Improved Beamforming in 3D Space Applied to Realistic Planar Antenna Arrays by Using the Embedded Element Patterns

In this paper we compare radiation patterns and mutual coupling in finite and infinite square lattice arrays of dielectric resonator antenna (DRA) elements. The array elements are cavity backed, slot fed cylindrical DRAs that utilizes the HE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11δ</sub> mode. It is observed that the degree of the mutual coupling for non-edge elements is very close to the mutual coupling between the corresponding elements in the infinite array. However, a large difference is observed in the mutual coupling between the center element and the two corner elements in the finite array with respect to the corresponding elements in the infinite array. The coupling is strongest in the E-plane and it is shown how it changes the embedded element patterns in the array.

A novel embedded element pattern decomposition method is proposed to synthesize conformal phased antenna arrays. This method decomposes the embedded element patterns as a product of a characteristic matrix and a Vandermonde structured matrix. This Vandermonde matrix is composed of modes in the modal space at the sampling angles. Because the fast Fourier transform (FFT) algorithm can be used in the Vandermonde structure, the computational cost can be reduced tremendously. In addition to its computational efficiency, the proposed method is also applicable to the synthesis of a pattern with any mainlobe direction and optimized polarization. A modified particle swarm optimization (PSO) method is applied to optimize the weights of the modes. This method is demonstrated through a simulation of a 9-element conformal array. The results show the advantages of the new method in achieving a low peak side lobe, accurate mainlobe scanning, and low cross-polarization.

We propose a methodology to compensate the effect of mutual coupling in planar antenna array arrangements using a novel electromagnetic machine learning (ML) technique. The electromagnetic behavior of the array elements and their mutual coupling interactions are described via the antenna current Green's function (ACGF). A ML artificial neural network (ANN) procedure is then applied and combined with the ACGF to optimize array ports and mitigate for mutual coupling effects.

A new experimental way of testing MIMO systems is proposed by means of two reverberation chambers coupled through a waveguide. The modularity of this experimental setup is emphasized and some theoretical and experimental results are presented. The effect of the waveguide on the propagation channel is pointed out. I. INTRODUCTION MIMO systems have gained a lot of attention since they promise an increase of the capacity with a very high spectral efficiency. The knowledge of the propagation mechanisms is crucial in order to define reliable, precise and adaptive channel models. Theoretical researches have been carried out in order to obtain such a channel model (1). However, a model must be supported by measurements campaigns. Those measurements are highly environment dependent and it is difficult to reproduce or to control the environment. In this paper, a new measurement system is proposed which allows to control and to reproduce different specific environments. This measurement testbed is composed of two reverberation chambers coupled through a waveguide. First, the theoretical modeling of the chambers is presented. To model accurately the channel we have to deepen the understanding of the propagation in the waveguide. The basics of waveguide modal analysis are presented. Then, the power weight of each mode is computed. From this result, we are able to understand intu- itively the propagation mechanism in waveguide like systems and the notion of independent paths with different amount of power. To fulfill the understanding of the waveguide, the radiation of each mode in the receiving chamber is deduced. Some numerical results are provided. A channel model is then presented in order to take into account all the parameters of our system. Measurement results are finally provided, pointing out the ability to obtain different propagation conditions. A discussion about the benefits and the drawbacks of this system concludes the paper. II. THE COUPLED REVERBERATION CHAMBERS The proposed testbed is composed of two mode stirred reverberation chambers (MSRC) of about 16m 3 each. MSRC have first been developed for susceptibility testing of electronic devices. Since they allow to produce a dense and isotropic multipath environment, they are now also used for testing antenna characteristics (such as correlation between antennas, mutual coupling or embedded element pattern) and wireless communications systems (2), (3). By means of the movement of the mechanical stirrer, the boundary conditions are changed and a new distribution of the propagating plane waves in the chamber is obtained. The originality in this paper is the use of two chambers to model separate environments for the emitter and the receiver. Those chambers are coupled through a waveguide (cf. Fig. 1) whose transverse dimensions can be changed in order to modify the channel characteristics between the emitter and the receiver. The waveguide allows to obtain independent propagation paths, and to control the degrees of freedom of the channel.

