###### Abstract  
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 \(n\)-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 allows for a reduction in the manufacturing complexity for the realization of high-performance filters. These capabilities are verified by designing a fifth-order GGW Chebyshev bandpass filter with a bandwidth \(BW=3.7\) GHz and return loss \(RL=20\) dB in the frequency range of the WR-75 standard, and by implementing it using computer numerical control (CNC) machining and three-dimensional (3D) printing techniques. Three prototypes have been manufactured: one using a computer numerical control (CNC) milling machine and two others by means of a stereolithography-based 3D 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 and simulated \(S\)-parameters, with insertion losses better than \(IL=1.2\) dB. Reduced size and high-performance frequency responses with respect to other GGW bandpass filters were obtained. These wideband GGW filter prototypes could have a great potential for future emerging satellite communications systems. 3D printing bandpass filter; CNC machining; groove gap waveguide technology; lowpass filter; stepped impedance synthesis Article Compact Wideband Groove Gap Waveguide Bandpass Filters Manufactured with 3D Printing and CNC Milling Techniques  
[PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], Compact Wideband Groove Gap Waveguide Bandpass Filters Manufactured with 3D Printing and CNC Milling Techniques  
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[PERSON], A., [PERSON], [PERSON], Compact Wideband Groove Gap Waveguide Bandpass Filters Manufactured with 3D Printing and CNC Milling Techniques  
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[PERSON], A., [PERSON], A., Compact Wideband Groove Gap Waveguide Bandpass Filters Manufactured with 3D Printing and CNC Milling Techniques  
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[PERSON], A., [PERSON], [PERSON]. Recently, many modified SIW technologies have been proposed to improve insertion losses by partially or fully removing the dielectric substrate. The structures with the fully removed substrate are named empty and dielectricless SIWs (ESIW and DSIW) [8; 9], while those with the substrate partially eliminated are called air-filled, hollow, and modified SIWs (AFSIW, HSIW, and MSIW) [10; 11; 12]. Among these different structures, the empty substrate integrated waveguide (ESIW) has the lowest insertion loss and exhibits propagation characteristics analogous to the RW [13; 14]. Thus, several filters with small and large fractional bandwidths (_FBWs_) have been successfully implemented in ESIW technology in recent years to benefit from RW-like properties. The designs with _FBW_ lower than 4% are based on coupled cavities, resonators, and inductive posts [8; 15; 16; 17; 18; 19], while _FBWs_ higher than 10% are obtained by means of stepped impedances [19]. These ESIW filters have the advantages of planar and SIW technologies. However, they still present smaller quality factors than RW technology. In general, these filters are manufactured in two pieces with top and bottom parts. The ESIW and RW technologies have the same manufacturing drawback, since they require a good electrical contact between the top and bottom parts to avoid leaky waves. To overcome this problem in ESIW devices, an improved fabrication process was proposed in [20].