Abstract: An amplifier circuit according to the present invention comprises: a first differential amplifier circuit including a first transistor having a gate terminal forming a first input node, a second transistor having a gate terminal forming a second input node and having a dimensional ratio with respect to the first transistor of K:M (where K>M), and a first current source that supplies a first current to a source terminal of the first transistor and a source terminal of the second transistor; a second differential amplifier circuit including a third transistor having a gate terminal forming a third input node, a fourth transistor having a gate terminal forming a fourth input node and having a dimensional ratio with respect to the third transistor of M:K, and a second current source that supplies a second current to a source terminal of the third transistor and a source terminal of the fourth transistor, the second differential amplifier circuit having a same gain as the first differential amplifier circuit; a

Abstract: In a radio apparatus, the band of a loop filter of a synthesizer in a blank channel searching state is narrower than the band in a communicating state. In addition, a radio wave environment is measured. A characteristic necessary for the radio apparatus is determined corresponding to the measured-radio wave environment. The power is controlled corresponding to the performance of the radio apparatus. Thus, the power consumption is decreased. In addition, the efficiency of the output power is improved. In the radio apparatus, the current consumption of a power amplifier PA is measured. A matching circuit (LNA or MIX) of the antenna is adjusted with the measured result so as to decrease an antenna loss. In the radio apparatus, a DC offset is removed from the transmitted power and the reflected wave. When the DC offset is removed using an AC coupling capacitor, the deterioration of the frequency characteristic of the receiving portion is compensated with a capacitor in a digital signal process.

Abstract: A quadrature modulator for generating a transmission signal includes an orthogonal signal generator configured to generate a first local signal and a second local signal orthogonal to the first local signal, a mix-adder configured to generate a first RF signal based on a first baseband signal, the first local signal, and the second local signal, and a mix-subtracter configured to generate a second RF signal based on a second baseband signal, the first local signal, and the second local signal. The quadrature modulator also includes an output subtracter configured to determine a difference between the first RF signal and the second RF signal and to generate the transmission signal based on the difference; and an amplitude adjuster configured to adjust an amplitude of the first baseband signal before feeding it to the mix-adder or adjust an amplitude of the second baseband signal before feeding it to the mix-subtracter.

Abstract: In a radio apparatus, the band of a loop filter of a synthesizer in a blank channel searching state is narrower than the band in a communicating state. In addition, a radio wave environment is measured. A characteristic necessary for the radio apparatus is determined corresponding to the measured-radio wave environment. The power is controlled corresponding to the performance of the radio apparatus. Thus, the power consumption is decreased. In addition, the efficiency of the output power is improved. In the radio apparatus, the current consumption of a power amplifier PA is measured. A matching circuit (LNA or MIX) of the antenna is adjusted with the measured result so as to decrease an antenna loss. In the radio apparatus, a DC offset is removed from the transmitted power and the reflected wave. When the DC offset is removed using an AC coupling capacitor, the deterioration of the frequency characteristic of the receiving portion is compensated with a capacitor in a digital signal process.

Abstract: A frequency converter converts a first current signal having a first frequency into a second current signal having a second frequency different from the first frequency. The frequency converter includes an adder and a switching circuit. The adder adds the first current signal and a reference current signal to output a third current signal. The switching circuit passes only that portion of the third current signal larger in magnitude than a threshold current to output the second current signal.

Abstract: A frequency converter comprises an impedance matching unit connected to a current switching stage and a transconductance amplifier stage. The impedance matching unit has an impedance for conjugate power match. For example, the impedance matching unit is a parallel resonant circuit that includes an inductor and a capacitor that are formed as an integrated circuit. Thus, the frequency converter that has high conversion gain and low noise is obtained.

Abstract: An orthogonal demodulating section converts the frequency of received signals to the lower range after rejecting an image band thereof by an RE filter. An image rejecting section rejects the image band of the orthogonally converted output. It allows enough of an image rejecting degree to be obtained. An A/D converter section converts the whole range into a digital signal and an orthogonal demodulating section demodulates a desirable channel by means of digital processing. Then, a channel selecting section selects and outputs the desirable channel.

Abstract: A frequency converter comprises a first mixer which frequency-converts an input signal with a first conversion gain in accordance with a local signal, a second mixer which frequency-converts the input signal with a second conversion gain lower than the first conversion gain in accordance with the local signal, and an adder which adds the output signals of the first and second mixers in opposite phase to each other in order to reduce distortion.

Abstract: A frequency converter converts a first current signal having a first frequency into a second current signal having a second frequency different fro the first frequency. The frequency converter includes an adder and a switching circuit. The adder adds the first current signal and a reference current signal to output a third current signal. The switching circuit passes only that portion of the third current signal larger in magnitude than a threshold current to output the second current signal.

