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Team Watts in the Box Presents… TeslaBox. Stephen Bennett Devin Callahan Ben Kaslon Sushia Rahimizadeh Connor Shapiro . Project Proposal and Purpose Hardware Design and Implementation Level 1 and 2 Block Diagrams Software Design and Implementation Use Case, System Context Diagram

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team watts in the box presents teslabox

Team Watts in the Box Presents… TeslaBox

Stephen Bennett

Devin Callahan

Ben Kaslon

Sushia Rahimizadeh

Connor Shapiro


Project Proposal and Purpose

  • Hardware Design and Implementation
    • Level 1 and 2 Block Diagrams
  • Software Design and Implementation
    • Use Case, System Context Diagram
  • Division of Labor for Major Tasks
  • Feasibility and Risks
  • Economic Viability, Environmental Aspects, Sustainability, Manufacturability, Safety, & Impact
  • Schedule for the First Semester of Work
  • Budget

Sushia Rahimizadeh


This project will consist of a scalable box or drawer in which small hand-held devices or toys can be placed and wirelessly charged.

The box will require only an external source of power in order to be able to charge the devices.

The devices will perform all RF harvesting and charging automatically without user input.

The user simply opens the lid, places the devices inside, and shuts the lid. The devices do the rest.

Sushia Rahimizadeh


The purpose of this project is to demonstrate the feasibility of scalable, commercially viable wireless charging.

  • It will be shown that any device is capable of being integrated with this technology and can be charged wirelessly in any station.
    • These stations can be placed in any household, business, hotel room, etc. and can be of varying size.

Sushia Rahimizadeh

state of the art

Heinrich Hertz – Directional, relatively high power free-space power transmission

  • Nikola Tesla – High power, omnidirectional power transmission
  • Jet Propulsion Laboratory and Raytheon (1973) -- 30 kW transferred over 1.6 km
  • Topic of “Wireless Power” has been of interest since early 1900’s

Sushia Rahimizadeh

State of the Art

Number of books that include the keyword “wireless power” since 1800, found by using Google Ngrams.


“Power Transmission”

    • DC electrical power into RF power
    • RF power transmitted through space to some electrically far point
    • Power is collected and converted into DC power at this point

Sushia Rahimizadeh

  • Multi-mode cavity
  • No field nulls
  • Field uniformity desired
  • Harvest power at any point within the cavity
expo deliverables

Hinged box

    • Disables power transmission when open
    • Enclosed by conductive mesh
    • Can mount all Tx antennas and display
  • RF Energy Transfer
    • Uses antennas, not coupled inductors
    • High overall efficiency
      • High conversion efficiency (DC  RF, RF  DC , DC  DC)
      • Aperture-to-Aperture efficiency
  • Power Management Circuits
    • Supports Li-Ion and Ni-MH

Sushia Rahimizadeh

Expo Deliverables
expo deliverables1

Externally-mounted display

    • Unique device identification
    • Power received
    • Remaining charge time

Sushia Rahimizadeh

Expo Deliverables
power transmit circuit


    • Converts supply power into a 1W 2.2 GHz RF modulated signal

Ben Kaslon

Power Transmit Circuit
voltage controlled oscillator


    • Convert supply power to a 2.2 GHz signal
  • Design Goals:
    • This signal will be modulated tens of MHz around 2.2GHz in order to improve power density uniformity in the box.
    • During development, input power is supplied from lab bench DC supply, but final design will be supplied from standard wall outlet.

Ben Kaslon

Voltage-Controlled Oscillator

Voltage Controlled Oscillator: Crystek CVCO55BE

frequency allocation
Ben KaslonFrequency Allocation
  • 2.2GHz was chosen
    • Unallocated in commercial space
    • No consumer wireless devices will be harmed by this frequency coupling onto the devices
    • Reduced component size
    • Large availability of components operate at this frequency
power amplifier


    • Amplify 2.2GHz signal from the VCO to 1W
  • Design Goal:
    • Must be designed to make the transmitter circuit as efficient as possible.

Ben Kaslon

Power Amplifier

Example Power Amplifier

transmit antenna


    • Transmits the amplified and modulated 2.2GHz signal
  • Design Goal:
    • Match Simulations
    • Display low loss to circuit
    • Well matched to the operating frequency
    • Widest bandwidth possible.

Ben Kaslon

Transmit Antenna
transmit antenna1

Patch antenna will be used.

    • Relatively easy to design
    • Small size
    • Low cost
    • Can be etched directly into PCB
    • Lots of research available on design

Ben Kaslon

Transmit Antenna

Example Patch Antenna

power transmit circuit risks

Efficiency of the designed power amplifier too low

    • If we are unable to design a sufficiently efficient amplifier, a COTS amplifier will have to be used
    • Ideally want 90% but will accept 50%
  • Design of the antenna does not match the simulations.
    • New simulations will have to be done with different, more predictable substrates
  • Non-uniform field distribution in the cavity
    • Need to try a new modulation scheme

Ben Kaslon

Power Transmit Circuit Risks
receiver circuit

Receiving arbitrarily polarized radiation within the cavity

Rectifying received microwave power to DC power

Maintain optimal power transfer throughout

Ben Kaslon

Receiver Circuit
receive antenna


    • Receive microwave power
  • Design Goals:
    • Polarization diversity
    • Harmonic rejection
    • Low reflections at fundamental frequency

Ben Kaslon

Receive Antenna
matching circuit

Rectifier input impedance is a function of:

    • Frequency
    • Power
    • DC Load
    • Harmonic terminations
  • Responsibilities:
    • Ensuring optimal power transfer between antenna and rectifier
  • Design Goals:
    • Achieve a low reflection coefficient
    • Low insertion loss
    • A precise, common impedance

Ben Kaslon

Matching Circuit


    • Rectify microwave power to DC power
  • Design Goals:
    • Maximize rectification efficiency
    • Low insertion loss
    • High switching speed
    • Smaller devices (smaller junction capacitance).

