This paper reports measured results of a multielement antenna implementation, we constructed, that performs at 2.4 GHz ISM band. Particular emphasis was given to the scattering parameters and validation characterization of this antenna structure. The constructed multielement antenna that was studied in both azimuth and elevation planes consists of a number of printed dipoles with integrated baluns. Due to its multielement construction, the proposed antenna structure is suitable for applications that require multielements nature such as MIMO, channel sounder, and digital beamforming.
Requirements for wider bandwidth capabilities, higher bit rates, and better quality of services are crucial for wireless communication applications. Scientific and engineering community provides a number of novel techniques and methods to meet these requirements. These offer efficient improvements on the throughput of the wireless systems and are usually applied on compatible radiation structures, provided by single or multiple-element antenna architectures. These were further studied in terms of radiation efficiency and performance. Besides, the printed dipole antenna with integrated balun is an attractive type of radiation element that was studied and investigated in previous literature [
In addition, the printed dipole antenna with integrated balun and a reflector structure could support multielement antenna configurations because of the compactness and geometry of the whole implementation. The corresponding literature indicates that these multiple-element antenna configurations are mainly used in modern wireless communication applications such as MIMO (Multiple-Input Multiple-Output). These are used on both the transmitter and receiver ends, providing significant enhancement on the capacity of a wireless communication channel. Furthermore, these multiple-element antenna structures support channel sounding and digital beamforming applications along with appropriate signaling techniques.
In fact, these considerations are taken into account in design and implementation of the proposed antenna system. A number of identical printed dipoles and a reflector structure are designed and fabricated for single and multiple antenna elements applications. The geometrical parameters of them were modified to achieve better performance in the frequency range of 2.4 GHz. This radiation structure is arranged on a wooden base that provides rotation in azimuth and elevation planes and supports radiation pattern adjustments. From these, it seems that the proposed antenna system could be used in a measurement test-bed platform for channel estimation, digital beamforming, and MIMO applications in the frequency range of 2.4 GHz. Single or multiple-element antenna configurations with appropriate RF equipments could be used on transmitting and receiving ends on wireless communication applications. Furthermore, the proposed antenna system provides a number of antenna array topologies due to the reflector nature. This is also an attractive and versatile feature that provides further investigation on wireless channel performance.
For this fact, we are going to use the proposed antenna system as the main part of an RF test-bed platform for both transmitting and receiving purposes. The corresponding results are expected to improve the available channel characterization models and enhance studies on variations of the wireless channel capacity and the correlation of the corresponding subchannels. In addition, the proposed antenna structure provides spatial multiplexing and diversity techniques on MIMO wireless applications because it offers a number of antenna elements on transmitting and receiving ends that are connected with appropriate RF devices. These provide encoding and decoding the main data stream into substreams that are propagated in the wireless channel, simultaneously, providing significant enhancements on the bit rate and quality of service in the current application.
Moreover, using multiple radiation elements in any antenna array configuration on the proposed implementation, we could steer the main beam of the whole radiation structure in a desired direction of transmission or arrival. This corresponds to the digital beamforming method that requires appropriate signaling techniques. Also, a number of similar wireless communication applications are supported by the proposed single-element antenna structure. SISO (Single-Input Single-Output) systems that use only one transmitting and receiving antenna element are the most significant of them.
In any case, the proposed implementation provides a novelty antenna structure for single or multiple ports wireless applications. The compact, easy implemented, and low-cost printed dipole element improves its directivity and efficiency, using the reflector plate structure. The last provides multiple-elements antenna configurations with several geometries and is also arranged on the wooden base structure for better mechanical support, providing rotation on both elevation and azimuth planes, too.
These attractive features of the proposed antenna system are crucial for wireless applications and experimental channel measurements. The performance of the proposed single and multiple-element antenna is investigated by the corresponding simulated and experimental measurements.
In this paper, we propose an antenna implementation for wireless communication applications. In particular, Section
The construction of the proposed antenna system was carried out into three discrete steps. At first, the printed dipole with integrated balun was designed and implemented to meet the technical requirements for high-quality performance in the frequency range of 2.4 GHz. Figure
Printed dipole dimensions.
