Cryan, MJ

Sittakul, V

English

Lossless matching circuits are integrated into PhAlAs used in a 2.4 GHz wireless-over-fibre link. The system uses a 220 m in-building multi-mode-fibre and results show a greater than 10 dB improvement in signal strength and improved throughput.Lossless matching circuits are integrated into PhAlAs used in a 2.4 GHz wireless-over-fibre link. The system uses a 220 m in-building multi-mode-fibre and results show a greater than 10 dB improvement in signal strength and improved throughput

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Photonic active integrated antennas (PhAlAs) using lossless matching for 2.4-GHz wireless-over-fibre systems

Lossless matching circuits are integrated into PhAlAs used in a 2.4 GHz wireless-over-fibre link. The system uses a 220 m in-building multi-mode-fibre and results show a greater than 10 dB improvement in signal strength and improved throughput

                          Sittakul, V., & Cryan, M. J. (2008). Photonic active integrated antennas(PhAIAs) using lossless matching for 2.4-GHz wireless-over-fibre systems.In Conference on Lasers and Electro-Optics, 2008 and 2008 Conference onQuantum Electronics and Laser Science (CLEO/QELS). Optical Society ofAmerica.Link to publication record in Explore Bristol ResearchPDF-documentUniversity of Bristol - Explore Bristol ResearchGeneral rightsThis document is made available in accordance with publisher policies. Please cite only the publishedversion using the reference above. Full terms of use are available:http://www.bristol.ac.uk/pure/about/ebr-terms.htmlTake down policyExplore Bristol Research is a digital archive and the intention is that deposited content should not beremoved. However, if you believe that this version of the work breaches copyright law please contactopen-access@bristol.ac.uk and include the following information in your message:• Your contact details• Bibliographic details for the item, including a URL• An outline of the nature of the complaintOn receipt of your message the Open Access Team will immediately investigate your claim, make aninitial judgement of the validity of the claim and, where appropriate, withdraw the item in questionfrom public view.Photonic Active Integrated Antennas (PhAIAs) Using Lossless Matching For 2.4-GHz Wireless-over-Fibre Systems  V.Sittakul and M.J.Cryan Department of Electrical and Electronic Engineering, University of Bristol, Bristol, BS8 1UB, UK  Author e-mail address: m.cryan@bristol.ac.uk   Abstract: Lossless matching circuits are integrated into PhAIAs used in a 2.4GHz wireless-over-fibre link. The system uses a 220m in-building multi-mode-fibre and results show a greater than 10dB improvement in signal strength and improved throughput. 2008 Optical Society of America  OCIS codes: (350.4010) Microwaves; (250.7260) Vertical cavity surface emitting lasers.  1. Introduction  Recently, the concept of Photonic Active Integrated Antennas (PhAIAs), where optical devices and antennas are integrated into one low cost circuit has been studied [1]. This allows photonic devices to be easily impedance matched to the non-radiating edge of the antenna where the input impedance varies from a few ohms up to 100’s of ohms. Results show that a link using PhAIAs can achieve acceptable throughput and reasonable signal strength and linearity performance. The links use direct modulation employing a VCSEL which has an input impedance, Zin= 37+j0 Ω at 2.4GHz and this can be easily matched by connecting the VCSEL close to the centre of the non-radiating edge. However, the photodiode (PD), used for direct detection, is more capacitive in nature having Zin= 10-j100Ω at 2.4GHz and this cannot be easily matched using the antenna’s range of input impedances.  One solution is shown in [2] whereby a lossless matching network is used. This paper shows what is believed to be the first example of integration of antenna, matching circuit and optical device in the same low cost module. The matching technique achieves much improved link gain performance across a narrow band which is sufficient for WiFi applications. A bidirectional link including matching circuits in both up and down link is implemented and tested and greater than 10dB improvement in signal strength is obtained.   