Dual Polarization Probe
Broadband dual-polarization probe has a wide range of applications. This page introduces a kind of application of broadband dual-polarization probe in the mini far-field measurement of electric small size. As shown in Figure 1, the radiation field of the antenna is divided into the Rayleigh zone, Fresnel zone, and Fraunhofer zone, which can be divided into near-field and far-field measurement, and the measurement distance L>D²/2λ
P 1 Schematic diagram of the antenna radiation field
- The product provides a wide-band dual-polarization probe with a frequency of 0.4-6GHz, and at the same time provides an algorithm program, which is used to achieve the cross-polarization of the whole frequency band > 30dB. When applied to a mini far-field, it can meet the far-field test conditions and directly obtain accurate test results by using a correction algorithm.
- Antenna measurement has harsh requirements on the test site, as shown in the following figure. When testing the distance L<2D²/λ, it is necessary to adopt near-field measurement, such as the multi-probe near-field measurement system which has fast testing speed but high system cost.
- The far-field measurement system can be used when testing the distance L<2D²/λ,. The size of the antenna to be DUT determines the size of the darkroom to be built. For the length of the antenna in sub6G, the cost and occupied area of the darkroom will be expensive. For the small-size antenna in sub6G, a small darkroom is used for far-field measurement, assuming that the test distance L=1m (this assumption will greatly facilitate the construction of the darkroom), as shown in Figure 2, the size of the DUT is calculated to be about 0.15m-0.6m, and there are various antennas within this size range.
P 2 L=1m Antenna size satisfying far-field conditions
- When the test distance is solved, it is necessary to choose a broadband horn antenna with a small enough size, at least D<150mm smaller than the antenna to be tested, and the cross-polarization is good enough. We refer to Broad-band dual-ridged horn OBH460 and the Open boundary wide-band quad-ridged horn ODPA-460, as shown in Table 1. The size exceeds 0.5m, far exceeding the requirements, and the Probe scheme with RFecho can meet the requirements. Here is the algorithm calibration scheme of the probe.
OBH460 ODPA-460 Rfecho Probe Polarization Single linear Dual linear Dual linear Cross-polar >30dB >30dB >30dB Dimensions (H x W x L) [mm] 540 x 292.3 x 435 527 x 527 x 462 <100*120*120
- It is impossible for a small-sized broadband dual-polarization probe to achieve good cross-polarization performance in the whole frequency band only at the hardware level, but scientists have done a lot of research on the calibration technology of the probe, which can effectively calibrate the cross-polarization of the small-sized broadband dual-polarization probe below 30dB, such as multi-probe near-field test system. The following is a brief introduction to this calibration method.
P 3 Probe-modified scattering matrix model
180 probes only
180 probes corrected by this algorithm
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