Hi Cris ... > 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.
Great! I was looking at some similar chips from both Intersil and National. They have a built in quadrature generator, so the LO can be at the fundamental freq. But what scares me was the NF (best was 21dB). Those equivalent chips I have. We (companhy) use them as IQ demods for some high capacity QAM modems and since there�s LNA/IF Amps before the NF is not a problem. But the AD8373 have "only" 11dB. Any LNA can make this drop to the 0.5dB NF level. > 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. I used some a time ago ... but it was a die version.I don�t remember which one (prototyping 2 y.a.). At that time the mixers they carry for such frequencies requires bond wiring. I guess today they have encapsulated units. I left this designs in stand by for a while because our target is/was a common platform from 6 to 23GHz with quadrature demodulator. And most of this chips will need some sort of external trimming on PCB/levels/phases to improove sideband supression. I guess on narrow band 10GHz this can be done easily. For wideband apps I guess we need to develop our own wideband I/Q demods :o). Centellax carry some (6 to 20GHz) but are expensive (1400 USD) and LO must be 2X received freq (e.g a 20.5GHz LO for 10.25GHz RX). > 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. This supose to be my last question: how AD8373 generates quadratre on such wide band :o). Answered above. 73 Marcus PY3CRX/PY2PLL http://py.qsl.br -- Internal Virus Database is out-of-date. Checked by AVG Anti-Virus. Version: 7.0.308 / Virus Database: 266.10.2 - Release Date: 21/4/2005 Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/soft_radio/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
