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