Silicon Beam–Lead
Schottky Barrier Mixer Diodes
DME, DMF and DMJ Series
Features
Ideal for MIC
Low 1/f Noise
Low Intermodulation Distortion
Low Turn On
Hermetically Sealed Packages
SPC Controlled Wafer Fabrication
Description
Alpha beam–lead and chip Schottky barrier mixer
diodes are designed for applications through 40 GHz
in Ka–band. The beam–lead design eliminates the
problem of bonding to the very small junction area
that is characteristic of the low capacitance involved
in microwave devices.
Beam–lead Schottky barrier mixer diodes are made
by the deposition of a suitable barrier metal on an
epitaxial silicon substrate to form the junction. The
process and choice of materials result in low series
resistance along with a narrow spread of capacitance
values for close impedance control.
A variety of forward knees are available, ranging from
a low value for low, or starved, local oscillator drive
levels to a higher value for high drive, low intermode
mixer applications. The beam–lead diodes are
available in a wide range of packages as shown.
Capacitance ranges and series resistances are
comparable with the packaged devices that are
available through K–band. The unmounted diodes
are especially well suited for use in microwave
integrated circuits. The mounted devices can be
easily inserted as hybrid elements in stripline,
microstrip or other such circuitry.
Beam–lead and chip Schottky barrier diodes are
categorized by noise figure for mixer applications in
four frequency ranges: S, X, Ku and Ka–bands.
However, they can also be used as modulators, high
speed switches and low power limiters.
Several types of semiconductor–barrier metal
systems are available, thus allowing proper selection
for optimum mixer design. For most applications the
N–type silicon, low drive types are preferable,
especially for starved LO mixers.
Beam–lead diodes are ideally suited for balanced
mixers, since they exhibit low parasitics and are
extremely uniform. A typical V
F
vs. I
F
curve is shown
in Figure 1. Typical noise figures vs LO drive is shown
in Figure 2 for single N–type, low drive diode types.
Maximum Ratings
Storage Temperature:
Operating Temperature:
Dissipated Power:
Max Current:
–65°C/+175°C
–65°C/+175°C
75 mW/Junction
100 mA
3–12
Alpha Industries
•
[617] 935 5150
•
Fax
[617] 824 4579
•
E-mail
sales@alphaind.com
•
Visit our web site:
www.alphaind.com
Silicon Beam–Lead Schottky Barrier Mixer Diodes
DME, DMF and DMJ Series
NF ZIF
dB
Ω
12.0 700
11.0 600
10.0 500
9.0 400
8.0 300
7.0 200
10.0
5.0
6.0 100
P–Type Zero
Bias
Band
S
C
X
Ku
Frequencies
2 to 4
4 to 8
8.2 to 12.4
12.4 to 18.0
ZIF
CC
mA
6.0
5.0
4.0
NF
3.0
2.0
1.0
0.01
CC
0
0.05 0.1 0.2 0.5 1.0 2.0 5.0 10.0
Forward Current (mA)
2.0
1.0
0.5
0.2
0.1
0.05
0.02
0.01
0.005
0.002
0.001
0
120
240
P–Type Low
Drive (DMB)
N–Type Low
Drive (DMF)
N–Type
Medium Drive
(DME)
Local Oscillator Driver (mW)
3
Figure 3. Typical X–Band Low Drive Mixer
Diode – RF Parameters vs. Local
Oscillator Drive
Single Ended Mixer
SIG Input
Coupler
LO Input
Matching
Network
RF Bypass
IF Output
360
480
600
DC Retrun
Forward Voltage (mV)
Figure 1. Typical Forward DC Characteristics
Curves – Voltage vs. Current
Balanced Mixer
SIG Input
3 dB
Hybrid
Coupler
LO Input
M.N.
M.N.
RF Bypass
IF Output
N–Type HIgh
Driver (DMJ)
1 Junctions
N–Type HIgh
Driver (DMJ)
2 Junctions
N–Type HIgh
Driver (DMJ)
3 Junctions
Double Balanced Mixer
LO Input
SIG Input
10.0
5.0
Forward Current (mA)
2.0
1.0
0.5
0.2
0.1
0.05
0.02
0.01
0.005
0.002
0.001
0
0.480
0.960
1.44
1.92
2.40
IF Output
Figure 4. Typical Mixer Circuits
Ordering Information
Forward Voltage (mV)
Figure 2. Typical Forward DC Characteristic
Curves – Voltage vs. Current
To order a packaged diode, simply append the part
number to the package outline number. For example,
a Medium Drive Ring Quad, Ku band (part number
DME2859–000) in a 234 package would be ordered
as DME2859–234.
Alpha Industries
•
[617] 935 5150
•
Fax
[617] 824 4579
•
E-mail
sales@alphaind.com
•
Visit our web site:
www.alphaind.com
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