saulbit
Member level 4
I am dealing with a receiver circuit, in which I have to use the HMC547 to realize an about 40dB isolation for the frequency from 4GHz to 20 GHz. According to the datasheet of the HMC547, the isolation would meet the demand. However, when I use the Rogers 4350 PCB material, the isolation is very bad, such as about 15dB at 4 GHz, less than 10 dB at 20 GHz. The measuring method is that one port of the SPDT ( such as RF1) is loaded by a 51 Ohm resistor, and the other port is sent into the spectrum. The RFC port is provided with the input frequency. The control circuit is OK. So what is wrong with the circuit? I have used some absorbative materials.