Abstract: A variable gain amplifier device controlled by a first gain control signal comprises a gain controlled amplifier having a gain and including a differential pair of first and second MOS type transistors configured to operate in a weak inversion region; and a control signal converter configured to convert the first gain control signal into a second gain control signal, and supply the second gain control signal to the gain controlled amplifier to exponentially vary the gain with respect to the first gain control signal.

Abstract: A variable gain amplifier device controlled by a first gain control signal comprises a gain controlled amplifier having a gain and including a differential pair of first and second MOS type transistors configured to operate in a weak inversion region; and a control signal converter configured to convert the first gain control signal into a second gain control signal, and supply the second gain control signal to the gain controlled amplifier to exponentially vary the gain with respect to the first gain control signal.

Abstract: A variable gain amplifier device controlled by a first gain control signal comprises a gain controlled amplifier having a gain and including a differential pair of first and second MOS type transistors configured to operate in a weak inversion region; and a control signal converter configured to convert the first gain control signal into a second gain control signal, and supply the second gain control signal to the gain controlled amplifier to exponentially vary the gain with respect to the first gain control signal.

Abstract: A frequency converter converts a first current signal having a first frequency into a second current signal having a second frequency different from the first frequency. The frequency converter includes an adder and a switching circuit. The adder adds the first current signal and a reference current signal to output a third current signal. The switching circuit passes only that portion of the third current signal larger in magnitude than a threshold current to output the second current signal.

Abstract: An image suppression filter circuit comprises a first phase shifter outputting a first output signal and a second output signal substantially orthogonal thereto, a second phase shifter outputting a third output signal and a fourth output signal orthogonal to the third output signal, a first subtracter subtracting the fourth output signal from the first output signal, a first adder adding the second and third output signals, a third phase shifter outputting a fifth output signal and a sixth output signal orthogonal to the fifth output signal, a fourth phase shifter outputting a seventh output signal and an eighth output signal orthogonal thereto, a second subtracter subtracting the eighth output signal from the fifth output signal, and a second adder adding the sixth and the seventh output signals.

Abstract: A frequency converter configured to convert a first current signal having a first frequency into a second current signal having a second frequency different from the first frequency is disclosed, which comprises an adder configured to add the first current signal and a predetermined reference current signal to output a third current signal corresponding to the sum of the first current signal and the reference current signal, and a switching circuit configured to pass only that portion of the third current signal which is larger in magnitude than a threshold current to output the second current signal.

Abstract: An amplifier circuit comprises a differential amplifier configured by a differential pair of transistors, a common emitter amplifier connected in parallel to the differential amplifier and configured by a pair of common-emitter configuration transistors, input and output terminals which are common to the differential amplifier and the common emitter amplifier, and a bias controller connected to the differential amplifier and the common emitter amplifier and configured to control a bias of at least one of the differential amplifier and the common emitter amplifier.

Abstract: A mobility proportion current generator comprises a voltage adder including a first MOS transistor, the voltage adder adding a voltage whose temperature dependency is small with respect to the mobility and a threshold voltage of the first MOS transistor to output a sum voltage, and a second MOS transistor including whose drain terminal is connected to a constant potential point, the sum voltage of the voltage adder being applied between the gate terminal and the source terminal of the second MOS transistor to output a current proportional to the mobility being output from the drain terminal thereof.

Abstract: A mobility proportion current generator comprises a voltage adder including a first MOS transistor, the voltage adder adding a voltage whose temperature dependency is small with respect to the mobility and a threshold voltage of the first MOS transistor to output a sum voltage, and a second MOS transistor including whose drain terminal is connected to a constant potential point, the sum voltage of the voltage adder being applied between the gate terminal and the source terminal of the second MOS transistor to output a current proportional to the mobility being output from the drain terminal thereof.

Abstract: A mobility proportion current generator comprises a voltage adder including a first MOS transistor, the voltage adder adding a voltage whose temperature dependency is small with respect to the mobility and a threshold voltage of the first MOS transistor to output a sum voltage, and a second MOS transistor including whose drain terminal is connected to a constant potential point, the sum voltage of the voltage adder being applied between the gate terminal and the source terminal of the second MOS transistor to output a current proportional to the mobility being output from the drain terminal thereof.

Abstract: In a radio apparatus, the band of a loop filter of a synthesizer in a blank channel searching state is narrower than the band in a communicating state. In addition, a radio wave environment is measured. A characteristic necessary for the radio apparatus is determined corresponding to the measured-radio wave environment. The power is controlled corresponding to the performance of the radio apparatus. Thus, the power consumption is decreased. In addition, the efficiency of the output power is improved. In the radio apparatus, the current consumption of a power amplifier PA is measured. A matching circuit (LNA or MIX) of the antenna is adjusted with the measured result so as to decrease an antenna loss. In the radio apparatus, a DC offset is removed from the transmitted power and the reflected wave. When the DC offset is removed using an AC coupling capacitor, the deterioration of the frequency characteristic of the receiving portion is compensated with a capacitor in a digital signal process.