Wireless communication technology is one of the most rapidly developing and most dynamic technical fields. In this field, various new technologies and new methods emerge one after another. Among them, Ultra Wide Band (超宽带) technology is a new wireless communication technology with huge development potential developed after the 1990s, and is listed as one of the top ten technologies for future communication.

In March 1990, the concept of "Ultra Wide Band (超宽带) radar" was proposed at the Ultra Wideband Radar Conference held at Los Alamo National Laboratory in New Mexico, USA. Ultra-wideband radar is a new type of radar, which is defined as: a radar with a fractional bandwidth (分数宽带) greater than 25% is an ultra-wideband radar.

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In formula (1), f<SUB>1</SUB> and f<SUB>h</SUB> are given by the energy bandwidth definition. If most of the energy of the waveform (generally greater than 90%) falls within the frequency range bounded by these two frequencies, then it is called f<SUB>h</SUB>-f<SUB>1</SUB > is the energy bandwidth.

UWB performance characteristics

UWB is a "maverick" wireless communication technology, which will bring low power consumption, high bandwidth and relatively simple wireless communication technology to the interface card and access technology of wireless local area network LAN and personal area network PAN. UWB has the following characteristics:

2.1 Strong anti-interference performance

UWB signals disperse weak radio pulse signals in a wide frequency band when transmitting, and the output power is even lower than the noise generated by ordinary equipment. When receiving, the signal energy is restored, and the spreading gain is generated during the despreading process. Therefore, compared with IEEE 802.11a, IEEE 802.11b and Bluetooth, UWB has stronger anti-interference under the same code rate condition. Table 1 presents the main performance index parameters of several major wireless communication technologies at present.

Table 1 Comparison of UWB and other wireless communication technologies

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2.2 High transmission rate

The data rate of UWB can reach tens of megabits per second to hundreds of megabits per second, which is expected to be 100 times higher than that of Bluetooth, and can also be higher than IEEE 802.11a and IEEE 802.11b.

2.3 Very wide bandwidth

The bandwidth used by UWB is above 1GHz, up to several gigahertz, and can work simultaneously with the current narrowband communication system without interfering with each other. This is in today's increasingly tight frequency resources. A new time-domain radio resource is opened up.

2.4 High spectrum utilization and large system capacity

Because there is no need to generate a sinusoidal carrier signal, the impulse sequence can be directly transmitted, so the UWB system has a wide spectrum and low average power, which is conducive to coexistence with other systems, thereby improving the spectrum utilization rate and bringing a great system. capacity.

2.5 Low transmit power

Since the spread spectrum processing gain of the UWB system signal is relatively large, even if a low-gain omnidirectional antenna is used, the transmission power of less than 1mW can be used to achieve several kilometers of communication.

2.6 Good confidentiality

The confidentiality of UWB is manifested in two aspects: on the one hand, time-hopping spread spectrum is used, and the receiver can only solve the transmitted data when the spread spectrum code of the transmitting end is known; on the other hand, the transmit power spectral density of the system is extremely low. cannot be received with conventional receivers.