In demodulation, the original signal can be obtained by multiplying the received modulated signal with the carrier signal. This method is called multiplicative demodulation.
Common pulse modulation techniques are:
Digital pulse modulation (DPM)
Digital pulse wideband modulation (DPWM)
Digital pulse frequency modulation
Digital pulse phase modulation (DPPM)
Among them, digital pulse modulation is the way that digital signals are directly multiplied by high-frequency carriers, while others modulate signals by changing the frequency, phase or width of carriers.
In addition, another commonly used pulse modulation technology is pulse code modulation (PCM). Its principle is to sample, quantize and encode the analog signal, and then multiply the obtained digital signal with the carrier signal for modulation. This method can effectively reduce the noise in the signal.
Pulse modulation technology has an important application in the field of communication, such as widely used to transmit voice, data, images and other information in telecommunications. In radio communication, it is also often used for long-distance radio transmission, radio broadcasting and navigation.
Excerpted from Principle of Pulse Modulation
Additional notes:
For pulse modulated signals, there is a difference between analog signals and digital signals. Analog signals are continuously changing, while digital signals are discrete. Analog signals usually need to be sampled by pulse modulation, quantized into digital signals and then modulated.
There are many kinds of pulse modulation circuits, which can be divided into many categories according to different modulation methods and application scenarios, such as:
Pulse width modulation (PWM): The pulse width of the carrier signal changes according to the amplitude of the signal. The larger the pulse width, the greater the signal amplitude.
Frequency modulation (FM): Change the frequency of the carrier signal according to the amplitude change of the signal. The higher the frequency, the greater the signal amplitude.
Phase modulation (PM): Change the phase of the carrier signal according to the amplitude change of the signal. The greater the phase, the greater the signal amplitude.
Digital Pulse Modulation (DPM): Modulates a digital signal by directly multiplying it with a high-frequency carrier.
There are other types of pulse modulation, such as pulse frequency modulation (PFM) and pulse phase modulation (PPM). These pulse modulation circuits play an important role in applications.
In addition, there are some advanced technologies, such as AM, FM and PM. Their applications cover broadcasting, television, radio navigation and other fields.