General Guided-Wave Impedance-Matching Networks with Waveguide-Metamaterial Elements

Wangyu Sun, Xu Qin, Shuyu Wang, and Yue Li

Phys. Rev. Applied 18, 034070 – Published 26 September 2022

Abstract

A plasmonic based nanocircuit transplants the lumped property of classical electronic circuits to optical frequencies, providing a circuit paradigm for optics and photonics. To broaden the material and frequency selections, the concept of a waveguide metamaterial is applied to design lumped elements by utilizing the waveguide’s structural dispersion to emulate the natural material’s dispersion. Here, as an important application of the physics of waveguide metamaterials, a general type of impedance-matching network directly integrated with a waveguide is investigated for various matching occasions of guided waves, outperforming the classical ones using waveguide membranes. Three representative matching examples are analyzed to validate the feasibility, namely, transmission discontinuities, active power amplifiers, and antennas. The numerical and experimental results confirm the impedance-matching applications of the waveguide metamaterial and suggest the potential merits of low loss and low crosstalk for the proposed waveguide-integrated matching networks in terahertz integrated-circuit designs.

Received 3 June 2022
Revised 26 July 2022
Accepted 17 August 2022

DOI:https://doi.org/10.1103/PhysRevApplied.18.034070

Physics Subject Headings (PhySH)

Impedance Integrated optics Optoelectronics Permittivity Plasmonics

Metamaterials Waveguides

Terahertz techniques

Condensed Matter, Materials & Applied PhysicsAtomic, Molecular & Optical

Authors & Affiliations

Wangyu Sun ¹, Xu Qin ¹, Shuyu Wang¹, and Yue Li ^1,2,*

¹Department of Electronic Engineering, Tsinghua University, Beijing 100084, China
²National Research Center for Information Science and Technology, Beijing 100084, China

^*lyee@tsinghua.edu.cn

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Vol. 18, Iss. 3 — September 2022

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Images

Figure 1
General concept of a general guide-wave matching network with WG-MTM elements. (a) Sketch of the general matching network, which is introduced to match a load of arbitrary complex impedance with a source of arbitrary real impedance. (b) Network is developed by inserting some dielectric layers (i.e., red parts) inside the waveguide. These layers are given the name WG-MTM elements and can exhibit effective parallel or series reactance, jX. (c) Equivalent-circuit models of networks comprising single, double, triple, etc. WG-MTM elements. (d) Potential applications of impedance matching.
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Figure 2
Impedance properties of waveguide metamaterial. (a) Scheme of the WG-MTM element within a metallic rectangular waveguide. (b) Effective capacitor and inductor model of the WG-MTM elements. (c)–(f) Comparisons between theoretical and simulated parallel reactance (C_P or L_P) of WG-MTM elements. Effective capacitor, i.e., $ε_{E}^{eff} > 0$ , (c) C_P vs $ε_{E}^{eff}$ , and (d) C_P vs a. Effective inductor, i.e., $ε_{E}^{eff} < 0$ , (e) L_P vs $ε_{E}^{eff}$ and (f) L_P vs a.
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Figure 3
Performance comparisons between waveguide metamaterial and classical metallic membranes. Scheme of the matching network with (a) capacitive waveguide metallic membranes or (b) capacitive WG-MTM element. (c) Reflection coefficients of (a),(b). Scheme of the matching network with (d) inductive waveguide metallic membranes or (e) inductive WG-MTM element. (f) Reflection coefficients of (d),(e).
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Figure 4
Waveguide-metamaterial matching networks for transmission discontinuities. (a) Conceptual sketch of the network to match a waveguide with E-plane step (change in height). Distributions of electric field magnitude at f_p when the waveguide (b) contains or (c) does not contain the WG-MTM elements. (d) Simulated reflection coefficients when it is unmatched and matched. (e) Conceptual sketch of the network to match a waveguide with H-plane step (change in width). Distributions of electric field magnitude at f_p when the waveguide (f) contains or (g) does not contain the WG-MTM elements. (h) Simulated reflection coefficients when it is unmatched and matched.
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Figure 5
Waveguide-metamaterial matching networks for the active power amplifier. (a) Sketch of the waveguide-integrated power amplifier, containing (b) input-matching network, (c) transistor with bias circuits, and (d) output-matching network. Matching network is composed of a single WG-MTM element integrated with the waveguide transmission line. (e)–(h) Performance comparisons before and after the proposed matching networks are inserted. (e) Reflection coefficient, (f) gain, (g) output power, and (h) PAE.
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Figure 6
Waveguide-metamaterial matching network for antenna. (a) Overall view of the structure to realize impedance matching for a cavity antenna by using a network with two WG-MTM elements. (b) Equivalent-circuit model of the proposed structure. (c) Photograph of the fabricated prototype of the cavity antenna with the proposed matching structure. Simulated and measured (d) reflection and (e) efficiency, when the cavity antenna is unmatched and matched.
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