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1-Newbie

## Hello Everybody, I need to estimate/predicte the circuit design of a black box using the measured impedance in the output of this box. The only hint that I have that the circuit inside the box is a demodulator, is it possible to estimate the schematic

Hello Everybody,

I need to estimate/predicte the circuit design of a black box using the measured impedance in the output of this box. The

only hint that I have that the circuit inside the box is a demodulator, is it possible to estimate the schematic of the black

box? is there any smart method to find the connection inside the box? Should I measure other things which make the

estimation process easier?  By mathcad or mathlab

It is very appreciated if anyone can help me with any information (Tutorial, literature, video, etc...) to solve this problem.

Thanks!

7 REPLIES 7
Emeritus
(To:bdjel)

Good day Bens,

I am moving this to the Mathcad community to get your question in front of the right people.

The Community Help community is for assistance with PTC Community and the Jive Platform.

Best,

Toby

19-Tanzanite
(To:bdjel)

So the only information you have is:

1) It's a demodulator

2) The output impedance

That's it? If that all you have you can tell nothing about the circuit inside. It's an electronic design problem, starting from the ground up.

23-Emerald I
(To:bdjel)

Are you sure its a demodulator .... and not an attenuator?

Luc

21-Topaz I
(To:bdjel)

There are many types of demodulators, for example: AM, SSB, FM, PM, ASK, FSK, PAM, CPSK, DPSK, MPSK, QPSK. You should know the output impedance (but is not enough, you should know at least the frequency and phase response) of each of these (non linear circuits) and, as a comparison with the experimental results, deduce the probable demodulator, and then the electrical circuit.

21-Topaz I
(To:bdjel)

Another way to know what type of demodulator there is in the black box, it might be this: to have, a "universal (namely the output can be AM, FM, PM ...)" modulated signal generator (easily available on the market), whose output is placed at the input of the black box. Test a signal at a time, with different modulation, as long as the output of the demodulator, is not the right one, That is, the modulating signal. If this output is identical to the modulating signal, you have almost found the type of demodulator That was unknown and, therefore, you can determine the circuit itself ,from the vast existing literature.

A very low cost generator, could be the following:

23-Emerald I
(To:bdjel)

What identification is visible on the box?

Get a brand name?  Maybe a model number?  There's a ton of info on the internet.

No names?  Can you get the cover open?

With only the impedance, you don't need Mathcad, you need psychic hotline!

23-Emerald I
(To:bdjel)

Do you have a physical 'black box' (that you can actually look at from all sides and measure with any equipment),  or

is it just a hypothetical black box?

Luc

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