Abstract: In a transmission circuit used in a TDD scheme, a preset current is supplied from a current source to a detection diode via a switch that is made conductive during a reception period and made non-conductive during a transmission period. A determination is made if the output of the detection diode is within a predetermined specified range and, if the output is out of the specified range, a judgment is made that the detection diode is faulty.

Abstract: From an antenna provided in a transmitter for transmitting a radio signal, the radio signal is transmitted in such a manner of: detecting transmission power of a transmission signal outputted to the antenna; detecting reflection power of a reflection signal reflected from the antenna; integrating the difference between the transmission power and the reflection power at a timing of transmitting a preamble signal of the radio signal; comparing the difference value obtained by the integration with a predetermined threshold value, and outputting an alarm in the case where the result of the comparison is that the difference value obtained by the integration is smaller than the threshold value.

Abstract: From an antenna provided in a transmitter for transmitting a radio signal, the radio signal is transmitted in such a manner of: detecting transmission power of a transmission signal outputted to the antenna; detecting reflection power of a reflection signal reflected from the antenna; integrating the difference between the transmission power and the reflection power at a timing of transmitting a preamble signal of the radio signal; comparing the difference value obtained by the integration with a predetermined threshold value, and outputting an alarm in the case where the result of the comparison is that the difference value obtained by the integration is smaller than the threshold value.

Abstract: In a transmission circuit used in a TDD scheme, a preset current is supplied from a current source to a detection diode via a switch that is made conductive during a reception period and made non-conductive during a transmission period. A determination is made if the output of the detection diode is within a predetermined specified range and, if the output is out of the specified range, a judgment is made that the detection diode is faulty.

Abstract: A power amplifier circuit includes a first variable gain amplifier for amplifying an input signal, a second variable gain amplifier for amplifying an output signal of the first amplifier, and a control circuit for controlling the gain of the first variable gain amplifier based on the output signal of the first variable gain amplifier and the gain of the second variable gain amplifier.

Abstract: An objective of this invention is to obtain a signal processing circuit and a signal processing method that reduce temperature-induced distortion when inputting a signal to a mixer and changing the frequency of the signal to a desired frequency. If a sensing result from a temperature sensor 133 is lower than a predetermined temperature, the attenuation factor of a first variable attenuator 102 is large while the attenuation factor of a second variable attenuator 108 is small. The magnitude relationship between the attenuation factors is reversed in a temperature range of the predetermined temperature or more. In a mixer 104 in which at a low temperature, the gain increases, and distortion increases, an increase in IM3 distortion can be prevented by increasing the attenuation factor at a low temperature. The same applies to a case where a mixer that has an amplifier arranged at a preceding stage thereof and makes the amplification factor of the amplifier large at a low temperature is used.

Abstract: Disclosed is a transmission output control apparatus for controlling transmitter output power to coincide with a first reference value. The apparatus includes an averaging circuit and a control section. The averaging circuit calculates an average value of said detection value of the output power. The control section outputs a differential signal between the average value and the first reference value as a transmitter output level control signal when the difference between said average value and said first reference value is less than a second reference value. The control section outputs a differential signal between said detection value and the first reference value as a transmitter output level control signal when the difference is equal to or greater than the second reference value.

Abstract: A power amplifier circuit includes a first variable gain amplifier for amplifying an input signal, a second variable gain amplifier for amplifying an output signal of the first amplifier, and a control circuit for controlling the gain of the first variable gain amplifier based on the output signal of the first variable gain amplifier and the gain of the second variable gain amplifier.

Abstract: An objective of this invention is to obtain a signal processing circuit and a signal processing method that reduce temperature-induced distortion when inputting a signal to a mixer and changing the frequency of the signal to a desired frequency. If a sensing result from a temperature sensor 133 is lower than a predetermined temperature, the attenuation factor of a first variable attenuator 102 is large while the attenuation factor of a second variable attenuator 108 is small. The magnitude relationship between the attenuation factors is reversed in a temperature range of the predetermined temperature or more. In a mixer 104 in which at a low temperature, the gain increases, and distortion increases, an increase in IM3 distortion can be prevented by increasing the attenuation factor at a low temperature. The same applies to a case where a mixer that has an amplifier arranged at a preceding stage thereof and makes the amplification factor of the amplifier large at a low temperature is used.

