Nuts & Volts - February 2006

will begin a testing and certification program like Wi-Fi and ZigBee.

How is this used? The plan is to use it to transmit video over short distances such as to wall-mounted TV screens and between TV sets and DVD players and other video gear. Video requires very high speeds and UWB can do it. Another application is a wireless USB port for PCs and laptops. The USB serial interface is the most widely used today with data rates to 480 Mbps. A wireless version will replace cables everywhere.

UWB is still new and just now emerging from development. But we should see some real consumer products using it this year. The Bluetooth SIG is expected to adopt UWB for their next higher speed version in the coming years, further increasing its usage.

RADIO FREQUENCY IDENTIFICATION (RFID)

RFID is the radio equivalent of a bar code. A tiny radio transceiver and a memory containing an ID number and other information is built into a tiny chip with an antenna to create what is called an RFID tag. The tag can be pasted on almost any item. When the tag is brought near an interrogator or reader unit, the tag transmits its information to the reader. A neat feature is that the tag has no battery or other power supply. Instead, the tag draws its power from the radio signal radiated by the reader. That RF is rectified and filtered into DC to power the tag. The tag then transmits its data back to the reader. The power is very low so read distances are only a few inches to a couple of feet max. Active tags with a battery give more power and can be read over a longer distance.

The original tags operated on 125 kHz, but the range was very short. Longer range units use the license-free frequency of 13. 56 MHz. Newer, second-generation tags operate in the 800-900 MHz UHF range and have a range of many feet.

RFID tags are designed for a wide range of uses. Inventory control in a warehouse, asset tracking, as well as shipping and handling. RFID is also used in automatic toll collection and payment for gasoline at the pump and

automated entry to parking areas. It is used in employee ID cards that are read to allow entry to the workplace. RFID has already been adopted by the military and many large retailers like Walmart. Look for others to use it as the volume increases and tag prices drop.

INFRARED

Infrared (IR) wireless uses infrared light to transmit data. Most TV and other remote controls use IR. Yet, it can be used for other data over short ranges. It has been used in printers, PDAs, laptops, and a few other devices. Data rates of 4 and 16 Mbps are available. The biggest limitation is the range which only extends up to several feet and there has to be a clear line-of-sight path because IR is light and can be blocked unlike radio waves. IR wireless is just a niche, but for some applications, it is a good fit. Besides, it is probably the cheapest wireless you can get.

NEAR FIELD

COMMUNICATIONS (NFC)

This is a relatively new wireless technology pioneered by Sony and Philips. The term near-field refers to the radio waves directly around the antenna which is mainly a magnetic field. The far field is made up of both the electric and magnetic fields. NFC is designed for very short range operation, typically less than 20 centimeters or roughly about eight inches. That is short range. NFC is similar to RFID in that it can be a passive communication where a device communicates with a reader or base station and derives its operating power from the transmitter. An active mode assumes that the device is also self powered, giving the device a longer transmission range. Some of the items to be NFC-enabled are cell phones, PDAs, and digital cameras. A smart card can also use it.

NFC uses the worldwide unlicensed frequency of 13. 56 MHz. The devices transmit identification information such as name and address and things like a credit card number. The data rate is 106 kbps, 212 kbps, or 424 kbps, depending on range and application.

NFC has several potential applications. First, it can be installed in a cell phone or PDA and used to make payments, buy tickets, or gain entry to certain places. In this way, it acts almost like an RFID tag. NFC is also targeted at uses such as establishing other wireless communications links such as connections between two Bluetooth or Wi-Fi enabled devices that do not initially talk to one another. By simply bringing the two devices close together, they exchange protocols and other connection data to establish a network, then the devices launch into communications by way of Bluetooth or Wi-Fi. Look for NFC this year and expanding next year.

ISM BAND RADIO

Let’s not forget those simple radios using the Industrial-Scientific-Medical (ISM) bands from about 300 to 500 MHz. Typical operating frequencies are 315 and 433 MHz. This is where your garage door opener and remote keyless entry devices work. Another common application is the wireless temperature sensor and wireless tire pressure measuring systems in some cars. When very simple data must be transmitted and no complex multilayer protocol is necessary, this is the wireless to use. The chips are cheap, plentiful, and very easy to use.

Is wireless everywhere? Not yet, but we are well on the way. And an amazing fact is that multiple radios are showing up in some devices, especially cell phones. Besides the cell phone transceiver, some handsets also contain the Bluetooth transceiver as described earlier. Some of the more exotic cell phones also contain a Wi-Fi transceiver that can be used to make Voice over Internet Protocol (VoIP) calls through any access point or hot spot. Some cell phone manufacturers are even thinking of putting ZigBee in a cell phone for remote control of home devices. And certainly look for NFC in phones. A cell phone could end up with five or six radios inside. The challenge will be to keep them from interfering with one another. Is that too much of a good thing or what? NV