Effect of amplitude modulation of the CDMA IS-95 signal on SAR measurements

Miniature probes employed for specific absorption rate (SAR) measurements are typically calibrated using a sinusoidal waveform (SW), even though they may be employed to measure a wide variety of communication signals with complex waveforms. This paper shows that the compression produced by the nonlinear response of the probe versus SAR, due to its diode detector, may introduce a significant overestimation of the SAR produced by CDMA IS-95 waveforms when the diode detector operates well into the compression region. This finding is demonstrated theoretically, verified numerically and experimentally, and physically interpreted. The effect is typically small and may be neglected in many practical circumstances involving low-power RF energy emitters, such as mobile phones or two-way dispatch radios.