Write it at the front
This is 【Matlab】BASK The simulation of modulation and demodulation of The second part of , Considering the reading experience , So I'm going to open another article to share BFSK The simulation of modulation and demodulation of .
Indexes
- Write it at the front
- One 、BFSK Modulation of
- 1.1 Different frequency carrier generation
- 1.2 Signal combination
- 1.3 Waveform Preview
- 1.4 Parameter setting （ Reference resources ）
- Two 、BFSK Demodulation of
- 2.1 Model structures,
- 2.2 Waveform Preview
- 2.3 Parameter setting （ Reference resources ）
- 3、 ... and 、 common problem
- At the end
One 、BFSK Modulation of
One FSK The signal can be seen as two different carriers BASK Superposition of signals ,BFSK The spectrum of the signal can be seen as \(f_1\) and \(f_2\) Two BASK The combination of spectrum .
Frequency shift keying is the use of carrier frequency to transmit digital signals , stay BFSK in , The carrier frequency varies with the binary baseband signal \(f_1\) and \(f_2\) Between two frequency points , Frequency shift keying (FSK) uses the frequency shift of carrier to transmit digital information . So the expression is ：
BFSK There are two kinds of modulation modes of the , They are analog frequency modulation and keying . This article uses keying , adopt Simulink Conduct simulation . The schematic diagram of the keying method is shown in the figure below ：
1.1 Different frequency carrier generation
according to BFSK Signal expression , We need to prepare two different frequency carriers . In order to generate different frequency carrier , We will BASK In modulation model Signal Geneator Replace with Sine Wave. in addition , In order to reflect 01 Characteristics of signal , 需要使曼彻斯特码的其 in One 通道经过非门 NOT, And then through the multiplier .
1.2 Signal combination
Observe 1.1 Oscillogram in , We can easily draw a conclusion ：BFSK The modulation signal is generated by the 0 code BFSK Modulation signal and 1 code BFSK Sum of modulated signals . So we let two different frequency carriers pass through Sum You can get the complete BFSK Modulation signal .
For model visibility , I will 0 code BFSK Modulation signal and 1 code BFSK The modulation signal is packaged .
1.3 Waveform Preview
Use Scope modular , We can observe the waveform of the signal in each stage . Put the Manchester code and BFSK The modulated signal is connected to the oscilloscope , We can see the figure below ：
1.4 Parameter setting （ Reference resources ）
We can adjust the parameters of each module to control BFSK Shape of modulated signal , The reference parameters of each module are given below ：
| Module name | Parameters | Set the value |
|---|---|---|
| Pulse Generator | Period (secs) | 1 |
| Pulse Width (% of period) | 50 | |
| Sine Wave 0b | Frequency (rad/sec) | 12*pi |
| Sine Wave 1b | Frequency (rad/sec) | 24*pi |
notes ： Module parameters not listed are processed by default .
Two 、BFSK Modulation of
BFSK There are two ways to demodulate , They are coherent demodulation and incoherent demodulation . Coherent demodulation is used in this paper , adopt Simulink Conduct simulation . The schematic diagram of coherent demodulation is shown in the figure below ：
Let's use Matlab/Simulink Implement the model step by step .
2.1 Model structures,
stay Simulink in , We can use Analog Filter Design To replace band-pass filter and low-pass filter , use Sine Wave Output same frequency demodulation carrier , use GreaterThanOrEqual Instead of sampling decider and sampling pulse . The specific model is as follows ：
2.2 Waveform Preview
Use Scope modular , We can observe the waveform of the signal in each stage . Manchester code 、BFSK Modulation signal and BFSK The demodulated signal is connected to the oscilloscope , We can see the figure below ：
2.3 Parameter setting （ Reference resources ）
The reference parameters of each module are given below ：
| Module name | Custom name | Parameters | Set the value |
|---|---|---|---|
| Analog Filter Design | Bandpass Filter 0b | Filter type | Bandpass |
| Lower passband edge frequency (rad/s) | 12*pi-20 | ||
| Upper passband edge frequency (rad/s) | 12*pi+20 | ||
| Bandpass Filter 1b | Filter type | Bandpass | |
| Lower passband edge frequency (rad/s) | 24*pi-20 | ||
| Upper passband edge frequency (rad/s) | 24*pi+20 | ||
| Lowpass Filter 0b | Passband edge frequency (rad/s) | 10*pi | |
| Lowpass Filter 1b | Passband edge frequency (rad/s) | 23*pi | |
| Sine Wave | Sine Wave | Frequency (rad/sec) | 12*pi |
| Sine Wave1 | Frequency (rad/sec) | 24*pi | |
| GreaterThanOrEqual | GreaterThanOrEqual | Relational operator | < |
notes ： Module parameters not listed are processed by default .
3、 ... and 、 common problem
Q： Sine wave distortion is encountered during simulation （ Including amplitude and shape ）, What to do with ？
A： If sine wave distortion is encountered in the simulation process （ Including amplitude and shape ）, Can be in Simulink Right click the blank space of the project , choice Model Configuration Parameters, After entering the page , On the tab Solver -> Solver details The following parameters are set in ：
| Parameters | Set the value |
|---|---|
| Max step size | 1e-5 |
| Relative tolerance | 1e-5 |
.
At the end
It's been a busy few weeks , It took a day to finish this article , But I had to finish it by Thursday Orz
I hope this essay and sister essay can help you ~