4
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Features
Low Loss
4 kW Coarse Limiters
200 Watt Midrange Limiters
10 mW Clean–Up Limiters
Description
Alpha has pioneered the microwave limiter diode.
Because all phases of manufacturing, from design
through epitaxy to the finished device, are specifically
tailored to this application, Alpha limiters have lower
loss, greater bandwidth and faster turn–on time than
equivalent competitive diodes.
Alpha’s series of thin base limiter diodes will provide
passive receiver protection over the entire range of
frequencies from 100 MHz to beyond 30 GHz.
These diodes are PIN silicon devices with a thin intrinsic
region, typically 2 microns for the CLA4603 and 4601,
4 microns for the CLA4606, 4604, and 4605, and 15
microns for the CLA4607 and 4608 series. They
operate as a power dependent variable resistance,
through mechanisms of charge injection and storage,
similar to rectification, when used in microwave circuitry
as shown in Figure 1. The different “I” region thicknesses
and capacitances provide variable threshold and
leakage power levels and power handling capability. The
CLA4607 and 4608, which can handle incident pulses of
up to 4 kW for 1 ms, are used as “coarse” prelimiters,
with the thinner diodes used as clean–up or “fine” limiters
to reduce the leakage power to as low as 10 mW for
protecting the most sensitive receivers.
210 240
Chip Dimensions
Model
Nb
DOT Diameter (Typ.) Chip
St l
Number Inches mm Style
CLA4601–000
CLA4602–000 0.0012
0.0015 0.02
0.04 150–806
150–806
CLA4603–000 0.0015 0.04 149–801
CLA4604–000
CLA4605–000
0.0015
0.0025
0.04
0.06
150–806
150–801
CLA4606–000 0.002 0.05 149–801
CLA4607–000
CLA4608–000 0.003
0.005 0.75
0.12 149–801
149–801
Limiter Diodes
CLA Series
4–12 Alpha Industries
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RF
Ground
Return
< 1Ω
CLA4607 CLA4606 CLA4603
Receiver
Figure 1. Cascaded Limiter Design
RF
CLA4607
Receiver
RR
Schottky Barrier
CMB7602
Figure 2. Quasi–Active Limiter
The CLA4603 and 4606 limiter diodes are
constructed in a passivated flat–chip configuration
and are available in a basic chip form or encapsulated
in a variety of Alpha glass or ceramic packages, a few
of which are shown.
Limiter diodes with lower capacitance values, to
0.08 pF, constructed with a passivated mesa
configuration, are available in the CLA4601 and 4605
series. The mesa devices offer low CJ, and therefore
broader bandwidth, lower loss, and faster response,
at reduced power . These diodes are also available in
chip package form, and represent the ultimate in
limiter performance, not approached by other
manufacturers. The CLA4607 diodes (highest
power) are available in both planar and mesa
construction.
Figures 3 and 4 illustrate the fundamental structures
of diodes mounted in a 50 ohm microstrip circuit. The
diode characteristics listed in the table refer to chips
mounted in such a circuit. The designer can use these
parameters in modeling the chip in any package,
provided overall package parasitics are considered.
Additional bonding and handling methods are
contained in Alpha application notes.
ÇÇÇÇÇÇÇÇÇÇÇÇÇ
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É
É
É
É
ÉÉ
ÉÉ
ÉÉ
É
É
É
ÉÉÉ
ÉÉÉ
É
É
É
ÉÉÉ
ÉÉÉ
É
É
É
ÉÉÉ
ÉÉÉ
ÉÉ
ÉÉ
ÉÉ
ÉÉ
É
É
ÉÉ
Ground
Plane Solder or
Epoxy Die Bond Microstrip Board
TFG 0.006” Thick Typ.
0.020”
Typ.
0.001” Gold Wire
Bond T yp.
50
Oh
m
Connector
Figure 3. Side View
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
Diode T yp. TFG Board
50 Ohm
Conductor
0.022” T yp
Ground
Return
12
Figure 4. Top View
CJRRCJRP
1
CJRP
2
50Ω50Ω
Coil for Ground Return
Figure 5. Low Level Equivalent Circuit
Limiter Diodes
CLA Series
4
4–13
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Basic Application
When designing microstrip limiters the bonding wire
length and diameter, in conjunction with the chip
capacitance, form a low pass filter (see Figure 7).
