UWB(ultra wide band) technology is a new type of wireless communication technology. It has a very steep by rising and falling time direct modulation of impulse pulse signal GHz, with the scale of bandwidth. Ultra-wideband technology which has solved the traditional wireless technology years of relevant major problem of the spread of channel decline, it has not sensitive, transmitting power spectral density low, low intercept capability, system and complexity, provide a few centimeters low the positioning precision, etc.
1 ultra-wideband signal and its features beauty the federal communications commission (FCC) regulation, part of the bandwidth for UWB signal boasts. Among them, some bandwidth for signal power spectral density 10dB place in - the value of measurement. Figure 1 for UWB signal and narrow width signal power spectral density comparison; A kind of typical pulse position modulation (PPM) UWB signal form way of [1], [2] for:
Str (k) (t) said the launch of the first k a user signal, it has not also is the number of single periodic impulsive move sum. W (t) said the single cycle pulse waveform transmission for single cycle, or gaussian pulse first and second order differential pulse one from the transmitter clock zero moment (t (k) = 0) started. The first j a pulse starting time for. Careful analysis of each time move weight:
(1) the pulse sequence diam-eter move the pulse said: form Time step of Tf, its single periodic impulsive 390v is extremely low, frames long or pulse repetition Time Frame a) (Tf typical values of pulse width for single cycle a hundred to a thousand times. ALOHA systems, so similar to the pulse sequence extremely easy cause random collisions.
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