Comprehensive Analysis of a Bridged-T Pre-Equalizer Circuit for High-Speed Visible Light Communications

Siti Hajar Ab Aziz; Norhanis Aida Mohd Nor; Suriza Ahmad Zabidi

doi:10.31436/iiumej.v26i1.3255

Authors

Siti Hajar Ab Aziz University of Kuala Lumpur https://orcid.org/0000-0002-0494-969X
Norhanis Aida Mohd Nor International Islamic University Malaysia https://orcid.org/0000-0001-8536-5567
Suriza Ahmad Zabidi International Islamic University Malaysia https://orcid.org/0000-0002-1584-2636

DOI:

https://doi.org/10.31436/iiumej.v26i1.3255

Keywords:

Bridged-T circuit, Pre-equalizer, VLC, Scattering parameter, Two-port networks, ADS/MATLAB

Abstract

This paper presents a comprehensive analysis of a bridged-T equalizer circuit (BTEC) designed for a high-speed visible light communications (VLC) system. The circuit is proposed to overcome the bandwidth limitation of light-emitting diodes (LEDs) in the VLC system. The advanced design system (ADS) and MATLAB were integrated to analyze the behavior of the BTEC in terms of transfer functions and scattering parameters S11, S12, S21, and S22. The results indicate a good correlation between the two tools, with the center frequency being 786 MHz. The 3-dB lower and upper cut-off frequencies are 501 MHz and 1.23 GHz, respectively. The impedance point is at magnitude 1 and 0 phase degrees on the Smith chart. This precise point ensures optimal matching to 50 ? of source and load impedance. This simulation proves that the bridged-T pre-equalizer circuit is a symmetric and reciprocal network since S11 = S22 and S12 = S21. This work combines the computational capabilities of MATLAB with the circuit simulation capabilities of ADS, which satisfied the pre-equalizer circuit experimental stage.

ABSTRAK: Kertas kerja ini membentangkan analisis komprehensif bagi litar penyama T terjepit (BTEC) yang direka untuk sistem komunikasi cahaya nampak (VLC) berkelajuan tinggi. Litar ini dicadangkan untuk mengatasi had lebar jalur diod pemancar cahaya (LED) dalam sistem VLC. Sistem reka bentuk lanjutan (ADS) dan MATLAB telah disepadukan untuk menganalisis kelakuan BTEC dari segi fungsi pemindahan dan parameter serakan S11, S12, S21, dan S22. Keputusan menunjukkan korelasi yang baik antara kedua-dua alat, dengan frekuensi tengah ialah 786 MHz. Frekuensi potong bawah dan atas 3-dB ialah 501 MHz dan 1.23 GHz, masing-masing. Titik impedans adalah pada magnitud 1 dan 0 darjah fasa pada carta Smith. Titik tepat ini memastikan padanan optimum kepada 50 ? sumber dan galangan beban. Dalam simulasi ini, terbukti bahawa litar pra-penyamaan bridged-T adalah rangkaian simetri dan timbal balik sejak S11 = S22 dan S12 = S21. Kerja ini menggabungkan keupayaan pengiraan MATLAB dengan keupayaan simulasi litar ADS, yang memenuhi peringkat percubaan litar pra-penyamaan.

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