Signal routing in MATLAB - Mini Project: Build & Apply

Signal routing

📖 Scenario: You are working on a simple signal processing system where different input signals are routed to output channels based on their type.This is like sorting mail into different bins depending on the address.

🎯 Goal: Create a MATLAB script that stores input signals in a structure, sets a routing threshold, routes signals to outputs based on the threshold, and then displays the routed signals.

📋 What You'll Learn

Create a structure called signals with fields audio, video, and data containing numeric arrays.

Create a variable called threshold with a numeric value.

Use a for loop with variable field to iterate over the fields of signals.

Route signals to a new structure routed only if their mean value is greater than threshold.

Print the routed structure to display the routed signals.

💡 Why This Matters

🌍 Real World

Signal routing is used in audio/video systems, communication devices, and data processing to send signals to the correct output channels.

💼 Career

Understanding signal routing helps in roles like embedded systems engineer, audio engineer, and communication system developer.

1

Create the signals structure

Create a structure called signals with these exact fields and values: audio = [1, 3, 5], video = [2, 4, 6], and data = [0, 1, 0].

MATLAB

% Your code here

Hint

Use dot notation to create fields in the signals structure.

2

Set the routing threshold

Create a variable called threshold and set it to 2.

MATLAB

signals.audio = [1, 3, 5];
signals.video = [2, 4, 6];
signals.data = [0, 1, 0];
% Your code here

Hint

Just assign the number 2 to the variable threshold.

3

Route signals based on threshold

Use a for loop with variable field to iterate over fieldnames(signals). Inside the loop, check if the mean of signals.(field) is greater than threshold. If yes, assign signals.(field) to routed.(field).

MATLAB

signals.audio = [1, 3, 5];
signals.video = [2, 4, 6];
signals.data = [0, 1, 0];
threshold = 2;
% Your code here

Hint

Use fieldnames to get the fields, then loop with for. Use mean to check the average value.

4

Display the routed signals

Write a disp statement to display the routed structure.

MATLAB

signals.audio = [1, 3, 5];
signals.video = [2, 4, 6];
signals.data = [0, 1, 0];
threshold = 2;
fields = fieldnames(signals);
routed = struct();
for i = 1:length(fields)
    field = fields{i};
    if mean(signals.(field)) > threshold
        routed.(field) = signals.(field);
    end
end
% Your code here

Hint

Use disp(routed) to show the routed signals.

Practice

1. What is the main purpose of signal routing in MATLAB programming?

easy

A. To send data to different parts of a program based on conditions

B. To create graphical user interfaces

C. To perform mathematical calculations only

D. To store data permanently on disk

Solution

1. Step 1: Understand signal routing concept

   Signal routing means directing data flow to different parts depending on conditions.

2. Step 2: Match purpose with options

   Only To send data to different parts of a program based on conditions describes sending data based on conditions, which is signal routing.

3. Final Answer:

   To send data to different parts of a program based on conditions -> Option A

4. Quick Check:

   Signal routing = conditional data flow [OK]

Hint: Signal routing controls data flow based on conditions [OK]

Common Mistakes:

• Confusing signal routing with data storage
• Thinking it only does calculations
• Mixing it up with GUI creation

2. Which of the following is the correct syntax to route a signal based on a condition in MATLAB?

easy

A. if signal > 0 {
output = signal;
} else {
output = 0;
}

B. if (signal > 0) then
output = signal
else
output = 0
end if

C. if signal > 0
output = signal;
else
output = 0;
end

D. if signal > 0:
output = signal
else:
output = 0

Solution

1. Step 1: Recall MATLAB if-else syntax

   MATLAB uses 'if condition', statements, 'else', statements, and 'end' to close.

2. Step 2: Compare options with MATLAB syntax

   if signal > 0 output = signal; else output = 0; end matches MATLAB syntax exactly; others use syntax from other languages.

3. Final Answer:

   if signal > 0 output = signal; else output = 0; end -> Option C

4. Quick Check:

   MATLAB if-else ends with 'end' [OK]

Hint: MATLAB if-else blocks end with 'end' keyword [OK]

Common Mistakes:

• Using 'then' keyword (not in MATLAB)
• Using braces {} instead of end
• Using colons like Python

3. What will be the output of this MATLAB code?

signal = -5;
if signal > 0
    routed = 1;
else
    routed = -1;
end
routed

medium

A. -1

B. 1

C. 0

D. Error

Solution

1. Step 1: Check the condition signal > 0

   signal is -5, which is not greater than 0, so condition is false.

2. Step 2: Follow else branch

   Since condition is false, routed is assigned -1.

3. Final Answer:

   -1 -> Option A

4. Quick Check:

   signal = -5 -> routed = -1 [OK]

Hint: Check condition truth to pick if or else branch [OK]

Common Mistakes:

• Assuming negative numbers satisfy > 0
• Confusing output variable name
• Expecting zero output

4. Identify the error in this MATLAB signal routing code:

signal = 10;
if signal > 5
    output = 1;
else
    output = 0;

medium

A. Variable 'output' is not defined

B. Missing 'end' to close the if statement

C. Incorrect comparison operator

D. Using semicolons incorrectly

Solution

1. Step 1: Check if statement structure

   MATLAB requires 'end' to close if blocks.

2. Step 2: Verify code completeness

   The code lacks 'end' after else block, causing syntax error.

3. Final Answer:

   Missing 'end' to close the if statement -> Option B

4. Quick Check:

   if blocks must end with 'end' [OK]

Hint: Always close if with 'end' in MATLAB [OK]

Common Mistakes:

• Forgetting 'end' after if-else
• Thinking semicolons end blocks
• Misusing comparison operators

5. You want to route a signal in MATLAB to three different outputs based on its value:
- If signal < 0, output = -1
- If signal == 0, output = 0
- If signal > 0, output = 1
Which code correctly implements this routing?

hard

A. if signal < 0
output = -1;
else if signal == 0
output = 0;
else
output = 1;
end

B. if signal <= 0
output = -1;
elseif signal == 0
output = 0;
else
output = 1;
end

C. if signal < 0
output = -1;
if signal == 0
output = 0;
else
output = 1;
end

D. if signal < 0
output = -1;
elseif signal == 0
output = 0;
else
output = 1;
end

Solution

1. Step 1: Understand routing conditions

   We need three cases: less than 0, equal to 0, greater than 0.

2. Step 2: Check code correctness

   if signal < 0 output = -1; elseif signal == 0 output = 0; else output = 1; end uses if, elseif, else correctly with proper conditions and 'end'.

3. Step 3: Identify errors in other options

   if signal <= 0 output = -1; elseif signal == 0 output = 0; else output = 1; end wrongly uses <= which overlaps conditions; C uses two separate ifs causing logic errors; D uses 'else if' which is invalid syntax in MATLAB.

4. Final Answer:

   if signal < 0 output = -1; elseif signal == 0 output = 0; else output = 1; end -> Option D

5. Quick Check:

   Use if-elseif-else for multiple conditions [OK]

Hint: Use if-elseif-else for multiple exclusive conditions [OK]

Common Mistakes:

• Using overlapping conditions like <= and ==
• Using nested if without else properly
• Writing 'else if' instead of 'elseif'