Vaisala RVP900

Chapter 6 ______________________________________________________ Processing Algorithms
VAISALA______________________________________________________________________ 239
The radar constant is determined from the characteristics of your radar
(check with the manufacturer if you are unsure of the values). Note that
transmit losses are accounted for in the radar constant, while receiver loss
is usually included in the calculation of I
o
.
If the value of I
o
calculated above was not based on loss-corrected dBm
values, correct I
o
as follows:
Example Calculation of dBZo:
This sample calculation is provided so that programmers can check their
arithmetic. The radar parameters:
The radar constant for this example is,
T Pulse width in microseconds.
θ Horizontal half-power full beamwidth.
φ Vertical half-power full beamwidth.
G Antenna gain (dimensionless) on beam axis.
λ Radar wavelength in cm. 5 cm
P
t
Transmitted power in kW. 500 kW
L
t
Transmit Loss 2 (3 dB)
T Pulse width in microseconds 1 microsecond
θ Horizontal half-power beamwidth in degrees 1 degree
φ Vertical half-power beamwidth in degrees 1 degree
G Antenna gain (dimensionless) on beam axis 19,953 (43.0 dB)
dBI
0 corrected
dBI
0
dBL
Coupler
– dBL
Cable
– dBL
Feed:Coupler
+=
C
2.69 10
16

2

P
t
 G
2
----------------------------------L
t
2.69 10
16
5
2
5001119 953
2
-------------------------------------------------------- 2.0==
6.76 10
6
mm
6
m
3–
km
2–
mW
1–
=