In this paper, the design of Log Periodic Fractal Koch Antennas (LPFKA) is proposed for Ultra High Frequency (UHF) band applications. The procedure to design the LPFKA with three different numbers of iterations in order to reduce the antenna size is discussed. The Computer Simulation Technology (CST) software has been used to analyze the performances of the designed antennas such as return loss, radiation patterns, current distribution and gain. The antennas have been fabricated using FR4 laminate board with wet etching technique. Using fractal Koch technique, the size of the antenna can be reduced up to 27% when the series iteration is applied to the antennas without degrading the overall performances. Both simulated and measured results are compared, analyzed and presented in this paper.

Abstract-This paper describes the design and analysis of a Microstrip Reflectarray Antenna (MRA) with Minkowski shape radiating element at frequency of 11 GHz. This structure has been analyzed and compared with the traditional reflectarray element (square element patch). It is found that this antenna array has lower sidelobe level (SLL) characteristic which is down to −25 dB. This MRA has maximum realized gain of 29.6 dB with half-power beamwidth (HPBW) of 3.7 • . The validation for the proposed MRA is done by comparing the simulated and measured E-plane radiation pattern. A very good agreement is found from the comparison between simulation and measurement.

Abstract-This paper presents the design, fabrication, and measurement of triple band metamaterial absorber at 8 GHz, 10 GHz and 12 GHz which are in the X-band frequency range. The unit cell of the metamaterial consists of three concentric copper rings at different radii, printed on 0.8 mm thick FR4 substrate in order to obtain triple resonant frequencies. The highly symmetrical ring structure in nature makes this absorber insensitive to any polarization state of incident electromagnetic (EM) waves for normal incident waves. The proposed structure is capable to operate at wide variations angle of incident wave. The simulated result shows that the triple-band metamaterial absorber achieves high absorbance for normal incident electromagnetic waves of 97.33%, 91.84% and 90.08% at 8 GHz, 10 GHz and 12 GHz, respectively, when subjected to normal incident electromagnetic. With metamaterial absorber maintaining 50% of absorbance value, the corresponding full width half maximum (FWHM) are 5.61%, 2.90% and 2.33%. The operating angles in which the metamaterial structure can maintain 50% absorbance at TE mode and TM mode are 67 • and 64 • , respectively. The experimental result verifies that the absorber is well performed at three different resonant frequencies with absorbance greater than 80%.

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Abstract-In this paper, the designed of triple-band printed dipole antennas are incorporated with single-band artificial magnetic conductor (AMC). The single-band AMCs are designed to resonate at 0.92 GHz, 2.45 GHz and 5.8 GHz using TLC-32 dielectric substrate. The four important parameters in AMC high impedance surface (HIS) design are also described in this paper. By simulating a unit cell of the AMC structure using a transient solver in Computer Simulation Technology (CST) software, the characteristic of the AMC can be characterized. The AMC condition is characterized by the frequency or frequencies where the magnitude of the reflection coefficient is +1 and its phase is 0 • . It has high surface impedance (Z s ) and it reflects the external electromagnetic waves without the phase reversal. This characteristic of AMC enables the printed dipole to work properly when the antenna with AMC ground plane (GP) is directly attached to the metal object. The performances of the antenna with and without AMC structure as a ground plane to the antenna such as return loss, realized gain, radiation efficiency, radiation pattern and directivity are studied. Reported results show that the performances of the antenna are improved. Hence, the designed dipole tag antenna can be used for metal object identifications when the AMC structure is introduced as a ground to the antenna. The properties of the antenna are also remained well when the size of metal plate attached to them is increased.

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Abstract-A wideband antenna with band notch function using electromagnetic bandgap (EBG) structure is proposed. The antenna is capable of reconfiguring up to three band notch operation. Three EBGs are aligned underneath the feed line of the wideband antenna. The transmission lines over EBGs unit cells perform as a band stop filter. A switch is placed on each of the EBG structure, which enables the reconfigurable band stop operation. The simulated and measured reflection coefficients, together with the radiation patterns, are shown to demonstrate the performance of the antenna.