Analog Devices' Low Power Radio Receiver Subsystem

For most of us, two-way radios are just expensive toys, but for others, like those in law enforcement and fire fighting, they are mission critical communication tools. Analog Devices says its new IF (intermediate frequency) digitizing IC is intended for just such professional apps. The new AD9874 integrates the IF-to-digital conversion process onto a single chip that AD says can be used to design a sensitive, low-power receiver suitable for a range of equipment, including dispatcher base stations, handheld portable radios and in-vehicle consoles. The AD9874 MxFE digitizes low level IF signals from 10 to 300 MHz with a bandwidth of up to 270 kHz. Typical noise figure is 8.7 dB SSB NF and linearity, as measured by third-order input intercept point (IIP3), is +0 dBm IIP3 (typical maximum bias). The AD9874 only sucks up 21.2 milliAmps of power versus 45 milliAmps for previous generations of the IC. The signal chain consists of a low noise amplifier, a mixer, a bandpass sigma-delta analog-to-digital converter, filters and automatic gain control (AGC) circuitry capable of 12 dB continuous gain adjustment. The high dynamic range and anti-aliasing provided by the bandpass sigma-delta converter let the AD9874 cope with blocking signals 80 dB stronger than the desired signal. The AD9874 is also programmable, providing register-based digital control of AGC and filter parameters, amplifier gain and bias currents through a serial peripheral interface (SPI) port. The IC is sampling in a 48-lead LQFP (leaded quad flat package), and is priced at $19.95 per unit in 1,000 unit quantities. It should be available in Q3 2002.