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

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

Summary Problem Requirements Design Impedance Matching Testing Power requirements Budget

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

Why Wireless? Environmental Considerations Mobility Energy Costs

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

Block Diagram

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

Voltage Doubler Workings

Schematic

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

Initial Design

Impedance Matching (Tuning) Z0Z0 ZLZL Matching Network

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

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.

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

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

Test Board

Trial and Error 4.5pF (4 - 1pF + 0.5pF in parallel)10pF0.5pF2.864-10.2 4.5pF (4 - 1pF + 0.5pF in parallel)10pF5pF2.75-6.67 4.5pF (4 - 1pF + 0.5pF in parallel)5pF 2.761-7.17 4.5pF (4 - 1pF + 0.5pF in parallel)5pF20pF2.747-8.67 open5pF20pF2.06-5.15 open5pF10pF2.114-7.54 open5pF 2.154-18.59 open5pF2pF1.648-4.01 open10pF 2.027-9.42 open20pF10pF1.999-9.49 5pF10pFopen2.63-11 open10pF5pF2.09-22.1 11nH10pF5pF2.1897-20.32 11nH5pF 2.26-32.1 11nH2pF5pF2.485-6.97 11nH3pF5pF2.4-14.1 PI Network Center FreqdB Trace to GND (doubler side)Trace in SeriesTrace to GND (antenna side)(GHz)

Trial and Error Results

Power Requirements

Attenuation (dBm)Attenuation (mW)Potential across LED (V) 2.4 GHz2.45 GHz -20.6309573441.4491.404 0.7943282351.5361.499 011.6191.574 11.2589254121.6481.625 21.5848931921.6691.653 31.9952623151.6851.676 42.5118864321.7021.692 53.162277661.7141.707 97.9432823471.7631.766 Using the 11nH - 3pF - 5pF matching network

Power Requirements Friis Transmission Equation

Project Status

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

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 5880 1 sheet\$0 Provided by Ben Total \$255.65 Remaining Purchases

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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