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A superheterodyne receiver is a receiver that maximizes both sensitivity and selectivity. Normally, these are conflicting goals, and in a single stage, you can only get one, but not both. The difficulty is that you cannot build a high gain RF stage with enough selectivity to reject adjacent signals. The superheterodyne process solves this problem.

First, the RF stage is built for high gain, but it is not very selective. It might have some tunability, i.e. selectivity, but that is not its primary objective.

Second, there is a local oscillator that is tuned to a frequency some distance away from the primary signal's carrier. In a standard AM receiver, that distance is 455 KHz; in a standard FM receiver, that distance is 10.7 MHz.

Third, the amplified RF signal and the local oscillator are mixed together. Recall from Fourier analysis that when you mix two signals together you get four signals; the two original signals, their sum, and their difference. We are interested in their difference. Basically, the output of the mixer contains the original signal downshifted to either 455 KHz or 10.7 MHz.

Fourth, we have an IF stage that is tuned around 455 KHZ or 10.7 MHz. The IF stage is highly optimized for operation at one range of frequencies, and can therefore be highly selective. Usually, the IF stage is three bandpass filters, each tuned slightly differently, so that the end result is a bandpass filter that is wide enough to pass the entire bandwidth of the original signal, 20 KHz for AM and 100 KHz for FM.

Fifth, we have the demodulator. At this point, we retrieve the signal and either just amplify it (AM) or further decode it for stereo (FM).

The end result is that we got sensitivity in the RF stage and selectivity in the IF stage, along with tunability in the local oscillator. That is the superheterodyne process.
A very common type of radio receiver. The output from a simple radio aerial will be of the order of a microvolt or so, and the output desired is a few volts. So an amplification of a million or so is needed. This is achieved by multiple stages of amplification - each generally of less than 100 times. And we need to be able to tune over a range of 3:1 for the Broadcast Band, and perhaps greater for some other bands.

For technical reasons concerning the mechanics of tuning, this is more easily achieved at a single frequency - typically about 0.5 MHz. The alternative would be to have the same number of stages of amplification but each with its own tuning. Mechanically much more difficult.

So, the incoming signal from the aerial is mixed in a mixer stage, along with an internally generated signal. [This mixer stage is a non-linear process, and as a result, produces a complex output, of both the input frequencies, the sum of them, and the difference between them. ] The difference frequency is selected - the 0.5MHz above.

So the mixer stage is followed by several intermediate stages of amplification operating at the 0.5 MHz, - where most of the amplification takes place.

This is then followed by a demodulator (detector) stage, which separates the audio signal from the carrier signal. And followed in turn by an audio amplifier stage which feeds the loudspeaker.

The 'hetrodyne' part of the name refers to the mixing of the signals at the mixer stage. For radios operating at higher frequencies than the broadcast, the Intermediate stage will commonly operate at 10MHz or so.

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Q: What is a superheterodyne receiver?
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Why TRF receiver was replaced by superheterodyne?

Superheterodyne is:more sensitive than TRFmore selective than TRFeasier to tune than TRFeliminates the squeal that sometimes happens with TRFis easier to adapt to FM and TV reception than TRFcan be adapted for use with microwave signals to up/down convertetc.


Why you use 455kHz frequency as an intermediate frequency in communication?

The intermediate frequency in the superheterodyne receiver is chosen as the desired compromise between sensitivity and selectivity. 455kHz is used in AM broadcast applications, while 10.7mHz is used for FM. The IF stage is tuned for a steep skirt passband at that frequency, allowing only the desired heterodyned (shifted) input signal to make it through to the demodulator.


Why intermediate frequency transformers are used in modulation process?

They are used as adjustable bandpass filters in superheterodyne (Google it) recievers. They determine how well you can select the radio station you require, while rejecting those close to it. They work in a fixed frequency range where their characteristics can be optimised.Very many modern radio recievers use some form of the superheterodyne principle though the function of the IF Transformer (ie bandpass filter) can be realised digitally, as in mobile phones for example. For AM radio a bandwidth of 9 KHz at 450KHz is typical.


What is broadcast receiver?

A broadcast receiver is a radio that receives broadcasts from commercial radio stations.


The receiver will be able to decode the message if the transmitter and receiver share the same?

traffic encryption key

Related questions

What is the disadvantageand advantage of Superheterodyne receiver?

can a superheterodyne receiver generated high noise


What is the importance of Intermediate Frequency stage of the superheterodyne receiver?

for better output,and low impedance.!@


Intermediate frequency amplifier in a TV receiver?

Is this sentence supposed to be question? Any superheterodyne receiver will have an IF amplifier. It doesn't matter whether TV or radio.


What are the 4 parts to a receiver?

radio frequency amplifier intermediate frequency( If strip) in a superheterodyne radio mixer /demodulator Audio amplifier


What is Double conversion receiver?

A type of superheterodyne radio using two separate mixers, each producing its own intermediate frequency. The block diagram of such a receiver is like this: RF -> M1 -> IF1 -> M2 -> IF2 -> D -> AF


What is the double conversion receiver?

A type of superheterodyne radio using two separate mixers, each producing its own intermediate frequency. The block diagram of such a receiver is like this: RF -> M1 -> IF1 -> M2 -> IF2 -> D -> AF


Why TRF receiver was replaced by superheterodyne?

Superheterodyne is:more sensitive than TRFmore selective than TRFeasier to tune than TRFeliminates the squeal that sometimes happens with TRFis easier to adapt to FM and TV reception than TRFcan be adapted for use with microwave signals to up/down convertetc.


How are electrical signals turned into data in microwave transmission?

This is usually done by modulating a much lower frequency carrier with the signal, then superheterodyning this carrier upconverting it into the desired microwave band. A corresponding superheterodyne receiver downconverts the microwave signal to a lower intermediate frequency which is then demodulated to recover the original signal.


What is a super heterodyne receiver?

A superheterodyne receiver is a Radio Frequency receiver method that multiplies the received signal frequency with a local oscillator frequency to get frequencies that are the sum and difference of the 2 frequencies. For example, if the received signal is 5MHz and the local oscillator frequency is 4MHz, they are multiplied together. 1MHz and 9MHz frequencies would be gotten. Usually the 1MHz is the Intermediate Frequency (IF). It will be admitted (through a band pass filter) later passed through the required electronic circuits for proper processing. There is also the method of the Variable Tuned Filter.


What is super heterodyne receiver?

A superheterodyne receiver is a Radio Frequency receiver method that multiplies the received signal frequency with a local oscillator frequency to get frequencies that are the sum and difference of the 2 frequencies. For example, if the received signal is 5MHz and the local oscillator frequency is 4MHz, they are multiplied together. 1MHz and 9MHz frequencies would be gotten. Usually the 1MHz is the Intermediate Frequency (IF). It will be admitted (through a band pass filter) later passed through the required electronic circuits for proper processing. There is also the method of the Variable Tuned Filter.


What is the difference between a Superheterodyne and a Neutrodyne radio receiver?

The superheterodyne converts the desired incoming signal frequency to an (usually lower) intermediate frequency before demodulating it and extracting the audio signal (or video/data, etc).The neutrodyne is a tuned radio frequency design where all amplifying stages operate at the incoming signal frequency. This was the commonest design up to the 1930s. The triode amplifiers used suffered from signal feedback, where a signal from the amplifier's output was coupled back to its input. This could cause the amplifier to act like a transmitter and to oscillate. Neutralization (with capacitors) was invented to prevent this problem and the circuit was named the "neutrodyne".


What are oscillators used for?

Signal generators: reference (tuning equipment) source - such as electronic keyboards beat frequencies - as in a superheterodyne radio