Design, simulation, and fabrication of broadband coaxial matched loads for the frequency range from 0 to 110 GHz

Abstract

Combining a theory for reflection-free termination of coaxial lines together with a novel manufacturing method results in 1-mm coaxial matched loads with an excellent absorption behavior over the frequency range from 0 to 110 GHz. Three different electromagnetic (EM) simulation approaches verify the capability of these matched loads to achieve reflection coefficients smaller than 243 dB over the entire frequency range. Matched loads with a maximum reflection coefficient of only 232 dB have been produced. An excellent performance was achieved by exponentially tapering the outer conductor over the region of a coaxial ceramic substrate coated by a thin-film resistance and by compensation for EM wave propagation inside the resistive coating.

Design, Simulation, and Fabrication of a 500 kV Ultrawideband Coaxial Matched Load and Its Connectors for Fast Transient Pulse Measurement Systems

“…Theoretically, to obtain reflection-free performance of the load, as demonstrated by Harris [46], the characteristic impedance of the coaxial line enclosing the resistor at any cross section must be equal to the load resistance beyond that cross section. Considering R 0 as the total resistance of the resistor and R(z) being the remaining ohmic resistance at a distance z from the short-circuited end of the resistor of total length l r , then R(z) can be written as follows [47]:…”

“…Equation ( 8) results in an exponential profile for the shielding, shown in the Figure 5. There are further improvements in the shielding conductor profile which have been published in the literature [47,48], such as tractorial terminations based on a tractrix profile, which is a steeper form of the exponential profile. However, for the resistive loads with a long resistive element for better insulation from flashovers, the difference in the results announced are not that overwhelming [47].…”

Matched loads using substrate integrated waveguide and shaped absorbing material for KA‐/Q‐band applications

“…Moreover, the resistive thin film (RTF) and carbon nanotubes have been utilized to enhance bandwidth of matched loads [3,4]. A NiCr alloys coaxial matched load even achieves a benchmark frequency range from dc to 110 GHz [5]. However, they require complex and costly nanofabrication or micromachining processes which are incompatible with the standard printed circuits board (PCB) process or complementary metal oxide semiconductor (CMOS) technology.…”