diff --git a/lib/radio/ddc/sim/tb_results.m b/lib/radio/ddc/sim/tb_results.m
index 2e91480..501b47f 100644
--- a/lib/radio/ddc/sim/tb_results.m
+++ b/lib/radio/ddc/sim/tb_results.m
@@ -2,7 +2,7 @@
 function tb_results()
 fa = 100.0;
 R = TEXTREAD('ratio.txt');
-N = 3;
+N = TEXTREAD('nstages.txt');;
 M = 1;
 fa_dec = fa/R
 N_pfir = 63;
@@ -12,18 +12,27 @@ Q_out_dec = TEXTREAD('q_dec.txt')';
 I_out_fir = TEXTREAD('i_fir.txt')';
 Q_out_fir = TEXTREAD('q_fir.txt')';
 
+I_out_fir = I_out_fir(1:2:length(I_out_fir));
+Q_out_fir = Q_out_fir(1:2:length(Q_out_fir));
+
 N_dec = length(I_out_dec)-2*N_pfir;
 N_fft_dec = N_dec
 N_fft2_dec = N_fft_dec/2;
 
-fft_y2_fir = 2/N_fft_dec*abs(fft(I_out_fir(2*N_pfir+1:N_fft_dec+2*N_pfir).*hann(N_fft_dec)'));
+N_fir = length(I_out_fir)-2*N_pfir;
+N_fft_fir = N_fir
+N_fft2_fir = N_fft_fir/2;
+
+fft_y2_fir = 2/N_fft_fir*abs(fft(I_out_fir(2*N_pfir+1:N_fft_fir+2*N_pfir).*hann(N_fft_fir)'));
 
-pfir_b = sinc(0.2*(-(N_pfir-1)/2:1:(N_pfir)/2));
-pfir_b = pfir_b/sum(pfir_b).*blackman(N_pfir)';
-I_out_dec = I_out_dec;
-Q_out_dec = Q_out_dec;
 fft_y2_dec = 2/N_fft_dec*abs(fft(I_out_dec(2*N_pfir+1:N_fft_dec+2*N_pfir).*hann(N_fft_dec)'));
 
+f = (1:N_fft_dec)/N_fft_dec;
+g = (R*M)^N;
+H = abs(sin(pi*M.*f)./sin(pi.*f/R)).^N;
+
+H = max(fft_y2_fir(1:2))*H ./ g;
+
 wavwrite(0.45*[I_out_fir'-mean(I_out_fir) Q_out_fir'-mean(Q_out_fir)], 8000, 16, 'iq_cfir.wav');
 wavwrite(0.45*[I_out_dec'-mean(I_out_dec) Q_out_dec'-mean(Q_out_dec)], 8000, 16, 'iq.wav');
 
@@ -36,8 +45,14 @@ figure;
 cic_plot(M, N, R);
 
 figure;
-plot(fa/(R*N_fft_dec)*(0:N_fft2_dec),20*log10(fft_y2_fir(1:N_fft2_dec+1)), '-', fa/(R*N_fft_dec)*(0:N_fft2_dec),20*log10(fft_y2_dec(1:N_fft2_dec+1)), '-');
-legend('CFIR', 'no CFIR');
+subplot(2,1,1)
+plot(fa/(R*N_fft_dec)*(0:N_fft2_dec),20*log10(fft_y2_dec(1:N_fft2_dec+1)), '-', fa/(R*N_fft_dec)*(0:N_fft2_dec),20*log10(H(1:N_fft2_dec+1)), 'r-');
+legend('CIC', 'Droop');
+xlabel('MHz');
+grid;
+subplot(2,1,2)
+plot(fa/(2*R*N_fft_fir)*(0:N_fft2_fir),20*log10(fft_y2_fir(1:N_fft2_fir+1)), '-');
+legend('CFIR');
 xlabel('MHz');
 grid;
 
diff --git a/lib/radio/ddc/src/tb_ddc.vhd b/lib/radio/ddc/src/tb_ddc.vhd
index e9a365a..7afe05a 100644
--- a/lib/radio/ddc/src/tb_ddc.vhd
+++ b/lib/radio/ddc/src/tb_ddc.vhd
@@ -306,8 +306,6 @@ BEGIN
 	rfgen_q_out_f	<= to_real(rfgen_dout_q);
 	
 	tb : PROCESS
-	file RESULT_FREQ:   text open write_mode is "ratio.txt"; 
-	variable L:         line;
 
 	BEGIN
 
@@ -315,8 +313,6 @@ BEGIN
 		wait for 4*PERIOD;
 		rst <= '0';
 
-		fprint(RESULT_FREQ, L,"%s\n", natural'image(cic_ratio));
-
 		wait for 2*PERIOD;
 		-------------------------------------------
 		-- Program gains
@@ -353,6 +349,21 @@ BEGIN
 		wait; 
 	END PROCESS;
 
+	tb_param : PROCESS
+	file RESULT_R:        text open write_mode is "ratio.txt"; 
+	file RESULT_N:        text open write_mode is "nstages.txt"; 
+	variable L:         line;
+
+	BEGIN
+
+		-- Wait 100 ns for global reset to finish
+		wait until rising_edge(clk) and rst = '0';
+		fprint(RESULT_R, L,"%s\n", natural'image(cic_ratio));
+		fprint(RESULT_N, L,"%s\n", natural'image(cic_nstages));
+		wait; 
+
+	END PROCESS;
+
 	tb_fo : PROCESS(clk)
 	file RESULT_Ii:	      text open write_mode is "i_in.txt"; 
 	file RESULT_Qi:	      text open write_mode is "q_in.txt"; 
@@ -363,21 +374,22 @@ BEGIN
 	variable L:         line;
 
 	BEGIN
-		if rising_edge(clk) and fileout_enable = '1' then
-			if ddc_din_vld = '1' then
-				fprint(RESULT_Ii, L,"%s\n", REAL'image(to_real(rfgen_dout_i)));
-				fprint(RESULT_Qi, L,"%s\n", REAL'image(to_real(rfgen_dout_q)));
-			end if;
-			if ddc_dout_vld = '1' then
-				fprint(RESULT_Ifir, L,"%s\n", REAL'image(to_real(ddc_dout_i)));
-				fprint(RESULT_Qfir, L,"%s\n", REAL'image(to_real(ddc_dout_q)));
-			end if;
-			if ddc_dec_vld = '1' then
-				fprint(RESULT_Idec, L,"%s\n", REAL'image(to_real(ddc_dec_i)));
-				fprint(RESULT_Qdec, L,"%s\n", REAL'image(to_real(ddc_dec_q)));
+		if rising_edge(clk) then
+			if fileout_enable = '1' then
+				if ddc_din_vld = '1' then
+					fprint(RESULT_Ii, L,"%s\n", REAL'image(to_real(rfgen_dout_i)));
+					fprint(RESULT_Qi, L,"%s\n", REAL'image(to_real(rfgen_dout_q)));
+				end if;
+				if ddc_dout_vld = '1' then
+					fprint(RESULT_Ifir, L,"%s\n", REAL'image(to_real(ddc_dout_i)));
+					fprint(RESULT_Qfir, L,"%s\n", REAL'image(to_real(ddc_dout_q)));
+				end if;
+				if ddc_dec_vld = '1' then
+					fprint(RESULT_Idec, L,"%s\n", REAL'image(to_real(ddc_dec_i)));
+					fprint(RESULT_Qdec, L,"%s\n", REAL'image(to_real(ddc_dec_q)));
+				end if;
 			end if;
 		end if;
-
 	END PROCESS;
 
 END;