Multi-Receiver Cross-Correlation Technique for (B)FSK Radios

This article presents a multi-receiver cross-correlation technique for (B)FSK receivers, targeting wireless sensor network applications. Here, multiple receiver outputs are pair-wise cross-correlated and the correlated output samples are averaged to lower the noise floor at the receiver output. Compared to a two-receiver cross-correlation, multi-receiver cross-correlation generates more cross-correlated output samples in a given time. Hence it requires a shorter measurement time for a desired noise floor reduction and facilitates a higher data rate for (B)FSK operation. Compared to a single receiver, it improves the linearity and the harmonic interferer tolerance using passive splitters and different LO frequencies in the receiver paths respectively. These theoretical insights are verified with measurements for the first time using a 2- and 3-receiver cross-correlation in a BFSK receiver. Operating at 1GHz and with a data rate of 200kbps, the demonstrator, using sub-mW mixer-first receiver front-ends for power efficiency, achieves -102dBm sensitivity and >40 dB rejection for both narrow and wideband harmonic interferers without any RF filters.