Abstract: Disclosed is a transmission output control apparatus for controlling transmitter output power to coincide with a first reference value. The apparatus includes an averaging circuit and a control section. The averaging circuit calculates an average value of said detection value of the output power. The control section outputs a differential signal between the average value and the first reference value as a transmitter output level control signal when the difference between said average value and said first reference value is less than a second reference value. The control section outputs a differential signal between said detection value and the first reference value as a transmitter output level control signal when the difference is equal to or greater than the second reference value.

Abstract: A program updating system having a communication function is composed of a first processor (1) that is operated by referring to a predetermined program and a second processor (2) which executes update of the program by using the communication function and then executes an update control of the program when a fault of the first processor (1) is detected. Thus, it is possible to provide the program updating system having the communication function, which can surely execute a program transfer, even if a fault is induced in the program to be updated.

Abstract: In a mobile apparatus for communication with a satellite, a plurality of antennas having different directivities from each other are provided. A selector circuit is connected between a transmitter circuit and the antennas to select and connect one of the antennas to the transmitter circuit. A control section controls the selector circuit in accordance with a reflected power detected from one of the antennas.

Abstract: A circuit for controlling a low-noise amplifier includes a low-noise transistor as an amplifying device. A bias voltage controller decreases a voltage to be applied to a gate of the transistor down to a voltage equal to or smaller than a pinch-off voltage to thereby pinch-off the low-noise amplifier, while power to be provided to the low-noise amplifier is kept off. In accordance with the circuit, even if an excessive input signal is input into the low-noise amplifier while the low-noise amplifier is not in operation, a gate current does not run through a transistor constituting the low-noise amplifier. Hence, it is possible to prevent destruction of a device and reduction in reliability of a device. In other words, the circuit operates as a circuit for protecting a device.

Abstract: In a burst signal transmitting apparatus for power-amplifying a burst signal to transmit the power-amplified burst signal, a correct transmission output can be obtained even in an initial burst signal after a power supply is turned ON. In this burst signal transmitting apparatus, a signal supply to a transmission antenna is blocked by a switch for a predetermined time period after the power supply is turned ON, but this signal is supplied to a dummy. During this time period, the initial burst signal is produced, and an automatic level control is carried out for this initial burst signal by way of an automatic level control loop constituted by a detector, an LPF, a differential amplifier, a reference voltage source, and a variable attenuator. Accordingly, the transmission level is converged to become constant. Thereafter, the burst signal is supplied to the transmission antenna by the switch, so that the operation is entered into the normal operation.

Abstract: A calibration system for calibrating a quadrature phase modulator comprises a signal generator for generating a pair of sine-wave signals which are quadrature in phase, an adjusting section for adjusting the amplitude and phase of the pair of sine-wave signals, a DC voltage offset block for adjusting the DC level of the pair of sine-wave signals, and a frequency spectrum analyzer for monitoring the output of the quadrature phase modulator. The output spectrum of the quadrature phase modulator includes three maximal points, two of which are caused by amplitude error, phase error and carrier leakage and minimized by consecutive adjustment in the adjusting block to calibrate the quadrature phase modulator.

Abstract: A frequency synthesizer includes a phase adder, a read only memory, a D/A converter, a bandpass filter, a low-pass filter, a phase comparator, a loop filter, a voltage controlled oscillator, and a frequency divider. The phase adder adds frequency setting data and output data of a plurality of bits every input clock to set the addition result as new output data. The read only memory outputs sine wave data on the basis of the output data from the phase adder. The D/A converter D/A-converts the sine wave data from the read only memory. The bandpass filter (particularly a switched capacitor filter) receives an output from the D/A converter and has a pass frequency which changes in accordance with the reference frequency of an output sine wave signal. The low-pass filter removes a high-frequency component from an output from the bandpass filter. The phase comparator compares the phase of an output from the low-pass filter with the phase of a frequency-divided output of the sine wave signal.

Abstract: In an intermediate frequency amplifier circuit having a crystal filter and a transistor amplifier, a tuning circuit including a coil and a capacitor is provided therebetween, and a current feedback resistor and a voltage feedback resistor are connected to the amplifying transistor. The resistance component of impedance is matched between the crystal filter and the amplifier by suitably selecting values of the resistors. Further, the reactance component of the impedance is matched therebetween by suitably selecting values of the coil and the capacitor. Thus, it is possible to obtain impedance matching between the crystal filter and the amplifier without degradation of NF and hence S/N ratio due the thermal noise caused by resistance elements in a conventional resistive attenuator which is conventionally used for impedance matching.