Concurrent Mode-Division Multiplexed Half-Mode Substrate-Integrated Waveguide Link With Three Independent Data Channels

This article introduces a three-channel half-mode substrate-integrated waveguide (HMSIW) link. The link achieves three independent channels by stacking two HMSIWs vertically, with one of them utilizing both the fundamental and the first higher-order modes (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$TE_{0.50}$</tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$TE_{1.50}$</tex-math></inline-formula>). Methods for selective excitation of both modes with good overall cross-modal isolation are introduced and presented. Furthermore, real-time eye-diagram measurements of the link using a pseudo-random binary sequence (PRBS) and on-off keying (OOK) modulation are presented in addition to a full MATLAB simulation model of the link showing its performance under quadrature amplitude modulation (QAM). The measured 10-dB return loss (RL) BW of the channels are more than 4 GHz (12–16 GHz) for the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$TE_{0.50}$</tex-math></inline-formula> modes along the two HMSIWs, and 3.6 GHz of the first higher-order mode <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$TE_{1.50}$</tex-math></inline-formula> (12.1–15.7 GHz), corresponding to a concurrent bandwidth of 3.6 GHz with more than 15 dB of isolation between the channels. To the best of our knowledge, this is the first demonstration of a three-channel link using HMSIWs. The structure is fabricated and measurements agree well with the electromagnetic simulations.