Beam Steering Technique For Half Width Microstrip Leaky Wave Antenna

• Main Author: Mohsen, Mowafak Khadom
• Format: Thesis
• Language: English; English
• Published: 2019
• Subjects: T Technology (General); TK Electrical engineering. Electronics Nuclear engineering
• Online Access: http://eprints.utem.edu.my/id/eprint/24519/; https://plh.utem.edu.my/cgi-bin/koha/opac-detail.pl?biblionumber=117148

The main beam of a uniform Leaky wave antenna (LWA) steers between near broadside at low frequencies and near endfire at high frequencies. However, it has been found extremely difficult to achieve a broadside beam from a uniform LWA. Consequently, this limitation of uniform LWAs to radiate towards broadside has attracted interest from the research community. In this research, presents a new design of the uniform half-width microstrip leaky-wave antenna (HW-MLWA) array to achieve high radiation in the broadside direction. The proposed design comprises the two elements of HW-MLWA placed at straight line, and this array is fed by a single probe in the center of two elements. The proposed antenna is designed, fabricated, and validated. The measured impedance bandwidth is 10.75% (4.4 – 4.9) GHz, and the maximum measured gain at broadside is 10.02 dBi. A Modify technique to enhance impedance bandwidth of single layer (HW–MLWA) with continuous main beam scanning to increase scanning range in automotive radar. The enhancement is carried out by etching four circular slots on the radiation element. The wide main beam scanning is between +12o to +70o when operation frequency sweeping between 4.3 to 6.5 GHz. The measured impedance bandwidth of 49.9% (4.28 GHz to 7.13 GHz) with peak gain 10.31 dBi at 5 GHz. Finally, this research presents a new half–width microstrip leaky wave antenna (HW–MLWA), which can electronically control its beam at a fixed frequency using a double-gap capacitor with diodes, resulting in better impedance matching and small variation gain while scanning in altimeter radar to measure altitude of ground. The elementary building blocks of this antenna are HW–MLWA and seven control unit cells (CUCs). A reconfigurable CUC is created by combining two triangle patches as double–gap capacitors with two diodes as a switch to connect the patches with the ground plane. Control switches is used to achieve backward–to–forward beam scanning at a certain frequency, a gap capacitor in each patch cell is independently disconnected or connected by using a PIN diode switch. The reactance profile at the free edge of the microstrip is modified when the state of the patch cell is changed, which in turn, shifts the main beam direction. The proposed antenna prototype has the capability to scan the main beam forward between (+28° to +67°) and backward between (−27° to −66°) at 4.2 GHz. Furthermore, a periodic HW–MLWA array is presented. It can electronically control its beam at fixed frequency using a double gap capacitor with diodes and has good impedance matching and very small variation gain while scanning. When the state of the patch cell is changed, the reactance profile is altered at the free edge of the microstrip that caused the direction of the main beam to change. This proposed antenna prototype can scan the main beam between +22° to +63° at 4.2 GHz, and the antenna has a measured peak gain of 12.72 dBi at 4.2 GHz. The gain variation while scanning is 1.12 dB. This design is suitable to mount at the bottom of the flying aircraft, unmanned aerial vehicle UAV’s and other flying objects to measure altitude from the ground surface.