Hi all
In a PLL contrlolled Rf amplifier front end how exactly the 1st RF stage frequency of the tuned circuit is contrlolled so it will be exactly the PLL freq+ IF frequncy ?
Thanks EC
FRONT END WITH PLL
Feb 03, 2009
7 Replies
One method that gets used is lots of switched caps with varicap fine tuning. But all-band radios are inevitably a compromise.
The key thing is to be exceptionally linear and low-noise across a large dynamic range, so intermodulation doesn't become an issue before you hit those IF filters, or you get all kinds of spurious out-of-band response. The new DTV chipsets are amazing.
The tuned circuit has a wide enough band width that a simple circuit with varactor diodes will be close enough.
The VCO tuning can also be a varactor diode. With care the voltage to frequency character of the two can be matched.
frequency of the tuned circuit is contrlolled so it
Sounds interesting What are the specs, model numbers?
M
That depends entirely (and exactly) on the radio designer. Tracking varactors, switched tuned circuits, wide-open front end -- they can all be used, and they each have their own advantages and disadvantages.
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html
Anadigics is one maker, look at their AIT-1010 and AIT-1021.
look up "RF mixer.."
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Many tahnks EC
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