Wideband microwave phase noise measurement based on photonic-assisted I/Q mixing and digital phase demodulation

Abstract

A wideband microwave phase noise measurement system is proposed based on quadrature phase demodulation of the mixing components of a signal under test (SUT) and its delayed replica. The time delay is introduced by a low-loss optical fiber, which can be sufficiently large to achieve a high phase noise measurement sensitivity, and the quadrature phase demodulation is achieved by photonic-assisted in-phase and quadrate (I/Q) mixing together with digital signal processing. Thanks to the optoelectronic hybrid quadrature phase demodulation, the use of feedback loops, which are usually required in conventional photonic-delay-line-based phase noise measurement systems, is avoided, and the measurable frequency range is expanded. An experiment is implemented. Accurate phase noise measurement of SUTs in a frequency range of 5-35 GHz is demonstrated. With a 2-km single-mode fiber serving as the photonic delay line, the phase noise floor is as low as -131 dBc/Hz at the offset frequency of 10 kHz. The proposed scheme can be applied for evaluating the performance of microwave systems using low-phase-noise and wideband tunable microwave sources.

Wideband Microwave Phase Noise Analyzer Based on All-Optical Microwave Signal Processing

“…For instance, optical frequency comb and carrier suppression interferometer techniques have been introduced to enhance the measurement sensitivity [12][13][14]. To eliminate the calibration procedure, quadrature phase demodulation based on in-phase and quadrate (I/Q) mixing and digital signal processing is adopted [13,[15][16][17]. Recently, multiple functions, such as microwave signal generation and frequency measurement, have also been integrated into the original phase noise measurement system [18][19][20].…”

Self-calibrating and high-sensitivity microwave phase noise analyzer applying an optical frequency comb generator and an optical-hybrid-based I/Q detector

“…In radar, communication, and navigation systems, high-stability microwave signals are highly demanded [2,3], and a high-sensitivity phase noise analyzer (PNA) is indispensable for measuring microwave signals having a low phase noise. Among the various methods for establishing a PNA, the photonic-delay-line-based frequency discriminator method has attracted a lot of attention because it can achieve a high sensitivity and a large measurement frequency range with the help of microwave photonic technologies [4][5][6][7]. In this method, to achieve a high phase noise measurement sensitivity, a large time delay is required [8], which, however, will reduce the reliable offset frequency range for phase noise measurement.…”

“…First, thanks to the use of balanced photodetection, the obtained signals in Eqs. (4) and (5) are free from the direct component (dc) interference, which is undesirable in zero-intermediate-frequency signal processing [7]. Besides, in obtaining Eq.…”

“…[10], the proposed PNA is free from complex calibration and interferences from the amplitude noises of the SUT and the laser. Compared with our previous work using an I ∕Q mixer for phase noise measurement [7], the proposed PNA is free from additional procedures to deal with the dc component that is undesirable in zero-intermediate-frequency signal processing. In addition, the proposed PNA can achieve a much lower phase noise floor through measuring the multiple phase noise.…”