Question

The mixer of a TV receiver is a/an ________ port device.

• A. one
• B. two
• C. three
• D. four

Hint:

The mixer is the heart of the superheterodyne receiver, translating high-frequency incoming radio signals down to a lower, fixed Intermediate Frequency (IF) where they can be amplified and filtered much more efficiently.

Answer 1

The Correct Option is C

Step 1: Understanding Mixer Functionality:
In RF and microwave communication engineering, an RF mixer is a non-linear circuit used to perform frequency translation (heterodining).

Step 2: Identifying the Mixer Ports:
A standard mixer has exactly three functional connection terminals (ports):

• RF Port (Radio Frequency Input): Receives the high-frequency signal from the antenna or preamplifier.
• LO Port (Local Oscillator Input): Receives a steady, single-frequency signal generated by the local oscillator.
• IF Port (Intermediate Frequency Output): Outputs the sum and difference frequencies ($f_{IF} = |f_{RF} \pm f_{LO}|$), which are then filtered to isolate the difference frequency.

Step 3: Conclusion:
Since a mixer is fundamentally a three-port electronic device, option (C) is correct.