This paper investigates the linearity of active devices and amplifiers
that have modulated input signals, We describe an implementation of a
mathematical technique for calculating spectral regrowth due to the n
onlinear amplification of modulated signals typically used in wireless
communication systems, This technique only requires knowledge of the
single-tone gain and phase data as a function of input power and can b
e applied to any modulated signal given a) the device or amplifier cha
racteristics do not change significantly over the bandwidth of the inp
ut signal and b) the modulation frequencies are much less than the car
rier frequency, Verification of the mathematical technique is presente
d using examples of measured and calculated spectra for pi/4-different
ial quadrature phase shift keying (DQPSK) personal handy phone system
(PHS) and code division multiple access (CDMA) Offset-QPSK personal co
mmunication system (PCS) modulation schemes, This calculation techniqu
e is essential in determining fundamental tradeoffs between device per
formance (linearity, output power, gain, and power-added efficiency) a
nd device bias conditions and load impedance.