In intermodulation terminology, which orders correspond to the sum and difference components from two tones?

In intermodulation terminology, which orders correspond to the sum and difference components from two tones?

• A. 1st and 2nd
• B. 3rd and 5th
• C. 7th and 9th
• D. 11th and 13th

Answer: (B)

When two tones mix in a nonlinear device, new frequencies appear that are combinations of the two input frequencies. The term “order” refers to how many input-tone components are involved in forming a given intermodulation product. The frequencies created by mixing both tones—for example the sum f1 + f2 and the difference |f1 − f2|—come from cross terms that involve both f1 and f2. In the usual two-tone intermodulation framework, the lowest cross terms that involve both tones occur at odd orders, with the first such cross terms appearing at the third order and then again at the fifth order. That’s why the sum and difference components are associated with the 3rd- and 5th-order intermodulation products. Higher odd orders (7th, 9th, etc.) also produce cross terms, but the fundamental sum/difference content is tied to those 3rd and 5th orders.

When two tones mix in a nonlinear device, new frequencies appear that are combinations of the two input frequencies. The term “order” refers to how many input-tone components are involved in forming a given intermodulation product. The frequencies created by mixing both tones—for example the sum f1 + f2 and the difference |f1 − f2|—come from cross terms that involve both f1 and f2. In the usual two-tone intermodulation framework, the lowest cross terms that involve both tones occur at odd orders, with the first such cross terms appearing at the third order and then again at the fifth order. That’s why the sum and difference components are associated with the 3rd- and 5th-order intermodulation products. Higher odd orders (7th, 9th, etc.) also produce cross terms, but the fundamental sum/difference content is tied to those 3rd and 5th orders.