ElecEng 4/6FJ4 LABORATORY
MODULE #3
Microwave Detection with a Crystal Detector
I. Objectives
The purpose of this module is to help the students get familiar with the “crystal” detector, one of
the simplest power detectors at radio, microwave and millimeter-wave frequencies. The crystal
detector uses a simple circuit, consisting of a diode, a RF (radio-frequency) choke and a low-pass
filter (often, this is simply a capacitor) to rectify the high-frequency signal.
The lectures of ElecEng 4FJ4 do not cover the general topic of microwave diodes and their
applications. Thus, this laboratory module is complementary to the lectures in both its content
and hands-on experience.
The students must prepare for the 3-hour laboratory beforehand by reading the DISCUSION part
of the Detection of Microwave Signals LabVolt (https://www.labvolt.com/) exercise, which
constitutes MODULE #3. If the students come to the lab unprepared, it is likely that they will not
be able to complete the exercises on time.
II. Preparing the Lab Report
The student is expected to bring along a printout of this guide. The Lab Report consists of simply
filling in the required information. Note that there are REVIEW QUESTIONS at the end of the
exercise. The student must provide answers to these questions, which are closely related to the
DISCUSSION and the PROCEDURE parts of the exercise.
The student is expected to hand in the lab report to the teaching assistant (TA) at the end of the
lab session. Take home work should not be necessary.
PLEASE WRITE DOWN YOUR NAME AND STUDENT ID ON THE TITLE PAGE!
III. Grading the Lab Report
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Total points: 100
Penalty for a missing item in the PROCEDURE part: −5 points
Penalty for a missing plot or table in the PROCEDURE part: −10 points
Penalty for a missing or wrong answer in the REVIEW QUESTIONS part: −10 points
IV. Feedback
We value your opinion. Direct your recommendations, opinions, and criticism to the Instructor
(Prof. Nikolova) at nikolova@ieee.org.
Nikolova
ElecEng 4FJ4 Labs
2014
ElecEng 4/6FJ4 LABORATORY
MODULE #3
MICROWAVE DETECTION WITH A CRYSTAL DETECTOR
Student Name:
Student ID:
Student Signature:
Date:
TA Name:
TA Signature:
Date:
REPORT GRADE:
(provided no later than one week after report submission)
Nikolova
ElecEng 4FJ4 Labs
2014
Exercise
5
Detection of Microwave Signals
EXERCISE OBJECTIVES
When you have completed this exercise, you will be familiar with the operation of a
crystal detector operating in the square-law region. You will be able to plot the
sensitivity curve of a crystal detector and to evaluate its tangential sensitivity.
DISCUSSION
Introduction to Crystal Detectors
Nikolova: The name "crystal" is
an archaic reference to the first
nonlinear devices acting as
diodes in the now obsolete
battery-less "crystal" radios.
Mineral crystals (small pebbles)
from lead sulphide (PbS) were
common. Nowadays, tunnel
diodes are usually used.
Microwave signals are detected by converting the microwave signal to a DC current
or DC voltage whose amplitude is a function of the amplitude of the microwave
signal. By doing so, conventional low-frequency instruments can be used to measure
many of the parameters of the microwave signal, or just to detect its presence.
Figure 5-1 represents a simplified microwave crystal detector circuit and its symbolic
representation. Crystal detectors are basically a type of diode rectifier. Because a
diode is a non-linear element, harmonic components of the input signal are
generated in the detection process. These harmonic components are attenuated by
the lowpass filter located before the detector output, leaving only the DC output
signal.
Figure 5-1. Simplified representation of a detection circuit and the symbolic representation of a
crystal detector.
Typical Sensitivity Curve of a Crystal Detector
Figure 5-2 shows how the output voltage of a detector varies as a function of the
microwave signal power at its input. This curve represents a typical sensitivity
curve for crystal detectors.
•
When the microwave signal power remains low, the detector output voltage is
proportional to the square of the microwave signal voltage and, therefore, to the
microwave signal power. In this condition, the detector is said to be operating in
its square-law, or quadratic region.
