Optimization of aperture coupled patch antenna element for mobile communication applications

A dual-polarized antenna array for 4G base stations is presented in this paper. The antenna array is a 2×4 uniform planar array and is composed of printed dual-polarized dipole antennas, operating in 1.7-2.2 GHz. By loading the metal plate and using antenna decoupling surface, the mutual coupling of the array is below -20dB.

Multi-beam antenna is an important way to increase the channel capacity of cellular communications. It is available in two ways, one is based on optical methods, such as Luneberg lens and Rotman lens. However, the common problem with this method is that the lens size is too large or difficult to process. Another method is based on beam-forming network composed of coupler and phase shifter, such as Butler matrix. The Butler matrix has been studied for a long time, in the form of microstrip, stripline, or substrate-integrated waveguide. The substrate-integrated waveguide with low insertion loss is mainly used in the higher frequency such as millimeter wave band. The microstrip is mainly used in 4G/5G base stations, suitable for broadband design and process. Low side-lobe level, narrow beams are especially important for multi-beam base station antennas. The traditional Butler matrix is 4 × 4 Butler matrix for 4-beam base stations. However, the traditional Butler matrix can only output equal-amplitude power, with a side-lobe level higher than −13.4 dB. The beam width is too wide due to the few number of antenna. The 4 × 4 Butler Matrix with attenuator can reduce the side-lobe level, but it will increase the insertion loss of the beam-forming network. The 4 × 4 Butler matrix with phase shifter and power divider can form a 4 × 6 Butler matrix, which reduce the beam width beam and side-lobe level. However, for large-angle scanning, not only the side-lobe level, but also the grating-lobe problem caused by the wide-angle scanning and wide antenna spacing needs to be solved. The array with triangle arrangement can reduce the side-lobe and grating-lobe level. A wide-band 4-beam antenna array and beam-forming network for 4G base stations are presented in this paper. Adopting triangular arrangement, the number of antenna in sub-array is increased, and the antenna spacing is reduced, resulting in good side-lobe and grating-lobe level suppression. The output amplitude and phase errors are small over a wide band, with low insertion loss.

A 77GHz microstrip antenna array with a small surface providing high side and grating lobe suppression is presented. This may serve as a starting point for 77GHz automotive radar applications. Multiple Wilkinson dividers guarantee both impedance matching at the input port (TX) as well as low return loss for the incoming (RX) signal. Phase shifting is done by adjusting the level of the Wilkinson dividers or by meandered sections of transmission line. The in∞uence of the radiation caused by the feeding network is analyzed and the absolute degradation in side lobe suppression is derived in this paper.

Field trial of an HTS filter system on a CDMA base station

This study examines the performance of the multi-user multiple-input-multiple-output (massive MIMO) systems with 1-bit, 2-bit and 3-bit analogue to digital converters (ADCs) under channel correlation and channel state information (CSI) errors. The OFDM modulated uplink with QPSK, 16QAM and 32QAM schemes are considered for the communication between the base station (BS) and the user equipment (UEs). The BS antenna array is assumed to be uniform linear (1D) or uniform rectangular (2D) arrays. Zero-Forcing (ZF) receiver has been employed by the BS due to its simplicity and superior performance over other linear receivers. Furthermore, we consider the square root raised cosine filter (SRRC) to enhance the performance of the low-resolution ADC systems. The results show that the resolution of ADCs mainly determines the modulation scheme and having a high-level channel correlation or CSI mismatch requires a higher resolution ADCs. Furthermore, it has been shown that the SRRC filter enhances the system performance even with low-resolution ADCs.

