RF input to a mixer is 200 MHz and the local oscillator frequency is 150 MHz. What output would you expect to see at the IF output prior to any filtering?
ā¢ Mixer operation in a superheterodyne receiver ā a mixer produces sum and difference frequencies of the RF (radio frequency) and LO (local oscillator) signals ā¢ Intermediate Frequency (IF) ā usually the result of RF Ā± LO before any filtering selects just one product ā¢ Know that mixers are nonlinear devices that generate multiple products, not just one
ā¢ What two main frequencies are produced when a 200 MHz RF signal is mixed with a 150 MHz local oscillator signal? Think in terms of sum and difference. ā¢ Besides the main sum and difference products, what other frequencies are already present at the mixer ports (like the original RF and LO) before filtering? ā¢ Which answer choice correctly lists all the signals you would reasonably expect at the mixer output prior to any IF filtering?
ā¢ Calculate sum = RF + LO and difference = RF ā LO clearly and write both values down. ā¢ Remember that before filtering, the original RF and LO signals can also appear at the mixer output along with the sum and difference products. ā¢ Check which options include both mixing products (sum and difference) and consider whether the original signals may also still be present before filtering.
No comments yet
Be the first to share your thoughts!