Ultrawide-Angle and Compact Leaky-Wave Antenna Based on Complex Periodic Structure

A compact antenna with the characteristic of wide-angle frequency beam scanning based on complex periodic structure is proposed. A double gradient spoof surface plasmon polaritons structure is added to the standard microstrip line for reducing the antenna size. The miniaturization of the proposed antenna is analyzed with the method of dispersion curves and electric field distribution. Periodic changes of the groove depth and trapezoidal gradient structure increase the beam scanning angle from backward to forward and suppress the open stopband effect. The proposed structure is printed on the FR-4 substrate with a compact size of 0.23λ
₀
× 3.71λ
₀
(λ
₀
is the wavelength of the lowest operating frequency), and has a working frequency band from 12.5 to 42.5 GHz for |
S
₁₁
| < −10 dB. Meanwhile, a wide beam-scanning angle of 142° (−52° to +90°) and an average gain of 7.9 dBi are obtained by simulation and measurement. The proposed leaky-wave antenna has a potential application in wireless communication system due to its small size, broad frequency band, wide beam scanning angle and low cost.