5-1
Detection of Microwave Signals
•
When the microwave signal power is higher than about -15 dBm, the detector
output voltage tends to be directly proportional to the microwave signal voltage.
In this condition, the detector is said to be operating in its linear region; that is,
it rectifies the applied signal.
Figure 5-2. Typical output voltage-versus-microwave input power curve of a crystal detector.
Voltage Sensitivity
The voltage sensitivity is an indication of a detector output voltage in the square-law
region when a microwave signal of a given power is applied to its input.
The voltage sensitivity can be calculated by using the equation below.
The voltage sensitivity is an approximation. Its main use is to compare the
performance of different detectors.
Amplification of a Crystal Detector's Output Signal
As Figure 5-3 shows, a crystal detector can be used to detect very small signals
when followed by a low-noise high-gain amplifier. The output level, amplified to a
level high enough to be easily measured, is then applied to an indicator.
5-2
Detection of Microwave Signals
Figure 5-3. Amplification of a crystal detector's output signal.
This method can be used for non-modulated and amplitude-modulated microwave
signals. Usually, the microwave signal is amplitude modulated by a 1-kHz square
wave signal. This permits the use of low-frequency instruments and circuits with low
noise level to measure several parameters of the microwave signal, and the
detection of even smaller signals.
Measuring the Tangential Sensitivity
The tangential sensitivity of a detector is a measure of the detector's ability to detect
low-level signals. It corresponds to the smallest microwave signal level that can be
detected above the noise level.
One way to measure the tangential sensitivity of a detector is to apply a microwave
signal amplitude modulated by a 1-kHz square-wave signal to the detector input:
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The level of the microwave signal is adjusted so that the peak-to-peak voltage of
the 1-kHz detected signal is equal to the peak-to-peak voltage of the noise at the
detector output, as Figure 5-4 shows.
•
The applied microwave signal power corresponds to the tangential sensitivity of
the crystal detector, as long as the percentage of modulation is 100%.
For the measurement setup, an oscilloscope, and an amplifier with a bandwidth wide
enough to prevent distortion of the shape of the 1-kHz square-wave signal are
required.
5-3
Detection of Microwave Signals
Figure 5-4. Oscilloscope screen showing a 1-kHz detected signal for tangential sensitivity
measurements.
Generally, crystal detectors will have a tangential sensitivity in the order of -50 dBm
for a bandwidth of 1 MHz. Since the noise power at the amplifier output is
proportional to the bandwidth of the amplifier, the tangential sensitivity is better when
the bandwidth is reduced.
Procedure Summary
In this exercise, you will measure the power of a microwave signal, using the
Thermistor Mount and the LVDAM-MW Power Meter. This will be the maximum
power used in the exercise, and will be the reference power level.
You will then replace the Thermistor Mount by a Crystal Detector and measure the
detector output voltage with the LVDAM-MW Oscilloscope. You will then attenuate
the microwave signal by steps and measure the Crystal Detector output voltage for
each attenuation setting. This will allow you to plot the sensitivity curve of the Crystal
Detector.
Finally, you will amplitude modulate the Gunn Oscillator's output signal with a 1-kHz
square wave and measure the tangential sensitivity of the Crystal Detector.
EQUIPMENT REQUIRED
Refer to the Equipment Utilization Chart, in Appendix F of this manual, to obtain the
list of equipment required to perform this exercise.
5-4
Detection of Microwave Signals
PROCEDURE
Nikolova: Please place a "tick" mark in the box of each step of the Procedure once this step is completed.
A missing "tick" mark indicates missed Procedure item, which can result in a penalty of -5 or -10 points.
Measuring the Maximum Power of the Microwave Signal
G
1. Make sure that all power switches are in the O (off) position. Set up the
modules and assemble the microwave components as shown in Figure 5-5.
