Programmable Order Multiple Feedback BandPass ActiveRC filter for FSK Transceiver An integrated programmable order multiple feedback (MFB) bandpass filter (BPF) implemented in 0.14 um CMOS technology is presented. The modular single ended filter has been used in an FSK transceiver, in both receiver (RX) and transmitter (TX). It is implemented by cascading different types of BP filters with different required bandwidth (BW) of RX and TX. A combination of Bessel and Butterworth filters to maximize stopband rejection, optimize inband flatness and minimize group delay variation is used. Each stage of the MFB filter draws 0.3mA of current from a 1.8V supply. A simple and efficient approach to trim center frequency which has minimum impact on area and parasitic components has been used. AC gain change of TX due to mismatches, parasitic and process and trimming has been compensated by a simple gain stage while it is budgeted in RX system SNR. The implemented 23.2MHz center frequency filters have been used in the FSK transceiver of a USB power delivery (PD) system, with a BW of 3.46MHz for RX filter and a BW of 1.3MHz for TX filter. The employed low current and small area architecture with its efficient trimming strategy meets the required performance of the FSK transceiver.

Flat PassBand Method with Two RC BandStop Filters for 4Stage Passive RC Polyphase Filter in LowIF Receiver Systems This paper proposes a flat passband for a 4stage passive RC polyphase filter in a bluetooth lowIF receiver system; there the bandwidth is 8MHz, the center IF frequency is 4MHz, and the required image rejection ratio is u003c30dB. Based on the superposition principle, the transfer function of this filter is derived. As the input signals are the wanted signals, there are two local maximum values which are calculated based on CauchySchwarz inequality theorem at 160kHz (1.24dB) and 40MHz (1.24dB). Therefore, two RC bandstop filters are used to improve the passband of these local maximum values (improvement of the ripple gain of passband from 2dB into 0.47dB). As a result, a 4stage passive RC polyphase filter for a lowIF receiver is designed, where an image rejection ratio is 36dB, and the passband gain is flat (the ripple gain is 0.47dB).