在9月2日我的博客ndWhatever Happened to Ultrawideband Wireless?I only mentioned the WiMedia Alliance’s multi-band (MB)-OFDM form of UWB and its continued usefulness. However, two other companies reminded me that there are other methods of UWB that are still around. Here is a quick look at what else is happening in UWB.
UWB最初是无线的冲动形式。短波被传输以表示使用脉冲位置或相位的位。UWB的这种形式在某些应用中存在问题，但仍用于地面穿透雷达齿轮。然后，一群制造商发明了MB-OFDM UWB，以适合FCCS对UWB的定义。这种形式称为Wimedia，以确保其定义UWB定义的最低500 MHz带宽要求。WIMEDIA格式使用128 OFDM子通道各4.125 MHz宽，以创建使用BPSK或QPSK调制的528 MHz OFDM UWB信号。发明了多个528 MHz频段，以覆盖FCC指定的UWB光谱从3.1到10.6 GHz。
The standard received a huge amount of support and about a dozen companies started making chips. The goal was to create a wireless USB device. And most of them did but only a few were ever commercially successful. Because of the complexity of the WiMedia UWB and its speed and range short comings, it never became mainstream. With 802.11n Wi-Fi coming along about the same time, WiMedia UWB quickly faded away. But, as I pointed out in the earlier blog, this form of UWB from Alereon has unusually good security characteristics so is now finding application in military and medical applications.
Paul Dillon ofPulse~LINKinformed me that there is another promising UWB form is called CWave. Invented by Pulse~LINK, this method is far simpler than the WiMedia standard and offers some interesting features and benefits that are worthy of note. CWave uses a continuous 4 GHz carrier modulated by a 1.35 Gb/s digital signal creating the familiar sin(x)/x shaped spectrum with the major nulls at 2.7 and 5.3 GHz. This spectrum is then filtered into a band pass from 3.3 to 4.7 GHz meeting the FCC’s requirement. The modulation is BPSK. This arrangement supports a 1.35 Gb/s data rate. CWave uses the popular Low Density Parity Check (LDPC) coding to provide some process gain. This results in a 900 Mb/s net data rate over short ranges.
与Wimedia格式相比，CWAVE确实很简单。它不需要所有超级快速的ADC和DAC，均衡或快速的FFT/IFFT处理。结果，它具有更少的电路和较低的功耗。它不需要PA。功率水平仍然是-41 dBM/MHz。在此功率水平上，与任何UWB一样，该范围仍然受到限制，但是在较低速度下，在理想条件下可以达到10米。
关于CWAVE的整洁的事情是，可以将载体放置在UWB频段内的任何地方。此外，QPSK或8PSK（例如8PSK）的更高级别可以将总数据吞吐量分别提高到2.7 GB/s或4.05 GB/s。至于无线应用程序，CWAVE非常适合室内视频流或USB连接。它也适合一些医疗和军事用途。
A unique application of Pulse-Link’s CWave is UWB over cable. Yes, cable. It can carry Ethernet over coax for example. CWave apparently operates well over the home-installed 75-ohm coax (RG-59/U and RG-6/U including splitters. In addition it could find a way into cable TV or satellite TV systems as the signal can be positioned higher than the current DOCSIS or satellite spectrum (above 2 GHz) on the cable. Pulse-Link has basic chipsets now with a GEN2 version on the way.
Another interesting UWB still around is impulse radio (IR) UWB. It uses the short Gaussian pulses for real time location systems (RTLS). Dublin-basedDecaWaveas created both chips and modules using this method. Their DW1000 IC operates on one of six channels in the 3.5 to 6.5 GHz range with a bandwidth of 500 MHz to meet the UWB definition. Data rates of 110 kb/s, 850 kb/s and 6.8 Mb/s are available. The chip is fully compliant to the IEEE’s 802.15.4-2011 standard that added the UWB PHY. The chips, called ScenSor, are designed to build location-based devices. With the short pulse technology, the chips and modules can locate items within 10 cm. Amazing.
CWave and ScenSor devices are certainly worth a look if you are considering fast short-range wireless technologies.
