Methods and apparatuses for downconverting high frequency subbands and isolating signals therein

Abstract

Methods and apparatuses for downconverting high frequency subbands to a lower frequency band and recovering signals-of-interest. The system includes a controller, a signal generator, an optical source, a dual-drive mach zehnder modulator (DDMZM), a photodetector, and a dechipping/image (DI) rejector. The controller outputs chipping frequencies to the signal generator which generates local oscillator (LO) tones shifted by the respective chipping frequencies. The optical source outputs an optical signal to the DDMZM which has first and second arms and modulators. The first modulator receives a signal from a source and modulates it onto the optical signal propagating through the first arm to form a first modulated optical signal. The second modulator receives the shifted local oscillator tones and modulates them onto the optical signal propagating through the second arm to form a second modulated optical signal. The DDMZM outputs a signal which is a combination of the first and second modulated optical signals to the photodetector which generates a corresponding electrical signal. The dechipping/image (DI) rejector receives the electrical signal and one of the chipping frequencies and outputs a signal that maximizes signals in one high frequency subband while suppressing signals in other high frequency subbands.