Hadia Elhenawy

Enhancement of Microstrip Monopole Antenna Bandwidth by Using EBG Structures

A novel compact design for UWB planar monopole antenna is presented in this letter. The basis for achieving the UWB operation is through using semicircular microstrip monopole antenna with circular modified ground plane. This shape produces bandwidth ranging from 3 to 35 GHz with discontinuities in certain bands from 7 to 10 GHz and from 12.5 to 17.5 GHz. The antenna size is around 27% of the size of a conventional rectangular microstrip patch antenna. Electromagnetic band-gap (EBG) structures are used for further improve the antenna performance. It is shown that by embedding metallo-EBG structure (MEBG) such as circular and square patches, it is possible to eliminate ripples in the operating band and still achieve a reduction in the antenna size to more than 60% from conventional patch. The final antenna design provides an impedance bandwidth (S11 <-10 dB) of more than 33 GHz with averaged radiation efficiency of 73%-74% and antenna gain of 6.5 dBi.

Ultrawide Bandwidth 2

Four types of EBG structures are proposed and used in the design of a patch antenna array to improve the bandwidth, gain and reduce the overall array size. The four ground plane designs for the 2 × 2 microstrip patch antenna array (MPAA) are; spiral artificial magnetic conductor (SAMC) ground plane, an SAMC embedded with a large spiral artificial magnetic conductor (LSAMC), an SAMC embedded with small spiral patch cells (SSAMC), and an SAMC embedded with small spiral mushroom-type electromagnetic band-gap patches (ESEBG). Simulation results show that each configuration has its advantages and limitations. For example while LSAMC provides better response in the array size reduction and improved bandwidth, SSAMC provides better response in reflection phase and hence higher gain. The ESEBG design provides better antenna gain and bandwidth. The achieved bandwidth of the 2 × 2 array antenna extends from 0.5 GHz to 20 GHz with 85% reduction in array size compared with conventional array with normal ground plane. The array gain increased from 6.5 to 10.5 dBi and the radiation patterns are all improved when using EBG structures.

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The design and characterization of a compact ultrawideband (UWB) antenna is presented in this letter. The bases for achieving such an UWB operation are through using semicircular microstrip monopole antenna and introducing a metamaterial as an artificial magnetic conductor (AMC). The AMC reduced antenna size, enhanced antenna gain and bandwidth, and decreased the cross-polarization effect. A spiral artificial magnetic conductor (SAMC) is used as a ground plane with one and four arms to further improve the antenna performance. Furthermore, to reduce surface wave propagation and decrease bandwidth discontinuity, holes surrounding the antenna structure are drilled in the substrate. The new antenna provides an impedance bandwidth of more than 35 GHz with S11 < -10 ± 0.5 dB. The SAMC antenna has a wide frequency range for practical applications ranging from all required wireless communication bands, i.e., GSM 900 MHz, ISM band, Bluetooth, wireless LAN and S-band, to new medical applications. Details of the proposed antenna design are described, and experimental results are presented.

2 Microstrip Patch Array Antenna Using Electromagnetic Band-Gap Structure (EBG)

Microstrip patch antennas with inset feed have been studied extensively over the past two decades because of its practical advantage when used in mobile wireless systems. The length of MPA, however, is comparable to a half wavelength with single resonant frequency and bandwidth around 2%. In this paper, we describe a novel approach to reduce the antenna size and provide multiband operation. Electromagnetic bandgap (EBG) structure is used as defect ground plane structure to reduce size and achieve multiband resonant frequencies. Two cells of spiral-shaped defected ground structure (DGS) with each cell composed of spiral with four arms are used in the design. Simulation results show that more than 50% reduction in size was achieved as well as fives resonant frequencies resulted from the new design. One resonance resulted from the fundamental patch antenna while the other four resulted from each spiral arms. Acceptable E-plane and H-plane radiation patterns and an antenna gain of about 4dB are achieved.

Ultrawide Bandwidth Umbrella-Shaped Microstrip Monopole Antenna Using Spiral Artificial Magnetic Conductor (SAMC)

As wireless communications applications continue to require more and more bandwidth, there has been continued increase in demand for ultra-wide bandwidth antennas. Planar monopole antennas are generally suitable for mobile applications and hence we researched avenues to improve the bandwidth of this antenna structure. First part in this paper describes the design of novel compact and ultra-wide bandwidth (UWB) antenna. The basis for achieving the UWB operation is through using semicircular microstrip monopole antenna with modified ground plane as semi circular patch like umbrella shape. This shape produced bandwidth ranging from 2 to 30 GHz with discontinuities from 7GHz to 10GHz, from 12.5 GHz to 17.5GHz and with a size reduction around 50% from conventional rectangular shape patch. Second part of this paper is focused on further improving in the antenna performance by using metamaterial structures such as Metallo-electromagnetic band gap structure (MEBG) and spiral artificial magnetic conductors (SAMC). The final novel antenna design provides an impedance bandwidth (S11≪-10dB) of more than 29GHz corresponding to over 900% increase over the original bandwidth.

