Channelized multi-frequency measurement system based on asymmetric double sideband detection.

A channelized multi-frequency measurement system based on asymmetric double sideband detection is proposed. In this scheme, the sub-modulators of the dual-parallel Mach-Zehnder modulator are utilized for optical frequency comb (OFC) generation and under-test signal modulation. Subsequently, a sawtooth wave voltage is applied to the main modulator to introduce frequency shift to the modulated signals, breaking the symmetry between the RF signals and the OFC. The coupled signal is then divided into upper and lower sidebands for frequency down-conversion. By calibrating the measurement results of the two sidebands with each other, the frequency of the signal can be accurately measured. Simulation is preformed to realize multi-frequency measurement of microwave signals with measurement error less than 2 MHz in the range of 2.2-20 GHz. It is also found that the proposal can solve the problem of frequency ambiguity.

Photonic generation of triangular waveform with tunable symmetry based on channelized frequency synthesis.

A symmetry tunable triangular waveform photonic generator based on channelized frequency synthesis is proposed and studied. The generator adopts a multichannel system architecture and harmonic amplitude control algorithm to physically isolate each subchannel. In a single subchannel, quadrature phase shift keying modulation and coherent dual-wavelength balanced detection are used to realize optical upconversion and suppress mixing interference in the process of frequency conversion. Therefore, the model has the characteristics of a high-order Fourier series fitting tunable function waveform output. The analysis results show that the Fourier series harmonic coefficients can be adjusted flexibly by the multivariable joint regulation algorithm. The relationship between the variables is analyzed and discussed. The feasibility of the scheme is verified by optical simulation; when the rms error (RMSE)≤0.03, a 20%-80% tunable symmetry triangular waveform can be obtained.

Multiple microwave frequency measurement system based on a sawtooth-wave-modulated non-flat optical frequency comb.

A photonic-assisted instantaneous microwave measurement system, capable of measuring multiple frequency signals, is demonstrated and analyzed. The principle lies in the combination of a channelizer and frequency-to-power mapping. An effective generation method of a non-flat optical frequency comb is proposed based on sawtooth wave modulation, which has more comb lines and adjustable comb spacing. Under this method, two low-speed post-processing devices are utilized to realize frequency measurements up to 32 GHz. The scheme is verified by simulation, and factors affecting system performance are also studied.