Ahmed Khidre

Circular Polarization Reconfigurable Wideband E-Shaped Patch Antenna for Wireless Applications

A polarization reconfigurable E-shaped patch antenna with wideband performance is proposed in this communication. The antenna is capable of switching its polarization from right hand circular polarization (RHCP) to left hand circular polarization (LHCP) and vice versa. Its structure is simple and consists of a single-layer single-feed E-shaped patch and two RF switches placed at appropriate locations in the slots. The design targets the WLAN IEEE 802.11 b/g frequency band (2.4-2.5 GHz) being used in various wireless communication systems. Full wave simulation is used for the antenna analysis, and a prototype of the antenna with an integrated DC biasing circuit has been fabricated and tested. Good agreement is obtained between simulated and measured results. The antenna exhibits a 7% effective bandwidth from 2.4 GHz to 2.57 GHz with a 8.7 dBic maximum gain. The antenna radiation symmetry is maintained upon switching between the two circular polarization modes.

Wide Band Dual-Beam U-Slot Microstrip Antenna

A wide band dual-beam microstrip antenna is proposed in this communication. Two radiation beams off broadside are obtained by operating the patch antenna at the higher order TM02 mode instead of the fundamental mode, which radiates a broadside beam. Broadening the antenna bandwidth is achieved by using the U-slot technique. Unlike previous work on the conventional U-slot microstrip antenna, the effect of the U-slot inclusion on the performance of a patch antenna operating at the TM02 mode is studied across the entire achieved bandwidth. The antenna analysis is carried out with the aid of full wave simulation, and an antenna prototype is fabricated and measured for validation. Good agreement between the simulated and measured results is observed. The antenna operating frequency range is 5.18-5.8 GHz with VSWR less than 2, which corresponds to 11.8% impedance bandwidth. It exhibits two radiation beams, directed at 35° and -33° with 7.92 dBi and 5.94 dBi realized gain, respectively at 5.5 GHz.

A Patch Antenna With a Varactor-Loaded Slot for Reconfigurable Dual-Band Operation

A new design approach for a microstrip patch antenna to achieve reconfigurable dual-band operation with tunable frequency ratio is introduced. The approach uses a lumped capacitor in the middle of a slotted patch antenna, which results in two resonant frequencies. The two resonant frequencies and their ratio are functions of the capacitance value. If a varactor with an appropriate biasing network is used, electronic tuning is realized by changing the applied DC voltage. To understand the dual-resonance behavior of the proposed antenna, an equivalent circuit model based on the transmission line theory of the antenna is established, considering the slot effect and the lumped capacitor. The results are verified with full wave simulation. Furthermore, measurements for fabricated antenna prototypes operating in 2-4.5 GHz are carried out for validation, and the performance shows a tunable frequency ratio from 1.45 to 1.93 with a capacitance range from 0.31 to 0.74 pF. It is worthwhile to point out that the radiation patterns are similar at both bands because both resonances are due to the fundamental TM01 mode.

Circularly Polarized Beam-Scanning Microstrip Antenna Using a Reconfigurable Parasitic Patch of Tunable Electrical Size

A reconfigurable microstrip antenna with a circularly polarized (CP) beam-scanning feature is proposed in this paper. Such feature is attained using a novel methodology that effectively tunes the electrical size of a patch antenna. The proposed antenna is a microstrip Yagi-Uda antenna consisting of two square patches. One patch is driven with two orthogonal feeds for CP operation, whereas the other patch is a parasitic one of tunable electrical size for beam scanning. The parasitic patch is loaded with a narrow square slot and four lumped varactors along with their dc biasing network to effectively tune its electrical size. Because the main beam direction is determined by the electrical size of the parasitic patch, electronic beam scanning is allowed by changing the capacitance value through the applied reverse dc biasing voltage. An antenna prototype has been fabricated for experimental validation. Operating at 2.45 GHz, the antenna performance shows a monotonic CP beam scanning that ranges from -36° to 3° with a 0.48-6.64 pF tuning capacitance. The achieved peak value for the realized gain is 8.1 dBic with 2.4-dB variation along the entire scanning range.

