This article demonstrates the design procedure of 3 x 3 and 5 x 5 L-band planar array, with dual-port dipole elements for polarization diversity and printed baluns for unbalanced feed. The polarization state can be reconfigured to linear or circular by applying a phase difference at the inputs of antenna elements. The final designs achieve the wide bandwidth of 200 MHz with active reflection coefficients less than -10 dB, peak gain variation of less than 1 dB in the boresight direction over the complete spectrum and +/- 45 degrees scanning in both elevation and azimuth planes with gain reduction of less than 2.5 dB from boresight. For the validation of the simulated results, a 3 x 3 array has been manufactured and tested. The measured results match well with the simulated results. The designed array is an excellent candidate for L-band radars with polarization diversity.

The key objective of the study was to examine the effectiveness of the probation system and community correctional services which are provided during the probation period in Pakistan. So the main focus of the study is that how the probation system does play a significant role for rehabilitation and reintegration of offenders to the society as better citizens. The Universe of the research is the probationers in jails of Pakistan. It is a survey based study. So, the multi stages sampling method has been applied. Hence seven districts have been selected by using simple random sampling techniques. Resultantly two hundred and ten probationers have been finalized through applying a proportionate sampling method. The result of the study showed that rehabilitation of probationers has been linked with supervision of probation officers. This relationship has been measured through change in the behavior of the probationers during their probation period and the role of the officers for their rehabilitation.

Fifth generation (5G) communication systems deploy a massive MIMO technique to enhance gain and spatial multiplexing in arrays of 16 to 128 antennas. In these arrays, it is critical to isolate the adjacent antennas to prevent unwanted interaction between them. Fifth generation absorbers, in this regard, are the recent interest of many researchers nowadays. The authors present a dual-band novel metamaterial-based 5G absorber. The absorber operates at 24 GHz and 28 GHz and is composed of symmetric meander lines connected through a transmission line. An analytical model used to calculate the total number of required meander lines to design the absorber is delineated. The analytical model is based on the total inductance offered by the meander line structure in an impedance-matched electronic circuit. The proposed absorber works on the principal of resonance and absorbs two 5G bands (24 GHz and 28 GHz). A complete angular stability analysis was carried out prior to experiments for both transverse electric (TE) and transverse magnetic (TM) polarizations. Further, the resonance conditions are altered by changing the substrate thickness and incidence angle of the incident fields to demonstrate the functionality of the absorber. The comparison between simulated and measured results shows that such an absorber would be a strong candidate for the absorption in millimetre-wave array antennas, where elements are placed in proximity within compact 5G devices.

A miniaturized four-port polarization diversity ultra-wide band multiple input multiple output (MIMO) antenna is presented in this article. Different structures are combined and excited with the tapered transmission line to obtain a reduced symmetric layout with the orthogonal arrangement in compact size. An inverted-c-shape partial ground plane is used to decouple the antenna elements placed in close proximity which reduced the overall size and improved the matched impedance of the MIMO antenna. Further, impedance bandwidth is improved by etching the slots in the ground plane. The overall dimension of the proposed compact MIMO antenna is 40 x 40 x 1.524 mm(3). The measured characteristics of a fabricated prototype on the FR4 laminate well matched with the simulated results. The antenna exhibits a quasi-omnidirectional radiation pattern on the H-plane throughout the operational bandwidth, with isolation greater than 16 dB, low envelope correlation, and gain variation. this antenna can efficiently be usedfor diversity applications and portable devices.

A simple but effective four port miniaturized Multiple Input Multiple Output (MIMO) antenna operating at wide-Ultra-wideband (UWB) region (3-13.5 GHz) including UWB (3.1-10.6 GHz), 11 GHz (10.7 to 11.7 GHz) and 13 GHz (12.75 to 13.25 GHz) frequency bands is proposed here. The phenomenon of the polarization diversity by deploying four orthogonal antenna elements is used to enhance the isolation between the MIMO antenna elements. The overall size (40 x 40 x 1.524 mm(3)) of the antenna is reduced by mitigating the unwanted interaction between the antenna elements by modifying patch shape and placing them in closed proximity to each other. The simulated results are verified by the measurements of the prototpe MIMO antenna. The results are compared with the state of the art antennas to demonstrate the valuability of the proposed antenna for the UWB MIMO applications. The proposed miniaturized UWB MIMO antenna is a potential candidate for the compact and portable devices.

