###### Abstract
The synthesis technique uses Chebyshev transfer functions and impedance inverters [46; 47], which are realized by means of suitably centered, distributed, and sized metallic pins along the groove area of the GGW. Bandpass response is realized by combining this rigorous low-pass synthesis technique with the high-pass characteristics (quasi-TE\({}_{10}\) mode) of the GGW. The proposed design technique and the behavior of the pins inserted in this wideband GGW filter differ from the pin-based bandpass filter solutions proposed in [33; 34; 42; 43]. The metallic pins employed in [33; 34] act as couplings between the resonant cavities realized in the periodic structures (PMC). A modal analysis [33] and then a technique using space mapping and coupling matrix [34] were applied to design these bandpass filters. In [42], the metallic pins are periodically inserted along the groove area of the GGW filter and work as resonators or couplings. With this last structure [42], it is possible to achieve bandpass filters of different narrow fractional bandwidths (\(FBWs\)). However, the technique proposed in this work [42] does not allow us to accurately define the return loss (\(RL\)) and the bandwidth (\(BW\)) of the GGW bandpass filter. In [43], the pins act as resonators in an evanescent GGW section. With this structure, it is difficult to achieve large input couplings and, therefore, it is impossible to obtain a wide bandwidth (\(FBW>10\%\)). The slow wave solution presented in [45] allows the design of GGW bandpass filters with different bandwidths, using the cut-off frequency of the GGW and band-stop effect of the quasi-periodic transverse corrugations inside the GGW. However, this method requires a large number of corrugations to achieve a high level of rejection in the out-of-band region, which makes it difficult to determine the upper edge of the bandwidth and increases the size of the filter. Regarding manufacturing, this slow wave solution and the stepped impedance structure proposed in this work are more robust against tolerance than the bandpass filters using high Q-factors resonant elements. The structures that result from this design method are suitable not only for prototype manufacturing using a computer numerical control (CNC) machining technique, but they can also be fabricated with an emerging 3D printing technique [36; 41; 48], thus providing a new class of low-cost and low-weight components for communications systems. In this work, a compact fifth-order wideband Chebyshev bandpass filter in GGW technology is proposed for the first time. The design of this filter with a bandwidth \(BW=3.7\) GHz (\(FBW=36.4\%\)) and return loss \(RL=20\) dB is described in Section 2. Section 3 is focused on the fabrication of three prototypes of this filter by means of a CNC milling machine and a stereolithography-based 3D printer to make a comparison between both fabrication techniques. The surfaces of two resin-based 3D prototypes were metallized using a silver vacuum thermal evaporation technique and a conductive paint spray coating system. The electromagnetic (EM) simulations and measurements of the three manufactured filter prototypes are presented and discussed in Section 4. In addition, the frequency response performance and size of these filters are compared with other bandpass filters in GGW technology. Finally, conclusions are presented in Section 5.