CONFORMAL WIRELESS

BATTERY PROJECT

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

Lommen’s 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 Z0 given H and εr

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)

Z0 ZL

Matching Network

Impedance Matching (Tuning) Normalizing the impedance:

zL=ZL/Z0

We assumed ZL=15-j150We assumed Z0=50zL=0.3-j3

Impedance Matching (Tuning)Note that zL 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=±[RL(Z0-RL)]^(1/2)-XL

B=±{[ (Z0-RL)/RL]^(1/2)}/RL

Two solutions possible for both B and XPositive X implies an inductorNegative X implies a capacitorPositive B implies a capacitorNegative B implies an inductor

Impedance Matching (Tuning) For positive values

jX=jωLjB=jωC

For negative valuesjX-j/ωCjB=-j/ωL

Test Board

Trial and Error

4.5pF (4 - 1pF + 0.5pF in parallel) 10pF 0.5pF 2.864 -10.24.5pF (4 - 1pF + 0.5pF in parallel) 10pF 5pF 2.75 -6.674.5pF (4 - 1pF + 0.5pF in parallel) 5pF 5pF 2.761 -7.174.5pF (4 - 1pF + 0.5pF in parallel) 5pF 20pF 2.747 -8.67open 5pF 20pF 2.06 -5.15open 5pF 10pF 2.114 -7.54open 5pF 5pF 2.154 -18.59open 5pF 2pF 1.648 -4.01open 10pF 10pF 2.027 -9.42open 20pF 10pF 1.999 -9.495pF 10pF open 2.63 -11open 10pF 5pF 2.09 -22.111nH 10pF 5pF 2.1897 -20.3211nH 5pF 5pF 2.26 -32.111nH 2pF 5pF 2.485 -6.9711nH 3pF 5pF 2.4 -14.1

PI Network Center Freq dBTrace to GND (doubler side) Trace in Series Trace to GND (antenna side) (GHz)

Trial and Error Results

Power Requirements

Power Requirements

Attenuation (dBm) Attenuation (mW) Potential across LED (V)2.4 GHz 2.45 GHz

-2 0.630957344 1.449 1.404-1 0.794328235 1.536 1.4990 1 1.619 1.5741 1.258925412 1.648 1.6252 1.584893192 1.669 1.6533 1.995262315 1.685 1.6764 2.511886432 1.702 1.6925 3.16227766 1.714 1.7079 7.943282347 1.763 1.766

Using the 11nH - 3pF - 5pF matching network

Power Requirements

Friis Transmission Equation

Project Status

Project Status

Tasks remainingRefine impedance matching techniquesVerify operation with antenna installedCharge a AAA batteryExplore flexible substrates

TimelineWant to be charging a battery within the first

4 weeks of next semesterFlexible substrates are a secondary

objective

Budget

Part Quantity Retail CostExpected

CostTotal Cost Notes

AAA Rechargable NiMH Batteries

2 packs (8 batteries)

$10.88/pack $10.88/pack $21.76 Walmart;

Energizer

AA Rechargable NiMH Batteries

2 packs (8 batteries)

$14.84/pack $14.84/pack $29.68

Walmart; Battery Biz

Total $51.44

Part QuantityRetail Cost

Expected Cost

Total Cost Notes

2.4 GHz wireless-G router 1 $41.99 $41.99 $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 $0.68 $68.00

Mouser

Mica 2.4 GHz SMD Antenna 5 $11.20 $11.20 $56.00

Antenova

Rogers duroid 5880 1 sheet $0 $0 Provided

by BenTotal $255.65

Remaining Purchases

Summary

Two PCBs createdInitial prototype including antennaTest board including SMA input

Impedance matching completedNeed to refine this processNeed to incorporate antenna