AD9864:  IF Digitizing Subsystem

The AD9864 is a general-purpose IF subsystem that digitizes a low level 10 MHz to 300 MHz IF input with a signal bandwidth ranging from 6.8 kHz to 270 kHz. The signal chain of the AD9864 consists of a low noise amplifier (LNA), a mixer, a band-pass Σ-Δ analog-to-digital converter (ADC), and a decimation filter with programmable decimation factor. An automatic gain control (AGC) circuit gives the AD9864 12 dB of continuous gain adjustment. Auxiliary blocks include both clock and LO synthesizers.

The high dynamic range of the AD9864 and inherent antialiasing provided by the band-pass Σ Δ converter allow the device to cope with blocking signals up to 95 dB stronger than the desired signal. This attribute often reduces the cost of a radio by reducing IF filtering requirements. Also, it enables multimode radios of varying channel bandwidths, allowing the IF filter to be specified for the largest channel bandwidth.

The SPI® port programs numerous parameters of the AD9864, allowing the device to be optimized for any given application. Programmable parameters include synthesizer divide ratios, AGC attenuation and attack/decay time, received signal strength level, decimation factor, output data format, 16 dB attenuator, and the selected bias currents.

The AD9864 is available in a 48-lead LFCSP package and operates from a single 2.7 V to 3.6 V supply. The total power consumption is typically 56 mW and a power-down mode is provided via serial interfacing.

Applications

• Multimode Narrow-Band Radio Products
  - Analog/Digital UHF/VHF FDMA Receivers
  - TETRA, APCO25, GSM/EDGE
• Portable and Mobile Radio Products
• SATCOM Terminals