Abstract: The present invention is a quadrature VLIF receiver, including calibration circuitry, and methods to closely match signal processing of an in-phase signal path and a quadrature-phase signal path to optimize VLIF image rejection. The calibration circuitry includes a variable gain variable-phase calibration signal generator, a variable gain amplifier for each signal path, phase adjustment circuitry for each signal path, and switching circuitry to support calibration steps. The calibration signal generator supplies a calibration signal at the same frequency as mixer local oscillator signals; therefore, during calibration, all signals downstream of the VLIF mixer are at DC, which simplifies calibration measurements, thereby minimizing calibration times.

Abstract: The present invention is a quadrature multi-mode RF receiver that uses a single quadrature mixer for tuning to desired frequency bands. In a direct conversion mode of operation, the RF receiver down converts a received RF signal directly into a baseband signal. In a VLIF mode of operation, the RF receiver down converts a received RF signal into a VLIF signal. When receiving a wanted RF signal, the frequency of the resulting VLIF signal is called the wanted VLIF frequency, and is based on the signal strength of the received RF signal. In one embodiment of the present invention, the wanted VLIF frequency is selected to be one of two VLIF frequencies. The wanted VLIF frequency is inversely related to the signal strength of the received RF signal.

Abstract: A variable load circuit for adjusting a phase of a differential signal including a first transistor having a first terminal adapted to receive a first component of the differential signal, a second transistor having a first terminal adapted to receive a second component of the differential signal and a second terminal coupled to a second terminal of the first transistor, and a variable current source coupled to a third terminal of both the first and second transistors. The variable current source generates a bias current based on a control signal. For each of the first and second transistors, a first capacitance is created between the first and second terminals, and a second capacitance is created between the first and third terminals. The first and second capacitances are each a function of the bias current and thus the control signal and operate to adjust the phase of the differential signal.

Abstract: The present invention is a differential transconductance amplifier circuit that includes matched cross-coupled transconductance elements connected such that the differential gain of the amplifier is determined by only passive elements. By virtually eliminating the effects of active elements on the amplifier gain, the amplifier operates in a very linear manner over its entire operating range. Power consumption, amplifier noise level, and dynamic range can be optimized with appropriate selection of the passive elements that determine amplifier gain.