Ultra Wideband Signals and Systems in Communication Engineering

The design of a four-band slot antenna for the global positioning system (GPS), worldwide interoperability for microwave access (WiMAX), and wireless area network (WLAN) is presented. The antenna consists of a rectangular slot with an area of ${\mathbf{0}}.{\mathbf{37}}{\lambda _g} \times {\mathbf{0}}.{\mathbf{14}}{\lambda _g} = {\mathbf{48}} \times {\mathbf{18}}\;{\bf m}{{\bf m}^{\mathbf{2}}}$ (where ${\lambda _g}$ is the guide wavelength), a $T$ -shaped feed patch, an inverted $T$ -shaped stub, and two $E$ -shaped stubs to generate four frequency bands. The radiating portion and total size of the antenna are less than those of the tri-band antennas studied in literature. Parametric study on the parameters for setting the four frequency bands is presented and hence the methodology of using the design for other frequency bands is proposed. The multiband slot antenna is studied and designed using computer simulation. For verification of simulation results, the antenna is fabricated and measured. The simulated and measured return losses, radiation patterns, realized peak gains, and efficiencies of the antenna are presented. Measured results show that the antenna can be designed to cover the frequency bands from 1.575 to 1.665 GHz for the GPS system, 2.4–2.545 GHz for the IEEE 802.11b&g WLAN systems, 3.27–3.97 GHz for the WiMAX system, and 5.17–5.93 GHz for the IEEE 802.11a WLAN system. The effects of the feeding cable used in measurement and of the cover are also investigated.

A Multiband Slot Antenna for GPS/WiMAX/WLAN Systems

In this study, a millimetre-wave (MMW) antenna is presented for the fifth-generation (5G) wireless multiple-input multiple-output (MIMO) applications, in order to offer numerous advantages including compactness, planar geometry, high bandwidth, and high gain performance. The concept of defected ground structures has been deployed for the first time in MIMO antenna design at MMW spectrum to fulfil 5G requirements of high bandwidth with compactness and low design complexity. The top surface of antenna comprises of a coplanar waveguide-fed T-shaped radiating patch element, while the bottom part is designed to constitute a partial ground loaded with two iterations of symmetrical split-ring slots at an optimised distance. Experimental results depict a wide bandwidth of 25.1-37.5 GHz, as well as a peak gain of 10.6 dBi at 36 GHz. Moreover, numerically evaluated efficiency of >80% is observed over the entire intended bandwidth of operation. For the demonstration, four-element MIMO antenna array of the proposed antenna element is also fabricated and tested, in order to validate high isolation between the adjacent elements, which makes the proposed antenna a potential candidate to be integrated in cellular phones and base stations for 5G MIMO systems and services.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-map.2017.0467

Millimetre-wave T-shaped MIMO antenna with defected ground structures for 5G cellular networks

A frequency-reconfigurable antenna designed using metasurface (MS) to operate at around 5 GHz is proposed and studied. The frequency-reconfigurable metasurfaced (FRMS) antenna is composed of a simple circular patch antenna and a circular MS with the same diameter of 40 mm (0.67 λ) and implemented using planar technology. The MS is placed directly atop the patch antenna, making the FRMS antenna very compact and low profile with a thickness of only 3.048 mm (0.05 λ). The MS consists of rectangular-loop unit cells placed periodically in the vertical and horizontal directions. Simulation results show that the operating frequency of the antenna can be tuned by physically rotating the MS around the center with respect to the patch antenna. The MS placed atop the patch antenna behaves like a dielectric substrate and rotating the MS changes the equivalent relative permittivity of the substrate and hence the operating frequency of the FRMS antenna. Measured results show that the antenna has a tuning range from 4.76 to 5.51 GHz, a fractional tuning range of 14.6%, radiation efficiency and a realized peak gain of more than 80% and 5 dBi, respectively, across the tuning range.

Frequency-Reconfigurable Antenna Using Metasurface

In this paper, an attractive multi-band RF planar sensor, suitable for non-destructive testing of dispersive materials, is proposed. The proposed sensor is based on a number of complementary split ring resonator (CSRR) unit cells etched in the ground plane of the microstrip line. Each CSRR unit cell can be represented by a narrow band reject filter with its center frequency corresponding to the resonant frequency of the respective CSRR cell. The proposed technique is used to design the two, three and four band microwave sensors operating at 1.5 GHz, 2.45 GHz, 3.8 GHz, and 5.8 GHz. The distance between the two adjoining CSRRs is minimized for each case without appreciably increasing the inter-cell coupling effect. The transcendental equations required for determining the complex permittivity of the material under test in terms of the resonant frequency are derived from the numerical data obtained using the electromagnetic solver, the CST studio. These numerical equations are then used to obtain the dielectric properties of various test samples, which are measured using the vector network analyzer. The detailed air gap analysis is also performed for checking the accuracy of the designed planar sensor under the real situation. The proposed sensors are fabricated on 0.8 mm thick FR4 substrates using the standard photolithography technique. A number of standard samples are tested using the fabricated sensors in multiple frequency bands, and a good agreement between the obtained results and the data available in literature shows the applicability of the proposed scheme.

