I have recently built a module which up-converts a baseband signal between 90 and 190 to an IF signal between 2263,5 and 2363,5 MHz. This module needs an OL signal of 2453,5 MHz @ 0dBm which passes through a buffer amplifier consisting of a band pass filter, an amplifier and an attenuator. The OL reaches the mixer with a level of +12 dBm.
Now that I have exposed the situation here is the problem: the OL tone is interfering every part of the PCB. When I connect the spectrum analyzer to either the output or the input of my circuit, there is a tone of 2453,5 MHz and a considerable level. In fact, if I desolder the AC coupling capacitors, so that there is no physical conexion in the microstrip circuit between the three ports, the interference is still in both the input and the output.
It seems that the OL is interfering all the circuit through the air.
Please, do you have any solution to avoid this interference? The box is already in an aluminium enclosure box.
Thank you very much in advance.