Just a quick report of my experience with the AD8347 evaluation board
at 1.3GHz.
I'm using the board to convert directly to baseband, and using
Alberto's software along with an (allegedly 96kHz, 24bit) M-Audio
Transit USB audio box with a 1.4GHz Dell D600 laptop. LO and signal
inputs came from lab. signal generators.
It works. With no preamp, I can detect signals at -130dBm on ssb,
while there are just notictable strong-signal effects within the I-Q
passband at -60dBm with the receiver gain at maximum. It's relatively
easy to adjust the unwanted sideband suppression to <-70dB.
The zero frequency beat equates to ~20dB SNR in whatever the
equivalent noise bandwidth of the spectrum display is. I need to look
at transient hardware effects related to DC offsets.
This all looks good, and sometime in the next month or two, I'll
design a pcb for the 8373 and its lower frequency version.
My reason for stating to look at this approach is that I want to build
a new 10GHz receiver for EME. My current system has elements designed
in the early 1980s..! I'm looking at the Hittite quadrature mixer
chips. I'd be pleased to hear from anyone with direct experience of
these parts.
BTW in recent reviews of quadrature generation techniques, the
polyphase network, originated by Michael Gingell at STC Labs in
England, back in the 1970s seemed to have been omitted. This is a very
popular technique for obtaining phase quadrature accurately from
baseband through to VHF/UHF and microwave frequencies, and is used in
the AD8373.
73
Chris
GW4DGU
IO71sv
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