Geometry structure | Parameters—Values |
---|---|
Dipole strip | Length: |
Width: | |
Gap: | |
Microstrip balun | Length: |
Length: | |
Length: | |
Length: | |
Width: | |
Width: | |
Width: | |
Gap: | |
Via radius | |
Ground plane | Length: |
Width: |
Geometry of printed dipole.
Printed dipole antenna.
The same method was used to design and construct a group of identical printed dipoles with integrated baluns in form of a uniform linear antenna array (ULA). In this structure, the distance between the sequential elements approximates the half of the wavelength (
Uniform linear Antenna Array.
This antenna architecture was selected in order to support MIMO and digital beamforming applications. This uniform linear antenna array is a simple and compact structure that provides transmit and receive diversity in wireless applications. As the distance between the sequential radiation elements is equal to
In single or multiple-element case, the proposed antenna configuration is equipped with a reflector plate. The design and implementation of this structure are included in the second step of the antenna system implementation. In particular, the radiation elements are proposed to be arranged on the reflector plate, vertically. For this, a leaf of aluminum plate with 6 mm thickness was used to construct the reflector structure. Figure
Reflector structure.
The corresponding dimensions are
Printed dipole antenna on reflector plate.
Uniform Linear antenna array on reflector plate.
In Figures
On this investigation, we studied the single element and the four-element uniform linear antenna array performance. The form of the reflector structure provides forty available locations of the printed dipole element. The uniform linear antenna array could be adapted on one of the ten available locations, appropriately. In any case, two orientations are also provided. In particular, the dipole axis will be aligned to
To complete the implementation of the proposed antenna positioning structure, we design and construct a wooden base. The printed dipole elements and the reflector plate of the antenna system are adapted on a wooden base, appropriately. Figure
Geometry of wooden base.
Geometry | Value |
---|---|
70 mm | |
940 mm | |
50 mm | |
1810 mm |
Schematic of the proposed antenna configuration.
As mentioned above, the proposed wooden base architecture provides radiation pattern adjustments on both the elevation and azimuth planes. Using dry wood material for this antenna positioning structure, any degradation on the antenna performance is neglected. The relative permittivity of the dry wood material approximates the value of 2 as the RF signal frequency is close to 2.4 GHz. Moreover, this type of wood provides easy and compact implementation on the proposed positioning structure. The design and fabrication process took place on our laboratory, and the engineering staff is familiar with these constructions, using suitable tools and methods. From these considerations, it is obvious that the proposed wooden positioning structure offers rotation adjustments, mechanical stability, easy and low-cost implementation without eliminating the performance efficiency of the radiation elements.
These design considerations have been introduced to fabricate the proposed antenna configuration. Its performance is studied and investigated by a course of detail-simulated and experimental measurements. Next section includes this investigation and the corresponding results.
In this wooden positioning antenna structure, the scattering parameters and radiation characteristics of the printed dipole antennas are studied and investigated. As mentioned above, the proposed antenna system consists of a reflector plate, a wooden structure, and a number of printed dipole antennas. In this investigation, we studied the impact of the reflector and wooden structures on the radiation elements performance.
For this, the
From these figures, it is obvious that the presence of the reflector plate yields mainly to resonance point shifts. This fact is introduced by the change in the value of frequency that the magnitude of
From these considerations, it is obvious that the impact of the reflector plate on the magnitude of
Moreover, simulated and experimental results introduce a second resonance point at the frequency range of 4 GHz. The reflector structure affects the magnitude of
These considerations are related to the single-element antenna design. In order to expand this study on multielement antenna performance, we investigate the magnitude of
Magnitude of
More precisely, these elements have the same resonance points, and the corresponding resonance bandwidths are quite identical, too. Mainly from experimental results, it is obvious that the form of each dipole-element curve declines from that which corresponds to single-element case. At the first resonance point, the minimum value of the magnitude of
For further analysis, Figures
Magnitude of
These simulated and experimental results indicate that the presence of the reflector structure affects the magnitude of
Another important issue on printed dipole performance corresponds to the radiation characteristics and how these are affected by the reflector structure. This impact was studied by measuring the radiation pattern of the printed dipole at the single and multiple-element antenna configurations. In particular, Figure
Simulated radiation diagrams of dipole with and without reflector at 2.44 GHz.
