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30 Cards in this Set

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Radar-
Pulse Modulation:

"S.H.E.R.1"
1. Transmits Very Short pulses
2. Transmits High Power pulses
3. Waits for Echo.
4. Measures elapsed time = Range
5. Pulse Radar uses 1 antenna for XMIT and RCV.
Radar-
Frequency Modulation:

"CC.Fix.E.R.S"
1. Transmits Radio Waves
2. CONTINUALLY CHANGES up and down in frequency, from a FIXED REFERENCE frequency.
3. Echo signal, will differ from XMIT frequency.
4. Elapsed time = Range
5. Frequency modulation FAVORED for STATIONARY targets.
Radar-
Continuous Wave Modulation:

"2.M=R.M=EvX.MG."
1. Transmits WAVE OF ENERGY.
2. Requires TWO SEPERATE antennas.
3. CANNOT differentiate range UNLESS wave is MODULATED.
4. Modulation = difference in xmit & echo frequencies.
5. Normal usage = MISSILE GUIDANCE.
Radar-
Pulse Doppler Modulation:

"P+F.X->FRWP.E+CWr=InPwX.Ph=+/- Motion."
1. Combines PULSE & FREQUENCY modulation.
2. Emits fixed FREQUENCY RADIO WAVE PULSES.
3. Echo = Range
4. Echo mixed with stable CW reference; locked IN PHASE with XMITED pulse.
5. PHASE DIFFERENCE = target motion.
Radar-
Power Supplies:

Low.High.Xmitter
1. Low power Power supplies divided into particular cabinets.
2. High Power is usually in xmitter where xmitter amplifies and converts power into pulses.
Radar-
Synchronizer/Modulator:
1. Trigger Pulses for:
- Xmitter
- Indicator Sweeps
- Ranging Circuits
2. Timing Ps. ensure synchronization throughout radar. Which are married to the PRF (Pulse Repetition Frequency).
3. PRF is set by Stable Oscillator (SO); sine-wave oscillator, multivibrator,or a blocking oscillator.
4. Output of the SO is sent to pulse shaping circuits to produce Timing Pulses (TP's).

1. Modulator can be seperate from SYNCHRO.
2. Primarily: MOD controls Radar Pulse WIDTH by use of a RECTANGULAR DC pulse (Modulator Pulse). PeakPower of XMITpulse depends on AMP of MODpulse.
Radar-
Transmitter:
1. Uses High-Power microwave oscillator. (HP-MICRO.SO)
- i.e. Magnetron
- (HP MICRO-AMP) i.e. Klystron
2. Oscillator or Amplifier - Requires PROPERLY TIMED, HIGH-amplitude, RECTANGULAR pulse...as operating power.
3. Duplexer.
Radar-
Antenna/Duplexer:
1. Receives echo pulse.
2. Amplifies entire signal.
3. Detects pulses.
4. Amplifies Pulses.
5. Decreases overall frequency to IF.
6. Routes signal to Indicator.
Radar-Types
Air:

Peak Power? Pulse Repetition Rate? Pulse Width?
Peak Power - High; for longer distances and faster moving targets than surface.
Pulse Repetition rate - Low; Provide enough travel time for echo return for longer distance targets.
Pulse Width - Wide; Detect further lengths of distance from own ship.
Radar-Types
Surface:

Range? Pulse Width? Pulse Repetition Rate? Peak Power? Vertical Beam? Horizontal Beam?
Range - LOS, radar horizon.
Pulse Width - Narrow; high degree of range resolution.
Pulse Repetition Rate - High; maximum definition of targets.
Peak Power - Medium; Permit detection of small objects.
Vertical Beam - Wide; Compensation for pitch and roll.
Horizontal Beam - Narrow; Permits accurate bearing determination.
Radar-Types
Fire Control:

Pulse Repetition? Pulse Width? Beam Width?
Pulse Rep - HIGH; maximum definition of targets.
Pulse Width - VERY narrow; Maximize range resolution.
Beam Width - VERY narrow; maximize bearing resolution.

