9 Compensation of Signals from Stationary Objects
177
Fig. 9.9 Timing diagrams of MTI circuit
non-fluctuating; otherwise, uncompensated residues may appear at the output of
MTI unit in the interference zones.
Modulation of video pulses of a moving target with the Doppler frequency is the
basis for the operation of pulsed MTI systems. However, at certain target velocities,
called blind speeds, such modulation is absent, resulting in target loss (lorry of lockon). The condition of modulation absence means the equality in amplitude of target
video pulses at the output of phase detector, spaced from each other by the repetition
period:
cos V t = cos( V (t − T )),
(9.11)
or
cos V t = cos( V (t − T )) + 2π n, n = 0, 1, 2, . . .
(9.12)
Blind speeds will occur when
177
Fig. 9.9 Timing diagrams of MTI circuit
non-fluctuating; otherwise, uncompensated residues may appear at the output of
MTI unit in the interference zones.
Modulation of video pulses of a moving target with the Doppler frequency is the
basis for the operation of pulsed MTI systems. However, at certain target velocities,
called blind speeds, such modulation is absent, resulting in target loss (lorry of lockon). The condition of modulation absence means the equality in amplitude of target
video pulses at the output of phase detector, spaced from each other by the repetition
period:
cos V t = cos( V (t − T )),
(9.11)
or
cos V t = cos( V (t − T )) + 2π n, n = 0, 1, 2, . . .
(9.12)
Blind speeds will occur when