Sharc-R2 Digital I/Q RF receiver project

Project overview

The Sharc-R2 receiver is an ham-radio project. The target is to build a high performance receiver for EME (Earth-Moon-Earth) applications with the latest technology :

DSP board

The DSP board is the SHARC EZ-KIT Lite from Analog Devices. Main features are :

As I need a high througput between the DSP and the Linux machine (for spectrogram), I have designed a homebrew Ethernet interface with a NS DP8391 chip connected to one SPORT.

RF front-end

The RF front-end is an I/Q direct conversion R2 receiver designed by KK7B. I have removed all the low frequency components after the dual low noise amplifier. The DSP audio input is directly connected to the output for the two I/Q amplifiers.

DDS VFO

The DDS VFO is based on a AD7008 chip from Analog Devices. A Microchip PIC16C84 is used to provide an I2C interface to the AD7008 DDS. Currently, this module is connected to the Linux PC though a homebrew I2C interface. Next step is to add I2C capability to the Sharc processor.

The DDS output frequency is close to 2.25 MHz.

144 MHz PLL module

The output of the DDS is converter to 144 MHz with a fixed modulus (64) frequency synthesizer based on a 4046 PLL. Frequency variation is done by tuning the DDS output to fout/64.

On the top/left corner, you can see the quarter wave coaxial line used to generate a 90 degres signal for the R2 front-end.

Linux GUI

For a high-performance homebrew receiver, Linux operating system is a must !

I have used the very good fltk graphical toolkit to design the GUI for my receiver. Here are some screen captures :