Frequency and Pattern Reconfigurable Antenna for Emerging Wireless Communication Systems

A printed and minimal size antenna having the functionality of frequency shifting as well as pattern reconfigurability is presented in this work. The antenna proposed in this work consists of three switches. Switch 1 is a lumped switch that controls the operating bands of the antenna. Switch 2 and Switch 3 controls the beam switching of the antenna. When the Switch 1 is ON, the proposed antenna operates at 3.1 GHz and 6.8 GHz, covering the 2.5–4.2 GHz and 6.2–7.4 GHz bands, respectively. When Switch 1 is OFF, the antenna operates only at 3.1 GHz covering the 2.5–4.2 GHz band. The desired beam from the antenna can be obtained by adjusting the ON and OFF states of Switches 2 and 3. Unique beams can be obtained by different combination of ON and OFF states of the Switches 2 and 3. A gain greater than 3.7 dBi is obtained for all four cases

Isolation improvement in UWB-MIMO antenna system using slotted stub

Multiple-input multiple-output (MIMO) scheme refers to the technology where more than one antenna is used for transmitting and receiving the information packets. It enhances the channel capacity without more power. The available space in the modern compact devices is limited and MIMO antenna elements need to be placed closely. The closely spaced antennas undergo an undesirable coupling, which deteriorates the antenna parameters. In this paper, an ultra wide-band (UWB) MIMO antenna system with an improved isolation is presented. The system has a wide bandwidth range from 2-13.7 GHz. The antenna elements are closely placed with an edge to edge distance of 3 mm. In addition to the UWB attribute of the system, the mutual coupling between the antennas is reduced by using slotted stub. The isolation is improved and is below -20 dB within the whole operating range. By introducing the decoupling network, the key performance parameters of the antenna are not affected. The system is designed on an inexpensive and easily available FR-4 substrate. To better understand the working of the proposed system, the equivalent circuit model is also presented. To model the proposed system accurately, different radiating modes and inter-mode coupling is considered and modeled. The EM model, circuit model, and the measured results are in good agreement. Different key performance parameters of the system and the antenna element such as envelope correlation coefficient (ECC), diversity gain, channel capcity loss (CCL) gain, radiation patterns, surface currents, and scattering parameters are presented. State-of-the-art comparison with the recent literature shows that the proposed antenna has minimal dimensions, a large bandwidth, an adequate gain value and a high isolation. It is worth noticeable that the proposed antenna has high isolation even the patches has low edge-to-edge gap (3 mm). Based on its good performance and compact dimensions, the proposed antenna is a suitable choice for high throughput compact UWB transceivers.Deanship of Scientific Research at Majmaah Universit

Low-profile dual-band antenna with on-demand beam switching capabilities

In this study, a dual-band pattern-reconfigurable monopole antenna is designed and experimentally validated for Cband satellite communication systems and sensing UWB-radar applications. The proposed antenna has three resonances at 3, 7 and, 8.5 GHz. To incorporate the reconfigurability, two switches are applied in the ground plane to reshape the radiation pattern and focus the radiated power in the desired direction. Thus, the desired beam from the antenna can be obtained by adjusting the states of the switches. The proposed antenna has good impedance matching (S11 < − 10 dB for both operating bands), reasonable gain (>4.1 dBi), and high efficiency (>83%) for all switching states. A good agreement is observed between the simulated and measured results

Optimization of a Compact Wearable LoRa Patch Antenna for Vital Sign Monitoring in WBAN Medical Applications Using Machine Learning

This study introduces an innovative and compact wearable Long-Range (LoRa) patch antenna developed for monitoring vital signs, with a focus on heart rate and body temperature, in medical applications of Wireless Body Area Networks (WBAN). The antenna functions within the 868 MHz and 915 MHz LoRa bands, filling a notable gap in current literature regarding compact, wearable antennas operating below 1 GHz. Fabricated on a Rogers Duroid RO3003 substrate, the antenna incorporates a U-slot on a conventional rectangular patch, a matching stub, and a partial ground plane to enhance impedance matching and performance efficiency. Furthermore, the antenna displays a bidirectional radiation pattern in the E-plane and an omnidirectional pattern in the H-plane at both frequencies, achieving a peak gain of 2.12 dBi and a radiation efficiency of 99.8% at 868 MHz. The antenna, measuring $80 \times 60 \text {mm}^{2}$ ( $0.23~\lambda _{0} \times 0.17~\lambda _{0}$ ), was designed, simulated, and optimized using CST Microwave Studio (MWS) software. The performance under bending conditions was also assessed, revealing a bending an excellent efficiency with minimal impact on bandwidth and gain. Specific Absorption Rate (SAR) analysis indicated that all values were within the safety limits set by FCC and ICNIRP standards. Supervised regression machine learning models, specifically the ensemble regression model, were employed to predict resonance frequencies based on various antenna parameters, resulting in an R-squared score of 87.68%. This approach significantly reduced the computational time required for full-wave simulations, streamlining the design process. Real-world experimental validation involved open-field testing of the fabricated prototype for WBAN LoRa applications. The performance, evaluated on a LoRa transceiver system utilizing the LoRa SX1276, demonstrated the superior capabilities of the proposed antenna in heart rate and temperature monitoring, with an average RSSI improvement of -5 dBm at various points within a range of up to 1 km. This confirmed its improved signal transmission and reception capabilities in vital sign monitoring. The proposed antenna shows strong performance metrics and significant potential for WBAN in long-range applications, as evidenced by thorough experimental validations

