Phase Detectors

  • Thread starter RLovelett
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My group had a design based on the http://www.analog.com/en/rfif-components/log-ampsdetectors/ad8302/products/product.html" [Broken] which was going to do our task of phase detection by use of what I can best tell was just some log amplifiers and
Circuit.png
.

Well the AD8302 is a TSSOP package and I cannot fabricate my own board with a package so small. So I need to make this phase detector on my own. I have found a 433MHz log amplifier like the AD8302's but can someone explain the theory of a log amplifier phase detector? Or just tell me how to make a 433MHz phase detector?
 
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  • #2
Averagesupernova
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Does the frequency vary? Do you need to detect phase at any other frequency besides 433 MHz? If not, I'm sure something can be done with a delay line and differential amplifier or for that matter a differential amplifier on it's own. The log amp issue might simply be a method to amplify very small signals up to a usable level.
 
  • #3
berkeman
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My group had a design based on the http://www.analog.com/en/rfif-components/log-ampsdetectors/ad8302/products/product.html" [Broken] which was going to do our task of phase detection by use of what I can best tell was just some log amplifiers and
Circuit.png
.

Well the AD8302 is a TSSOP package and I cannot fabricate my own board with a package so small. So I need to make this phase detector on my own. I have found a 433MHz log amplifier like the AD8302's but can someone explain the theory of a log amplifier phase detector? Or just tell me how to make a 433MHz phase detector?

You might consider just using a prototyping adapter for the TSSOP part. One name for them is "surfboard". I googled surfboard prototyping +tssop, and got lots of good hits (including a Digikey page). Here's the hit list:

http://www.google.com/search?source...L_enUS301US302&q=surfboard+prototyping++tssop

.
 
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  • #4
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can someone explain the theory of a log amplifier phase detector? Or just tell me how to make a 433MHz phase detector?

you can make a simple phase detector using a xor gate for lower frequencies, or a mixer for higher frequencies. In either case, slight phase difference will be proportional to output DC voltage.

Log amps are made of long chains of saturated transistor amplifying stages for increased non-linearity.
 
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  • #5
f95toli
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You might consider just using a prototyping adapter for the TSSOP part. One name for them is "surfboard". I googled surfboard prototyping +tssop, and got lots of good hits (including a Digikey page). Here's the hit list:
.

I don't think that is such a good idea. Using hole-mounted components at 433 MHz is just asking for trouble. You definitly need to know what you are doing, even when working with a monolithic device like this.

My advice would be to just buy a connectorized phase detector. Or, if all you are after is a change in signal as the phase changes you could do what waht suggested and simply use a mixer.

It might also be worth having a look at Minicircuits website, they sell "plug-in" type phase detectors which as far as I remember work up to about 400 MHz. They should be MUCH easier to use than an IC.
 
  • #6
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@f95toli: I used your mini-circuits suggestion and found the http://www.minicircuits.com/case_styles/TTT167.pdf" [Broken]. This should be a replacement for the other chip; its cheaper and it looks like we can actually manufacture the board for this part. Thanks very much for the help.

@berkeman: After I discussed it with the group they didn't like the idea of having to deal with extra connectors at such a high frequency. If we were going to down mix the signal we probably would have gone this direction.

Thanks everyone for the help!
 
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  • #7
berkeman
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I don't think that is such a good idea. Using hole-mounted components at 433 MHz is just asking for trouble. You definitly need to know what you are doing, even when working with a monolithic device like this.

Yikes, my bad. I skipped right over the 433MHz part of his post. Yeah, a surfboard approach would not work at those frequencies. Thanks for the catch, f95toli. Looks like your MiniCircuits suggestion worked out well.
 

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