General description of multiple-modulation effects and sideband production in magnetic resonance
A theory is presented for the sideband structure produced by a general multiple-modulation scheme with arbitrary combination of p-tuple field modulation, q-tuple frequency modulation, and r-tuple amplitude modulation for integral p, q, and r. A general formula describing the multiple-modulation effects is analytically derived using a density matrix formalism under the assumption of negligible saturation; an equivalent result is obtained from the phenomenological Bloch equation. The general formula reveals that field and frequency modulations are equivalent for the sideband production, even in the presence of amplitude modulation. Two particular cases, viz., r-tuple amplitude modulation and double field modulation are dealt with to show the validity and applicability of the general formula.