Broadband high efficiency active integrated antenna

Qin, Yi (2007) Broadband high efficiency active integrated antenna. Doctoral thesis, Northumbria University.

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Abstract

Active integrated antenna (MA) is a very popular topic of research during recent decades. This is mostly due to its advantages, such as compact size, multiple functions and low cost, etc. The MA system can be regarded as an active microwave circuit which the output or input port is free space instead of a conventional 50-ohm interface. The major drawbacks of the conventional MA include narrow bandwidth, low efficiency, etc. An experimental investigation on broadband slot-coupled antenna is carried out, which results an impedance bandwidth of 50 % is achieved by both a ring slot- coupled and square ring slot-coupled patch antenna. An improved design technique for broadband class-E power amplifier (PA) design, based on the theoretical analysis done by Mader [2], is introduced to calculate the circuit parameters. The technique is applied to a RF microwave class-E power amplifier design (PA) that results a bandwidth of 12 % power added efficiency (PAE) greater than 60 % is achieved. The aim of this work is to design broadband high efficiency linearly polarized (LP) and circularly polarized (CP) MA and arrays that will be useful for mobile communication system. The MA does not need conventional matching network between the amplifier and the antenna, because the antenna serves as both a harmonics-tuning network and a radiator. A novel high efficiency broadband LP MA is demonstrated using a ring slot-coupled patch antenna with a class-E PA. It exhibits a PAE over 50 % within a 14.6 % bandwidth. For the first time, a high efficiency broadband CP MA is designed using a class-E PA integrated with a broadband CP antenna. The CP AIA achieves a PAE over 50 % within a 14 % bandwidth. The axial ratio of the CP MA is below 3 dB over a 9 % bandwidth. For further improve the performance, a novel L-shaped slot-coupled broadband CP MA is employed in a 2x2 array. The array consists of four sequentially rotated broadband CP antenna elements with an element spacing of half a free space wavelength. The antenna was designed to operate in the 3G band around 2 GHz. A bandwidth of 22.7 % PAE greater than 50 % is achieved together with a peak PAE of 71.35%. A bandwidth of 27 % axial ratio below 3 dB is resulted.

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