A Compact In-Line Waveguide-to-Microstrip Transition in the Q-Band for Radio Astronomy Applications

Abstract

Abstract:A microstrip-to-waveguide transition has been realized for radio astronomy applications, designed to operate in the Q-band (33-50 GHz). As part of an array radio frequency (RF) receiver, the main requirement of such a transition is the reduction of transverse space occupation for the integration in the entire receiver chain, so an in-line configuration has been developed. Moreover, the high frequency band implies that an easy fabrication is a critical requirement if a good match between the two guiding structures is to be obtained in the desired band (with a relative bandwidth of 40%). The combination of CAD software and an optimization tool allows the device to achieve a good return loss over the entire band.

An In-Line Coaxial-to-Waveguide Transition for Q-Band Single-Feed-Per-Beam Antenna Systems

“…As a matter of fact, by introducing an offset in the pin position along the short side b with respect to the center ( Figure 2), and so approaching it to the WG upper wall, a large field is concentrated in the small gap g between the two aforementioned conductors. Such a field configuration is similar to a single-ridged waveguide (R-WG) whose ridge is centered in the long side with an height equal to the offset of the pin [33]. Moreover, the field lines in the pin section gather in the gap between the pin and the upper wall, and they are oriented parallel to the lines in the ridged area.…”

“…This paper proposes an in-line coaxial-to-waveguide transition with a compact geometry to obtain a good match over the whole Q-band (33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49)(50). The aim is to reach the desired matching (typically, at least a return loss (RL) > 20 dB in radioastronomy) without increasing the transverse occupation and limiting the additional components to the strictly necessary, in order to obtain a satisfactory accuracy in the design despite the small operating wavelengths involved.…”

“…The aim is to reach the desired matching (typically, at least a return loss (RL) > 20 dB in radioastronomy) without increasing the transverse occupation and limiting the additional components to the strictly necessary, in order to obtain a satisfactory accuracy in the design despite the small operating wavelengths involved. This is an alternative solution to the previous work which involved a microstrip as end-launcher [33]. The shift between a microstrip and a coaxial end-launcher leads to several improvements.…”

“…This dispersion is due both to a dispersivity of the dielectric constant and to the geometric dispersion of the microstrip [34]. The latter can be well modelled but only for "free space" microstrip, not in configurations as in [33]. On the other hand, the coaxial conductors have no geometrical dispersion, and the dielectric material dispersion is typically smaller than the dispersion of a microstrip slab [35].…”

Millimeter-wave Dual-Function Hollow Metal Waveguide to Microstrip Transition and Bandpass Filter based on ENZ Metamaterial

“…To interconnect the hollow metal waveguide and microstrip in a compact form is of great interest for millimeter multichip modules and hybrid integrated circuits applications, as different functional components may use different types of host waveguides. Based on the tunneling effect, ENZ waveguide can interconnect the hollow metal waveguide and microstrip efficiently at selected frequency band, in spite of the significant impedance mismatch and geometry difference between these waveguides, making it an interesting alternative waveguide transition method to the other classic schemes using microstrip probe [33 -35], patch [36,37], fin line [38,39], and step matching [40,41]. using the ENZ waveguide centered at around 33 GHz.…”