Transition from Microstrip Line to Ridge Empty Substrate Integrated Waveguide Based on the Equations of the Superellipse

Abstract

In recent years, multiple technologies have been proposed with the aim of combining the characteristics of traditional planar and non-planar transmission lines. The first and most popular of these technologies is the Substrate Integrated Waveguide (SIW), where rows of metallic vias are mechanized in a printed circuit board (PCB). These vias, together with the top and bottom metal layers of the PCB, form a channel for the propagation of the electromagnetic fields, similar to that of a rectangular waveguide, but through a dielectric body, which increases the losses. To reduce these losses, the empty substrate integrated waveguide (ESIW) was recently proposed. In the ESIW, the dielectric is removed from the substrate, and this results in better performance (low profile and easy manufacturing as in SIW, but lower losses and better quality factor for resonators). Recently, to increase the operational bandwidth (monomode propagation) of the ESIW, the ridge ESIW (RESIW) and a transition from RESIW to microstrip line was proposed. In this work, a new and improved wideband transition from microstrip line (MS) to RESIW, with a dielectric taper based on the equations of the superellipse, is proposed. The new wideband transition presents simulated return losses in a back-to-back transition greater than 20 dB in an 87% fractional bandwidth, while in the previous transition the fractional bandwidth was 82%. This is an increment of 5%. In addition, the transition presents simulated return losses greater than 26 dB in an 84% fractional bandwidth. For validation purposes, a back-to-back configuration of the new transition was successfully manufactured and measured. The measured return loss is better than 14 dB with an insertion loss lower than 1 dB over the whole band.

Manufacturing Methods Based on Planar Circuits

“…Procedures requiring more than one soldering phase Some prototypes, for example, RESIW or DRESIW devices [16], may need to be welded in two or more phases. To make possible a welding process divided into two or more phases, the methods described previously can be combined together.…”

Passive Planar Microwave Devices

“…Among the investigated parameters, the antenna distance was found to be the most important parameter for improving the accuracy of both RCP and BCP. Finally, Herraiz et al [12] proposed a new wideband transition from the microstrip line (MS) to ridge empty substrate integrated waveguide (RESIW), with a dielectric taper based on the equations of the superellipse. The new wideband transition presents simulated return losses in a back-to-back transition greater than 20 dB in an 87% fractional bandwidth, while in the previous transition, the fractional bandwidth was 82%, which supposes an increase of 5%.…”

Microstrip to Double Ridge Empty Substrate Integrated Waveguide Transitions Based on Exponential and Superelliptical Dielectric Taper

“…The superellipse equations are not new in the microwave filed, and they were used for defining impedance matching networks in planar and rectangular technologies [19]. However, it was not until recently that it has been used to match two different technologies, as validated with a transition from microstrip to SRESIW in [16]. A superellipse [20] is a general curve with a single control parameter N .…”

“…Table 4 provides initial values for the design parameters of the transitions. The expressions for the initial values of a c , b c , w sell are extracted from [16], and l sell is extracted from [10]. As in the previous transition, λ g refers to the wavelength in the widened section of DRESIW of width a + 2b c .…”

“…The SRESIW was first proposed in [14]. However, it was not until years later that microstrip to SRESIW transitions were proposed, designed, and manufactured [15], [16]. These transitions present a fractional bandwidth of around 80%.…”