Keysight U8903A User manual

Keysight Technologies
U8903A Audio Analyzer
Creating a Custom Filter for the
U8903A Audio Analyzer
Demo Guide

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This demonstration will teach you how to create your own custom lter for the Keysight Technologies, Inc.
U8903A Audio Analyzer by using the MATLAB software on your computer.
Table of Contents
Demonstration Objectives 2
Step 1: Matlab fdatool
(lter design and analysis tool) 3
Step 2: Create Filter 4
Step 3: Export Filter
Coefcient 7
Step 4: Settling Time (Delay) 9
Step 5: Transfer to .juf le 11
S tep 6: Upload .juf le to
U8903A Audio Analyzer 13
Conclusion 14
Ordering Information and
Related Literature 15
Demonstration objectives
Steps to create a custom lter
Follow the steps below to create your own custom lter for the U8903A.
Steps
1. Matlab fdatool (lter design and analysis tool)
2. Create Filter
3. Export Filter Coefcient
4. Settling Time (Delay)
5. Transfer to .juf le
6. Upload .juf le to U8903A Audio Analyzer

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Matlab fdatool (Filter Design and Analysis Tool)
Step 1
Figure 1. MATLAB command window
Figure 2. Filter Design and Analysis Tool
Instructions
1. Start MATLAB program (Figure 1)
2. In the command window, type “fdatool” to start Filter Design and Analysis Tool in MATLAB (Figure 2)

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Create lter
Step 2
Figure 3. “Set quantization parameter” icon
Figure 4. Selecting “Single-precision oating-point” and “Return to the Design Filter page”
Instructions
1. Click on “Set quantization parameter” (Figure 3)
2. Select “Single-precision oating-point” because the architecture of the U8903A is 32 bits (Figure 4)
3. Return to the Design Filter page (Figure 4)

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Instructions
4. Select the “Response Type” e.g. Lowpass, Highpass, Bandpass, and Bandstop (Figure 5)
5. Select the “Design Method” e.g. IIR or FIR (Figure 5)
6. Select the “Frequency Specications” you require e.g. Fpass (1 and 2), Fstop (1 and 2) (Figure 5)
Requirements for Frequency Specications:
– Low Bandwidth = 78125 Hz
– High Bandwidth = 312500 Hz
7. Select the “Magnitude Specications” e.g. Wpass (1 and 2), Wstop (1 and 2) (Figure 5)
8. Press the “Design Filter” button (Figure 5)
Figure 5. Selecting “Response Type”, “Design Method”, “Frequency Specications”, “Magnitude Specication”, and Press “Design Filter” Button

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Instructions
9. The “Order” number (see Figure 6) must be less than 256 in order to meet the architecture of the U8903A Audio Analyzer. Changing
the “Design Method” will change the order number.
Figure 6. Order number must be less than 256

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Export lter coefcient
Figure 7. Exporting Filter Coefcient Information to a le
Instructions
1. Go to “File”, then select “Export...”
2. At “Export To”, select “Coefcient File (ASCII)”
3. Click on “Export” button, and Save to *.fcf le
4. The Filter Coefcient Data File will then be displayed
Export lter coefcient information to a le (gure 7)
Step 3

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Figure 8. Export Filter Coefcient as an object for analysis
Instructions
1. Go to “File”, then select “Export...”
2. At “Export To”, select “Workspace”
3. At “Export As”, select “Object”
4. At “Variable Names”, for “Discrete Filter”, enter “Hd”, then click the “Export” button
5. The Hd object is then in the MATLAB window
Export lter coefcient as an object for analysis (Figure 8)

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Settling time (Delay)
Step 4
Knowing the settling time of your lter
You can know the settling time for your lter by creating a 20 Hz Sine Wave for testing the lter you just created using the
MATLAB software
Instructions
In the MATLAB command window
1. Type in the code below:
– fs = 78125
– f = 20
– n = 1:65536
– xn = sin(2*pi*f*n/fs)
These objects (fs, f, n, and xn) are now created in Matlab (Figure 9):
– fs (Frequency Sampling): 78125 for low bandwidth 312500 for high bandwidth
– f(Frequency): 20 Hz
– n(Points): 1 to 65536
– xn (20 Hz Sine wave)
2. Type in the code below to plot the 20 Hz sine wave:
– plot(xn,’DisplayName’,’xn’,’YDataSource’,’xn’);gure(gcf);
A 20 Hz Sine wave graph (Figure 10) is created.
Figure 9. MATLAB command window and objects
Figure 10. 20 Hz Sine wave

