Abstract: A receiving device includes a mixer, an AC coupling circuit, a post-stage circuit, and a DC offset calibration circuit. The mixer is utilized for mixing an input signal with a local oscillating (LO) signal from an oscillator to generate a converted signal. The AC coupling circuit is coupled to the mixer and utilized for reducing at least one portion of DC offset of the converted signal to generate a filtered signal. The post-stage circuit is coupled to the AC coupling circuit and utilized for processing the filtered signal to generate an output signal. The DC offset calibration circuit is coupled to the post-stage circuit and utilized for providing at least a compensation current for the post-stage circuit to reduce DC offset of the output signal.

Abstract: A receiving apparatus includes an amplification section that amplifies a received signal and a frequency conversion section that converts a frequency of the received signal, from a radio frequency to a baseband, the baseband having a lower frequency than the radio frequency. A gain control section amplifies, by a predetermined gain, the signal that has been subjected to the frequency conversion to the baseband. A voltage calibration section performs calibration on an offset voltage generated in the signal subjected to frequency conversion to the baseband. A time constant control section sets a first time constant during a reception operation and sets a second time constant, which is reduced with respect to the first time constant, during the calibration.

Abstract: An automatic gain control device capable of reducing signal saturation or signal distortion caused by out-of-band signals of a filter or delay of a control signal. An AGC response control section compares a level of control voltage (‘V2_I terminal’ signal) output from an AGC control section b with a level of control voltage (‘V3_I terminal’ signal) output from an AGC control section c. If the ‘V3_I terminal’ signal is below the ‘V2_I terminal’ signal, an AGC amplifier is controlled by the ‘V3_I terminal’ signal. If the ‘V3_I terminal’ signal is above the ‘V2_I terminal’ signal, the AGC amplifier is controlled by the ‘V2_I terminal’ signal. In the latter case, control information of the AGC control section b is replaced by control information of the AGC control section c so that the AGC control section c controls the AGC amplifier c.

Abstract: A reception apparatus capable of calibrating a DC offset voltage fast and with high accuracy even in an environment in which interferer exist without causing noise characteristic degradation. In this apparatus, a digital signal processing section (108) controls the gain of a received signal at such a gain that predetermined reception quality is obtained. A time constant control circuit (110) controls the time constant and makes the amount of attenuation of the received signal of a low pass filter (106a) more moderate compared to the case where a DC offset voltage is not calibrated during DC offset voltage calibration. A voltage calibration circuit (111) calibrates the DC offset voltage generated in the received signal when controlling the gain.

Abstract: The direct conversion receiving apparatus has a gain control amplifier for variably amplifying a base band signal based on a gain switching control signal. A high pass filter has a first circuit including capacitors connected in parallel that are inserted in a path connecting an input terminal to an output terminal and switching effective total capacitance of the capacitors based on a first time constant switching control signal, and a second circuit including a resistor for providing a predetermined direct current voltage to the output terminal and switching the effective resistance value of the resistor based on a second time constant switching control signal. A control circuit outputs the gain switching control signal, and the first and second time constant switching control signals according to the change of the gain control of said gain control amplifier.

Abstract: An automatic gain control loop for a radio receiver, comprising a switchable lowpass filter (21) to reduce distortions in an analogue gain control signal (6) by switching said switchable lowpass filter (21) to a low time constant in case a change of a gain control signal (6) of the automatic gain control loop lies above a predetermined threshold, which low time constant is lower than a normally used time constant, comprises a hold unit (24) which affects that said switchable lowpass filter (21) uses said low time constant a predetermined time after a change of the gain control signal (6) of the automatic gain control loop lies below said predetermined threshold.

Abstract: A feedback circuit for amplification of the output signal of an analog front end and suppression of its DC and low frequency components comprises a variable gain amplification unit (2) controlled by a gain control signal and a reverse path unit (6) comprising a filter unit (8) with variable time constant. A control unit (13) produces the gain control signal as well as a reverse path control signal (S) which causes adaptation of variable resistances (12) and capacitances (10) in such a way that the time constant of the filter unit (8) varies essentially proportionally with the gain of the variable amplifier unit (2). Thereby the gain of the feedback circuit as a function of the frequency retains its shape with varying gain.

Abstract: An automatic gain control loop for a radio receiver, comprising a switchable lowpass filter (21) to reduce distortions in an analogue gain control signal (6) by switching said switchable lowpass filter (21) to a low time constant in case a change of a gain control signal (6) of the automatic gain control loop lies above a predetermined threshold, which low time constant is lower than a normally used time constant, comprises a hold unit (24) which affects that said switchable lowpass filter (21) uses said low time constant a predetermined time after a change of the gain control signal (6) of the automatic gain control loop lies below said predetermined threshold.