7/29/2019 RF info

1/4

The RF module, as the name suggests, operates at Radio Frequency. The

corresponding frequency range varies between 30 kHz & 300 GHz. In this RF system,

the digital data is represented as variations in the amplitude of carrier wave. This kind of

modulation is known as Amplitude Shift Keying (ASK).

Transmission through RF is better than IR (infrared) because of many reasons. Firstly,

signals through RF can travel through larger distances making it suitable for long range

applications. Also, while IR mostly operates in line-of-sight mode, RF signals can travel

even when there is an obstruction between transmitter & receiver. Next, RF

transmission is more strong and reliable than IR transmission. RF communication uses

a specific frequency unlike IR signals which are affected by other IR emitting sources.

This RF module comprises of an RF Transmitter and an RF Receiver. The

transmitter/receiver (Tx/Rx) pair operates at a frequency of434 MHz. An RF transmitter

receives serial data and transmits it wirelessly through RF through its antenna

connected at pin4. The transmission occurs at the rate of 1Kbps - 10Kbps.The

transmitted data is received by an RF receiver operating at the same frequency as that

of the transmitter.

The RF module is often used alongwith a pair of encoder/decoder. The encoder is used

for encoding parallel data for transmission feed while reception is decoded by a

decoder. HT12E-HT12D, HT640-HT648, etc. are some commonly used

encoder/decoder pair ICs.

http://www.engineersgarage.com/content/ht12ehttp://www.engineersgarage.com/content/ht12dhttp://www.engineersgarage.com/content/ht12dhttp://www.engineersgarage.com/content/ht12dhttp://www.engineersgarage.com/content/ht12dhttp://www.engineersgarage.com/content/ht12e

7/29/2019 RF info

2/4

Pin Diagram:

Pin Description:

RF Transmitter

Pin No Function Name

1 Ground (0V) Ground

2 Serial data input pin Data

3 Supply voltage; 5V Vcc

4 Antenna output pin ANT

RF Receiver

Pin No Function Name

1 Ground (0V) Ground

2 Serial data output pin Data

3 Linear output pin; not connected NC

4 Supply voltage; 5V Vcc

7/29/2019 RF info

3/4

5 Supply voltage; 5V Vcc

6 Ground (0V) Ground

7 Ground (0V) Ground

8 Antenna input pin ANT

A radio transmitter is anelectronic circuitwhich transforms electric power from a battery or

electrical mainsinto aradio frequencyalternating current, which reverses direction millions to

billions of times per second. The energy in such a rapidly-reversing current can radiate off a

conductor (the antenna) aselectromagnetic waves(radio waves). The transmitter also

"piggybacks" information, such as an audio or video signal, onto the radio frequency current to

be carried by the radio waves. When they strike the antenna of aradio receiver, the waves excite

similar (but less powerful) radio frequency currents in it. The radio receiver extracts the

information from the received waves. A practical radio transmitter usually consists of these parts:

Apower supplycircuit to transform the input electrical power to the highervoltagesneeded to produce the required power output.

Anelectronic oscillatorcircuit to generate theradio frequencysignal. This usually

generates asine waveof constantamplitudeoften called thecarrier wave. In most

modern transmitters this is acrystal oscillatorin which the frequency is precisely

controlled by the vibrations of aquartz crystal.

Amodulatorcircuit to add the information to be transmitted to thecarrier waveproduced

by the oscillator. This is done by varying some aspect of the carrier wave. The

information is provided to the transmitter either in the form of anaudio signal, which

representssound, avideo signal, or for data in the form of abinarydigitalsignal.

o In an AM (amplitude modulation) transmitter theamplitude(strength) of the

carrier wave is varied in proportion to the audio signal.o In an FM (frequency modulation) transmitter thefrequencyof the carrier is varied

by the audio signal.

o In an FSK (frequency-shift keying) transmitter, which transmits digital data, the

frequency of the carrier is shifted between two frequencies which represent the

two binary digits, 0 and 1.

Many other types ofmodulationare also used. In large transmitters the oscillator and

modulator together are often referred to as the exciter.

