What Are the Different Types of FM Radio Advertising?

FM (Frequency Modulation) is frequency modulation. It is customary to use FM to refer to general FM broadcasting (76-108MHz, 87-108MHz in China and 76-90MHz in Japan). In fact, FM is also a modulation method, even in the short-wave range. Between 27-30MHz, as a band for amateur radio, space, satellite communications applications, there are also frequency modulation (FM) mode. ^[1]

Frequency modulation (FM) at

In simple frequency modulation, only two oscillators are used

Composite frequency modulation includes two or more carrier body oscillators and two or more modulator body oscillators, which can generate more side frequencies and increase the computational complexity. There are many possible combinations of composite frequency modulation, and each combination will bring unique frequency combining effects.

There are at least the following five basic combinations of composite frequency modulation:

1.Multi-carrier combination with independent modulators

(Additive carriers with one modulator)

This combination includes two or more simple FM instruments working at the same time. The effect obtained is the sum of the output of each FM instruments (in the legend abbreviation, al indicates the amplitude of carrier 1, fl indicates the frequency of carrier 1, and d1 indicates modulation The frequency offset of the body 1 is the amplitude of the modulation body 1, f1 represents the frequency of the modulation body 1, and a represents the carrier amplitude.

Multi-carrier combination with only one modulator

(Additive carriers with one modulator)

The effect it obtains is the sum of the outputs of each carrier.

3.Single carrier with parallel modulator

(Single carrier with parallel modulators)

4. Single carrier with multiple (stepwise) modulators

(Single carrier with serial modulators)

5.Self-modulated carrier

(Self-modulating carrier)

The so-called self-modulating carrier is to modulate its own frequency with the output of the signal oscillator. The output signal of the oscillator is multiplied by a feedback factor (represented by fb), and a frequency value (fm) is added before being re-input to its own frequency input. The feedback factor (represented by fb) can be seen here as a

FM Fundamentals

FM communication is the use of frequency modulation to complete the modulation to complete the communication. FM modulation has good anti-noise performance and transmits voice signals without distortion. Wireless FM modulation uses an LC resonant circuit composed of discrete components.

FM short wave frequency modulation technology

Compared with the original signal spectrum, the frequency spectrum can be increased to twice the original spectrum after applying FM technology. Using short-wave frequency modulation technology, the fidelity of communication quality can be improved. If it encounters large interference, it can also ensure the signal stability and reliability. ^[5]

In order to make the short-wave frequency modulation technology play a role in short-wave communication, more auxiliary technologies are used, including auxiliary antenna adaptive zero adjustment, adaptive modulation and demodulation, adaptive frequency selection technology, and the like. With such auxiliary technology, the performance of short-wave communication has been greatly improved, including anti-interference and anti-fading have been greatly improved, so it meets the requirements of continuous and uninterrupted communication. ^[5]