DT3: RF On/Off Remote DT3: RF On/Off Remote Control TechnologyControl Technology

Rodney SingletonRodney SingletonJoe LarsenJoe LarsenLuis GarciaLuis Garcia

Rafael OcampoRafael OcampoMike MoultonMike Moulton

Eric HatchEric Hatch

AgendaAgenda

Radio Frequency OverviewRadio Frequency Overview Frequency SelectionFrequency Selection Signals MethodsSignals Methods Modulation MethodsModulation Methods

Radio FrequencyRadio Frequency

Spans from 3kHz to 300GHzSpans from 3kHz to 300GHz Advantage:Advantage:

Long DistanceLong Distance No stress on line-of-sightNo stress on line-of-sight

Disadvantage:Disadvantage: Needs to be operated in accordance with the Needs to be operated in accordance with the

FCCFCC Interference occurs between RF devicesInterference occurs between RF devices

Remote Control using RFRemote Control using RF Remote Control:Remote Control:

Wireless device used to operate audio, video Wireless device used to operate audio, video and/or other electronic equipment using and/or other electronic equipment using transmission.transmission. Car openerCar opener Garage DoorGarage Door

Specifically for our project:Specifically for our project: Using RF as a remote control to power on/off Using RF as a remote control to power on/off

a system.a system.

Selecting a frequencySelecting a frequency Spectrum CharacteristicsSpectrum Characteristics

How “rich” is your signalHow “rich” is your signal Distance and environmentDistance and environment

Legal ConsiderationsLegal Considerations Licensed or unlicensedLicensed or unlicensed Allowed power outputAllowed power output International regulationsInternational regulations

Generalizing the RF Spectrum Generalizing the RF Spectrum Frequency Examples3 Hz – 30 kHz Submarine Communications30 kHz – 300 kHz RFID, Navigation Signals300 kHz – 3 MHz AM Broadcasts3 MHz – 30 MHz Amateur radio, RFID 30 MHz – 300 MHz FM Radio, Line of sight aircraft communication, Maritime

Radio

300 MHz – 3 GHz Broadcast TV, Cell phones, WLAN, Bluetooth, GPS3 GHz – 30 GHz WLAN, Backhaul Communications

• Lower frequencies will go further and more easily penetrate obstacles

• Higher frequencies have greater bandwidth

Licensed FrequenciesLicensed Frequencies If a RF signal is considered “Mission If a RF signal is considered “Mission

Critical” a license should be consideredCritical” a license should be considered Allows for sole use of that frequencyAllows for sole use of that frequency Significant costSignificant cost

$19 Billion raised in 700 MHz auction$19 Billion raised in 700 MHz auction Large Telecommunication providersLarge Telecommunication providers

Other options do exist in the unlicensed Other options do exist in the unlicensed spectrumspectrum

ISM BandISM Band Industrial, Scientific, and Medical Industrial, Scientific, and Medical

bandsbands A shared and unlicensed set of A shared and unlicensed set of

frequenciesfrequencies Must accept all interference receivedMust accept all interference received Transmission power regulationsTransmission power regulations Usage regulationsUsage regulations

Regulations vary by countryRegulations vary by country Max power output for 2.4 GHz:Max power output for 2.4 GHz:

US: 30 dBm, before antenna. 36 dBm, US: 30 dBm, before antenna. 36 dBm, with antenna.with antenna.

Europe: 20 dBmEurope: 20 dBm 900 MHz is unlicensed only in North and 900 MHz is unlicensed only in North and

South AmericaSouth America

Frequency range6.765–6.795 MHz13.553–13.567 MHz26.957–27.283 MHz40.66–40.70 MHz433.05–434.79 MHz902–928 MHz2.400–2.500 GHz5.725–5.875 GHz24–24.25 GHz61–61.5 GHz122–123 GHz244–246 GHz

ISM CongestionISM Congestion 900 MHz and 2.4 GHz ranges are 900 MHz and 2.4 GHz ranges are

extremely congestedextremely congested Urban areas will have higher congestionUrban areas will have higher congestion

RF Detection RF Detection

RF detector monitors the output of an RF detector monitors the output of an RF circuit and develops a dc output RF circuit and develops a dc output voltage.voltage.

RF detectors are used primarily to RF detectors are used primarily to measure and control RF power in measure and control RF power in wireless systems.wireless systems.

In a receiver:In a receiver: Signal strength is a key factor in Signal strength is a key factor in

maintaining reliable communications.maintaining reliable communications. In a transmitter:In a transmitter:

The amount of power transmitted is The amount of power transmitted is critical because of regulatory guidelines. critical because of regulatory guidelines.

Main Applications of RF DetectorsMain Applications of RF Detectors Transmitter output power measurement is the primary Transmitter output power measurement is the primary

application.application.