Highly‐tunable and wide stopband microstrip bandpass filters

This paper presents the design of a highly‐tunable single‐ended and balanced filter with improved upper stopband performance. The proposed filters are designed using a spurline and a U‐shaped stepped impedance resonator (SIR) with a varactor diode connected to the open‐circuited end. A spurline is introduced in both designs to achieve wide stopband performance by suppressing the higher‐order modes. The proposed filters have high tunable ranges (single‐ended: 2.35‐3.99 GHz; balanced: 2.39‐4 GHz), low insertion losses (IL) (single‐ended: 0.07‐0.2 dB; balanced: 0.21 to 1.1 dB) and wide upper stopband performance (single‐ended: 3.79f1 with a rejection level higher than 20 dB; balanced: 3.79f1 with a rejection level higher than 20 dB). Performance of both filters are experimentally validated by comparing the experimental results with the simulated ones. Both filters can cover most of the fifth‐generation (5G) wireless communication bands with different biasing voltages (capacitance). When both filters are compared with state‐of‐the‐art filters, the proposed filters are found to achieve high tunable ranges with low IL and wide upper stopband performance

Low-profile dual-band antenna with ondemand beam switching capabilities

In this study, a dual-band pattern-reconfigurable monopole antenna is designed and experimentally validated for Cband satellite communication systems and sensing UWB-radar applications. The proposed antenna has three resonances at 3, 7 and, 8.5 GHz. To incorporate the reconfigurability, two switches are applied in the ground plane to reshape the radiation pattern and focus the radiated power in the desired direction. Thus, the desired beam from the antenna can be obtained by adjusting the states of the switches. The proposed antenna has good impedance matching (S11 < − 10 dB for both operating bands), reasonable gain (>4.1 dBi), and high efficiency (>83%) for all switching states. A good agreement is observed between the simulated and measured results

Tunable SIW Bandpass Filters With Improved Upper Stopband Performance

This brief propose the design and measurement of tunable, highly selective and wide-stopband microwave filters using substrate integrated waveguide (SIW) technology. A two pole filter is designed using optimized cavity parameters. Two higher order (4-pole) filters are designed by connecting two cavities vertically and horizontally through coupling slots. In this way, four poles are achieved in two cavities, in which the proposed filter produces 2×N poles in N cavities. A varactor diode is employed in both configurations to make the filters tunable. The proposed filters have wide upper stopband performance [20 dB up to 4.8f1 (Filter 1) and 20 dB up to 4.2f1 (Filter 2)], lower insertion losses [0.2-1.1 dB (Filter 1) and 0.2-1.5 dB (Filter 2)] and good tunability ranges [2.7-3.4 GHz (Filter 1) and 3.1-3.9 GHz (Filter 2)]. In order to validate the proposed design, a prototype is fabricated on RT/duroid 5870 substrate and measured. The simulated results accord closely with the measured results

Dielectric resonator antenna with reconfigurable polarization states

This study presents a simple and low-profile cylindrical dielectric resonator antenna (CDRA) for the fifth-generation (5G) band (3.5 GHz) with switchable polarization. The antenna can operate with linear or circular polarization (right-handed circular polarization [RHCP] or left-handed circular polarization [LHCP]) by changing the states of the PIN diodes below the CDRA, while keeping the same operating frequencies. The antenna operates at three modes (Mode 1, Mode 2, and Mode 3). It exhibits linear polarization in Mode 1, RHCP in Mode 2, and LHCP in Mode 3. The 10-dB bandwidths of 750 MHz (3.1–3.85 GHz), 950 MHz (3.03–3.98 GHz), and 960 MHz (3.03–3.99 GHz) are noted for Mode 1, Mode 2, and Mode 3, respectively. The 3-dB axial ratio bandwidth of 22.2% (3.09–3.86 GHz) and 21.4% (3.08–3.82 GHz) is achieved for Mode 2 and Mode 3, respectively. The reported antenna has high gain ( >5.25 dBi for all operating modes) and high radiation efficiency ( >79.8% for all operating modes). The proposed antenna is suitable for use in polarization diversity applications