diff --git a/radio/Interpolation.hpp b/radio/Interpolation.hpp
index e9d830e..a234d87 100644
--- a/radio/Interpolation.hpp
+++ b/radio/Interpolation.hpp
@@ -17,6 +17,13 @@ namespace Radio
 namespace Interpolation
 {
 
+// --------------------------------------------------------------
+// Complex FIR-based polyphase interpolation filter (Farrow structure)
+// From:
+// "PERFORMANCE AND DESIGN OF FARROW FILTER USED FOR ARBITRARY RESAMPLING"
+// [unknown date], Fred Harris, Signal Processing ChairCommunication Systems and Signal Processing Institute
+// College of Engineering, San Diego State University, San Diego, CA 92182-0190 USA
+// --------------------------------------------------------------
 class Farrow : public FirComplex
 {
 	typedef struct _ml_farrow_coef_hdr_t
@@ -63,7 +70,7 @@ public:
 		m_fifo[m_w] = x;
 	}
 	
-	ComplexScalar process(radio_float_t mu, uint32_t pop)
+	ComplexScalar process(RealScalar mu, uint32_t pop)
 	{
 		uint32_t i, r;
 		int32_t j;
@@ -131,8 +138,9 @@ public:
 			}
 		}
 		printf("Farrow filter coefficients loaded (M=%d, N=%d)", m_M, m_N);
-	
+		
 		delete [] pCoeff;
+		fclose(pFile);
 
 	}
 	
@@ -146,7 +154,7 @@ private:
 	CVec m_h;
 	CVec m_fifo;
 	
-	ComplexScalar horner(radio_float_t mu)
+	ComplexScalar horner(RealScalar mu)
 	{
 		uint32_t i;
 
@@ -161,6 +169,179 @@ private:
 	
 };
 
+// --------------------------------------------------------------
+// Complex FIR-based discrete step polyphase interpolation filter
+// --------------------------------------------------------------
+class PolyPhase : public FirComplex
+{
+public:
+	PolyPhase()
+	{
+		
+	}
+	
+	~PolyPhase()
+	{
+		
+	}
+	
+	void init(RealScalar fa, RealScalar tsym, RealScalar alpha, uint32_t N, uint32_t M)
+	{
+		uint32_t i, j;
+		fir_float_t *pCoeff;
+		RealScalar k;
+	
+		FirComplex::setNumTaps(N);
+		m_M = M;
+		m_N = N;
+		m_coeff.resize(N, M);
+		m_fifo.resize(N);
+		m_fifo.setZero();
+		
+		pCoeff = (fir_float_t*)malloc((N+1)*M*sizeof(fir_float_t));
+		memset(pCoeff, 0, (N+1)*M*sizeof(fir_float_t));
+
+		k = CalcFirSRRC(pCoeff, M*fa, tsym, alpha, N*M);
+
+		m_coeff.resize(N, M);
+		for(i=0; i < M; i++)
+		{
+			for(j=0; j < N; j++)
+			{
+				m_coeff(j,i) = M*pCoeff[M*j+M/2+i];
+			}
+		}
+		free(pCoeff);
+	}
+
+	void feed(ComplexScalar const &x, uint32_t push)
+	{
+		m_w = (m_w + push) % m_N;
+		m_fifo[m_w] = x;
+	}
+	
+	ComplexScalar process(RealScalar mu, uint32_t pop)
+	{
+		uint32_t i, r, index;
+		int32_t j;
+
+		index = (uint32_t)dmod(dmax(0, mu*m_M), (RealScalar)m_M);
+		
+		m_r = (m_r + pop) % m_N;
+
+		if (pop)
+		{
+			r = m_r;
+			j = m_N-1;
+			while(r < m_N)
+			{
+				m_x[j--] = m_fifo[r++];
+			}
+			r = 0;
+			while(j >= 0)
+			{
+				m_x[j--] = m_fifo[r++];
+			}
+		}
+
+		return FirComplex::processReal(m_coeff.col(index));
+	}	
+	
+private:
+	uint32_t m_M;
+	uint32_t m_N;
+	uint32_t m_r;
+	uint32_t m_w;
+	RMat m_coeff;
+	CVec m_fifo;
+};
+
+class DownSampler : public FirComplex
+{
+public:
+	DownSampler()
+	: m_pFir(nullptr)
+	, m_pCoeff(nullptr)
+	, m_M(0)
+	, m_currStage(0)
+	{
+		
+	}
+	~DownSampler()
+	{
+		if (m_pFir)
+			delete [] m_pFir;
+			
+		if (m_pCoeff)
+			delete [] m_pCoeff;
+		
+	}
+	void init(uint32_t M, RealScalar const *coeff, uint32_t N)
+	{
+		uint32_t i, j;
+		uint32_t stage_N;
+		uint32_t stage;
+		
+		if (m_pFir)
+			delete [] m_pFir;
+			
+		if (m_pCoeff)
+			delete [] m_pCoeff;
+
+		m_pFir = new FirComplex[M];
+		m_pCoeff = new RVec[M];
+		
+		for (stage=0; stage < M; stage++)
+		{
+			stage_N = 0;
+			for (i=stage; i < N; i += M)
+			{
+				stage_N++;
+			}
+			m_pFir[stage].setNumTaps(stage_N);
+			m_pCoeff[stage].resize(stage_N);
+			
+			j=0;
+			for (i=stage; i < N; i += M)
+			{
+				m_pCoeff[stage](j++) = coeff[i];
+			}
+		}
+		m_M = M;
+		m_currStage = m_M-1;
+
+	}
+	
+	uint32_t process(CVec &dst, CVec const &src, uint32_t len)
+	{
+		uint32_t i;
+		uint32_t j;
+		ComplexScalar res(0,0);
+		
+		j = 0;
+		for (i=0; i < len; i++)
+		{
+			m_pFir[m_currStage].feed(src(i));
+			res += m_pFir[m_currStage].processReal(m_pCoeff[m_currStage]);
+			m_currStage--;
+			if (m_currStage >= m_M)
+			{
+				dst(j++) = res;
+				res = ComplexScalar(0,0);
+				m_currStage = m_M-1;
+			}
+			
+		}
+		return j;
+	}
+	
+private:
+	FirComplex *m_pFir;
+	RVec *m_pCoeff;
+	uint32_t m_M;
+	uint32_t m_currStage;
+	
+};
 } // Radio::Interpolation
 } // ::Radio