Constant Impedance Transmission Line with Leaky-Wave Radiation

This paper proposes a leaky-wave transmission line (TL) based on n = -1 space harmonic. Its main structure is a modulated parallel line. However, different from all other space harmonic leaky wave TLs (to date), this modulation introduces nearly no disturbance to the impedance of its transmission line. Therefore, it naturally has no open-stopband (OSB). Different from the other leaky-wave antenna (LWA) designs, where the OSB is generated first, then eliminated with additional structures, the proposed design has no OSB from the starting point. It has a special manufacturing process based on 3D-printing and copper tape. It also features high radiation gain, and ultra-wideband. The simulated result shows a peak realized gain of 10.6 dBi for broadside radiation. Measured return loss is mostly better than 10 dB within 6–18 GHz.