logic in circulator for feedback from oscillator

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yefj

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Hello , i have the following system which get a feedback from oscillator from circulator.
As you can see in the lab photos i put power to port A and i need to get the dip in power at port C.
The power input which comes from A and goes into B while the feedback from the resonator is from port C.
looking at the circulator component i have ports 1 2 3 .
currently its works good i put power to port 2 and i see the "DIP" from port 3 at some frequency range exactly as shown in the article and the attached diagram.
but when i flip ports 2 and 1 i dont see such dip response from port 3
i dont understand few things:
1.why do we inject power to port 2 and not port 1?
Its like a flipped polarity. if i switch the ports and i dont get any dip like as i see when i put power threw port 2.
looking at the diagram from wikipedia why do i see a good dip frequency response from port 2
Thanks.






 

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General comment, I don't like to have at least 3 threads discussing operation of cavity stabilized oscillator (not to consider many other threads discussing supporting circuitry). Problem is that you need to refer to other threads or duplicate information.

cavity stabilized oscilator functionality question

Hello, there is a schematic sof a cavity stabilised oscilator shown bellow, taken from the attached article. first we have our YIG source which producin a 10GHZ signal with noise around it. It gets amplified and put into a cavity resonator which produce a pure signal at 10GHZ. I cant understand...
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strategy for designing a locking component in PLL

Hello,there is a circuit shown below taken from the attached article, where we put a YIG signal to a cavity resonator(from A to B) . Then for feedback we lock on the point of the dip. this dip is supposed to be a resonance of a cavity. resonance is when the magnetic energy equals the electric...
www.edaboard.com

As the general operation has been discussed in the other threads, I'll restrict my answer to the obvious

Do you have any doubts that circulator direction in circuit diagram from IEEE article could be wrong? If not, you only need to verify that the circulator used in your hardware is connected and working correctly, e.g. with VNA or power meter. Or are you seriously asking if the circuit can work with CCW circulator operation?
 
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Signals go clockwise , unless you live upside down or "down under". just kidding.

When matched ports, the differential in permeability acts like a prism to deflect the path in 1 direction for each port.

So if you want the signal out of port 3 then driving from port 1 is backwards "in the traffic circle."

The isolation in the reverse direction must be -36dB at fo from 1 to 3 and after directional couple and adjustable pad, the carrier is further suppressed to 90 dB with the combiner/splitter.

Why are some SMA connectors so banged up? Did you torque them properly too? Better make sure your cables are working as expected with a VNA.
--- Updated ---

Are these rated for Cryogenic temperatures?
 
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Hello,I have tested my circulator in network analyzer and i saw the following pattern.
the system acts as shown below.
I measured the signal which passes from port 2 to port 1 while port 3 is open circuit.
when i plug a termination on port 3 i see -25dB of energy passing from port 2 to port 1.
when i plug the resonator i see something in the middle
so i understand that the energy ability to pass from port 2 to port 1 linked to the resonance of the resonator at port 3.
How the resonances are linked to the reflection coefficient from port 3?
Thanks.






--- Updated ---

UPDATE:
At resonance the circulator sees 50 Ohm so all energy goes to port 3 instead of port 1.
thats why port 1 is feed back
sorry FVM for this question i needed to understand how the circulator and resonator work together.
Thanks.
 

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When I said check circulator operation with VNA, I was thinking about testing the circulator without cavity, terminating the third port with 50 ohm load. Cavity S11 and S21 can be also checked by VNA.
 
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This seems to be your circulator model:

In the graphs you can see the thru pass measurement from P1 -> P2, with P3 terminated into 50 Ohm.
You can also see that P2 -> P1 is isolated, with P3 terminated into 50 Ohm.

Keep in mind the specified frequency range: 9.2 to 10.5 GHz
 

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volker@muehlhaus said:
Keep in mind the specified frequency range: 9.2 to 10.5 GHz
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The sweep frequency range of 5 to 11 GHz shown in post #4 involves two problems:
1. Circulator is operated outside useful frequency range.
2. High Q cavity resonance won't be possibly even seen.

I suggest to start with identification of cavity resonance frequency and reflection characteristic using appropriate VNA settings (frequency resolution < 100 kHz) Once you are sure to see the expected resonator behaviour, you can try in combination with circulator.
 
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If you calibrate each component then you model it and simulate the loop.

This is starting to resemble reverse engineering a concealed radar weapon or bomb detector without prerequisite skills using scavenged components.
 
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