Compact Wideband Groove Gap Waveguide Bandpass Filters Manufactured with Printing and CNC Milling Techniques

Abstract

<p>This paper presents for the first time a compact wideband bandpass filter in groove gap waveguide (GGW) technology. The structure is obtained by including metallic pins along the central part of the GGW bottom plate according to an <em>n</em>-order Chebyshev stepped impedance synthesis method. The bandpass response is achieved by combining the high-pass characteristic of the GGW and the low-pass behavior of the metallic pins, which act as impedance inverters. This simple structure together with the rigorous design technique allow reducing the manufacturing complexity for the realization of high-performance filters. These capabilities are verified by designing a fifth-order GGW Chebyshev bandpass filter in the frequency range of the WR-75 standard with a fractional bandwidth FBW = 37% and return loss <em>RL</em> = 20 dB, and by implementing it using computer numerical control (CNC) machining and three-dimensional (3-D) printing techniques. Three prototypes have been manufactured: one using a CNC milling machine and two others by means of a stereolithography-based 3-D printer and a photopolymer resin. One of the two resin-based prototypes has been metallized from a silver vacuum thermal evaporation deposition technique, while for the other a spray coating system has been used. The three prototypes have shown a good agreement between the measured <em>S</em>-parameters and simulated results, and offer high-performance frequency responses and reduced size with respect to other GGW bandpass filters. These GGW bandpass filters could have a great potential for future emerging satellite communications systems. </p>