Compact shorted inverted‐L antenna with circular polarisation for RFID handheld reader

Abstract

Two shorted inverted-L radiating elements are located on the orthogonal corner of the square substrate and connected to each output port of a Wilkinson power divider. A shorted inverted-T strip is placed on the other corner of the square for a perturbing resonator to generate circularly-polarised (CP) radiation in the UHF band. Proper adjusting of the horizontal and vertical lengths of the inverted-T strip will differentiate two orthogonal linearly modes with 90°phase difference for a good CP radiation. Simulated and measured results indicate that the proposed structure can achieve circular-degree polarisation operation. A measured impedance bandwidth (VSWR ≤ 2) of about 16.4% (810-960 MHz) and a 3 dB axial-ratio (AR) bandwidth of about 4.4% (890-930 MHz) at 915 MHz were obtained.

Analysis of circular polarization antenna design trade‐offs using low‐cost EM‐driven multiobjective optimization

“…Although this approach is straightforward, it increases complexity and physical size of the structure which is due to the necessity of accommodating the circuitry required for achieving appropriate phase shift between the radiator ports . Compact dimensions and CP operation can be also achieved through modifications of antenna geometry using slots, stubs, ground plane perforations, or their combinations . However, such antennas are normally characterized by a narrow axial ratio (AR) bandwidth which limits their usefulness for modern communication systems.…”

“…The necessity of handling several criteria at the same time reveals multi‐objective nature of the problem. CP antenna design methods prevailing in the literature are unsuitable for explicit control of more than one criterion . Instead, they are oriented toward improvement of AR and/or reflection within the specified bandwidth, with other figures being a by‐product of the selected antenna topology .…”

“…[5][6][7] Compact dimensions and CP operation can be also achieved through modifications of antenna geometry using slots, stubs, ground plane perforations, or their combinations. [8][9][10] However, such antennas are normally characterized by a narrow axial ratio (AR) bandwidth which limits their usefulness for modern communication systems. Notwithstanding, in Ref.…”

“…CP antenna design methods prevailing in the literature are unsuitable for explicit control of more than one criterion. 6,10,11 Instead, they are oriented toward improvement of AR and/or reflection within the specified bandwidth, with other figures being a by-product of the selected antenna topology. 11 Furthermore, manual design based on parameter sweeps and visual inspection of the structure response remains a popular design choice.…”

Compact dual ports handheld RFID reader antenna with high isolation

“…Handheld RFID readers reported are most single port with various structures [1][2][3][4][5][6][7]. RFID system consists of a tag and reader.…”