Gain antenna measurement using single cut near field measurements

Some antennas require rapid validation at a reduced measurement distance while maintaining sufficient accuracy in the determination of pertinent antenna parameters such as gain. In particular, for cellular base station antennas in production phase the measurement time can be a limitation. In these cases, a rapid check of the radiation performance in the two main planes is sufficient. Other examples are phase arrays with high degree of steering that would require considerable measurement time for characterizing all steering positions. This paper presents a near-field antenna test procedure providing single or double main plane patterns including the gain. The procedure is applicable to antennas, with separable excitation in the two main planes. The test set-up is based on an azimuth positioner and near to far-field transformation based on expansion in cylindrical modes. The paper shows results for gain measurements. Near to far-field transformation is performed using the cylindrical modes expansion assuming a zero-height cylinder. This allows the use of a FFT in the calculation of the far field pattern including probe correction. In the case of gain, the near to far-field transformation factor is calculated for bore sight direction, taking advantage of the separable excitation properties of the antenna. This factor is used in the gain calculation by comparison technique

Measurement facility comparisons within the european antenna centre of excellence

This paper gives an overview of the activities performed under the Antenna Measurement Techniques and Facility Sharing activity of the Antenna Centre of Excellence (ACE) within the EU 6th framework research program. In particular, the activities involving antenna measurement facility comparisons are discussed in detail. These activities are important instruments to verify the measurements accuracies for each range and investigate and evaluate possible improvements in measurement set-up and procedures

Facility comparison campaigns within Eurapp

An important activity within the past Antenna Centre of Excellence (ACE) network was dedicated to facility comparison campaigns as reported in. The activities spanned the frequency range from L-Ka band using different antennas (VAST12, SATIMO SH800 and SATIMO SH2000). The vast amount of data from different measurements institutions within Europe and US has been used to establish a reference pattern for each of the high accuracy reference antennas. The reference patterns and the data from the facility comparison activities are considered important instruments to verify the measurements accuracies for antenna measurement ranges as well as to investigate and evaluate possible improvements in measurement set-ups and procedures. This paper gives an overview of the ongoing activities in the frame of the EURAPP working group on antennas measurements and the first considerations on useful criteria for comparing and evaluating large amount of measured antenna data

EMC Measurement Setup Based on Near-Field Multiprobe System

Multiprobe spherical near-field measurement is a potent tool for fast and accurate characterization of electrical properties of antennas. The use of fast switching in one axis, an azimuth positioner, and a near- to far-field transformation allows a substantial time reduction in antenna measurements while maintaining high-quality results. On the other hand, conventional emissions EMC measurement systems are typically based on detecting the radiated spurious emissions by a device at different frequencies. The systems usually work in far-field (or quasi-far-field conditions), performing the measurements either at 3 or 10 meters. Measurements under these conditions take space and time. Moreover, the systems are not cost-effective for pre-compliance purposes where pre-testing of the device should provide valuable information and confidence about the DUT before performing a compliance test. This chapter analyzes the possibility of cost and space reduction for EMC systems based on multiprobe near-field measurement systems in combination with OTA (over the air measurements), reference-less systems, spherical near-field transformation, phase reconstruction, modal filtering, source reconstruction, and software-defined radio receivers

Time and spatial filtering for echo reduction in antenna measurements

During the last years, new algorithms, based on time filtering, spatial or modal filtering, have been designed for echo reduction techniques applied to antenna measurements. These algorithms have been used for different applications where the effect of the echoes is important, as far field system, VHF or UHF applications, automotive systems, small antennas, etc. The authors, in previous papers, have analysed the effect of different algorithms: time filtering (fft, non uniform dft or matrix pencial), modal filtering based on Spherical modes (MV-Echo) and spatial filtering based on Integral Equations (Insight) and holographic techniques (fft and dft) to cancel the effect of the reflections. This comparison has been applied to the measurements of a dipole antenna (SD1900) using a StarLab system. It is observed that each of the algorithms is better for different situations, depending on the source of the echo. For instance, time filtering techniques are good for reflections coming from different distances with respect the direct ray, but not so good for close reflections. In addition hey need a large frequency band to work properly. Spatial algorithms can correct the effect of positioners or other structures close to the antenna under test, but they are better for planar near field acquisitions and worse for classical single probe spherical near field where the antenna is rotated and probe is fixed (e.g. roll-over-azimuths systems). Moreover, they require extra information of the AUT geometry. This paper presents first a comparison of each algorithm and then, a combination of time and spatial techniques based on uniform or non-uniform DFT to take advantage of the benefits of each algorithm for different origins of the reflections

Measurement and simulation of reflector antenna

Well-established procedures are consolidated to determine the associated measurement uncertainty for a given antenna and measurements scenario [1-2]. Similar criteria for establishing uncertainties in numerical modelling of the same antenna are still to be established. In this paper, we investigate the achievable agreement between antenna measurement and simulation when external error sources are minimized. The test object, is a reflector fed by a wideband dual ridge horn (SR40-A and SH4000). The highly stable reference antenna has been selected to minimize uncertainty related to finite manufacturing and material parameter accuracy. Two frequencies, 10.7GHz and 18GHz have been selected for detailed investigation

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

This paper presents a comparison between two different echo reduction techniques applied to one-single cut antenna measurements. These techniques are based on modal filtering and time filtering. The first technique uses a postprocessing of the far field one-single cut so as to obtain a modal expansion of cylindrical modes and to cancel the effect of spurious signals. The second one is based on filtering echoes out in time domain by applying a Fourier Transform to get a signal in which some spurious contributions can be filtered out. Such techniques are applied on the single cut measurements of a wideband horn (MVI SH2000) performed in a semi-anechoic chamber and on the measurements of a dipole (MVI SD1900) performed in a MVG spherical multi-probe system (StarLab). A smart combination of both methods is also applied in order to improve the results of the post processing with respect each different method

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

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

A reflection suppression technique for far field antenna measurements

This paper presents a reflection suppression technique for far field antenna measurements. The technique is based on a source reconstruction over a surface greater than the antenna itself. To be able to perform the reflection construction the next steps are required: the complete far field antenna pattern is obtained through interpolation of the acquired cuts, the currents are obtained through a holographic technique, the field out of the antenna area is filtered, and the pattern is reconstructed. The algorithm is used with measurements in the LEHA-UPM antenna measurement facilities and in the outdoor far field facility of LIT INPE in Brazil

Analysis and suppression of reflections in far-field antenna measurement ranges

This paper presents the analysis of the reflections in two kind of spherical far field ranges: one if the classical acquisition where the AUT is rotated and the second one corresponds to the systems where the AUT is fixed and the antenna probe is rotated. In large far field systems this is not possible, but this can be used to the measurement of small antennas, for instance, with the SATIMO StarGate system. In both cases, it is assumed that only one frequency is acquired and the results should be improved cut by cut, in order not to lose the advantages or far field measurements. Finally, some practical results are studied using measurements of one antenna in the outdoor far field facility of LIT INPE in Brazil