The design and advantages of a novel light emitting diode (LED) bandwidth extension technique, based on the adoption of negative impedance converters (NICs), are discussed in the context of visible light communication systems. The design principles of the proposed negative impedance converter are introduced, with analytical derivations of the impedance frequency behaviour and the circuit performance frequency limitations. A two-transistor circuit is designed to generate a negative capacitance over the range −3 to −5 nF and is experimentally demonstrated, using discrete transistors, passive elements and commercially available LED constructed on a PCB, with frequencies up to 50 MHz. NIC design considerations necessary to obtain optimum LED bandwidth extension are discussed and outlined. Measurements demonstrate advantageously the optically lossless nature of the proposed solution and that, unlike traditional passive equalization or pre-distortion based bandwidth extension techniques, substantial improvement in the LED bandwidth, of up to 400 % can be obtained without compromising the output optical power.

中文翻译：

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负阻抗转换器在光发射机带宽扩展中的应用

在可见光通信系统的背景下，讨论了一种基于采用负阻抗转换器（NIC）的新型发光二极管（LED）带宽扩展技术的设计和优点。介绍了所提出的负阻抗转换器的设计原理，并对阻抗频率特性和电路性能频率限制进行了分析推导。设计了一个双晶体管电路，以产生−3至-5 nF范围内的负电容，并使用分立晶体管，无源元件和在PCB上构建的市售LED进行了实验演示，频率高达50 MHz。讨论并概述了获得最佳LED带宽扩展所需的NIC设计注意事项。