Abstract
A miniaturized antenna employing a negative index metamaterial with modified split-ring resonator (SRR) and capacitance-loaded strip (CLS) unit cells is presented for Ultra wideband (UWB) microwave imaging applications. Four left-handed (LH) metamaterial (MTM) unit cells are located along one axis of the antenna as the radiating element. Each left-handed metamaterial unit cell combines a modified split-ring resonator (SRR) with a capacitance-loaded strip (CLS) to obtain a design architecture that simultaneously exhibits both negative permittivity and negative permeability, which ensures a stable negative refractive index to improve the antenna performance for microwave imaging. The antenna structure, with dimension of 16 × 21 × 1.6 mm3, is printed on a low dielectric FR4 material with a slotted ground plane and a microstrip feed. The measured reflection coefficient demonstrates that this antenna attains 114.5% bandwidth covering the frequency band of 3.4–12.5 GHz for a voltage standing wave ratio of less than 2 with a maximum gain of 5.16 dBi at 10.15 GHz. There is a stable harmony between the simulated and measured results that indicate improved nearly omni-directional radiation characteristics within the operational frequency band. The stable surface current distribution, negative refractive index characteristic, considerable gain and radiation properties make this proposed negative index metamaterial antenna optimal for UWB microwave imaging applications.
Highlights
Microwave imaging systems have recently been used extensively for medical imaging applications.Usually, these imaging systems are constructed with a circular cylindrical array antenna and used to detect cancerous tissue
Metamaterial unit cells are installed on the radiating patch with a modified split-ring resonator (SRR) and a capacitance-loaded strip (CLS) to obtain design architecture that simultaneously exhibits both negative permittivity and negative permeability, a stable negative refractive index to improve the antenna performance for microwave imaging
A CLS is added to the modified SRR metamaterial unit cell, so that the resonance property is achieved within the operating Ultra wideband (UWB) range
Summary
Microwave imaging systems have recently been used extensively for medical imaging applications. The ultra-wideband signal provides good resolution and penetration properties The use of such microwave imaging systems has been proposed to detect breast cancer [1,2,3]. The antenna provides 3 dB directivity and −1 dBi maximum gain, along with radiation efficiency of 40% at 2.50 GHz. Several UWB antenna designs with different shapes, low distortion and compact size have been proposed for use in microwave imaging systems [27,28,29]. Metamaterial unit cells are installed on the radiating patch with a modified SRR and a CLS to obtain design architecture that simultaneously exhibits both negative permittivity and negative permeability, a stable negative refractive index to improve the antenna performance for microwave imaging
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