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Step 4
Applying lter to the 20 Hz Sine wave
Instructions
In the MATLAB command window
1. Type in the code below to apply lter to 20 Hz sine wave (Figure 11) :
–l=lter(Hd,xn);
Objects lter is now created in MATLAB
2. Type in the code below to plot the result:
–plot(l,’DisplayName’,’l’,’YDataSource’,’l’);gure(gcf);
A 20 Hz Sine wave graph with the lter applied (Figure 12) is created.
3. By zooming into the graph you are able to search for the result (Figure 12)
Result after applying lter with 20 Hz Sine wave:
–Noise level will be ne after 4000 samples
Figure 11. MATLAB command window and objects
Figure 12. Zooming into the graph to see in-depth result

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Figure 13. Filter Coefcient Data
Transfer coefcient data to *.juf le
Step 5
Instructions
Information transfer and saving as a .juf le:
1. Name the *.juf le with a suitable title and bandwidth
2. Select Type (IIR or FIR)
3. Conrm Delay (Settling Samples)
4. Conrm Sections
5. Conrm Filter Coefcient Data
Design methods
There are different ways to transfer the Filter Coefcient data depending on the Design Methods (IIR or FIR)
Instructions
For Design Method FIR, enter the information below (Figure 13 and 14) :
1. ‘#Type: FIR”
2. ‘#Delay: ***” (From Settling Time/Delay)
3. “#Coefcients:”
4. Directly copy all the data from the Filter Coefcient data information (from Step 3)
5. Save the <anyname>.juf le
Figure 14. Example of Coefcient le

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For the IIR Design Method, the transfer to .juf is relatively more complicated compared to the FIR Design Method
Instructions
For Design Method IIR, enter the information below (Figure 15 and 16):
1. ‘#Type: IIR”
2. ‘#Delay: ****” (From Settling Time/Delay)
3. “#Sections:”
4. Steps to transferring data:
a. Scale Values
b. Conrm second part of SOS matrix
c. Conrm rst part of SOS matrix
d. Enter a blank line
e. Continue from step a to step d for subsequent Scale Values.
Figure 16. Example of .juf le
Figure 15. Filter Coefcient Data

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Upload .juf le to U8903A Audio Analyzer (Figure 17 and 18)
Step 6
Figure 17. Uploading .juf le and selecting lter
Instructions
1. Copy .juf le to a USB pen drive
2. Plug the USB pen drive into the U8903A Audio Analyzer
Steps to upload to the U8903A Audio Analyzer
3. Press “ ▼” key to access AA1 mode
4. Press “Meas. Cong” softkey
5. Press “Filter” softkey
6. Press either “LPF”, “HPF”, or “weighting” softkey
7. Select “Custom”
8. Press “Source” softkey
9. Press “Storage 1” softkey
10. Select the .juf le and press “Enter” key
11. The Filter will now be shown on either the LPF, HPF, or Weighting tab depending on your selection

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Figure 18. Selecting a source when uploading .juf le to U8903A
Conclusion
Due to differences in the testing environments and standards, general low pass lter, high pass lter, or weighting lter
will only satisfy and fulll some tests. Some users may require some custom lters in order to test DUTs. The U8903A
Audio Analyzer provides users the capability to upload their own custom lter. This demonstration will enable users to
create their custom lters with a computer using the MATLAB software.

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For further information, refer to Keysight U8903A Audio Analyzer Quick Fact
Sheet, Literature Number 5990-8504EN.
–Keysight U8903A Audio Analyzer,Data Sheet, Literature Number
5990-8499EN
–Keysight U8903A Audio Analyzer, Quick Start Guide, Part Number
U8903-90032
Ordering Information
Related Literature
For the most up-to-date and complete application and product information, visit our product website
at: www.keysight.com/nd/audioanalyzer

This information is subject to change without notice.
© Keysight Technologies, 2012 - 2014
Published in USA, August 2, 2014
5991-1558EN
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