Simple photonics-based angle of arrival and Doppler frequency shift measurement system for long baseline antennas.

Using photonics to measure the characteristics of an RF signal has a number of advantages compared to electronics. As a result, many photonics-based RF signal measurement systems have been reported. However, none of them can simultaneously measure an RF signal angle-of-arrival (AOA) and Doppler frequency shift (DFS) while having a simple and low-cost structure that is suitable for use in a long baseline antenna array.

All-optical instantaneous RF signal frequency measurement system based on a linear ACF with a steep slope.

A new microwave photonic structure for measuring the frequency of an RF signal, to the best of our knowledge, is presented. The frequency of an unknown RF signal can be determined by simply measuring the system output optical powers. The proposed frequency measurement system can be designed so that the ratio of the two system output optical powers as a function of the RF signal frequency or the amplitude comparison function (ACF) has a steep linear slope over a wide frequency range.

All-optical high-order subharmonic mixer with a high signal-to-noise ratio and stable performance.

A photonics-based high-order subharmonic mixer, which enables a low-frequency LO source to be used for high-frequency RF signal frequency downconversion, is presented. It is based on an optically injected semiconductor laser, which is oscillated in the period-one state, sandwiched between two optical phase modulators. It has the advantages of a simple and compact structure, wide bandwidth, absence of electrical components, reconfigurable subharmonic mixing operation, stable output IF signal performance, high signal-to-noise ratio, infinite LO-to-RF port isolation, and high LO-to-IF port isolation.

Wavelength switching technique for phase interrogation of Mach Zehnder interferometer-based optical sensors.

A method for determining the phase shift of a Mach Zehnder interferometer (MZI) is presented. It is based on switching the wavelength of continuous wave (CW) laser light illuminating the MZI and measuring the interferometer output amplitudes at DC and switching frequency. The method can measure the MZI phase shift unambiguously over the entire phase shift range of 2π.

Microwave frequency measurement based on a frequency-to-phase mapping technique.

A new frequency-to-phase mapping technique for measuring a radio-frequency (RF) signal frequency is presented. The concept is based on generating two low-frequency signals where their phase difference is dependent on the input RF signal frequency. Hence, the input RF signal frequency can be determined by using a low-cost low-frequency electronic phase detector to measure the phase difference between the two low-frequency signals.

Photonic microwave frequency divider with a tunable division ratio and harmonic suppression capability.

A photonic microwave frequency divider that is capable to realise tunable high order frequency division, is presented. It is based on injecting an RF phase modulated optical signal into an off-the-shelf DFB laser operating at period-N state. Optical frequency components with a frequency separation of 1/N times the input RF signal frequency are generated by the DFB laser.

Parity-time-symmetric optoelectronic oscillator based on higher-order optical modulation.

An optoelectronic oscillator (OEO) for single-frequency microwave generation, enabled by broken parity time (PT) symmetry based on higher-order modulation using a Mach-Zehnder modulator, is proposed and demonstrated. Instead of using two physically separated mutually coupled loops with balanced gain and loss, the PT symmetry is realized using a single physical loop to implement two equivalent loops with the gain loop formed by the beating between the optical carrier and the ±1-order sidebands and the loss loop formed by the beating between the ±1-order sidebands and the ±2-order sidebands at a photodetector. The gain and loss coefficients are made identical in magnitude by controlling the incident light power to the modulator and the modulator bias voltage.

Broadband microwave photonic frequency translator with a wide frequency shifting range.

A microwave photonic topology for shifting the frequency of an input microwave signal is presented. It operates based on a single sideband frequency mixing approach. The amount of microwave signal frequency shift is determined by a local oscillator frequency.

Multichannel microwave photonic based direction finding system.

A new microwave photonic topology for RF signal direction finding is presented. It is based on a dual-parallel Mach Zehnder modulator (DPMZM) in series with an optical phase modulator (PM). The direction of an RF signal received by the antennas connected to an RF port of the DPMZM and the PM can be determined from the power ratio of two system output low frequency components, without the need to know the incoming RF signal amplitude in advance.

Simple photonics-based system for Doppler frequency shift and angle of arrival measurement.

A novel photonic approach for simultaneously measuring both the Doppler frequency shift (DFS) and the angle of arrival (AOA) of a microwave signal in a radar system is presented. It has the same structure as a fiber optic link consisting of a laser, an optical modulator and a photodetector. The incoming microwave signal and a reference signal are applied to the optical modulator.

Cascaded modulator topology for frequency conversion in antenna remoting applications.

A new cascaded modulator structure that has the ability to realize high conversion efficiency microwave frequency downconversion, while at the same time able to overcome two fundamental limitations in the dual-parallel modulator approach, is presented. It is based on utilizing the polarization-dependent modulation efficiency property in LiNbO electro-optic modulators. The new structure allows the modulators for the RF signal and local oscillator (LO) modulation to be placed in different locations suitable for antenna remoting applications, and it has infinite isolation between the LO and RF signal ports.

Linearized fiber-optic link with a high spurious free dynamic range over a wide frequency range.

An all-optical linearized fiber-optic link is presented. It solves the problem in most reported structures where a high spurious free dynamic range (SFDR) can only be obtained in a limited frequency range. The link only involves a laser, an optical modulator, and a photodetector.

Broadband high dynamic range fiber optic link based on a dual-polarization modulator.

