AD607

The AD607 is a 3 V low power receiver IF subsystem for opera-tion at input frequencies as high as 500 MHz and IFs from 400 kHz to 12 MHz. It consists of a mixer, IF amplifiers, I and Q demodulators, a phase-locked quadrature oscillator, AGC detector, and a biasing system with external power-down.

The AD607's low noise, high intercept mixer is a doubly-balanced Gilbert cell type. It has a nominal 15 dBm input referred 1 dB compression point and a 8 dBm input referred third-order intercept. The mixer section of the AD607 also includes a local oscillator (LO) preamplifier, which lowers the required LO drive to 16 dBm.

The gain control input can serve as either a manual gain control (MGC) input or an automatic gain control (AGC) voltage-based RSSI output. In MGC operation, the AD607 accepts an external gain-control voltage input from an external AGC detec-tor or a DAC. In AGC operation, an onboard detector and an external averaging capacitor form an AGC loop that holds the IF output level at ±300 mV. The voltage across this capacitor then provides an RSSI output.

The I and Q demodulators provide inphase and quadrature baseband outputs to interface with Analog Devices' AD7013 (IS54, TETRA, MSAT) and AD7015 (GSM) baseband con-verters. A quadrature VCO phase-locked to the IF drives the I and Q demodulators. The I and Q demodulators can also de-modulate AM; when the AD607's quadrature VCO is phase locked to the received signal, the in-phase demodulator becomes a synchronous product detector for AM. The VCO can also be phase-locked to an external beat-frequency oscillator (BFO), and the demodulator serves as a product detector for CW or SSB reception. Finally, the AD607 can be used to demodulate BPSK using an external Costas Loop for carrier recovery.