Definition
Radar detects objects using radio wave reflections:
\text{Transmit χ-modes} \rightarrow \text{Target} \rightarrow \text{Reflected χ-modes}
In SCU terms: Radar transmits electromagnetic χ-modes and measures their reflections from targets—extracting distance and velocity from time delay and Doppler shift.
Radar Principle
\text{Round-trip time: } t = \frac{2R}{c} \rightarrow R = \frac{ct}{2}
Time delay reveals distance. Doppler shift reveals velocity.
Radar Equation
Received χ-mode power:
P_r = \frac{P_t G^2 \lambda^2 \sigma}{(4\pi)^3 R^4}
Power decreases as R⁴—distant targets are very faint.
χ-Mode Information
| Measurement | χ-Mode Property |
|---|---|
| Range | Round-trip χ-mode delay |
| Velocity | Doppler χ-mode shift |
| Direction | χ-mode arrival angle |
| Size | χ-mode cross-section |
Radar Types
| Type | χ-Mode Method |
|---|---|
| Pulsed | Time-of-flight χ-mode delay |
| CW | Continuous Doppler χ-mode shift |
| SAR | Synthetic aperture χ-mode imaging |
| Phased array | Electronic χ-mode beam steering |
Signal Processing
| Technique | Purpose |
|---|---|
| Pulse compression | Improve range resolution |
| Doppler filtering | Velocity discrimination |
| CFAR | Adaptive χ-mode threshold |
| Track-while-scan | Target χ-mode tracking |
Applications
| Application | χ-Mode Target |
|---|---|
| Air traffic | Aircraft χ-mode signatures |
| Weather | Precipitation χ-mode scattering |
| Automotive | Vehicle/obstacle χ-modes |
| Planetary | Surface χ-mode mapping |
The Key Insight
Radar is active χ-mode sensing.
Probing with electromagnetic χ-modes:
- Transmit known χ-mode waveform
- Target reflects χ-modes back
- Delay reveals distance
- Doppler reveals motion
Radar creates its own χ-mode illumination, then measures how targets modify those χ-modes—active sensing rather than passive detection.