A tunable multiband folded printed quadrifilar helical antenna (FPQHA) is proposed. Creating slot on the arms of FPQHA is a simple approach for designing multiband helical antenna. Also varying width and length of the slot can cause to tune the interested frequency bands. The operating frequency ranges in L/S/C band that covers L1 GPS band and most of the commercial wireless communication systems, such as WLAN [IEEE 802.11 (2.4/3.6/5 GHz)], LTE and WiMAX (2.5/3.5 GHz).

In this paper, a miniaturized ultra-wideband antipodal tapered slot antenna with exponential strip arms is presented. Two exponential arms with designed equations are optimized to reduce the lower edge cut-off frequency of the impedance bandwidth from 1480 MHz to 720 MHz, resulting in antenna miniaturization by 51%. This approach also improves antenna bandwidth without compromising the radiation characteristics. The dimension of the proposed antenna structure including the feeding line and transition is 158 × 125 × 1 mm3. The results show that a peak gain more than 1 dBi is achieved all over the impedance bandwidth (0.72–17 GHz), which is an improvement to what have been reported for antipodal tapered slot and Vivaldi antennas with similar size.

A novel single‐feed wide band planar single layer circularly polarised (CP) slot antenna is presented. This low cost slot antenna consists of an L‐shaped feeding stub with metamaterial inspired complementary split ring resonator (MICSRR) and a wide 45° rotated symmetric square aperture. Broadband impedance and CP radiation bandwidth (BW) is achieved by using a novel artificial exciting stub with defecting CSRRs on it. By controlling the excitation phase of L‐shaped stub, a desirable circular polarisation can be generated and both impedance and CP BWs are considerably increased by up to 89%. The operating frequency ranges in S/C band about 1.5 octaves from 2.4–6.22GHz that covers most of the commercial wireless communication systems, such as WLAN (IEEE 802.11 (2.4/3.6/4.9/5/5.9GHz)), LTE and WiMAX (2.5/3.5/5.8GHz). The measured BWs of 3‐dB axial ratio and voltage standing wave ratio  < 2 are around 91% (2.4–6.4GHz) and 89% (2.4–6.22GHz), respectively. The measured boresight gain is less than 6 dBic over the CP BW.

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