An easy-to-manufacture and efficient four-port-printed Multiple Input Multiple Output (MIMO) antenna operating across an ultra-wideband (UWB) region (2.9–13.6 GHz) is proposed and investigated here. The phenomenon of the polarization diversity is used to improve the isolation between MIMO antenna elements by deploying four orthogonal antenna elements. The proposed printed antenna (40 × 40 × 1.524 mm3) is made compact by optimizing the circular-shaped radiating components via vertical stubs on top of the initial design to maximally reduce unwanted interaction while placing them together in proximity. The measurements of the prototype MIMO antennas corroborate the simulation performance. The findings are compared to the recent relevant works presented in the literature to show that the proposed antenna is suitable for UWB MIMO applications. The proposed printed UWB MIMO antenna could be a good fit for compact portable wireless electronic devices.

This paper presents a highly compact frequency-selective surface (FSS) that has the potential to switch between the X-band (8 GHz–12 GHz) and C-band (4 GHz–8 GHz) for RF shielding applications. The proposed FSS is composed of a square conducting loop with inward-extended arms loaded with curved extensions. The symmetric geometry allows the RF shield to perform equally for transverse electric (TE), transverse magnetic (TM), and 45° polarizations. The unit cell has a dimension of 0.176 λ0 and has excellent angular stability up to 60°. The resonance mechanism was investigated using equivalent circuit models of the shield. The design of the unit element allowed incorporation of PIN diodes between adjacent elements for switching to a lower C-band spectrum at 6.6 GHz. The biasing network is on the bottom layer of the substrate to avoid effects on the shielding performance. A PIN diode configuration for the switching operation was also proposed. In simulations, the PIN diode model was incorporated to observe the switchable operation. Two prototypes were fabricated, and the switchable operation was demonstrated by etching copper strips on one fabricated prototype between adjacent unit cells (in lieu of PIN diodes) as a proof of the design prototypes. Comparisons among the results confirmed that the design offers high angular stability and excellent performance in both bands.

An eight element, compact Ultra Wideband- Multiple Input Multiple Output (UWB-MIMO) antenna capable of providing high data rates for future Fifth Generation (5G) terminal equipments along with the provision of necessary bandwidth for Third Generation (3G) and Fourth Generation (4G) communications that accomplishes band rejection from 4.85 to 6.35 GHz by deploying a Inductor Capacitor (LC) stub on the ground plane is presented. The incorporated stub also provides flexibility to reject any selected band as well as bandwidth control. The orthogonal placement of the printed monopoles permits polarization diversity and provides high isolation. In the proposed eight element UWB-MIMO/diversity antenna, monopole pair 3-4 are 1800 mirrored transform of monopole pair 1-2 which lie on the opposite corners of a planar 50 × 50 mm 2 substrate. Four additional monopoles are then placed perpendicularly to the same board leading to a total size of 50 × 50 × 25 mm 3 only. The simulated results are validated by comparing the measurements of a fabricated prototype. It was concluded that the design meets the target specifications over the entire bandwidth of 2 to 12 GHz with a reflection coefficient better than -10 dB (except the rejected band), isolation more than 17 dB, low envelope correlation, low gain variation, stable radiation pattern, and strong rejection of the signals in the Wireless Local Area Network (WLAN) band. Overall, compact and reduced complexity of the proposed eight element architecture, strengthens its practical viability for the diversity applications in future 5G terminal equipments amongst other MIMO antennas designs present in the literature.

A compact printed monopole patch antenna with finite ground for future Sub 6 GHz 5G wireless communications is presented. The microstrip patch antenna with square slot has compact size of 30×34 mm 2 . Good impedance match over wide range (3 - 7 GHz band) is achieved by partial ground plane and optimization of stub. The antenna exhibits omni-directional radiation pattern with high gain over the entire band. The proposed antenna is realized on FR4 laminate and good agreement with simulated results indicate that proposed design can be employed in future 5G wireless applications for wireless communication between Internet of Things nodes.

This article reports on a novel Coplanar WaveGuide (CPW) loop feed structure with an isolated circular slot in the middle to excite a higher order mode in the cylindrical Dielectric Resonator Antenna (DRA). The proposed feeding structure is etched on the bottom side of the substrate and it allows the cylindrical DRA to achieve a broader bandwidth and higher gain. For demonstration, the proposed feeding structure with the DRA is optimized at the X-band over the frequency range from 7.88 GHz to 8.78 GHz. The simulation results and experimental validation confirmed that the proposed feeding structure for the DRA can be used for achieving a broader bandwidth, higher gain, and broadside radiation characteristics.

