Arnidza Ramli

Optical wireless front-end receiver design

Optical wireless or Free Space Optics (FSO) has received considerable attention as an alternative to existing Radio Frequency (RF) communication system. This is due to the growing demand for wireless broadband communications and congestion on bandwidth of RF spectrum. In optical wireless application, the performance of the receiver is significantly determines the overall performance of optical wireless link. Receiver is required to have large aperture. Accordingly, the detector is required to have a large detection area which produces high photodetector capacitance and limits the receiver bandwidth. In this paper, the front-end optical receiver designs especially for wireless application have been focused where a fundamental requirement is the achievement of wide dynamic range and broad bandwidth. Through a review on reported works, the bootstrapping technique is found effectively reduces the photodetector capacitance associated with the large area photodetector. Consequently, the overall bandwidth of the system can be improved.

Bandwidth Enhancement Technique using Series-Shunt Bootstrapping for Front-End Optical Wireless Receiver

The performance of receiver system for the optical wireless communication is greatly determined by the performance of the front-end. However, large detection area required in optical wireless application produces high detector capacitance hence limits the bandwidth performance of the system. Thus, techniques to reduce effective detector capacitance are required to increase the receiver sensitivity, bandwidth and noise performance. A lot of papers have been previously reported successful techniques to enhance the bandwidth by employing bootstrapping technique. This paper introduces a series-shunt bootstrapping technique which exploits a series-shunt positive capacitive feedback. The modeling of the circuit is done by utilizing MATLAB. This technique boosts the bandwidth up to 1.04 GHz.

Modeling of a Series-Shunt Bootstrapping Pre-amplifier Circuit for Free Space Optics

The signal level in an optical wireless receiver is weakest at the front end of the receiver due to the photodetector capacitance. Most of the papers have been previously reported successfully in bandwidth enhancement using bootstrapping technique. This paper introduces a series-shunt bootstrapping circuit which is boosted up the bandwidth to GHz. The modeling of the circuit exploits a series-shunt positive capacitive feedback. Feedback is applied to a buffered differential pair to obtain a bootstrap action. The result is only based on the modeling using MATLAB. Utilizing the dissimilar values of photodetector capacitance, the bandwidth does not alter to a great extent. Therefore, this circuit is suitable to implement in high noise environment especially in optical wireless link.

Transimpedance amplifier with automatic bandwidth compensation technique for large window optical front-end receiver

We present the transimpedance amplifier with an automatic bandwidth compensation technique for free space optics. The proposed topology includes a TIA which features a bandwidth control input and a replica bias circuit to sense the active device DC parameter variations. A photo detector model and the front-end structure, TIA with an automatic bandwidth compensation circuit have been simulated. The results show that the design minimizes the bandwidth spread when a variation parameter is considered.

A Wireless Utility Meter System: Design and Implementation

The conventional utility billing system suffers from the inefficiency of utility providers workforce deployment. Apart from the financial cost issue, unnecessary workforce deployment will result in an extensive period of utility meter reading and billing. The solution proposed in the authors Malaysian patents numbered PI2010002408 and PI20100022305 is the utilization of a wireless utility meter system for application of water meter specifically and other utility types, at large. The proposed wireless utility meter system makes use of an onsite utility usage monitoring and billing, that is capable of reducing the utility providers workforce deployment while serving as a necessary transient step towards a truly automatic monitoring and billing solution. Another advantage in the proposed semi-automatic wireless onsite meter reading is the elimination of unnecessary cost of maintaining the complicated fully automatic offsite wireless meter reading. The proposed wireless utility meter system is designed using SKXBee wireless modules. In the proposed design, consideration is also given to the utility usage database system. Indeed, in the near future, the proposed wireless utility meter design can be implemented as a transient step before the application of a fully automatic wireless meter solution becomes feasible in the third world countries.

Optical front-end receiver design for optical wireless communication system

This paper presents a bootstrapping technique that is applicable for various large window photodetectors by introducing a variable feedback capacitor to the front-end system. Two types of optical front-end receivers; Transimpedance amplifier (TIA) and Bootstrap transimpedance amplifier (BTA) were simulated and the performances of both architectures were compared. With the photodiode input capacitance compensation, the BTA improves the systems performance in which up to 670% increase was exhibited in the systems bandwidth. On the other hand, using the variable feedback capacitor in the circuit design, the fidelity of the system response was improved. This article also refers some recent patent on optical wireless receiver designs.

Terrestrial optical wireless communication propagation analysis considering Malaysia's weather condition

The reflection of sunlight by mirrors or known as the heliograph is an early method of optical wireless communication (OWC). Modern OWC was an offshoot of the development of laser technologies. Recently, OWC has expended to include terrestrial networks and deep space mission between points with a distance separation ranging from 100m at rates up to 10Gbps (Bouchet, O, 2006). Naturally, modern communication system reveals much higher data rates with better quality of service (QoS) compared to these ancient methods. There are many advantages of OWC which are important for a terrestrial system. In this work, a description and system performance characterization of the OWC are presented. Atmospheric effects (attenuation and turbulence), channel model and communication performance factors such as bit error rate (BER) and outage probability in weak turbulence condition were also studied and discussed. The OWC system are designed and simulated for performance characterization considering Subang terrestrial.

Shunt bootstrapping structure for large window optical front-end receiver for free space optic application

Free space optical link requires photodetector with large detection area. A large window photodetector usually suffers high photodiode capacitance resulting low bandwidth. In this work, a shunt bootstrapping technique was proposed to improved the bandwidth.