Smart Antennas – Enabling Coopers Law

Wireless systems have come a long way in the last ten years due to the penetration of mobile telephony. The antenna is one aspect of a wireless system that is seeing emerging technologies under active development. Traditional antennas broadcast a signal in all directions spreading the power of the signal over a wide area. One way to improve the performance of the antenna is to create a series of cells with an antenna at the center of each cell. This strategy is used by the mobile phone industry. The second strategy places two antennas near to each other and then switches back and forth to get the best signal. This helps eliminate problems caused by multipath fading. Finally, there are smart antennas which use a series of antennas and DSP algorithms to create a more efficient transmission/reception of signals. Smart antennas are also called adaptive array or switched beam.

In this tutorial on smart antennas the author uses the analogy of how one uses hearing to detect the direction of a sound. Smart antennas use multiple antennas to determine the direction of an incoming signal and then transmit back in the same direction; thus providing more efficient reception and transmission.

One type of smart antenna is the MIMO which stands for Multiple Input Multiple Output, which was first investigated by Jack Winters at Bell Labs in 1984. Instead of fighting the problem of multipath fading, MIMO takes advantage of it. Multipath fading is caused by a radio signal bouncing off structures and topographies creating multiple signals which reach the antenna at different times and from various angles.

The Wireless Networking and Communications group at the University of Texas is one example of research in the area of Smart Antennas. Brian Evans researches the use of digital signal processing algorithms to improve the performance of the communication signal. Time equalization shortens the duration of the transmission while frequency equalization mitigates magnitude and phase distortions.

Smart antenna technology is not only under development in the University, but is also deployed by industry. One company on the forefront of Smart Antennas is ArrayComm. Their president, Martin Cooper, articulated “Cooper’s Law” which states that the number of conversations (both voice and data) has doubled every 2.5 years since radio waves were first used for transmission – that’s 104 years ago. This increase is due to several technology improvements including frequency division, modulation techniques, spatial division, and the increase in usable spectrum and now smart antennas.

Lyrtech makes FPGA and DSP-based platforms for smart antenna development which is all about providing higher data rates and higher capacities on the wireless network. Bandspeed is an Austin company that applied Spatial Division Multiplexing to WLAN applications, which adjusts the transmit power and sectorizes the physical coverage of the RF signal.

As wireless becomes increasingly important to our communications infrastructure, the need for bandwidth will grow. Smart antennas are an important technology in this area.

Best regards,
Hall T.

Web to Mobile Applications – Portability and Location

The web is now reaching out through mobile phones creating a space rich in emerging technologies. Applications are appearing in numerous places. Bones in Motion is one of my favorites. The mobile phone keeps track of a runner’s location and sends it back to a web-based application which then tracks his performance. If you’re a biker or runner simply take your phone on a jog, and when you return, your distance, time, and pace are logged on the internet and compared to your previous results.

Berggi started by a long-time friend, Babur Ozden is a social networking software that let’s mobile phone users share files such as mp3-based music and photos. It’s aimed at the Teen and Tween market, and is a good example of how file sharing between mobile phone users can be implemented.

At the recent SxSW festival held in Austin, a social networking software called Dodgeball gained prominent attention due to the large cluster of people using it. Dodgeball let’s you create a list of friends. When you “check-in” it tells you if anyone on your friends-list is in your area say a local restaurant or bar.

Backend technologies from Microsoft have been around for awhile now. With the advent of .NET, Microsoft created a foundation on which to build web-based and then web-mobile applications. Microsoft offers the Advanced System Format which is a file format storing synchronized multimedia data which comes with a series of codecs for encoding, streaming, and playing data from the file format. C# is a popular language for those developing Mobile-Web applications. In this article, the author describes how to convert a C#-based program from the web to a mobile device. It basically boils down to changing the controls, the links, and text font sizes to work on a mobile device.

Nokia lists emerging technologies including web services, Python, SIP, and more.

Radio over the mobile phone is another application. Numerous vendors offer downloads to let you listen to the radio on your phone. Spodradio is one example.

