Fractional Impedance Bandwidth Research Articles

3D Printed High Gain Complementary Dipole/Slot Antenna Array

By employing the complementary dipole antenna concept to the normal waveguide fed slot radiator, an improved antenna element with wide impedance bandwidth and symmetrical radiation patterns is developed. This is achieved by mounting two additional metallic cuboids on the top of the slot radiator, which is equivalent to adding an electric dipole on top of the magnetic dipole due to the slot radiator. Then, a high-gain antenna array was designed based on the improved element and fabricated, using 3D printing technology, with stable frequency characteristics operated at around 28 GHz. This was followed by metallization via electroplating. Analytical results agree well with the experimental results. The measured operating frequency range for the reflection coefficient ≤−15 dB is from 25.7 GHz to 29.8 GHz; its corresponding fractional impedance bandwidth is 14.8%. The measured gain is approximately 32 dBi, with the 3 dB beamwidth around 4°.

Dual-Linearly Polarized, Electrically Small, Low-Profile, Broadside Radiating, Huygens Dipole Antenna

A dual-linearly polarized, electrically small, low-profile, broadside radiating Huygens dipole antenna is presented, that is, an advanced combination of electric and magnetic near-field resonant parasitic elements. Its prototype was fabricated and tested. The measured results are in good agreement with their simulated values. At 1.515 GHz, the prototype is electrically small ( $ka = 0.904$ ) and low profile ( $0.0483\lambda _{0}$ ). It exhibits high port isolation and a large front-to-back ratio (FTBR). The isolation between its two ports is demonstrated to be over 25.8 dB within its −10 dB fractional impedance bandwidth, 0.46%. When port 1 (port 2) is excited, the peak realized gain is 2.03 dBi (2.15 dBi) strictly along the broadside direction with a 12.4 dB (12.1 dB) FTBR.

A Differentially Driven Dual-Polarized High-Gain Stacked Patch Antenna

A differentially driven dual-polarized high-gain stacked patch antenna is presented in this letter. Two-layer stacked patches are adopted to increase the impedance bandwidth of the antenna. Each of the two stacked patches is inserted with four shorting posts for enhancing the antenna gain. To validate the proposed design, a prototype was meticulously fabricated and tested. The simulated and measured results of the antenna show fractional impedance bandwidths of greater than 19% for differential reflection coefficients less than −10 dB and a high isolation level between the two polarizations ( $ \vert S_{dd21}\vert $ larger than 35 dB). The antenna gain of up to 11 dBi was also measured for the two ports. Furthermore, a good agreement of radiation patterns between simulation and measurement with the cross-polarization levels lower than −16 dB over the whole operating frequency band is achieved.

Broadband circularly polarized dipole look‐like F‐shaped antenna with symmetrically inverted F‐shaped modified ground plane

AbstractA microstrip antenna consists of F‐shaped radiating structure with symmetrical F‐shaped modified or defected ground plane look‐like dipole antenna featured for broad axial ratio bandwidth (ARBW) is presented. Modified/defected ground plane comprises of an optimized rectangular ground plane united with symmetrically inverted F‐shaped structure printed at the bottom side of substrate. Furthermore, a narrow rectangular slit was imprinted from the modified ground plane to obtain broad ARBW. Proposed antenna optimized, fabricated, and experimentally examined. Measured results confirm that it can yield an fractional impedance bandwidth of approximately ≈37.5% and a 3‐dB ARBW of ≈31.7%. The measured gain range from 2 dB to 4 dB within the 3‐dB ARBW with maximum gain of 4 dBic. The cross polar rejection was observed better than 15 dB alongwith wide −3 dB beamwidth of 85°.

A wideband dual-mode complementary dipole antenna

ABSTRACTA wideband dual-mode complementary dipole antenna is proposed. The antenna is composed of a wideband slotline radiator and an electric dipole. It is excited by a coaxial cable at the center. A pair of slot stubs is used to perturb the second odd-order mode within the slotline radiator, and a dual-resonant wideband radiation characteristic is resulted in. An antenna prototype is then designed, fabricated and measured. The measured results show the antenna has a fractional impedance bandwidth of 40.2% with two resonances. Unidirectional radiation pattern and an average gain of about 7 dBi are satisfactorily achieved within the operating bandwidth as well. The antenna has a simple structure and exhibits a dual-resonant, wideband radiation characteristic.

