Question

What are the possibilities the rf pcb board can fail?
At the transmitting port?
When device under testing is power supply, vector signal generator, and signal analyzer?

Answer 1

A few Possible failures of RF PCB board are listed below:

1. Interference between Digital and RF/Analog modules of PCB:

When RF circuit and digital circuit modules are working together on a single board with the same power supply, more chances are there that the total system becomes instable because of digital signals swing between ground and positive power supply and due to small period. Due to larger amplitude and shorter switching time, all the digital signals will contain high-frequency elements that are independent to switching frequency. In analog sections, the voltage is usually less than 1μV from radio tuning loop to radio equipment receiver. Therefore, difference between radio tuning loop and RF signals can reach a very high value. As a result, the performance of radio equipment will be effected.

2. Interference due to Power Supply:

RF circuits are highly sensitive to noise due to very low voltages from radio tuning loop to radio equipment receiver. Voltage glitchs may arise on power lines due to sudden current absorbents in the circuits viz. microcontrollers. If proper decoupling techniques are not applied, voltage glitches at RF circuit power port, which may cause serious failure of the circuit.

3. Improper GROUND:

Poor placement / improper Ground on RF circuit leads to erroneous results. In contrast, most digital circuit functions are capable to work despite of improper grounding. Where as for RF circuitis, a short ground line will play an equivalent role as inductor affecting the operation of the operation of RF circuit intended for some other purpose.

4. Radiated Interference by Antenna on Other Analog Circuits:

An RF PCB consists of several analog circuits like analog-digital converter (ADC) or digital-analog converter (DAC). The high-frequency signals transmitted by RF transmitter arrive at input terminal of ADC because any circuit line will transmit or receive RF signals like antenna does. If input terminal of ADC is inappropriately processed, RF signals will possibly become self-excited within ADC, which then arouses ADC deviation.