  Spread-spectrum signals are increasingly adopted in fields including
communications, testing of electronic systems, Electro-Magnetic Compatibility
(EMC) enhancement, ultrasonic non-destructive testing. This paper considers the
synthesis of constant-envelope band-pass wave-forms with preassigned spectra
via an FM technique using only a limited number of frequencies. In particular,
an optimization-based approach for the selection of appropriate modulation
parameters and statistical features of the modulating waveform is proposed. By
example, it is shown that the design problem generally admits multiple local
optima, but can still be managed with relative ease since the local optima can
typically be scanned by changing the initial setting of a single parameter.
