Week 2 Theory Flashcards
(78 cards)
What is frequency diveristy
When a radar transmits 2 or more frequencies simultaneously
What is frequency agility
When a radar switches between multiple frequencies in a controlled manner
Benifits of frequency agility
Good anti clutter
Eliminates second time round returns
Different material reflect different frequencies better than others
Benefits of continuous wave
Good for doppler
High average power
Narrow bandwidth
Disadvantages of continuous wave
Cant calculate range
Separate transmitter and receiver needed
What is frequency modulated continuous wave (FMCW)
Radar transmits continuously but changes freq over time
What is Interrupted continuous wave (ICW)
CW signal that gets interrupted not stopped so that the phase of the signal remains coherent
Types of inter pulse modulation
Stagger
Dwell and switch
Jitter
Agility
Types of stagger
Simple- seven or less
Complex- more than seven
What is switch and dwell
PRI is set for a number of pulses and then switches to a different freq for a number of pulses
Types of jitter
Discrete
Random
Firing order def
Order in which PRIs are transmitted
Element def
Describes an individual PRI
Positions def
Total number of PRIs in a cycle
Cycle length def
Time it takes to go through 1 sequence
Cycle rate def
Number of times a sequence is repeated in a second
Mean PRI def
Average of all positions in a cycle
What is UMOP
Unintentional modulation on pulse
Knows as SEI or fingerprinting
What is FMOP
Frequency modulation on pulse
What is FMOP used for
Varying frequency over the pulses length (sweep) allows for better range resolution
What is doppler
Apparent shift in frequency as an object moves towards or away from and observer
What is coherence
Continuity of phase from one signal to the next
What is doppler notch
When the velocity of a contact is bellow which a radar classes them as clutter and does not identify them
Tangental fade
Reducing of doppler due to a reduction in radial velocity