Abstract: A polar-loop wireless communication apparatus includes, on a forward path between an amplitude detector and a power amplifier which constitute an amplitude control loop, a variable gain amplifier and a switch to change characteristics of a loop filter to output a frequency bandwidth of the amplitude control loop to an order less than an order for normal operation. The system is operated with the characteristics set to the lower order to measure outputs from the power amplifier to calibrate the output power of the power transmitter, and the register is operated with the characteristics set to the higher order to measure the open loop gain of the amplitude control. According to results of the calculation, data to correct gain characteristics of the variable gain amplifier with respect to an output control signal is stored in a nonvolatile memory of a baseband circuit.

Abstract: A variable gain amplifier of low amplitude distortion, and low noise, having a large variable range, is provided. A variable gain differential amplifier that controls a gain by use of bias current is used as each of unit amplifiers (VGAs) making up the variable gain amplifier. A large variable gain range is obtained by series-connecting a plurality of the variable gain differential amplifiers. An attenuator is installed on the input side of the unit amplifier (VGA) at least in the initial stage. By doing so, it becomes possible to prevent amplitude distortion from occurring to the respective VGAs. An attenuator utilizing voltage division by capacitors, generating no noise, is used for lowering noise. Further, the variable gain amplifier is provided with a fixed gain amplifier installed in the final stage as necessary in order to obtain a total gain as desired.

Abstract: A variable gain amplifier of low amplitude distortion, and low noise, having a large variable range, is provided. A variable gain differential amplifier that controls a gain by use of bias current is used as each of unit amplifiers (VGAs) making up the variable gain amplifier. A large variable gain range is obtained by series-connecting a plurality of the variable gain differential amplifiers. An attenuator is installed on the input side of the unit amplifier (VGA) at least in the initial stage. By doing so, it becomes possible to prevent amplitude distortion from occurring to the respective VGAs. An attenuator utilizing voltage division by capacitors, generating no noise, is used for lowering noise. Further, the variable gain amplifier is provided with a fixed gain amplifier installed in the final stage as necessary in order to obtain a total gain as desired.

Abstract: When a transmitting oscillator is built in a communication semiconductor integrated circuit device like a high-frequency IC constituting a wireless communication system, the system prevents degradation of the accuracy of control on the output power of a power amplifier due to noise jumped from an output pin of the transmitting oscillator to an input pin for a detected signal (feedback signal) of an output level of the power amplifier. The transmitting oscillator is built in the high-frequency IC. The detected signal of the output level of the power amplifier, which is detected by a coupler, is attenuated to a level slightly higher than the level of noise jumped from the output pin of the transmitting oscillator to the input pin for a feedback signal of an amplitude control loop, which in turn is inputted to the feedback signal input pin of the high-frequency IC.

Abstract: The present invention provides a communication semiconductor integrated circuit device equipped with a high-frequency power amplifier circuit including a gain control amplifier and a bias circuit which supplies such a bias current as to linearly change the gain of the gain control amplifier, and a wireless communication system using the same. A bias current generating circuit which supplies a bias current to a linear amplifier that constitutes the communication high-frequency power amplifier circuit, comprises a plurality of variable current sources respectively different in current value and start level. These variable current sources are controlled according to an input control voltage and thereby combine their currents into a bias current. The combined bias current changes exponentially with respect to the input control voltage.

Abstract: A polar-loop wireless communication apparatus includes, on a forward path between an amplitude detector and a power amplifier which constitute an amplitude control loop, a variable gain amplifier and a switch to change characteristics of a loop filter to output a frequency bandwidth of the amplitude control loop to an order less than an order for normal operation. The system is operated with the characteristics set to the lower order to measure outputs from the power amplifier to calibrate the output power of the power transmitter, and the register is operated with the characteristics set to the higher order to measure the open loop gain of the amplitude control. According to results of the calculation, data to correct gain characteristics of the variable gain amplifier with respect to an output control signal is stored in a nonvolatile memory of a baseband circuit.

Abstract: The present invention provides a communication semiconductor integrated circuit device equipped with a high-frequency power amplifier circuit including a gain control amplifier and a bias circuit which supplies such a bias current as to linearly change the gain of the gain control amplifier, and a wireless communication system using the same. A bias current generating circuit which supplies a bias current to a linear amplifier that constitutes the communication high-frequency power amplifier circuit, comprises a plurality of variable current sources respectively different in current value and start level. These variable current sources are controlled according to an input control voltage and thereby combine their currents into a bias current. The combined bias current changes exponentially with respect to the input control voltage.

Abstract: A variable gain amplifier of low amplitude distortion, and low noise, having a large variable range, is provided. A variable gain differential amplifier that controls a gain by use of bias current is used as each of unit amplifiers (VGAs) making up the variable gain amplifier. A large variable gain range is obtained by series-connecting a plurality of the variable gain differential amplifiers. An attenuator is installed on the input side of the unit amplifier (VGA) at least in the initial stage. By doing so, it becomes possible to prevent amplitude distortion from occurring to the respective VGAs. An attenuator utilizing voltage division by capacitors, generating no noise, is used for lowering noise. Further, the variable gain amplifier is provided with a fixed gain amplifier installed in the final stage as necessary in order to obtain a total gain as desired.

Abstract: The present invention provides a communication semiconductor integrated circuit device equipped with a high-frequency power amplifier circuit including a gain control amplifier and a bias circuit which supplies such a bias current as to linearly change the gain of the gain control amplifier, and a wireless communication system using the same. A bias current generating circuit which supplies a bias current to a linear amplifier that constitutes the communication high-frequency power amplifier circuit, comprises a plurality of variable current sources respectively different in current value and start level. These variable current sources are controlled according to an input control voltage and thereby combine their currents into a bias current. The combined bias current changes exponentially with respect to the input control voltage.

Abstract: A differential circuit having a relatively simple structure capable of delivering a linear transfer characteristic and expanding an input dynamic range. An increase in magnitude of differential input voltage V.sub.in applied to each gate of differential-pair MOSFETs M1 and M2 in the differential circuit decreases control voltage V.sub.CONT in a control circuit. On the other hand, since a current fed to MOSFETs M3 and M4 in the differential circuit decreases simultaneously, a current supplied to the differential-pair MOSFETs M1 and M2 in the differential circuit increases. Thus, the present invention makes it possible to effectively expand the input dynamic range with respect to differential input voltage V.sub.in.

Abstract: An apparatus for checking the voltage applied to one or more electrical circuits provided on a substrate comprises a pair of power supply terminals respectively connected to each of the electrical circuits, a means for applying a voltage between the power supply terminals, a manually operable power switch means provided between the voltage applying means and one of the power supply terminals and a battery check device. The battery check device includes a battery check circuit provided on the substrate and connected between the power supply terminals. The battery check circuit is adapted to detect the voltage applied between the power supply terminals and to provide a detection signal indicating the result of the detection. The battery check device further includes a display means connected to the battery check circuit and adapted to indicate the detected voltage level in response to the detection signal.