A new microwave photonic frequency up converter is presented. It is capable to generate an up converted upper or lower sideband RF signal with the other sideband and the LO being suppressed. Compared to the reported photonics-based single sideband (SSB) frequency up converters, the proposed structure is simple and does not require high-frequency electrical components. The upper or lower sideband can be selected by controlling a modulator bias voltage. The new photonics-based SSB mixer is experimentally verified. Around 30 dB suppression in the undesired frequency components adjacent to the up converted RF signal is demonstrated for different input LO and IF signal frequencies when the SSB mixer is operated in either upper or lower sideband mode.

The objective of this paper is to present a microwave photonic system that can measure the angle of arrival (AOA) of multiple microwave signals with improved measurement accuracy. It is based on a photonic mixer approach to down convert the incoming microwave signals into IF signals, which enables a low-frequency electrical spectrum analyser to be used for measuring the power of the IF signals to determine the incoming microwave signal AOAs. AOA measurement errors can be reduced by operating the optical modulator at a different transmission point for a different range of microwave signal AOA. The system also has the ability to remove the incoming microwave signal amplitude dependence in the AOA measurement. Measured results demonstrate 0°−81.5°AOA measurement with less than ±2°errors over the 0°−30°and 30°−81.5°AOA measurement range when the optical modulator is biased at the minimum and maximum transmission point respectively. The errors remain below ±2°even when there is a ±0.1 dB change in the output IF signal power. AOA measurement of two microwave signals is also demonstrated.

An optical single sideband modulator without generating both the −2ndand +2nd-order sidebands is presented. It is based on a parallel operation of two dual-drive Mach-Zehnder modulators (DDMZMs) where one is operated as a conventional single sideband (SSB) modulator and the other is operated as a single-drive Mach-Zehnder modulator (MZM) biased at the maximum transmission point. The 2nd-order sidebands generated by the SSB modulator and the maximum-biased MZM can be cancelled by controlling the sideband amplitude and phase. Canceling the 2nd-order sidebands eliminates the secondorder harmonic component presented at the output of a long-reach fiber optic link. The new SSB modulator can be implemented using standard off-the-shelf components and has a wide bandwidth. Experimental results show >20 dB 2nd-order sidebands suppression for different modulation indexes and 22.6 dB reduction in the fiber optic link output secondorder harmonic component, compared to using a conventional SSB modulator formed by a DDMZM and a 90°hybrid coupler. Results also demonstrate that the performance of the new SSB modulator is insensitive to the optical carrier frequency and the input RF signal frequency.

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. Beating of the echo and reference signal sidebands at the photodetector generates a low-frequency electrical signal. The DFS and the AOA can be determined from the frequency and the power of the low-frequency electrical signal measured on an electrical spectrum analyzer. The system has a very simple structure and is low-cost. It has a wide operating frequency range and a robust performance. Experimental results demonstrate a DFS measurement at around 15 GHz with errors of less than ±0.2 Hz, and a 0° to 90° AOA measurement with less than ±1° errors.

A novel approach for realizing a microwave photonic image rejection mixer is presented in this paper. It is based on using a widely tunable narrow-band optical notch filter implemented by stimulated Brillouin scattering (SBS) to remove the image signal. The image rejection mixer has a simple structure as it only requires a single integrated dual-polarization modulator for both frequency conversion and pump wave generation for the SBS process. The absence of electrical components enables the image rejection mixer to be operated over a wide frequency range with a high image rejection ratio. A technique is also proposed to suppress the noise generated by the SBS process in the image rejection mixer. Experimental results demonstrate a high and constant image rejection ratio of over 32 dB for the image rejection mixer operating over an RF signal frequency range of 11.8-19.6 GHz, and around −5 dB conversion efficiency.