Photonic down‐conversion and linearisation with tunable IF bandwidth and improved spurious‐free dynamic range

Abstract

A scheme for simultaneous down-conversion and linearisation of radio-frequency (RF) signals is proposed and demonstrated. Based on carrier-suppressed double-sideband modulation, the input RF signal can be down-converted to any intermediate frequency (IF) tone in the range of 8-12 GHz. Compared with the down-conversion scheme with two cascaded intensity modulators, the proposed scheme has improvement of >21 dB of the suppression ratio of third-order intermodulation distortion and 6.17 dB of spurious-free dynamic range.

Linearized microwave downconversion link based on fast and intelligent impairment equalization for noncooperative systems

“…Nevertheless, the nonlinearity of the modulator is one of the main problems that may lead to the intermodulation distortion (IMD), in particular the thirdorder IMD (IMD3), which would degrade the spurious free dynamic range (SFDR) [5] . So far, several effective schemes have been reported to improve the linearity of downconversion links, including (i) employing cascaded modulators combined with an optical filter [6][7][8] , and (ii) using one dual-polarization quadrature phase shift keying (QPSK) Mach-Zehnder modulator (MZM) and two photodetectors (PDs) [9] . However, most microwave photonic-based systems, in particular the array radar systems and electronic reconnaissance systems, are built up based on simple intensity modulation and direct detection (IM-DD).…”