Norwood, Mass.—Designed for low data-rate wireless applications, Analog Devices Inc. has developed an RF transceiver dubbed the ADF7021 that operates in multiple frequency bands between 80- to 650-MHz and 862- to 940-MHz.
The ADF7021 narrowband sub-GHz CMOS transceiver is tailored for maximum range applications, such as wireless AMR (automatic meter reading), wireless home automation, industrial control and automation and remote security.
The ADF7021 has been targeted for ease of use and complies with government regulations for radio transmitters. The ADF7021 is fully compliant with European ETSI-200-220, North American FCC Part 15 and Part 90,95, and Japan ARIB STD-T67 regulatory standards.
It also delivers what ADI claims is the industry's best receiver sensitivity of -123-dBm at 1-Kbit/s, interference blocking of 60-dB at 1-MHz and +6dBm IP3.
"The ADF7021 is the only IC that meets the strict FCC Part 90 regulatory standard. In addition, it has excellent radio performance with best-in-class receiver sensitivity—6 dB better than the nearest competitor—which translates into longer range," said Doug Grant, director of business development for RF and wireless systems, Analog Devices.
The receiver sensitivity of the ADF7021 is approximately 10-dB better than ADI's previous offerings, and between 12 and 15 dB better than most competitors' parts, he added
The ADF7021 is a highly integrated RF transceiver that includes the channel filtering, easy-to-use interface to microcontrollers, and features such as on-chip temperature sensing to allow the use of lower-cost, high-temperature-drift crystals. It has an on-chip TRX switch, VCO tank and RF/IF filters, fully automatic AFC and on-board ADC.
"Their drift can be compensated by knowing the temperature change, while other radios require more-expensive low-drift crystals," he said.
By improving receiver sensitivity, the ADF7021's narrowband operation makes it suitable for maximum range operations. Wideband systems allow more noise to pass through the system, which prejudices the signal-to-noise ratio, and reduces the available range. Narrowband operation provides greater range. In addition, the ADF7021's operation in frequency bands below 1-GHz gives it better range. The range of a radio system is in part dependent on the frequency of transmission. Higher frequencies have higher loss, both in free space and in the real world.
Comparing operation at 915-MHz (one of the bands that the ADF7021 covers) with operation at 2.4-GHz (2400 MHz, where Bluetooth and WiFi operate), the signals drop by almost a factor of 10 for the same transmitter power, reducing the range by a factor of two, according to Grant.
"Unlike processor speeds, where more gigahertz is better, in wireless communications range calculations, more gigahertz is worse," he said.
The ADF7021 has both Gaussian and raised cosine data filtering options to improve spectral efficiency for narrow-band applications. The transmit section's VCO operates at twice the fundamental frequency to reduce spurious emissions and frequency pulling problems. The transmit section also contains a low noise fractional-N PLL with output resolution of <1 ppm. This frequency-agile PLL allows the ADF7021 to be used in frequency hopping spread spectrum (FHSS) systems.
The transmitter output power is programmable in 63 steps from '16 dBm to +13 dBm and has an automatic power ramp control to prevent spectral splatter and help meet regulatory standards. The transceiver RF frequency, channel spacing, and modulation are programmable using a 3-wire interface. The device operates with a power supply range of 2.3 V to 3.6 V and can be powered down when not in use.
For more specifications, please click here for a datasheet: www.analog.com/UploadedFiles/Data_Sheets/ADF7021.pdf.
To speed wireless product development, ADI is also supplying its ADIismLINK development tool. Designers can transfer data between multiple units and a master node without having to spend time developing their own protocol software.
The ADF7021 is sampling now and will be available in production quantities in November 2006. It is offered in a 48-lead CSP package and is priced at $2.85 per unit in quantities of 1,000.
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Analog Devices Inc., 1-800-262-5643, www.analog.com
