A low-profile frequency reconfigurable monopole antenna operating in the microwave frequency band is presented in this paper. The proposed structure is printed on Flame Retardant-4 (FR-4) substrate having relative permittivity of 4.3 and tangent loss of 0.025. Four pin diode switches are inserted between radiating patches for switching the various operating modes of an antenna. The proposed antenna operates in five modes, covering nine different bands by operating at single bands of 5 and 3.5 GHz in Mode 1 and Mode 2, dual bands (i.e., 2.6 and 6.5 GHz, 2.1 and 5.6 GHz) in Mode 3 and 4 and triple bands in Mode 5 (i.e., 1.8, 4.8, and 6.4 GHz). The Voltage Standing Waves Ratio (VSWR) of the presented antenna is less than 1.5 for all the operating bands. The efficiency of the designed antenna is 84 % and gain ranges from 1.2 to 3.6 dBi, respectively, at corresponding resonant frequencies. The achieve bandwidths at respective frequencies ranges from 10.5 to 28%. The proposed structure is modeled in Computer Simulation Technology microwave studio (CST MWS) and the simulated results are experimentally validated. Due to its reasonably small size and support for multiple wireless standards, the proposed antenna can be used in modern handheld fifth generation (5G) devices as well as Internet of Things (IoT) enabled systems in smart cities.
In this paper, the design and experimental evaluation of a hexagonalshaped coplanar waveguide (CPW)-feed frequency reconfigurable antenna is presented using flame retardant (FR)-4 substrate with size of 37 × 35 × 1.6 mm 3 . The antenna is made tunable to three different modes through the status of two pin diodes to operate in four distinct frequency bands, i.e., 2.45 GHz wireless fidelity (Wi-Fi) in MODE 1, 3.3 GHz (5G sub-6 GHz band) in MODE 2, 2.1 GHz (3G Long Term Evolution (LTE)-advanced) and 3.50 GHz Worldwide Interoperability for Microwave Access (WiMAX) in MODE 3. The optimization through simulation modeling shows that the proposed antenna can provide adequate gain (1.44∼2.2 dB), sufficient bandwidth (200∼920 MHz) and high radiation efficiency (80%∼95%) in the four resonating frequency bands. Voltage standing wave ratio (VSWR) <1.5 is achieved for all bands with properly matched characteristics of the antenna. To validate the simulation results, fabrication of the proposed optimized design is performed, and experimental analysis is found to be in a considerable amount of agreement. Due to its reasonably small size and support of multiple frequency bands operation, the proposed antenna can support portable devices for handheld 5G and Wireless LAN (WLAN) applications.
This work proposes a low-profile, printed antenna that offers pattern and frequency reconfiguration functionalities printed on FR-4 substrate with a size of 46 × 32 × 1.6 mm3. The proposed antenna can operate in five different frequency bands, each one identified as a Mode, wherein there are possibilities of pattern reconfiguration. The frequency and pattern reconfigurability are made possible through 12 p-i-n diode switches (S1 to S12). The former is enabled through the switches S1 to S4 within the radiating patch, hence effectively controlling the resonant bands of the antenna; the latter is made possible through main lobe beam steering, enabled by the rest of the eight switches (S5 to S12), loaded in split parasitic elements designed on both sides of the radiator. The proposed antenna operates in the 5 GHz (4.52–5.39 GHz) band when all switches are OFF. When S1 is ON, the operating band shifts to 3.5 GHz (2.96–4.17 GHz); it changes to a 2.6 GHz (2.36–2.95 GHz) band when S1 and S2 are ON. When S3 is also turned ON, the antenna shifts to the 2.1 GHz Band (1.95–2.30 GHz). When S1–S4 are ON, the operating band shifts to a 1.8GHz (1.67–1.90 GHz) band. In all these bands, the return loss remains less than −10 dB while maintaining good impedance matching. At each operating band, the ON/OFF states of the eight p-i-n diode switches (S5 through S12) enable beam steering. The proposed antenna can direct the main beam in five distinct directions at 3.5GHz, 2.6 GHz, and 2.1 GHz bands, and three different directions at 5 GHz and 1.8 GHz bands. Different 5G bands (2.1, 2.6, 3.5, and 5) GHz, which fall in the sub 6GHz range, are supported by the proposed antenna. In addition, GSM (1.8 GHz), UMTS (2.1 GHz), 4G-LTE (2.1 GHz and 2.6 GHz), WiMAX (2.6 GHz and 3.5 GHz) and WLAN (5 GHz) applications are also supported by the proposed antenna, which is a candidate for handheld 5G/4G/3G devices.
In this paper, a printed low-profile antenna with frequency and pattern reconfigurable functionality is designed in three modes. Each mode operates at different frequency bands and has several options available for pattern reconfiguration in these bands. The proposed antenna consists of eight pin-diode switches (S1 to S8). The switches S1 and S2, installed in the radiating patch, are used for frequency reconfigurability to control the operating bands of the antenna. The rest of the six switches (S3, S4, S5, S6, S7, and S8), loaded in the stubs on the rear side of the antenna, are used for pattern reconfiguration to control the main lobe beam steering. When all switches are off, the proposed antenna operates in a wideband mode, covering the 3.82-9.32 GHz frequency range. When S1 is on, the antenna resonates in the 3.5 GHz (3.09-4.17 GHz) band. When both S1 and S2 are on, the resonant band of the antenna is shifted to 2.5 GHz band (2.40-2.81 GHz). A very good impedance matching with a return loss of less than -10 dB is attained in these bands. The beam steering is done at each operating frequency by controlling the on and off states of the six pin-diode switches (S3, S4, S5, S6, S7, and S8). Depending on the state of the switches, the antenna can direct the beam in seven distinct directions at 4.2 GHz, 4.5 GHz, and 5 GHz. The main beam of the radiation pattern is steered in five different directions at 5.5 GHz, 3.5 GHz, and 2.6 GHz operating bands for the given state of the mentioned switches. The proposed antenna supports several sub-6 GHz 5G bands (2.6 GHz, 3.5 GHz, 4.2 GHz, 4.5 GHz, and 5 GHz) and can be used in handheld 5G devices.
An ultra-wideband and efficient single layer polarization converting metasurface based on an L-shaped resonator is presented. The metasurface is based on an F4B dielectric substrate with relative permittivity of 2.65 and a loss tangent of 0.002. The size of the unit cell is 0.132λo × 0.132λo and the thickness of the metasurface is 0.05λo, where λo is the largest wavelength (corresponding to the lower frequency) in the operation band of interest. The proposed structure effectively transforms the linearly or circularly polarized incident wave to its orthogonal equivalent, which is justified by both simulated and measured results where the polarization conversion ratio (PCR) is greater than 90% in the frequency range from 8.6 GHz to 22 GHz with a fractional bandwidth of 88%. The polarization transformation process is illustrated in depth by the surface current distribution. Simulation results reveal that ultra-wideband is achieved because of strong electric and magnetic dipole resonances on the upper and the lower layer of the metasurface. Furthermore, the bandwidth and central frequency can be efficiently adjusted over a wide spectrum by changing the geometric aspects of the unit cell, thereby retaining high transformation proficiency. The designed converter can be used in applications such as antenna design, radar invisibility, imaging, microwave communications, and remote sensing.
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