Project Wireless - February 2009 - (Page 17) PrOjeCT SPonSor aDvertISement DlP DeSign RFiD ReADeR/WRiteR At Digi-Key from digi-Key, dlp design’s dlp-rfidlp8c is a low-cost, usB-powered module for reading from and writing to iso 15693, iso 18000-3 and tag-it™ intelligent rfid transponder tags. it has the ability to both read and write up to 256 bytes of data in addition to reading the unique identifier (uid/sid). all of the dlp-rfid-lp8c’s electronics reside on a single, compact pcB, and all operational power is taken from the host Windows/Windows ce/linux pc via the usB interface. up to eight external antennas can be connected via standard sma connectors. clIck here for aDDItIonal InformatIon | vOLuMe 1 | nuMber 1 antenna. the size and mechanical constraints of the device, as well as the electrical requirements, also determine the type of construction/ technology to use. most of these internal antennas can be mounted through a smd process, smt process, pogo pins, spring contact, mini u.fl/i-pex connector or direct solder. When long-feed cables are used, it is important to factor in signal loss from the cable, which can be several decibels. the ability to solve some of the most demanding design issues in small, handheld devices with multiple radio applications will narrow the antenna selection and the type of technology needed. some of these challenges are isolation, minimum gain and efficiency, hand/body effect and specific absorption rate. isolation becomes an issue when multiple antennas are located close together in a small handheld device. antennas that operate in the same or in a close frequency range couple among themselves and cause a reduction in performance. the minimum gain and efficiency requirement becomes a challenge in small devices due to proximity to other components such as the lcd, metal shields, battery and other electronic components. the lowerfrequency applications, such as 850and 900-mhz bands, are challenging due to the longer wavelength in the lower operating frequencies. hand/body effect requirements become an issue in a handheld device due to frequency detuning when the device is held close to human body tissue. the resonance frequency will be shifted out of band and cause a high attenuation in the signal due to impedance mismatch and degradation in antenna performance. also, the tissue near it absorbs the radiated energy from the antenna and prevents the signal from propagating to the open air. likewise, sar requirements should be considered due to regulatory requirements. due to the high isolation property and distributed nearfield radiation of these special ceramic antennas, sar and body/hand effect can be reduced Contents viewpoint Smart integration design Signal Paths in 3G and Feature / Smart Phone Apps Antennas for Handheld devices Home Page Product Training Module Online Ordering Suppliers Catalog 17 http://ad.doubleclick.net/clk;211088645;32661511;z?http://www.digikey.com http://ad.doubleclick.net/clk;211153876;32661511;y?http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=813-1020-ND http://ad.doubleclick.net/clk;211088645;32661511;z?http://www.digikey.com http://ad.doubleclick.net/clk;211088750;32661511;w?http://digikey.com/PTM/PTMMaster.page?site=us&lang=en http://ad.doubleclick.net/clk;211088807;32661511;z?http://ordering.digikey.com/ordering/addpart.aspx?site=US&source=search http://ad.doubleclick.net/clk;211088983;32661511;e?http://digikey.com/Suppliers/SupplierIndex.page?site=us&lang=en http://ad.doubleclick.net/clk;211091911;32661511;p?http://dkc1.digikey.com/us/en/pdf/Current.html
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