A highly flexible and accurate beam-forming system for direct IF receivers that leverages continuous-time bandpass delta sigma modulators (CTBPDSMs) and bit-stream processing has been developed at the Electrical Engineering and Computer Science at the University of Michigan.
The aforementioned beam-forming system implements beam-forming in the oversampled bit-stream domain by directly processing the unfiltered outputs of the CTBPDSMs. Oversampled signals are filtered and decimated for further digital signal processing (DSP) in conventional oversampling ADC-based receivers. The approach enables a multiplier-less implementation of down-mixing and complex weight multiplication (CWM) with only multiplexers; this reduces circuit complexity and area compared to analog beam-forming schemes.
Programmable 7-bit beam-forming weights provide reconfigurability with a resolution of 1.4 degrees. The output from each CTBPDSM channel has 51dB of SNDR on average, whereas combined channels create a beam-formed output with 57dB of SNDR, an improvement of 6dB. The 1.04x1.04mm2 chip in 65nm CMOS consumes 71.2mW, while the core occupies only 0.15mm2.
- Wireless communication
- Detection and ranging operations
- CMOS-based chip
- Reconfigurable design
- High resolution
- Improved performance
- Low area
- Low power