Understand electromagnetic waves, frequency and wavelength.
Learn the role of impedance and matching in RF systems.
Grasp the meaning of VSWR and decibel (dB) in real applications.
| Time | Module | Description |
|---|---|---|
| 0–10 min | Review | Short quiz to recall prior concepts. |
| 10–30 min | Theory | Explain EM waves, wavelength formula, and impedance definition. |
| 30–50 min | Demonstration | Use cable analogy to illustrate signal flow and reflection. |
| 50–55 min | Verification | Summarize key logic in your own words. |
| 55–60 min | Memory Plan | Write 3 key cards and schedule spaced reviews. |
Electromagnetic Wave
An electromagnetic wave is the propagation of alternating electric and magnetic fields.
RF signals are essentially high-frequency electromagnetic waves.
Frequency & Wavelength
Frequency (f): oscillations per second, in hertz (Hz).
Wavelength (λ): distance of one cycle, λ = c / f.
Higher frequency means shorter wavelength.
Impedance
Impedance represents how much a medium resists signal flow.
50 Ω is the standard in RF systems for optimal power and signal integrity.
Matching & Reflection
When impedances differ, part of the signal reflects back.
Proper matching minimizes reflection and maximizes power transfer.
VSWR (Voltage Standing Wave Ratio)
Indicates how well the system is matched.
Ideal VSWR = 1. Practical engineering target: ≤ 1.5.
dB (Decibel)
Expresses power or voltage ratios in logarithmic form.
-3 dB ≈ half power, +3 dB ≈ double power.
Purpose: Visualize impedance matching.
Take a data cable as signal path.
Imagine signal as water flow.
Squeeze one end → mismatch → reflection.
Uniform thickness → matched system → no reflection.
| Time | Task |
|---|---|
| +4 hours | Recall key formulas and terms. |
| Next day | Oral summary before Lesson 2. |
| Day 3 | Quick quiz. |
| Day 7 | Weekly review and error log. |
What is an electromagnetic wave?
How are wavelength and frequency related?
Why is 50 Ω used in RF systems?
What does VSWR = 1 mean?
How many dB is a 50% power drop?
| No. | Front | Back |
|---|---|---|
| 1 | What is wavelength? | λ = c / f; one full wave cycle length. |
| 2 | Why is impedance matching important? | Prevents signal reflection and ensures smooth transmission. |
| 3 | What does -3 dB mean? | Power reduced to half. |