Note: Before connecting the Thermistor Mount, unscrew the
matching screws so that they do not penetrate into the
waveguide; the screws do not need to be removed from the
posts.
G
2. Make the following settings on the Gunn Oscillator Power Supply:
VOLTAGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MIN.
MODE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . DC
METER SCALE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 V
G
3. Turn on the Gunn Oscillator Power Supply and the Data Acquisition
Interface (DAI) by setting their POWER switch to the "I" (ON) position.
Set the Gunn Oscillator supply voltage to 8.5 V. Wait for about 5 minutes to
allow the modules to warm up.
G
4. On the host computer, start the LVDAM-MW software. In the Application
Selection window, make sure the Work in stand-alone box is unchecked,
and click OK.
In the Settings panel of LVDAM-MW, make the following settings:
Gunn Oscillator/VCO Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ON
Function Input 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Power Meter
Gain Input 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 dB
5-5
Detection of Microwave Signals
Figure 5-5. Computer and module arrangement (showing electrical connections to microwave
components), and microwave setup.
G
5-6
5. Wait for about 5 minutes to allow the modules to warm up. In LVDAM-MW,
start the Power Meter and set it to display dBm readings. Enter the power
Detection of Microwave Signals
factor indicated (η) on the Thermistor Mount’s waveguide. Then, perform
zeroing of the Power Meter.
G
6. On the Thermistor Mount, loosen the knurled lock-nut that holds the
moveable short circuit into place. Adjust the short circuit to the position
nearest the waveguide which gives a maximum reading on the Power
Meter. Then, adjust each matching screw of the Thermistor Mount to
maximize the power reading. Fine tune if necessary. Finally, lock the
moveable short circuit into position.
G
7. Note and record the reading of the Power Meter. This will be, in the context
of this exercise, the maximum power of the microwave signal.
Maximum power of the microwave signal =
dBm
Close the Power Meter of LVDAM-MW.
Determining the Sensitivity Curve of the Crystal Detector
Note: A first microwave circuit [Figure 5-6 (b)] will be used to
perform the measurements requiring an attenuation lower than
30 dB. A 30-dB Fixed Attenuator will then be added to the
microwave circuit to perform the rest of the
measurements—which require an attenuation equal to or higher
than 30 dB.
G
See Note on p. 5-9 before
item 10.
8. In the Settings panel of LVDAM-MW, set the field Gunn Oscillator/VCO
Power to OFF.
Set up the modules and assemble the microwave components as shown in
Figure 5-6.
Connect the Crystal Detector to MULTI-FUNCTION INPUT 1 of the Data
Acquisition Interface.
Note: Connecting the output of the Crystal Detector to one of the
DAI Inputs (in this case MULTI-FUNCTION INPUT 1) will allow
you to monitor the Crystal Detector output voltage with the
Oscilloscope of LVDAM-MW.
G
9. Set the blade of the Variable Attenuator to 0.0 mm.
5-7
Detection of Microwave Signals
Figure 5-6 Computer and module arrangement (showing electrical connections to microwave
components), and microwave setup for attenuations lower than 30 dB.
5-8
Detection of Microwave Signals
Nikolova: Just connect
the 60-dB Amplifier here.
This way you will need to
insert only one additional
component later.
Note: It is probable that you will not need the 60-dB Amplifier in
this section of the exercise, since the level of the signal produced
at the output of the Crystal Detector is usually strong enough for
the acquisition process to perform the calculations and display the
proper signal on the Oscilloscope. However, if the signal is too
weak, connect the 60-dB Amplifier between the output of the
Crystal Detector and Multi-Function Input 1 of the Data
Acquisition Interface (as shown in Figure 5-9 of this exercise).
G 10. In LVDAM-MW, select the Data Table function, which will bring up the Data
Table. In this Table, manually enter the column titles and figures already
recorded in Table 5-1 below. Save the Data Table.
Nikolova: You can fill in this table by hand directly in your Report printout. Using the
software to generate the Table is optional.
