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

[Go to TOC]

 

PROPAGATION TIME /

RESOLUTION

1. ROUND TRIP RANGE: RF Cafe - Round trip range equation with t = time to reach target

                        Rules of Thumb

In one μsec round trip time, a wave travels to and from an object at a distance of: The time it takes to travel to and from an object at a distance of:
≈ 150 m

≈ 164 yd

≈ 500 ft

≈ 0.08 NM

≈ 0.15 km

≈ 1 m ≈ 0.0067 μsec

≈ 1 yd ≈ 0.006 μsec

≈ 1 ft ≈ 0.002 μsec

≈ 1 NM ≈ 12.35 μsec

≈ 1 km ≈ 6.7 μsec

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

 

Time Distance Traveled   Distance Time it Takes
1 milli sec (ms) 165 NM 1 NM 6.18 μsec
1 micro sec (μs) 1000 ft 1 km 3.3 μsec
1 nano sec (ns) 1 ft 1 ft 1 nsec

3. UNAMBIGUOUS RANGE

Radar range diagram - RF Cafe(DISTANCE BETWEEN PULSES):RF Cafe - Unambiguous range equeation

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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About RF Cafe

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Copyright: 1996 - 2024

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    BSEE - KB3UON

RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while tying up your telephone line, and a nice lady's voice announced "You've Got Mail" when a new message arrived...

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