Why local oscillator is used in AM?
If the frequency of this local oscillation signal is not accurate, the frequency of the frequency-converted signal will deviate from the center frequency of the intermediate frequency bandpass filter. For this reason, local oscillation signals are required to have high accuracy and low frequency fluctuation.
What is local oscillator in AM receiver?
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 are the 3 types of amplitude modulation?
Types of Amplitude Modulation
- Double sideband-suppressed carrier modulation (DSB-SC).
- Single Sideband Modulation (SSB).
- Vestigial Sideband Modulation (VSB).
How does a distortion analyzer work?
Distortion analyzers inject a low distortion sine wave into the input of the DUT and then extract that signal somewhere downstream from that point. The signal is fed into a very sharp notch filter to null out only the original sine wave frequency.
What are the two types of AM transmitters?
The two types of AM transmitters that are used based on their transmitting powers are: High level transmitters use high level modulation, and low level transmitters use low level modulation. The choice between the two modulation schemes depends on the transmitting power of the AM transmitter.
What is the difference between high level transmitter and low level transmitter?
The low-level AM transmitter shown in the figure (b) is similar to a high-level transmitter, except that the powers of the carrier and audio signals are not amplified. These two signals are directly applied to the modulated class C power amplifier.
How to measure harmonic distortion?
Measurement of harmonic distortion can be carried out by feeding a sine wave into the input of the device and separating the sine wave from its harmonics at the output. Distortion is measured as the ratio of harmonic level to the level of the fundamental frequency. This is usually expressed as a percentage but sometimes also expressed as a decibel.