Equivalent Circuit Model of High Power LEDs for VLC Systems

Li, Xicong; Ghassemlooy, Zabih; Zvánovec, Stanislav; Zhang, Min; Burton, Andrew

doi:10.1109/wacowc.2019.8770209

Cited by 22 publications

(32 citation statements)

References 21 publications

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“…The corresponding curve given in Fig. 2(b) is plotted with the same parameter A = SNR 0 • f 3dB as in (18) and is in a good agreement with the analysis. To conclude, for a VLC system with the first-order response, there always exists an optimum modulation bandwidth to achieve a maximum capacity under the condition of a limited transmit power and no power-loading.…”

Section: Higher Capacity Without Snr Penalties: Multi-carrier Modulationsupporting

confidence: 81%

“…Additionally, there exists an optimal point to achieve the largest capacity. Using (18) as the upper bound of C EQ (B mod ), the capacity is plotted as a function of B mod in Fig. 2(b) with f 3dB = 10MHz and SNR(f ) = 35 dB, 0 < f < f 3dB .…”

Section: Capacity Analysismentioning

confidence: 99%

“…When including a pre-equaliser at the transmitter, one must consider the impedance mismatch issue when driving the LED, which has a dynamic resistance of less than 5 at a high bias current level [18], with a standard 50 signal generator. Fig.…”

Section: Led Current Driver Designmentioning

confidence: 99%

“…The single carrier CAP requires a flat frequency response to obtain low BER, which is achievable within the pass-band of the LED. However, beyond an LED's 3-dB bandwidth, the LED has an attenuation rate of 20 dB per decade [18]. By increasing the number of sub-carriers, the frequency response in each band can be approximated to be flat, which eliminates the need for an equaliser.…”

Section: Multi-carrier Modulation Scheme: M-cap With Bit-loadingmentioning

confidence: 99%

“…The bridge-T structure, which was first introduced for copper telephone lines to deliver high-quality voice transmission [15], has a constant impedance [16], [17], thus facilitating impedance matching. Note that LEDs have a rather low impedance (few ohms including the parasitic resistance) when biased at high currents [18], and therefore cannot be directly connected to the bridge-T equaliser. In [14], both active pre-and post-EQs were used to increase the bandwidth from 12 to 233 MHz in order to transmit 550 Mb/s OOK data.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Should Analogue Pre-Equalisers be Avoided in VLC Systems?

Ghassemlooy

Zvánovec

et al. 2020

IEEE Photonics J.

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Visible light communication (VLC) systems are highly constrained by the limited 3-dB bandwidth of light-emitting diodes (LEDs). Analogue pre-equalisers have been proposed to extend the LED's bandwidth at the cost of reduced signal-to-noise ratio (SNR). Compared with the pre-equaliser, the multi-carrier modulation with bit-loading can efficiently use the spectrum beyond the LED's raw 3-dB bandwidth without incuring SNR penalties by employing multiple narrow quasi-flat sub-bands to eliminate the need for equalisation. In this work we show by means of theoretical and experimental investigation that VLC with multi-band carrierless amplitude and phase modulation with bit-loading can outperform VLC with analogue pre-equalisers.

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Section: Higher Capacity Without Snr Penalties: Multi-carrier Modulationsupporting

confidence: 81%

Section: Capacity Analysismentioning

confidence: 99%

Section: Led Current Driver Designmentioning

confidence: 99%

Section: Multi-carrier Modulation Scheme: M-cap With Bit-loadingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Should Analogue Pre-Equalisers be Avoided in VLC Systems?

Ghassemlooy

Zvánovec

et al. 2020

IEEE Photonics J.

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A miniaturized and low-energy subcutaneous optical telemetry module for neurotechnology

Truong

Nikpour

et al. 2023

J. Neural Eng.

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This study presents a proof-of-concept optical telemetry module that leverages a single light-emitting diode (LED) to transmit data at a high bit rate while consuming low power and occupying a minimal area. Our experiments showed that we could achieve 108 Mbit/s and 54 Mbit/s back telemetry data rates for tissue thicknesses of 3 mm and 8 mm, respectively. The proposed module is designed to be powered by near-field coupling and achieve bidirectional communication by low-speed downlink from near-field communication (NFC). It aims to minimize the size of the implant while providing reliable transmission that meets the requirements of high-speed wireless communication from a multi-electrode array neurotechnology implant outside the body. The power consumption of the module is 1.57 mW, including the power consumption of related circuits, resulting in an efficiency of 14.5 pJ/bit, at a tissue thickness of 3 mm and a data rate of 108 Mbit. The use of an optical lens, combined with tissue scattering effect and optimized emission angle, makes the module robust to misalignments of up to ±5 mm and ±15˚ between the implantable and external units. The LED in the implantable unit is only 0.98 x 0.98 x 0.6 mm3, and the testing module is composed of discrete components and laboratory instruments. This work aims to show how it is possible to strike a balance between a small, reliable, and high-bit-rate data uplink between a neural implant and its proximal, wirelessly connected external unit. This optical telemetry module has the potential to be integrated into a significantly miniaturized system through an application-specific integrated circuit (ASIC) and can support up to 1,000 channels of neural recordings, each sampled at 9 kSps with a 12-bit readout resolution.

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LED Systems Applications and LED Driver Topologies: A Review

et al. 2023

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High-power light-emitting diodes (LEDs) and high-brightness LEDs have revolutionized the lighting industry. The availability of cost-effective LEDs with high luminous flux, efficacy, and reliability has expanded their application to replace incandescent and fluorescent light sources. They have also enabled many new applications that were considered infeasible before, due to the inherent limitations of traditional sources of light. This survey provides a comprehensive overview of ac-and dc-supplied LED lighting systems and their applications, corresponding specifications and their similarities to/differences from regular power supplies. Restrictions imposed by LEDs characteristics, safety considerations, and dimmers are discussed. Also, LED driving approaches are categorized and their suitability for different applications is provided.

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Equivalent Circuit Model of High Power LEDs for VLC Systems

Cited by 22 publications

References 21 publications

Should Analogue Pre-Equalisers be Avoided in VLC Systems?

Should Analogue Pre-Equalisers be Avoided in VLC Systems?

A miniaturized and low-energy subcutaneous optical telemetry module for neurotechnology

LED Systems Applications and LED Driver Topologies: A Review

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