Volume 75, Issue 5-6

This paper presents a compact and the low-cost coupled line band-pass filter with application to future generation millimetre-waves and 5G communications. The proposed approach of the filter design is based on the coupled-line and centre tapped upper and lower stepped impedance resonators. These resonators generate the sharp rejection, wide bandwidth, and abet to realize the compact filter. A detailed theoretical as well as the numerical analysis of the filter has also been investigated. As a demonstration, the proposed band-pass filter configuration has been designed and fabricated at the 33.5 GHz frequency using a low-cost PCB technique. It has observed that the proposed filter, results in a better return loss and the low insertion loss. The experimental results has been presented and compared with the simulated results and has found quite satisfactory. Moreover the results obtained validate a good agreement with each other.

This paper presents a novel design of rigid coaxial line based variable stub tuner. It incorporates controlled drive for the movement of shorting ring along the length of the stub inside the coaxial line. The ring is housed inside stub through linear slot over the coaxial conductor. Inbuilt slot at outer conductor of coaxial line introduces undesirable discontinuity which deteriorates the performance of the stub. It needs to be compensated to get the desirable performance of tuner. The effect of discontinuity has been analyzed using circuit modelling and compensated in design itself for the desired performance. The compensated tuner has been fabricated and tested where test results are found as return loss better than 25 dB and Voltage Standing Wave Ratio (VSWR) in between 1.1 and 1.9 in the frequency range of 80–850 MHz. The presented work is useful for the development of high power stub tuner in the range of High Frequency (HF), Very High Frequency (VHF) and Ultra High Frequency (UHF) which is an interest of wide spread applications in areas of communication, defence, satellite, radar, tokamak etc.

In this paper, two types of coaxial coupler and waveguide coupler for different frequency helix traveling wave tubes (TWTs) are designed, fabricated and cold tested. The coaxial coupler includes of window ceramic and RF transformer section. At present multi-section impedance transformer design approach is used for wideband helix TWTs. In any helix TWT, impedance of the source is transformed to the characteristic impedance of helix. This is done by the quarter-wavelength (λ/4) impedance transformation approach. The simulated results of different types of couplers are carried out by HFSS and CST microwave studio software and compare with experimental results. Three-dimensional electromagnetic field simulators allowing the any geometry with port excitations it is possible to model the complex coaxial and waveguide type couplers with helix SWS assembly and predict its desired return loss performances.

For the next generation wireless networks, backhaul links with data rates of several Gbit / s are required. Line-of-Sight-MIMO with optimally arranged antennas can exploit the full multiplexing gain of orthogonal MIMO streams to achieve high throughput, as shown in recent works utilizing the 60 GHz mm wave band. In contrast, conventional MIMO systems operating at sub-6 GHz carrier frequencies, as utilized in modern WLAN networks, rely on rich scattering channels to enable reliable transmissions. In this work, we explore the feasibility of applying the LoS-MIMO concept to wireless single-carrier links operating at sub-6 GHz frequencies. For this, we investigate the sub-6 GHz LoS-MIMO channel in a 4 × 4 MIMO configuration by performing measurements in an anechoic chamber and an outdoor backhaul-like environment. In addition, different adaptive equalizers are evaluated. The results show, that the LoS-MIMO concept holds for sub-6 GHz frequencies both in pure LoS and in outdoor environments. It provides high multiplexing gain; however, the multipath propagation limits the potential performance of the equalizers in terms of achievable BER.

Here, a planar Ultra-Wideband (UWB) wearable Multiple Input Multiple Output (MIMO) antenna is designed for on-arm wearable Wireless Body Area Network (WBAN) applications. This antenna is designed on a 100% cotton cloth substrate. The two-port MIMO antenna has a dual spinning wheel shape like radiators with the partial ground and microstrip feedings. The two partial grounds are connected to a rectangular strip to have common ground. The complete surface area of the antenna is 40 ×  70 mm 2 . In comparison with recently published papers in the same research area, the bending and SAR analysis are also done to estimate the performance of this wearable antenna, which is the novelty of this research work. For entire UWB bandwidth, S–parameters, gain, efficiency, and diversity parameters (Channel Capacity Loss [CCL] and Envelope Correlation Coefficient [ECC]) and far-field simulations are done for all cases such as flat, bend, on body antenna, which demonstrates the appropriateness of the presented antenna to be operated to the human arm.

