[Discuss-gnuradio] Halfband interpolator stages for FPGA transmit chain of USRP1

[Dominik Auras]

Hi GNU Radio community!

Because the halfband interpolators are disabled in the current USRP1, I 
have investigated to reactivate these. However it turned out that it was 
easier to integrate the new implementation I have found in the USRP2.

So I have added the USRP2 halfband interpolators to the USRP1 fpga code 
 base. The result is a new transmit chain with 2 cascaded halfband 
interpolator stages, each of them using the 31-tap halfband 
interpolators from USRP2.

The included configuration gives an FPGA bitstream that supports one 
receive chain (w/hb) and one transmit chain with halfband filters. About 
96% of the FPGA resources are in use.

I have tested the transmit chain with my USRP1s and it worked fine.

Please note that all I have done was to merge part of the USRP2 verilog 
code into USRP1. Except for a few adjustments, there were no big 
changes. These excellent modules I have reused have been created by Matt 
et al.!!

You find some documentation and the downloads at my site:

http://www.dominikauras.de/gnuradio/usrp_txhb.html

Best regards Dominik