Direct conversion receiver

Telecommunications – Receiver or analog modulated signal frequency converter – Local control of receiver operation

Reexamination Certificate

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Details

C455S312000, C455S324000

Reexamination Certificate

active

07856218

ABSTRACT:
In a direct conversion receiver, to cancel a DC offset generated in the baseband processing block, negative feedback arrangements comprising a gain control amplifier and a low-pass filter are respectively attached to the I and Q signal branches of the baseband block following mixer outputs. The gain control amplifier in each negative feedback circuit is gain adjusted so that the product G·B of the gain G of a primary gain control amplifier and its own gain B will be constant and thereby the DC offset is cancelled. This DC offset cancellation can be applied in a continuous receiving system with no intermittent time during a receiving operation. Capacitance elements located off-chip can be reduced to those to be used only in the low-pass filters in the negative feedback circuits, whereas many off-chip capacitance elements have been required to be inserted between each stage of gain control amplifiers in conventional baseband chains.

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Harald Pretl, Werner Schelmbauer, Robet Weigel, Richard Hagelauer, Bernd Adler and Josef Fenk, “Circuit and system Considerations for UMTS Xero-IF Receivers in SiGe BiCMOS”, Microwave Workshop Digest (2001), pp. 264-268.
Japanese Office Action dated Dec. 18, 2007, in Japanese and English.

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