多探头技术

PROBE ARRAY CONCEPTS FOR FAST TESTING OF LARGE RADIATING STRUCTURES
Ph. GARREAU, L. DUCHESNE, A. GANDOIS, L. FOGED, P.O. IVERSEN SATIMO SA, 22 Avenue de la Baltique, Courtaboeuf , France
2.0 Stargate Technology
The Stargate systems that are now installed worldwide consist of individual A-MST probes and a passive combining network [1]. Such arrays have been installed covering frequencies from 70MHz to 18GHz. A conceptual block diagram of such a system is shown in Figure 1.
range, enabling the use of standard low cost electronic components. The low frequency modulator is synchronized with the receiver data acquisition to provide phase and amplitude measurements at each probe in fractions of a millisecond.. The major advantage of the Stargate technology over mechanically scanned systems is the drastic improvement in measurement speed. For tests with up to few tens of frequencies, the test time is generally reduced proportionally to the number of elements in the probe array. As an example, a recently installed vehicle based antenna test system is able to do multi-frequency spherical near-field measurements with 1° elevation and azimuth resolution in just over 5 minutes. Comparable systems based on single probe mechanical scanning would require at least four hours for completing the same test.
AUT
A-MST Probe Array RF Power easuring antenna radiation patterns require sampling the electromagnetic fields on a surface or a path around the antenna under test (AUT). Traditionally, such measurements involve a rotation of an AUT in front of a test probe, and/or or the movement of a probe antenna around the AUT. Single probe systems, rely on mechanical movements to perform this field sampling, while probe arrays replace some or all of the mechanical movements with electronic scanning techniques. Although, probe arrays can certainly be used for testing
LF Modulator Receiver
Figure 1: Conceptual Block Diagram of A-MST Probe Array near-field antenna measurement system. Satimo’s A-MST probes are dual polarized and operate over more than a decade of bandwidth. The low frequency modulator operates in the kHz frequency
small antennas directly in the far-field, they offer the biggest advantages for near-field measurements where a large number of spatial samples are required. Near-field measurements require sampling the field over a surface partially or fully enclosing the AUT. For electrically large structures, the required number of spatial sampling points can become exceedingly large and the associated measurement time a real obstacle. Probe arrays offer a way to significantly improve the overall measurement time while maintaining the measurement accuracy.
ABSTRACT Satimo’s STARGATE probe array systems are now well established as an efficient tool for testing radiated performances of wireless devices and antennas. Since 1998, about forty STARGATE measurement systems have been successfully installed worldwide. Recently, a range of new applications have also demonstrated the suitability of probe arrays for large radiating structures and directive antennas. These new generation of measurement set-ups present innovative aspects regarding their rapidity, dynamic range, and accuracy. This paper will describe several novel antenna testing concepts based on probe arrays that cover automotive, aerospace, and military applications and a wide range of frequencies. The basic difference between traditional approaches using single probe and the STARGATE approach using an array of probes will be explained along with probe array calibration procedures. An error analysis budget using the conventional NIST error terms will be presented including the specific terms related to the use of probe arrays. Also a discussion will be made on some of the key technical challenges to making large probe arrays including such issues as dynamic range, mechanical tolerances, and data truncation effects. Keywords: Antenna Measurements, Probe Arrays, Spherical Near-Field, Aeronautical, Automotive.
3.0 Measurement Accuracy
Early implementations of probe arrays provided limited dynamic range and suffered from other restrictions that reduced their accuracy for antenna measurements. These limitations were largely overcome by the introduction of Satimo’s Stargate system. For each specific application a detailed uncertainty budget is generally developed. An example of an uncertainty budget developed following the general procedure in [2] and [3] for antenna radiation pattern is shown in Table 1. This example is specific to an automotive test system and is shown to illustrate which terms are big uncertainty contributors. In spherical nearfield antenna measurement systems employing probe arrays for testing large structures, the following terms have been observed to dominate the uncertainty budgets for testing low to medium gain antennas: 1. 2. 3. Room Scattering Truncation Effects Gain of calibrated substitution antenna