Multiband and miniaturized inset feed microstrip patch antenna using multiple spiral-shaped defect ground structure (DGS)

This paper presents microstrip array antenna integrated with novel shapes of 2D-electromagnetic band-gap structure (2D- EBG). Three difierent shapes of 2D-EBG are used for harmonic suppression, optimizing the current distribution on the patches and decreasing the mutual coupling between array elements. As a result, the performance of the antenna array is improved. The three novel shapes of 2D-EBG presented are star, H shaped and I shaped slots. Simulated and measured results verify the improved performance of the array antenna compared to the array antenna without EBG as well as antenna array with conventional EBG shapes. The harmonic suppression and re∞ection coe-cients are improved by about 18dB. Minimum mutual coupling is less than i20dB, and the antenna size is reduced by 15% compared to the original size.

Enhancement of ultra-wide bandwidth of microstrip monopole antenna by using metamaterial structures

This paper presents an investigation of both electromagnetic wave model and equivalent circuit model for microstrip patch antenna (MPA) with rectangular defected ground plane structure (RDGS). The objective of the proposed design is to reduce antenna size from Wi-Fi wireless band to the Bluetooth band. The first part of the paper describes the electromagnetic wave modeling using the High Frequency Structure Simulator (HFSS®) software to study the effect of RDGS on antenna resonant frequency. An optimization tool together with curve fitting were then used to formulate an approximate equation that describes the identified trends from the simulations. Second part is focused on estimating, using the Advanced Designing System (ADS) software the parameters of an equivalent circuit model for MPA with RDGS. The developed equivalent circuit consists of lumped elements for both MPA and RDGS structure and also include representation of the electrical and the magnetic coupling between rectangular grounded slot and MPA. Optimum values of the equivalent circuit elements were determined, and the overall simulation results were confirmed experimentally.

MICROSTRIP ARRAY ANTENNA WITH NEW 2D-ELECTROMAGNETIC BAND GAP STRUCTURE SHAPES TO REDUCE HARMONICS AND MUTUAL COUPLING

A new miniaturized ultra-wideband bandpass fllter with embedded reconflgurable multiband frequency notch function was designed and implemented by embedding all the passive components into a printed circuit board with a high dielectric constant. The proposed fllter consists of compact 2U-shaped DGS resonators shunt connected to parallel coupled lines to achieved frequency notch. To tune the notched band, suitable capacitor elements within the inner/outer U-DGS and RF PIN diode within the outer U-DGS are integrated. A curve fltting formula is derived to show the efiect of the capacitor value on the center frequency of the notched band, which is decreased by 56.7%. These capacitors improved the quality factor and have the efiect of reducing the fllter size by 72% as compared to other fllters. The RF PIN diode in the outer U-DGS acts as a switch to exhibit a band notch covering the bandwidth of the WLAN for IEEE 802.11a/h at 5.5GHz and RFID ISO 18000 series pars 5 in microwave (MW) which is set at 5.8GHz, 6.1GHz and 6.8GHz, and the other bands. RF PIN diodes control the notched band and raises it from 5.25GHz to 6.85GHz (27%) or remove the band notched according to its positions. In order to validate the feasibility of the proposed structure, UWB BPF with center frequency of 6.85GHz is designed, fabricated, and measured. The fllter has passband from 3.2GHz to 10.7GHz and notched band designed to generate stop band from 5.25 to 6.85GHz, and the two transmission zeros are observable at 2GHz and 12.5GHz, respectively by measurement. This paper shows the

Electromagnetic analyses and an equivalent circuit model of microstrip patch antenna with rectangular defected ground plane

This paper proposes a new fuzzy constant false alarm processor (FCFAR) for radar MTD systems. The proposed amplitude processor decides the fixed threshold value for the CFAR using fuzzy logic controller according three input variables. First input is the fast threshold from fifty serially averaged range cells. The second is the slow threshold from concatenated 500 averaged range cells. The third input is the signal to noise ratio at the RF stage of the radar system. The proposed processor is simulated under Matlab program environment on 1 million range cells data in additive white Gaussian noise (AWGN) with non-homogeneous background clutter and from 5 to 30 dB signal to noise ratio (S/N). The results show the superiority of the proposed FCFAR than the traditional systems used during the last decade.

DESIGN OF RECONFIGURABLE MINIATURIZED UWB- BPF WITH TUNED NOTCHED BAND

A simple multiband of multiple-input-multiple-output (MIMO) antenna with low mutual coupling is proposed for laptop application. The proposed antenna consists of two planar inverted F-antenna (PIFA) elements. Each element consists of two trapezoidal shaped slots within the radiating plate and uniplanar electromagnetic band gap within the ground plane. EBG ground plane is used for obtaining lower cut off frequency, increase the gain, and larger bandwidth. The proposed uniplanar shape is easy to fabricate without the use of vias or other kinds of vertical connections. The proposed antenna is designed to cover two narrow bands namely GSM 1.8 GHz, upper WLAN 5.2 GHz and a wideband from 2.4 GHz to 4 GHz. Moreover, mutual coupling reduction by using EBG is studied, where two integrated antenna elements can operate simultaneously. Results show that the MIMO antenna has mutual coupling of less than -35 dB at 5.2 GHz, and less than -15 dB through other frequencies. The average envelope correlation coefficient is less than 0.3 over the operating frequencies. All these features enable the proposed antenna to be a good candidate for MIMO laptop applications.