Sunday 30 March 2014

SDR Front End

Work on developing the Arduino SDR continues with the rationalization of the front end into a plug-in module...


This little unit combines the quadrature clock generator section of my DDS shield, as implemented on a brace of 7474's and the switching Tayloe mixer, built around the 74CBT3253. These surface mount goodies, which add up to the same kind of front end seen on "Softrock"-type SDR systems, are mounted on a little PCB about 3 * 5 cm...


The new board makes it easy to build up the front end of a software defined radio using "building bricks" plugged into a solderless breadboard, as in the case below, which includes one of my standard plug-in 40m bandpass filters, a DDS module for clock generation and the new board...


I'm taking this path away from the DDS Shield used previously, in preparation for some experiments with the Si570 - which will be required to get the x4 clock rates required to achieve coverage of higher HF bands.

Here's the entire Arduino SDR receiver with the new front-end module...


Cleaning up the layout (with the new module) seems to have brought about an attendant clean up of the noise performance of the receiver - but that's just a subjective impression and may be no more than wishful thinking!

...-.- de m0xpd 

2 comments:

  1. Am having ZERO success here trying to do the same thing! Any change you can email me the schematic? antonywatts at me dot com

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  2. By the way have you looked at LTC6904 as a clock?

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