This paper deals with the calibration of the analogue chains of a Square Kilometre Array (SKA) phased aperture array station, using embedded element patterns (one per antenna in the array, thus accounting for the full effects of mutual coupling) or average element patterns to generate model visibilities. The array is composed of 256 log-periodic dipole array antennas. A simulator capable of generating such per-baseline model visibility correlation matrices was implemented, which allowed for a direct comparison of calibration results using Statistically Efficient and Fast Calibration (StEFCal) with both pattern types. Calibrating the array with StEFCal using simulator-generated model visibilities was successful and thus constitutes a possible routine for calibration of an SKA phase aperture array station. In addition, results indicate that there was no significant advantage in calibrating with embedded element patterns, with StEFCal successfully retrieving similar per-element coefficients with model visibilities generated with either pattern type. This can be of significant importance for mitigating computational costs for calibration, particularly for the consideration of real-time calibration strategies. Data from the Aperture Array Verification System 1 prototype station in Western Australia was used for demonstration purposes.

This paper deals with the synthesis of monopulse antenna patterns, sum and difference ones, for planar phased array antennas with an elliptical aperture boundary featuring unequal ultra-low peak sidelobe levels (PSLLs) for the two principal planes of its far field. The used synthesis method is the iterative Fourier transform (IFT) approach. The elliptical planar phased array antenna involved in this synthesis contains 3656 open-ended waveguide radiating elements arranged in a triangular element grid and has an aperture width and height of 50λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> and 25λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> , respectively, where λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the wavelength at X-band center frequency 1.0f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> . The simulated monopulse pattern results will be compared with those of a 4680-element rectangular planar phased array antenna having the same width, height, radiator type and triangular grid as the elliptical array antenna. The monopulse patterns of the rectangular array antenna meet the same unequal ultra-low PSLL requirements as those of the elliptical array antenna. It will be shown that the elliptical array antenna with a slightly enlarged aperture containing 4170 elements features on receive comparable or even better far-field performance characteristics as that of the rectangular array antenna. All reported far-field pattern simulations take mutual coupling between the array elements into account.

A research about design and realization of dual planar bow-tie dipole array antenna at 2.4 GHz will be presented for Wifi Outdoor BTS applications. The proposed antenna should have wide bandwidth, high gain, and ± 45° dual polarization. From the simulation and measurement results of realized antenna we can concluded that our proposed antenna has met the desired specifications; antenna reflection coefficient value <; -10 dB, mutual coupling <; -20 dB, antenna bandwidth exceeds 1.2 GHz, antenna gain reaches 16.62 dBi. Moreover, beside for Wifi Outdoor BTS applications, this implemented antenna actually can be used for another wireless systems simultaneously for GSM 1800 MHz, 3G 2100 Mz, and LTE/Wimax 2300/2500 MHz.

The future terahertz (THz) communication is a promising solution to the high-data-rate and short-range communication due to its broad available bandwidth. However, the high propagation path loss and the limited output power of the amplifier require highly directive antennas with high antenna gain in order to realize a reasonable signal-to-noise ratio (SNR). An angle of arrival (AoA) estimation is necessary to adjust the main lobe direction of the antenna. A major challenge of the AoA estimation is the compromise between accuracy and time consumption due to the big number of main lobe directions. This paper proposes a novel efficient AoA algorithm, which utilizes the fact that the power angular spectra (PAS) of different frequencies are highly correlated and the THz communication devices are equipped with radio frequency (RF) frontends of lower frequency. By means of a rough and quick estimation at the lower frequency, the range of the true AoA can be confined significantly and the precise estimation can be carried out efficiently. To begin with, an antenna model with discrete main lobe directions is proposed and the relationship between antenna gain, half power beam width (HPBW) and number of main lobe directions is analyzed. The PAS correlation is then validated with channel sounding measurement. The two-step AoA estimation algorithm is derived, formulated and finally validated with hardware demonstration.

