Question
Why are odd-order intermodulation products, created within a receiver, of particular interest compared to other products?
Answer Options
- A) Odd-order products of two signals in the band being received are also likely to be within the band
- B) Odd-order products are more likely to overload the IF filters
- C) Odd-order products are an indication of poor image rejection
- D) Odd-order intermodulation produces three products for every input signal within the band of interest
Correct Answer: A
Explanation
Intermodulation (IMD) products are generated at various orders (2F_1, 3F_1, F_1 \pm F_2, 2F_1 \pm F_2, etc.). While all are unwanted, the odd-order products (third, fifth, seventh, etc.) are the most problematic because of where they fall in the frequency spectrum relative to the desired signal.
Odd-order products, such as 2F_1 - F_2 and 2F_2 - F_1 (third-order), have a unique and troublesome property: if the two original signals (F_1 and F_2) are relatively close in frequency within the passband, the resulting odd-order IMD product will also fall close to or within the band being received. Since these products cannot be easily filtered out, they cause direct and persistent interference to the desired signal.
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