Re: Question about Basic TX/RX boards, the I, Q


#1

I can’t get the output to the fm_tx_2_daughterbaords.py example to
work. I am testing with 2 complex signals and on each signal, the
I channel is a sinusoid and the Q channel is a sinusoid of a
different frequency. I have connected each of the 4 SMA
connectors from the 2 Basic TX daughterboards to a different
channel on an oscope. I expect to see a sinusoid on each channel
but that is not the case. I see some weird waveform on the
different channels on the oscope. Originally I didn’t think the
TX mux was set correct because the comments at the beginning of
the example says that it transmits SSB (USB) and that is not what
I’m looking for. I want each of the 4 different waveforms (2
sines on the I’s and 2 sines on the Q’s, all with different
frequencies) to come out of the 4 SMA connectors. Any help would
be greatly appreciated.

Thanks,
Nick


#2

On Tue, Apr 03, 2007 at 09:50:20AM -0400, removed_email_address@domain.invalid wrote:

I’m looking for. I want each of the 4 different waveforms (2
sines on the I’s and 2 sines on the Q’s, all with different
frequencies) to come out of the 4 SMA connectors. Any help would
be greatly appreciated.

Thanks,
Nick

Nick,

Without a serious amount of hacking you’re not going to be able to get
4 unrelated signals out of 2 Basic Tx’s, and if you could, you’d lose
the digital upconverters.

Each I/Q pair is sent through a DUC (in the AD9862) that computes the
equivalent of

OUT = IN * exp(jwt)

where IN is the I/Q input and OUT is the I/Q output, and w is the
freqency of the digital LO.

Given how the DUC works, you can’t treat the I and Q as if they were
totally unrelated. There’s a reason they’re called I and Q, not I1
and I2.

Eric