🎯 Pulse Radar Virtual Laboratory

Interactive PPI Display Simulation for ECE 514E, Department of  Electrical & Communication Engineering

Fundamentals of Pulse Radar Systems

1. Basic Principle

A pulse radar system transmits short bursts (pulses) of electromagnetic energy and listens for echoes reflected from targets. By measuring the time delay between transmission and reception, the range to the target is determined.

R = (c × Δt) / 2
Where R = Range, c = Speed of light (3×10⁸ m/s), Δt = Round-trip time delay

2. Plan Position Indicator (PPI)

The PPI is a type of radar display that represents the radar antenna's 360° scan in a circular format:

  • Center: Represents the radar location (ownship)
  • Range Rings: Concentric circles indicating distance from center
  • Bearing: Angle around the circle (0-360°)
  • Blips: Targets appearing as bright spots on the display
  • Sweep: Rotating line representing the antenna beam position

3. Key Radar Parameters

Pulse Repetition Frequency (PRF)

The rate at which pulses are transmitted, measured in Hz.

PRF = 1 / PRI (Pulse Repetition Interval)
Maximum Unambiguous Range: Rmax = c / (2 × PRF)
If a target is beyond this range, it appears at an incorrect (ambiguous) range.

Pulse Width (τ)

Duration of the transmitted pulse in microseconds.

Range Resolution: ΔR = c × τ / 2

Shorter pulses provide better range resolution but require higher peak power.

Radar Cross Section (σ)

A measure of a target's ability to reflect radar energy back to the receiver, measured in m². Depends on:

  • Target size and shape
  • Material properties
  • Aspect angle
  • Operating frequency

4. Radar Range Equation

The fundamental equation describing received signal power:

Pr = (Pt G² λ² σ) / ((4π)³ R⁴)

Where Pt = transmitted power, G = antenna gain, λ = wavelength, σ = RCS, R = range

Educational Note: In this simulation, we assume a monostatic radar (same antenna for transmit and receive) with a directional antenna pattern rotating at constant speed.

PPI Display Simulation

Observe the rotating radar sweep and target detection. Adjust parameters to see their effects on detection and display.

Sweep/Beam
Target Blip
Range Rings

Control Panel

500 Hz
Rmax: 300 km
2.0 μs
Resolution: 300 m
50%
3 RPM

Active Targets

System Status:
Beam Angle: 0°
Detected: 0 targets
Range Scale: 0-80 km

Experimental Procedure

Familiarization (10 minutes)
Launch the PPI simulation and observe the rotating sweep. Note the range rings and the coordinate system. The radar is located at the center of the display. Identify the heading indicator (usually at the top representing North or forward direction).
Target Detection Analysis (20 minutes)
Add 3-5 targets at different ranges and bearings using the "Add Random Target" button. For each target, record:
  • Slant range (distance from center)
  • Bearing angle (degrees from North)
  • Relative signal strength (brightness of blip)
Verify that the range agrees with the formula: R = cΔt/2.
PRF Variation Study (20 minutes)
Objective: Understand Maximum Unambiguous Range

Adjust the PRF slider and observe the Rmax calculation. Set PRF to 1000 Hz (Rmax = 150 km). Place a target at approximately 140 km. Gradually increase the PRF to 2000 Hz and observe if the target "folds over" (range aliasing). Document at what PRF the target range becomes ambiguous.
Range Resolution Experiment (20 minutes)
Objective: Understand pulse width effects

Set pulse width to 10 μs (resolution = 1500 m). Place two targets at the same bearing but separated by 1 km in range. Verify they appear as a single merged target. Gradually decrease pulse width to 0.5 μs and observe when they resolve as separate targets. Record the minimum separation distance.
Radar Cross Section Investigation (15 minutes)
Add targets with varying RCS values (the simulation randomizes these). Adjust the Gain control and observe which targets disappear first as you lower the gain. This demonstrates the radar detection threshold and the importance of target RCS in detection probability.
Multiple Target Tracking (15 minutes)
Create a scenario with 10 targets distributed throughout the coverage area. Practice estimating ranges and bearings manually from the PPI display. Compare your manual readings with the actual displayed coordinates in the target list.
Safety Note: This is a software simulation. In actual radar laboratories, always follow RF safety protocols and never look directly into waveguide openings when transmitters are active.

Laboratory Report Guidelines

Title Page Requirements

  • Course name and number (e.g., EE 340 - Microwave Engineering)
  • Experiment title: "Pulse Radar Characteristics and PPI Display Analysis"
  • Student name and ID
  • Date of experiment and submission date
  • Instructor name

Abstract (Approx. 150-200 words)

Summarize the objectives, methodology, and key findings. Include specific mention of PRF effects on ambiguous range, pulse width impact on resolution, and observations of target detection thresholds.

Introduction (1 page)

  • Principles of pulse radar operation
  • Importance of PPI displays in air traffic control, maritime navigation, and weather monitoring
  • Objectives of this laboratory exercise

Theoretical Background (2-3 pages)

  • Derivation of the radar range equation
  • Explanation of PRF and unambiguous range with mathematical treatment
  • Range resolution and pulse compression concepts
  • PPI display coordinate systems (polar vs. cartesian conversion)

Experimental Procedure

Describe the simulation environment and parameters varied. Do not copy the lab manual verbatim; describe what you actually did and observed.

Results and Analysis (Major Section)

Required Elements:

  • Table 1: Target coordinates (Actual vs. Measured from PPI)
  • Graph: PRF vs. Maximum Unambiguous Range (theoretical and observed)
  • Photographic captures or sketches of PPI display showing resolution limits
  • Analysis of minimum detectable signal vs. range relationship
  • Error analysis comparing calculated vs. displayed ranges
Critical Analysis Question: Why does the radar range equation have an R⁴ term in the denominator? Discuss the implications for long-range target detection.

Discussion Questions (Must Address All)

  1. Explain why decreasing PRF increases unambiguous range but reduces data update rate. What operational scenarios require high PRF vs. low PRF?
  2. How would you resolve range ambiguity in a practical radar system?
  3. Discuss the trade-off between pulse width (energy) and range resolution. How do modern radars overcome this limitation?
  4. If a target appears at 180° bearing on the PPI and moves to 90°, has the target moved clockwise or counter-clockwise relative to the radar?
  5. Why do aircraft with stealth technology have low RCS? How does shape affect radar return?

Conclusion

Summarize key learning outcomes. Discuss the limitations of the simulation compared to real-world radar systems (atmospheric effects, multipath, clutter, etc.).

References

Cite the course textbook (e.g., Skolnik, Introduction to Radar Systems), IEEE papers on radar signal processing, and any additional resources consulted.

Grading Rubric:
• Technical Content (40%) – Accuracy of calculations and depth of analysis
• Presentation (20%) – Organization, grammar, figure quality
• Critical Thinking (30%) – Quality of discussion and insights
• Formatting (10%) – Adherence to guidelines and templates

Reports must be typed (LaTeX or Word) with all figures properly numbered and captioned. Hand-drawn sketches are acceptable only if neatly executed and scanned.