2. Results  Figure 1(a) shows the complete PhAIA in front view and figure 1(b) shows a zoom in of the matching circuit. Single stub matching is used since this is sufficient for this narrowband application. The circuit is fabricated on low loss substrate with εr≈4 and thickness 0.33mm. This matching circuit along with microstrip carrier on which the PD is wire bonded is mounted on the back side of the 2.4 GHz antenna on FR4 substrate with εr≈4.5 and thickness 1.5mm.                                   (a)                                                                                     (b)  Fig. 1.  (a) Layout of the PhAIA with matched PD mounted on backside (b) Matching circuit at the back of the patch (Zoomed in)   PD 40 mm 3 mm Wire 16 mm   10 mm Microstrip Carrier Bias Circuit Matching circuit Microstrip  Patch Antenna Wire bond to ground Wire bond to antenna 0.64 mm         a633_1.pdf   © 2008 OSA / CLEO/QELS 2008       CThR2.pdf   978-1-55752-859-9/08/$25.00 ©2008 IEEEFigure 2 (right) shows a photograph of the PhAIA with PD in this setup. A low cost fixture, which can be freely adjusted in X-Y-Z directions, is used for aligning the Multi-Mode Fibre (MMF) to PD. The fully bi-directional link including matching circuits is shown in figure 2.          Fig. 2. Diagram of bi-directional link     In figure 2, the USB WiFi adapter (802.11g) is used to simulate an access point from which the WiFi signal can be tapped off. Here, the external antenna of the USB adapter is removed in order that the RF signal can be directly fed into coaxial cable. The power splitter is required to separate the uplink and downlink and the VCSELs and the PDs function as the modulators and demodulators respectively. The laptop is placed at a distance, d away from the patch antennas. Then, proprietary software provided by Provision Communications (www.provision-comm.com) a spin-out from the University of Bristol was used to measure the signal strength and the throughput of the link as a function of the distance, d.  -95-90-85-80-75-70-65-60-55-500 1 2 3 4 5 6 7 8Distance (m)Signal Strength (dBm)6mA (Matching)8mA (Matching)6mA (No matching)8mA (No matching)0200040006000800010000120000 1 2 3 4 5 6 7 8Distance (m)Throughput (kbps)6mA (Matching)8mA (Matching)6mA (No matching)8mA (No matching)                                Fig. 3. Signal Strength vs Distance at different                                    Fig. 4. Throughput vs Distance at different                                           VCSEL1 bias currents                                                                           VCSEL1 bias currents  Figures 3 and 4 show that a range of 8m can be obtained with acceptable data rate. It was not possible to obtain data at greater than 8m due to the room size limitation.  As can be seen in figure 3, the signal strength can be improved by greater than 10 dB when a matching circuit is used. Figure 4 shows that on average the throughput is also improved, it is believed that fading effects are making the differences less clear at certain distances. Further improvements in performance will be achieved when the splitter is replaced by a low cost, surface mount circulator.  3. Conclusion  The lossless matching technique is applied to a bi-directional WoF link using PhAIAs. The link is demonstrated over 220m of real in-building MMF. Experimental results show an improvement of greater than 10 dB in terms of signal strength and that the connection can be maintained over ranges of 8m without the use of RF amplification.  4. References [1]. V.Sittakul and M.J.Cryan, “A fully bidirectional 2.4 GHz Wireless-over-fibre system using Photonic Active Integrated Antennas (PhAIAs)”, IEEE Journal of Lightwave Technology, vol.25, No. 11, Nov 07. [2]. E. Ackerman et al, “A high-gain directly modulated L-band microwave optical link”, IEEE Microwave Theory Tech, 1990, pp. 153-155. Built-in Wi-iFi   adapter  Laser controller ILX Lightwave LDC-3724B Power splitter  VCSEL1 (TSB-8B12-000)     VCSEL2 (TSB-8B12-017)    Photodiode2  (TPD-8D12-006) Photodiode1  (TPD-8D12-006) USB Wi-Fi adapter (SENAL sub-362EXT)    Bias Tee1 In-building  220 MMF In-building  220 MMF   d PhAIAs Matching circuit Matching circuit      PhAIA with PD2  Matching circuit   Fixture  MMF        a633_1.pdf   © 2008 OSA / CLEO/QELS 2008       CThR2.pdf   

Ackerman et al, “A high gain directly modulated L band microwave optical link”,

Photonic active integrated antennas (PhAIAs) using lossless matching for 2.4-GHz wireless-over-fibre systems

https://research-information.bris.ac.uk/files/3019887/sittakul2_CLEO_2008.pdf

Photonic active integrated antennas (PhAIAs) using lossless matching for 2.4-GHz wireless-over-fibre systems

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