Page 273 - Radar Technology Encyclopedia

263 mapping, terrain matrix, multiport

Terrain mapping is radar surveying to obtain different types A conductance matrix is a matrix Y, of 2N ports, that estab-
of maps, including topographic. Side-looking radars mounted lishes the relation between N normalized voltages u acting
n
on aircraft or spacecraft and using either real or synthesized on a microwave multiport and the reaction in the form of N
apertures, along with a precision navigational system, are normalized currents :
i
n
used for terrain mapping. The onboard inertial navigation sys-
i = Y N ´ N n
u
n
tem of the aircraft provides a precision on the order of 1m,
·
which makes it possible to create a quality radar image on a The elements of the conductance matrix y mn are deter-
scale of 1:250,000 or 1:100,000. A specific feature of terrain mined with a short-circuit of the inputs, except for the excited
mapping is the reference of the radar image to a topographic one:
·
map. Referencing is done either from special marks whose · i m
·
coordinates are strictly associated with the coordinates of the y mn = -----
u n ·
,
,
platform, or by aligning the radar blips of the character refer- u g = 0 q = 1 N q ¹, n
ence points with the images on the topographic map. A radar The nondiagonal elements are called reciprocal conduc-
mapping system with reproduction of terrain altitude uses tances, the diagonal ones natural conductances. The conduc-
-1
radar interferometers, dual-beam stereoscopic sensors, or sen- tance matrix is the inverse of the impedance matrix Z: Y = Z .
sors which survey the terrain from different directions to IAM
obtain a stereoscopic effect. Ref.: Sazonov (1988), p. 78.
The simplest method of mapping is to obtain a mosaic
The covariance [correlation] error matrix M, of measure-
map. In terrain mapping, radar image correction and decoding ˆ
ments of the vector parameter is composed of values of the
a
are carried out, and joint processing of a large number of
squares of the deviation of its components, a, from their esti-
i
images using television-optical equipment and computers. ˆ
mates, a i , obtained by one method or another:
(See also RADAR, ground-mapping.) IAM
ˆ ˆ
,
,
–
(
Ref.: Mel'nik (1980), p. 169; Reutov (1970), p. 339. M = M ij = á ( a – a i ) a a j )ñ ij ,= 1 N
i
j
MARK, calibration. Calibration marks are “the indications where N is the number of the components of .
a
superimposed on a display to provide a numerical scale of the The correlation error matrix characterizes the quality of
parameters displayed.” An example is a range marker, a refer- the estimate method and is used to determine the fundamental
ence appearing on a display that is delayed by a known accuracy of radar measurement both of independent and of
amount from the transmission, and used to determine the dependent parameters of signals. It is used in the theory of
range of the target by reading visually the relative position of Kalman filtering.
the received signal. SAL The matrix that is the inverse to the correlation error
Ref.: IEEE (1993), p. 150; Barton (1976), p. 38. matrix is called the precision matrix. IAM
MASER (See AMPLIFIER, paramagnetic quantum). Ref.: Shirman (1981), pp. 191, 207.
The impedance matrix is the matrix Z, of a 2N multiport that
MATRIX
establishes the relation between the N normalized currents i
N
beam-forming matrix (see FEED). acting on a microwave multiport and the reaction in the form
The coherence matrix comprises normalized reciprocal cor- of N normalized voltages u N :
relation functions of polarization components of a planar
· · u = Z i
wave (components of the field intensity), E1 t () E2 t (), , in a N N ´ N N
linear polarization base: It is a generalization of the impedance in Ohm’s law for a
·
double-port. The element z mn of the matrix is determined
1 r 11 r 12 · · with excitation of the nth input by an ideal current source, i ,
r = ---------------------- , r = á Ei t () Ej ñ t ij 12 n
,,=
,
ij
r + r
11 22 r 21 r 22 when unloaded (i = 0, q = 1,N, q ¹ n) at the other inputs:
q
where < x > is the averaged value of x over the argument t.
t
·
The coherence matrix completely determines the polar- u m
z = ------
ization state of an electromagnetic wave and can be measured mn ·
i n
,
,
in practice (see POLARIZATION). i q = 0 q = 1 N q ¹, n
To describe a field that is scattered by a long object, a Nondiagonal elements are called reciprocal impedances
more general matrix of space-time correlation functions is of inputs of the multiport, and diagonal ones are called natural
used: impedances. IAM
· · * Ref.: Montgomery (1947), p. 140; Sazonov (1988), p. 77.
,
(
r D r Dt ) á Ei rt ,( ) Ej ( r + D rt + Dt )ñ
,
=
ij rt ,
A multiport matrix is a square matrix with dimensions N ´
where is the space coordinate vector. IAM N, where N is the number of inputs of a microwave multiport,
r
Ref.: Kanareikin (1966), p. 62; Kraszhuk (1988), p. 96. establishing the relation between the action matrix r N on the
multiport and the reaction vector f N . The action and reactions