Q:
What is the purpose of impedance matching in the MAX2112EVKIT? Is it okay not to use the RC in the design?
A:
The EV kit includes on-board matching circuitry at the MAX2112 RF input to convert the 50Ω source to the 75Ω RF input of the MAX2112. When the RFIN is not terminated properly, you will see signal reflection. This means that some of the signal is reflected back to its origin (in this case RFIN) instead of being carried to the end of the cable. This happens when the impedance is mismatched, hence why you need the impedance matching circuit to avoid that. The -6dB power loss is expected from the matching resistor network. Therefore, input power to the device must be adjusted to account for the -6dB power loss.