Lab: Visualize EM Waves
One relation, the whole spectrum
What you will do
- Wavelength at 100 MHz
- Raise f 24×, shrink λ 24×
- The energy of a green photon
- Delay across one kilometre
How to read these. Each page states which of its numbers are computed, which come from a published figure, and which are illustrative. Several were generated with AI assistance and say so on the page. They are teaching instruments, not measurements of real hardware.
Labs
Lab: Build and Combine Sine Waves
Two tones, one slow beat
What you will do
- Beat frequency of two close tones
- The carrier the beat rides
- Two equal tones add — or cancel
- How long one beat lasts
Lab: Modulate and Demodulate an AM Signal
One knob sets the whole AM signal
What you will do
- Where the sidebands land
- How little the carrier spends on the message
- Even at its best, AM wastes two thirds
- Push m past 1 — the envelope goes negative
Lab: Compare AM and FM Under Noise
AM and FM meet the same noise
What you will do
- The FM modulation index β
- How much spectrum wideband FM eats
- What all that bandwidth buys
- The trade: narrow the deviation, lose the gain
Lab: Explore Constellation Diagrams
More bits per symbol, more errors
What you will do
- How many bits per symbol?
- The BER of QPSK at 8 dB
- Same energy per bit, more errors
Lab: Calculate Max Data Rates
The ceiling on every link: Shannon capacity
What you will do
- The link SNR, in dB
- The SNR as a ratio
- The spectral efficiency
- The Shannon capacity
- Why +3 dB buys so little
Lab: Visualize Radiation Patterns
Aim a beam with phase, not motion
What you will do
- Steer the beam to 30°
- How wide is the beam?
- When does a grating lobe appear?
Lab: Simulate Signal Propagation
Watch a signal weaken with distance
What you will do
- The free-space path loss
- The received power
- A concrete wall in the way
Lab: Build a Link Budget
Add it up: does the link close?
What you will do
- The received power
- The margin over sensitivity
- Does the cellular link close?
Lab: Visualize Channel Sharing
One channel, split into orthogonal subcarriers
What you will do
- The subcarrier spacing
- The useful symbol time
- The cyclic-prefix guard
Lab: Decode a WiFi Frame
Take an 802.11 frame apart, byte by byte
What you will do
- Decode the Frame Control word
- Add up the field lengths
- Prove the FCS is a real CRC-32
- Read the MCS PHY rate
Project: Design a Wireless Link
Design one link, end to end
What you will do
- Modulation: the error rate
- Antenna: the beamwidth
- Link: does it close?
- Link: how fast?
Demos
Visualize EM waves
From lesson A Brief History of Wireless Communication
Move one knob — the frequency — and watch the wavelength λ = c/f, the period T = 1/f, the photon energy E = h f and the band all recompute, with a transverse E-and-B wave that packs in more cycles as the frequency climbs and a marker that walks the spectrum.
Build and combine sine waves
From lesson Anatomy of a Sine Wave
Add two or three sinusoids and watch their sum, added point by point. Slide two frequencies close and a slow beat appears at |f₁−f₂|; set two equal tones in phase and they add to A₁+A₂, anti-phase and they cancel. The beat frequency, carrier, envelope and combined peak amplitude are all measured off the samples.
Modulate and demodulate an AM signal
From lesson Why We Need Modulation
Build a standard AM signal s(t) = A_c[1 + m·cos(2πf_m t)]cos(2πf_c t) and watch its envelope carry the message, an envelope detector recover it, and the spectrum show a carrier with a sideband at f_c ± f_m. Raise the modulation index m past 1 and the envelope goes negative — the detector clips and distorts. The sideband frequencies, envelope minimum A_c(1−m) and power efficiency m²/(2+m²) are all computed.
Compare AM and FM under noise
From lesson FM
Build an FM signal s(t) = A_c cos(2πf_c t + β sin(2πf_m t)) and read its modulation index β = Δf/f_m and Carson bandwidth 2(Δf + f_m). Add the same seeded noise to an AM and an FM signal and watch a frequency discriminator recover a clean message where an envelope detector gets a noisy one — the 3β²(β+1) SNR advantage above the ~10 dB FM threshold. Widen Δf for more noise immunity but more bandwidth.
2D propagation simulator
From lesson Reflection, Diffraction, Scattering
Drag walls and the transmitter across a floor plan; every wall crossing, mirror reflection and knife-edge diffraction is computed, and the coverage map is redrawn from the geometry.
Wireless channel emulator
From lesson Multipath and Fading
Build a multipath channel tap by tap and watch five linked views: impulse response, phasor sum, envelope over time, frequency response and the distribution the envelope obeys.
Constellation, AWGN and BER
From lesson Constellation Diagrams
Pick a modulation, set the noise, and watch simulated bit errors land on the theoretical curve. Gain error, phase error and Gray coding are separable.
Antenna patterns and phased-array beamforming
From lesson Antenna Arrays and Beamforming
Steer an N-element array by phase alone. Beamwidth, side lobes, grating lobes and directivity are all measured off the computed pattern, never looked up.
Link budget & path-loss explorer
From lesson Link Budget Analysis
Where the power went, how far the link reaches, and how much the choice of propagation model changes the answer. Effective aperture is shown beside the gain knobs.
Multiple-access sandbox
From lesson FDMA, TDMA, CDMA
One time-frequency rectangle shared four ways — FDMA, TDMA, CDMA, OFDMA — with real Walsh codes and a scheduler fairness comparison.
OFDM signal generator
From lesson OFDM
Build an OFDM symbol from subcarriers with a real IFFT, add a cyclic prefix, push it through a channel and read the EVM and ISI back off the receiver.
Decode a WiFi (802.11) frame
From lesson WiFi (802.11)
Take an 802.11 MAC frame apart field by field — Frame Control, Duration, Address 1/2/3, Sequence Control, optional Address 4, body and FCS — and watch the contiguous offsets sum to the total length. Decode the Frame Control word bit by bit into type, subtype and flags; compute the FCS as a real CRC-32 (0xEDB88320) over the bytes and flip one to see it read corrupt; and read an MCS index as a computed 802.11n PHY rate.