Revision 7:46327dcab1bf, committed 2014-12-08

Comitter:

MikamiUitOpen

Date:

Mon Dec 08 05:46:37 2014 +0000

Parent:

6:e4b8e25573f3

Commit message:

7

Changed in this revision

diff -r e4b8e25573f3 -r 46327dcab1bf WindowingDesignLpfHpf/WindowingDesignLH.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/WindowingDesignLpfHpf/WindowingDesignLH.cpp	Mon Dec 08 05:46:37 2014 +0000
@@ -0,0 +1,75 @@
+//------------------------------------------------------------------------------
+//  Design of FIR filter of LPF and HPF using window method
+//
+//  2014/12/08, Copyright (c) 2014 MIKAMI, Naoki
+//------------------------------------------------------------------------------
+
+#include "WindowingDesignLH.hpp"
+
+namespace Mikami
+{
+    WindowingDesign::WindowingDesign(int order, float fs)
+            : FS_(fs), PI_FS_(3.1415926536f/fs)
+    {
+        order_ = order;
+        if ((order % 2) != 0)
+        {
+            fprintf(stderr, "order must be even.");
+            return;
+        }
+        hm_ = new float[order/2+1];
+        wn_ = new float[order/2+1];    
+        
+        HammWindow();
+    }
+        
+    void WindowingDesign::Design(int order, Type pb, float fc,
+                                 float hk[])
+    {       
+        if (pb == LPF) fC_ = fc;
+        if (pb == HPF) fC_ = 0.5f*FS_ - fc;
+    
+        if (order != order_)
+        {
+            order_ = order_;
+            if (hm_ != NULL) delete[] hm_;
+            hm_ = new float[order/2+1];
+            if (wn_ != NULL) delete[] wn_;
+            wn_ = new float[order/2+1];
+            HammWindow();
+        }
+
+        // Calculate coefficients for LPF
+        LpfCoefficients();
+        // If HPF, transform coefficients
+        if (pb != LPF) ToHpf();
+        
+        for (int k=0; k<=order/2; k++)
+            hk[k] = hm_[order/2-k];
+    }
+
+    // Calculation of coefficients for LPF
+    void WindowingDesign::LpfCoefficients()
+    {
+        float w = 2.0f*PI_FS_*fC_;
+        hm_[0] = 2.0f*fC_/FS_;
+        for (int k=1; k<=order_/2; k++)
+            hm_[k] = (sinf(k*w)/(PI_*k))*wn_[k];  
+    }
+    
+    // Transform LPF to HPF
+    void WindowingDesign::ToHpf()
+    {
+        for (int k=1; k<=order_/2; k+=2)
+            hm_[k] = -hm_[k];
+    }    
+
+    // Hamming window
+    void WindowingDesign::HammWindow()
+    {
+        float pi2OvM = 2.0f*PI_/(float)(order_ + 1);
+        for (int n=0; n<=order_/2; n++)
+            wn_[n] = 0.54f + 0.46f*cosf(pi2OvM*n);
+    }
+}
+

diff -r e4b8e25573f3 -r 46327dcab1bf WindowingDesignLpfHpf/WindowingDesignLH.hpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/WindowingDesignLpfHpf/WindowingDesignLH.hpp	Mon Dec 08 05:46:37 2014 +0000
@@ -0,0 +1,52 @@
+//------------------------------------------------------------------------------
+//  Design of FIR filter of LPF and HPF using window method -- Header
+//
+//  2014/11/09, Copyright (c) 2014 MIKAMI, Naoki
+//------------------------------------------------------------------------------
+
+#ifndef HAMMING_WINDOWING_DESIGN_HPP
+#define HAMMING_WINDOWING_DESIGN_HPP
+
+#include "mbed.h"
+
+namespace Mikami
+{
+    class WindowingDesign
+    {
+    public:
+        struct Coefs { float a1, a2, b1; };
+        enum Type { LPF, HPF };
+
+        // Constructor
+        WindowingDesign(int order, float fs);
+
+        //Destructor
+        ~WindowingDesign()
+        {
+            delete[] hm_;
+            delete[] wn_;
+        }
+
+        // Execution of design
+        void Design(int order, Type pb, float fc, float hk[]);
+
+    private:
+        static const float PI_ = 3.1415926536f;
+        const float FS_;    // Sampling frequency
+        const float PI_FS_;
+        
+        float *hm_;     // For coefficients
+        float *wn_;     // For Windwo
+                
+        int order_;     // Order
+        float fC_;      // Cutoff frequency
+        
+        // Calculation of coefficients for LPF
+        void LpfCoefficients();
+        // Transform LPF to HPF
+        void ToHpf();
+        // Hamming window
+        void HammWindow();
+    };
+}
+#endif  // HAMMING_WINDOWING_DESIGN_HPP