Analysis and Dynamic Range Enhancement of the Analog-to-Digital Interface in Multimode Radio Receivers

The 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.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Electrical and Computer Engineering

Department dc:contributor.department

Electrical and Computer Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

1997

Author dc:creator

• Fox, Brian L.

Chair dc:contributor.committeechair

• Reed, Jeffrey H.

Committee members dc:contributor.committeemember

• Woerner, Brian D.
• Bostian, Charles W.

• Digital Receivers
• A/D Conversion
• A/D Converter Distortion
• Software Radio
• Cellular Radio

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

etd-113117281975580

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/35868