This paper introduces a frequency agile RF filter for interference attenuation in a base station RF frontend. Digital and RF systems are combined in a feed-forward architecture. This architecture provides a frequency response with multiple tunable transfer function zeros. This feed-forward architecture is called the hybrid RF-DSP feed-forward filter. Measurements demonstrate successful interferer suppression for operation at several bands between 800 and 1800 MHz. The group delay mismatch between the feed-forward paths is reduced with a delay line to achieve between 32 to 24 dB of attenuation for interferers with bandwidths from 1 to 8 MHz. The digital filter used within the prototype had 32 complex taps, thereby providing the RF filter with 32 tunable transfer function zeros.

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Keywords Active filters, feed-forward, interference cancellation, mixed signal, tunable filter
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Conference 2012 6th IEEE Radio and Wireless Week, RWW 2012 - 2012 IEEE Radio and Wireless Symposium, RWS 2012
Wyville, M.W. (Mark W.), Smiley, R.C. (Russell C.), & Wight, J. S. (2012). Frequency agile RF filter for interference attenuation. In RWW 2012 - Proceedings: IEEE Radio and Wireless Symposium, RWS 2012 (pp. 399–402). doi:10.1109/RWS.2012.6175382