Low Power FM ReceiverLow Power FM Receiver

Andrew YoungNovember 17, 2008

OverviewOverview

Project Inspiration RequirementsDifferencesDesign Block DiagramDesign SchematicOperational FlowchartLCD LayoutQuestions

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InspirationInspiration2008 IEEE Student Contest

◦ Objective: Create low power FM radio receiver ◦ Can use commercially-available IC subsystems

Senior Design Project◦ Competition between two teams◦ Goal is lowest power consumption

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Design Requirements Receive FM radio from 88.1 to 107.9 MHz Output audio at > 4mW per channel to standard 32-

Ohm headphones (33-Ohm resistors used for testing) Adjustable volume/station Interact with user via LCD interface Entire design implemented on one PCB

Competition Testing: One supply source, < 15V DC Design allows for internal circuit inspection

Optional Extras: Display RDS data (station name, artist, song title) Any extra features (signal strength, station presets,

menu) My own customization – video games, easter eggs, etc.

DifferencesWhat is different about this

design compared to the senior design project?◦Extra features – Something cool to

add which takes advantage of already-existing components, such as the attached LCD and joystick (video game, perhaps?).

Design Block DiagramDesign Block Diagram

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FM Receiver IC

(Si4703)

Microcontroller

(ATMega32)

LCD/User Interface104.1

Headphone Amplifier

Schematic - Page 1Push Buttons

FM Receiver

ATMega32

Switching Power Supply

Voltage Adjustment

LCDPort A

Port B Audio L/R

Battery Output

Si4703 Comm

Schematic - Page 2Batteries (2x AA)

Clock Generator Headphone Jack

Audio Amplifier

Gain Adjustment

Potentiometers Noise Suppression

Input Coupling

ESD Protection

Audio L/R

Low Voltage Input

On/Off Switch

AVR Application Development

Codevision AVR IDE (Evaluation) ◦Limited to 2kB code size◦Built-in libraries (LCD, I2C, Power-

Save)

AVR Studio 4.0 ◦Used to debug and set clock rates,

voltage levels, fuses

Operational FlowchartOperational Flowchart

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Power onAVR

Initializes Receiver &

LCDSet to

Default Station & Volume

Receive RDS Data

Interrupt When Button Pressed

Determine Button Pressed

(Volume Up or Down, Tune Up or Down)

Receive Signal

Strength

Output Signal & RDS to

LCD

Send Appropriate Signal to IC to Change Volume/Station

Send Appropriate Signal to Receive Current

Volume/Station

Translate Data to LCD Output

Return from Interrupt

Idle

Interrupt

LCD LayoutLCD Layout

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104.1 - KZRZArtist – Song NameSig. █ █ █ █Vol. █ █ █ █ █ █ █ █ █

SummarySummaryDesigning Low-Power FM Radio Receiver w/ Inspiration: Senior Design CompetitionExtras: Features not required by the senior

design project, such as a video game using the 4x20 LCD and the attached joystick.

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QuestionsQuestions

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ATMega32 AVR

Silicon Labs Si4703

Headphone Amplifier – MAX9725