Simulated radiation diagrams of dipole on reflector plate at 2.44 GHz and 2.33 GHz.
Experimental radiation diagrams of dipole with and without reflector at 2.44 GHz.
Experimental radiation diagrams of dipole on reflector plate at 2.44 GHz and 2.33 GHz.
ULA array on reflector plate and wooden positioning structure in RF anechoic chamber.
At first, Figures
For analysis on multiple-element antenna performance, Figure
Simulated radiation diagrams of single and element 2 dipoles without reflector plate at 2.44 GHz.
Experimental radiation diagrams of single and element 2 dipoles without reflector plate at 2.44 GHz.
From these results, it seems that the printed dipole and the element 2 on the ULA array have the same radiation characteristics on both E and H plane. This consideration indicates that the radiation patterns of each of the four dipoles at the ULA array are not affected by the presence of the adjacent elements. Single or multiple printed dipole antenna configurations have the same radiation characteristics. The last observation is meaningful for multiple-element antenna performance and the corresponding wireless applications.
Furthermore, the impact of the reflector structure on the ULA array was also investigated. For this purpose, Figures
Simulated radiation diagrams of element 2 dipole on reflector plate at 2.33 GHz and 2.44 GHz: (a) E-plane and (b) xy-plane.
Experimental radiation diagrams of element 2 dipole on reflector plate at 2.33 GHz and 2.44 GHz. (a) E-plane (b) xy-plane.
From these radiation patterns, it is obvious that the simulated results are in agreement with the corresponding experimental. Both of them indicate that the element 2 on the reflector plate introduces high direction. This increased value of directivity approximates the corresponding directivity that the single dipole introduces in case of the reflector’s presence.
The analysis above corresponds to the reflector structure impact on the single or multiple-element antenna performance. As mentioned in previous section, the reflector plate is arranged on the wooden base, in order to implement the proposed antenna structure. For this, an appropriate analysis on wood effects at antenna performance took place. At first, the magnitude of
Magnitude of
From these curves, it seems that the simulated results indicate no effect on the single printed dipole performance by the wooden base’s presence. Instead, the corresponding experimental measurements introduce a quite small increment on the magnitude of
For multiple-element antenna configuration, the measurements above were done with the ULA array and the wooden base. In particular, the corresponding simulated and experimental curves for the elements at the ULA array and the single dipole on the wooden base are depicted in Figures
Magnitude of
Both simulated and experimental results in these figures above indicate that the impact of the wooden base on the magnitude of
Further investigation on impact of the wooden base in the printed dipole radiation patterns produces an amount of simulated and experimental results. Figure
Schematic of investigated antenna configuration.
Radiation pattern of dipole with and without wooden base in E-plane: (a) simulated and (b) measured.
Both simulated and experimental curves present the gain of the dipole in E-plane for two different cases, with and without the wooden base’s presence. From these results, it is realized that the presence of wood affects the radiation pattern of printed dipole and provides small variations on the antenna gain. This observation is crucial in directions where this element radiates, efficiently. For this purpose, the printed dipole orientation is optimized in the proposed antenna implementation. In particular, the printed dipole has to be arranged on the wooden positioning structure, so that its axis is oriented vertical to the wooden arms at the same plane. The dipole axis orientation has to be aligned on
The proposed implementation represents a narrowband antenna configuration for wireless applications at the frequency range of 2.4 GHz. The radiation element is realized by a compact printed dipole with integrated balun. The reflector plate and the wooden base provide antenna’s performance. The effect of them on scattering parameters and radiation pattern of the dipole are studied and investigated for single and multiple-element antenna configurations. Simulated and experimental measurements on the magnitude of
This research project (PENED) is cofinanced by E.U.-European Social Fund (80%) and the Greek Ministry of Development-GSRT (20%).