Measurement of Broadband IF-over-Fiber Link for 60 GHz Wireless Applications

Abstract

Indoor wireless systems at 60 GHz provide much higher throughput than today’s solutions but need more closely spaced access points. Radio-over-Fiber advancements are a promising solution for the signal distribution. We propose a broadband IF-over-Fiber architecture comprised of miniaturized electronic components for quadrature modulation and upconversion. The 60 GHz wireless generation is realized by transmitting at intermediate frequency (IF) at 10 GHz over single mode fiber (SMF) and upconversion at the base station (BS) front-end with low-cost electronic components on printed circuit board (PCB). The central station (CS) includes an electronic IQ modulator for the provision of multi-Gbps quadrature data modulation formats and successively increase the spectral efficiency of the wirelessly transmitted data. The BS front-end comprises of the 60 GHz upconverter and a 60 GHz planar 2\(\times \)2 microstrip antenna array. The 10 GHz IF carrier allows an optical transmission with higher spectral efficiency in optical domain, as well as it is less susceptible to dispersion induced power fading inherent in optical fiber. The optical fronthaul link of the 10 GHz IF signal modulated with up to 2 Gbps payload data over SMF lengths of 2 km, 12.8 km and 25.6 km has been studied. The system analysis is made with respect to error vector magnitude (EVM), eye and constellation diagrams. The recovered QPSK data has signal-to-noise of 14 dB corresponding to EVM of 20% for transmission over 25.6 km SMF.