Planar near field measurement using photonic sensor for microstrip array antenna at X band - comparison among planar near field measurements using photonic sensor and open-ended waveguide, and far field measurement

摘要

We report the measurement of antenna patterns at 9.41 GHz, of a microstrip array antenna using a photonic sensor as a probe for planar near field scanning equipment. Because the antenna size of the photonic sensor is less than 0.1 wavelenght, the antenna can be considered as a linearly-polarized electric infinitesimal antenna. Moreover the sensor consists of dielectric materials except metals used for the antenna and a mirror. Therefore, the coupling between an antenna under test and the sensor is negligible. This means that we can measure the electric field close (about 0.3 wavelength) to the aperture of the antenna under test. To verify the characteristics, we have measured the antenna patterns of the same antenna using the conventional open-ended waveguide as a probe of the planar near field method and using the far-field method, and compared the measured results using the three methods. Because the measured results agree within 1 dB in the main beam of the antenna, we have confirmed that the photonic sensor can be treated as a linearly-polarized electric infinitesimal antenna.