Dielectric resonator based circularly polarized MIMO antenna with polarization diversity

AbstractIn this article, a dual sense dual port circularly polarized cylindrical dielectric resonator antenna (CDRA) is discussed for multiple input multiple output (MIMO) applications. Three exclusive features of the proposed radiator are (i) modified circule‐shaped aperture generates circular polarization for both the ports; (ii) proposed structure can generate left‐hand circular polarization (LHCP) and right‐hand circular polarization (RHCP) that depends on feed port selection; (iii) by introducing the concept of polarization diversity (LHCP/RHCP) and defected ground structure (DGS) between the two radiator, isolation is improved. A prototype of proposed radiator is fabricated and experimentally tested to authenticate the simulated results. The fractional impedance bandwidth for port 1 and port 2 is 15.1% and 14.9%, respectively. Within the targeted operating band, the isolation is better than −25 dB between the ports. Different diversity performance parameters are also calculated and they are also lie within their optimum limit. The proposed MIMO antenna is suitable for WLAN (5.5/5.8 GHz) applications.

A circularly polarized wideband high gain patch antenna for wireless power transfer

AbstractThis article deals with a microstrip patch antenna working at 868 MHz, suitable for the radio frequency wireless power transfer and energy harvesting applications. The proposed monolithic antenna is compact, lightweight and it is printed on a thick substrate in order to maximize the total gain in the broadside direction. The antenna radiates at 868 MHz with a fractional impedance bandwidth of 5% and it shows a gain of 4.14 dB.

A Novel 60 GHz Wideband Coupled Half-Mode/Quarter-Mode Substrate Integrated Waveguide Antenna

A novel wideband substrate integrated waveguide (SIW) antenna topology, consisting of coupled half-mode and quarter-mode SIW resonant cavities, is proposed for operation in the 60 GHz band. This innovative topology combines a considerable bandwidth enhancement and a low form factor with compatibility with low-cost printed circuit board manufacturing processes, making it excellently suited for the next generation, high data rate wireless applications. Moreover, exploiting SIW technology, a high antenna-platform isolation is obtained, enabling dense integration with active electronics without harmful coupling. The computer-aided design process yields an antenna that covers the entire 57–64 GHz IEEE 802.11ad band with a measured fractional impedance bandwidth of 11.7% (7 GHz). The measured maximum gain and radiation efficiency of the prototype are larger than 5.1 dBi and 65%, respectively, within the entire impedance bandwidth.

Low-Cost Aperture-Coupled 60-GHz-Phased Array Antenna Package With Compact Matching Network

A low-cost multilayer antenna-in-package solution, using the standard printed-circuit-board (PCB) process, is proposed for the 60-GHz-phased array system. The design procedure focuses on overcoming the fabrication restrictions and realizing a low-cost, broadband, compact and reliable package solution. The multilayer stack-up structure consists of three laminates and two bondply layers, with which the antenna element, vertical quasi-coaxial via transition, antenna feedline, power, and low-speed interfaces are realized. An aperture-coupled patch antenna with a compact fan-shaped feeding network and a vertical quasi-coaxial via transition are proposed, fabricated, and measured. For the single antenna element, including the vertical quasi-coaxial via transition, the measured fractional impedance bandwidth ( $\vert \text{S}11\vert dB) is 20.2%, and the measured peak gain is 6.9 dBi at 62 GHz. Based on the single antenna, a 16-element antenna package is realized in the dimension of 14 mm $\times14$ mm $\times0.925$ mm. Measurements show that each antenna element achieves a $\vert \text{S}11\vert $ less than −10 dB from 57.2 to 64.5 GHz, 4–7.5 dBi gain across all four IEEE 802.15.3c channels.

A Study of 28 GHz, Planar, Multilayered, Electrically Small, Broadside Radiating, Huygens Source Antennas

Two 28 GHz, planar, electrically small Huygens source antennas are presented that are broadside radiating and are based on multilayer PCB technology. The designs seamlessly integrate electric Egyptian axe dipole and magnetic capacitively loaded loop near-field resonant parasitic elements with a coax-fed dipole radiator. Both linearly polarized (LP) and circularly polarized (CP) systems are demonstrated. The simulations of the LP system indicate that it is electrically small: ka = 0.961; has peak realized gains and front-to-back ratios (FTBRs) in the range from, respectively, 3.77 to 4.54 dBi and 7.16 to 33.92 dB; and radiation efficiencies higher than 81.14% over its entire 2.14%, −10-dB fractional impedance bandwidth (FBW−10dB). A prototype was fabricated and tested; the measured and simulated results are in good agreement. The CP system exhibits similar properties: ka = 0.942; 1.41% FBW−10dB with a 0.47% 3-dB axial ratio fractional bandwidth; and peak realized gain, FTBR, and radiation efficiency values equal to 2.03 dBi, 26.72 dB, and 73.4%, respectively. To confirm their efficacy for on-body applications, the specific absorption rate values of both the LP and CP Huygens source antennas were evaluated and found to be very low.

