Chapter 8
Coherent Radar Systems
In NCRS systems examined above, target detection and its parameters measurement
are performed based on envelope analysis of reflected oscillations, pick-out by envelope detector. High-frequency pulse filling is used as a carrier frequency that transports information on target to the radar receiver, and as a means of optimal energy
storage of a single pulse in the resonant circuits of IFA. All phase and frequency
information on target, which is contained in the sequence (burst) of pulses, reflected
from a target, is destroyed.
Naturally, that incomplete use of possible information on target, contained in highfrequency filling, leads to energy losses in a signal and to decrease of radar observation efficiency. The signal-to-noise ratio in receiving path of the radar decreases, the
minimum required input signal-to-noise ratio, i.e., the station coefficient of discrimination, increases. The main physical process in NCRS, which degrades a signal detection at background of noise, is a suppression of each of burst pulses with noise in a
nonlinear element—an envelope detector. At weak single pulses, the signal-to-noise
ratio at detector output decreases as compared to input.
Failure to use the information on target contained in the high-frequency filling
leads to another defect of NCRS—its poor protection from highly correlated
(compared to receiver noise) passive interference: reflections from local objects,
reflections from hydrometeors, the sea surface, metallized tapes. Interfering reflections from stationary or slowly moving objects can significantly disrupt the normal
operation of ground-based, air-borne, ship-borne and other radars.
The radar efficiency increases significantly upon the transition from non-coherent
receiving to coherent receiving, which allows, to one degree or another, to extract
additional information on target, contained in high-frequency filling of pulse burst.
To implement coherent receiving in a pulsed radar, it is fundamentally necessary
to have three oscillations that are coherent with each other: a sounding oscillation, a
receiving oscillation, a reference oscillation in receiver, intended for comparison in
phase or in frequency with the received oscillation.
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021
D. A. Akmaykin et al., Theoretical Foundations of Radar Location
and Radio Navigation, Springer Aerospace Technology,
https://doi.org/10.1007/978-981-33-6514-8_8
157
Coherent Radar Systems
In NCRS systems examined above, target detection and its parameters measurement
are performed based on envelope analysis of reflected oscillations, pick-out by envelope detector. High-frequency pulse filling is used as a carrier frequency that transports information on target to the radar receiver, and as a means of optimal energy
storage of a single pulse in the resonant circuits of IFA. All phase and frequency
information on target, which is contained in the sequence (burst) of pulses, reflected
from a target, is destroyed.
Naturally, that incomplete use of possible information on target, contained in highfrequency filling, leads to energy losses in a signal and to decrease of radar observation efficiency. The signal-to-noise ratio in receiving path of the radar decreases, the
minimum required input signal-to-noise ratio, i.e., the station coefficient of discrimination, increases. The main physical process in NCRS, which degrades a signal detection at background of noise, is a suppression of each of burst pulses with noise in a
nonlinear element—an envelope detector. At weak single pulses, the signal-to-noise
ratio at detector output decreases as compared to input.
Failure to use the information on target contained in the high-frequency filling
leads to another defect of NCRS—its poor protection from highly correlated
(compared to receiver noise) passive interference: reflections from local objects,
reflections from hydrometeors, the sea surface, metallized tapes. Interfering reflections from stationary or slowly moving objects can significantly disrupt the normal
operation of ground-based, air-borne, ship-borne and other radars.
The radar efficiency increases significantly upon the transition from non-coherent
receiving to coherent receiving, which allows, to one degree or another, to extract
additional information on target, contained in high-frequency filling of pulse burst.
To implement coherent receiving in a pulsed radar, it is fundamentally necessary
to have three oscillations that are coherent with each other: a sounding oscillation, a
receiving oscillation, a reference oscillation in receiver, intended for comparison in
phase or in frequency with the received oscillation.
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021
D. A. Akmaykin et al., Theoretical Foundations of Radar Location
and Radio Navigation, Springer Aerospace Technology,
https://doi.org/10.1007/978-981-33-6514-8_8
157