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Why is it that the RF section and the local oscillator are ganged tuned?
There is a fixed difference in frequency between the local oscillator and the RF amplifier at all times. This difference in frequency is the IF. This fixed difference and ganged tuning ensures a constant IF over the frequency range of the receiver.
What is RF carrier oscillator?
The term carrier wave originated with radio. In the transmitter, an electronic oscillator generates a sinusoidal alternating current of radio frequency; this is the carrier wave. The information signal is used to modulate the carrier wave, altering some aspects of the carrier, to impress the information on the wave.
Why local oscillator frequency is greater than carrier frequency?
As a listener tunes across the broadcast band, the local oscillator is also tuned in synchronism so as to precisely produce a single-frequency signal (essentially an unmodulated carrier signal) which is higher in frequency by 455 kHz in comparison to the incoming signal.
Which oscillator is used as local oscillator in radio receiver?
triode
The triode is used as the local oscillator, and the pentode is used as the mixer.
What is the local oscillator frequency?
In electronics, a local oscillator (LO) is an electronic oscillator used with a mixer to change the frequency of a signal. This frequency conversion process, also called heterodyning, produces the sum and difference frequencies from the frequency of the local oscillator and frequency of the input signal.
What is RF and IF signal?
An RF (or IF) mixer (not to be confused with video and audio mixers) is an active or passive device that converts a signal from one frequency to another. These three ports are the radio frequency (RF) input, the local oscillator (LO) input, and the intermediate frequency (IF) output.
What are the 2 advantages of heterodyning?
Benefits or advantages of Superheterodyne Receiver The devices are cheaper at such lower frequencies compare to higher frequencies. ➨It is easy to filter IF signal compare to RF signal. ➨It offers better sensitivity compare to homodyne receiver architecture.
Why do we need a local oscillator?
Is the local oscillator higher than the carrier frequency?
In most cases the local oscillator frequency is made higher than that of the required carrier so that Fig. 9.26. A superhet receiver. where fLO is the local oscillator frequency, fS is the r.f. signal carrier frequency and fIF is the intermediate frequency.
What is the output of a local oscillator?
The inputs to the mixer are the signal at the radio frequency and the sinusoid from a local oscillator (LO). The output is the signal at the intermediate frequency. Mixing is the process of multiplying the RF signal by the local oscillator and then low-pass filtering the product.
Where are the Lo and RF signals applied?
The LO and RF signals are applied to the two ports. Diode mixers are in each of the remaining two ports. At one diode, the sum of the RF and LO signals appears, and at the other diode is the difference of the two signals. The two diode mixers should have the same characteristics and be well matched.
How does mixing affect the local oscillator signal?
Mixing is the process of multiplying the RF signal by the local oscillator and then low-pass filtering the product. The conversion process of a mixer will cause a loss known as conversion loss, which is defined as: