Question
Which intermodulation products are closest to the original signal frequencies?
Answer Options
- A) Second harmonics
- B) Even-order
- C) Odd-order
- D) Intercept point
Correct Answer: C
Explanation
Intermodulation (IMD) occurs when two or more signals mix in a non-linear circuit (such as an overdriven amplifier or a receiver mixer), creating new, spurious frequencies. These spurious frequencies are referred to by their order, which is the sum of the coefficients of the original signals.
IMD products generated from odd-order distortion (e.g., third-order: 2F_1 - F_2 and 2F_2 - F_1) are the most problematic because they fall close to the original signal frequencies. Because they are spectrally close, they are difficult to filter out and often cause interference and noise in the desired channel. In contrast, even-order products (like F_1 + F_2) are usually far from the desired signal.
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