Line lengths of (L1, and L2) are varied to provide
broadband matching and flat leakage characteristics.
Typically, L1 and L2 are on the order of 0.1
wavelength. In Figure 1, the CLA4607 chip provides
about 20 dB attenuation, reducing a 1 kW input to 10
watts. The CLA4606 reduces this to 100 mW and the
CLA4603 to about 20 mW.
During the rise time of the incident pulse, the diodes
behave in the following manner. The CLA4603, due
to its thin “I” region, is the first to change to a low
impedance. Experiments indicate that the CLA4603
reaches the 10 dB isolation point in about 1 ns and
20 dB in 1.5 ns with an incident power of 10 watts.
The CLA4606 takes about 4 ns and the CLA4607
about 50 ns. Consequently, the CLA4603 provides
protection during the initial stages of pulse rise time,
with the thicker diodes progressively “turning on” as
the power increases. With proper spacing (L1 and L2),
the “on” diodes reflect high impedances to the
upstream diodes, reducing the turn–on time for those
diodes and ensuring that essentially all of the incident
power is reflected by the input diode, preventing
burnout of the thinner diodes. At the end of the pulse
the process reverses, and the diodes “recover” to the
high impedance state; the free charge which was
injected in the “I” region by the incident power leaks
off through the ground return and additionally is
reduced by internal combination. With a ground
return, recovery time is on the order of 50 ns. With a
high impedance return, for example the circuit of
Figure 2, the Schottky diodes recovers or 1 “opens”
in practically zero time, and internal recombination,
on the order of several diode lifetimes, is the only
available mechanism for recovery. This recovery time
can be long–on the order of 1 µS for the CLA4607
series. The shunt resistor Rr minimizes the problem.
One hundred ohms will approximately double the
recovery time, compared to a short circuit.
When the Schottky diode is directly coupled to the
transmission line, in cascade after the coarse limiter,
the leakage power will be less than if a zero ohm
ground return were used. If the Schottky is decoupled
too much, the leakage power increases, owing to the
high DC impedance of a Schottky. Similarly, a 3.0 ohm
ground return causes an increase of about 3 dB in
leakage power compared to a zero ohm return.
RS
12
50Ω50Ω
Coil for Ground Return
RSRS
Figure 6. High Power Equivalent Circuit
2 4 6 8 1012141618
1.75
1.50
1.25
1.0
Frequency (GHz)
VSWR
0.50 pF
0.30 pF
0.15 pF
50Ω
Bonding Wires
50Ω
Diode
Chip
single Section
Low Pass Filter
50Ω
Bonding Wires
50Ω
Diode
Chip
Single Section
Low Pass Filter
Figure 7. Typical VSWR for Low Pass Filters
2 4 6 8 1012141618
0.4
0.3
0.2
0.1
Frequency (GHz)
Insertion Loss (dB)
0.5
50Ω
Bonding Wires
50Ω
Single Diode Section
CJRP
Diode Chip
0.50 pF
0.30 pF
0.15 pF
Figure 8. Typical Diode Insertion
Loss vs. Frequency
Limiter Diodes
CLA Series
4–14 Alpha Industries
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105104102CW
1.0
10.0
100.0
Pulse Length (Sec)
Peak Normalized to Tabulated Value at 1.0 µS(°C/W)
°C/W
CLA4607,
08 Series
°C/W
CLA4601, 02, 03, 04,
05, 06 Series
Figure 9. Pulsed Thermal Impedance
0 +10 +20 +30 +40 +50 +60 +66
0
+10
+20
+30
+40
+50
Peak Pout Input (dBm)
Peak Power Output (dBm)
CLA4603
CLA4606
CLA4607
CLA4604
CLA4601
50Ω50Ω
Diode
Chip
Figure 10. Typical Peak Leakage
Power at 1 GHz
2 4 6 8 1012141618
+9
+6
+3
0
Frequency (GHz)
Leakage Power Above 1.0 GHz (dB)
50Ω50Ω
Diode
Chip
Figure 11. Leakage Power vs. Frequency
0.25
0.50
0.75
1.0
Power Derating Factor
–50°C0°C +50°C +100°C +150°C
Case Temperature (°C)
Figure 12. Power Handling Capability
vs. Temperature
Ordering Information
The table on the following page shows the part
numbers for chip limiter diodes.
