Page 352 - Fundamentals of Radar Signal Processing

PRF modes where there are no range ambiguities.

Staggered PRI operation can be analyzed in terms of either the PRIs or the
corresponding PRFs. The former is more direct and is used here. Consider a
system using P staggered PRIs {T , T , …, T }. The corresponding set of pulse
1
0
P–1
repetition intervals is {PRF } = {1/T }. Assume that each of the PRIs is
p
p
selected as an integer multiple of a base interval T ,
g
(5.33)

with corresponding PRFs, PRF = 1/T and F = 1/T . This is reasonable for
p
p
g
g
many radar systems, where T may correspond to the fast-time sampling interval
g
and the set of integers {k } to the number of range bins in each PRI. The {k }
p
p
3
are called the staggers and the ratio k : k of any two of them is called a
m
p
stagger ratio. In many practical cases the staggers are chosen to be relatively
prime integers.
For a given PRI, any MTI filter will exhibit blind Doppler frequencies at
all integer multiples of the corresponding PRF. Consequently, the first true blind
Doppler frequency F of a system using staggered PRIs will be the lowest
bs
frequency that is blind at all of the corresponding PRFs, i.e., the least common
multiple (LCM) of the set

(5.34)

A complete cycle through the set of PRIs takes a total period T equal to the
tot
sum of each of the staggered PRIs

(5.35)

It is of interest to determine how much the blind Doppler of the staggered
system is increased relative to a comparable unstaggered system. A reasonable

choice for an unstaggered system to serve as a baseline reference is one whose
PRI equals the average PRI of the staggered system. The time required to collect
N pulses will then be approximately the same for the two systems. The average
PRI is

(5.36)