Motionless, Single-Snapshot Far-field Pattern and EIRP Measurement Method in a Compact Hybrid Chamber Employing a Sampling Array

Artikel i vetenskaplig tidskrift, 2026

A method for motionless far-field radiation pattern and Equivalent Isotropic Radiated Power (EIRP) measurement of black-box transmitters in a compact antenna chamber is presented. Motionless operation is particularly valuable for rapid production testing of complex devices under test (DUTs) such as beamsteering array antennas. The chamber is a metal overmoded rectangular waveguide terminated by a sampling chamber array antenna (CAA) at one end and an absorbing wall at the other end, where the DUT test zone is located. Using reciprocity and power-wave formalism, we derive a linear relation between the coherently sampled CAA receive signals and the DUT EIRP pattern, enabling pattern reconstruction from a single-snapshot without mechanical rotation. A one-time calibration procedure, based on the measured embedded element fields (EEFs) of the CAA and an optimal beamforming algorithm, yields CAA weight vectors that, in the transmit situation, synthesize a rich set of plane waves in the test zone, thereby defining a high-resolution sampling grid of the pattern and EIRP normalization. A dedicated probe-correction technique is developed to ensure accurate EEF estimation despite the strongly multi-scattering environment. Full-wave simulations in the 5G NR FR1 range and experiments in a 900 MHz prototype chamber validate the method for representative linear and circular polarized (LP/CP) DUT cases. The measured EIRP errors at peaks are 0.2–0.4 dB for the three experimental DUTs. The maximum pointwise normalized pattern errors within ±60° are between -17 dB and -25 dB, with the largest value associated with a localized feature in the anechoic chamber reference for the low-gain CP spiral DUT. In the high-gain simulated cases, the errors decrease below -30 dB.