Reconfigurable microwave photonic mixer with minimized path separation and large suppression of mixing spurs

Abstract

A compact reconfigurable photonic microwave mixer is proposed and demonstrated based on a dual-polarization Mach-Zehnder modulator and an optical 90-deg hybrid. By simply changing the photodetection schemes, single-ended, double-balanced, I/Q, and image-reject mixing can be implemented. Thanks to the sidebands selection by an optical filter, unwanted mixing spurs are highly suppressed. In addition, the system is insensitive to environmental vibration because the optical path separation is minimized. An experiment is carried out. Reconfigurable mixing functionalities with very small phase dithering are verified. The mixing spurs are suppressed by more than 30 dB, and the image-reject ratio for image-reject mixing is about 40 dB.

Photonics-Based Microwave Image-Reject Mixer

“…Phase-cancellation technique is another way to realize photonics-based microwave IRMs [18][19][20][21][22][23][24][25][26][27][28][29][30], also known as Hartley architecture. Figure 5 shows the principle method.…”

“…The third class of photonic IRMs based on phase cancellation applies a 90 • optical hybrid to introduce a quadrature phase [25][26][27][28][29]. Benefiting from a simple structure and the small phase imbalance of the commercially available optical hybrid over a wide frequency range, a high image rejection ratio can be achieved in a large bandwidth.…”

“…One branch is modulated by an RF signal and the other is modulated by an LO signal, both with carrier-suppressed single-sideband (CS-SSB) modulation. The CS-SSB modulation can be realized by using either optical filters placed in each branch [25][26][27], or I/Q modulators operated at CS-SSB mode [28,29]. Signals from the two branches are sent to the signal port and the LO port of the 90 • optical hybrid, which typically has two in-phase output and two quadrature output ports.…”

“…It should be noted that if other outputs of the 90 • optical hybrid are directed to PDs, single-ended and balanced mixers can also be realized. Since parallel modulations, and/or parallel filterings, and parallel amplifications are required to obtain the independent RF and LO sidebands, the system performance will therefore be vulnerable to any path length difference between the two branches [26][27][28][29]. Therefore, environmental vibration, which cause path length variations, would be a challenge for practical application of such IRMs.…”

“…In this paper, we review recent developments in photonics-based microwave IRM with an emphasis on the pre-filtering method [12][13][14][15][16][17] and the phase cancellation method [18][19][20][21][22][23][24][25][26][27][28][29][30]. Applications of photonics-based microwave IRMs in electronic warfare, radars, satellite communications, and so on, are described [31][32][33][34][35][36][37][38][39][40][41][42][43], with challenges in implementing photonics-based microwave IRMs to meet the requirements of RF systems.…”