MIMO Antenna Measurement

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The main issue in measuring the performance of small antennas is the influence of the coaxial cables feeding the device under test. The coax not only impacts the Far Field patterns by scattering of field incident on the cable, but if the coax is not decoupled properly, it becomes a large contributor to the total radiation measurements. Optical Zonu’s OZ100 and OZ101 Series, RF over Fiber Optics Product Line are miniature with an extremely low profile, measuring only 18 x 50 x 7.5 mm.

The extremely small size, low power consumption and high performance features of the RFoF Modules, combine to create a compelling argument for the uses of RF over Fiber Optics Modules in antenna radiation pattern measurements.

Although the idea of using optical links is not new for RF signals, almost all of the RFoF developments in the Antenna measurement area are either too big, too short ranged, or simply not suitable for use in anechoic chambers. The OZ100 series is specifically designed to fit into a very small space and is optimized for low power consumption (runs on a small battery), thus imitating typical mobile phone handset electronics. It can be used for anechoic chamber measurements, but is designed for long range applications as well.

Optical Zonu’s Fiber Optic Links enable the measurement of the radiation pattern of small antennas without any coaxial cable interference effects. The product family was designed to enable the testing of hand‐held cellular telephones and emerging LTE (employing Antenna Diversity) devices, operating from the low voltage battery supply of the phone itself (down to +3.7 Volts).

Experimental results have demonstrated that the use of legacy RF coaxial cable strongly disturbs the antenna gain and radiation patterns for both polarization components. With very simple integration at low cost, our OZ100/101 Series Links can characterize radiation patterns of both narrow and UWB compact antennas. Studies which compared both measured and simulated results, demonstrated excellent agreement (±1 dB) for co‐polarization in the different cut‐planes. At very low power level measurements, and at high frequencies, standard RFoF Products in the market today are considered too big to be used because they affect the antenna radiation pattern. It is “best practice” to use miniaturized optoelectronic components, whose size does not materially impact the outline of the product under test.