Compact planar folded monopole antenna with coupling mechanism for Quad ISM band, GNSS and UMTS applications

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This study presents a compact meandered type monopole antenna improved with coupling mechanisms to increase the number of allocated frequency bands in consideration. The proposed antenna includes a meandered (folded) conductor structure. Two straight conductors placed at the end of the meandered part bring Industrial, Scientific and Medical (ISM) bands at the upper UHF band with coupling mechanism, and one stub-like conductor inserted at the input of the meandered region gives another ISM band at the higher frequency. The antenna works at four popular ISM frequency bands of 433, 866, 915 MHz and 2.4 GHz, which cover several wireless applications such as M-bus, M2M, IoT, LoRa, RFID, Wi-Fi and Bluetooth. Along with the optimized dimensions of meandered and straight conductor parts, the proper arrangement of the dimensions related with coplanar feed part additionally provides upper Global Navigation Satellite System (GNSS) band, which includes upper bands of GPS, GLONASS, Galileo applications, and almost full coverage of 3G/UMTS -2100/IMT-2000 band. The described antenna has compact structure with about 0.125λ0by 0.046λ0at the lowest frequency, reasonable gain and omnidirectional radiation pattern characteristics.