General Information
The Keysight Technologies, Inc. 33330B/C Series of broadband coaxial detectors are specifically
designed for use in microwave instrumentation and systems applications such as the detecting
element in leveling loops, power monitoring, and as wideband video detectors.
These detectors utilize a Low Barrier Schottky (LBS) diode that requires no bias, has exceptional
broadband flatness and low SWR, and is environmentally rugged. For measurement accessory
applications, Keysight offers similar RF performance with a variety of input and output connectors
in the Model 423B, 8470B, and 8472B Series.
The Low Barrier Schottky diode detector
The 33330B/C detectors consist of a Low Barrier Schottky (LBS) diode and a miniature thin film
circuit that matches the diode to a 50-ohm transmission line. The diode is a specially fabricated
Schottky diode using metalization designed to achieve low origin resistance, thus eliminating the
need for bias. In addition to superior RF characteristics, the LBS detector offers significant advantages
over other types of detectors. For example, a typical Schottky requires bias for proper operation; a
tunnel diode detector has a limited power range because of its negative resistance region; and the
point contact diode, because of its fragile construction, is unsuitable for many field applications.
Frequency Range
–
–
–
–
–
–
–
Broadband (0.01 to 26.5 GHz)
Excellent flatness (±0.6 dB to 18 GHz)
Low SWR (<1.5 to 18 GHz)
Environmentally rugged (MIL-STD 883 tests)
Field replaceable diode modules
APC 3.5-mm connector (reliable, SMA compatible)
Low Barrier Schottky diode (no bias required)
Since only metallurgical bonds are
used with the diode, the detectors
are extremely rugged. As noted on
page 4, the detectors have undergone
extensive environmental testing
to MIL-STD 883 procedures, an
important factor in military systems
applications. The detector can also
withstand high RF power levels for
short durations without burnout,
important for power monitoring appli-
cations. For example, it can typically
withstand 1 watt CW for a minute
without permanent damage.
The equivalent circuit and pulse
response equations for the 33330B/C
detectors are shown in Figures 1
and 2, and extensive data on the
performance of the detectors is given
on page 3. Using this information, the
user can select a load to extend the
square law region to higher power
levels or to minimize the output varia-
tion over a given temperature range.
Excellent broadband flatness
The thin film input matching circuit
was optimized for flat frequency
response and low SWR, which yields
improved performance in leveling
loops and power monitoring applica-
tions. Use of thin film fabrication
techniques for the circuit and diode
results in excellent unit-to-unit
repeatability of performance, and
thus matched pairs will track within
a few tenths of a dB over the entire
frequency range (see Figure 2). This
feature is especially important in
the 20 to 26.5 GHz frequency range
where diode capacitance causes the
sensitivity to decrease by 3.3 dB, yet
this “roll off” characteristic is very
repeatable and matched pairs will
track within ±0.5 dB.
minimizes reflections that cause
frequency response ripple and power
measurement inaccuracies. Such
errors can be significant. For example,
using a detector with an SWR of 2.5:1
in an application with a 2:1 source
match can result in more than a
±1.3 dB ripple. For the same source
match of 2:1, a typical 33330B detec-
tor with SWR less than 1.25 would
have less than ±0.4 dB ripple.
APC 3.5-mm connector
improves performance and
extends frequency range
The Keysight 33330B/C detectors
use the APC-3.5 connector, which is
compatible with the industry standard
SMA but is more rugged and offers
improved repeatability over hundreds
of connections. Use of this connector
extends the frequency range of the
33330C to 26.5 GHz.
Low SWR
The miniature thin film circuit used
provides an excellent 50-ohm match
to the transmission line, which
Equivalent Diode
R
V
, Diode
Video
Impedance
Video
Ringing
Suppressor
(50 )
RF
In
50
V
Video
C
B
, RF Bypass
Out
Capacitor
Typical Values:
R
V
(Diode Video Impedance) ~ 1.3 k *
=
C
B
(RF Bypass Capacitor) ~ 30 pF nominal
=
(R
LOAD
)(R
V
)
T
R
(10 to 90% Risetime) ~ 2.2 ––––––––– (C
B
+ C
LOAD
)
=
R
LOAD
+ R
V
*
@ 25 °C and P
IN
< –20 dBm (see Figure 7)
Figure 1. Equivalent circuit for the Keysight 33330B/C detectors
with typical parameter values
Figure 2. Typical frequency response of the
Keysight 33330B/C detectors
3
Specifications
1
33330B
Frequency range
2
Frequency response
Octave band flatness
Broadband flatness
±0.2 dB over any octave to 8 GHz
0.01 to 12.4 GHz: ±0.3 dB
0.01 to 18 GHz: ±0.6 dB
0.01 to 4 GHz: 1.2
0.01 to 18 GHz: 1.5
> 0.5 mV/μW
200 mW
1 watt (typical)
< 50 μV
±0.2 dB over any octave to 8 GHz
0.01 to 12.4 GHz: ±0.3 dB
0.01 to 20 GHz: ±0.6 dB
20 to 26.5 GHz: ±1.5 dB from a –3.3 dB linear slope
0.01 to 4 GHz: 1.2
4 to 18 GHz: 1.5
18 to 26.5 GHz: 2.2
0.01 to 18 GHz: > 0.5 mV/μW
18 to 26.5 GHz: > 0.18 mV/μW
200 mW
1 watt (typical)
< 50 μV
0.01 to 18 GHz
33330C
0.01 to 26.5 GHz
SWR
Low level sensitivity
Maximum operating input
Typical short-term maximum input
(less than 1 minute)
Noise (μV peak to peak with
CW power applied to produce
100 mV output, 400 kHz BW)
Output polarity
Matched response
3
Negative (default Option 301), Positive (Option 003)
0.01 to 12.4 GHz: ±0.2 dB
0.01 to 18 GHz: ±0.3 dB
0.01 to 12.4 GHz: ±0.2 dB
0.01 to 18 GHz: ±0.3 dB
0.01 to 26.5 GHz: ±0.5 dB
Option 003
Environmental capabilities
4
Operating temperatures
5
Temperature cycling
Vibration
Shock
Acceleration
Altitude
6
Salt atmosphere
7
Moisture resistance
With epoxy coating
7
Without coating
1. Measured at 25 °C and < –20 dBm unless otherwise specified.
2. Below 1 GHz RF may leak through the video connector. If objectionable, this may be eliminated with a low pass filter.
3. Option 001 must be ordered for each matched pair. Default option is Option 101, no matched pair.
4. Additional information available upon request.
5. Typical variations with temperature are shown on page 3.
6. Tested only to 50,000 ft (15,240 m), capable of much higher performance.
7. Use of an epoxy coating is required for meeting these requirements. Contact your Keysight Components Field Engineer for details.
MIL-STD 883. Method 1004.1: (25 to 65 °C, 95% RH)
25 to 40 °C, 95% RH
–65 to 100 °C
MIL-STD 883. Method 1010.1: (–65 to ±100 °C)
MIL-STD 883. Method 2007 0.6’’ D.A. (20 to 80 Hz) and 20 G (80 to 2000 Hz)
MIL-STD 883. Method 2002.1 (500 G. 0.5 ma)
MIL-STD 883. Method 2001 (5000 G)
MIL-STD 883. Method 1001: (50,000 ft. 15,240 m)
MIL-STD 883. Method l009.1: (48 hr. 5% solution)
5
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