Abstract:
A center frequency adjustment device for a communications receiver includes an A/D converter coupled to an analog filter in the communications receiver for converting an output signal of the analog filter to a digital signal, a carrier frequency offset estimator coupled to the A/D converter for estimating a carrier frequency offset of the communications receiver according to the digital signal, and a control circuit coupled to the analog filter and the carrier frequency offset estimator for adjusting a center frequency of the analog filter according to the carrier frequency offset.
Abstract:
A method and device for calibrating in-phase and quadrature-phase (IQ) mismatch. The device is used in a direct down-conversion circuit of a communication system. The device has a first mixer for mixing an RF signal with a first carrier signal, so as to generate an in-phase analog signal; a second mixer for mixing the RF signal with a second carrier signal, so as to generate a quadrature-phase analog signal; an operation unit for executing a Least Mean Square (LMS) algorithm and thereby generating a compensation signal according to the in-phase analog signal and the quadrature-phase analog signal; and a calibration unit for compensating the in-phase analog signal and the quadrature-phase analog signal according to the compensation signal, so as to calibrate the IQ mismatch between the in-phase analog signal and the quadrature-phase analog signal.
Abstract:
A method and an apparatus of IQ mismatch calibration in a radio communication system. The method includes receiving a radio frequency signal, mixing the radio frequency signal with a first carrier to generate an In-phase analog signal, mixing the radio frequency signal with a second carrier to generate a Quadrature-phase analog signal, detecting a phase offset between the In-phase analog signal and the Quadrature-phase analog signal, computing at least a tuning parameter according to the phase offset, and calibrating at least one of the In-phase analog signal and the Quadrature-phase analog signal according to at least one of the phase offset and the tuning parameter such that the In-phase analog signal and the Quadrature-phase analog signal are orthogonal after calibration.
Abstract:
A low drop-out (LDO) voltage regulator with efficient frequency compensation is disclosed. The LDO voltage regulator includes an error amplifier, a transmission element, a voltage divider and a pole control unit. The error amplifier generates a control signal according to a reference voltage and a feedback voltage. The transmission element is coupled to the error amplifier, and adjusts an input voltage to generate an output voltage according to the control signal. The voltage divider is coupled to the transmission element, and performs a voltage division operation on the output voltage to generate the feedback voltage. The pole control unit is coupled to the transmission element, and provides and adjusts an output capacitor of the LDO voltage regulator to fix a frequency of a pole according to variation of an output impedance of the transmission element, so as to maintain loop stability.
Abstract:
A signal strength detecting device of a communication system is disclosed. The signal strength detecting device is coupled to a frequency down mixer of the communication system and the frequency down mixer is used for receiving and converting a first signal to a second signal whose frequencies are lower than frequencies of the first signal. The signal strength detecting device comprises a frequency up converter for receiving and converting the second signal to a third signal whose frequencies are higher than the frequencies of the second signal and a detecting unit for detecting strength of the third signal and generating a signal strength indicator to the communication system according to a detecting result corresponding to the strength of the third signal, wherein the signal strength indicator represents the strength of the first signal received by the frequency down mixer.
Abstract:
The present invention provides an apparatus for enhancing Q factor of an inductor. The apparatus includes a negative resistance generator coupled to the inductor for providing a negative resistance, and a bias circuit coupled to the negative resistance generator for biasing the negative resistance generator.
Abstract:
A low noise amplifier for operating in response to different gain modes is disclosed. The low noise amplifier includes a voltage adjusting circuit, which provides a first bias voltage at a first gain mode and provides a second bias voltage at a second gain mode, where the second bias voltage is different from the first bias voltage; and an amplifying circuit coupled to the voltage adjusting circuit, for providing a first transfer characteristic according to the first bias voltage during the first gain mode in order to amplify an input signal to generate an output signal, and for providing a second transfer characteristic according to the second bias voltage during the second gain mode in order to amplify the input signal to generate the output signal.
Abstract:
An apparatus and a method for calibrating IQ mismatch to ensure that an in-phase oscillating signal and a quadrature-phase oscillating signal are orthogonal to each other. The apparatus includes a mixer for mixing the in-phase oscillating signal with the quadrature-phase oscillating signal to generate an output signal, a control module for determining a control signal according to a low-frequency component of the output signal, and a phase adjusting module for adjusting the phase of a specific oscillating signal to ensure that the in-phase oscillating signal and the quadrature-phase oscillating signal are orthogonal to each other. The specific oscillating signal may be the in-phase or the quadrature-phase oscillating signal. The apparatus does not require a digital signal-processing unit to perform complex calculations nor requires additional oscillating sources for calibration. Hence, the circuit design is much simplified, and the consumption of system resources is significantly reduced.
Abstract:
A multi-band receiver is disclosed. The multi-band receiver includes a low-noise amplifier (LNA) and a mixer. The LNA includes a switched receiving circuit, a loading circuit, and a switching circuit. The switched receiving circuit has a first receiving circuit for receiving a first signal corresponding to a first frequency, and a second receiving circuit for receiving a second signal corresponding to a second frequency. The loading circuit is utilized for providing a specific load to the switched receiving circuit. The switching circuit is used for controlling whether the first signal or the second signal is transferred to the loading circuit. The mixer is coupled to the low-noise amplifier for receiving an output signal generated from the LNA and for down-converting the output signal.
Abstract:
A variable gain amplifying circuit, which applies a resistor ladder to obtain a more precise gain, is disclosed. The amplifying circuit includes an input, an operational amplifier (op-amp), a resistor unit and a feedback resistor. The feedback resistor is coupled between an output and an inverting input of the op-amp. The resistor unit includes at least one resistor ladder. The resistor unit further includes a switching unit for controlling whether the at least one resistor ladder is coupled between the input of the amplifying circuit and the inverting input of the op-amp. A differential amplifying circuit for more precise gain adjustment is also disclosed.