This thesis discusses spherical near-field measurements implemented by a circular waveguide probe which has much shorter length and wider operating range than those proposed similar circular probes. A brief introduction of spherical near-field measurement techniques is provided first. We also introduce the well-known conclusion that utilizing first-order probes simplifies the measurements and associated near-field to far-field transformation. Accordingly, a relatively short circular waveguide probe antenna is designed and fabricated. Detailed fields of this probe are analyzed to demonstrate that it is still a first-order probe even though the length is short. Furthermore, it radiates only first-order fields over a wide frequency range, indicating it is applicable as a near-field measurement probe in this range. This wide operating range is because of the use of symmetry to control unwanted modes. We also exploit the concept that a first-order probe can be realized with two first-order modes: TE11 and TM11. Probe calibration results also evidence these findings. This circular waveguide probe is then utilized to examine a base station antenna in its near-field range. The transformed far-field patterns validate the practicability of our probe.The TM11 mode is not harmful because it is first-order in I, as will be discussed below. Table 2.1 shows some modes of a 6-inch diameter circular waveguide in the order of their cutoff frequencies. It is evident that if this waveguide is operated anbsp;...
|Title||:||Wide Operating Range for a Circular Waveguide Probe in Spherical Near-field Measurements|
|Publisher||:||ProQuest - 2009|