The Smith Chart, Impedance Matching, and Transmission Line Circuits

AbstractThe paper demonstrates an effective technique to significantly enhance the bandwidth and radiation gain of an otherwise narrowband composite right/left-handed transmission-line (CRLH-TL) antenna using a non-Foster impedance matching circuit (NF-IMC) without affecting the antenna’s stability. This is achieved by using the negative reactance of the NF-IMC to counteract the input capacitance of the antenna. Series capacitance of the CRLH-TL unit-cell is created by etching a dielectric spiral slot inside a rectangular microstrip patch that is grounded through a spiraled microstrip inductance. The overall size of the antenna, including the NF-IMC at its lowest operating frequency is 0.335λ0 × 0.137λ0 × 0.003λ0, where λ0 is the free-space wavelength at 1.4 GHz. The performance of the antenna was verified through actual measurements. The stable bandwidth of the antenna for |S11|≤ − 18 dB is greater than 1 GHz (1.4–2.45 GHz), which is significantly wider than the CRLH-TL antenna without the proposed impedance matching circuit. In addition, with the proposed technique the measured radiation gain and efficiency of the antenna are increased on average by 3.2 dBi and 31.5% over the operating frequency band.

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Implementations of ACJ Technique in Different Four-Port Filter Networks

Handbook of Research on 5G Networks and Advancements in Computing, Electronics, and Electrical Engineering - Advances in Computer and Electrical Engineering ◽

10.4018/978-1-7998-6992-4.ch011 ◽

2021 ◽

pp. 281-299

Author(s):

Eugene A. Ogbodo

Keyword(s):

Transmission Line ◽

Impedance Matching ◽

Main Challenge ◽

The Common ◽

Coupled Resonator

This chapter proposes the use of asynchronously coupled-resonator junctions (ACJ) in the design of a multi-input multi-output (MIMO) filtering network and a masthead combiner (MHC). By employing the resonator junctions, miniaturised circuits are achieved without using any transmission-line-based impedance matching circuits. The main challenge in the designs is the control and implementation of the external couplings at the common ports of this all-resonator-based MIMO filtering network and MHC. Both devices are four ports-based with the MIMO filtering network operating at 1.8, 2.1, and 2.6 GHz, while the MHC operates at the two channels of 1.8 and 2.1 GHz. The demonstrated designs achieved fractional bandwidths of 1.764 GHz to 1.836 GHz, 2.058 GHz to 2.142 GHz, and 2.548 GHz to 2.652 GHz, respectively. Good agreements have been achieved between the measurements of the prototype devices and the simulations.

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