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Sound signal spectrum analyzer
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Application background Signal frequency, amplitude and phase estimation(1) frequency (periodic) detectionIn the periodic signal, the time domain waveform analysis can be used to determine the period of the signal, which is to calculate the time difference of the adjacent two signal peaks, or the time difference of zero crossing. The time difference (T) of zero crossing (TI) is used in this period. The frequency is f = 1/T, since it is able to obtain multiple T values (TI), so the average value is used as the estimated value of the period.(2) amplitude detectionIn one period, the difference of Ymin and the minimum value of ymax is A = (Ymin - /2) A, and the ymax and Ymin of first A values are not found in one cycle. Key Technology (1) audio signal input, input from the sound card, input from the WAV fi
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Discrete-time Fourier transform
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Application background In MATLAB, any signal (vector) must be a finite length, which is the first point to be a problem. Therefore, it is not possible to use DTFT to calculate the infinite length signal MATLAB. There is a notable exception to the case, when the analytical formula can be derived from the transformation definition and only when it is calculated, the MATLAB can be used to calculate the infinite length DTFT. Key Technology 1 pulse signal DTFTUsing the DTFT function to calculate the 12 point pulse signal DTFT. Draw in the area between the DTFT W. Separate the real and imaginary parts, but note that these are not very useful. The amplitude of the DTFT. When drawing, note that the variable of the frequency axis is correctly annotated.
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Performance analysis and Simulation of small signa
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Application background Small signal amplifier is an important part of the electronic circuit, because it works in the linear region of the transistor, so it is called linear amplifier, using MATLAB to simulate the various parameters of the small signal amplifier, such as voltage gain, input impedance, output impedance, frequency response, etc. Key Technology 1, learning the principle of the common emitter amplifier circuit, using the default parameters or set up their own parameters to debug amplif1.m program, get the output parameters2, learning the principle of direct coupled amplifier, using the default parameters or their own set of parameters to debug the amplif2.m program, get the output parameters.3, learning the principle of differential amplifier circuit, using the default parameters or their own set of parameters to debug the amplif3.m program, get the output parameters.4. The principle of the coupled audio amplifier is learned by using
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Discrete time filter design
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Application background (1) Butterworth filter: a filter with a band and stop band attenuation. , , , ,, [N, Wc]=buttord, (Ws, Ap, As, Wp) used to determine the order of the Butterworth filter. ; ; [b;; butter; a]=;;;; N; Wc; options(2) Chebyshev type I filter: passband ripple in the passband ripple controller, presents the characteristics, monotone attenuation in the stopband(3) Chebyshev type II filter: stopband ripple in the stopband ripple controller, presents the characteristics, the pass band monotone attenuation Key Technology 1, impulse response is not political reformThe impulse response invariant method is to transform the s plane of the analog filter into the z plane of the digital filter, and then map the analog filter into a digital filter. IIR digital filter design is an important part of simulation design of low pass filter, typical of a Butterwort
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Sampling process
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Application background The two principle of the sampling process is aliasing and reconstruction, which involves the mixing of sine wave and linear frequency modulation signal. Then the DTFT is used in the frequency domain.1 because the analog signal can not be generated in the MATLAB, it is necessary to do the simulation of real-time t axis. Therefore, it is important to distinguish between the T and the sampling period of the study.2 for the continuous time signal sampling, because the frequency domain is extended to the frequency domain, it is shown that the aliasing effect is shown in the frequency domain. In MATLAB, the effect can only be simulated. Simulation includes sampling operations, D/A conversion.3 to demonstrate the aliasing effect, a simple analog input signal is required to pass the system. Interval sampling with A/D converter. Using X (T) sample obtained from the sample subset to achieve simulation. D/A is composed of two parts: the sampling time int
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Spectral analysis MATLAB experiment
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Application background signal is infinitely long, and in the process of signal processing can only use a limited long signal, so the signal is needed to "cut off". In signal processing, the "cut off" is viewed as a signal of a finite length, or from the point of view of the analysis is the infinite length x (T) multiplied by the finite length w (T).& nbsp; & nbsp; if x (T) is a bandwidth limited signals, and w (T) is unlimited bandwidth function, truncated signal also must be unlimited bandwidth signal, resulting in the so-called spectral leakage. Key Technology Using MATLAB programming to draw the shape of various window functions 2, using MATLAB programming to draw a variety of window function of the amplitude response 3, the amplitude frequency response of the rectangular window, the window length are: N=10, N=20, N=50, N=100& nbsp; 4, known periodic signal x (T) =0.75+3.4cos2 PI ft+2.7cos4 PI ft+1.5sin3.5 PI ft+2.5si
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