Digital Wireless Repeater
Wireless repeaters are the most often used devices in modern wireless communication systems. Owing to the advantages of lower cost and less complexity than base stations, they have been widely used in shopping malls, hotels, subways, airports to eliminate the signal blind/weak areas to expand signal coverage.
Wireless repeaters receive signals with their antennas, filter out noise by the functions such as filtering and low noise amplification, and then amplify desired signals’ power before transmission. Wireless repeaters can be classified into analog, fiber optical and digital types. Among them digital repeaters are built on software defined radio (SDR) technology and use digital IF (Intermediate Frequency) units instead of analog ones, allowing relay for different wireless protocols just by adjusting software configuration of digital IF units.
A digital repeater is basically made up with RF and digital IF circuits. The RF circuit is built with a low-noise amplifier, analog up and down converters, analog filter, and power amplifiers; it is mainly responsible for low-noise amplification, analog up and down conversion, power amplification, and analog filtering. The digital IF circuit includes an ADC, DAC, digital up and down converters and digital filters to implement A/D and D/A conversions, digital up and down conversion, as well as digital signal filtering, respectively. FPGAs could be used as an integrated solution for digital IF units.