Reconfigurable microstrip antenna with tunable radiation beamwidth

This paper proposes a reconfigurable microstrip antenna with a tunable radiation beam. The design methodology uses two tunable size parasitic patches placed to the left and right of a probe-fed patch along its H-plane. Each parasitic patch is loaded with a lumped varactor as well as its biasing network, to effectively change its electrical size. Because the radiation beamwidth is controlled by the electrical size of the parasitic patches, electronic zooming is allowed by changing the capacitance value through the applied DC voltage. Both varactors are biased as unison, such that one DC control signal is required for the entire antenna. The antenna performance shows a dynamic control over the radiation beamwidth that ranges from 50° to 112° with capacitance tuning range of 0.5 pF to 2.5 pF.

Reconfigurable dual-band patch antenna using varactor-loaded slot

This paper introduces a new approach to design a microstrip patch antenna with reconfigurable dual band operation. Dual-band is achieved by the placement of a lumped capacitor on a slotted patch antenna, and the two resonant frequencies and their ratio are function of the capacitance value. Consequently, tuning of both frequencies is allowed by choosing proper capacitor value. If a varactor with an appropriate biasing network is used instead, electronic tuning is attained by changing the applied DC voltage. To understand the dual resonance behavior of the proposed antenna, a transmission line (TL) model with the wheeler incremental volume concept is established and validated with full wave simulation. The antenna shows 1.35-1.73 tunable frequency ratio with 0.5-1.1 pF capacitance. Moreover, the radiation patterns are similar at both bands.

Reconfigurable UWB printed monopole antenna with band rejection covering IEEE 802.11a/h

Reconfigurable microstrip UWB printed monopole antenna has been designed, analyzed, fabricated and measured with WLAN/Hyperlan2 band rejection characteristic. Band notch is realized by adding a parasitic patch in the back plan then it is cut into two parts which are connected by mean of two RF switches. The ON and OFF state of these switches enables and disables the band notch and hence reconfigurability is introduced. Simulation and experimental results are compared as well as simulated radiation pattern for the two states (ON/OFF) are presented. Also parametric study for optimizing different design parameters is investigated.

Reconfigurable microstrip Yagi-Uda antenna with a scannable circularly polarized beam

This paper proposes a novel reconfigurable microstrip antenna with circularly polarized beam scanning feature. It is based on a microstrip Yagi-Uda antenna of two square patches. One patch is driven with two orthogonal feeds and the other is a parasitic. The parasitic patch is loaded with four lumped varactors and a DC biasing network, to effectively change its electrical size. Because the main beam direction is determined by the electrical size of the parasitic patch, electronic beam scanning is allowed by changing the capacitance value through the applied DC voltage. Operating at 2.45 GHz, the antenna shows a beam scanning range from -36° to 32° with 2.3 dB gain variation across the entire scanning range and gain peak value of 8.1dBi.

Transmitarray antenna design using slot-type element

Many transmitarray antennas are designed with multilayer frequency selective surface type elements. The goal of this paper is to present a multiple conductor layers transmitarray antenna using slot-type element with no substrate material. A quaternary-layer transmitarray antenna using cross-slot elements has been designed, fabricated, and tested for 11.3 GHz operating frequency. The measured gain of the prototype transmitarray is 22.06 dB. It is observed that the oblique incident associated with the excitation and the polarization direction has a strong effect on the antenna radiation pattern and gain.

Reconfigurable microstrip antenna with two-dimensional scannable beam

This paper proposes a reconfigurable microstrip antenna with two-dimensional beam scanning feature. The antenna geometry consists of two parasitic patches placed along the E and H-planes of a probe-fed patch. Each parasitic patch is loaded with a lumped varactor and DC biasing network, to effectively change its electrical size. Because the main beam direction is determined by the electrical size of the parasitic patches, electronic beam scanning is allowed by changing the capacitance value through the applied DC voltage. Consequently, Two DC control signals are used for the two-dimensional beam scanning. Operating at 2.5 GHz, the antenna shows a beam scanning that ranges from 0°to 32° in the elevation plane and from 0° to 90° in the azimuth plane. The attained peak gain value is 8.51 dBi with 0.8 dB gain variation across the entire scanning range.