TERAHERTZ FILTERS USING A NEW DESIGN PROCEDURE Jorge A.M. Souza, 1 Marbey M. Mosso, 1 Glaucio L. Siqueira, 1 and Vanessa P.R. Magri 2 1 CETUC – Telecommunications Studies Center, Pontifical Catholic University, Rio de Janeiro, RJ, Brazil; Corresponding author: mitrione@cetuc.puc-rio.br 2 TET – Engineering School, Federal Fluminense University, Niter oi, RJ, Brazil Received 9 November 2016 ABSTRACT: This work presents a development of a filter and a wave- guide using substrate integrated to work at millimeter frequencies with a demonstration method to correct the dimensions of a substrate integrat- ed waveguides (SIWG). As a proof of concept, and using the method of dimensioning correction, another filter and a waveguide are created for working at frequencies up to 40 GHz, more precisely, at central frequen- cy of 28 GHz to perform with 5G applications. V C 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:1333–1337, 2017; View this article online at wileyonlinelibrary.com. DOI 10.1002/ mop.30534 Key words: millimeter band; SIWG; dimension correction 1. INTRODUCTION The development of Substrate Integrated Waveguides (SIWG) have been related and allow new perspectives for utilization to new frequencies band, including millimetric waves [1]. For a best result, the SIWG must be synthetized with metalized holes in the substrate [2]. Another use for the SIWG is the integration with lumped elements for substrate integrated circuits (SIC). The structures can be synthetized for planar structures aiming better loss characteristics and low cost fabrication [3]. This waveguide can be replaced from conventional waveguides with size reduction and costs [4]. And two or more lines of metalized holes are used for mark off the area compared to a rectangular wave- guide in TE 10 mode. The cutoff frequency is specified from dimen- sion “a” as well the substrate height “h”. An important factor that can be verified is that the substrate height must be smaller than the dimension “a”. The dimension “a” specifies the fundamental mode propagation constant. The metalized holes define the waveguide losses. Figure 1 presents the SIWG: This waveguide cannot be considered as an homogeneous rect- angular waveguide, but its behavior can be transformed in a rectan- gular waveguide. This waveguide is considered a band pass filter with cut off frequency defined as a TE 10 mode cut off frequency. Several waveguides and filters are developed, and among them, two examples are selected to be performed as proof of concept, until 40 GHz. The substrates used in this development are Silicon (Si) and Silicon Germanium (SiGe) at THz domain, and in the proof of concept, Rogers R5880 (with Dk 5 2.2) at 28 GHz for use at 5G applications. This paper is structured using this presentation: Section 2 introduce a new procedure to design the SIWG Filter and its waveguide, Section 3 shows the simulation and measured results when available for the SIWG Filter, Section 4 illustrates the future works and the comments for this work and Section 5 presents the bibliography used in this work. 2. A NEW DESIGN PROCEDURE FOR SIWG FILTER AND WAVEGUIDE DEVELOPMENT This development consists to obtain a SIWG Filter with four vias: two external holes with smaller radii located at kg 4 from microstrip lines and two inner holes with greater radii located at kg 2 from external holes. The distance between these inner holes is k g , which k g is the electric wavelength for any substrate. The minimum width for a SIWG is expressed by equation (1): a5 c 2  f TE10 (1) The electric length in any dielectric waveguide, is calculated using the equation (2): k g 5 k ffiffiffiffi  r p (2) Circular centralized holes are placed in the center of SIWG to obtain the correct bandwidth for signal transmission. This holes provide inductance and capacitance reactancies expressed by X L and X C respectively [5]. The equivalent circuit model can relate all reactancies with the characteristic impedance of the Wave- guide, the TE 20 mode propagation wavelength in the filter cen- tral frequency, the hole diameter (d) and the waveguide dimension for cutoff frequency of TE10 mode, accordingly equations (3) thru 6. The equivalent electric circuit of a circular centered hole is defined in the Figure 2: X L Z 0 : k g 2:a 5u 1 (3) X C Z 0 : k g 2:a 5u 2 (4) d a 5u 3 (5) k g a 5u 4 (6) The values of u 1 ; u 2 ; u 3 ; u 4 for each metallized via can be obtained from the filter central frequency. Considering a broad- band filter, only four vias are needed, because the higher quanti- ty of vias, the narrower is the filter. And using the four metallized vias method, we have two vias with high radii d 1 and the other two vias have small radii d 2 , the equivalent circuit is illustrated in Figure 3 where LT 1 thru LT 5 are the distancies between vias which can create the filter and are modeled as Figure 1 The SIWG Developed DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 59, No. 6, June 2017 1333