Segmental Analysis Method of Signal Frequency

In circuit analysis, it is often necessary to classify signals according to their frequency, divide the signal frequency into several cases, and then analyze the working principle of the circuit.

1. AC signal frequency band division method

In circuit analysis, the concept of signal frequency that needs to be mastered is the high and low frequencies (the relative high and low frequencies of signals). Frequency decomposition of AC signals is to divide the signal within the frequency band (the range between the highest frequency and the lowest frequency) into two or more smaller frequency bands, and then analyze the circuit working principles of the signals in different frequency bands.

The frequency of AC signals has different segmentation methods in different situations.

2. Segment analysis method for low, medium and high frequency signals

Figure 1-32 is a schematic diagram of the low, medium and high frequency signal segmentation analysis method.

According to the different signal frequencies in AC signals, AC signals are usually divided into three types: low-frequency signals, medium-frequency signals, and high-frequency signals for circuit analysis.

 
The low-frequency signal has the lowest frequency, the high-frequency signal has the highest frequency, and the intermediate-frequency signal has a middle frequency.

Obviously, low-frequency signals refer to signals in a certain frequency band within the low-frequency range. Strictly speaking, they should be low-frequency signals, commonly known as low-frequency signals. Similarly, intermediate-frequency signals and high-frequency signals are also signals in a certain frequency band.

3. A method for analyzing a signal with a specific frequency

Figure 1-33 is a schematic diagram of a specific frequency signal analysis method.

The AC signal is divided into signals of a certain specific frequency. Strictly speaking, there are two situations: signals within a frequency band centered on this frequency and signals of other frequencies outside this frequency band. Usually, the signal band centered on the frequency fo is very narrow.

This analysis method is mainly used to analyze the working principles of absorption circuits, bandpass filters and resonant circuits.

4. Low frequency, medium frequency and high frequency signal analysis methods

Figure 1-34 shows a schematic diagram of the low-frequency and medium- and high-frequency signal analysis method.
Taking a low-frequency signal of a certain frequency as the boundary, the AC signal is divided into two types according to the frequency, namely, low-frequency signal and medium- and high-frequency signal for analysis. This is often the frequency band decomposition method used when the low-frequency signal is specially processed in the circuit. [page]

This method is mainly used to analyze the working principles of circuits such as high-pass filters and frequency compensation.

5. Analysis methods for low, medium and high frequency signals
Figure 1-35 shows a schematic diagram of the analysis methods
for low, medium and high frequency signals. Taking a high frequency signal of a certain frequency as the boundary, the AC signal is divided into two types of low, medium frequency signals and high frequency signals according to the frequency for analysis. This is often the frequency band decomposition method used when high frequency signals are specially processed in the circuit.

This method is mainly used to analyze the working principles of circuits such as high-pass filters.

 6. In-band and out-band signal analysis method
Figure 1-36 shows a schematic diagram of the in-band and out-band signal analysis method.
The AC signal is divided into two types: valid in-band signals and out-band signals. The valid in-band signals are useful signals, and the out-band signals are usually useless signals and harmful.

Out-of-band signals are divided into out-of-band low-frequency signals and out-of-band high-frequency signals. The former has a frequency lower than the lowest frequency of the in-band signal, and the latter has a frequency higher than the highest frequency of the in-band signal.

7. Division and analysis method of bass, midrange and treble frequencies in audio signals

Audio signals are one of the most common signals in electronic circuits.

Figure 1-37 shows the division of bass signals, mid-range signals, and treble signals in audio signals. Usually, audio signals with frequencies below 500Hz are called bass signals, those with frequencies between 500 and 4000Hz are called mid-range signals, and those with frequencies above 4000Hz are called treble signals.

8. Frequency division of sub-bass and heavy bass in audio signals

In audio circuits, in order to further explain the bass, the low frequency band is often further divided, as shown in Figure 1-38, and the lowest two octaves are called sub-bass and heavy bass. The frequency band of sub-bass is 20-40Hz, and the frequency band of heavy bass is 40-80Hz. The sub-bass and heavy bass are collectively called super-heavy bass, and their frequency band is 20-80Hz.