java实现FIR滤波器(附完整源码)

下面是一个简单的Java实现FIR滤波器的代码，包括滤波器设计和信号处理两个部分。

首先是滤波器设计部分，其中定义了一个函数firCoefficients，它生成了FIR滤波器的系数。这里采用了一个经典的窗函数法进行滤波器设计，具体细节见代码注释。

public class FIRFilter {
    private double[] coefficients;

    public FIRFilter(double[] coefficients) {
        this.coefficients = coefficients;
    }

    public double[] filter(double[] inputSignal) {
        int M = coefficients.length;
        int N = inputSignal.length;
        double[] outputSignal = new double[N + M - 1];

        // Zero padding the input signal
        double[] inputSignalPadded = new double[N + M - 1];
        for (int n = 0; n < N; n++) {
            inputSignalPadded[n] = inputSignal[n];
        }

        // Convolution
        for (int n = 0; n < N + M - 1; n++) {
            for (int m = 0; m < M; m++) {
                if (n - m >= 0 && n - m < N) {
                    outputSignal[n] += coefficients[m] * inputSignalPadded[n - m];
                }
            }
        }

        return outputSignal;
    }

    public static double[] firCoefficients(int M, double fc, double fs) {
        double[] h = new double[M];

        // Generate the impulse response
        for (int n = 0; n < M; n++) {
            if (n == (M - 1) / 2) {
                h[n] = 2 * fc / fs;
            } else {
                h[n] = Math.sin(2 * Math.PI * fc * (n - (M - 1) / 2) / fs) / (Math.PI * (n - (M - 1) / 2));
            }
            h[n] *= 0.54 - 0.46 * Math.cos(2 * Math.PI * n / (M - 1));
        }

        return h;
    }
}

接下来是信号处理部分，使用上面定义的FIRFilter类进行信号滤波。这里简单地生成了一个正弦信号和一个噪声信号，并对它们进行了滤波，输出了滤波后的信号。

public class Main {
    public static void main(String[] args) {
        // Generate a sine wave signal
        double A = 1;
        double f = 1000;
        double fs = 8000;
        double[] t = new double[8000];
        double[] x = new double[8000];
        for (int n = 0; n < 8000; n++) {
            t[n] = n / fs;
            x[n] = A * Math.sin(2 * Math.PI * f * t[n]);
        }

        // Generate a noise signal
        double[] y = new double[8000];
        Random rand = new Random();
        for (int n = 0; n < 8000; n++) {
            y[n] = rand.nextGaussian();
        }

        // Filter the signals
        double fc = 500;
        int M = 101;
        double[] h = FIRFilter.firCoefficients(M, fc, fs);
        FIRFilter filter = new FIRFilter(h);
        double[] xFiltered = filter.filter(x);
        double[] yFiltered = filter.filter(y);

        // Plot the signals
        Plot2DPanel plot = new Plot2DPanel();
        plot.addLinePlot("x", Color.BLUE, t, x);
        plot.addLinePlot("xFiltered", Color.RED, t, xFiltered);
        plot.addLinePlot("y", Color.GREEN, t, y);
        plot.addLinePlot("yFiltered", Color.ORANGE, t, yFiltered);
        JFrame frame = new JFrame("FIR Filter");
        frame.setContentPane(plot);
        frame.setSize(800, 600);
        frame.setVisible(true);
    }
}

以上代码使用了Java绘图库JMathPlot来实现信号的可视化，如果没有安装该库，请先进行安装。