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HMPP-3890-TR2

P1-P3P4-P6P7-P9P10-P12
7
Figure 13. Soldering details of connector ngers to upper ground plane.
Figure 14. Soldering details of connector ngers to lower ground plane.
Demo-board Preparation
Since the performance of the shunt switch is ultimately
limited by the demo-board, a short discussion of the
constructional aspects will be benecial. Edge-mounted
SMA connectors (Johnson #142-0701-881) were mounted
on both the reference and test lines. A special mounting
technique has been used to minimize reection at the pcb
to connector interface. Prior to mounting, the connector
pins were cut down to two pin diameters in length. Subse-
quently, the connector ngers were soldered to the upper
ground plane (Figure 18). Solder was lled between the
connector body and ngers on the lower ground plane
until the small crescent of exposed teon was completely
covered (Figure 19).
Test Results
Measurements of the reference line’s return and insertion
losses were used to gauge the eectiveness of the VSWR
mitigating steps. In our prototype, the worst case return
loss of the reference line was 20 dB at 5 GHz (Figure 20).
Figure 15. Swept Return Loss of Reference
Line.
FREQUENCY (GHz)
RETURN LOSS (dB)
1 62 4 53
-18
-22
-26
-30
-34
-38
Figure 12. Demo-board DEMO-HMPP-389T.
test line
reference line
Agilent
SK063A
HMPP-389T
Testing the HMPP-389T on the Demo-board
Introduction
The HMPP-389T PIN diode is a high frequency shunt switch.
It has been designed as a smaller and higher performance
version of the HSMP-389T (SC-70 package).
The DEMO-HMPP-389T demo-board allows customers
to evaluate the performance of the HMPP-389T without
having to fabricate their own PCB. Since a shunt switch’s
isolation is limited primarily by its parasitic inductance, the
product’s true potential cannot be shown if a conventional
microstrip pcb is used. In order to overcome this problem,
a coplanar waveguide over ground-plane structure is
used for the demo-board. The bottom ground-plane is
connected to the upper ground traces using multiple
via-holes.
A 50Ω reference line is provided at the top to calibrate the
board loss. The bottom line allows the HMPP-389T diode
to be tested as a shunt switch.
Figure 15. Swept return loss of reference line.
8
To evaluate the HMPP-389T as shunt switch, it was
mounted on the test line and then the appropriate bias-
ing voltage was applied. In our prototype, the worst case
return loss was 10 dB at 5 GHz (Figure 22). The return loss
varied very little when the bias was changed from zero
to -20V.
Figure 19.
Insertion loss of HMPP-389T at -20V.
The PIN diode’s resistance is a function of the bias current.
So, at higher forward current, the isolation improved.
The combination of the HMPP-389T and the SK063A
demoboard exhibited more than 17 dB of isolation from
1 to 6 GHz at If ≥ 1mA (Figure 25).
Figure 17. Return Loss of HMPP-389T
Mounted on Test Line at 0V and -20V Bias.
FREQUENCY (GHz)
RETURN LOSS (dB)
-5
-15
-25
-35
-45
-55
1 62 4 53
Figure 18. Insertion Loss of HMPP-389T at
0V.
FREQUENCY (GHz)
INSERTION LOSS (dB)
0
-0.2
-0.4
-0.6
-0.8
-1.0
1 62 4 53
Figure 19. Insertion Loss of HMPP-389T at
-20V.
FREQUENCY (GHz)
INSERTION LOSS (dB)
1 62 4 53
0
-0.2
-0.4
-0.6
-0.8
-1.0
Figure 20. Isolation at Different Frequencies
with Forward Current as a Parameter.
FREQUENCY (GHz)
ISOLATION (dB)
-10
-14
-18
-22
-26
-30
1 62
0.15 mA
0.25 mA
0.5 mA
1 mA
1.5 mA
20 mA
4 53
Figure 18. Return loss of HMPP-389T mounted on test line at 0V and -20V
bias.
Normalization was used to remove the pcb’s and connec-
tors’ losses from the measurement of the shunt switch’s
loss. The active trace was divided by the memorized
trace (Data/Memory) to produce the normalized data.
At zero bias, the insertion loss was under 0.6 dB up to 6
GHz (Figure 23). Applying a reverse bias to the PIN diode
has the eect of reducing its parasitic capacitance. With a
reverse bias of -20V, the insertion loss improved to better
than 0.5 dB (Figure 24).
Figure 18. Insertion loss of HMPP-389T at 0V.
Figure 20. Isolation at dierent frequencies with forward current as a
parameter.
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 frequency range.
Figure 16. Insertion Loss of Reference
Line.
FREQUENCY (GHz)
INSERTION LOSS (dB)
0
-0.2
-0.4
-0.6
-0.8
-1.0
1 62 4 53
Figure 16. Insertion loss of reference line.
Insertion loss of the reference was very low and generally,
increased with frequency (Figure 21). If the demo-board
has been constructed carefully, there should not be any
evidence of resonance. The reference line’s insertion loss
trace can be stored in the VNA’s display memory and
used to correct for the insertion loss of the test line in the
subsequent measurements.
9
Assembly Information
The MiniPak diode is mounted to the PCB or microstrip
board using the pad pattern shown in Figure 26.
SMT Assembly
Reliable assembly of surface mount components is a com-
plex process that involves many material, process, and
equipment factors, including: method of heating (e.g., IR
or vapor phase reow, wave soldering, etc.) circuit board
material, conductor thickness and pattern, type of solder
alloy, and the thermal conductivity and thermal mass of
components. Components with a low mass, such as the
MiniPak package, will reach solder reow temperatures
faster than those with a greater mass.
After ramping up from room temperature, the circuit
board with components attached to it (held in place with
solder paste) passes through one or more preheat zones.
The preheat zones increase the temperature of the board
and components to prevent thermal shock and begin
evaporating solvents from the solder paste. The reow
zone briey elevates the temperature suciently to pro-
duce a reow of the solder.
The rates of change of temperature for the ramp-up and
cool-down zones are chosen to be low enough to not
cause deformation of the board or damage to compo-
nents due to thermal shock. The maximum temperature
in the reow zone (T
MAX
) should not exceed 260°C.
These parameters are typical for a surface mount assembly
process for Avago diodes. As a general guideline, the
circuit board and components should be exposed only
to the minimum temperatures and times necessary to
achieve a uniform reow of solder.
0.4 0.4
0.3
0.5
0.3
0.5
2.60
0.40
0.20
0.40 mm via hole
(4 places)
0.8
2.40
Figure 21. PCB Pad Layout, MiniPak (dimensions in mm).
This mounting pad pattern is satisfactory for most
applications. However, there are applications where a
high degree of isolation is required between one diode
and the other is required. For such applications, the
mounting pad pattern of Figure 27 is recommended.
Figure 22. PCB Pad Layout, High Isolation MiniPak (dimensions in mm).
This pattern uses four via holes, connecting the crossed
ground strip pattern to the ground plane of the board.
P1-P3P4-P6P7-P9P10-P12

HMPP-3890-TR2

Mfr. #:
Buy HMPP-3890-TR2
Manufacturer:
Broadcom / Avago
Description:
PIN Diodes 50 VBR 0.3 pF
Lifecycle:
New from this manufacturer.
Delivery:
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