Packaged limiter diodes may be specified by adding
the package number to the chip number. For
example, CLA4605– 210 is the CLA4605– 000 in the
210 package.
210 240
The recommended packages for limiter diodes are
shown on page 6–11.
Available through distribution:
CLA4603–210
CLA4606–210
CLA4607–210
CLA4603–240
CLA4606–240
CLA4607–240
Limiter Diodes
CLA Series
4
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Electrical Specifications at 25
°
C
Part
Number
VB
(V)
CJ
@ 0V
(pF)
CJ
@ 6V
(pF) RS Typical1RP2
(Ω)ΘP3
(°C/W) ΘCW
(°C/W)
TL
(ns)
Typ. Typ. Max. @10 mA (Ω)@1.0 mA (Ω) Typ. Typ.
( )
Typ.
CLA4601–000
CLA4602–000 15–30 0.12
0.20 0.10
0.15 2.0
1.5 4.0
3.0 3000
2000 15
10 120
80 5
5
CLA4603–000 20–45 0.20 0.15 1.5 5.0 2000 10 100 5
CLA4604–000
CLA4605–000 30–60 0.12
0.20 0.10
0.15 2.0
1.5 4.0
4.0 3000
2000 10
7100
70 7
7
CLA4606–000 45–75 0.20 0.15 1.5 4.0 2000 7 80 10
CLA4607–000
CLA4608–000
120–180
120–180
0.20
0.80
0.15
@ 50V
0.50
@ 50V
1.5
0.5
3.5
3.0
2000
1000
1.2
0.3
40
15
50
100
Available through distribution.
Typical Performance
Part
Number
Peak Pin
(1.0 µS)
(dBm)
Threshold4
(dBm)
Leakage4
POUT
(dBm)
Insertion Loss2
(dBm) CW5 Power In
(W)
Recovery6
Time,
(ns)
Max. Typ. Typ. Typ. Max. Typ.
CLA4601–000
CLA4602–000 +47
+50 +7
+7 +21
+24 0.1
0.1 2
35
5
CLA4603–000 +50 +10 +22 0.1 2 10
CLA4604–000
CLA4605–000 +47
+50 +12
+12 +24
+27 0.1
0.1 3
410
10
CLA4606–000 +53 +15 +27 0.1 3 20
CLA4607–000
CLA4608–000 +60
+66 +20
+20 +39
+44 0.1
0.2 6
15 50
100
1. Series resistance is measured at 100 MHz.
2. Chip loss can be represented as a resistance in shunt with the junction capacitance. RP is measured at 3 GHz, zero bias. Figure 9 indicates typical variation with frequency . Loss data
shown are for 10 GHz for 0.15 and 0.30 pF chips, 5 GHz for 0.50 pF chips. Reflective loss is shown in Figure 8 and is included. Loss is measured at –10 dBm input.
3. Pulsed thermal impedance is given for a 1 µS pulse. Figure 10 shows typical variation for longer pulse lengths. CW thermal impedance presumes infinite heat sink.
4. Threshold input power produces 1 dB increase in insertion loss. Figure 1 1 shows typical leakage power curves. Data taken for 1.0 GHz. Figure 12 shows typical variation with frequency .
Note especially the roll–off of CLA4607 at higher frequency.
5. Note that CW power and average power are not synonymous. Power ratings are computed in terms of a peak junction temperature of 200°C, for short pulses, an average junction
temperature of 125°C, and an ambient of 25°C. Duty factor 0.001 assumed for maximum pulse power input. Figure 13 shows power derating with temperature.
6. Recovery time is measured with ground return (less than 1.0 ohm) to 1 dB excess loss, at 1 GHz.
Outline Dimensions
METALIZED
SILICON
GOLD DOT
150–801 .002 (min) .010 .014
Chip
Style Bonding Pad
Nominal (In.) Min. Max.
Chip Size (In.)
MET ALIZED BACK
CONT ACT GOLD
149–801 150 Series
150–806 .010 .014.0011 (min)
.004 – .006
Limiter Diodes
CLA Series
