Applications of ultrawideband in communications and ranging

by Thanawat Thiasiriphet

Institution: Universit├Ąt Ulm
Department: Ingenieurwissenschaften und Informatik
Degree: PhD
Year: 2015
Record ID: 1117272
Full text PDF: http://vts.uni-ulm.de/docs/2015/9514/vts_9514_14372.pdf


Impulse Radio Ultrawideband (UWB) systems are based on the transmission of short time sub-nanosecond impulses. High data transfer rates as well as precise accuracy for distance and position estimation (ranging) are potentially achievable with these types of signals, while promising devices with low complexity and low power consumption. Despite of many advantages, several problems are needed to be addressed. The transmit power of the UWB systems are generally limited by spectral masks, and therefore the UWB received power is expected to be low. Analog to digital conversion cannot be performed with reasonable power consumption due to the large. For communications, optimal performance can be achieved by detection methods based on analog correlation but applying these methods to UWB systems is very challenging. Strict time synchronization and channel estimation are required. Detection method with less synchronization constraint such as energy detection is more preferable for UWB systems. We propose a novel UWB receiver structures based on a comb filter. The comb filter is a feedback loop with an analog delay element, and it is used for performing a coherent combination to improve the signal-to-noise ratio of the receiving signal and also to suppress interference from other systems. The comb based receiver can be used for both communications and ranging applications because, with proper setting, the output signal of the comb filter is the effective channel impulse response. The coherent combination process in the comb filter gives energy detection the benefits that cannot be achieved by conventional approaches. For ranging, conventional methods based on analog impulse correlation perform very well in high SNR scenarios but large error bias is expected when the SNR is low. The SNR improvement from the comb filter can improve the ranging performance of UWB radar system greatly.