Delta Modulation Technique for Improving the Sensitivity of Monobit Subsamplers in Radar and Coherent Receiver Applications

Journal Article · Fri Aug 01 00:00:00 EDT 2014 · IEEE Transactions on Microwave Theory and Techniques

DOI:https://doi.org/10.1109/TMTT.2014.2332433· OSTI ID:1140866

Rodenbeck, Christopher T. ^[1]; Tracey, Keith J. ^[1]; Barkley, Keith R. ^[1]; DuVerneay, Brian B. ^[1]

---

1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

This paper introduces a technique for improving the sensitivity of RF subsamplers in radar and coherent receiver applications. The technique, referred to herein as “delta modulation” (DM), feeds the time-average output of a monobit analog-to-digital converter (ADC) back to the ADC input, but with opposite polarity. Assuming pseudo-stationary modulation statistics on the sampled RF waveform, the feedback signal corrects for aggregate DC offsets present in the ADC that otherwise degrade ADC sensitivity. Two RF integrated circuits (RFICs) are designed to demonstrate the approach. One uses analog DM to create the feedback signal; the other uses digital DM to achieve the same result. A series of tests validates the designs. The dynamic time-domain response confirms the feedback loop’s basic operation. Measured output quantization imbalance, under noise-only input drive, significantly improves with the use of the DM circuit, even for large, deliberately induced DC offsets and wide temperature variation from -55°C to +85 °C. Examination of the corrected vs. uncorrected baseband spectrum under swept input signal-tonoise ratio (SNR) conditions demonstrates the effectiveness of this approach for realistic radar and coherent receiver applications. In conclusion, two-tone testing shows no impact of the DM technique on ADC linearity.

• Research Organization: Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC04-94AL85000
• OSTI ID: 1140866
• Report Number(s): SAND2014-2348J; 505919
• Journal Information: IEEE Transactions on Microwave Theory and Techniques, Vol. 62, Issue 8; ISSN 0018-9480
• Publisher: IEEE
• Country of Publication: United States
• Language: English

Related Subjects

47 OTHER INSTRUMENTATION
Analog-to-digital conversion
Doppler radar
RF integrated circuits (RFICs)
coherent receivers
sampled data circuits