FM amplitude modulation is what each serves

There is no difference, each has its own advantages and disadvantages.

1. Under the same frequency, power, etc., the transmission of signals by frequency modulation is much farther than that of amplitude modulation. Because the carrier frequency level of the amplitude modulation mode must be three or forty decibel higher than the noise level to obtain a good image index, and the frequency modulation mode only needs to be a few decibel higher than the noise level.

Frequency modulation is stronger than amplitude modulation anti-interference ability: the impact of various external interference, processing industry and celestial power interference on the modulated wave is mainly manifested in the generation of parasitic amplitude modulation and the formation of noise. The FM system can use the method of limiting to eliminate the parasitic amplitude modulation caused by interference.

However, the amplitude of the amplitude modulated signal in the amplitude modulation system is variable, so the amplitude limiting cannot be used, and it is difficult to eliminate external interference.

3. In addition, the larger the signal-to-noise ratio of the signal, the stronger the anti-interference ability. The signal-to-noise ratio of the demodulated signal is related to the modulation coefficient, and the larger the modulation coefficient, the greater the signal-to-noise ratio. Because the frequency modulation coefficient is much larger than the amplitude modulation coefficient, the signal-to-noise ratio of the FM wave is high, and the interference noise in the FM broadcast is small.

4 Frequency modulated wave ratio amplitude modulated frequency bandwidth.

The selling rock in the FM market does not mean the following:

By definition, the frequency modulation market is defined for the electricity market, specifically referring to automatic generation control, that is, secondary frequency modulation auxiliary services.

Frequency modulation is the earliest market for the commercial application of energy storage, and after energy storage enters the frequency modulation market, the cost of electricity services paid by users can be greatly reduced, which exists in Germany, Australia, the United Kingdom and even China.

Features of secondary frequency modulation:

Manual frequency modulation: in the frequency modulation plant, the operator adjusts the early output of the generator according to the change of the system frequency, so that the frequency is kept within the specified range, the characteristics of manual frequency modulation is that the reflection speed is slow, and when the adjustment amplitude is large, it often cannot meet the requirements of frequency quality, and the personnel on duty operate frequently and the labor intensity is large.

Auto Modulation: This is the modern power system.

The frequency modulation mode adopted, automatic frequency modulation is to automatically increase or decrease the power generation output of the generator through the automatic device installed in the power plant and the dispatching center with the change of system frequency, keep the system frequency fluctuating in a small range, automatic frequency modulation is a component of power system dispatching automation, it has the comprehensive functions such as completing frequency modulation, power control between systems and contact line exchange, and economic scheduling.

1.Amplitude modulation and frequency modulation are the most common in radio, and amplitude modulation is modulation (AM) that makes the frequency of a high-frequency carrier change with a signal. In its detection, the amplitude of the carrier signal changes with the transformation of a certain characteristic of the modulated signal.

Frequency modulation is modulation (FM) that changes the frequency of the carrier wave according to the modulated signal. The magnitude of the change in the modulated frequency is determined by the size of the modulated signal, and the period of change is determined by the frequency of the modulated signal, and the anti-interference ability of the frequency modulation is strong, and the distortion is small, but the service radius is small, and the frequency modulation is stronger than the amplitude modulation anti-interference ability 2, and the frequency frequency band is related to the modulation coefficient, that is, the modulation coefficient is large, and the frequency bandwidth.

In frequency modulation, the frequency modulation coefficient is often greater than 1, and the amplitude modulation coefficient is less than 1 (greater than 1 is overmodulated, which will be seriously distorted), so the frequency band width of the frequency modulation wave is much larger than the frequency band width of the amplitude modulation wave. Therefore, the sound quality should be good, the upper limit of the audio can reach about 10kHz 3, the utilization rate of the frequency modulation system power is greater than the amplitude modulation system In the total transmitting power, the side frequency power is the effective power of the transmission modulation signal, and the side frequency power is related to the modulation coefficient. Because the frequency modulation coefficient mf is greater than the amplitude modulation coefficient ma, the power utilization rate of the frequency modulation system is higher than that of the amplitude modulation system.

