Codebook Requirements for Estimating Multi-Antenna SAR in Linear Time

Specific Absorption Rate (SAR) is an exposure safety measure used by regulatory agencies for determining the compliance of portable wireless transmitting devices. It has been shown that compliance of devices with multiple transmitter chains operating at a single frequency can be determined with measurement time that is linear in the number of antennas per probe location. One known example relies on a specific set of excitation signals that turns on one or two antennas at a time. We provide a general requirement on the excitation signals such that a wide class of signals can be used for SAR compliance in linear time. This general requirement allows a subset of the signal "codebook" of the device to be considered as the excitation signals for SAR compliance. We give an example where the excitation signals turn all of the antennas on simultaneously and show its advantages over the existing method.