This article reports on a compact, single layer Frequency Selective Surface (FSS) for tri-band GSM shielding applications. The proposed FSS unit cell comprises of three independent elements. The outermost square ring suppresses GSM-900 MHz signals, the innermost annular ring is incorporated in the design to stop GSM-2100 MHz signals and the middle square ring is used to suppress GSM-1800 MHz signals with a -10 dB rejection bandwidth of 600 MHz, 100 MHz, and 250 MHz, respectively. Furthermore, the proposed FSS exhibits a stable frequency response when illuminated by waves at oblique angles of incidence and a polarization insensitive behavior up-to 60°. The proposed FSS unit cell is realized on an FR4 substrate. A finite prototype containing 8 ×7 unit cells with an overall size of 270 ×230 mm 2 is also fabricated and tested. A good agreement between the measured and simulated results showed that the proposed FSS can be employed for suppressing unwanted signals in the GSM-900, GSM-1800 and GSM-2100 bands.

This study reports on a highly miniaturised polarisation selective surface (PSS) for dual-band Wi-Fi and WLAN applications. The proposed unit cell consists of two independently tuneable square loops. The outer loop is split with a gap of 0.2 mm to introduce polarisation selectivity and miniaturisation for lower-frequency band of 2.5 GHz. The inner square loop is inductively loaded with arms to suppress 5.45 GHz frequency band. These configurations have resulted in a unit element size of lambda/14 at 2.5 GHz, which is not presented before to the best of the authors' knowledge. A wide rejection bandwidth (- 10 dB) of more than 600 and 1180 MHz is obtained around 2.5 and 5.45 GHz, respectively. Furthermore, the proposed PSS exhibits an excellent polarisation selective characteristic by generating two stopbands at 2.5 and 5.45 GHz when illuminated by horizontal (TM) incident waves, whereas vertically (TE) polarised incident waves result in the generation of passbands for these two frequencies. Numerical validation through equivalent circuit modelling of the proposed PSS has also been carried out. A finite prototype containing 31 x 33 elements is fabricated and tested. The measured results demonstrated that the PSS has excellent potential for applications that employ polarisation separators and wave generators.

An eight element, compact Ultra Wideband-Multiple Input Multiple Output (UWB-MIMO) antenna capable of providing high data rates for future Fifth Generation (5G) terminal equipments along with the provision of necessary bandwidth for Third Generation (3G) and Fourth Generation (4G) communications that accomplishes band rejection from 4.85 to 6.35 GHz by deploying a Inductor Capacitor (LC) stub on the ground plane is presented. The incorporated stub also provides flexibility to reject any selected band as well as bandwidth control. The orthogonal placement of the printed monopoles permits polarization diversity and provides high isolation. In the proposed eight element UWB-MIMO/diversity antenna, monopole pair 3-4 are 180o mirrored transform of monopole pair 1-2 which lie on the opposite corners of a planar 50 x 50 mm2 substrate. Four additional monopoles are then placed perpendicularly to the same board leading to a total size of 50 x 50 x 25 mm3 only. The simulated results are validated by comparing the measurements of a fabricated prototype. It was concluded that the design meets the target specifications over the entire bandwidth of 2 to 12 GHz with a reflection coefficient better than -10 dB (except the rejected band), isolation more than 17 dB, low envelope correlation, low gain variation, stable radiation pattern, and strong rejection of the signals in the Wireless Local Area Network (WLAN) band. Overall, compact and reduced complexity of the proposed eight element architecture, strengthens its practical viability for the diversity applications in future 5G terminal equipments amongst other MIMO antennas designs present in the literature.

This article reports on a compact metamaterial based electromagnetic absorber for Ku band radar applications. The proposed absorber offers -10 dB absorption from 14.29 GHz - 14.73 GHz having a maximum absorption peak at 14.6 GHz. The simulated and experimental results showed stable absorption response. Furthermore, it is experimentally shown that the proposed metamaterial absorber exhibits stable frequency response when illuminated by waves at oblique angles of incidence and polarization insensitive behavior up-to 60°. A good compliance between the measured and simulated results is observed.

A compact reconfigurable UWB MIMO antenna with four radiators that accomplish on-demand band rejection from 4.9 to 6.3 GHz is presented. An LC stub is connected to the ground plane by activating the PIN diode for each radiator. Two radiators are placed perpendicular to each other to exploit the polarization diversity on a compact 25 × 50 mm 2 FR4 laminate. Two additional radiators are then fixed obliquely on the same laminate (without increasing size) in angular configuration at ±45 ∘ perpendicular to the first two planar radiators still exploiting polarization diversity. The design is validated by prototyping and comparing the results with the simulated ones. On demand band rejection through the use of PIN diodes, wide impedance matching (2–12 GHz), high isolation amongst the radiators, compactness achieved by angular placement of the radiators, low gain variation over the entire bandwidth, band rejection control achieved by adjusting the gap between stub and ground plane, and low TARC values makes the proposed design very suitable for commercial handheld devices (i.e., Huawei E5785 and Netgear 815S housings). The proposed configuration of the UWB MIMO radiators has been investigated first time as per authors’ knowledge.