The full models of meander spoof surface plasmon (SSP) cells are presented for the design of slow wave transmission lines (SW-TLs) with the minimum loss and controllable mutual coupling (MC). In addition to the modeling of dispersion curve and characteristic impedance, the proposed circuit model based on geometrical parameters calculates the ohmic loss of the SW-TLs composed of meander SSP cells. Being verified with the full-wave analysis, the model provides a clear understanding of the mechanism of the SSP-based SW-TLs and a new way to design with other circuits at a system level. The model is applied to minimize the ohmic loss in the meander SW-TLs up to at least 10 dB per 10 wavelengths lower than that of conventional TLs. The MC of the SW-TLs can be controlled either up to three orders of magnitude lower or one order of magnitude higher than that of the conventional TLs. This paper proposes methods to decrease the ohmic loss of single-layered meander SW-TLs and also controls MC between them. The proposed methods open new avenues for complex and compact circuit designs.

This paper presents a high-directivity planar microstrip antenna array operating at microwave frequency. The antenna array consists of 48 sub-arrays, and each sub-array comprises 4 elements. The radiation mechanism of the single element, by exciting the first higher order mode (EH/sub 1/ mode), can be estimated by the full-wave analysis. Through appropriately arranging and feeding these 192 single elements, the radiated characteristic of the antenna performs narrow radiation beamwidth both in azimuth (AZ) and elevation (EL), thus achieving high directivity. The planar microstrip antenna array prototype is built and tested at 38GHz by traditional printed circuit board (PCB) fabricating process. The measurement result indicates the high directivity of 22.3dB and the 3-dB beamwidth of 8/spl deg//12/spl deg/ (AZ/EL) at the elevated angle 30.2/spl deg/ away from the broadside direction.

This paper present further validations of a Method of Moment (MoM) based technique dedicated to fast simulation of SKA-low arrays. In particular, the embedded element patterns and array patterns are studied. The patterns obtained using this technique are compared with those using the commercial software CST. The comparison shows the importance of the mutual coupling in modeling these patterns. Further validation is demonstrated by an example of nulling in the presence of mutual coupling.

In this work we present an approach for the prediction of far-field pattern characteristics of phased array fed reflector antennas by modeling only a small part of the array. In this approach, the simulated EEPs of the FPA are modeled as the phase-shifted versions of the simulated embedded element pattern (EEP) of the central element, and thereafter combined with the optimum weighting coefficients in order to find the total pattern of the feed. Although, the EEPs of dense array antennas are generally not identical (due to the array antenna mutual coupling and edge truncation effects), for typical FPA excitation scenarios, where the array edge elements have relatively low weights to produce the desired illumination of the reflector, this simplified approach has been found sufficiently accurate.

Planar Beam-forming Antenna Array for 60-GHz Broadband Communication

This letter presents a planar wideband linear antenna array to cover multiple wireless standards. The array consists of four microstripline-fed open-ended quarter-wavelength slot antenna elements. By feeding the antenna properly, a fundamental radiating antenna mode can be excited over a wide frequency range. The antenna array is simulated in terms of surface current distributions and S-parameters. Simulated results are compared to the manufactured prototype antenna array. Measured results show the -10-dB impedance bandwidth is from 2.55 to 6.1 GHz, corresponding to 83% relative impedance bandwidth, while mutual coupling is less than -16.6 dB within the aforementioned impedance bandwidth. The simulated -10-dB bandwidth is from 2.0 to 6.0 GHz. Measured radiation patterns are presented at 2.4, 3.5, and 5.2 GHz with 4.6, 7.0, and 7.9 dBi maximum gain in boresight direction, respectively. The measured radiation patterns and grating lobe levels correlate well with the theory and are 10-15 dB below the main lobe depending on the studied frequency.

In this paper, a planar beam-forming antenna array is proposed by using the orthogonal radiation modes of coupled antenna system. Mode-decomposition allows channel capacity to be fully exploited while the mutual coupling between closely spaced antennas is significantly reduced. For low profile design, a four-element patch antenna array module implemented in a double-layer substrate is adopted. For experimental demonstration, the simulated and measured results of a 2.4 GHz antenna array fabricated on low-cost printed circuit board are given.