A code acquisition module for a direct sequence spread spectrum (DSSS) receiver includes: a Sparse Discrete Fourier transform (SDFT) module configured to perform an SDFT on a finite number of non-uniformly distributed frequencies comprising a preamble of a received DSSS frame to calculate Fourier coefficients for the finite number of non-uniformly distributed frequencies; a multiplier configured to multiply the Fourier coefficients for the finite number of non-uniformly distributed frequencies of the received DSSS frame by complex conjugate Fourier coefficients for the finite number of non-uniformly distributed frequencies to generate a cross-correlation of the received DSSS frame and the complex conjugate Fourier coefficients; and a filter module configured to input the cross-correlation and output a delay estimation for the received DSSS frame.

High-performance ultra-wideband Phased Array Antennas (PAA) are disclosed, having unique capabilities, enabled through photonic integrated circuits and novel optical architectures. Unique capabilities for PAA systems are enabled by photonic integration and ultra-low-loss waveguides. Novel aspects include optical multiplexing combining wavelength division multiplexing and/or a novel extension to array photodetectors, providing the capability to combine many RF photonic signals with very low loss. Architectures include tunable optical up-conversion and down-conversion systems, moving a chosen frequency band between baseband and a high RF frequency band with high dynamic range. Simultaneous multi-channel RF beamforming is achieved through power combining/splitting of optical signals.

A radio frequency (RF) photonic equalizer may include a first electro-optic (E/O) modulator configured to modulate an optical carrier based upon an RF input signal, a stimulated Brillouin scattering (SBS) medium coupled to the first E/O modulator, and a second E/O modulator configured to modulate the optical carrier based upon an equalizing function waveform. An optical circulator may be coupled to the SBS medium and the second E/O modulator, and a photodetector may be coupled to the optical circulator.

A system has a plurality of non-linear circuit stages and an intervening linear circuit stage. An input signal is provided to a first non-linear circuit stage, and from the first non-linear circuit stage, to the linear circuit stage. The first non-linear circuit stage applies a second-order distortion to the input signal and provides the resulting signal to the linear circuit stage. The resulting signal that is output from the linear circuit stage is inverted with respect to the input signal and suitably linearly processed (attenuated or amplified). This signal is then provided to a second non-linear circuit that applies a second-order distortion and outputs a signal that has an overall reduction in second-order distortion.

A method of interference suppression with intermodulation distortion mitigation includes processing an RF signal comprising an RF signal of interest and an RF interfering signal to produce a first and second RF drive signal each with a desired RF interference signal power and having a 90 degree relative phase. The first RF drive signal is imposed onto a first optical signal with a modulator to generate a first modulated optical signal so that the modulator has a large-signal behavior that is characterized by a Bessel function of the first kind J.sub.1(), wherein the desired power at a frequency of the interference signal of the first drive signal is chosen to correspond to a zero of the Bessel function of the first kind J.sub.1(). The second RF drive signal is imposed onto a second optical signal with a modulator to generate a second modulated optical signal so that the modulator has a large-signal behavior that is characterized by a Bessel function of the first kind J.sub.1(), wherein the desired power at a frequency of the interference signal of the second drive signal is chosen to correspond to another zero of the Bessel function of the first kind J1(b). The first and second modulated optical signal are combined with an optical power ratio that is selected to suppress third-order intermodulation distortion products in an electrical signal generated by detecting the optically combined first and second modulated optical signals.

Methods and apparatus for reducing and/or canceling signal interference between receiver and transmitter components of a wireless communications device are described. The methods and apparatus are well suited for use in a wide range of devices including user equipment devices such as cell phones as well as in network equipment such a base stations. Opto-mechanical devices are used in some embodiments as part of an apparatus which performs interference cancellation on RF (Radio Frequency) signals.

The present invention reduces the level of optical reflections created in a photonic integrated circuit (PIC) going back into an integrated laser through Reflection Engineering; optimizing the phase/timing and position of optical reflections inherent to a PIC design while adding engineered reflections to the PIC to allow inherent reflections to be reduced or eliminated. The Wavelength Division Multiplexed (WDM) geometric optical isolator of the present invention combines an array of closely spaced WDM lasers with an array of modulators in a novel geometry in order to provide effective optical isolation of the lasers.

A photonic integrated circuit (PIC) provides a common architecture to feed both optical and RF phased arrays that may be used for missile guidance, mobile data links, autonomous vehicles and 5G cellular communications. A plurality of switches are monolithically fabricated on the PIC with the optical feed network to switch the optical power of the phase-modulated optical channel signals between the integrated optical antennas and the RF antennas to produce steerable optical and RF beams. The photo-detectors and RF antennas may be discrete components or integrated with the optical feed network.

A spread spectrum receiving method receives a spread spectrum signal. An optical signal frequency comb is generated. Modes of the optical signal frequency comb are modulated with a received spread spectrum signal. An optical local oscillator comb is generated that is mutually coherent with the signal frequency comb. A code word is applied to the local oscillator comb. The combs are combined and the received spread spectrum signal is detected from the combined combs.

A system for Nyquist zone disambiguation of a received broadband RF signal is disclosed. The system includes continuous-wave (CW) and pulsed photonic sources whose outputs may be combined into a single input. Both CW and pulsed components of the combined photonic input are modulated by sampling the received RF input signal. The system includes hybrid couplers for IQ demodulation of the modulated combined photonic signal. The system demultiplexes the demodulated inphase and quadrature differential photonic signals into their CW and pulsed component signals. The pulsed component signals may be digitized by narrowband multibit analog-digital converters (ADC) while the CW component signals are digitized by high speed low latency mono-bit ADCs to determine frequency components (e.g., bandwidth information) and other spectrum information of the RF input signal.