User's Manual Part 2

Processing Algorithms (draft)
RVP8 User’s Manual
April 2003
5–47
5.7.7 Case 3: Alternating H/V Transmit: Single-Channel Receiver
Input Receiver Samples
This is the traditional ZDR radar with a high-power fast switch that alternates between
horizontal and vertical on each pulse. The switch is made just prior to the transmit pulse so that
the transmitter radiates and then receives at a single polarization for each pulse. Thus the
samples are:
s
1
hh
s
2
vv
s
3
hh
. . . s
M)1
vv
For the discussion below we will assume that there are M+1 total samples with M/2 horizontal
pulses indexed by (1, 2, 3...M–1) and M/2+1 vertical pulses indexed at (2, 4, 6, ...M). Note that
the processor does not assume that the first pulse in a sequence is horizontal.
Calculation of the Polarization Measurands
The processing is done in pulse pair with optional clutter filter. Again, for accurate ZDR
measurements, the clutter filter may interfere.
The RVP8 calculates the following:
ZDR + 10ĄLOGĄ
ƪ
S
hh
S
vv
ƫ
ZDR + 10ĄLOGĄ
ƪ
t |s
hh
|
2
u*N
h
t |s
vv
|
2
u*N
v
ƫ
Ą ) GDR
PHIDP +
1
2
Ą argĄ
ƪ
R
a
ĄR
*
b
ƫ
RHOHV +
|ò
hv
(T
s
)|
Ą
ƪ
ò
hv
(2T
s
)
ƫ
0.25
KDP based on least squares fit to PHIDP (see Section 5.7.10).
where the following definitions are used:
|ò
hv
(T
s
)| +
|R
a
| ) |R
b
|
2 S
hh
S
vv
Ǹ
ò(2T
s
) +
Ť
ȍ
Mń2 *1
n+1
(s
*
hh
[2n * 1]Ąs
hh
[2n ) 1]Ą )Ą s
*
vv
[2n]Ąs
vv
[2n ) 2])
Ť
(Mń2 * 1)(S
hh
) S
vv
)
R
a
+
1
Mń2
ȍ
Mń2
n+1
s
2n*1
hh
* s
2n
vv
and R
b
+
1
Mń2
ȍ
Mń2
n+1
s
2n
vv
* s
2n)1
hh
The calculation of the channel powers (t |s
hh
|
2
u and t |s
vv
|
2
u) is done using alternating
pulses in this case. Note that in the calculation of R
b
, the RVP8 uses the extra M+1 sample. The
gain terms cancel in the calculation of ρ so in the implementation they are simply assumed to be
=1.