Transcript DT3: RF On/Off Remote Control Technology

DT3: RF On/Off Remote
Control Technology
Rodney Singleton
Joe Larsen
Luis Garcia
Rafael Ocampo
Mike Moulton
Eric Hatch
Agenda
Radio Frequency Overview
 Frequency Selection
 Signals Methods
 Modulation Methods

Radio Frequency
Spans from 3kHz to 300GHz
 Advantage:
Long Distance
 No stress on line-of-sight


Disadvantage:
Needs to be operated in accordance with the
FCC
 Interference occurs between RF devices

Remote Control using RF

Remote Control:

Wireless device used to operate audio, video
and/or other electronic equipment using
transmission.
 Car
opener
 Garage Door

Specifically for our project:

Using RF as a remote control to power on/off
a system.
Selecting a frequency

Spectrum Characteristics
How “rich” is your signal
 Distance and environment


Legal Considerations
Licensed or unlicensed
 Allowed power output
 International regulations

Generalizing the RF Spectrum
Frequency
Examples
3 Hz – 30 kHz
Submarine Communications
30 kHz – 300 kHz
RFID, Navigation Signals
300 kHz – 3 MHz
AM Broadcasts
3 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, GPS
3 GHz – 30 GHz
WLAN, Backhaul Communications
• Lower frequencies will go further and more easily
penetrate obstacles
• Higher frequencies have greater bandwidth
Licensed Frequencies

If a RF signal is considered “Mission
Critical” a license should be considered
Allows for sole use of that frequency
 Significant cost

 $19
Billion raised in 700 MHz auction
 Large Telecommunication providers

Other options do exist in the unlicensed
spectrum
ISM Band


Industrial, Scientific, and Medical
bands
A shared and unlicensed set of
frequencies




Must accept all interference received
Transmission power regulations
Usage regulations
Regulations vary by country

Max power output for 2.4 GHz:



US: 30 dBm, before antenna. 36 dBm,
with antenna.
Europe: 20 dBm
900 MHz is unlicensed only in North and
South America
Frequency range
6.765–6.795 MHz
13.553–13.567 MHz
26.957–27.283 MHz
40.66–40.70 MHz
433.05–434.79 MHz
902–928 MHz
2.400–2.500 GHz
5.725–5.875 GHz
24–24.25 GHz
61–61.5 GHz
122–123 GHz
244–246 GHz
ISM Congestion
900 MHz and 2.4 GHz ranges are
extremely congested
 Urban areas will have higher congestion

RF Detection

RF detector monitors the output of an
RF circuit and develops a dc output
voltage.

RF detectors are used primarily to
measure and control RF power in
wireless systems.

In a receiver:


Signal strength is a key factor in
maintaining reliable communications.
In a transmitter:

The amount of power transmitted is
critical because of regulatory guidelines.
Main Applications of RF Detectors

Transmitter output power measurement is the primary
application.

It is essential to know the RF output power.

In many cases, the transmitter power is controlled
automatically.

As a result, the output power is measured and compared
to a set point level in a feedback control circuit so power
can be adjusted as required.
Types of RF Detectors
There are two basic types:
1.
Logarithmic type
2.
RMS type.

The log type converts the input
RF power into a dc voltage proportional to the log
of the input, making the output directly related to
decibels.

The RMS detector creates a dc output proportional
to the RMS value of the signal.
General Criteria for Selecting RF
Detectors

The type of RF signal to be measured is the most
important determining factor in the type of detector to
use.

Log type is best for:



general power measurement and control applications
pulsed RF signals
RMS type is best for:

those applications where then signal has a high crest factor or a
widely varying crest factor
*The crest factor is the ratio of the peak to RMS value of the signal.
Binary Coding
The process of coding pieces of information
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)

Most basic of shift key
modulations.

Binary form of AM

Type of ASK

On/Off Key
Advantages v. Disadvantages of ASK

WOO-HOO’s:
Cheaper
 Conserves
power with the
case of OOK


BOO’s:

Susceptible to
interference
What is FSK ???


A frequency modulation scheme where digital
information is transmitted through discrete
frequency changes of a carrier wave.
Two types are Minimum-shift keying (MSK) and
Audio frequency-shift keying (AFSK).
Common Applications of FSK

Remote Metering



Automatic Meter Reading
(AMR)
Car door openers/remote
car starters.
Garage door openers
Advantages of FSK

Rejects unwanted noise

Better signal-to-noise ratio

Automatic volume control
Disadvantages of FSK

Expensive

High power consumption

Slow data transmission
Phase Shift Keying (PSK)
A digital implementation of Phase
Modulation (PM)
 Most forms of digital data transmission
used a form of Phase Modulation
 Very high bitrate capabilities
 Unnecessarily complicated for most
remote control applications

Analog Signaling (Tone Signals)



Information sent using analog tones within the
voice band (20 Hz – 20 kHz)
Tones detected or not detected, corresponding
to binary ‘1’ or ‘0’
Tones of frequency ‘a’ corresponds to ‘1’,
frequency ‘b’ corresponds to ‘0’ (AFSK)


Can use any analog modulation technique and
existing equipment
Commonly used by amateur radio and emergency
services
Conclusion
Frequency Selection
 RF Detection
 Types of Encoding
 Types of Modulation


Questions?