This paper presents a transceiver prototype capable of in-band full duplex communication. Apart from a conventional transceiver and antenna, this prototype relies on a tunable elec trical balance duplexer to minimize the in-band self-interference at RF. Such duplexer however requires continuous-time tuning to ensure accurate impedance balancing with the antenna across dif ferent environmental conditions. An automatic tuning algorithm is presented which tracks antenna impedance variations and tunes the duplexer accordingly. This tuning operates on a standard compliant training sequence to minimize the overhead on the communication system. The implemented tuning mechanism does not require any additional RF or analog hardware, and maximally re-uses the digital resources of a conventional baseband processor.The full duplex prototype was validated in a wireless link for IEEES02.11 channels in the 2.4GHz ISM band, in which the error vector magnitude improves by 15dB as the RF self-interference cancellation increased from 25dB to 45dB.Keywords-In-band full duplex, self-interference cancellation, automated tuning, transceiver prototype.978-1-63190-055-6

Cross-correlation can be used in energy detection applications, such as spectrum analyzers, but also frequency shift keying (FSK) receivers, to improve noise suppression. To achieve higher signal-to-noise ratio (SNR), integration in time may be used, but could make it rather slow for communication purposes. In order to achieve better data-rates in low SNR conditions, we propose to use multiple chains instead of the traditional two chains. In this paper, we show an analysis of the SNR improvement and the power consumption penalty for BFSK modulation when using more chains. It shows that for low noise correlation between the chains, the improvement in sensitivity is proportional to the number of chains. Also, we develop a figureof-merit to evaluate the optimum number of chains for different parameters of the receiver design. Furthermore, two examples from literature are analyzed. At their optimum number of chains, they both show ∼6dB improvement in sensitivity with similar or even better figure-of-merit.

Wireless sensor networks have recently emerged in a wide range of applications. Many attributes are essential for such networks such as: low cost, small form-factor, limited peak power consumption and the ability to operate in harsh interference scenarios. Most of these networks do not require high data-rates to operate. In this respect, sub-sampling receivers have shown promising results but suffer from noise folding and interference aliasing. In this paper, a sub-sampling receiver in combination with cross-correlation is used to enhance sensitivity and interference robustness while maintaining the sub-sampling advantages. An architecture which uses two different sampling frequencies is proposed. It shows ∼2dB SNR improvement compared to traditional architectures due to cross-correlation and an additional ∼2dB for each doubling of integrations. For a BER of 10 −3 , the required SIR is reduced with 4.5dB, 11.5dB and 14.5dB after using cross-correlation with the same, half and quarter data-rate used respectively. These improvements allow for a lower-power and lower-cost implementation.

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 2and 3-receiver cross-correlation in a BFSK receiver. Operating at 1 GHz and with a data rate of 200 kbps, the demonstrator, using sub-mW mixer-first receiver front-ends for power efficiency, achieves −102 dBm sensitivity and > 40 dB rejection for both narrow and wideband harmonic interferers without any RF filters.