A low-power digital frequency synthesizer combining direct digital frequency synthesis techniques with serrodyne frequency translation principles to produce a wideband frequency response with high spectral purity. A conventional direct digital synthesizer is used to generate a high-resolution analog carrier signal from a low-speed digital clock signal. The carrier signal is phase modulated by a low-resolution signal generated from a high-speed digital clock signal. The modularity signal is a higher frequency signal than the carrier signal. The phase modulation is accomplished by exact decoded attenuators. The spectral purity of the resulting high-resolution output signal is unobtainable by conventional direct digital synthesizers, while providing significant power savings.

Composite direct digital synthesizer

A Baseband Radio Over Fiber (BROF) architecture is proposed, where upto four Radio Frequency (RF) carriers can be generated, while using the heterodyne photo-detection of only two optical signals. This proposed BROF architecture has a star-like structure and it is composed of six Radio Access Units (RAUs), where data is transmitted from the Central Unit (CU) to the Base Station (BS) and from the BS to the RAU over a distance of 20 Km and 0.3 Km, respectively, at a rate of 768 Mbps. The performance of the system supporting four carrier frequencies drops by at most 1dB, at a BER of 10-9, compared to conventional heterodyne photo-detection.

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Baseband Radio over Fiber Aided Millimeter-Wave Distributed Antenna for Optical/Wireless Integration

The design of a 6 to 18 GHz serrodyne modulator is described. It consists of a P-I-N diodes based all passive eight step phase shifter. The device is digitally controlled. Experimental data and a comparison with a conventional serrodyne TWT are presented.

An Eight - Phase Broadband Serrodyne Modulator

This correspondence considers the use of a stepped phase shifter as an approximation to continuous phase shifting for serrodyne frequency translation. Variations in translation loss and suppression of undesirable components as a function of the number of steps used is presented.

M. Greenbaum

Papers

Serrodyne Frequency Translation Using Stepped Modulation Waveforms