Digital local-oscillator generation using a delta-sigma technique

Abstract

Local-oscillator (LO) signals in up/down converters for most radar systems are typically generated using synthesizers, bench sources, custom-built frequency sources or direct-digital synthesis (DDS). In a digital-array radar (DAR) concept, a single-bit delta-sigma (/spl Delta/-/spl Sigma/) technique is considered as a viable alternative to encode sine waves digitally for LO signal generation. This technique is applied to synthesize sinusoidal signals at a low frequency. These signals are then injected into a frequency multiplier system for generating LO signals. When independently coded /spl Delta/-/spl Sigma/ sine waves are created offline on a per element basis for a phased array system, the in-band noise shaped response improves as a result of digital beam forming (DBF). In this paper, a single-bit encoding technique for LO signal generation is discussed. Some simulation results are provided as well as a candidate microwave design for a frequency multiplier system.