Beamforming

zdm/beam_generator/DSA110_beamfile.dat

@@ -0,0 +1,9 @@
+1.405e9        #MHz obs frequency
+3.4         # FWHM [deg]
+34.37 0     # pointing angle (zenith, azimuth) of primary beam. Centre is 71.6 deg - 37:14:02 = 34.37
+48          # number of antennas
+-200 0      # ant 1
+200 0       # ant 48
+256         # number of beams
+-3.764     # azimuth angle of beam0 [deg]. 2.125 / sin(34.37)
+3.764      # azimuth angle of final beam [deg] Adding 255 / 60. to above

zdm/beam_generator/FAST.dat

@@ -0,0 +1,29 @@
+2 -1 1 1.04 60.
+# above are: beam method (2: read tabe below)
+# -1: individual half power beam widths
+# 1: beam widths are HPBW
+# 1.04: scale beam widths by this value (1.3 GHz to 1.25 GHz)
+# 60. units of below, here arcminutes
+# data from https://iopscience.iop.org/article/10.1088/1674-4527/20/5/64/pdf
+# bX    bY      HPBW1300    A1250
+-0.04   -0.02   3.01        0.622
+5.76    -0.01   3.04        0.581
+2.86    -4.98   3.03        0.617
+-2.89   -5.01   3.05        0.598
+-5.78   -0.02   3.03        0.639
+-2.92   4.98    3.07        0.604
+2.85    4.97    3.02        0.602
+11.55   -0.02   3.04        0.554
+8.65    -5.01   3.04        0.577
+5.78    -10.02  3.08        0.586
+0.00    -10.04  3.05        0.580
+-5.78   -10.07  3.07        0.576
+-8.67   -5.05   3.04        0.604
+-11.61  -0.02   3.10        0.573
+-8.68   4.99    3.06        0.568
+-5.83   10.02   3.10        0.529
+-0.03   10.00   3.02        0.565
+5.76    10.00   3.05        0.557
+8.63    4.98    3.03        0.569
+
+

zdm/beam_generator/README.txt

@@ -0,0 +1,24 @@
+This folder contains files used to generate simulate telescope beamshapes,
+and convert them into Beamdata. These programs are independent of the zdm code,
+but provide useful into to it.
+
+The relevant programs are:
+
+###### sim_fast_mutibeam.py ########
+This program simulates the FAST multibeam system using data
+contained in "FAST.dat", which is taken from
+https://iopscience.iop.org/article/10.1088/1674-4527/20/5/64/pdf
+With little adaptation, it could also simulate Parkes and Arecibo
+multibeam systems.
+
+###### sim_askap_beams.py ########
+This program is used to simulate the envelope formed by
+ASKAP beams.
+
+
+###### sim_DSA_beams.py ######
+Used to simulate the beamhape from tied beams generated by
+an array of coherently added antennas. It is used to simulate
+e.g. DSA beamshapes - although the exact locations of DSA
+antennas are not known. It could easily be adapted to an arbitrary
+tied array (e.g. MeerKAT)

zdm/beam_generator/compare_fast_parkes.py

@@ -0,0 +1,52 @@
+"""
+Compares FAST and PARKES multibeam profiles
+
+Parkes is scaled to FAST according to simple scaling
+relations.
+
+Note that the Parkes profile is originally taken
+from a full beam simulation.
+"""
+import numpy as np
+from matplotlib import pyplot as plt
+
+def main():
+
+
+
+    FASTb = np.load("FAST_log_bins.npy")
+    FASTh = np.load("FAST_log_hist.npy")
+
+    Parkesb = np.load("../data/BeamData/parkes_mb_log_bins.npy")
+    Parkesh = np.load("../data/BeamData/parkes_mb_log_hist.npy")
+
+    lPb = np.log10(Parkesb)
+    lPb = lPb[:-1]
+    lPb += (lPb[1]-lPb[0])/2.
+    Parkesb = 10**lPb
+
+    lFb = np.log10(FASTb)
+    lFb = lFb[:-1]
+    lFb += (lFb[1]-lFb[0])/2.
+    FASTb = 10**lFb
+
+    total = np.sum(FASTh)
+    print("Total FAST is ",total)
+    # scaling of Parkes hist
+    Parkesh *= 19/13 * (64/300)**2.
+
+    plt.figure()
+
+    plt.plot(Parkesb,Parkesh,label="Scaled Parkes")
+    plt.plot(FASTb,FASTh,label="Gaussian FAST sim")
+    plt.xlabel("B")
+    plt.ylabel("$\\Omega(B)$")
+    plt.xscale('log')
+    plt.yscale('log')
+    plt.legend()
+    plt.tight_layout()
+    plt.savefig("parkes_fast_comparison.png")
+    plt.close()
+
+main()
+

zdm/beam_generator/plot_askap_avals.py

@@ -0,0 +1,44 @@
+"""
+Simple script to plot the "avals": values of
+beam sensitivity for ASKAP as a function of
+distance from boresight.
+
+These "avals" are taken from James et al.
+
+"""
+
+import numpy as np
+from matplotlib import pyplot as plt
+
+
+#### Defines theta offsets from boresights [deg] #####
+thetas = np.linspace(0,4,51)
+
+##### Loads in avals from Hotan et al #####
+data = np.loadtxt("avals.dat")
+x = data[:,0]
+y = data[:,1]
+h_avals = np.interp(thetas,x,y)
+
+##### Calculates avals from James et al. #####
+theta_off = 0.8
+sigma_theta = 3.47
+
+small = np.where(thetas < theta_off)
+
+ftheta = np.exp(-0.5 * ((thetas-theta_off)/sigma_theta)**2.)
+ftheta[small] = 1.
+
+##### plots the values ######
+plt.figure()
+
+plt.plot(thetas,ftheta,label="James et al")
+plt.plot(thetas,h_avals,label="Hotan et al")
+plt.xlim(0,4.)
+plt.ylim(0.63,1.06)
+plt.xlabel("Offset from boresight [deg]")
+plt.ylabel("Relative beam amplitude [B/B(0)]")
+plt.legend()
+plt.tight_layout()
+plt.savefig('avals.pdf')
+plt.close()