Zhaoyang Tu

Simultaneously photonic frequency downconversion, multichannel phase shifting, and IQ demodulation for wideband microwave signals

A single photonic system that can simultaneously perform frequency downconversion, multichannel phase shifting, and in-phase (I) and quadrature (Q) demodulation for microwave signals is proposed and experimentally demonstrated. Using an integrated polarization-division multiplexing Mach-Zehnder modulator, radio frequency (RF) signals can be frequency downconverted to multichannel intermediate frequency (IF) signals and the phase of each IF signal can be independently and arbitrarily tuned. Using two quadrature channels, the RF signal can be IQ demodulated. In the experiment, high and flat conversion gains from 8 to 40 GHz and continuously tunable phase shifts over the 360-deg range are demonstrated. In addition, vector signals with various modulation formats at 40 GHz are frequency downconverted to baseband and the IQ data are successfully extracted.

Photonic microwave frequency measurement with a tunable range based on a dual-polarization modulator

This paper presents a novel photonic-assisted microwave frequency measurement scheme based on an integrated dual-polarization Mach-Zehnder modulator (DPol-MZM). The DPol-MZM is used to obtain a polarization multiplexing signal modulated by the microwave signal with the frequency to be identified. The obtained signal is split into two channels after propagating along a single mode fiber. The two divided parts are used to establish an amplitude comparison function (ACF) which provides frequency-power mapping. The proposed scheme is experimentally verified. The frequency responses of the two branches are nearly complementary; thus, a relatively steep ACF is obtained. A frequency measurement range from 2 to 28 GHz with an error of ±0.2  GHz is achieved. Moreover, the measurement range can be tuned by simply adjusting the polarization state of one channel. The proposed system is simple, and the measurement range can be easily adjusted.

Analog Photonic Link With Tunable Optical Carrier to Sideband Ratio and Balanced Detection

Optical carrier to sideband ratio (CSR) optimization and balanced detection are two effective techniques to improve the performance of an analogy photonic link (APL). Here, we proposed an APL where tunable optical CSR and balanced detection can both be implemented. A single integrated polarization division multiplexing Mach–Zehnder modulator (PDM-MZM) is used to generate a polarization multiplexed signal containing an optical carrier and two radio frequency modulated sidebands, and the optical CSR can be tuned from –15 to 15 dB by simply adjusting the direct current bias of the modulator. By optimizing the optical CSR in the proposed link, the link gain and noise figure (NF) are improved by 12 and 6.8 dB compared with conventional quadrature biased link. In addition, after balanced detection in the proposed link, the link gain, NF, third-order spurious free dynamic range (SFDR), and especially the second-order SFDR are further improved.

A Photonic Technique for Instantaneous Microwave Frequency Measurement Utilizing a Phase Modulator

We propose a simple microwave frequency measurement approach utilizing a phase modulator. After properly adjusting the polarization controllers in the proposed system, two dispersion-induced power penalty functions with different variation trends are obtained. A distinct relationship between the power ratio and the microwave frequency can be constructed by comparing the two power penalty functions. Thus, the microwave frequency can be determined by the power ratio value. Since only a bias drift free phase modulator and a single laser source are needed, the measurement system is significantly simplified. In the experiment, a frequency measurement over the range of 1.6-24.6 GHz with measurement errors within ±0.3 GHz is achieved.

Angle-of-Arrival Estimation of Broadband Microwave Signals Based on Microwave Photonic Filtering

We propose and experimentally demonstrate a photonic approach to estimate the angle-of-arrival (AOA) of broadband microwave signals. Using an integrated polarization-division multiplexing Mach–Zehnder modulator and a differential group-delay module, a microwave photonic notch filter is constructed. The relative time delay in reception of the signal at two separate antenna elements can be obtained by measuring the transmission notches over the signal spectra. The AOA is calculated from the relative time delay and the antenna spacing. The experiment results show that the measurement error is less than ±0.35 ps when the relative time delay changes from −14 to 16 ps.