Impedance Bandwidth Enhancement of a Novel Fabricated Fractal Patch Antenna Using Invasive Weed Optimization Algorithm

In this paper, the possibility of different configurations of a novel Koch fractal geometry for the miniaturization and broad banding of a microstrip patch antenna, while maintaining its gain and radiation pattern, is investigated. To achieve the best results, the invasive weed optimization (IWO) algorithm, which is shown to be very robust and adaptive, is used for optimization. The whole design procedure is auto-controlled by linking, the high-frequency structure simulator with MATLAB software. For the first configuration, IWO is used to find the best location of feed point to minimize the return loss, e.g., S 11 ( $$\left| {S_{11} } \right| < {-}10\;{\text{dB}}$$ ) and hence increasing the radiation efficiency of the proposed antenna. $$\left| {S_{11} } \right|$$ of about −40 dB was achieved. Next, the proposed fractal with air-filled substrate and a ring slit is presented. The key design parameters such as air gap height, the slot gap width, location of feed point have been optimized using IWO to obtain the best possible bandwidth. Simulation results show a fractional impedance bandwidth of about 40% (2.42–3.59 GHz). This band is used by weather radar and some communication satellites. Gain and radiation pattern of the proposed antenna are acceptable within the frequency bandwidth. A prototype of the antenna is also fabricated and tested. Measured parameters are in good agreement with the simulated results.

Design of Low-Profile Metamaterial-Loaded Substrate Integrated Waveguide Horn Antenna and Its Array Applications

A metamaterial-loaded substrate integrated wave-guide (SIW) horn antenna and its array application are researched in this communication. The mushroom-type metamaterial is placed in front of SIW horn aperture, and much improvement in impedance matching is achieved on a 1/ $20~\lambda _{0}$ -thickness substrate. Due to the backward wave generated by the metamaterial, backward endfire radiation pattern is observed for the proposed antenna. Experimental results indicate that a fractional impedance bandwidth of 10.6% is obtained for a fabricated prototype. Furthermore, a shunt four-element array and a monopulse four-element array are designed based on the novel SIW horn element to further enhance the radiation performance. Results show that performances of wide operating bandwidth, low profile, and backward endfire radiation pattern are maintained for the designed two arrays.

Design of a Dual-Band Microstrip Antenna With Enhanced Gain for Energy Harvesting Applications

In this letter, a dual-band circular patch antenna is introduced. The antenna consists of a circular patch with a direct feed through microstrip feedline designed to radiate at 2.45 GHz with fractional bandwidth of 4.5%. A circular slot is inserted into the ground plane that radiates by capacitive coupling between the patch and the ground plane. This slot radiates at 1.95 GHz with fractional impedance bandwidth of 5%. The antenna achieves good radiation characteristics by inserting a reflecting plane at optimum position behind it. The antenna has gain of 8.3 and 7.8 dBi at 1.95 and 2.45 GHz, respectively. This antenna is proposed for the rectenna; then it is designed to direct the main beam in a certain direction by increasing front-to-back (F/B) ratio with low cross-polarization levels by using defected reflector structure in the reflecting plane. The equivalent circuit of the proposed antenna is introduced to model the electrical behavior of the antenna. The proposed antenna can be used to harvest the energy from Wi-Fi and widely spread mobile networks. The proposed antenna was designed using CST Microwave Studio. The simulated and measured results show good agreement.

A 750–1000 GHz $H$ -Plane Dielectric Horn Based on Silicon Technology

A wideband THz H-plane dielectric horn antenna based on silicon (Si) technology is proposed in this paper. The antenna can be integrated with the planar structure circuit and the dielectric ridge waveguide. To fabricate the proposed antenna, the deep reactive ion etching high-resistivity Si fabrication process is used. The size of the proposed antenna is $3.13 \times 4 \times 0.1$ mm3. The operating frequency of the antenna ranges from 750 to 1000 GHz, which corresponds to a fractional impedance bandwidth of 28.6%. The antenna has a narrow beamwidth in the H-plane and a high gain. To test this antenna, the characterization of the metal waveguide diagonal horn for measurement is analyzed. Then the non-contact measurement method is applied to measure the designed dielectric horn. The simulated radiation efficiency of the antenna is higher than 80% while the measured gain of the antenna is larger than 8 dBi. Measured H-plane radiation patterns from the proposed antenna are presented and show reasonable agreement with the simulated results.