All of these technologies can support Virtual Instrumentation. The mobile phone is simply an extension of the web but adds a new element – Location. For measurement applications, location can be critical. When we were developing the LabVIEW on the PDA numerous users needed to tie their measurement to a geographical position. There was one application on a Navy frigate where the seamen were tasked with making a measurement in a particular location on a ship. If the measured temperature came out over 90 degrees F, then the seaman had to file a report and take corrective action. Surprise, surprise, the measured temperature never came out over 90 degrees but topped out at 89.5 F, most of the time. By tying the measurement with a location, one can truly know what the temperature is.

Best regards,
Hall T.

Medical Imaging -- Using RF, Ultrasonic, Nuclear and Even Holography

Medical imaging uses a variety of techniques to produce images of the human body. Radiography creates images by exposing x-rays to photographic film. Computed tomography is a series of x-rays taken from different angles and then joined together to create a cross section of the subject. Magnetic Resonance Imaging uses absorption and emission of RF energy to generate images of a subject. Ultrasonic imaging uses sound waves in the 1-15 MHz range.Virtual Instrumentation applications abound for each of these techniques. TU Delft in the Netherlands has developed a high resolution ultrasound scanning system for the detection of cervical cancer. It measures the pulse-echo traces at up to 16 revolutions per minute to create a radial image. Stanford University School of Medical developed an ultrasonic application based on micromachined transducer arrays. It uses a probe architecture for volumetric scanning. This architecture generates higher sensitivity at a lower cost.

Nuclear Medicine Imaging also called Positron Emission Tomography (PET) measures radioactive substances (injected into the subject) such as Carbon-11. PET systems use a circular shaped gamma ray detector to measure the radioactive elements, converting the gamma rays into photons. A photomultiplier tube converts the photons into electrical signals.

A number of emerging technologies are coming into play for medical imaging applications. Bio-holography or what is also called Beo-tomography places minor body parts such as the human finger into an electromagnetic field to generate holographic images of internal organs. While still in the research phase, they have tested over 8000 patients.

RF Current Density Imaging is an MRI technique that uses electromagnetic waves to measure magnitude and phase from which one can create an image of the subject.

Harris Technologies developed a technique called hyper radar (requires subscription) for medical imaging.

These emerging technologies seek to produce finer images at a lower cost by making better use of RF waves.

Best regards,
Hall T.

Wireless Medical Telemetry Systems

Telemetry has been around for a long time such as in the utility business for meter reading. A more recent use case is the medical industry which uses biotelemetry to transmit a patient’s condition – heart rate, temperature, etc, to a wireless receiver that can monitor and provide data to healthcare provider.

There are some more historic examples of Biotelemetry. In this web-site Swedish scientists implanted devices (through the nostrils) into patients’ brains for purported brain control. The web-site reads like the script to a bad B-movie.

A more conventional use of biotelemetry is for heart monitoring. Wireless telemetry from implanted medical devices provides obvious benefits. In the cardiology area, Transoma Medical is one example of a company that makes wireless telemetry systems for cardio monitoring.

This patent describes an implanted device which is powered by the heart tissue through piezoelectric energy converter and modulates the signal based on the activity of the heart.

Wireless Medical Telemetry Service (WMTS) operates in the 608 to 614 MHz frequency range, with other frequencies (1395 to 1400 MHz, and 1429 to 1432 MHz) set aside for general medical telemetry.

The FDA has strict guidelines on the use of WMTS which can only be administered by a licensed physician or hospital. Since WMTS shares radio spectrum space with astronomy applications, WMTS cannot be used within 80Km of an astronomy station. Due to the lack of available spectrum space, medical telemetry has made use of unused bandwidth in broadcast television, in particular, channels 7-13. With the advent of Digital TV, that spectrum is now being used by the primary user -- the TV broadcaster forcing WMTS providers to find bandwidth elsewhere in the spectrum.

Virtual instrumentation brings tools for organizing the data received from a wireless medical telemetry system. In this example researchers from Kansas State university, used LabVIEW and a MySQL database to organize the captured data from what they term a Wireless Body Area Network. (WBAN)

For a primer on WMTS, click here. For a detailed list of biotelemetry resources, Texas A&M offers a rich web site.

Best regards,
Hall T.