Uwb Radar
Uwb Radar And Applications CHAPTER 1
INTRODUCTION
UWB stands for ultra wideband. The basic concept is that frequency is meaningless. UWB systems use electromagnetic pulses, just pulses, not short wave-packets. Pulse repetition frequency (PRF) couldnot be declared, as is not a correct figure of electromagnetic spectrum occupation. PRF is typically in the range of 1 to 50 MHz.The pulse repetition period ismodulated to carry information or coding. A precise frequency description of UWB emission could be given by the Fourier transform of the pulse. Being the pulse very narrow, in the order of hundreds of picoseconds, frequency spectrum widens up to a few gigahertz often without a clear peak.
Figure 1.1 Waveform of 320ps 1W UWB radar pulse
As a consequence resonance and UWB technology are opposite concepts. Resonance means narrow band, while ultra wideband means a wider band, or even the widest. Unlike conventional radio systems, resonating circuits are not used in UWB radio. Actually they are, or should be, avoided, even if it is not quite easy to do so.
A.S.I.E.T, Kalady Department Of Electronics And Communication
1
Uwb Radar And Applications
Figure 1.2 A sinusoidally shaped UWB pulse in frequency domain
Since the pulse is extremely concentrated in time, it is clear that power is spread in the frequency domain. Actual spectrum usage can only be estimated from the FFT of the emitted pulse train or it can be measured with a sensible spectrum analyzer. The frequency tuning concept is now useless because the focus is on time. Ultra wideband systems are definitely ―tuned in time‖ not infrequency. So high Q-factor components for signals selection in frequency are not needed and precise timing is used instead. The analysis of fields of application for UWB technologies demonstrates that device of this type can be used practically in all cases where highly precise remote observation of objects at short distances and their motion are required.
A.S.I.E.T, Kalady
INTRODUCTION
UWB stands for ultra wideband. The basic concept is that frequency is meaningless. UWB systems use electromagnetic pulses, just pulses, not short wave-packets. Pulse repetition frequency (PRF) couldnot be declared, as is not a correct figure of electromagnetic spectrum occupation. PRF is typically in the range of 1 to 50 MHz.The pulse repetition period ismodulated to carry information or coding. A precise frequency description of UWB emission could be given by the Fourier transform of the pulse. Being the pulse very narrow, in the order of hundreds of picoseconds, frequency spectrum widens up to a few gigahertz often without a clear peak.
Figure 1.1 Waveform of 320ps 1W UWB radar pulse
As a consequence resonance and UWB technology are opposite concepts. Resonance means narrow band, while ultra wideband means a wider band, or even the widest. Unlike conventional radio systems, resonating circuits are not used in UWB radio. Actually they are, or should be, avoided, even if it is not quite easy to do so.
A.S.I.E.T, Kalady Department Of Electronics And Communication
1
Uwb Radar And Applications
Figure 1.2 A sinusoidally shaped UWB pulse in frequency domain
Since the pulse is extremely concentrated in time, it is clear that power is spread in the frequency domain. Actual spectrum usage can only be estimated from the FFT of the emitted pulse train or it can be measured with a sensible spectrum analyzer. The frequency tuning concept is now useless because the focus is on time. Ultra wideband systems are definitely ―tuned in time‖ not infrequency. So high Q-factor components for signals selection in frequency are not needed and precise timing is used instead. The analysis of fields of application for UWB technologies demonstrates that device of this type can be used practically in all cases where highly precise remote observation of objects at short distances and their motion are required.
A.S.I.E.T, Kalady
References: [1] M. Kulkarni, ―Microwave and Radar Engineering‖ pp. 514-517 umesh publications January 2010 [2] Harmuth H.F. (1984) Antennas and waveguides for nonsinusoidal waves. Supplement 15 Advances in Electronics and Electron Physics, Academic Press, Inc. [3] Harmuth H.F. (1986) Propagation of nonsinusoidal electromagnetic waves. Supplement18 Advances in Electronics and Electron Physics, Academic Press, Inc. [4] Harmuth H.F. (1990) Radiation of nonsinusoidal electromagnetic waves. Supplement 23 Advances in Electronics and Electron Physics, Academic Press, Inc. [5] Fullerton L.W. (1987) Spread spectrum radio transmission system. United States Patent 4,641,317. [6] Fullerton L.W. (1988) Time domain radio transmission system. United States Patent 4,743,906. [7] Fullerton L.W. (1989) Time domain radio transmission system. United States Patent 4,813,057. [8] Fullerton L.W. (1990) Time domain radio transmission system. United States Patent 4,979,186. [9] [10] McEwan T.E. (1994) Ultra-wideband receiver.United States Patent 5,345,471. McEwan T.E. (1994) Ultra-wideband radar motion sensor. United States Patent 5,361,070. [11] Harmuth H.F. (1981) Nonsinusoidal waves for Radar and radio communication.Supplement 14 Advances in Electronics and Electron Physics, Academic Press, Inc. A.S.I.E.T, Kalady Department Of Electronics And Communication 23