AbstractThis research paper introduces a ultra-wideband (UWB) multiple input multiple output (MIMO)/diversity antenna with three rejected bands using one compact electromagnetic band gap (EBG) structure. The suggested EBG structure rejects three bands at WiMAX, WLAN, and the X-band within the passband of the UWB antenna. To achieve compactness in the conventional EBG structure, two via and square slots are introduced. This structure contributes to better impedance matching by using tapered feedline and slots in the radiating patch. To improve the isolation among all four compact UWB monopoles, decoupling strips are extended from the ground plane. Furthermore, the |S21| is below 17 dB in between the antenna elements and the envelope correlation coefficient is below 0.5, which are tolerable values within the UWB range. Furthermore, different MIMO/diversity characteristics are also discussed. An FR-4 substrate with dimensions of 38 × 45 × 1.6 mm3 is used for the fabrication of the suggested structure.

A compact eight-element antenna array based on loop antennas to be utilized in 5G mobile applications is presented in this paper. The individual antenna elements are installed on the side frames of the main circuit board. The array operates over LTE 42 (3.4-3.6 GHz) band with a compact size of 9.5x3 mm(2). The performance parameters that characterize the proposed array such as, isolation (>14.8 dB), Envelop correlation coefficient (ECC<0.1) are presented. The proposed array has decent channel capacity of 41 bps/Hz. The effects of installing battery and plastic frame have been discussed. In addition, the user's hand proximity effect on the proposed antenna array performance is presented. The array design was fabricated and its radiation characteristics are experimentally verified. The simulated and measured results are in good agreement with each other.

This article presents a dual notched Frequency Selective Surface (FSS) using a compact structure. Four sub-cell square split ring resonators (SSRRs) are imprinted over 8x8 mm(2) FR-4 substrate in a 90 degrees clockwise rotational symmetric manner. Dual resonant bands are obtained at 3.08 GHz ranging from 2.5 to 3.6 GHz and 10.2 GHz ranging from 7.95 GHz to 12.3 GHz. The proposed FSS covers the WiMAX band ranging from 2.5 to 2.7 GHz and 3.3 to 3.6 GHz and entire X-band ranging from 8 to 12 GHz. The structure presents a good angular response for both TE and TM incident polarized wave for normal and oblique angles. The pass band from 4.3 GHz to 5 GHz frequency with resonant dip at 4.6 GHz is obtained. The maximum relative deviation in between transmission zero frequency and angularly incident frequency is 1.2% and 4.2% at 70 degrees TM and TE polarized wave, respectively.

A band reject frequency selective surface (FSS) is presented in this paper. The given structure band stops the sub 6 GHz 5G frequency band for the electromagnetic shielding. Modified square loop (MSL) is imprinted over an FR-4 substrate. Modification is done in such a way that metallic patches are attached at all four sides of traditional SL. The proposed design band rejects the 5.05 to 6 GHz frequency band with resonant frequency at 5.55 GHz. The design presents polarization independent characteristics with good angular stability up to 60° for both the incident polarized waves (TE and TM). The −20dB fractional impedance bandwidth is 17.19 % in both the polarization cases. The structure is designed over a cost effective FR-4 substrate. The dimensions of the proposed design are $8 \times 8\text{m}\text{m}^{2}$. The effective dimensions of the given unit cell is $0.14\lambda \times 0.14\lambda. \lambda$ here corresponds to the resonant wavelength.

Recently demand of thin smartphones with wide screen display has been increased. A ten element compact monopole antenna array is introduced in this paper for ultrathin smartphone applications. The proposed array covers the LTE 42 (3.4GHz-3.6GHz) band. The structure provide isolation and efficiency better than -10dB and 60% respectively. The designed antenna elements are mounted on side-frames of size $150 \times3\times0.8 mm^{3}$. These attributes make the proposed design a possible candidate for ultrathin smartphone applications.

This article presents a dual-band 12-element antenna system based on slot antennas for fifthgeneration (5G) of mobile communication. The basic structure of each antenna element is composed of a T-shaped slot. The antenna array is designed to operate at LTE 42 and LTE 43 bands ranging from 3400–3600 MHz and 3600–3800 MHz, respectively. The impact on the antenna parameters due to the user’s hand is also explored. The isolation between antenna elements is better than 14.8 dB with a total efficiency of more than 74%. A small envelope correlation coefficient less than 0.05 and the channel capacity of 61.9 bps/Hz make the proposed array a viable solution for 5G smartphones.

In this paper an overview of an Ultra High Frequency RFID reader antenna for retail self-billing applications has been discussed. As each application of retail management vary for this region the role of RFID reader becomes important. Here all the requirements for UHF RFID reader and their antenna performance for retail practical application have been analysed and compared with various exiting antenna design. An example of reader antenna at centre frequency 900Mz with 4.5dBi gain is discussed.

With changing scenario, technology as well as communication has also changed. To improve telecommunication various techniques and trends are used and same can be seen in antenna designing. Distinctive antenna planning methods are known, to accomplish preferable isolation, efficiency, high data rate, and channel limit. With the increase in number of antenna arrays, efficiency can be improved up to 80% and channel capacity >50 s/Hz.

