0
-0.2
INSERTION LOSS (dB)
-0.4
-0.6
-0.8
-1.0
1
2
3
4
5
6
FREQUENCY (GHz)
ISOLATION (dB)
Figure 16. Insertion loss of reference line.
Normalization was used to remove
the pcb’s and connectors’ losses
from the measurement of the
shunt switch’s loss. The active
trace was divided by the memo-
rized trace (Data/Memory) to
produce the normalized data. At
zero bias, the insertion loss was
under 0.6 dB up to 6 GHz (Figure
18). Applying a reverse bias to the
PIN diode has the effect of
reducing its parasitic capacitance.
With a reverse bias of -20V, the
insertion loss improved to better
than 0.5 dB (Figure 19).
0
The PIN diode’s resistance is a
function of the bias current. So, at
higher forward current, the
isolation improved. The combina-
tion of the HMPP-389T and the
SK063A demoboard exhibited
more than 17 dB of isolation from
1 to 6 GHz at If
≥
1mA (Figure 20).
-10
0.15 mA
-14 0.25 mA
0.5 mA
-18 1 mA
-22 1.5 mA
To evaluate the HMPP-389T as
shunt switch, it was mounted on
the test line and then the appropri-
ate biasing voltage was applied. In
our prototype, the worst case
return loss was 10 dB at 5 GHz
(Figure 17). The return loss varied
very little when the bias was
changed from zero to -20V.
-5
-26
-0.2
INSERTION LOSS (dB)
20 mA
-30
1
-0.4
2
3
4
5
6
FREQUENCY (GHz)
-0.6
Figure 20. Isolation at different frequencies
with forward current as a parameter.
-0.8
-1.0
1
2
3
4
5
6
FREQUENCY (GHz)
-15
RETURN LOSS (dB)
Figure 18. Insertion loss of HMPP-389T at 0V.
-25
0
-35
-0.2
INSERTION LOSS (dB)
The combination of the
HMPP-389T and the demo-board
allows a high performance shunt
switch to be constructed swiftly
and economically. The extremely
low parasitic inductance of the
package allows the switch to
operate over a very wide fre-
quency range.
-45
-0.4
-55
1
2
3
4
5
6
FREQUENCY (GHz)
-0.6
Figure 17. Return loss of HMPP-389T mounted
on test line at 0V and -20V bias.
-0.8
-1.0
1
2
3
4
5
6
FREQUENCY (GHz)
Figure 19. Insertion loss of HMPP-389T at -20V.
7
AGILENT [ AGILENT TECHNOLOGIES, LTD. ]
