Electronic Warfare and Radar Systems Engineering Handbook
- Propagation Time / Resolution -

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PROPAGATION TIME /

RESOLUTION

1. ROUND TRIP RANGE: with t = time to reach target

                        Rules of Thumb

2. ONE WAY RANGE: R = ct with t = time to reach target

3. UNAMBIGUOUS RANGE

(DISTANCE BETWEEN PULSES):

Normally a radar measures "distance" to the target by measuring time from the last transmitted pulse. If the interpulse period (T) is long enough that isn't a problem as shown in "A" to the right. When the period is shortened, the time to the last previous pulse is shorter than the actual time it took, giving a false (ambiguous) shorter range (figure "B").

       Rules of Thumb

       RNM ≈ 81Pms

       RKm ≈ 150Pms

    Where Pms is PRI in milliseconds

4. RANGE RESOLUTION

             Rules of Thumb

   500 ft per microsecond of pulse width

   500 MHz IF bandwidth provides 1 ft of resolution.

5. BEST CASE PERFORMANCE:

    The atmosphere limits the accuracy to 0.1 ft

    The natural limit for resolution is one RF cycle.

Table of Contents for Electronics Warfare and Radar Engineering Handbook

Introduction | Abbreviations | Decibel | Duty Cycle | Doppler Shift | Radar Horizon / Line of Sight | Propagation Time / Resolution | Modulation | Transforms / Wavelets | Antenna Introduction / Basics | Polarization | Radiation Patterns | Frequency / Phase Effects of Antennas | Antenna Near Field | Radiation Hazards | Power Density | One-Way Radar Equation / RF Propagation | Two-Way Radar Equation (Monostatic) | Alternate Two-Way Radar Equation | Two-Way Radar Equation (Bistatic) | Jamming to Signal (J/S) Ratio - Constant Power [Saturated] Jamming | Support Jamming | Radar Cross Section (RCS) | Emission Control (EMCON) | RF Atmospheric Absorption / Ducting | Receiver Sensitivity / Noise | Receiver Types and Characteristics | General Radar Display Types | IFF - Identification - Friend or Foe | Receiver Tests | Signal Sorting Methods and Direction Finding | Voltage Standing Wave Ratio (VSWR) / Reflection Coefficient / Return Loss / Mismatch Loss | Microwave Coaxial Connectors | Power Dividers/Combiner and Directional Couplers | Attenuators / Filters / DC Blocks | Terminations / Dummy Loads | Circulators and Diplexers | Mixers and Frequency Discriminators | Detectors | Microwave Measurements | Microwave Waveguides and Coaxial Cable | Electro-Optics | Laser Safety | Mach Number and Airspeed vs. Altitude Mach Number | EMP/  Aircraft Dimensions | Data Busses | RS-232 Interface | RS-422 Balanced Voltage Interface | RS-485 Interface | IEEE-488 Interface Bus (HP-IB/GP-IB) | MIL-STD-1553 & 1773 Data Bus |

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