An RFpower amplifierto increase the power of the signal, to increase the range of the

radio waves. Animpedance matching(antenna tuner) circuit to match theimpedanceof the transmitter

to the impedance of the antenna (or thetransmission lineto the antenna), to transfer

power efficiently to the antenna. If these impedances are not equal, it causes a condition

calledstanding waves, in which the power is reflected back from the antenna toward the

transmitter, wasting power and sometimes overheating the transmitter.

http://en.wikipedia.org/wiki/Electronic_circuithttp://en.wikipedia.org/wiki/Electronic_circuithttp://en.wikipedia.org/wiki/Electronic_circuithttp://en.wikipedia.org/wiki/Mains_powerhttp://en.wikipedia.org/wiki/Mains_powerhttp://en.wikipedia.org/wiki/Radio_frequencyhttp://en.wikipedia.org/wiki/Radio_frequencyhttp://en.wikipedia.org/wiki/Alternating_currenthttp://en.wikipedia.org/wiki/Alternating_currenthttp://en.wikipedia.org/wiki/Alternating_currenthttp://en.wikipedia.org/wiki/Electromagnetic_wavehttp://en.wikipedia.org/wiki/Electromagnetic_wavehttp://en.wikipedia.org/wiki/Electromagnetic_wavehttp://en.wikipedia.org/wiki/Radio_receiverhttp://en.wikipedia.org/wiki/Radio_receiverhttp://en.wikipedia.org/wiki/Radio_receiverhttp://en.wikipedia.org/wiki/Power_supplyhttp://en.wikipedia.org/wiki/Power_supplyhttp://en.wikipedia.org/wiki/Power_supplyhttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Electronic_oscillatorhttp://en.wikipedia.org/wiki/Electronic_oscillatorhttp://en.wikipedia.org/wiki/Electronic_oscillatorhttp://en.wikipedia.org/wiki/Radio_frequencyhttp://en.wikipedia.org/wiki/Radio_frequencyhttp://en.wikipedia.org/wiki/Radio_frequencyhttp://en.wikipedia.org/wiki/Sine_wavehttp://en.wikipedia.org/wiki/Sine_wavehttp://en.wikipedia.org/wiki/Sine_wavehttp://en.wikipedia.org/wiki/Amplitudehttp://en.wikipedia.org/wiki/Amplitudehttp://en.wikipedia.org/wiki/Amplitudehttp://en.wikipedia.org/wiki/Carrier_wavehttp://en.wikipedia.org/wiki/Carrier_wavehttp://en.wikipedia.org/wiki/Carrier_wavehttp://en.wikipedia.org/wiki/Crystal_oscillatorhttp://en.wikipedia.org/wiki/Crystal_oscillatorhttp://en.wikipedia.org/wiki/Crystal_oscillatorhttp://en.wikipedia.org/wiki/Quartz_crystalhttp://en.wikipedia.org/wiki/Quartz_crystalhttp://en.wikipedia.org/wiki/Quartz_crystalhttp://en.wikipedia.org/wiki/Modulatorhttp://en.wikipedia.org/wiki/Modulatorhttp://en.wikipedia.org/wiki/Modulatorhttp://en.wikipedia.org/wiki/Carrier_wavehttp://en.wikipedia.org/wiki/Carrier_wavehttp://en.wikipedia.org/wiki/Carrier_wavehttp://en.wikipedia.org/wiki/Audio_signalhttp://en.wikipedia.org/wiki/Audio_signalhttp://en.wikipedia.org/wiki/Audio_signalhttp://en.wikipedia.org/wiki/Soundhttp://en.wikipedia.org/wiki/Soundhttp://en.wikipedia.org/wiki/Soundhttp://en.wikipedia.org/wiki/Video_signalhttp://en.wikipedia.org/wiki/Video_signalhttp://en.wikipedia.org/wiki/Video_signalhttp://en.wikipedia.org/wiki/Binary_numeral_systemhttp://en.wikipedia.org/wiki/Binary_numeral_systemhttp://en.wikipedia.org/wiki/Digitalhttp://en.wikipedia.org/wiki/Digitalhttp://en.wikipedia.org/wiki/Digitalhttp://en.wikipedia.org/wiki/Amplitude_modulationhttp://en.wikipedia.org/wiki/Amplitude_modulationhttp://en.wikipedia.org/wiki/Amplitude_modulationhttp://en.wikipedia.org/wiki/Amplitudehttp://en.wikipedia.org/wiki/Amplitudehttp://en.wikipedia.org/wiki/Amplitudehttp://en.wikipedia.org/wiki/Frequency_modulationhttp://en.wikipedia.org/wiki/Frequency_modulationhttp://en