From f1a9a85c6138715c3933c957c695d0482b901154 Mon Sep 17 00:00:00 2001
From: Warrick Lo <warrick.s.z.lo@gmail.com>
Date: Wed, 11 Feb 2026 07:16:45 -0800
Subject: Finish lab report up to Task 2B

Signed-off-by: Warrick Lo <warrick.s.z.lo@gmail.com>
---
 matlab/phasor.m | 15 +++++++++++++++
 matlab/prep.sh  | 26 ++++++++++++++++++++++++++
 matlab/specan.m | 53 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 94 insertions(+)
 create mode 100644 matlab/phasor.m
 create mode 100644 matlab/prep.sh
 create mode 100644 matlab/specan.m

(limited to 'matlab')

diff --git a/matlab/phasor.m b/matlab/phasor.m
new file mode 100644
index 0000000..add5f84
--- /dev/null
+++ b/matlab/phasor.m
@@ -0,0 +1,15 @@
+function phasor(modulus, argument)
+	% Wrapper for quiver() that plots phasor diagrams.
+	%
+	% Expects the modulus and argument (in degrees)
+	% of a complex number.
+
+	r = modulus;
+	phi = argument * pi / 180;
+
+	% Automatic scaling is disabled.
+	quiver(0, 0, r*cos(phi), r*sin(phi), 0);
+
+	xlim([-r r]);
+	ylim([-r r]);
+end
\ No newline at end of file
diff --git a/matlab/prep.sh b/matlab/prep.sh
new file mode 100644
index 0000000..a2def48
--- /dev/null
+++ b/matlab/prep.sh
@@ -0,0 +1,26 @@
+#!/bin/sh
+
+# Prepare all waveform data for MATLAB processing.
+#
+# This script will:
+# 1.	sanitise the header before running MATLAB's readtable();
+# 2.	convert line endings from DOS to UNIX; and
+# 3.	rename files to have *.tsv file extensions.
+#
+# This script assumes all waveform data is tab-delimited and
+# stored in *.txt files.
+#
+# Usage: ./prep.sh
+
+files=$(ls -- *.txt)
+
+for i in $files; do
+	printf "Converting %s\n" "$i"
+
+	# Replace the header and convert DOS line endings (CRLF)
+	# to UNIX line endings (LF).
+	sed -i -e "1c time\tv1\tv2\tv3\ti1\ti2\ti3" -e "s/\x1D$//" "$i"
+
+	# Rename files to have TSV extensions.
+	mv "$i" "${i%.*}.tsv"
+done
diff --git a/matlab/specan.m b/matlab/specan.m
new file mode 100644
index 0000000..751dba9
--- /dev/null
+++ b/matlab/specan.m
@@ -0,0 +1,53 @@
+function specan(filename)
+	% Spectrum analyser
+	%
+	% Analyse and plot the frequency spectrum of a waveform
+	% given by a tab-separated value (TSV) file.
+	%
+	% The following column headers for the TSV are assumed:
+	% time, v1, v2, v3, i1, i2, i3
+	%
+	% Time measurements are assumed to be in milliseconds.
+	% All voltages and currents are assumed to be given
+	% in Volts and Amperes, respectively.
+
+	data = readtable(filename, FileType="text", Delimiter="\t");
+
+	L = length(data.time);
+	% Assumes data is sampled at regular intervals.
+	T = 1e-3*(data.time(end)-data.time(1))/(L-1);
+	fs = 1/T;
+	% Frequency axis for plotting.
+	f = fs/L*(0:L-1);
+
+	Y1 = abs(fft(data.v1)/L);
+	Y2 = abs(fft(data.v2)/L);
+	Y3 = abs(fft(data.v3)/L);
+	Y4 = abs(fft(data.i1)/L);
+	Y5 = abs(fft(data.i2)/L);
+	Y6 = abs(fft(data.i3)/L);
+
+	figure(1);
+
+	subplot(2, 1, 1);
+	hold on;
+	plot(f, Y1, "r", LineWidth=2);
+	plot(f, Y2, "g", LineWidth=2);
+	plot(f, Y3, "b", LineWidth=2);
+	title("Frequency Spectrum of Voltage Measurements");
+	xlim([0 1e3]);
+	xlabel("Frequency, $f$ (Hz)", Interpreter="latex");
+	ylabel("$\left|\mathcal{F}(V)\right|$ (V)", Interpreter="latex");
+	legend("V_1", "V_2", "V_3");
+
+	subplot(2, 1, 2);
+	hold on;
+	plot(f, Y4, "r", LineWidth=2);
+	plot(f, Y5, "g", LineWidth=2);
+	plot(f, Y6, "b", LineWidth=2);
+	title("Frequency Spectrum of Current Measurements");
+	xlim([0 1e3]);
+	xlabel("Frequency, $f$ (Hz)", Interpreter="latex");
+	ylabel("$\left|\mathcal{F}(I)\right|$ (A)", Interpreter="latex");
+	legend("I_1", "I_2", "I_3");
+end
\ No newline at end of file
-- 
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