In this article, a compact frequency selective surface (FSS) is implemented using a modified metallic square loop structure for ultrawide band (UWB) stop behavior. The proposed structure exhibits wideband rejection over the entire UWB, ranging from 3.1 to 10.8 GHz. The proposed structure manifests polarization independent characteristics and provides a stable frequency response for normal and oblique angles under both transverse electric (TE) and transverse magnetic (TM) incident polarization. The angular stability for various polarization angles is also obtained. This structure provides a −10dB wide impedance bandwidth of 110.79%. The maximum relative deviation in between transmission zero frequency and angularly incident frequency is 5.9% and 6.2% at 80˚ TE and TM polarized wave, respectively, with attenuation more than 45 dB. The unit cell of the proposed FSS is imprinted on single-layer FR4 substrate of the dimensions 6 × 6 mm 2 , which is 0.062× 0.062 λ, where λ is the wavelength of lower cut-off frequency and is by far the smallest design for the desired UWB rejection FSS.

A 10 element multiple input multi output (MIMO)/Diversity antenna system is considered to work in Sub-6 GHz frequency range. The proposed design can work in long term evolution (LTE) band 42(3.4-3.6 GHz), LTE band 43(3.6-3.8 GHz) and LTE band 46(5.15-5.925 GHz). The proposed design consists of 10 identical and highly isolated T-shaped slot antennas fed with T-shaped lines. All three bands have the return loss values (<−6 dB) and total antenna efficiency (>83%) in free space. The peak value of envelope correlation coefficient is 0.06 and the calculated value of ergodic channel capacity is found to be greater than 41bps/Hz in all the bands.The effect of hand grip as well as the presence of battery and LCD screen is investigated. Simulated results are validated via fabrication and measurement of the proposed design.

In this research work, a circularly polarized (CP) monopole antenna is designed for Ultra-Wideband (UWB) applications. The CP UWB antenna is be made up of a reformed ring patch and ground plane. The slots and stubs are inserted in the ground to achieve CP in the UWB antenna. This antenna attained an Axial Ratio Bandwidth (ARBW) of 5 GHz (4.0–9.0 GHz) that lies in the UWB frequency range that is from 3.1 to 10.6 GHz. The designed antenna has a radiation efficiency of around 80% for the complete UWB frequency range. The CP UWB antenna is designed and fabricated using the FR4 with a compact size of 32 × 30 × 1.6 mm3 and with a peak gain of 6.8 dBi. Tested results are in good resembles with simulated ones.

This work presents an 18 element antenna system compatible with massive multiple input multiple output (MIMO)/Diversity fourth/fifth generation (4G/5G) smartphones. The antennas are designed at sub-6 GHz long term evolution (LTE) band 42 (3.4-3.6 GHz) and LTE band 43 (3.6-3.8 GHz). A simple slot type antenna is considered as the radiating element, with open ended slots used for obtaining a compact design. These slots also act as decoupling elements to improve the isolation among different radiators. The proposed antenna elements are designed on a low-cost FR-4 substrate having dimension of 150 mm $\times80$ mm $\times1.6$ mm, which can be typically used for 6-inch smart phones. The simulated and measured values of antenna gain are found to be greater than 5.3 dBi. Simulated and measured results of the proposed design show excellent impedance matching (reflection coefficient>20 dB), port isolation (>20 dB), total efficiency (>87%) and Envelope Correlation Coefficient (< 0.01) over the operating frequency. MIMO antenna performance metrics are verified by calculating the ergodic channel capacity with Kronecker channel model.

The design of a compact triple band notched Frequency Selective surface (FSS) at Ultra-Wide-Band (UWB) frequency range is presented. To make the proposed FSS polarization insensitive, on the upper part of the substrate a single metallic square loop (SL) and four identical rotational symmetric square split ring resonators (SSRR1) are placed, whereas at the bottom part another four identical rotational symmetric SSRR loops (SSRR2) are printed. Here each SSRR is rotated in 90 degrees clockwise direction over a single layered FR4 substrate. Triple band notches are obtained at WiMAX and Satellite communication downlink C-band (3.3-4.2 GHz), WLAN (5.1-5.9 GHz) and Satellite communication X-band (7.2-8.4 GHz) for both TE and TM polarizations. Angular stability is achieved until 70 degrees and attenuation of more than 25 dB is observed at resonance. The passband is obtained at 4.37 and 6.22 GHz. The proposed structure separates the closely spaced frequency bands by a ratio of 1.44 and 1.39 at the stop band and 1.42 at the pass band. The dimensions of the proposed FSS unit cell are 0.13 lambda(0) x 0.13 lambda(0) x 0.020 lambda(0), where lambda(0) represents the free space wavelength at the lowest resonance frequency. Good agreement between modeled and measured results is obtained.

