Allan C Ward

US Patent:

6476957, Nov 5, 2002

Filed:

Jul 17, 2000

Appl. No.:

09/620324

Inventors:

Allan Ward - Alexandria VA
Keith J. Williams - Accokeek MD
Paul D. Biernacki - Alexandria VA
Lee T. Nichols - Springfield VA

Assignee:

The United States of America as represented by the Secretary of the Navy - Washington DC

International Classification:

G02F 135

US Classification:

359326, 333167, 333176

Abstract:

An image rejecting microwave photonic downconverter uses a microwave sub-carrier modulation technique without concern for image frequency interference in the shifted signal, thereby allowing telecommunications systems to downconvert densely multiplexed communications channels into a low frequency band where conventionqal electronics can perform signal-processing functions. The image rejecting microwave photonic downconveter incoming microwave signals can be processed without ambiguity in direction finding applications, allowing remotable, multioctave microwave signal processing for frequency and phase determination. A first laser providing an optical carrier that is modulated by a first electro-optic modulator with a sinusoidal electrical signal generated by a first local oscillator and a second laser providing optical carrier that is modulated by a second electro-optic modulator with a sinusoidal electrical signal generated by the second local oscillator for a signal generated by a second local oscillator; are transmitted independently through two polarization-maintaining (PM) optical fibers of arbitrary length to a distant point. There the first modulated optical signal is converted to an electrical domain and mixed with an input from an ultra-broadband radio frequency (RF) antenna receive-array, shifting the entire RF band to a higher frequency band equal to the original RF signal plus the modulated optical frequency signal.