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SD1003 Advisor: Ben Braaten Team members: Casey Brossart Chris Pickett Matt Lommen Matt Sandbakken

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Summary Problem Requirements Design Impedance Matching Testing Power requirements Budget

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The Problem Charging a battery without being hooked into the grid.

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Why Wireless? Environmental Considerations Mobility Energy Costs

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Requirements Design a wireless battery charger Operate at 2.4 GHz Create a DC output voltage Uses high frequency laminate

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Block Diagram

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Voltage Doubler Uses configuration capacitors and Diodes Rectifies AC input to DC output

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Voltage Doubler Workings

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Schematic

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Lommens Microstrip Calculator Allows all active components to be mounted on the top side of the board Susceptible to cross-talk and unintentional radiation Calculates W or Z 0 given H and ε r Important to match the characteristic impedance of microstrip line to that of the source. Maximum power is delivered Improves signal-to-noise ratio Reduces amplitude and phase errors

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Initial Design

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Impedance Matching (Tuning) Z0Z0 ZLZL Matching Network

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Impedance Matching (Tuning) Normalizing the impedance: z L =Z L /Z 0 We assumed Z L =15-j150 We assumed Z 0 =50 z L =0.3-j3

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Impedance Matching (Tuning) Note that z L lies outside the 1+jx circle on the Smith Chart. Because of this, the following configuration for the matching network should be used.

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Impedance Matching (Tuning) X=±[R L (Z 0 -R L )]^(1/2)-X L B=±{[ (Z 0 -R L )/R L ]^(1/2)}/R L Two solutions possible for both B and X Positive X implies an inductor Negative X implies a capacitor Positive B implies a capacitor Negative B implies an inductor

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Impedance Matching (Tuning) For positive values jX=jωL jB=jωC For negative values jX-j/ωC jB=-j/ωL

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Test Board

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Trial and Error 4.5pF (4 - 1pF + 0.5pF in parallel)10pF0.5pF pF (4 - 1pF + 0.5pF in parallel)10pF5pF pF (4 - 1pF + 0.5pF in parallel)5pF pF (4 - 1pF + 0.5pF in parallel)5pF20pF open5pF20pF open5pF10pF open5pF open5pF2pF open10pF open20pF10pF pF10pFopen open10pF5pF nH10pF5pF nH5pF nH2pF5pF nH3pF5pF PI Network Center FreqdB Trace to GND (doubler side)Trace in SeriesTrace to GND (antenna side)(GHz)

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Trial and Error Results

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Power Requirements

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Attenuation (dBm)Attenuation (mW)Potential across LED (V) 2.4 GHz2.45 GHz Using the 11nH - 3pF - 5pF matching network

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Power Requirements Friis Transmission Equation

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Project Status

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Tasks remaining Refine impedance matching techniques Verify operation with antenna installed Charge a AAA battery Explore flexible substrates Timeline Want to be charging a battery within the first 4 weeks of next semester Flexible substrates are a secondary objective

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Budget PartQuantityRetail Cost Expected Cost Total CostNotes AAA Rechargable NiMH Batteries 2 packs (8 batteries) $10.88/pac k $21.76 Walmart; Energizer AA Rechargable NiMH Batteries 2 packs (8 batteries) $14.84/pac k $29.68 Walmart; Battery Biz Total $51.44 PartQuantity Retail Cost Expected Cost Total CostNotes 2.4 GHz wireless- G router 1$41.99 Ebay Capacitors (.1pF to 150pF) 750 (various sizes) $83.65 Digikey/ Mouser Inductors (11nH)20$6.01 Digikey RF Detector 4 VBR 0.3 pF 100$0.68 $68.00 Mouser Mica 2.4 GHz SMD Antenna 5$11.20 $56.00 Antenova Rogers duroid sheet$0 Provided by Ben Total $ Remaining Purchases

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Summary Two PCBs created Initial prototype including antenna Test board including SMA input Impedance matching completed Need to refine this process Need to incorporate antenna

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