Multi-Band RF Planar Sensor Using Complementary Split Ring Resonator for Testing of Dielectric Materials

A planar dual-band monopole antenna with a frequency-tunable band is presented. The structure of the antenna radiator has a stem connecting to two branches that are used to generate two frequency bands at around 2.4 and 3.4 GHz for Worldwide Interoperability for Microwave Access (WiMAX) applications. The lower band covers the WiMAX frequency band of 2.3–2.4 GHz, while the higher band is frequency-tunable to the WiMAX frequency bands of 3.3–3.4, 3.4–3.6and 3.6–3.8 GHz. The frequency tunability is achieved by using the reverse-bias voltage across a varactor that is placed between the stem and one of the radiating branches of the radiator. In this study, the radiating branch responsible for the higher band is selected for tuning. A simple and novel biasing circuit, consisting of two radio frequency (RF) choke resistors and an L-shaped stub, is designed for biasing the varactor. Results show that the higher band can be continuously tuned in frequency, yet keeping the lower band unchanged. The reflection coefficient, radiation pattern, and efficiency of the antenna are studied using computer simulation and measurement.

Dual-Band Monopole Antenna With Frequency-Tunable Feature for WiMAX Applications

The design of a frequency-reconfigurable planar monop- ole antenna with a wide tuning range for cognitive radio is presented. The radiator of the antenna consists of two sections, Section I and Sec- tion II, which are connected together using a PIN-diode. Section I is meandering and responsible for generating a high-frequency band at about 2.69 GHz. Section II has a U-shape and, together with Section I, generates a low-frequency band at about 2.39 GHz. The PIN-diode is used to select whether only Section I or both Sections I and II together to work as the radiator for the antenna. The radiator has a very com- pact size of only 11.5 3 8.4 mm 2 . Continuous tuning for the low- and high-frequency bands is accomplished by placing a varactor on Section I of the radiator. The varactor and the PIN diode are biased using very simple DC circuits. The frequency-reconfigurable antenna is studied, designed, and optimized using computer simulation. Measurement is used for verification of the simulation results. Results show that the antenna can be tuned from 2.69 to 3.0 GHz using Section I and from 2.39 to 2.62 GHz using both Sections I and II together. Using the PIN- diode, the antenna can achieve a wide tuning range of 2.39 to 3.0 GHz. The antenna performance in terms of tuning range, radiation pattern, realized peak gain, and efficiency is presented. The feeding cable used in measurement causes substantial discrepancies between the simulated and measured results. A simulation cable model is used to verify such cable effects. V C 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:145-152, 2014; View this article online at wileyonlinelibrary.- com. DOI 10.1002/mop.28070

Frequency‐reconfigurable monopole antenna with wide tuning range for cognitive radio

In this paper, a triple-band monopole antenna for WLAN and WiMAX wireless communication applications is presented. The antenna has a simple structure designed for 2.4/5.2/5.8 GHz WLAN and 3.5/5.5 GHz WiMAX bands. The radiator is composed of just two branches and a short stub. The antenna is designed on a 40 × 40 × 0.8 mm3 substrate using computer simulation. For verification of simulation results, a prototype is fabricated and measured. Results show that the antenna can provide three impedance bandwidths, 2.35–2.58 GHz, 3.25–4 GHz and 4.95–5.9 GHz, for the WLAN and WiMAX applications. The simulated and measured radiation patterns, efficiencies and gains of the antenna are all presented.

A triple-band monopole antenna for WLAN and WiMAX applications

The design of a compact antenna for use in wireless devices of the 2.4/5.2/5.8-GHz wireless-local-area network (WLAN) is presented. The antenna consists of an L-shaped monopole radiator (L-element) with microstrip-fed on one side of the substrate and a protruding meander-microstrip ground stub (M-stub) on the other side. The L-element and the M-stub generate a high-frequency band at around 5.4 GHz for the high WLAN bands and a low-frequency band at around 2.44 GHz for the low WLAN band, respectively. The antenna has a very compact size of only 25 × 25mm2, including the ground plane. Computer simulation is used to study, design, and optimize the antenna. For verification of the simulated performance, the antenna is fabricated and measured using the antenna measurement system, Satimo Stargate. The effects of the feeding cable used in measurement cause discrepancies between the simulated and measured performances. To verify the cable effects, the feeding cable is modeled in simulation. With the use of the cable model, the simulated and measured performances show very good agreements. A practical application of the proposed antenna is also studied by installing it on a printed-circuit board having the similar size of a smartphone. The impedance bandwidth, radiation pattern, peak gain, and efficiency of the antenna are studied and presented. Results show that the antenna is a potential candidate for small WLAN wireless devices. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:469–475, 2014

A compact monopole antenna for WLAN applications

The article presents the design of a compact dual-band monopole antenna with microstrip-fed for use in wireless devices in the worldwide interoperability for microwave access (WiMAX) system. The radiator of the antenna has a compact size of only 14.5 × 8.7 mm2 and consists of a short stem and two branches generating two frequency bands at around 2.4 and 3.5 GHz for the WiMAX system. The two frequency bands can be easily and independently set using the parameters of the two radiating branches. The antenna performance in terms of reflection coefficient, radiation pattern, peak gain, and efficiency is studied using computer simulation. For verification of simulation results, the antenna is fabricated and measured using the antenna measurement system Satimo Starlab. The feeding cable used to connect the antenna to the measurement system causes substantial discrepancies between the simulated and measured results. To study the cable effects, the feeding cable is modeled and used in computer simulation for studies. With the use of the cable model, the simulated and measured results agree very well. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1765–1770, 2013

X. L. Sun

Papers

Dual-Band Monopole Antenna With Frequency-Tunable Feature for WiMAX Applications

Frequency‐reconfigurable monopole antenna with wide tuning range for cognitive radio

A triple-band monopole antenna for WLAN and WiMAX applications

A compact monopole antenna for WLAN applications

Dual-Band Monopole Antenna with Compact Radiator for 2.4/3.5 GHz WiMAX Applications