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[Discuss-gnuradio] Low frequency (original and custom DC) daughter board
From: |
Krzysztof Kamieniecki |
Subject: |
[Discuss-gnuradio] Low frequency (original and custom DC) daughter boards problems |
Date: |
Sun, 15 May 2005 23:16:34 -0400 |
User-agent: |
Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.7.5) Gecko/20041217 |
A project that I am working on is using a USRP to generate pure tone signals and measure those
signals after they have passed through our "black box" application. We need to measure down to DC so
we have modified the TX and RX boards with "granddaughter" boards.
We have run into a problem which can be seen on both the original daughter boards and our modified
ones. There seems to be bleed through from the TX boards to the RX board, at frequencies up to 8kHz.
Test setup:
- Running the USRP with one TX board and one RX board
- Nothing is connected to the SMA connectors
- One TX DAC is outputting a pure tone generated by gr.sig_source_s
- One RX ADC output is being mixed with a gr.sig_source_c using a gr.multiply_cc. The output is then
filtered with gr.fir_filter_cc
(response graph, of original RX & TX boards, here
http://www.kamieniecki.com/krys/gnuradio/AC_front_end_cropped.png) It looks like the response of a
lowpass filter to me.
Does anyone have any ideas before I get together with our EE?
BTW:
We are getting nice strong clean signals at 9kHz, when we connect the TX to
the RX.
For TX we use an AD8057, and for RX we use an AD8138.
I'm also looking into releasing schematics for these "highly advanced"
modifications.
--
Krzysztof Kamieniecki
callsign:KB1KLB
mailto:address@hidden
- [Discuss-gnuradio] Low frequency (original and custom DC) daughter boards problems,
Krzysztof Kamieniecki <=