The Emperor's new technology

AUTHOR: Inavate

Audio-Technica caused a stir at InfoComm this year with the announcement of SpectraPulse, a new wireless microphone system based around a technology called Ultra Wideband. Chris Fitzsimmons takes a closer look at SpectraPulse and Ultra Wideband to see what potential it has elsewhere in AV.

You will no doubt have heard the term broadband, you may well have heard the terms narrowband and wideband, but what about Ultra Wideband (UWB)? First some definitions. narrowband, when used in the context of the study of wireless channels, implies that the message bandwidth is not wider than the coherence bandwidth of the channel and that the width of the channel is small enough that its frequency response can be considered flat. The opposite state of affairs is known as wideband. This is where a message exceeds the coherence bandwidth of a particular channel.
ultra-wideband is an extension of this, but it works in a very different way to other Radio transmission methods. Rather than putting a lot of energy into a particular frequency on the RF spectrum, as you would with a narrowband signal, in ultra-wideband the energy is spread across a very wide range of frequencies but at much lower power at a given frequency. So in narrowband digital transmission, a peak of energy in the frequency would be recognised as a 1 by the receiver, and a low in the frequency would be a 0.

The concept of UWB is actually fairly simple – send a fast, known pulse sequence, identify the sequence by looking for the sequence and known pulse characteristics, synchronise to the pulse train and decode the information.

Matt Nelson, currently Director of Marketing for Avocent, and formerly of UWB start-up company Time Domain explained: “What UWB does is takes that one peak of RF energy in a single frequency and smashes it. So rather than bandwidth being vertical in the scheme of things it’s broadened over a whole range of frequencies.
“Fundamentally you’ve moved out of a frequency based domain, and moved into a time domain, so lets say you have this energy spread over the 3-5GHz range, a total of 2 GHz. But what you do is open a window of time in which you can look for that energy in that specific clock cycle. So you have a radio receiver that listens only in particular time intervals to see if there is energy there. If there’s energy there it’s a 1, if not it’s a 0.”

So what?

The first important thing about UWB transmitters is that they emit below the so-called fundamental noise floor of all electronic devices. Anything electronic, be it your mobile phone, computer monitor or desk fan emits some degree of RF energy. UWB devices operate below this noise level which means that in countries where the technology is allowed, they don’t need to be licensed because they don’t interfere with other radio technologies, they are lost in the background noise.
The second thing is that compared to other wireless technologies, the radio architecture is flipped on its head. In conventional applications, it’s all about the amount of power you can push out through a particular antenna. However, in UWB the key is the sensitivity of the receiver being sufficient to pick out the signal from the rest of background noise.
This two properties are the ones that Audio-Technica have taken advantage of in the development of SpectraPulse in which they partnered with UWB experts Multispectral Solutions Inc. But more on that later. But first, here’s a bit of background to UWB.

In the beginning

When UWB was first conceived almost ten years ago, it promised the earth. The idea was that by spreading bandwidth across a wide spectrum you could have bit rates of hundreds of megabits over a wireless connection for very low power inputs. We were therefore going to have great battery life for mobile devices, and be able to transmit video, audio and data. But the harsh reality of the situation was that you can’t get all of those things at once. Physics has a nasty habit of getting the way of brilliant ideas. What the chip manufacturers found when they actually started making the devices was that they could have low power or high data rates but not both.

Dr Robert Fontana, President of Multispectral Solutions explains the compromises necessary: “What they realised was that the initial assumptions were all nonsense. They had this device with gobs of gobs of bandwidth, but to translate that to gobs and gobs of data-rate you need gobs and gobs of power. These things needed fans to cool them, not particularly conducive to a mobile device. Drawing a watt of power means you need to change your battery every 15 minutes.
“In my view, the sweet spot for this kind of technology is a bit rate of below 10-20 mbits. At that kind of level you can get a decent range, around ten metres, which is ideal for PAN (personal area networks), and excellent battery life.”

What is it good for

So if UWB isn’t allowing us to toss the wires out the window just yet for HD video and HDMI, what is it good for? Well one thing it’s great for is audio, as Audio-Technica has discovered. SpectraPulse uses UWB to transmit uncompressed digital audio at data rates of about 8mbits/s. The product operates with an audio bandwidth of 100-12,000 Hz and uses 16bit digital audio with a 24kHz sampling rate.

Security is another important benefit of the system. As previously mentioned, it operates below the noise floor and is therefore inherently hard to detect, even with sensitive test equipment. Also, because UWB works on pulses of data rather than continuous transmission like traditional FM signals they are again hard to detect or decode. SpectraPulse transmits at 40 nanowatts average power. This is approximately one million times lower than an FM system.

If that wasn’t enough, A-T has developed an option 128-bit encryption feature for particularly sensitive applications. This feature allows the microphone and audio control interface to be encrypted and keyed to each other so that even someone with another SpectraPulse system would not be able to decode the signals.

Another company just beginning its journey down the UWB path in the AV space is Gefen. President and CEO Hagai Gefen had this to say about the company’s current generation of products: “Gefen’s Wireless for HDMI Extender uses a UWB-based chipset from Tzero Technologies, combined with Analog Way’s compression technology to deliver an HDMI signal up to 30 feet, for high definition audio and video signals. Small sender and receiver units connect the HDTV source to the display or projector with no cables required, making it ideal for difficult installation spaces.
“We see these solutions as just the beginning of a trend that is steadily gaining influence over the industry as standards become regulated as technologies advance in reliability and performance.”

One thing to note is that both A-T and Gefen’s products are currently only available in the USA. However the, the European Commission has ratified the UWB standard and by the time this article hits the streets, the resolution will have been adopted. Whilst A-T are understandably unwilling to put a precise date on when SpectraPulse will be available in EMEA, the time scale bandied about is 18 months or so. These companies are the vanguard and you can expect to see several further developments from elsewhere in the market over that time.

One note of caution, like so many other technologies before it that have promised to do away with wires forever, with UWB you don’t get something for nothing. Wireless HDMI may be extremely useful, but for the foreseeable future you’re still going to need to plug the display into a power socket.