Analog signal processing refers to the various operations and adjustments of analog signals (continuously changing signals) in order to efficiently transmit, enhance, filter, or convert into other forms of signals. Analog signal processing includes a number of key steps and techniques, the specific process and method may vary depending on the application scenario, but usually includes the following main steps:
1. Signal collection
Sensor/Source device: Analog signals are usually derived from some phenomenon of the physical world, such as temperature, sound, pressure, etc. For example, temperature sensors, microphones, accelerometers and other devices can convert physical quantities into analog signals.
Input signal: The signal at this stage is usually the original analog signal, such as a continuous change in voltage or current.
2. Amplification (gain)
Amplifier: If the amplitude of the signal is small, it may be necessary to use an amplifier to increase the strength of the signal. Gain adjustment ensures that the amplitude of the signal is appropriate for subsequent processing or transmission.
Operational amplifier: In many analog signal processing, a common device is the operational amplifier (Op-Amp), which can be used to amplify weak analog signals.
3. Filtering
Filters: Analog signals are often disturbed by noise or unwanted frequency components, so filters are needed to remove these disturbances. Filters can be:
Low-pass filter: allows low-frequency signals to pass through and blocks high-frequency signals (such as removing high-frequency noise).
High-pass filter: allows high frequency signals to pass through and blocks low frequency signals (such as removing DC offset).
Bandpass filter: Only allows signals within a certain frequency range to pass through, often used in radio, audio and other applications.
Band-stop filter: removes signals from a specific frequency range, usually used to remove interference from a specific frequency.
The purpose of filtering is to clear the signal, remove unnecessary frequency components or noise, and improve the quality of the signal.
4. Modulation and demodulation
Modulation: The process of modulation is the conversion of the original signal into a form suitable for long-distance transmission. Common modulation methods are:
Amplitude modulation (AM) : Information is transmitted by changing the amplitude of the signal.
Frequency modulation (FM) : The transmission of information by changing the frequency of the signal.
Phase modulation (PM) : Information is transmitted by changing the phase of the signal.
Demodulation: Demodulation is the reverse processing of the modulated signal by the receiver to restore the original analog signal.
5. Analog signal conversion (if necessary)
Analog-to-digital conversion (ADC) : If the Analog signal requires further Digital processing or storage, it is first necessary to convert the analog signal to a digital signal via an analog-to-digital Converter (ADC).
This process converts continuously changing analog signals into discrete digital signals, which are convenient for further processing by computers or digital systems.
Common types of ADCs are successive approximation (SAR), serial (Sigma-Delta), and so on.
Digital-to-analog conversion (DAC) : Digital signals can also be converted to Analog signals using a digital-to-analog Converter (DAC). For example, in a digital audio playback device, the digital audio signal needs to be converted to an analog signal by a DAC to drive the speaker.
6. Signal enhancement and processing
Gain control: Depending on the strength of the signal, dynamic range control of the signal may be required to ensure that the gain of the signal is not too strong or too weak.
Linear/nonlinear processing: In some applications (such as audio processing, sound amplification, etc.), the signal may require nonlinear processing (such as distortion effects, compression, etc.).
7. Signal output and transmission
The processed signal can be output directly to back-end devices such as drive motors, displays, speakers, etc., or sent to remote locations via analog transmission lines.
When transmitted over long distances, analog signals may be subject to attenuation and noise interference, so they often need to be optimized using techniques such as modulation, amplification, and filtering.
8. Common analog signal processing applications
Audio processing: including audio amplifiers, equalizers, effects and other equipment to process sound signals, such as audio signal enhancement and filtering in the sound system.
Wireless communication: In radio, television broadcasting and other fields, analog signals need to be modulated and demodulated.
Biomedical signals: such as electrocardiogram (ECG), electroencephalogram (EEG) and other signals acquisition, filtering, amplification and analysis.
Industrial control: such as analog signals collected by sensors (temperature, pressure, flow, etc.) and used to control the input of the system.
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