We propose joint spatial division and multiplexing (JSDM), an approach to multiuser MIMO downlink that exploits the structure of the correlation of the channel vectors in order to allow for a large number of antennas at the base station while requiring reduced-dimensional channel state information at the transmitter (CSIT). JSDM achieves significant savings both in the downlink training and in the CSIT uplink feedback, thus making the use of large antenna arrays at the base station potentially suitable also for frequency division duplexing (FDD) systems, for which uplink/downlink channel reciprocity cannot be exploited. In the proposed scheme, the multiuser MIMO downlink precoder is obtained by concatenating a prebeamforming matrix, which depends only on the channel second-order statistics, with a classical multiuser precoder, based on the instantaneous knowledge of the resulting reduced dimensional “effective” channel matrix. We prove a simple condition under which JSDM incurs no loss of optimality with respect to the full CSIT case. For linear uniformly spaced arrays, we show that such condition is approached in the large number of antennas limit. For this case, we use Szego's asymptotic theory of Toeplitz matrices to show that a DFT-based prebeamforming matrix is near-optimal, requiring only coarse information about the users angles of arrival and angular spread. Finally, we extend these ideas to the case of a 2-D base station antenna array, with 3-D beamforming, including multiple beams in the elevation angle direction. We provide guidelines for the prebeamforming optimization and calculate the system spectral efficiency under proportional fairness and max-min fairness criteria, showing extremely attractive performance. Our numerical results are obtained via asymptotic random matrix theory, avoiding lengthy Monte Carlo simulations and providing accurate results for realistic (finite) number of antennas and users.

The use of adaptive antennas in mobile communications base stations is self-explanatory. It offers the potential of increased spectrum efficiency, extended range of coverage and reduced delay spread. However, one major concern for adaptive antenna system is the non-linearity effects of the RF/IF chain upon digital baseband beamforming network. The article investigates these effects on the performance of adaptive antennas and suggests potential solutions to these non-linearity problems in base station transceiver systems.

Levels of radiofrequency radiations around two global systems for mobile communication (GSM) base stations located in the vicinity of a residential quarter and workplace complex were measured. The effects of the radiofrequency radiations on albino mice placed in exposure cages and located around the base stations over a six months period were carried out. The levels of radiofrequency (RF) radiations around the base stations were found to be between 488.51mV/m to 625.49mV/m compared to 59 mV/m in control stations. The results of the weight change experiment showed that over the 180 days of observation, there was weight gain in the exposed and control mice groups. Statistical comparisons of mean weight changes between exposed mice and control mice showed that there were no significant (P>0.05) differences between the weight of the test animals. The hematological studies revealed an elevation of white blood cell (WBC) counts in mice exposed to RF radiations compared to control group. There was however no significant (P>0.05) difference between the red blood cell counts in the exposed and control mice. There was also no significant (P>0.05) difference in the hemoglobin and glucose levels in the blood of both exposed and control mice groups. The red blood cells in exposed mice were however found to contain a higher number of macrocytes, poikilocytes, polychromatic cells and fewer target cells than the control mice. Histological studies of the heart and kidney of exposed mice showed only slight tissues deformities in kidneys of exposed mice compared to control. The relevance of these findings in setting radiofrequency radiation exposure guidelines and the need for more studies with widely varying biological parameters is very necessary as Nigeria leaps further into the communication age.

The wireless technology and broadband applications nowadays are very advanced from their early stages, but still an antenna is the indispensable item in these technologies. Hence this paper presented a compact micro strip 2X1 patch antenna for applications in WLAN band operating in the 5GHz–6GHz frequency range. Two element compact patch antenna with a combination of simple diamond decoupling structure is presented here. This antenna is constructed using RO 4350 substrate used for high frequency applications. After simulation with CST software the performance of the proposed antennas is investigated and compared to both the cases. An improvement of 9.2dB in coupling loss (S21) and 3.2dB in return loss (S11) are achieved.

Left Handed Metamaterial are the artificial material having negative value of refractive index thus following left hand property. Miniaturization is one of the best advantages offered by metamaterial. The paper presents the ideas about the use of metamaterials in innovative antenna designs from an engineering perspective. In the previous work, an eight shaped left handed metamaterial was designed with the help of FR4 substrate having μr = −4 and er = −2 at 1.8 GHz. Present work includes the use of previously designed structure as a base substrate for rectangular microstrip patch antenna for size minimization and characteristics improvement. The traditionally designed antenna resonates at 1.8 GHz with −12 dB return loss with low cost FR4 as a base substrate on the other hand metamaterial loaded layer antenna resonates at 1.8 GHz with −34 dB return loss. By adding left-handed metamaterial return loss has been improved and the effective volume of the rectangular microstrip patch antenna is also shortened by 71% and 47% reduction was applied to the base substrate of the patch antenna. Line feeding technique is used for the excitation of the proposed antenna. The process of designing and simulation is done using CST Microwave Studio 2010 and MATLAB is used for the retrieval of complex dielectric parameters using NRW (Nicholson Ross-weir) approach. The fundamental parameters of the antenna such as return loss, Bandwidth, gain, radiation pattern are obtained and are compared with the traditionally designed antenna.