ATTENUATION
SETTING (dB)
0
ATTENUATOR
BLADE'S
POSITION (mm)
DELIVERED
POWER (dBm)
DETECTOR
VOLTAGE (V)
20 log
DETECTOR
VOLTAGE (dB)
0
5
10
15
20
25
30
0
35
40
Table 5-1. Determining the sensitivity curve for the Crystal Detector.
G 11. Fill in the column "ATTENUATOR BLADE'S POSITION" of the Data Table:
Nikolova: A plot of the blade-position
vs. attenuation curve of the attenuator
is provided at your table. We have two
such attenuators and their curves are
also provided at the back of this
guide.
By referring to the attenuation-versus-blade position curve (or the
corresponding Data Table) of the Variable Attenuator obtained in
Exercise 4, determine as precisely as you can the attenuator blade's
position required to obtain each of the attenuation settings listed in the Data
Table. Record your results in the table and save your work.
Note: For the attenuation settings equal to or higher than 30 dB,
subtract 30 dB from the attenuation setting and determine the
Variable Attenuator's blade position required to obtain the
resulting difference.
For example, an attenuation setting of 30 dB requires that the
Variable Attenuator's blade position be returned to 0 mm; an
attenuation setting of 35 dB requires that the blade position be set
to provide a 5-dB attenuation, and so on.
This must be done because, as already mentioned, a 30-dB Fixed
Attenuator will be added to the current microwave circuit when the
required attenuation is equal to or higher than 30 dB.
5-9
Detection of Microwave Signals
G 12. Fill in the column "DELIVERED POWER" of the Data Table. For each
attenuation setting, calculate and record the power delivered to the Crystal
Detector, using the formula below. Save your work.
where
Maximum Power = Maximum power of the microwave signal,
as recorded in step 7 of this exercise
G 13. In the Settings panel of LVDAM-MW, make the following settings:
Gunn Oscillator/VCO Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ON
Function Input 1 . . . . . . . . . . . . . . . . . . . . . Voltage Probe (Unipolar)
Gain Input 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 dB
Start the LVDAM-MW Oscilloscope and set it as follows:
Channel 1 (X)
Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500 mV/DIV
Time base . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200 µs/DIV
Trigger Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ch1 Software
Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Continuous Refresh
G 14. Fill in the column "DETECTOR VOLTAGE" for each of the attenuation
settings between 0 and 25 dB listed in the Data Table. To do this, perform
the steps below.
a. Adjust the Variable Attenuator's blade to the position required to obtain
the attenuation setting.
b. Measure the voltage on channel 1 of the Oscilloscope screen and
record it in the column "DETECTOR VOLTAGE".
It will be necessary to increase the sensitivity of Oscilloscope Channel 1
when the vertical deflection becomes too low. This is performed by
changing the Scale of Channel 1, and by increasing Gain Input 1 as
necessary.
Note: Changing the Gain on the Input associated with an
Oscilloscope channel will change the scales available on this
channel:
– An Input Gain of 0 dB provides the following scales on the
associated Oscilloscope channel: 1 V/div, 500 mV/div, and
200 mV/div.
– An Input Gain of 20 dB provides the following scales on the
associated Oscilloscope channel: 100 mV/div, 50 mV/div,
and 20 mV/div.
5-10
Detection of Microwave Signals
–
An Input Gain of 40 dB provides the following scales on the
associated Oscilloscope channel: 10 mV/div, 5 mV/div, and
2 mV/div.
Note: The dynamic range of measurement, on each scale of the
Oscilloscope, is not the same as with an ordinary oscilloscope. This occurs
because the dynamic range of measurement is limited by the converters
of the Data Acquisition Interface. Therefore, the maximum voltage that you
can measure, on each scale of the Oscilloscope, is as follows:
– With Function Input set to Voltage Probe (Unipolar): Gain of 0 dB: 3 V;
Gain of 20 dB: 300 mV; Gain of 40 dB: 30 mV.