4. Because the frequency modulation wave is more than the amplitude modulation frequency bandwidth, it also brings the problem of selectivity, so it is not suitable for use in the low-frequency spring brother section of the radio frequency, and the band of about 100m is often used. The characteristics of this band propagate in a straight line, so the radius of propagation is relatively small I know that, I haven't touched it for a few months, you can systematically learn "High Frequency Electronic Technology".

Frequency modulation, the full name is "frequency modulation". It is a modulation method that makes the instantaneous frequency of the carrier change according to the change law of the signal to be transmitted.

The circuit of the modulation method of FM is called a frequency modulator, which is widely used in FM radio, television accompaniment, microwave communication, phase-locked circuit and frequency sweeper.

If an electrical signal in this frequency range is directly radiated, both the transmitting and receiving devices are harsh. These requirements require a large size tangerine antenna to transmit and receive electromagnetic waves. At the same time, relatively low-frequency electromagnetic waves have poor immunity to interference and interfere with each other during transmission and reception.

The radio side produces a lot of noise, so that the listener hears the sound or signal is completely buried in the noise.

Therefore, in order to reduce the hardware requirements of the indiscriminate transmitting and receiving equipment and improve the anti-interference performance, the collected electrical signals are usually loaded onto the high-frequency sine wave signals for transmission and reception. The acquired electrical signal is called the baseband signal, the high-frequency sine wave is called the carrier wave, and the process of loading the baseband signal onto the carrier wave is called modulation.

Inventor of frequency modulation

In the history of the development of radio communication, Armstrong's English name is familiar to people, and his invention of the frequency modulation method in 1933 created a new high-quality communication method - FM broadcasting, and began a new era of high-fidelity high-quality broadcasting. In addition to amplitude modulation, there are also frequency modulation, as well as pulse code modulation (PCM) invented by Ribbs in 1937.

The above content refers to Encyclopedia - FM.

Frequency modulation and amplitude modulation are two common analog modulation techniques.

Frequency modulation refers to changing the frequency of a signal to transmit information. In frequency modulation, the frequency of the carrier signal is modulated, changing as the signal changes. FM can achieve high-quality audio transmission, so it is widely used in broadcasting, radio communication and audio equipment.

The FM signal is characterized by strong anti-interference ability and relatively stable transmission quality.

Amplitude modulation refers to changing the amplitude of a signal to transmit information. In amplitude modulation, the amplitude of the carrier signal is modulated and changes as the signal distribution changes. Amplitude modulation is generally used for the transmission of low-frequency signals, including voice and audio signals.

Amplitude modulation signals are characterized by being relatively simple, but sensitive to noise and interference, and have relatively short transmission distances.

Frequency modulation and amplitude modulation have their own application scenarios in signal transmission. FM is suitable for the transmission of high-quality audio, such as radio stations and audio equipment; Amplitude modulation is suitable for the transmission of low-frequency signals, such as AM broadcasting and voice communication. In addition, FM and AM have some other characteristics and applications, such as anti-interference ability, spectrum utilization efficiency, etc., which make them play an important role in different communication needs.

is a modulation method used in electronic communications, most commonly used for radio carriers to transmit information. In amplitude modulation, the amplitude (signal strength) of the carrier wave varies proportionally to the transmitted wave.

For example, the waveform may correspond to the sound reproduced by the speaker, or it may correspond to the light intensity of the TV pixels. This method is contrasted with frequency modulation for carrier frequency variations, and phase modulation for phase variations of homogeneous branches.

Frequency modulation (abbreviation: FM) is a modulation method that represents information in terms of the instantaneous frequency change of the carrier wave.

The corresponding amplitude modulation method is to represent the information through the change in the amplitude of the carrier, while its frequency remains the same. ）

In analog applications, the frequency of the carrier wave varies directly in equal proportion to the amplitude of the input signal. In digital applications, the frequency of the carrier is discretely transitioned according to the value of the data serial, the so-called frequency keying (FSK).