In this article, cross-shaped metallic parasitic strips based two radiator element multiple-input multiple-output (MIMO) dielectric resonator antenna (DRA) is excited by quadrature wave transformer microstrip feedline, designed, simulated and fabricated for ultra-wideband (UWB) applications. The proposed MIMO antenna structure is implemented with the help of two rectangular-shaped radiator elements that supports three modes HE 11 δ , HE 21 δ , and HE 12 δ at 4.4, 8.3, 10.8 GHz respectively. These fundamental and higher-order modes are supported to wide impedance bandwidth. Inverted T-shaped metallic strip and ground stub to improve the impedance bandwidth 104.6% (3.3–10.8 GHz) with 5.7 dBi peak gain, to enhance the coupling coefficient by stub, scissor-shaped defected ground structure and cross-shaped metallic parasitic strips are used in the existed structure. The MIMO diversity parameters are implemented as simulated ECC ≤ 0.003, DG ≥ 9.98 dB, and CCL ≤ 0.68. All the obtained MIMO antenna parameters are within the acceptable limit for providing high data rate for UWB applications.

A two-port multiple input multiple output (MIMO) dielectric resonator antenna is proposed where two orthogonally connected feed lines are combined to unite two orthogonally produced modes. The feed lines build a hybrid network. The backplane is defected by a circular defected ground structure (CDGS), which is extended by two rectangular slits placed orthogonally with the input ports. The antenna uses a single ‘H/I’-shaped dielectric resonator (DR) element. It covers frequency spectrum from 7.29 to 10.65 GHz and fulfils the international telecommunication union (ITU) (8–8.5 GHz) and Maritime Radio Navigational (8.85–9 and 9.2–9.5 GHz) application bands. The antenna offers very high port isolation (>18 dB) and diversity properties throughout the whole application band. The antenna also provides circular polarization (AR ≤ 3 dB) in the operating ranges from 8 to 8.25 GHz and 8.85 to 8.9 GHz. Simulated and measured results make clear to the antenna most suitable for MIMO operation.

Conical Terahertz DRA (dielectric resonator antenna) have been designed and investigated at terahertz spectrum i.e. 10 THz. Lower terahertz frequency band is useful for high data speed communication and upper band is used for optical sensors and free space wireless communications. Novelty in this work is to open up research in. terahertz. A unique geometry based dual band terahertz DRA with mathematical formulations has been proposed. The comprehensive analysis in terahertz regime have been worked out with S11, VSWR, radiation pattern and efficiency using conical TDRA. The conical terahertz DRA is designed at 10 THz frequency with 4.9 dBi, gain with bore sight radiation pattern. The equivalent circuit of conical terahertz DRA have been evaluated for dynamic impedance showing frequency dependence nature.

We present the design of a compact tri-band adhesive planar antenna which operates as a gateway for biomedical applications. Operating in the Industrial, Scientific and Medical (ISM) band (2.4–2.5 GHz), the Institute of Electrical and Electronics Engineers (IEEE) 802.15.6 Wireless Body Area Network Ultra-Wide Band (WBAN UWB) (3.1–10.6 GHz) and the IEEE 802.11 Wireless Local Area Network or WLAN (WLAN) band (5.15–5.725 GHz), the antenna is useful in the context of body-signal monitoring. The ISM band is used for in-body communication with the implanted medical devices, whereas the WBAN and WLAN bands are for off-body communication with the base station and central medical server, respectively. We have designed our antenna to operate at 2.34/3.20/4.98 GHz. The simulation results show that the antenna has 10 dB bandwidths of 420 MHz (2.07–2.49 GHz), 90 MHz (3.16–3.25 GHz), and 460 MHz (4.76–5.22 GHz) to cover the ISM, WBAN, and WLAN bands, respectively. The proposed antenna is printed on a flexible Rogers RT/duroid 5880 epoxy substrate and it occupies a compact volume of 24 × 24 × 0.787 mm. The designed antenna is simulated using HFSS and the fabricated antenna is experimentally validated by adhering it to a human skin. The simulated and measured performance of the antenna confirms its omnidirectional radiation patterns and high return losses at the three resonant bands.

A slot loaded annular sector microstrip antenna having a pentaband operation is presented. The antenna has six resonant frequencies and the fourth band occurs between the fourth and fifth resonance. The radiation pattern is linearly polarized at all the frequencies. The radiation is broadside directed at the first three bands, tilted at the fourth and split at the fifth band. The resonant frequencies are located at 3.543 (Sub-6 GHz 5G band), 5.118 (ISM 5.2 GHz), 5.625 (WiMAX 5.8 GHz), 8.463, 9.534 and 11.25 GHz. Analysis of the structure is done using Multiport Network Modeling which fairly accurately predicts the resonant frequencies of the structure.