Comparison of several common modulation methods for wireless modules

At present, there are many types of common wireless module on the market. The differences between them are often reflectedin the supported frequency, maximum rate, modulation method, power consumption,etc. This article compares several modulation methods commonly used in wireless module.

ASK definition

ASK is short for Amplitude Shift Keyingmodulation. For example, binary, and the binary symbols 0 and 1 are representedby different amplitudes respectively, which is ASK.

"Amplitude Shift Keying", also known as "Amplitude Shift Keying", is called ASK, and is a common method of modulation technology. If the possible state of the digital modulation signal corresponds to the binary information symbol or its corresponding baseband signal state one-to-one, the modulated signal is called a binary digital modulation signal. Keying with binary information symbols is called binary amplitude keying and is represented by 2ASK.

Shift Keying Schematic

In the “amplitude shift keying” mode, when “1” appears, the carrier with amplitude A is turned on, and when “0” appears, the carrier is turned off. This is equivalent to moving the original baseband signal (pulse train) spectrum to side.

Amplitude shift keying (ASK) is equivalent to amplitude modulation in an analog signal, except that it is a binary number multiplied by a carrier frequency signal. Amplitude shifting uses frequency and phase as constants andamplitude as variables. Information bits are transmitted through the amplitudeof the carrier. Binary amplitude keying (2ASK), because the modulation signalhas only two levels of 0 or 1, the result of the multiplication is equivalent to turning the carrier frequency off or on. The practical significance is that when the modulated digital signal is "1 ", The carrier is transmitted; when the modulated digital signal is" 0 ", the carrieris not transmitted. The principle is shown in Figure 1, where s (t) is a baseband rectangular pulse. Cosine signals are generally used for carrier signals, and modulated signals are used to convert digital sequences intounipolar baseband rectangular pulse sequences, and the role of this on-offkeying is to multiply this output by the carrier to shift the spectrum to thecarrier frequency. Nearby, realize 2ASK. The realized 2ASK waveform is shown inFigure 2.

2ASK waveform

The simplest and most commonly used form of amplitude modulation keying for this modulation technique is switching. The presence of a carrier isrepresented by a "1" and the absence of a carrier is represented by a"0". This type of modulation is called on-off keying (OOK), and it is the