[time-nuts] New to the list...Hello from Melbourne
Lux, James P
james.p.lux at jpl.nasa.gov
Sun Aug 31 11:20:47 EDT 2008
From: time-nuts-bounces at febo.com [time-nuts-bounces at febo.com] On Behalf Of Clint Jeffrey - VK3CSJ [clintjeffrey at optusnet.com.au]
Sent: Saturday, August 30, 2008 10:52 PM
To: time-nuts at febo.com
Subject: [time-nuts] New to the list...Hello from Melbourne
As for me now, there are a couple of interests, I'm wanting to put together a receiver operating at 8.4GHz where the PLO is referenced (10MHz) from a OCXO which in turn is getting it's reference from a GPS Rx with a 10KHz output, all for the sake of increased stability, plus I have an interest in Amateur Radio Astronomy together with a small group from the Astronomical Society of Victoria (ASV) we are establishing a site here in mid Victoria, one of three, there will be some projects that will require a GPS timing for accuracy.
8.4 GHz as in the deep space Space to Earth band, or just below?
What kind of signals are you looking to receive?
Depending on what you're looking for, performance wise, the traditional approach is a DRO locked to the reference with a conventional PLL using a sampling phase detector. However, Hittite now sells some nice GaAs VCOs and VCO/PLLs in that band that you might want to take a look at, especially if you need wide tuning range (it's a real bear to get a quiet DRO to tune over a 50 MHz range). In some tests at JPL, the MMIC outperforms the DRO quite nicely.
You can either do a direct "divide down from 8GHz" into a PFD for the loop, driving the reference from a DDS, which is driven from your XO.. OR.. you can mix the 8.4 GHz down with a harmonic mixer driven by a XO. You mix down to some practical IF in the tens of MHz, then, run that into the PLL where you compare to the DDS. The approach depends on your particular phase noise and tunability requirement.
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