Photonics‐Based Microwave Frequency Mixing: Methodology and Applications

Abstract

Photonics‐based microwave frequency mixing provides distinct features in terms of wide frequency coverage, broad instantaneous bandwidth, small frequency‐dependent loss, and immunity to electromagnetic interference as compared with its electronic counterpart, which can be a key technical enabler for future broadband and multifunctional RF systems. Herein, all‐optical and optoelectronic microwave frequency mixing techniques are reviewed, with an emphasis on the latest advances in photonics‐based microwave frequency mixers with improved performance in terms of conversion efficiency, dynamic range, mixing‐spur suppression, mixing functionality, and polarization independence. Innovative applications enabled by photonics‐based microwave frequency mixers, such as radio‐over‐fiber communication systems, radar systems, satellite payloads and electronic warfare systems, are also reviewed. In addition, efforts in implementing integrated photonics‐based microwave mixers that lead to a dramatic reduction in size, weight, and power consumption are also reviewed.

Chip‐Based Microwave‐Photonic Radar for High‐Resolution Imaging

“…Electronic approaches apply filters to remove some of the mixing spurs and out of band noise, which, however, restricts the instantaneous bandwidth of the system. Photonic I/Q mixing or image-reject mixing can apply wideband coherent cancellation to overcome this problem using optical 90°hybrid or microwave photonic phase shifters, [30,31] which not only ensures a wideband de-chirping, but also eliminates the frequency mixing between radar echoes of different targets. [13] Wavelength-division multiplexing may also be adopted for the chip-based system, which opens the possibility for on-chip arrayed radar or MIMO radar with reduced hardware resources.…”

Microwave Photonic Radars

“…Other broadband analog signal processing based on CW lasers was also reported, such as phase shifting [124]- [126], mixing [10], [127], phase coding [128], [129], filtering [130]- [132], Fourier transform [133], [134], and frequency multiplication [135]- [137], which exhibits excellent flexibility and reconfigurability as well. The combination of OFCs and CW-based signal processing would further enhance the signal processing with parallel processing capability, which not only reduces the number of devices but also improves the inter-channel consistency.…”

“…The excellent amplitude-phase consistency would enable wideband noise and interference cancellation in the optical domain. Previously, coherent cancellation is explicitly or implicitly used in many microwave photonic systems, such as highlinearity analog optical links [141]- [145], image-reject mixers [10], [146]- [152], co-site interference cancellation [153]- [159], and frequency multipliers [160]- [162] to suppress the noise, undesirable nonlinear components, interference and image frequencies. For example, a linearized analog optical link with the third-order intermodulation distortion (IMD3) component suppressed by 40 dB was built in [142]; an image-reject mixer with an image-rejection ratio of 25 dB for a 1.2-GHz instantaneous bandwidth linearly frequency-modulated (LFM) signal was realized in [150] (as a comparison, the instantaneous bandwidth of an electrical image-reject mixer is less than 160 MHz [146]); a 30-dB co-site interference cancellation ratio over 9.5 GHz frequency range was obtained in [156] (while for electrical method the maximum reported bandwidth is only 120 MHz [163]); and an optical link with the common-mode noise suppressed by 15 dB over an 18-GHz frequency range was implemented in [164].…”

“…In the transmitter, mixers are needed to upconvert the wave-form generated at the IF band to the desired RF band; while at the receiver, the mixers are required to down-convert the received RF signal to the baseband or IF band since the ADCs and DSP units usually have insufficient bandwidth to directly process the RF signals. To meet the requirement of future multifunctional or reconfigurable radars, mixers should be capable of processing Although a lot of wideband mixers have been developed using pure electronics, they always generate a large number of undesired mixing components (15-dB LO and RF to IF isolation for a 4-44 GHz commercially available electrical mixer [10]). Filters can remove some of the mixing spurs, but they may not work if the input signal has a wide bandwidth.…”

“…In that case, the mixing spurs and the desired output might overlap in the spectrum. As a result, the operational instantaneous bandwidth and the dynamic range of the mixer are still limited (i.e., IF instantaneous bandwidth limited to no more than 3 GHz [10]), leading to multi-stage frequency converters together with filters employing to today's radar systems to ensure a sufficiently high dynamic range, favorable conversion efficiency, and acceptable mixing-spur suppression [245]- [247].…”