[vcp,vcpangles]
= radarvcd(freq,rfs,anht) calculates
the vertical coverage pattern of a narrowband radar antenna. The Vertical Coverage Pattern is the radar's
range, vcp, as a function of elevation angle, vcpangles.
The vertical coverage pattern depends upon three parameters. These
parameters are the radar's maximum free-space detection range, rfs,
the radar frequency, freq, and the antenna height, anht.

[vcp,vcpangles]
= radarvcd(___,Name,Value) allows you to specify
additional input parameters as Name-Value pairs. You can specify additional
name-value pair arguments in any order as (Name1,Value1,...,NameN,ValueN).
This syntax can use any of the input arguments in the previous syntax.

radarvcd(___) displays the
vertical coverage diagram for a radar system. The plot is the locus
of points ofmaximum radar range as a function of target elevation.
This plot is also known as the Blake chart.
To create this chart, radarvcd invokes the function blakechart using default parameters.
To produce a Blake chart with different parameters, first call radarvcd to
obtain vcp and vcpangles.
Then, call blakechart with user-specified parameters.
This syntax can use any of the input arguments in the previous syntaxes.

Set the frequency to 100 MHz, the antenna height to 10 m, and the free-space range to 200 km. The antenna pattern, surface roughness, antenna tilt angle, and field polarization assume their default values as specified in the AntennaPattern, SurfaceRoughness, TiltAngle, and Polarization properties.

Obtain an array of vertical coverage pattern values and angles.

Set the frequency to 100 MHz, the antenna height
to 10 m, and the free-space range to 200 km. The antenna pattern is
a sinc function with 45° half-power width. The surface roughness
is set to 1 m. The antenna tilt angle is set to 0°, and the field
polarization is horizontal.

Plot the range-height-angle curve (Blake Chart) for a radar with a user-specified antenna pattern.

Define a sinc-function antenna pattern with a half-power beamwidth of 90 degrees.

pat_angles = linspace(-90,90,361)';
pat_u = 1.39157/sind(90/2)*sind(pat_angles);
pat = sinc(pat_u/pi);

Specify a radar that transmits at 100 MHz. The free-space range is 200 km, the antenna height is 10 meters, the antenna tilt angle is zero degrees, and the surface roughness is one meter.

Radar antenna height specified as a real-valued scalar. Height
units are set by the HeightUnit Name-Value pair.

Example: 10

Data Types: double

Name-Value Pair Arguments

Specify optional comma-separated pairs of Name,Value arguments.
Name is the argument
name and Value is the corresponding
value. Name must appear
inside single quotes (' ').
You can specify several name and value pair
arguments in any order as Name1,Value1,...,NameN,ValueN.

Radar range units denoting kilometers, nautical miles, miles,
feet or meters. This name-value pair specifies the units for the free-space
range argument, rfs, and the output vertical
coverage pattern, vcp.

Antenna height units denoting meters, nautical miles, miles,
kilometers, or feet. This name-value pair specifies the units for
the antenna height, anht, and the 'SurfaceRoughness' name-value
pair.

Dielectric constant of reflecting surface specified as complex-valued
scalar. When omitted, the dielectric constant is taken from a frequency-dependent
seawater dielectric model derived in Blake[1].

Surface roughness specified as a non-negative real scalar. Surface
roughness is a measure of the height variation of the reflecting surface.
The roughness is modeled as a sinusoid wave with crest-to-trough height
given by this value. A value of 0 indicates a smooth surface. The
units for surface roughness height is specified by the value of the 'HeightUnit' Name-Value
pair.

Antenna elevation pattern, specified as a real-valued N-by-1
column vector. Values for 'AntennaPattern' must
be specified together with values for 'PatternAngles'.

ath = linspace(-pi/2, pi/2, 361);
HPBW = 10*pi/180;
k = 1.39157/sin(HPBW/2);
u = k*sin(ath);
apat = sinc(u/pi);

Antenna pattern elevation angles specified as a real-valued N-by-1
column vector. The size of the vector specified by 'PatternAngles' must
be the same as that specified by 'AntennaPattern'.
Angle units are expressed in degrees and must lie between –90°
and 90°. In general, to properly compute the coverage, the antenna
pattern should fill the whole range from –90° to 90°.

Antenna tilt angle specified as a real-valued scalar. The tilt
angle is the elevation angle of the antenna with respect to the surface.
Angle units are expressed in degrees.

Maximum elevation angle, specified as a real-valued scalar.
The maximum elevation angle is the largest angle for which the vertical
coverage pattern is calculated. Angle units are expressed in degrees.

Vertical coverage pattern returned as a real-valued, K-by-1
column vector. The vertical coverage pattern is the actual maximum
range of the radar. Each entry of the vertical coverage pattern corresponds
to one of the angles returned in vcpangles.

The maximum detection range of a radar antenna
can differ, depending on placement. Suppose you place a radar antenna
near a reflecting surface, such as the earth's land or sea surface
and computed maximum detection range. If you then move the same radar
antenna to free space far from any boundaries, a different maximum
detection range would result. This is an effect of multi-path interference
that occurs when waves, reflected from the surface, constructively
add to or nullify the direct path signal from the radar to a target.
Multipath interference gives rise to a series of lobes in the vertical
plane. The vertical coverage pattern is the plot of the actual maximum
detection range of the radar versus target elevation and depends upon
the maximum free-space detection range and target elevation angle.
See Blake [1].

References

[1] Blake, L.V. Machine Plotting
of Radar Vertical-Plane Coverage Diagrams. Naval Research
Laboratory Report 7098, 1970.