Wide‐band CPW‐fed slot antenna with parasitic directors for end‐fire radiation

In this study a novel slot array antenna backed by a metallic reflector has been presented which produces end-fire radiation. Several slots with different dimensions were etched in the ground plane of a thin substrate. Only first two slots were fed directly by a coplanar waveguide feed line while the other slots radiate by the mechanism of parasitic coupling. The simulation results show that the proposed antenna is capable of producing tilted end-fire beam in a wide frequency band ranging from 12 to 18 GHz. The fractional impedance bandwidth of the antenna was found to be 40%. A prototype of the design was also fabricated and measurements were taken. It was found that the simulated results for the return loss, radiation pattern and gain of the antenna are close to the measured ones. The peak measured gain was found to be 10 dB while the maximum gain in exact end-fire direction is almost 2 dB. As the radiating elements are slots therefore the antenna can be flush mounted in the conducting surface of an airborne vehicle. Moreover, due to the small thickness of substrate the antenna can be easily designed for conformal applications.

Bandwidth enhancement of dual‐layer patch antenna using low mutual‐coupling near‐field resonant parasiticl elements

ABSTRACTA pair of face‐to‐face semicircular split‐ring resonators (SSRRs) was utilized to improve the impedance bandwidth of a planar patch antenna. By loading the SSRRs on the superstrate layer, their fundamental resonant modes could be capacitively induced by the radiation patch of the antenna underneath them, respectively. Benefitting from the ultra‐low mutual coupling level between the SSRRs even though their resonant modes are very close to each other, their resonant frequency ranges could be merged with the resonant frequency range from the fundamental mode of the radiation patch to produce a wide fractional impedance bandwidth as high as 4.2% (witnessing 5.16 times enhancement compared with that of a standard patch antenna), even with such a low profile (only 0.052λ0 height). Moreover, the experimental results, which are in good agreement with the simulation values, demonstrated its stable and excellent radiation characteristics, including strict broadside main beams with high polarization purity and large front‐to‐back ratios over the entire operational bandwidth. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:180–186, 2017

A novel ultra‐wideband metamaterial antenna using chessboard‐shaped patch

ABSTRACTA novel ultra‐wideband (UWB) antenna with chessboard‐shaped patch is successfully designed by employing planar patterned metamaterial in this paper. The metamaterial antenna has two layers, a novel chessboard‐shaped patch on the top layer and a planar metallic ground carved grid patterned gaps on the bottom layer. This novel antenna has a fractional impedance bandwidth of 71%, which is far more than that of a corresponding conventional patch antenna. Its radiation efficiency is higher than 88% within its operating frequency range 3.5∼7.9GHz and a maximum radiation efficiency of 96% has been achieved. Its gain is varied from 2.7 to 6.9dBi within its operating bandwidth. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:3008–3012, 2016

Planar endfire circularly polarized antenna using concentric annular sector complementary dipoles

A novel planar endfire circularly polarized (CP) antenna is presented and explored by using concentric annular sector complementary dipoles. The antenna is composed of a semicircular disk radiator operating at TM11 mode and a concentric annular sector dipole operating at one-half wavelength mode. A set of closed-form formulas is derived to reveal the operation principle and employed to determine the geometrical parameters of the proposed CP antenna. The design approach is both numerically and experimentally validated. Good agreement between the theoretical, numerical and experimental results has demonstrated its endfire radiation beam in parallel with its plane. The fractional impedance bandwidth for |S11| < −10 dB is up to 6.45%, and axial ratio (AR) bandwidth of less than 3 dB is up to 14.43% in fraction, in addition to its simple geometry with only seven design parameters.

Experimentally Validated, Planar, Wideband, Electrically Small, Monopole Filtennas Based on Capacitively Loaded Loop Resonators

Two planar efficient wideband electrically small monopole filtennas are presented. The first one directly evolved from a common planar capacitively loaded loop (CLL)-based filter. This filtenna possesses a flat realized gain response within the operational band and good band-edge selectivity. The second filtenna consists of a driven element augmented with a CLL structure and with slots etched into its ground plane. It expands the fractional impedance bandwidth of the first case from 6.28% up to 7.9%. It too has a gain response that remains flat over its operational bandwidth and even higher band-edge selectivity. Both filtennas are electrically small: $ka . The experimental results, which are in good agreement with their simulated values, demonstrate that both filtennas exhibit excellent impedance matching, high radiation efficiency, flat gain response, and steep skirts at both band edges, as well as producing monopole radiation patterns that are uniform and nearly omnidirectional in their H-planes.

Wideband hollow‐cavity substrate integrated waveguide stacked patch antenna for millimeter‐wave application

ABSTRACTThis letter proposes a wideband substrate integrated waveguide (SIW) stacked patch antenna for millimeter‐wave application. The proposed antenna is composed of strip‐line, coupling slot, hollow‐cavity, and stacked patches. Four near‐resonant‐frequency bands can be generated simultaneously to achieve 36% measured fractional impedance bandwidth from 26.5 to 38.2 GHz with the reference of |S11| less than −10 dB, and also with high linear polarization purity. A prototype of the antenna is fabricated and tested to verify the design concept. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2429–2433, 2016