[hpsdr] Taylor series corrected DDS

[pvharman at arach.net.au]

Just came across this technique for improving the performance of DDS.

http://www.xilinx.com/xlnx/xebiz/designResources/ip_product_details.jsp?
key=Direct_Digital_Synthesizer



Looks like an interesting  and relatively low overhead way of reducing DDS 
spurs.

73's Phil...VK6APH