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What is a RF Transmitter and Receiver?

An RF module (short for radio-frequency module) is a (typically) small electrical device that allows two devices to send and receive radio signals. It is frequently useful in an embedded system to connect with another device wirelessly. Radio waves, a type of electromagnetic radiation with known radio frequencies ranging from 3kHz to 300 GHz, are used to communicate.

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. We will learn what an RF transmitter and receiver are in this post. We’ll also go through some of its features and applications.

What is RF Module?

The RF module, as its name suggests, works at radio frequency. This frequency band spans 30 kHz and 300 GHz. The digital data is represented as variations in the amplitude of the carrier wave in this RF system.This types of modulation is an Amplitude Shift Keying (ASK) .

An RF Transmitter and an RF Receiver are included in this RF module. The frequency of the transmitter/receiver (Tx/Rx) pair is 434 MHz. An RF transmitter accepts serial data and wirelessly delivers it via RF via its antenna linked to pin4. The transmission speed is between 1 and 10 kilobits per second. An RF receiver operating at the same frequency as the transmitter receives the transmitted data.

When sending logic zero while fully suppressing the carrier frequency, the transmitter draws no power, consuming much less power in battery operation. When logic one is sent carrier is fully on to about 4.5mA with a 3volts power supply. The data is transmitted serially from the transmitter to the tuned receiver. For data transfer, the transmitter and receiver are connected to two microcontrollers.

The transmitter/receiver (Tx/Rx) of this Radio Frequency (RF) module uses Amplitude Shift Keying (ASK). This serial input is transmitted over RF by the hybrid ASK Transmitter. The transmitted signal is then received by the Receiver module, which is located away from the source of transmission. As a result, these RF signals are broadcast at a specific frequency and baud rate. The sent data is only received by the RF receiver if it operates at the same frequency as the transmitter. Furthermore, this RF module can be used in a car security system, a remote keyless entry system, a garage door controller, a home security system, a wireless mouse, and an automation system.

Features of RF Module:

  • The Receiver frequency 433MHz
  • Receiver typical frequency 105 Dbm
  • Receiver supply current 3.5 mA
  • Low power consumption
  • operating voltage of receiver is  5V
  • The transmitter frequency range 433.92MHz
  • Supply voltage of transmitter is between 3V to 6V
  • Output power of transmitter is between 4Dbm to 12Dbm

433 MHz RF Transmitter and Receiver:

434 Mhz wireless RF module is basically a superheterodyne Amplitude Shift Keying / ook (On-Off keying-based) module. This RF module designed based on an RF Transmitter and an RF Receiver operates at a frequency of 433 MHz.This RF module is often used with a pair of encoder/decoder. This is an RF Encoder & Decoder Interfacing board with HT12D & HT12E IC chips. HT12E used to encode data for RF Transmitter and HT12D used to decode the data received by the RF receiver. The module consists of a SAW resonator tuned for 433.xx MHz operation. Moreover, there is a switching transistor and a few passive components to perform the functions.

HT 12E Encoder ICs designed as series of CMOS LSIs for Remote Control system applications. It Encodes 12 bits of information which consists of N address bits and 12-N data bits. The HT 12D ICs decoder designed as a series of CMOS LSIs that pairs each other with  HT12E encoder. The encoder/decoder pair should be with the same number of addresses and data formats for proper operation. The Decoder receives the serial address and data from its corresponding decoder, transmitted by a carrier using an RF transmission medium. Thus output fed to the output pins of the microcontroller after processing the data.

The Transmitter transmits encoded serial input through RF. Then the Receiver module receives the transmitted signal placed away from the source of transmission. Thus these RF signals transmitted at a particular frequency and a baud rate.  The RF receiver receives the transmitted data only if it operating at the same frequency as that of the transmitter. The transmitter module comes with an RF tuned circuit and a couple of OP Amps to amplify the received carrier wave from the transmitter. This amplified signal is further fed to a PLL (Phase Lock Loop) which enables the decoder to “lock” onto a stream of digital bits. This gives better-decoded output and noise immunity.

  • Operating voltage: 3.6~5.5v ( 5v recommended),
  • Receiver sensitivity as high as -110dbm,
  • Compatible with HT12E and HT12D,
  • Low power and good range.
  • High-frequency stability and low coherence and interference
  • Easy interfacing with the RF modules, using the female headers for placing the modules.
  • Breakout pins for connecting to the microcontroller.
  • DIP Switch for Address Selection (when multiple modules are used at one location)
  • Status LED for valid transmit.
  • Supports both ASK, FSK RF modules
  • Small size, high quality PCB.

RF Transmitter Circuit:

The HT12E encoder IC converts 4-bit parallel data from four data pins into serial data for transmission over an RF link using a transmitter.

RF Receiver Circuit Diagram

RF receiver circuit diagram

The HT12D decoder IC translates serial data from an RF receiver into 4-bit parallel data and drives the output accordingly.

Applications:

  • Wireless security systems
  • Car alarm systems
  • Remote controls
  • Sensor reporting
  • Vehicle monitoring
  • Remote control
  • Telemetry
  • Small-range wireless network
  • Wireless meter reading
  • Access control systems
  • Wireless home security systems
  • Area paging
  • Industrial data acquisition system
  • Radio tags reading
  • RF contactless smart cards
  • Wireless data terminals
  • Wireless fire protection systems
  • Biological signal acquisition
  • Hydrological and meteorological monitoring
  • Robot remote control
  • Wireless data transmissions

I hope all of you are clear about what an RF transmitter and receiver is.We MATHA ELECTRONICS will be back soon with more interesting topics.

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