In this study, a novel design of circularly polarized antenna based on Koch fractal geometry is presented and experimentally investigated. Circular polarization and size reduction are achieved by placing two asymmetric Koch fractal geometries on x- and y-planes of the single-probe-feed square radiator. Further, to tune resonant frequency around the 911-MHz, four arrow-shaped slots are inserted in diagonal axes of the square radiator. It is perceived that compact size of the antenna can be achieved by increasing the overall size of the arrow-shaped slots and indentation angles of Koch fractal geometry. The antenna is fabricated on FR4 substrate with a size of $54 \times 54 \times 1.6\,\text{mm}^3$ ( $0.162 \lambda_{0}\times 0.162 \lambda_{0}\times 0.0048 \lambda_{0}$ at 900 MHz) and tested to validate the proposed design. The 3-dB axial-ratio bandwidth and impedance bandwidth of the proposed antenna design are found to be 8 MHz (907.0–915 MHz) and 37.0 MHz (891.0–928.0 MHz), respectively. The measured results confirm that the proposed design covers US radio-frequency identification (RFID) band (902–928 MHz) and can be used for RFID short-range reading applications.

Design of Koch Fractal Circularly Polarized Antenna for Handheld UHF RFID Reader Applications

A structure of a compact ultra-wideband monopole antenna has been presented. The antenna consists of a microstrip-fed rectangle radiator as well as a ground plane with a rectangle slit and an L-shaped stub. The critical factor in achieving a small size is a careful design procedure involving numerical optimisation of all geometry parameters of the antenna aiming at explicit size reduction while maintaining acceptable electrical performance. The final design exhibits dimensions of only 9.45 × 18.5 mm and a footprint of 175 mm
 2
. Experimental validation and comparisons with competitive designs are also provided.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/el.2015.4432

Compact UWB monopole antenna for internet of things applications

A novel coplanar waveguide-fed transparent antenna for ultrawideband applications with enhanced bandwidth is presented. In this design, different techniques have been used to broaden the bandwidth. The rectangular radiator of the antenna is equipped by the staircase technique to increase the overlapped resonant frequencies. Moreover, two major and minor symmetrical rectangular stubs are mounted on top of the quarter-circle slot ground by using a dual axis to significantly increase the bandwidth between 3.15 and 32 GHz for VSWR <; 2. AghT-8 transparent thin film is used in the design of the proposed antenna to obtain a very compact size and lightweight structure.

CPW-Fed Transparent Antenna for Extended Ultrawideband Applications

A very small coplanar waveguide (CPW)-fed rectangular slot antenna with dual band-notched characteristics for super ultrawideband (UWB) applications is proposed. This antenna consists of a rectangular slot, a beveled rectangular patch, two S-shaped slits cut in the ground plane and an elliptical ring slot (ERS) etched in the patch. The corners of a simple rectangular patch are beveled to improve the impedance bandwidth, especially at the middle frequencies of the band. In addition, a pair of semicircle slots is etched in the ground plane to enhance the bandwidth to more than 23 GHz. A pair of S-shaped slits connected to the rectangular slot, and an ERS cut in the beveled rectangular patch, is employed to create band-notched performances in WiMAX and WLAN spectrum, respectively. The proposed antenna has a very small size of $15 \times 15 \text{mm}^{2}$ , and therefore, it is one of the smallest UWB slot antennas that have been reported until now, and provide a very wide impedance bandwidth from 2.6 to more than 23 GHz for $\text{VSWR} with dual band-notched properties.

Very Small Dual Band-Notched Rectangular Slot Antenna With Enhanced Impedance Bandwidth

A comparative performance study of rectangular and circular shape microstrip patch antennas at an X band frequency is presented in this paper. The resonant frequency is chosen at 10 GHz which is suitable for a variety of wireless applications. CST Microwave Studio is used as the software environment to design and compare the performance of the antennas. It is found that the rectangular patch antenna shows about 3.0 dB higher return loss than the return loss of circular patch antenna. In addition, the rectangular patch antenna has an improved VSWR value of 1.18 than that of the circular patch with VSWR 1.27. However, circular patch antenna offers about 8% higher bandwidth and nearly 2.0dB less side lobe power than that of rectangular patch antenna.

Comparative study of rectangular and circular microstrip patch antennas in X band

A novel coplanar waveguide (CPW)-fed compact ultrawideband (UWB) microstrip antenna is proposed for ultrawideband applications. The proposed antenna posseses a method to minimize the monopole antenna by loading of inverted L-strip over the conventional monopole patch antenna to lower the height of the antenna. The ground was vertically extended toward two sides of the single radiator. Therefore, the large space around the radiator that is usually wasted can be effectively saved. The antenna is practically fabricated and simulated. Measured results show a good agreement with simulated results. The prototype with overall size of $25 \times 25 \times 1.6\ {\hbox{mm}}^3$ achieves good impedance matching, constant gain, stable radiation patterns, and constant group delay over an operating bandwidth of 2.6-13.04 GHz (10.44 GHz).

A CPW-Fed Compact UWB Microstrip Antenna

A novel single-feed arrowhead-shape slotted microstrip antenna for circular polarization (CP) is proposed. To achieve CP radiation and antenna size reduction, an arrowhead-shaped slot is embedded in the first quadrant along the diagonal axes of a square patch. Thus, the structure is asymmetric, and good-quality CP performance can be achieved by adjusting the size of the slot. The antenna is simulated and practically fabricated. Measured results confirm the validity of this design and show a good agreement with simulated results. The antenna generates CP radiation at 911 MHz with an overall size of 87 × 87 × 4.572 mm 3. The fabricated antenna shows an impedance bandwidth of 35.0 MHz (888.0-923.0 MHz) with 8.0 MHz (908.0-916.0 MHz) 3-dB axial-ratio bandwidth (ARBW).

Circularly Polarized Arrowhead-Shape Slotted Microstrip Antenna

Circularly polarized hexagonal ring microstrip patch antenna with asymmetrical feed and DGS

A CPW feed UWB microstrip antenna with dual band-notched characteristics for WiMAX (3.3–3.7 GHz) and WLAN (5.15–5.825 GHz) band rejection is proposed. The overall antenna size is 25 mm × 25 mm × 1.6 mm. By cutting a L-shape slot in the ground plane WLAN band can be restricted and a stub is used between the two inverted L-shape structure of patch for rejection of the WiMAX band. The measured results demonstrate that the proposed antenna has good omnidirectional radiation patterns with appreciable gain across the operating bands. The measured impedance bandwidth defined by VSWR < 2 of 11.7 GHz (2.7–14.4 GHz), with the two notched bands of 3.1–3.8, and 4.8–5.8 GHz, is obtained.

Design of dual band-notched UWB antenna

In this letter, a novel single-layer single-probefeed compact antenna is proposed for triband operation. In comparison to the previous triple band fractal antennas, the antenna dimension has a compact size of 25mmx25mm. Various iterations of the proposed fractal antenna are compared, and finally an optimized design is presented and fabricated. The proposed design is combination of minokwski and modified sierpinski carpet fractal patch antenna. The simulated and measured results show that the proposed fractal antenna can be used for WLAN/WiMAX applications.

Anil Kr Gautam

Papers

A CPW-Fed Compact UWB Microstrip Antenna

Circularly Polarized Arrowhead-Shape Slotted Microstrip Antenna

Circularly polarized hexagonal ring microstrip patch antenna with asymmetrical feed and DGS

Design of dual band-notched UWB antenna

Triple-band antenna combining Minkowski and modified Sierpinski fractal geometry