are now being produced, in laptop and a Gaussian monopulse, shown in Figure 5.2-27. Its power notebook computers for example, that include both spectrum is shown in Figure 5.2-28. If the time scale in Wi-Fi and Bluetooth, sometimes even in the same Figure 5.2-27 is in nanoseconds, then the width of the chipset. In this case collaboration is possible in the device pulse is 0.5 nanoseconds and the 3 dB bandwidth of the software to prevent inter-network collisions. power spectrum is approximately 3.2 GHz with maxi- mum power density at 2 GHz. 5.2.5 Ultra-wideband technology In order to pass information over a UWB communi- cation link, trains of pulses must be transmitted with some characteristic of a pulse or group of pulses varied in Ultra-wideband (UWB) technology is based on trans- order to distinguish between "0" and "1." The time be- mission of very narrow electromagnetic pulses at a low tween consecutive pulses should be determined in repetition rate. The result is a radio spectrum that is a pseudo-random manner in order to smooth the energy spread over a very wide bandwidth-much wider than spikes in the frequency spectrum. Reception of the the bandwidth used in the spread-spectrum systems transmitted pulse train is done by correlating the re- previously discussed. Ultra-wideband transmissions are ceived signal with a similar sequence of pulses generated virtually undetectable by ordinary radio receivers and in the receiver. A large number of communication links therefore can exist concurrently with existing wireless can be maintained simultaneously and independently by communications without demanding additional spec- using different pseudo-random sequences for each link. trum or exclusive frequency bands. A pulse similar to that of Figure 5.2-27 can be gen- These are some of the advantages cited for erated by applying an impulse, or perhaps more conve- ultra-wideband technology: niently a step-voltage or current, to a linear band limited Very low spectral density-Very low probability of interference with oth