmonic generated from the harmonic generator with the other part of the fundamental wave signal to offer a combined signal to the amplifying device, wherein the harmonic reflection circuit reflects the second harmonic.

Abstract: The performance of an amplifying system is improved by achieving adequate matching. The amplifying system for amplifying signals includes distributing means 1 that distribute a signal, a carrier amplifier 2 that amplifies the distributed first signal in Class AB, a peak amplifier 4 that amplifies the distributed second signal in Class B or Class C, a first transmission line having a given electric length and being connected to an output of the carrier amplifier, a second transmission line having a given electric length and being connected to an output of the peak amplifier, and a combining end 18 for combining an output of the first transmission line and an output of the second transmission line.

Abstract: A distortion compensation apparatus includes distortion generating means for generating distortions to compensate for a distortion generated in an amplifier 2. The distortion generating means includes a nonlinear circuit 13 having an input/output expansion characteristic as a circuit which generates a distortion of the lowest odd order as a compensation target and also includes a nonlinear circuit 18 having an input/output saturation characteristic as a circuit which generates a distortion of another odd order as a compensation target.

Abstract: The invention relates to a high sensitivity receiver installed outdoors which may be used in a base station of a mobile communication system, for example. A received radio frequency signal is converted into a signal in a desired frequency band by a reception bandpass filter RXF3, is subject to a low noise amplification to a desired level by a low noise reception amplifier LNA4, and the amplified signal is converted into an optical signal by a laser diode LD5. RXF3, LNA4 and LD5 are confined in a heat shielding box. LD5 is cooled by cooling means to the order of critical temperature where RXF3, for example, assumes a superconducting state, whereby the dynamic range is increased and stabilized.

Abstract: Different carrier frequencies are chosen for plural transmitters of a transmitting device and signals are transmitted at frequency bands overlapping each other. In the receiving device weighting coefficients are provided in input-to-output paths of an interchannel interference canceller 21 so that the cross correlation between output signals from the interchannel interference canceller is minimized.

Abstract: To provide a super directional gain in a multi-element array antenna. An array antenna comprising a plurality of antenna elements A-1–A-4 spaced at intervals (equal to or less than a quarter of a wavelength) that provides a supergain is used. A weight generator circuit generates weight data in accordance with phase difference and amplitude difference among the antenna elements A-1–A-4 and directivity data of each of the antenna elements A-1–A-4. The generated weight data is used to weight each of the antenna elements A-1–A-4.

Abstract: In an apparatus for measuring absorbed power including an electromagnetic field probe 1 fixedly mounted within a head simulation phantom 2 which simulates the configuration and the electromagnetic characteristics of a head of a human body, and wherein the strength of an electric field or a magnetic field of a radio wave externally irradiated upon the head simulation phantom 2 is measured by the electromagnetic field probe 1, and the power of the radio wave absorbed by the head is estimated on the basis of measured values, the head simulation phantom 2 comprises a solid dielectric 10? which simulates the configuration and the electromagnetic characteristics of a head of a human body or a liquid dielectric 10 which simulates the electromagnetic characteristics of a head of a human body and which is filled in an enclosed vessel 10 which simulates the configuration of a head of a human body. The volume of the solid dielectric 10? or the volume of the enclosed vessel 11 is equal to or less than 5×105 mm3.

Abstract: In an apparatus for measuring absorbed power including an electromagnetic field probe 1 fixedly mounted within a head simulation phantom 2 which simulates the configuration and the electromagnetic characteristics of a head of a human body, and wherein the strength of an electric field or a magnetic field of a radio wave externally irradiated upon the head simulation phantom 2 is measured by the electromagnetic field probe 1, and the power of the radio wave absorbed by the head is estimated on the basis of measured values, the head simulation phantom 2 comprises a solid dielectric 10? which simulates the configuration and the electromagnetic characteristics of a head of a human body or a liquid dielectric 10 which simulates the electromagnetic characteristics of a head of a human body and which is filled in an enclosed vessel 10 which simulates the configuration of a head of a human body. The volume of the solid dielectric 10? or the volume of the enclosed vessel 11 is equal to or less than 5×105 mm3.

Abstract: A radio communication system is comprised of: a transmitting system in which N transmission signals, frequency-converted to the same transmission frequency, are generated by N transmitters, N being an integer equal to or greater than 2, and the transmission signals are each applied to each one of N elements of an antenna for transmission; and a receiving system in which each transmitted signal is received by N-element antenna and the cross correlation coefficient between the transmitted signals received by the N-elements is minimized to thereby reconstruct each transmitted signal. The plural transmitted signals of the same frequency are received and the cross correlation coefficients of the received transmitted signals are minimized to thereby permit multiplexing of the transmission signal.

Abstract: A divider/combiner unit combines RF signals, then converts the combined signal into an optical signal and sends it over an optical fiber. N radio access units each convert the optical signal received from the optical fiber into an RF signal and transmits it from an antenna, and each radio access unit converts an RF signal received by the antenna into an optical signal and sends it over an optical fiber to the divider/combiner unit. The divider/combiner unit converts the received optical signal into RF signals and outputs them. This system is operated as plurality of communication systems in common to them in correspondence to a plurality of input/output terminals of the divider/combiner unit.

Abstract: In a high sensitive radio receiver system for a diversity reception from two antennae per each of three sectors (SC1, SC3, SC3), a series connection of a bandpass filter (31 to 36) and a low noise amplifier (41 to 46) is contained in each of a plurality of vacuum chambers (81 to 86), the interior of which is cooled by a distinct, separate cooling unit (91 to 96). The two antennae per sector are connected to bandpass filters contained in different vacuum chambers.

Abstract: A mobile communication base station determines the oncoming direction of a radio wave with a simple arrangement and transmits a narrow angle beam in this direction. Received signals from a pair of wide angle beam antennae 21-1 and 21-2 having an equal configuration and a common orientation and which are located close to each other are fed to a direction finder receiver 22 and a communication receiver 15. By utilizing the fact that the both received signals have a coincident amplitude, a phase difference between the received signals is detected. The oncoming direction of the received radio wave (or the direction of a mobile station) is determined on the basis of the phase difference. A beam switcher 12 is controlled so as to connect a transmitter 13 to a narrow angle beam antenna (one of 11-1 to 11-4) which is directed in the oncoming direction thus determined.

Abstract: In a feedforward amplifier with a dual loop in which a distortion injection path of a distortion elimination circuit 50 is provided as a feedforward configuration composed of a first auxiliary amplifier distortion elimination circuit 60 and a first auxiliary amplifier distortion elimination circuit, a second variable attenuator 55 and a second variable phase shifter 56 are provided preceding the distortion detection circuit 60, a second pilot signal injected between stages of a main amplifier 14 is detected by a directional coupler 85, and the second variable attenuator 55 and the second variable phase shifter 56 are controlled by a second controller 97 to minimize the level of the detected second pilot signal, thereby bringing the distortion elimination circuit and the first auxiliary distortion detection circuit into balance at the same time.

Abstract: The invention relates to a high sensitivity receiver installed outdoors which may be used in a base station of a mobile communication system, for example. A received radio frequency signal is converted into a signal in a desired frequency band by a reception bandpass filter RXF3, is subject to a low noise amplification to a desired level by a low noise reception amplifier LNA4, and the amplified signal is converted into an optical signal by a laser diode LD5. RXF3, LNA4 and LD5 are confined in a heat shielding box. LD5 is cooled by cooling means to the order of critical temperature where RXF3, for example, assumes a superconducting state, whereby the dynamic range is increased and stabilized.