Theta Microelectronics, Inc.

Spyros Pipilos

A wireless local area network receiver having separate automatic gain control (AGC) loops for providing a radio frequency AGC and a baseband frequency AGC, as well as a DC offset cancellation circuit. The AGC loops control a low noise amplifier amplifying the received RF signal, and the baseband signal or signals from a mixer of I and Q mixers. The DC offset compensation loop is also responsive to the baseband AGC signal to maintain a substantially fixed gain in the DC offset compensation feedback. Details of various embodiments are disclosed, including embodiments for orthogonal frequency division multiplexing (OFDM) that provide the AGC operation and the DC offset cancellation to the desired levels within the relatively short period of a preamble that precedes the data transmission.

Wireless LAN receiver with I and Q RF and baseband AGC loops and DC offset cancellation

Apparatus and methods for eliminating DC offset in a wireless communication device operable on a continuous basis or on a sampled basis. In a receive channel, the output of a forward variable gain amplifier is fed back to an RC circuit to charge the capacitor (C) to a voltage dependent on the DC offset in the variable gain amplifier output. The voltage on the capacitor is amplified and summed with the input to the variable gain amplifier. The RC circuit is configured to provide a high gain feedback at DC and very low frequencies, but very low gain at signal frequencies. Preferably the output of the forward variable gain amplifier is fed back to the RC circuit with a gain that is inversely proportional to the forward gain. Disconnection of the capacitor and feedback of the capacitor voltage provides sampled operation. Various embellishments and sample applications are disclosed.

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Athens, Greece

Spyros Pipilos