Low-Cost MIMO Radio Over Fiber System for Multiservice DAS Using Double Sideband Frequency Translation

In this paper, a novel low-cost DSB frequency translation system is experimentally demonstrated and its theory is mathematically proved. The new system is capable of transmitting wideband LTE MIMO signals and supporting multiple services. Experimentally, 2 × 2 LTE MIMO channels with 20 MHz bandwidth, and a 700 MHz carrier frequency, are transmitted simultaneously along with an IEEE 802.11 g signal (54 Mbps) over a 300 m length of multi-mode fiber (MMF). The MIMO channel matrix of the system is retrieved and the condition number is calculated. It can be seen in the experimental results that the system is well conditioned, has a low-error vector magnitude (EVM) and the transmission of the MIMO signals has negligible effect on the IEEE 802.11 g signal. The use of a preamplifier minimizes the nonlinearity introduced by the frequency mixers, resulting in a high spurious-free dynamic range (SFDR). Compared to a single sideband (SSB) system, where multiple filters are used and two channels encounter different EVMs, the new DSB system avoids unnecessary filtering and the impairments introduced will be the same for both channels. Therefore it can be concluded that the improved MIMO over fiber system using DSB frequency translation technology is a potential low-cost solution for multiservice MIMO-enabled distributed antenna systems (DAS).