Updated plotting to provide equal spacing of frequency steps.

TankGlobals.py

@@ -6,11 +6,11 @@ import numpy as np
 #####
 f0		= 28
 bw0		= 6.5 # assumed tuning range (GHz)
-bw_plt	= 2 # Plotting range (GHz)
+bw_plt	= 3 # Plotting range (GHz)
 fbw		= bw0/f0 # fractional bandwidth
 
 frequency_sweep_steps = 101
-gamma_sweep_steps = 15
+gamma_sweep_steps = 16
 
 gamma = 1 - np.power(f0 / (f0 + bw0/2),2)
 gamma_limit_ratio = 0.99 # how close gamma can get to theoretical extreme

tankPlot.py

@@ -25,6 +25,9 @@ def dB10(pwr_tf):
 	"""Describe power gain of a transfer function in dB (i.e. 10log(x))"""
 	return 10*np.log10(np.abs(pwr_tf))
 	
+def atan(x):
+	return 180/np.pi*np.arctan(x)
+
 
 ################################################################################
 # Override the defaults for this script
@@ -38,7 +41,21 @@ from TankGlobals import *
 ################################################################################
 # Now generate the sweep of resonance tuning (gamma, and capacitance)
 
-gamma_swp = np.linspace(-gamma,gamma,gamma_sweep_steps);
+# Linear based gamma spacing
+#gamma_swp = np.linspace(-gamma,gamma,gamma_sweep_steps)
+
+# Linear PHASE gamma spacing
+# First compute the most extreme phase given the extreme gamma
+g1_limit = np.sqrt( g1*g1 - (gamma*gamma) * c1/l1  )
+K_limit = np.sqrt(c1/l1)*1/g1_limit
+phase_limit = np.mod(np.pi/2 - np.arctan( -1/K_limit * 1/gamma ),np.pi) - np.pi
+
+# This gives us our equal phase spacing points
+phase_swp = np.linspace(-1,1,gamma_sweep_steps) * phase_limit
+# Then use this to compute the gamma steps to produce arbitrary phase given
+# our perfect gain constraint.
+gamma_swp = np.sign(phase_swp)/np.sqrt(np.power(np.tan(np.pi/2 - phase_swp),2)+1) * g1 / np.sqrt(c1/l1)
+
 # compute correction factor for g1 that will produce common gain at f0
 g1_swp = np.sqrt( g1*g1 - (gamma_swp*gamma_swp) * c1/l1  )
 # and compute how much of a negative gm this requres, and it's relative
@@ -54,27 +71,45 @@ print('    Rp = %.3f Ohm' % (1/g1))
 print('    Max G1 boost %.2fmS (%.1f%% of gm1)' % \
 	(1e3*np.max(np.abs(g1_boost)), 100*np.max(g1_ratio)))
 
-h = pp.figure()
-mgr = pp.get_current_fig_manager()
-ax1 = h.add_subplot(2,2,1, projection='smith')
-ax2 = h.add_subplot(2,2,3, projection='polar')
-ax3 = h.add_subplot(2,2,2)
-ax4 = h.add_subplot(2,2,4)
+y_tank = np.zeros((len(gamma_swp),len(f)), dtype=complex)
+tf = np.zeros((len(gamma_swp),len(f)), dtype=complex)
 for itune,gamma_tune in enumerate(gamma_swp):
 	c1_tune = c1_swp[itune]
 	g1_tune = g1_swp[itune]
 	K = np.sqrt(c1/l1)/g1_tune
-	y_tank = g1_tune + jw*c1_tune + 1/(jw * l1)
-	#print(1/np.mean(np.abs(y_tank)))
-	ax1.plot(y_tank, datatype=SmithAxes.Y_PARAMETER, marker="None")
-	tf = gm1 / g1_tune * \
+	y_tank_tmp = g1_tune + jw*c1_tune + 1/(jw * l1)
+	y_tank[itune,:] = y_tank_tmp
+	tf_tmp = gm1 / g1_tune * \
 		1j*(1+delta) / \
 		( 1j*(1+delta) + K*(1 - (1+gamma_tune)*np.power(1+delta,2)) )
+	tf[itune,:] = tf_tmp
+
+tf = tf.T
+tf_d = tf[:,1:]-tf[:,:-1]
+tf_r = tf / (tf[:,int(tf.shape[1]/2)]*np.ones((tf.shape[1],1))).T
+y_tank = y_tank.T
+################################################################################
+
+h1 = pp.figure()
+h2 = pp.figure(figsize=(5,7))
+mgr = pp.get_current_fig_manager()
+################################################################################
+ax1 = h1.add_subplot(2,2,1, projection='smith')
+ax2 = h1.add_subplot(2,2,3, projection='polar')
+ax3 = h1.add_subplot(2,2,2)
+ax4 = h1.add_subplot(2,2,4)
+
+ax1.plot(y_tank, datatype=SmithAxes.Y_PARAMETER, marker="None")
 ax2.plot(np.angle(tf), dB20(tf))
 ax3.plot(f,dB20(tf))
 ax4.plot(f,ang(tf))
 
 ################################################################################
+ax8 = h2.add_subplot(2,1,1)
+ax9 = h2.add_subplot(2,1,2)
+ax8.plot(f,dB20(tf_r))
+ax9.plot(f,ang_unwrap(tf_r.T).T)
+
 ax1.set_title('Tank Impedance')
 ax2.set_title('Transfer Function')
 
@@ -82,11 +117,20 @@ ax3.set_title('TF Gain')
 ax3.set_ylabel('Gain (dB)')
 ax4.set_title('TF Phase')
 ax4.set_ylabel('Phase (deg)')
-for ax_T in [ax3, ax4]:
+ax8.set_title('TF Relative Gain')
+ax8.set_ylabel('Relative Gain (dB)')
+ax9.set_title('TF Relative Phase')
+ax9.set_ylabel('Relative Phase (deg)')
+for ax_T in [ax3, ax4, ax8, ax9]:
 	ax_T.grid()
 	ax_T.set_xlabel('Freq (GHz)')
 	ax_T.set_xlim(( np.min(f), np.max(f) ))
 
-h.tight_layout()
+
+################################################################################
+h1.tight_layout()
+h2.tight_layout()
 mgr.window.geometry(default_window_position)
-h.show()
+h1.show()
+mgr.window.geometry(default_window_position)
+h2.show()