Radio Frequency and Power Level Detection Circuit

Hello Everyone!

I want to design a circuit, which detects the resonant frequency of my 5 GHz resonator, also tells me exact S11 (reflection coefficient). The circuit will be connected to my resonator.

In short, I want to make a circuit for a Vector network analyzer (VNA). I dont want to use VNA to measure resonant frequency and dB levels of my resonator.

I want to know what components do I need to make this circuit and does it also require FPGA or Arduino programming?

Any suggestion or recommendation is highly appreciated.

Waiting for your replies. Thanks a bunch!

It's not so complicated.You will use a directional coupler to measure the reflected waves coming from the resonator and you will also use a VCO to sweep the frequency band which in you're interested.The system will sweep the VCO and will observe the reflected wave at proper port of directional coupled and using a bit signal processing methods with some digital stuffs.A good calibration is just necessary.
You realize a simple one port scalar network analyzer but if you work on it, it's also possible to realize one port vector analyzer to find out the phase of the reflected wave.

Thanks for your reply.

After reading your message I feel better and thinking it is possible.

Can you please draw an schematic diagram of how to connect things?

I have zero circuit knowledge. But I have a slightly better electromagnetic knowledge.

In fact, there are few possibilities to realize such system but some of them simpler.
If you don't have any circuit design experience, I will sketch something in couple of days for you.

Thank you very much. I will design my novel resonator at 5GHz, it will be an electromagnetic bio sensor. I have to integrate it with a circuit, and not use network analyzer. I would only need s-parameter (S11) of the resonator from entire circuit. Like one we see on network analyzer's screen.

It will be a great help if you can sketch for me the schematic, I will then order components, we have enough budget.

The system principally looks a scalar NVA.This steup can measure the magnitude of S11 but if you intend to measure also the phase of S11, the system will be more complicated.
Calibration is the key here.It should be done very carefully by connecting the directional coupler's output to "open circuit", "short circuit" and "load termination" and each termination should be registered into memory.I have put a DSP but you can use also simple an embedded microcontroller circuit or any other stuff to collect and process the data.It's a primitive system block, you can improve it by inspiration.

The setup looks clear to me now. I'm very thankful to you Sir for helping and clearing my confusion. I will order these components for 5 GHz and also I will fabricate planar calibration circuits for DC. The last block 'DSP' would be a FPGA kit or arduino kit I suppose? I will ask my DSP friends about ordering which DSP kit.

Thanks a lot for helping.

Have a nice day.

There are very good directional couplers in SMT package like this in order to miniaturize the system.
https://www.anaren.com/sites/default...ta%20Sheet.pdf

Thanks! Sir can I have your email address? Just if I have some questions, I can contact you in email. You are great helper for me in this project.

Hello!

Is there any circuit design tool where I can add these components and see if the system is working?

I want to add some more information that this system will not detect power level. It just has to detect peak value of frequency.

I want to run the simulation of this system before ordering these products online.

Can you suggest any program or application where I can perform this simulation and see if the above circuit system working.

I am ordering components from minicircuits company.

a simple balanced mixer set up in quadrature will act like a phase detector. Near resonance, the refelected phase shift off of the resonator varies wildly, with the S11 phase being zero degrees right at resonance. You can set up a circuit to work like that.

Thanks for your reply.

I want to detect magnitude, not the phase. Phase detection seems a bit more Complicated. A peak value detection of magnitude of return loss w.r.t frequency. We can call it as peak value of magnitude. It can also be called as the peak or optimal parametric retrieval system.