Type of Document Master's Thesis Author Fox, Brian L. Author's Email Address email@example.com URN etd-113117281975580 Title Analysis and Dynamic Range Enhancement of the Analog-to-Digital Interface in Multimode Radio Receivers Degree Master of Science Department Electrical and Computer Engineering Advisory Committee
Advisor Name Title Reed, Jeffrey Hugh Committee Chair Bostian, Charles W. Committee Member Woerner, Brian D. Committee Member Keywords
- Digital Receivers
- A/D Conversion
- A/D Converter Distortion
- Software Radio
- Cellular Radio
Date of Defense 1997-02-01 Availability unrestricted AbstractThe rapidly developing wireless market has spawned a multitude of
different standards for cellular, PCS, and wireless data. To allow users
the ability to access services conforming to disparate standards,
multimode handsets capable of software reconfiguration are needed.
These "software radios" are distinguished from their traditional
counterparts by their strong reliance on digital channel filtering and
demodulation which may be reprogrammed to receive different
standards. In these radios, higher dynamic range is required from the
analog portion, most notably, the analog-to-digital converter (ADC).
This research examines through analysis and simulation the
performance requirements of analog-to-digital converters for use in
radios which are conformant to the AMPS, IS-54, GSM, and IS-95
cellular standards. Simulations reveal the degradation in performance
under conditions of off-channel interference, fading, and converter
nonlinearities. Included in this analysis is the design of automatic gain
control (AGC) for narrowband and IS-95 spread spectrum systems to
optimize quantization noise and distortion due to A/D overload. Lastly,
methods for improving the dynamic range of the analog-to-digital
interface such as nonuniform quantization, companding, and dither are
presented. The development of a novel A/D using a direct-sequence
pseudo-noise (DSPN) technique in conjunction with an asymmetrical
quantizer is presented and compared with standard dither techniques.
Advantages of this technique compared to ordinary ADC's include an
almost one bit improvement in resolution, quantization noise whitening,
elimination of A/D offsets, and the ability to simultaneously digitize
multiple analog signals with a single quantizer. The technique requires
no synchronization and is easily implemented.
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