Fire-Control radars use a very narrow circular beam which provides extremely accurate detection of Range, Bearing, and Elevation. Fire-Control Radar's are the only type of Radar that provide Elevation data among the types of Radar.
Radar-Types
Navigation:
Navigation Radars are primarily designated as Surface search radars with very good bearing and range resolution.
Radar-Types
Airborne:

B.I.S.A.N.
Bombing
Intercept and Missile Control
Search
Airborne early warning
Navigation
Radar-Limitations
Minimum Range
Range = Elapsed Time/12.36micro seconds

Because, RF travels at the speed of light, light takes 6.18 micro seconds to travel one Nautical mile.
Radar-Limitations
Maximum Range

CW, Ppk (XMITpulse), PRR/PRF, Receiver Sensitivity.
Calculated by the reciprocal of PRF divided by 12.36 micro seconds.

1/PRF dvided by 12.36 micro seconds = MAXrange
Radar-Limitations
Ambiguous Returns
Ambiguous returns are Echo pulses that reach the receiver after the leading edge of the following pulse. Ambiguous pulses are coined as such, because if they were to appear on a PPI, they would indicate an incorrect Range. Therefore, in order for no Ambiguous returns to be displayed on the PPI, the Timing Pulse for the Radar MUST BE RESET to 0, after each pulse.
Radar-Limitations
PRF
Pulse Repetition Frequency; PRIMARY limiting factor for Maximum Range

Amount of time taken in one second to produce one XMIT pulse.

Essential for calculating MAXrange due to it's reciprocal being equal to PRT; Pulse Repletion Time.
Radar-Limitations
PRT
Pulse Repletion Time; The total time for a XMIT pulse to be emitted from the Transmitter and Received.
Radar-Limitations
Peak Power
The MAXrange of a Radar is directly related to the amount of Power (RF energy) in a Waveform (pulse amplitude).

Ppk is determined by dividing Pavg by the DUTY CYCLE.

Ppk = Pavg/DutyCycle
Radar:
Duty Cycle
Duty Cycle: Pulse Width divided by Pulse repetition time.

PW/PRT = Duty Cycle.
Radar-Limitations
Average Power
Average power is the measurement of power over the entire Pulse Repletion Time.

Pavg = Ppk x PW x PRF
Radar-Limitations
Ducting
Temperature Inversion and/or Moisture Lapse; causing a large change in the REFRACTION INDEX of the lowest few hundred feet in the atmosphere.

Ducting will cause Radar horizons to be either INCREASED or DECREASED; depending on the direction the Radar waves are bent; REFRACTED.
Radar-Capabilities
Radar Horizon
Targets must be within the Line-Of-Sight (LOS) of a radar to be detected.

LOS = Square root of antenna height (in feet) by 1.25. Result is distance in Nautical Miles.
Radar-Capabilities
(MDS) Minimum Discernible Signal
This is the weakest usable signal te receiver can detect. The weaker the usable input signal, the more sensitive the receiver.
Radar-Capabilities
Range Resolution
Target Resolution is the capability a Radar has to discerning between two closely grouped targets. This is all dependent upon the pulse width of the XMIT pulse. Range

Resolution = PW x 164 yards.
Radar-Capabilities
Bearing Resolution
Bearing (Azimuth) Resolution is entirely dependent upon the width of the XMIT beam AND Target Range. Due to Beam width increasing of course as distance increases, distance will most decisively play a part. Two targets of the same range must be separated by at least one beam width to be identified as two individual targets.
Radar-Capabilities
Radar Accuracy
Range, Bearing, & Height.

Besides Atmopheric conditions, corrosion control, and weather proofing, Range of a Target is mostly dependent upon PULSE SHAPE. SQUARE waves are ideal. Smaller PW's at closer Ranges are needed to allow the least allowable delay in transition from Transmitter to Receiver by Duplexer which is mostly dependent upon the PW of a XMIT pulse.
Radar-SPS/67

Transmitter Frequency
5450 to 5825 MHz
Radar-SPS/67

Pulse Widths
1.0 µsec (Long), 0.25 µsec (Medium), 0.1 µsec (Short)
Radar-SPS/67

Peak Power
135kWatts - 285kWatts