It is essential to know the RF output power. It is essential to know the RF output power.

In many cases, the transmitter power is controlled In many cases, the transmitter power is controlled automatically. automatically.

As a result, the output power is measured and compared As a result, the output power is measured and compared to a set point level in a feedback control circuit so power to a set point level in a feedback control circuit so power can be adjusted as required. can be adjusted as required.

Types of RF Detectors Types of RF Detectors There are two basic types: There are two basic types: 1.1. Logarithmic type Logarithmic type 2.2. RMS type. RMS type.

The log type converts the inputThe log type converts the inputRF power into a dc voltage proportional to the logRF power into a dc voltage proportional to the logof the input, making the output directly related toof the input, making the output directly related todecibels. decibels.

The RMS detector creates a dc output proportionalThe RMS detector creates a dc output proportionalto the RMS value of the signal.to the RMS value of the signal.

General Criteria for Selecting RF General Criteria for Selecting RF DetectorsDetectors

The type of RF signal to be measured is the most The type of RF signal to be measured is the most important determining factor in the type of detector to important determining factor in the type of detector to use. use.

Log type is best for:Log type is best for: general power measurement and control applicationsgeneral power measurement and control applications pulsed RF signalspulsed RF signals

RMS type is best for:RMS type is best for: those applications where then signal has a high crest factor or a those applications where then signal has a high crest factor or a

widely varying crest factorwidely varying crest factor

*The crest factor is the ratio of the peak to RMS value of the signal.*The crest factor is the ratio of the peak to RMS value of the signal.

Binary CodingBinary CodingThe process of coding pieces of information The process of coding pieces of information

and are assigned the values of “0” or “1”.and are assigned the values of “0” or “1”.

Examples of binary coding for:

• Unique codes for different devices

• Character strings to bit strings

• Security

Amplitude Shift Key Modulation (ASK)Amplitude Shift Key Modulation (ASK)

Most basic of shift key Most basic of shift key modulations.modulations.

Binary form of AMBinary form of AM

Type of ASKType of ASK On/Off KeyOn/Off Key

Advantages v. Disadvantages of ASKAdvantages v. Disadvantages of ASK

WOO-HOO’s:WOO-HOO’s: CheaperCheaper Conserves Conserves

power with the power with the case of OOKcase of OOK

BOO’s: Susceptible to

interference

What is FSK ???What is FSK ??? A frequency modulation scheme where digital A frequency modulation scheme where digital

information is transmitted through discrete information is transmitted through discrete frequency changes of a carrier wave.frequency changes of a carrier wave.

Two types are Two types are Minimum-shift keying (MSK)Minimum-shift keying (MSK) and and Audio frequency-shift keying (AFSK)Audio frequency-shift keying (AFSK)..

Common Applications of FSKCommon Applications of FSK

Remote MeteringRemote Metering Automatic Meter Reading Automatic Meter Reading

(AMR)(AMR) Car door openers/remote Car door openers/remote

car starters.car starters. Garage door openersGarage door openers

Advantages of FSKAdvantages of FSK Rejects unwanted noiseRejects unwanted noise

Better signal-to-noise ratioBetter signal-to-noise ratio

Automatic volume controlAutomatic volume control

Disadvantages of FSKDisadvantages of FSK ExpensiveExpensive

High power consumptionHigh power consumption

Slow data transmissionSlow data transmission

Phase Shift Keying (PSK)Phase Shift Keying (PSK) A digital implementation of Phase A digital implementation of Phase

Modulation (PM)Modulation (PM) Most forms of digital data transmission Most forms of digital data transmission

used a form of Phase Modulationused a form of Phase Modulation Very high bitrate capabilitiesVery high bitrate capabilities Unnecessarily complicated for most Unnecessarily complicated for most

remote control applicationsremote control applications

Analog Signaling (Tone Signals)Analog Signaling (Tone Signals) Information sent using analog tones within the Information sent using analog tones within the

voice band (20 Hz – 20 kHz)voice band (20 Hz – 20 kHz) Tones detected or not detected, corresponding Tones detected or not detected, corresponding

to binary ‘1’ or ‘0’to binary ‘1’ or ‘0’ Tones of frequency ‘a’ corresponds to ‘1’, Tones of frequency ‘a’ corresponds to ‘1’,

frequency ‘b’ corresponds to ‘0’ (AFSK)frequency ‘b’ corresponds to ‘0’ (AFSK) Can use any analog modulation technique and Can use any analog modulation technique and

existing equipmentexisting equipment Commonly used by amateur radio and emergency Commonly used by amateur radio and emergency

servicesservices

ConclusionConclusion Frequency Selection Frequency Selection RF DetectionRF Detection Types of EncodingTypes of Encoding Types of ModulationTypes of Modulation

Questions?Questions?