System and method for generating shaped ultrawide bandwidth wavelets

Abstract

An ultra-wide band (UWB) waveform generator and encoder for use in a UWB digital communication system. The UWB waveform is made up of a sequence of shaped wavelets. The waveform generator produces multi-amplitude, multi-phase wavelets that are time-constrained, zero mean, and can be orthogonal in phase, yet still have a −10 dB power spectral bandwidth that is larger than the frequency of the peak of the power spectrum In one embodiment, the wavelets are bi-phase wavelets. The encoder multiplies each data bit by an n-bit identifying code, (e.g., a user code), resulting in a group of wavelets corresponding to each data bit. The identifying codeword is passed onto the UWB waveform generator for generation of a UWB waveform that can be transmitted via an antenna.

Description

CROSS REFERENCE TO RELATED PATENT DOCUMENTS [0001] The present application is a continuation application of U.S. patent application Ser. No. 09 / 685,205, filed Oct. 10, 2000, entitled SYSTEM AND METHOD FOR GENERATING ULTRA WIDEBAND PULSES.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to ultra wideband radio communication systems, and in particular to methods, systems and devices for generating waveforms that include wavelets that are shaped and modulated to convey digital data over a wireless radio communication channel using ultra wideband signaling techniques. [0004] 2. Description of the Background [0005] There are numerous radio communication techniques to transmit digital data over a wireless channel. These techniques include those used in mobile telephone systems, pagers, remote data collection systems, and wireless networks for computers, among others. Most conventional wireless communication techniques modulate the digital d...

AI Technical Summary

Benefits of technology

"The present invention provides a novel programmable wavelet generator for use in UWB communication systems. The generator uses an analog mixer and a pulse generator to create various shapes of UWB wavelets. The shape of the wavelet can carry more than one bit of information by varying the shape, position, or both, according to an encoding scheme. The invention also provides a highly integratable approach for generating wavelets and encoding data onto UWB wavelets by controlling the shape of the wavelet. The resulting waveform can be transmitted as a UWB signal. The invention has various technical effects, such as improved data transmission and increased efficiency of the UWB communication system."

Problems solved by technology

Several problems arise with this technique, however.

First, it is not as efficient as other techniques, for example, sending non-inverted and inverted pulses where 3 dB less radiated power is required to communicate in the same memory-less Gaussian white noise channel.

Second, reflections from objects in the vicinity of the transmitter and receiver can cause a pulse that was supposed to be at the beginning of the time window, to appear in at the end of time window, or even in the time window of a subsequent pulse.

One of the problems associated with this technique is that the transmission lines take up sizeable space and accordingly, are not amenable to integration on a monolithic integrated circuit.

In generating these UWB pulse streams, however, non-ideal device performance can cause tones to pass through to the antenna and to be radiated.

In particular, switches, gates, and analog mixers that are used to generate pulses are well known to be non-ideal devices.

Accordingly, leakage is a problem.

This is problematic since one of the design objectives is to generate a pulse stream that will not interfere with other communications systems.

Similar problems to those discussed above regarding transmitters are also encountered in UWB receivers.

As discussed above, the spectral spikes (DC and otherwise) introduced by the non-ideal analog mixers can make decoding of only moderately weak signals difficult or impossible.

Furthermore, UWB receivers often suffer from leakage of the UWB signal driving the mixer.

This reception of the drive signal being used to decode the received signal can therefore cause a self-jamming condition wherein the desired signal becomes unintelligible.

The challenge, then, as presently recognized, is to develop a highly integratable approach for generating shape-modulated wavelet sequences that can be used in a UWB communications system to encode, broadcast, receive, and decode a data stream.

Furthermore, the challenge is to build such a wavelet generator where the smooth power spectrum calculated by using ideal components, is realized using non-ideal components.

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