Circuit Board is not working properly at 2.4GHz

[FvM]

Please show a photo or drawing of the PCB layout and clarify how the 500 ohm RF probe is connected to the circuit. Only "barrel" or short ground clip can reproduce 2.4 GHz correctly.

As far as I understand, you have the generator unterminated (please correct me if I'm wrong). This can be expected to cause some additional magnitude error due to non-perfect generator output matching, but unlike in a 7 dB order of magnitude.

 

[volker@muehlhaus]

As far as I understand, you have the generator unterminated (please correct me if I'm wrong). This can be expected to cause some additional magnitude error due to non-perfect generator output matching, but unlike in a 7 dB order of magnitude.

Frank, that is very possible if he probes the location-dependent standing wave voltages on the unterminated line. That can be twice the 50 Ohm voltage (at open end and n*lambda/2 locations) or zero voltage (at 1/4 lambda + n*lambda/2 from open end).

I agree he needs to show a photo of the test setup, including probe connection.

 

[FvM]

That's of course possible if we have a line of sufficient length, not probed at the end. According to the (vague) description, I was expecting only short traces on the PCB.

 

[pawalepravin92]

This looks a high impedance probe.
Above you wrote: "I have taken a Bare PCB and just mounted a SMA connector at input. "
It is no surprise that you measure nonsense results if you probe a line that is not properly terminated.

~~

Also, I can't believe the frequency rating of the probe. The ground path connection is way too long at these frequencies.
Edit: Ok, that's even documented here

View attachment 149647

Thank you sir,

"I was just trying to see the difference in result at 1.2 GHz and 2.5 GHz, without terminating. And able to see the 8 to 9 dB difference, so I was worried." Sorry for that.

So then please help me out to find the reason that Why my circuit is giving 8 - 9 dB extra loss at 2.5GHz.
I will share my circuit and layout.

 

[volker@muehlhaus]

Your
measurement
method
is
wrong.

Don't
trust
measurement
results.

Learn
to
do
correct
RF
measurements.