Combination of time and spatial filtering to improve echo reduction in antenna measurements

Abstract

Abstract-Different research groups have been working during the last years in different echo reduction techniques applied to antenna measurements, based on spatial, modal or time filtering. Some applications where these methods are usually employed are: outdoor systems, for HF or VHF frequency systems or for small measurement systems where the anechoic material is only placed in front of the AUT. This paper analyzes the measurements of a dipole antenna (SD1900) using a StarLab system and the application of the different algorithms. It is observed that each of the algorithms is better for different situations, depending for instance on the angular value of the pattern. Finally, a combination of different methods in a smart way improve the results of the post processing with respect each independent method.

Analysis of time filtering techniques for echo reduction in antenna measurements

“…First, the samples measured at different frequencies are transformed to the time domain, via an inverse FFT. The echoes are then effectively filtered out in the time domain, and finally a new FFT is applied to reconstruct the field [21][22][23][24][25]. The time filtering principle is shown in Fig.…”

Comparison of echo reduction techniques for one-single cut antenna measurements

“…The concept about this method has been explained in the introduction of this paper. In [24], this technique has been applied to the NF of the antenna. In this paper is instead applied on the FF of the AUT, where direct ray and interferences can still clearly be detected because the transformation from NF to FF is just a linear operation, which does not impact the effectiveness of this filtering method.…”

“…The algorithms can in fact be applied to specific cuts where the user could detect problems or to single cuts NF measurements. In fact, this algorithm can be combined with the single cut NF/FF transformation software presented in previous work [24].…”

Time filtering techniques for echo reduction in antenna measurements

“…There are different methods for performing this filtering, and, in this paper, the authors have used the wellknown Fourier Transform [1] and the Matrix Pencil methods [2][3] for the cancelation of the echoes in antenna tests. FFT method has been used in [4] with other modal filtering methods to improve the results of antenna measurements. However, the objective of the paper is to compare both methods and to analyze the limitations and advantages of each technique for antenna measurements.…”