.wikipedia.org/wiki/Frequency_modulationhttp://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Frequency-shift_keyinghttp://en.wikipedia.org/wiki/Frequency-shift_keyinghttp://en.wikipedia.org/wiki/Frequency-shift_keyinghttp://en.wikipedia.org/wiki/Modulationhttp://en.wikipedia.org/wiki/Modulationhttp://en.wikipedia.org/wiki/Modulationhttp://en.wikipedia.org/wiki/Power_amplifierhttp://en.wikipedia.org/wiki/Power_amplifierhttp://en.wikipedia.org/wiki/Power_amplifierhttp://en.wikipedia.org/wiki/Impedance_matchinghttp://en.wikipedia.org/wiki/Impedance_matchinghttp://en.wikipedia.org/wiki/Impedance_matchinghttp://en.wikipedia.org/wiki/Antenna_tunerhttp://en.wikipedia.org/wiki/Antenna_tunerhttp://en.wikipedia.org/wiki/Antenna_tunerhttp://en.wikipedia.org/wiki/Electrical_impedancehttp://en.wikipedia.org/wiki/Electrical_impedancehttp://en.wikipedia.org/wiki/Electrical_impedancehttp://en.wikipedia.org/wiki/Transmission_linehttp://en.wikipedia.org/wiki/Transmission_linehttp://en.wikipedia.org/wiki/Transmission_linehttp://en.wikipedia.org/wiki/Standing_wavehttp://en.wikipedia.org/wiki/Standing_wavehttp://en.wikipedia.org/wiki/Standing_wavehttp://en.wikipedia.org/wiki/Standing_wavehttp://en.wikipedia.org/wiki/Transmission_linehttp://en.wikipedia.org/wiki/Electrical_impedancehttp://en.wikipedia.org/wiki/Antenna_tunerhttp://en.wikipedia.org/wiki/Impedance_matchinghttp://en.wikipedia.org/wiki/Power_amplifierhttp://en.wikipedia.org/wiki/Modulationhttp://en.wikipedia.org/wiki/Frequency-shift_keyinghttp://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Frequency_modulationhttp://en.wikipedia.org/wiki/Amplitudehttp://en.wikipedia.org/wiki/Amplitude_modulationhttp://en.wikipedia.org/wiki/Digitalhttp://en.wikipedia.org/wiki/Binary_numeral_systemhttp://en.wikipedia.org/wiki/Video_signalhttp://en.wikipedia.org/wiki/Soundhttp://en.wikipedia.org/wiki/Audio_signalhttp://en.wikipedia.org/wiki/Carrier_wavehttp://en.wikipedia.org/wiki/Modulatorhttp://en.wikipedia.org/wiki/Quartz_crystalhttp://en.wikipedia.org/wiki/Crystal_oscillatorhttp://en.wikipedia.org/wiki/Carrier_wavehttp://en.wikipedia.org/wiki/Amplitudehttp://en.wikipedia.org/wiki/Sine_wavehttp://en.wikipedia.org/wiki/Radio_frequencyhttp://en.wikipedia.org/wiki/Electronic_oscillatorhttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Power_supplyhttp://en.wikipedia.org/wiki/Radio_receiverhttp://en.wikipedia.org/wiki/Electromagnetic_wavehttp://en.wikipedia.org/wiki/Alternating_currenthttp://en.wikipedia.org/wiki/Radio_frequencyhttp://en.wikipedia.org/wiki/Mains_powerhttp://en.wikipedia.org/wiki/Electronic_circuit

7/29/2019 RF info

4/4

In higher frequency transmitters, in theUHFandmicrowaverange, oscillators that operate stably

at the output frequency cannot be built. In these transmitters the oscillator usually operates at a

lower frequency, and is multiplied byfrequency multipliersto get a signal at the desired

frequency.

http://en.wikipedia.org/wiki/Ultrahigh_frequencyhttp://en.wikipedia.org/wiki/Ultrahigh_frequencyhttp://en.wikipedia.org/wiki/Ultrahigh_frequencyhttp://en.wikipedia.org/wiki/Microwavehttp://en.wikipedia.org/wiki/Microwavehttp://en.wikipedia.org/wiki/Microwavehttp://en.wikipedia.org/wiki/Frequency_multiplierhttp://en.wikipedia.org/wiki/Frequency_multiplierhttp://en.wikipedia.org/wiki/Frequency_multiplierhttp://en.wikipedia.org/wiki/Frequency_multiplierhttp://en.wikipedia.org/wiki/Microwavehttp://en.wikipedia.org/wiki/Ultrahigh_frequency