Ben Kaslon

receiver circuit risks

Sub-Operational Efficiencies

    • Increasing power transmitted into cavity
    • Antenna matching circuit redesign
  • Interference from device
    • Isolation will have to be introduced

Ben Kaslon

Receiver Circuit Risks
power management circuit

Design Goals:

    • Maximize boost converter efficiency
    • Minimize microcontroller power consumption

Connor Shapiro

Power Management Circuit
  • Responsibilities:
    • Charge controlling
      • Ni-MH
      • Li-Ion
    • Battery monitoring
      • Generation of UI/display data
power management circuit risks

Battery over-charging

    • Prioritize cell protection
  • No power to turn on microcontroller – total system failure
    • Specialized cold-start circuit

Connor Shapiro

Power Management Circuit Risks
battery charging

Ni-MH Charge Cycle

    • Constant-Current
  • End-of-charge based on following peak V

Connor Shapiro

Battery Charging
  • Li-Ion Charge Cycle
    • Constant-Current & Constant-Voltage
  • End-of-charge based end of current-draw
display circuit

Antenna receives device status information

Microcontroller routine to translate data to generic display instructions

Connor Shapiro

Display Circuit
example lcd displays

Small compact LCD Display

Designed to interface easily with any MCU

Can be used to display any generic shapes

Cycle through displaying data for each device

Connor Shapiro

Example LCD Displays
microcontroller tasks
Stephen BennettMicrocontroller Tasks

Power Manager

Display Manager

Decode power data packets

Convert received data to appropriate display format

  • Rectified power detection
  • Power management
    • Control boost converter to produce correct battery charging profile
  • Monitor voltage and current going to chargeable device
  • Packetize power data and device ID for transmission to display circuit


    • Transceivers
      • Sending/receiving data at appropriate frequency
      • Outputting clean signal to microcontroller
    • Microcontroller
      • Translating data to display instructions
    • Display
      • Outputting data to user
  • Design Goals:
    • Display instructions are independent of received data format
    • Displayed data is readable and user friendly

Stephen Bennett

microcontroller and transceiver
Stephen BennettMicrocontroller and Transceiver
  • MSP430 family
    • Low cost
    • Low power
    • Integrates well with CC1110
    • Prior experience
  • CC1110 Transceiver
    • 315-915 MHz
    • Easy integration with MSP430
  • CC430 family
    • MSP430 with integrated CC1110


CC1110 Transceiver

software risks

Code rewrites due to changes in underlying hardware

    • Careful code design that is as hardware-independent as possible
  • Code size exceeds space on microcontroller
    • Choose a microcontroller with more onboard memory
    • Worst case – add external memory
  • Regressions or bugs created by new code
    • Use a version control system (Git) in order to keep an immutable code history

Stephen Bennett

Software Risks
division of labor

Sushia Rahimizadeh

    • Research in energy harvesting, communications systems, and embedded systems
  • Ben Kaslon
    • Antenna design with a background in RF theory (Space Grant)
    • Experience with VNA’s, SA’s and RF design software (NIST)
  • Devin Callahan
    • Analog circuit design, implementation, and control (LSI)

Devin Callahan

Division of Labor
  • Stephen Bennett
    • Software background in embedded wireless communications platform (Qualcomm)
    • Power management background (Space Grant)
  • Connor Shapiro
    • Power management background (TI & coursework)

Academic Resources

    • ZoyaPopovic – Faculty Advisor
      • Provide guidance in power amplifier and antenna design
    • Steve Dunbar – Ph.D. Student
      • TI Analog/RF applications engineer willing to assist in component selection and applications
    • Sean Korhummel – Ph.D. Student
      • Provide guidance in converter design
  • Outside research already exists

Devin Callahan


Most required components can be purchased directly from electronics suppliers, including:

    • Voltage-controlled oscillators
    • Microcontrollers
    • Power transistors
    • Converter inductors, diodes & capacitors

Devin Callahan

economic viability

A household or business can purchase one of the boxes

  • Any device outfitted with the charging hardware will be able to be charged in any box
  • Low cost to produce a unit
    • Most cost found in the container
    • Relatively small cost for manufacturing of electronics

Devin Callahan

Economic Viability

Most parts are available commercially

    • Voltage controlled oscillator
    • Microcontroller
    • Peripheral parts
  • Parts that are not available commercially will designed
    • Need to be designed for efficiency
      • Power amplifier
      • Rectifier
      • Antennas
    • Cheap to produce
  • Low maintenance expectations
    • Unexpected component malfunction exempting

Devin Callahan


Main concern of the system is to ensure minimum leak of RF power in compliance with FCC regulations

It will be easy to see if this project is working or not. Either the battery on the device will be charged or it will not

Component tolerances will not affect the design, apart from negligible detractions from system efficiency

Devin Callahan

environmental considerations

Leaked power is chief concern

    • The system must abide by FCC regulations by emitting no stray power
    • Also relates to overall efficiency
    • No other environmental concerns

Devin Callahan

Environmental Considerations

This system exhibits zero risk to the environment or the population so long as all RF energy is kept within the box

A standard 120VAC outlet plug will eventually be used

Devin Callahan

impact on society


RF energy transfer proof-of-concept

Devin Callahan

Impact on Society
reach goals

Additional battery chemistries

More advanced GUI

USB Charging

Devin Callahan

Reach Goals