The following topics are dealt with: integrated circuit design; low-power electronics; CMOS integrated circuits; CMOS analogue integrated circuits; operational amplifiers; system-on-chip; field programmable gate arrays; power engineering computing; Ge-Si alloys; wide band gap semiconductors.

Fixed-frequency beam scanning leaky-wave antennas (LWAs) that can scan their main beam over a specific frequency band are highly desired for future wireless communication systems. A composite right-/left-handed (CRLH) LWA is developed in this article that facilitates fixed-frequency continuous beam scanning over a wide operational frequency band. A variation of a simple single-layer nonreconfigurable frequency-based continuous beam scanning CRLH LWA is considered first. Its dispersion properties are approximately investigated using an equivalent circuit model. It is reported how two groups of varactor diodes can be incorporated into its basic circuit model to electronically control its dispersion behavior. An optimized reconfigurable CRLH LWA with practical dc biasing lines is then realized from this nonreconfigurable design. Fixed-frequency continuous beam scanning, from backward to forward directions through broadside, is reported over a wide operational frequency band. Simulations predict that the antenna can operate from 4.75 to 5.25 GHz with the main beam being continuously scannable at each frequency point. A prototype was fabricated, assembled, and tested. The measured results confirm its simulated performance characteristics.

We develop a framework for downlink heteroge- neous cellular networks with line-of-sight (LoS) and non-line- of- sight (NLoS) transmissions. Using stochastic geometry, we derive a tight approximation of the achievable downlink rate that enables us to compare the performance between densifying small cells and expanding base station (BS) antenna arrays. Interestingly, we find that adding small cells into a sparse network improves the achievable rate much faster than expanding antenna arrays at the macro BS. However, when the small cell density exceeds a critical threshold, the spacial densification will lose its benefits and further impair the network capacity. To this end, we present the optimal small cell density that maximizes the rate as practical deployment guidance. In contrast, expanding macro BS antenna array can always increase the capacity until reaching an upper bound caused by pilot contamination, and this bound also surpasses the peak rate obtained from deployment of small cells. Therefore, small cells are preferred for low rate requirements due to the rapid rate gain, and the massive MIMO is preferred for higher rate requirements due to better achievable rate.

This article investigates using a phased linear antenna array instead of the planar array to circumvent the problem that two frequency squint steering main beams cannot cover any two beam directions simultaneously. First, we approximate the donut-shaped main beam of the linear array by means of multiple pencil-shaped main beams of a virtual planar array for matching the steering main beam of the linear array with the multi-path sparse scattering channel model mathematically and give a method for calculating the number of antenna elements of the virtual array. Second, we cope with possible inter-user interference on a single squint main beam of the linear array in some scenarios by means of the power-domain non-orthogonal multiple access (PD-NOMA) technique, making it possible to support communication with two users on a single squint main beam at the base station (BS) side. The feasible domain of PD-NOMA is given when a single antenna is used for both the BS and the user end, assuming a two-user successive interference cancellation (SIC) decoding power ratio limit. Third, three algorithms are given for serving multi-user at the BS via squint beams of the linear array. Finally, numerical results show that the second proposed algorithm supporting PD-NOMA pairing within a single donut-shaped squint main beam significantly increases the number of simultaneous users served within a single cellular system.

We consider the information theoretic limits of the uplink in a MIMO cellular network with two types of macrodiversity. In the first case, the whole network acts as a multi-access channel where every base station antenna array is part of a central receiver (global macrodiversity). In the second case, we partition the network into clusters of cooperating base stations (local macrodiversity) thereby eliminating the growth in complexity at the receiver with network size. Macrodiversity is shown to provide very significant gains in sum capacity over single cell processing schemes where co-channel interference is the dominant impairment. We also explore the rate at which the sum capacity of the local macrodiversity scheme approaches that of global macrodiversity as the cluster size increases.