Broadband Microwave Photonic Mixer With High Spurs Suppression and Image Rejection

Abstract

Abstract-A microwave photonic mixer for up-and downconversion based on dual parallel in-phase and quadrature (I/Q) modulators is proposed. Dual parallel I/Q modulators and 90degree electrical hybrid couplers are used to obtain carriersuppressed single-sideband modulation of radio frequency (RF), intermediate frequency (IF), and local oscillator (LO) signals.The optical bandpass filter (OBPF) is employed to select the -1storder or +1st-order sideband of the LO signal to realize up and down conversion. In the experiments, an IF frequency range of 5-17 GHz can be upconverted to an RF frequency range of 15-37 GHz, and an RF frequency range of 8-40 GHz can be downconverted to an IF frequency range of 2-5 GHz. The spurs suppression ratio exceeds 50 dB for up and down conversion. To the best of our knowledge, this is the highest reported spurs suppression in a broadband microwave photonic mixer. Moreover, the OBPF is also utilized to obtain an image rejection ratio (IRR) of 45.91 dB at an IF frequency of 4 GHz. To obtain a lower frequency of IF signal and a higher IRR, a Brillouinassisted notch filter is applied to attenuate the image signal. In this way, an IRR of more than 60 dB can be obtained at an IF frequency of 2 GHz.

A Reconfigurable Local Oscillator Harmonic Mixer with Simultaneous Phase Shifting and Image Rejection

“…It can be observed that the IF signal generated by the image signal frequency conversion is well suppressed with an IRR of 51.35 dB as presented in Figure 11a. In the same situation without using a 90 • optical hybrid coupler, the IRR is also better than the 45.91 dB in [10]. Additionally, in Figure 11b, the amplitude of the IF signal waveform generated by the frequency conversion of the image signal is almost zero.…”

“…For example, Zhu et al proposed a frequency down-conversion scheme based on CS-SSB modulation via an integrated DP-MZM [19]. Shen and Zhou proposed a dual parallel in-an I/Q modulators-based microwave photonic mixer [10]. Considering frequency conversion efficiency, the above-mentioned solutions have their limitations since they can only achieve down-conversion of a single frequency and are only suitable for point-to-point scenarios.…”

“…Meanwhile, the frequency conversion system implemented image rejection capabilities to eliminate the impact of IM on the mixing process, thereby enhancing the system's anti-interference ability to respond to varying interference sources in the space spectrum. Finally, compared to non-reconfigurable solutions [9][10][11][12], the scheme proposed in this paper is more flexible. It can be switched to select the up-conversion or downconversion and enables the flexible selection of ±first, ±second, ±third, ±fourth-order sidebands of the LO for mixing according to specific requirements, thereby achieving signal output in different frequency bands.…”

“…Therefore, phase shifting with 360 • fullrange tuning capability is one of the core functions in various signal processing applications, such as IoT [6], multifunctional radars [7], and satellite payloads [8]. However, some of the current mixing schemes can only convert frequency without phase shifting [4,9,10]. Therefore, microwave photonic mixers that possess phase shifting functionalities have become a research hotspot.…”