A planar, compact UWB MIMO antenna with four elements that accomplish band rejection from 4.91 to 6.41 GHz is presented. Rejection is accomplished using an L-C stub connected to the ground plane. The length of the stub is changed to reject the band starting from 2.5 GHz to above 8.8 GHz. The perpendicular placement of the elements enables polarization diversity and attains high isolation. Elements 3 and 4 are 180 degrees mirrored transforms of elements 1 and 2 on the opposite corners of the substrate. The antenna measures 50 x 50 mm(2) only with all four elements placed. The simulated results are validated by measurements of a fabricated prototype. The design attains the targeted specifications over the entire bandwidth of 2 to 12 GHz with a reflection coefficient better than -10 dB (except the rejected band), isolation more than 17 dB, low envelope correlation, low gain variation and strong rejection of the signals in the WLAN band. The small size and reduced complexity to obtain WLAN rejection makes the proposed design very useful for diversity applications and portable handheld devices with MIMO antennas as designed by panorama antenna.

A compact four-element multiple-input-multiple-output (MIMO) antenna for ultra-wideband (UWB) applications with WLAN band-notched characteristics is proposed here. The proposed antenna has been designed to operate from 2 to 12 GHz while reject the frequencies between 4.9 to 6.4 GHz. The four antenna elements are placed orthogonal to attain the polarization diversity and high isolation. A thin stub connected to the ground plane is deployed as a LC notch filter to accomplish the rejected WLAN band in each antenna element. The mutual coupling between the adjacent elements is at least 17 dB while it has low indoor and outdoor envelop correlation (<0.45) and high gain with compact size of two boards, each measuring 50 x 25 mm(2). To validate the concept, the prototype antenna is manufactured and measured. The comparison of the simulation results showed good agreement with the measured results. The low-profile design and compact size of the proposed MIMO antenna make it a good candidate for diversity applications desired in portable devices operating in the UWB region.

This article reports on a compact, single layer polarizer having angular independent metasurface. The proposed design can efficiently convert cross polarization to co-polarization and vice versa for X - band applications. The unit cell consists of a stretched 8 shaped element printed diagonally on an FR4 substrate having 1.6 mm thickness backed by ground plane. The proposed design converts a linearly polarized incident wave into its orthogonal counterpart after getting reflected from the metasurface polarizer provided that the incident wave is polarized in x or y axis. Two distinct polarization conversion peaks are obtained at 9.9 GHz and 11.2 GHz with overall bandwidth more than 2 GHz. The design also exhibits stable frequency response at oblique angles of incidence up-to 45°. A finite prototype with overall dimensions of 210 × 290 mm 2 containing 21 × 15 unit cells is fabricated and tested. A good agreement between the measured and simulated results showed that the proposed design can be employed for linear polarization conversion applications in X band.

This paper describes a design of a circularly polarized patch antenna array for Ku-band (14.45 GHz - 15.65 GHz) data-link for small to medium unmanned aerial vehicles. A multilayer antenna structure including the feeding network is studied in this paper. Compact size, circular polarization and bandwidth are important requirements in designing this system. The required bandwidth and circular polarization are achieved by truncating the corners of patch elements using a power divider and four bent slots to reduce the coupling effects and maintain the polarization purity. The antenna array is analyzed in terms of return loss, radiation pattern, axial ratio and total gain over the complete frequency band.

In this article, a circularly polarized coupled slot 1 x 4 stacked patch antenna array with enhanced bandwidth is proposed for S-band applications. Initially, a patch antenna radiating at 2.79 GHz is designed and maximum energy from feedline to patch element is coupled using two rectangular slots. Whereas, a parallel feedline structure is designed to provide polarization flexibility by creating 0, 90, and 180(o) phase differences. Then, a truncated patch element is vertically stacked in the design to achieve broader bandwidth of 600 MHz over frequency range from 2.4 to 3.0 GHz. Finally, a coupled slot 1 x 4 array stacked antenna array having feedline line structure to provide 90(o) phase difference for circular polarization is designed and fabricated for measurements. It is observed that the final design achieved target specification having impedance matching (|S-11| (dB) < -10 dB over 2.4 to 3.0 GHz, broad band circular polarization, and 11.5 dBic total gain. Overall, a good agreement between simulated and measurement results is observed.