University of Macau

Rui P Martins

Pui-In Mak

Seng-Pan U

Ka-Fai Un

Chak-Fong Cheang

Wei-Han Yu

A digital calibration circuit is used to provide joint-elimination of transmitter and receiver I/Q imbalances. Digital I and Q quadrature signals are received and converted to analog I and Q quadrature signals on I and Q for transmission on output channels. An output mixer is used to convert the quadrature signals to an unbalanced RF output. An unbalanced RF signal is received selectively either externally or from the RF output using a source follower, and the received signal is mixed to provide analog I and Q quadrature signals, using a local oscillator (LO). The LO adds an additional 90 &#xb0; phase shift between I and Q quadrature channels of the unbalanced RF input. Parameter estimating the transmitted digital I and Q quadrature signals and providing estimations of I and Q quadrature imbalance conditions.

Non-recursive digital calibration for joint-elimination of transmitter and receiver I/Q imbalances with minimized add-on hardware

A switched current resistor (SCR) PGA for constant-bandwidth gain control includes an inverting amplifier, a feedback resistor forming a feedback loop between an output side and an input side of the inverting amplifier, and a switched current resistor (SCR) array connected in parallel to the feedback resistor, and configured to tune a gain range between a maximum and a minimum. The SCR array includes a plurality of switched resistors, each comprising a switch in series with a resistor. When the plurality of switched resistors are switched by a gain-control logic, a plurality of switched current sources and a plurality of grounded resistors are switched correspondingly to deliver a transient current, an equivalent of which flows through the plurality of grounded resistors out from the input side of the inverting amplifier, leading to a feedback factor of the PGA being constant.

Switched current resistor programmable gain array for low-voltage wireless LAN and method using the same

An amplifier circuit includes a transconductance amplifier at an input side of the amplifier circuit, a transimpedance amplifier connected to an output of the transconductance amplifier, and a voltage amplifier connected to an output of the transimpedance amplifier. The transconductance amplifier and the transimpedance amplifier form a low-impedance node at an interface thereof. A feedback circuit is connected between an output of the voltage amplifier and the low-impedance node between the transconductance amplifier and the transimpedance amplifier. The transconductance amplifier, the transimpedance amplifier, and the voltage amplifier form a main amplifier stage. The feedback circuit senses an imbalance in an output of the main amplifier stage, whereby a correction signal is integrated and negatively fed back to the low-impedance node between the transconductance amplifier and the transimpedance amplifier.

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Macau, China

Rui P Martins