A triple band notch MIMO/Diversity antenna using Inductance Boosted Compact Electromagnetic Band Gap (IB-CEBG) cells is presented in this paper. For obtaining compactness in the conventional EBG cell, spiral shaped defects are introduced. The proposed antenna obtains triple band notches in WiMAX (3.3–3.6 GHz), WLAN (5–6 GHz), and the X-band satellite communication (7.2–8.4 GHz) bands. IB-CEBG cells exhibits miniaturization of approximately 46% for WiMAX band, 50% for WLAN band and 48% for X-band Satellite communication band, compared to conventional EBG cells. To enhance the isolation among all four compact UWB monopoles, rectangular slots in the ground plane and parasitic decoupling arrangement are utilised. Further, a stepped structure with an angular separation of 90◦ is incorporated with individual monopoles to reduce mutual coupling effects. Stepped structure also helps in the better impedance matching by incrementing the path length. The results show that the magnitude of transmission coefficient is greater than 15 dB in between the ports of proposed antenna elements. Envelope Correlation Coefficient is less than 0.5, which lies in tolerable limits for Ultra-Wide band (UWB) frequency range. It has been noticed that notched frequency is dependent on IB-CEBG cell parameters. The proposed antenna is fabricated using an FR-4 substrate with overall dimensions of 58 × 90 × 1.6 mm3.

Frequency selective surface (FSS) is a type of spatial filter, which offer transmission and reflection characteristics by modifying the electromagnetic incident wave striking its surface. This chapter presents the basic concepts and principle of operation of the FSS. It discusses various types and techniques on the current state-of-art in the field of FSS and the applications of the FSS related to the antennas and summarizes the advantages and disadvantages of the FSS with future scope. The chapter also discusses the classification of FSS on the basis of FSS elements, design structure, and applications. On the basis of structure, FSS is classified into three categories, i.e., single-layer FSS, multilayer FSS, and three-dimensional FSS. Antennas or radar systems are vulnerable to the physical environment; consequently, the performance gets affected when exposed to the outer world. The most famous applications of the FSS are reconfigurable antennas, isolation in multiple-input multiple-output antennas, controlling radar cross section, and antenna radomes.

Wireless communication systems play a significant role in our day-to-day life. The printed antennas are used in wireless applications due to their low profile, ease of fabrication, and cost-effectiveness. However, they have major drawbacks such as low efficiency, narrow bandwidth, and surface wave excitation. To resolve these problems, in this chapter, an intensive study is performed in the field of electromagnetic band gap (EBG) structures. These are periodic and non-periodic structures that access or prevent the propagation of electromagnetic waves in a specific band of frequency. EBG structures are high-impedance surfaces and can be considered a good example of artificial magnetic conductors. These structures help improve the antenna performance by increasing gain and bandwidth and reducing mutual coupling between antenna elements. EBG structures can also be used to obtain band-rejection characteristics in UWB antennas and to design low-profile, compact, and multi-band antenna designs. In this chapter, several EBG structure-based patch antennas that best suit modern-day wireless communication systems are discussed. The current challenges and limitations of the typical patch antennas and different EBG structures are discussed in detail with some possible suggestions.

This paper describes the trends that are being followed in 5G antenna design. The antenna design techniques that are used in Sub-6 GHz range to achieve better isolation, efficiency and channel capacity will be discussed. Increasing the number of antenna in 5G MIMO antenna array can increase the efficiency up to 80% and capacity more than 50b/s/Hz in sub-6GHz range. Apart from this, designs of antenna in millimeter range are also investigated. Comparison of various antennas based on their performance is done.

In this editorial, a compact two element Ultra Wide Band Multiple Input Multiple Output (UWB MIMO) antenna with triple-band notch characteristics is presented. A single Two Via Compact Electromagnetic Band Gap (TVC-EBG) structure is used to achieve triple-band notches at WiMAX, WLAN, and X Band. An inverse L-shaped stub is inserted in the ground plane of the antenna to diminish mutual coupling amid antenna elements. Isolation and Envelope Correlation Coefficient (ECC) is less than -15 dB and 0.015, respectively. The diversity properties like Total Active Reflection Coefficient (TARC), Diversity Gain (DG) are less than -10 dB and greater than 9.95 dB respectively. The proposed antenna is designed using a low-cost FR4 substrate with overall dimensions of 21 x 36 x 1.6 mm(3).

This paper investigates the performance of compact triple band-notched Multiple Input Multiple Output (MIMO) antenna for Ultra-Wideband (UWB) communication. Open-ended quarter wavelength slots are inserted on the radiators. These slots are used to obtain notch bands at WiMAX/C band, WLAN band and the X-band Satellite Communication System that ranges in 3.3–4.2 GHz, 5– 6GHz, and 7.2–8.6 GHz, respectively. An I-shaped stub extends from the ground surface to minimize mutual coupling among radiating elements. Mutual coupling and Envelope Correlation Coefficient are found less than −15 dB and 0.2, respectively. The diversity characteristics like Mean Effective Gain Ratio and Total Active Reflection Coefficient are found around 1 dB and less than −10.5 dB respectively. The radiation efficiency of the radiator is more than 80% over the entire UWB frequency range. The proposed antenna is designed with the overall dimensions of 23 × 40 × 1.6 mm3.