Here in this article you will see the block diagram and feature of a high quality FM radio receiver. FM radio receivers are very popular these days due to FM broadcast available all over. A good quality FM radio receiver is capable of producing quality audio which had been broadcast at the time of transmission. The receiver should be capable of receiving and producing stereo FM signal. This FM radio receiver is battery powered and is portable because it can be powered from a single 9V battery. A PP3 battery could do or a rechargeable battery could also work just fine. The power consumption of this radio is just moderate and battery could last for a few hours of listening. Dual power option is available if somewhere power line is available, the best choice to operate this radio could be the means power.
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| Supper FM 9 block diagram |
This Supper FM 9 radio receiver circuit is based on superheterodyne function. In superheterodyne design the radio signal is amplified and is fed back again in the input several times. This way the signal become very strong and very large to be better identified by the audio frequency stage. The signal from the antenna is fed to the band bass filter. Then this signal is few to the tuned RF amplifier where the channel selection is made and a particular frequency band is selected to output. The band selection is made by a varicap diode whose capacitance can be varied by applying reverse biasing of the diode. Such diodes are very common in modern tuning circuits where a voltage signal is used to make the tuning. There are common in digital type tuning circuits.
Next is the mixer stage where the signal is mixed with the local frequency oscillator frequency to obtain the difference of the two frequencies which would be exact 10.7MHz. Then the signal is fed to the next stage 10.7MHz band pass filter where any other unwanted signals are rejected and the desired 10.7MHz signal is fed to the next stage the IF amplifier stage. In IF amplifier stage the signal is amplified.
Next this signal is fed to the limiter and demodulator stage where the signal is seperated from the carrier. When the signal is separated from the carrier, the carrier is rejected and the only audio signal is few to the audio amplifier stage. Before sending the signal to the audio amplifier stage, the signal is fed to another stage the stereo signal detection where the signal is divided into two audio signals, L and R stereo signals. Then these L and R stereo signals are fed to two separate audio amplifiers where both L and R signals are amplifier to the the level so that two speakers could be driven by this audio signal.
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