– With Function Input set to Voltage Probe (Bipolar): Gain of 0 dB: ±
1.5 V; Gain of 20 dB: ± 150 mV; Gain of 40 dB: ± 15 mV.
G 15. Fill in the remainder of the column "DETECTOR VOLTAGE" for the
attenuation settings of 30 to 45 dB:
a. In the Settings panel of LVDAM-MW, set the field Gunn Oscillator/VCO
Power to OFF.
b. Insert the 30-dB Fixed Attenuator between the 6-dB Fixed Attenuator
and the Variable Attenuator, as Figure 5-7 shows. Do not modify the
remainder of your setup.
c. In the Settings panel of LVDAM-MW, set the field Gunn Oscillator/VCO
Power to ON.
d. Adjust the Variable Attenuator's blade to the position required to obtain
each of the remaining attenuation settings listed in the Data Table. For
each attenuation setting, measure the voltage on channel 1 of the
Oscilloscope screen and record it in the column "DETECTOR
VOLTAGE".
Note: You may not be able to fill in the last row of the Data Table
due to the very low voltage level measurement required to do so.
Figure 5-7. Microwave setup for attenuations equal to or higher than 30 dB.
5-11
Detection of Microwave Signals
G 16. Fill in the last column, "20 log DETECTOR VOLTAGE (dB)", of the Data
Table. For each attenuation setting, calculate the detector output voltage,
in dB, based on the detector voltage (V) measured for each of these
settings, and record your results. Save your work.
G 17. In LVDAM-MW, select the Graph function of the Data Table and plot the
sensitivity curve of the Crystal Detector by selecting "DELIVERED POWER"
for the X axis and "20 LOG DETECTOR VOLTAGE" for the Y axis.
The obtained curve should resemble that shown in Figure 5-8.
Print your graph. Then, determine the square-law region of the sensitivity
curve by plotting a straight line tangential to this curve.
As Figure 5-8 shows, in the square-law region, a variation of 1 dBm in the
input power to the Crystal Detector produces a variation of approximately
2 dB in the Crystal Detector output voltage.
This occurs because the Crystal Detector output voltage is proportional to
the square of the amplitude of the microwave voltage. Since the X-axis of
the graph in Figure 5-8 indicates the microwave power (power unit in dBm),
and since the Y-axis indicates the detector output voltage (in dB), a
variation of 1 dBm in the microwave power produces a variation of 2 dB in
the detector output voltage; a variation of 4 dBm in the supplied microwave
power produces a variation of 8 dB in the detector output voltage; and so
on.
Note: The lower section of your curve may deviate from the
straight line, due to inaccuracies of measurements at low signalto-noise ratios. However, consider this section as making part of
the square-law region.
Save your work, and then close the Data Table.
Nikolova: You can plot your curve by entering the data from Table 5-1 directly onto Figure 5-8 in
your Report printout. Using the software to generate your plot is optional.
5-12
Detection of Microwave Signals
Figure 5-8. Sensitivity curve of the Crystal Detector.
Measuring the Tangential Sensitivity of the Crystal Detector
G 18. In the Settings panel of LVDAM-MW, set the Gunn Oscillator/VCO Power
to OFF, so that there is no microwave signal injected into the waveguide.
G 19. As Figure 5-9 shows, modify your circuit so as to connect the Crystal
Detector to MULTI-FUNCTION INPUT 1 of the Data Acquisition Interface,
via the 60-dB Amplifier, Model 9593. This will allow you to monitor the
amplified Crystal Detector output voltage on the Oscilloscope.
5-13
Detection of Microwave Signals
As Figure 5-9 shows, the supply cable for the 60-dB Amplifier must be
connected to the DB-9 male connector on the bottom of the Data Acquisition
Interface.
Figure 5-9. Computer and module arrangement (showing electrical connections to microwave
components), and microwave setup.
