6.1 Detection of Radio Signals
137
Values of R parameter also numerically equal to a relation of maximum peak
power of output signal of matched filter at input of threshold unit to average noise
power at output of matched filter:
Q avn.out =
P s.max
P n
out
= R
(6.21)
If we evaluate an average power of signal P m. f at output of matched filter per
period of HF oscillations, then, as is known:
P m. f =
P s.max
2
(6.22)
In this case, at input of threshold unit a signal-to-noise relation equals:
Q sn.av =
P s.av
P n
=
P s.max
2P n
=
Q sn.out
2
=
R
2
=
E
N 0
.
(6.23)
Operation of real radar systems largely differs from those ideal conditions, at
which targets detection is carried out at least energy of incoming from a target signal
(least value R = 2E/N o ) to provide target detection with specified probability.
At targets detection in real radar systems, in general case, a large signal energy is
required, and consequently, it is necessary to have a large signal-to-noise ratio R at
input of the system at similar required probabilities P cd and P f a .
At practical application of conclusions of the targets detection theory in radar
location, the main objective is a determining of required for target detection energy
of reflected from a target signal. To solve the mentioned task is possible by two
following approaches.
Firstly, to compose a full signal (passing) and noises model in any given radar
system and find density probabilities distribution of output signals for different
hypothesis before threshold unit. By further plotting the real characteristics of detection, it is possible to determine a real value of relation R for ensuring of required
probabilities P cd and P f a . However, the mentioned approach has an essential disadvantage in that there could be a huge amount of real radar model variants and it
becomes very difficult and lengthy to solve this problem. Besides, in some cases it
is difficult to formalize some nodes of radar model for rigorous solution of detection
problem.
The second solution approach concludes in that an objective is divided into several
stages. Firstly, decreasing level of signal-to-noise ratio at coming through any typical
block or node of real radar structure is to be found, or we should determine at how
many times the required signal energy will increase at radar input, reflected from a
target, at considering of different deviations from ideal conditions of operation in the
examined structure or node.
As it was mentioned before, to consider the pointed deviations the coefficient
(factor) of losses in α ls system is introduced. Coefficient of losses α ls shows, at how
137
Values of R parameter also numerically equal to a relation of maximum peak
power of output signal of matched filter at input of threshold unit to average noise
power at output of matched filter:
Q avn.out =
P s.max
P n
out
= R
(6.21)
If we evaluate an average power of signal P m. f at output of matched filter per
period of HF oscillations, then, as is known:
P m. f =
P s.max
2
(6.22)
In this case, at input of threshold unit a signal-to-noise relation equals:
Q sn.av =
P s.av
P n
=
P s.max
2P n
=
Q sn.out
2
=
R
2
=
E
N 0
.
(6.23)
Operation of real radar systems largely differs from those ideal conditions, at
which targets detection is carried out at least energy of incoming from a target signal
(least value R = 2E/N o ) to provide target detection with specified probability.
At targets detection in real radar systems, in general case, a large signal energy is
required, and consequently, it is necessary to have a large signal-to-noise ratio R at
input of the system at similar required probabilities P cd and P f a .
At practical application of conclusions of the targets detection theory in radar
location, the main objective is a determining of required for target detection energy
of reflected from a target signal. To solve the mentioned task is possible by two
following approaches.
Firstly, to compose a full signal (passing) and noises model in any given radar
system and find density probabilities distribution of output signals for different
hypothesis before threshold unit. By further plotting the real characteristics of detection, it is possible to determine a real value of relation R for ensuring of required
probabilities P cd and P f a . However, the mentioned approach has an essential disadvantage in that there could be a huge amount of real radar model variants and it
becomes very difficult and lengthy to solve this problem. Besides, in some cases it
is difficult to formalize some nodes of radar model for rigorous solution of detection
problem.
The second solution approach concludes in that an objective is divided into several
stages. Firstly, decreasing level of signal-to-noise ratio at coming through any typical
block or node of real radar structure is to be found, or we should determine at how
many times the required signal energy will increase at radar input, reflected from a
target, at considering of different deviations from ideal conditions of operation in the
examined structure or node.
As it was mentioned before, to consider the pointed deviations the coefficient
(factor) of losses in α ls system is introduced. Coefficient of losses α ls shows, at how