Fundamental Of Communication System Of Radio Transmitter (AM/FM)” In order better understand the way the radio transmitter works. Block diagram of a simple AM (amplitude modulated) signal transmitter is shown in poc.2.2. The amplitude modulation is being performed in a stage called the modulator. Two signals are entering it. High frequency signal called the carrier (or the signal carrier).
Fundamental Of Communication System Of Radio Transmitter (AM/FM)” Being created into the HF oscillator and amplified in the HF amplifier to the required signal level. And the low frequency (modulating) signal coming from the microphone or some other LF signal source (cassette player, record player, CD player, CD player, etc.) being amplified in the LF amplifier. On modulators output the amplitude modulated signal UAM is acquired. This signal is then amplified in the power amplifier, and then led to the emission antenna.
Fundamental Of Communication System Of Radio Transmitter (AM/FM)
Block diagram of an FM frequency modulated transmitter is given on pic.2.4. Information being transferred. i.e the modulating signal is a signal from some LF source. It is being amplified in LF amplified in LF amplifier and then led into the HF oscillator. Where the carrier signal is being created.
Fundamental Of Communication System Of Radio Transmitter (AM/FM)” The carrier is a HF voltage of constant amplitude whose frequency is in the absence of modulating signal equal to the transmitter’s carrier frequency fest. In the oscillatory circuit of the HF oscillator a vertical capacities diode is located. It is a diode whose capacitance depends upon the voltage between its ends, so when being exposed to LF voltage, its capacitance is changing in accordance with this voltage. Due to that frequency of the oscillator is also changing, i.e. the frequency modulation is being proceeded to the power amplifier that provides the necessary output power of the transmission signal.
Transmission is the process of sending and propagating an analogue or digital information signal over a physical point to point or point to multipoint transmission medium, optical fiber or wireless.
Block diagram of S.H. Radio Receiver (AM):-
A super heterodyne receiver (often shortened to super het) uses frequency mixing to convert a received signal to a fixed intermediate frequency (IF) which can be more conveniently processed than the original radio carrier frequency. It was invented by US engineer Edwin Armstrong in 1918 during world war.
Principle of Heterodyning Action:-
The super heterodyning (short for supersonic heterodyne) receiver was first evolved by major Edwin Howard Armstrong in 1918. It was introduced to the market place in the late 1920 and gradually phased out the TRF receiver during the 1930.
The principle of operation in the super heterodyne is illustrated by the diagram in figure 4. In this system. The incoming signal is mixed with a local oscillator to produce sum and difference frequency components.
The lower frequency difference component called the intermediate frequency (IF) is separated from the other components by fixed tuned amplifier stages set to the intermediate frequency.
The tuning of the local oscillator is mechanically ganged to the tuning of the signal circuit or radio frequency (RF) stages so that the difference at intermediate frequency is always the same fixed value. Detection takes place at intermediate frequency instead of at radio frequency as in the TRF receiver.
Modulation is the process of varying one or more properties of a periodic waveform called the carrier signal with a modulating signal that typically contains information to be transmitted.