QUESTION

Question

Dear sir,

According to your instruction, I setup testing. Network Analyzer (E5071C) connect to RFO series 22pF. And 1.8VDC power supply to VCC series 47nH. But I found Network Analyzer has a problem after I tuned M20057 matching with 1.8VDC. My Network Analyzer return loss cannot go back to 0dB in 1559MHz-1609MHz when I preset Network Analyzer. Is Network Analyzer damaged in Port1? Or other reason?

It is because I need to tune second version PCB board for M20057 module. Can you comment it. Thanks in advance.

Best regards

Harry Cheng

Answer 1

Hi Harry,

You need to place a Bias T between your network analyzer and the coax cable going to your M20057 to supply the DC voltage to the LNA. This ensures the DC voltage does not feed back into the NA.
Also check your input max dB in your NA to make sure the receiver front end can handle the amplified signal. If the amplified signal is higher that what the NA can receive put a attenuator pad between the Bias T and the NA to reduce the signal to the level the NA can handle.

Which side of the 22pF capacitor was the coax that sends the signal to the NA placed? It should be placed between the capacitor and the GPS receiver not on the antenna side of the capacitor.

Best regards,

Geoff S