A 7.25-7.75GHz 5.9mW UWB Transceiver with -23.8dBm NBI Tolerance and 1.5cm Ranging Accuracy Using Uncertain IF and Pulse-Triggered Envelope/Energy Detection

Abstract

The ultra-wideband (UWB) has recently been recognized as a revived wireless technology for short-range communication and fine ranging [1]–[3]. Even though the coherent UWB receiver achieves good sensitivity and high immunity against the narrowband interference (NBI), it suffers from high power and complex design for receiver synchronization. With a simple architecture and intermittent operation, the noncoherent UWB receiver achieves high energy efficiency [3], but the performance is vulnerable to the NBI. Because of new wireless standards such as 5G NR and Wi-Fi 6, having good NBI tolerance at 5-6GHz range becomes critical for UWB transceiver systems. The NBI tolerance of only -45dBm at 6GHz is reported in a recent noncoherent transceiver [4]. In this paper, we propose a 7.25-7.75GHz UWB transceiver that achieves good NBI tolerance as well as fine ranging with following features. Firstly, the uncertain-IF architecture is employed for the UWB receiver for the first time to achieve an optimum performance between energy efficiency and NBI tolerance. Unlike the uncertain-IF wake-up receiver (WuRX) for narrowband wireless standards [5], the quality (Q) factor requirement and the design complexity for the RF filter or IF filter could be significantly relaxed. To have good image rejection, a high LO frequency of 9GHz is chosen for down conversion, so that the image frequency can be beyond 10GHz. Secondly, the transceiver employs the synchronized on-off keying (S-OOK) modulation to mitigate the baseband synchronization issue [6]. Based on the S-OOK modulation, a pulse-triggered envelope/energy detector (PT-EVED) is designed in the receiver not only to automatically define an optimum integration window for good sensitivity during the communication mode but also to provide a fine ranging resolution during the ranging mode. Thirdly, a ΔΣ time-to-digital converter (TDC) is employed to have a digital-intensive ranging demodulation with a 1b oversampled output.