Making a 433MHz Phase Detector with Log Amplifiers

In summary, the group was planning to use the AD8302 for their phase detection task, but were unable to fabricate their own board due to the small package size. They were looking for alternatives and considered using a 433MHz log amplifier, but needed more information on its theory and how to make a phase detector at that frequency. Suggestions were made to use a prototyping adapter or a mixer, and the MiniCircuits website was recommended for a suitable replacement chip. Ultimately, the group decided to use the MiniCircuits chip for their project.
  • #1
RLovelett
5
0
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
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
RLovelett said:
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
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
berkeman said:
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 definately 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
@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
f95toli said:
I don't think that is such a good idea. Using hole-mounted components at 433 MHz is just asking for trouble. You definately 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.
 

1. What is a phase detector and why is it important in 433MHz applications?

A phase detector is a circuit that compares the phases of two signals and outputs a voltage proportional to the phase difference. It is important in 433MHz applications because it is used to ensure that the transmitted and received signals are properly aligned in order to accurately detect and decode the information being transmitted.

2. What are log amplifiers and how do they work in a phase detector?

A log amplifier is a circuit that amplifies the logarithm of an input signal. In a phase detector, log amplifiers are used to convert the phase difference between the two signals into a voltage that can be measured and used to adjust the phase of the transmitted signal.

3. What are the benefits of using log amplifiers in a 433MHz phase detector?

Using log amplifiers in a 433MHz phase detector offers several benefits, including a wider dynamic range, higher accuracy, and better noise performance compared to linear amplifiers. This results in a more precise and reliable phase detection, which is crucial for successful communication in 433MHz applications.

4. What are some key considerations when designing a 433MHz phase detector with log amplifiers?

When designing a 433MHz phase detector with log amplifiers, it is important to carefully select the log amplifiers to ensure they have the appropriate frequency response, dynamic range, and noise performance for the specific application. Additionally, the circuit layout and component placement should be optimized to minimize noise and interference.

5. Can a 433MHz phase detector with log amplifiers be used in other frequency applications?

Yes, a 433MHz phase detector with log amplifiers can be adapted for use in other frequency applications by selecting log amplifiers with the appropriate frequency response and modifying the circuit accordingly. However, it is important to note that the circuit design and component selection may vary for different frequencies.

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