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Space-time processing of the coded ultra wideband signals

Keywords:

Yu.S. Radchenko, R.V. Titov


Development of the local networks, appearance of personal networks, increasing requirements of the date rate within them – all the facts bring out that new data transmission technologies are required. One of the technologies is application of ultra wideband (UWB) pulse signals. Such signals represent the sequence of pulses with no carrier with the length of about several hundred picoseconds and low duty factor. Propagation of UWB pulse signals has a multipath nature. So, during reception of such signals not only time, but time-space processing is required, for example with the use of an antenna array. The considered UWB pulse signals can be characterized by two time parameters – delay and period, and one spatial parameter, i.e. angle of arrival (AOA), and by three autocorrelation functions, respectively. Synthesis of the UWB pulse signal time-spatial estimation algorithm shows that the logarithm of maximum likelihood functional cannot be presented into two multipliers, where the first one depends on time only, and the second one on AOA only. So, time-space processing cannot be divided to two different procedures of only time and only space processing, and UWB pulse signals cannot be characterized by a conventional polar pattern. Instead, an autocorrelation function by AOA can be considered as an energetic polar pattern (EPP). Also the autocorrelation function by delay and period can be considered as a generalized uncertainty function (GUF). GUF and EPP of non-modulated UWB pulse signals have a lot of side lobs. But using of code modulation – amplitude or position – allows much negating these side lobes. For such modulation, zero correlation zone codes and others can be used , which have been described a lot for the last years. Analysis of resolution by time and space parameters of UWB pulse signals shows that code modulation does not decrease this resolution. Also if code modulation does not reject pulses within signal, i.e. does not decrease energy of signal, then such modulation will not decrease potential accuracy of estimation time-space parameters in the case of separate estimation as well as in the case of estimation of two or all three parameters simultaneously.
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