Question

What are high-level and low-level modulators?

Answer 1

Modulation

1. Modulation is a common communication system procedure in which a very high-frequency carrier wave is used to convey a low-frequency message signal, ensuring that the transmitted signal retains all of the information included in the original message signal.
2. The technique of superimposing a low-frequency signal over a high-frequency carrier signal is known as modulation.
3. Amplitude modulation is a type of modulation in which the amplitude of the carrier signal is adjusted in proportion to the message signal but the phase and frequency remain constant.
4. Phase modulation is a sort of modulation in which the carrier signal's phase is changed in response to the low frequency of the message signal.
5. Frequency modulation is a type of modulation in which the frequency of the carrier signal is changed in proportion to the message signal but the phase and amplitude remain constant.

High-level modulators:

1. A high-level modulator is one that modulates a circuit with a high power section, typically the final RF amplifier.
2. When the modulating voltage is delivered to the collector/plate circuit of the final power amplifier, high-level modulation occurs.
3. It has the advantage of not requiring linear amplifiers for the RF amplification stages after AM modulation.

Low-level modulators

1. In a Low-level Amplitude Modulation system, modulation is done at the low power of the carrier and modulating signal. Hence, the output power of modulation is low. As a result, power amplifiers are needed to increase the signal to the required level of power.
2. A low-level AM modulator is one that applies modulation to the transmitter's low power stages, typically in the RF generation stages or via the digital signal processing areas.
3. The disadvantage of this approach is that the RF stages require linear amplification.
4. Low-level modulation has the benefit of using less modulating signal strength to obtain a high percentage of modulation.