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In this letter, a triple-band zeroth-order-resonance (ZOR) epsilon-negative antenna using two series pseudo-open termination (P-OT) unit cells is proposed, for the case where shunt ZOR $({\boldsymbol{f}_{\boldsymbol{sh}}})$ is higher than series ZOR $({\boldsymbol{f}_{\boldsymbol{se}}})$ . Epsilon-negative transmission line (ENG TL) resonates a shunt ZOR, while the two series P-OT unit cells resonate two series ZORs ( ${\boldsymbol{f}_{\boldsymbol{se}}}$ and ${\boldsymbol{f}_{\boldsymbol{se1}}}$ ). Both the P-OT unit cells create different capacitances with the ENG TL to resonate ${\boldsymbol{f}_{\boldsymbol{se}}}$ and ${\boldsymbol{f}_{\boldsymbol{se}1}}$ . An electric field distribution vector is used to verify the resonances for zeroth order, and it is found that all the three resonances follow zeroth-order characteristics. The P-OT unit cells can be placed anywhere around the ENG TL to get proper matching. The measured resonances are 5.95 GHz $({\boldsymbol{f}_{\boldsymbol{se}1}})$ , 6.26 GHz $({\boldsymbol{f}_{\boldsymbol{se}}})$ , and 6.91 GHz $({\boldsymbol{f}_{\boldsymbol{sh}}})$ covering the satellite transmission frequencies of the C-band. The measured peak gains are 1.14, 1.39, and 2.19 dBi for $({\boldsymbol{f}_{\boldsymbol{se}1}})$ , ${\boldsymbol{f}_{\boldsymbol{se}}}$ , and ${\boldsymbol{f}_{\boldsymbol{sh}}}$ , respectively. ${\boldsymbol{f}_{\boldsymbol{se}1}}$ and ${\boldsymbol{f}_{\boldsymbol{se}}}$ have peak gain at the left and the right side of the $\varphi = {\text{0}^{\circ}}$ plane, respectively, while ${\boldsymbol{f}_{\boldsymbol{sh}}}$ has peak gains at both the right and the left sides of the $\varphi = {\text{0}^{\circ}}$ plane.

In this paper, a triple-band and dual-band zeroth order resonance (ZOR) epsilon negative antennas are proposed using two pseudo-open termination unit cells for the case where the shunt ZOR ( f sh ) is higher than the series ZOR ( f s e 1 ). The epsilon negative transmission line (ENG TL) resonates f sh while the series ZORs ( f s e 1 and f s e 2 ) are excited by the series capacitance of the two pseudo-open termination unit cells. If the series capacitances of the two pseudo-open termination unit cells are different then f s e 1 and f s e 2 are excited, else only f s e 1 is excited. f s e 1 and f s e 2 along with f sh results in triple-band ZOR antenna, while a single f s e 1 with f sh results in dual-band ZOR antenna. The pseudo-open termination unit cells can be placed anywhere around the ENG TL to get proper matching. All the resonances for both the antennas follow zeroth order characteristics which are verified using electric field vector. The measured peak gains of the triple-band ZOR antenna for f s e 2 , f s e 1 and f sh are 1.14 dBi, 1.39 dBi, and 2.19 dBi, respectively, with dipole mode for f sh . For dual-band ZOR antenna, the measured peak gains for f s e 1 is 1.4 dBi, and f sh is 2.05 dBi, with dipole mode for f s e 1 and f sh .

In this paper, a single-band omni-directionally circularly polarized Zeroth Order Resonance (ZOR) epsilon negative antenna is proposed. The above proposed antenna is designed for the case where the shunt ZOR is higher than series ZOR. Circular Polarization (CP) is achieved using Asymmetric Unit Cells (AUCs) which create orthogonal components. Zeroth order resonator inherently provides 90° phase shift between two orthogonal polarizations. Left Hand Circular Polarization (LHCP) is achieved by adding stubs with two 90° right bends to the unit cells. Electric field distribution is used to verify the excited resonance for zeroth order and it is found that it follows zeroth order characteristics. The simulated and the measured shunt ZOR are 4.21 GHz and 4.26 GHz, with fractional bandwidths of 1.3 % and 0.87 %, respectively. The simulated and measured LHCP gains are 2.05 dBic and 1.9 dBic, respectively.