The Study Of Ranging Method Based On The UWB Techniques

Recent years, Ultra wideband techniques have been the focus of much research and development because of its unique characteristics, especially following the approval of the UWB techniques by the FCC (Federal Communications Commission) in February 2002. And it also results in an increasing research in UWB applications. UWB impulse radio technique makes use of ultra-short duration pulses, which yields ultra-wideband signals characterized by extremely wide frequency band and extremely low power spectral densities. Its application in military field and civilian field is becoming wider and wider in virtue of the good abilities of anti-detection, low power consumption, potentially immunity to multipath fading and so on.With the development of wireless communication techniques and the increasing requirement of various kinds of services for users, ranging and location are playing a more and more important role. Several conventional location techniques, such as GPS location, location based on the cell Network (Cell ID Positioning), have a limited application foreground because of their various disadvantages. Communication network based on UWB transmission has good abilities of anti-noise, anti-jam, resolving multipath and penetrating walls, and has a larger communication capability as well. Therefore, UWB technique is becoming a potential technique for the future ranging and location techniques.It is well known that multipath and non-line-of-sight (NLOS) are the main factors that affect the ranging accuracy of time-of-arrival (TOA) estimation based on UWB. So, the UWB ranging technique faces a challenge in the multipath and NLOS environments. Typical approaches for UWB TOA estimation in many papers are based on the signal cross-correlation. But the first arrival path is not always the strongest component owing to the multipath and NLOS. Therefore the detection of the first arrival path is very important.Though the ranging method by using the signal cross-correlation can get much high accuracy, it needs very high sampling rates. But the UWB receivers usually have to operate at very low sampling rates compared to Nyquist rate. This makes it difficult to effectively capture the energy at each individual multipath component using the local correlator. So, energy detection (ED) based ranging becomes a feasible alternative because of its simplicity and lower sampling rates.In this thesis, after introducing the basic principles of UWB systems, we mainly studied two tasks just described as follows: 1) A new two-step ranging algorithm is proposed. In order to reduce the ranging error caused by the NLOS, in our proposed method, the first step is to obtain the rough TOA and the second is to improve the ranging accuracy by using the early-late gate signals. Theoretics and simulation results show that it can improve the ranging accuracy without needing the additional algorithm complexity.2) An adaptive noise cancellation (ANC) based ranging algorithm is proposed. we firstly conclude the main ranging algorithms based on the energy detection. Though energy detection does not require accurate timing or pulse shapes, it suffers from noise due to a square-law device. So in this thesis, we use an ANC system to decrease the effect of the noise. The results show that the ranging method based on the ANC system can accomplish ranging even under the condition of small SNRs, and has a higher ranging precision.