This paper presents a simple, linearized fiber-optic link that is capable of realizing a high spurious free dynamic range (SFDR) at different input RF signal frequencies without the need of readjusting system parameters. The link is based on a commercial dual-polarization modulator followed by a linear polarizer. The third-order nonlinearity at the third-order intermodulation distortion frequency can be cancelled by designing the angle of the linear polarizer.

Ultra-wide bandwidth photonic microwave phase shifter with amplitude control function.

This paper presents a new technique for realizing continuous 0°-360° RF signal phase shift over a very wide bandwidth. It is based on using single-sideband modulation together with optical filtering to largely suppress one of the RF modulation sidebands over a wide input RF frequency range, and controlling the phase of the optical carrier to shift an RF signal phase. The technique does not require expensive electrical or optical components to realize an RF signal phase shift over 2-40 GHz frequency range with a flat amplitude and phase response performance.

Photonic microwave quadrature filter with low phase imbalance and high signal-to-noise ratio performance.

A photonic microwave quadrature filter is presented. It has a very simple structure, very low phase imbalance, and high signal-to-noise ratio performance. Experimental results are presented that demonstrate a photonic microwave quadrature filter with a 3 dB operating frequency range of 10.

Photonic microwave phase shifter based on dual-sideband phase-control technique.

An all-optical photonic microwave phase shifter that can realize a continuous 0°-360° phase shift is presented. The phase-shifting operation is implemented by controlling the phase of the two RF phase-modulation sidebands while keeping the optical carrier phase fixed. The use of two RF modulation sidebands, instead of a single sideband used in most conventional phase shifters, has the advantage of high-output RF signal power, and consequently high signal-to-noise ratio performance.

Instantaneous high-resolution multiple-frequency measurement system based on frequency-to-time mapping technique.

A new microwave photonic instantaneous frequency measurement system that can simultaneously measure multiple-frequency signals while achieving very high resolution and wide frequency measurement range is presented. It is based on the frequency-to-time mapping technique implemented using a frequency shifting recirculating delay line loop and a narrowband optical filter realized by the in-fiber stimulated Brillouin scattering effect. Experimental results demonstrate the realization of a multiple-frequency measurement capability over a frequency range of 0.

Microwave photonic mixer with high spurious-free dynamic range.

A new linearized photonic mixer structure, which can fully eliminate the third-order intermodulation distortion, is presented. It is based on an integrated dual-parallel Mach-Zehnder modulator to which an optimized RF split and an optimized optical phase shift are applied, in series with a Mach-Zehnder modulator driven by the LO. The mixer achieves a very high spurious-free dynamic range performance, it enables essentially infinite isolation between the RF and LO ports, and it has the ability to function over a multioctave frequency range.

Microwave photonic mixer based on a single bidirectional Mach-Zehnder modulator.

A microwave photonic mixer based on a single electro-optic Mach-Zehnder intensity modulator operating in both directions is presented. In this mixer structure, the light from the optical source travels in opposite directions inside the modulator and is modulated by both the RF signal and the local oscillator (LO). The output optical spectrum comprises the RF signal and LO sidebands without the optical carrier.

Optical-to-RF phase shift conversion-based microwave photonic phase shifter using a fiber Bragg grating.

A novel microwave photonic phase shifter structure is presented. It is based on the conversion of the optical carrier phase shift into an RF signal phase shift via controlling the carrier wavelength of a single-sideband RF-modulated optical signal into a fiber Bragg grating. The new microwave photonic phase shifter has a simple structure and only requires a single control to shift the RF signal phase.

High conversion efficiency microwave photonic mixer based on stimulated Brillouin scattering carrier suppression technique.

A new microwave photonic mixer that can achieve a high conversion efficiency is presented. It is based on using the stimulated Brillouin scattering loss spectrum to suppress the optical carrier at the output of two optical phase modulators driven by the RF signal and the LO, respectively. Experimental results are presented, which demonstrate a high conversion efficiency of 11.

Tunable coherence-free microwave photonic bandpass filter based on double cross gain modulation technique.

A tunable, coherence-free, high-resolution microwave photonic bandpass filter, which is compatible to be inserted in a conventional fiber optic link, is presented. It is based on using two cross gain modulation based wavelength converters in a recursive loop. The double cross gain modulation technique solves the semiconductor optical amplifier facet reflection problem in the conventional recursive structure; hence the new microwave photonic signal processor has no coherent interference and no phase-induced intensity noise.

Robust and environmental insensitive fiber optic Sagnac interferometer for microwave photonic applications.

A technique that allows a fiber optic Sagnac interferometer based microwave photonic device to be implemented using non-polarization maintaining components inside the Sagnac loop while still obtaining an output that is insensitive to changes in environmental conditions is presented. It is based on inserting the non-polarization maintaining components in between a polarization beam combiner and a Faraday rotator mirror inside the loop. The technique also introduces a phase bias to the light propagating inside the loop.

Microwave photonic notch filter based on a dual-Sagnac-loop structure.

A new single-wavelength, coherence-free microwave photonic notch filter is presented. The concept is based on a dual-Sagnac-loop structure that functions with a new principle in which the two loops operate with different free spectral ranges, and which generate noncommensurate taps. It has the ability to generate a narrow notch response and can operate to high frequencies.

Suppression of phase-induced intensity noise in fibre optic delay line signal processors using an optical phase modulation technique.

A technique that can suppress the dominant phase-induced intensity noise in fibre optic delay line signal processors is presented. It is based on phase modulation of the optical carrier to distribute the phase noise at the information band into a high frequency band which can be filtered out. This technique is suitable for suppressing the phase noise in various delay line structures and for integrating in the conventional fibre optic links.