5-14
Detection of Microwave Signals
G 20. Make the following settings:
On the Gunn Oscillator Power Supply:
MODE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 kHz
On the Variable Attenuator:
Blade Position . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 mm
Note: Setting the MODE switch of the Gunn Oscillator Power Supply to
1 kHz will cause the Gunn Oscillator's output signal to be amplitude
modulated by a 1-kHz square wave.
G 21. In the Settings panel of LVDAM-MW, make the following settings:
Gunn Oscillator/VCO Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ON
Filter Input 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . > 30 kHz
Function Input 1 . . . . . . . . . . . . . . . . . . . . . . Voltage Probe (Bipolar)
Gain input 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 dB
Set the LVDAM-MW Oscilloscope as follows:
Channel 1 (X)
Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 mV/DIV
Time base . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500 µs/DIV
Trigger Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ch1 Software
Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Continuous Refresh
G 22. Gradually decrease the attenuation provided the Variable Attenuator (turn
its adjustment screw counterclockwise) until you obtain a waveform similar
to that shown in Figure 5-4 of the DISCUSSION on the oscilloscope screen
(that is, a 1-kHz detected signal having a peak-to-peak amplitude
approximately equal to the peak-to-peak voltage of the noise in this signal.)
Figure 5-10 shows an example of signal obtained on the Oscilloscope.
At that point, the level of the 1-kHz detected signal will be very low. You can
switch the 1-kHz MODE switch of the Gunn Oscillator Power Supply
between the "DC" and "1 kHz" positions to better see and evaluate the level
of the noise signal alone and that of the 1-kHz detected signal to see if they
are approximately equal.
5-15
Detection of Microwave Signals
Figure 5-10. Example of a 1-kHz detected signal on the Oscilloscope.
G 23. Record the position of the Variable Attenuator's blade below.
Variable Attenuator's blade position:
Nikolova: A plot of the bladeposition vs. attenuation curve
of the attenuator is provided
at your table. We have two
such attenuators and their
curves are also provided at
the back of this guide.
mm
Referring to the attenuation-versus-blade position curve (or the
corresponding Data Table) of the Variable Attenuator obtained in
Exercise 4, determine the attenuation provided by the Variable Attenuator
at this blade position.
Attenuation:
dB
Calculate the total attenuation by adding 30 dB to the attenuation obtained
from the Variable Attenuator's curve.
Total attenuation:
dB
Calculate the power of the Crystal Detector's input signal (tangential
sensitivity) by subtracting the total attenuation from the maximum power of
this signal (as recorded in step 7 of this exercise).
Tangential sensitivity:
dBm
G 24. Turn off the Gunn Oscillator Power Supply and the Data Acquisition
Interface by setting their POWER switch to the O (OFF) position.
Disassemble the setup and return all components to their storage location.
G 25. Close the LVDAM-MW software.
5-16
Detection of Microwave Signals
CONCLUSION
In this exercise, you were introduced to the principles of microwave signal detection
and to the operation of crystal detectors.
You plotted the sensitivity curve of the Crystal Detector by measuring its output
voltage for different levels of the microwave signal at its input.
You measured the tangential sensitivity of the Crystal Detector, by amplitude
modulating the Gunn Oscillator's output signal with a 1-kHz square wave.
REVIEW QUESTIONS
1. What do microwave detectors allow you to do?
2. What characterizes the square-law region of a detector?
3. What does the sensitivity curve of a crystal detector represent?
4. A crystal detector generates a signal of 10 mV for an incident microwave power
of -25 dBm. What is the detector sensitivity (in mV/mW)?
5. Why is it often useful to amplitude modulate a microwave signal with a 1-kHz
square wave before applying it to a crystal detector?
5-17
5-18
50
Attenuator #1
45
40
Attenuation (dB)
35
30
25
20
15
10
5
0
0
0.5
1
1.5
2
2.5
3
Blade Position (mm)
3.5
4
4.5
5
50
45
Attenuator #2
40
Attenuation (dB)
35
30
25
20
15
10
5
0
0
0.5
1
1.5
2
2.5
3
Blade Position (mm)
3.5
4
4.5
5