Pulse or digital communications – Equalizers – Automatic
Reexamination Certificate
2002-05-21
2010-11-16
Ha, Dac V (Department: 2611)
Pulse or digital communications
Equalizers
Automatic
C375S236000, C375S350000, C708S300000, C455S067110
Reexamination Certificate
active
07835434
ABSTRACT:
The invention relates to an adaptive Radio Frequency (RF) filter (11), which is particularly useful as an RF filter in Wireless Local Area Networks (WLAN's). As greater demands are placed on RF systems, for example in WLAN's in order to increase channel capacity by utilizing available bandwidth, corresponding demands are placed upon performance and tolerance of components used in FR circuits. An adaptive Radio Frequency (RF) filter for filtering first and second RF signals from an OFDM encoded carrier signal is provided, the adaptive RF filter comprises: a low-pass filter (102) configured to filter first and second RF signals, one from another, so as to provide a first RF output signal; the adaptive RF filter being tunable in response to one or more input signals, the at least one input signal being derived from a comparator (37,100), which compares the first RF output signal with a desired value for said first RF output signal, and provides a connection factor for varying a characteristic of the filter (102). An advantage of the invention is that it facilitates filter of two OFDM encoded RF signals, the first typically at 8.1 MHz and the second (unwanted) at 11.9 MHz, from a base-band signal, with a noise floor level of —55 dB or better. Another advantage is that the filter is able to self calibrate and is able to take into account fluctuations which may affect performance, for example thermal drift, and automatically trim its characteristics so as to compensate for these fluctuations.
REFERENCES:
patent: 5146470 (1992-09-01), Fujii et al.
patent: 6269165 (2001-07-01), Stott
patent: 6633894 (2003-10-01), Cole
patent: WO 00/28664 (2000-05-01), None
patent: WO 01/28310 (2001-04-01), None
Khorramabadi et al.., “FA 10.6: Baseband Filters for IS-95 CDMA Receiver Applications Featuring Digital Automatic Frequency Tuning,” ISSCC96/Session 10/ Low-Power & Communication Signal Processing/ Paper FA 10.6, 1996 IEEE International Solid-State Circuits Conference, pp. 172, 173 & 439.
PCT International Search Report PCT/EP02/05607.
Gercekci Anil
Huynh Thien Luong
Newton Anthony David
Freescale Semiconductor Inc.
Ha Dac V
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