GAOTek Digital Storage Oscilloscope is designed with 2 Analog Channels, 32 Trigger Channels and Digital Channels 4 /16 channels from logic analyzer pod and holds the memory of 512 Kilobytes and 1 Megabytes. It integrates DSO, Logic Analyzer, FFT Spectrum Analyzer, electronics counter, and clock jitter analyzer. The module efficiently solves complicated trigger problems by providing a comprehensive set of triggers such as rising or falling edge, pulse width, delayed, and count. This oscilloscope is commonly used for the maintenance of electronic equipment and laboratory work, and is suitable for field use in sciences, medicine, engineering and telecommunications.
- 5-in-1 design: digital oscilloscope, logic analyzer , FFT spectrum analyzer , electronics counter, and clock jitter analyzer
- 50 MSa/s to 500 MSa/s for 1 channel sampling rate.
- 1 Sa/s to 250 MSa/s for 2 channel sampling rate.
- Universal triggering with 512 trigger levels.
- Several types of triggering: I2C, SPI, UART, cross trigger, pre-triggering, pulse width, TV(NTSC 525, PAL 625) triggering and count
- Precision 125 MHz frequency counter, up to 7 digital resolution at 1 M memory for each analog channel
- X-Y plot allow to graph one channel to another.
- Multi window software.
- USB interface.
- Fast Fourier transform function for Bandwidth testing.
- Convenient Timing State display for logic debug
|Analog Channel||A1, A2|
|Input Bandwidth||2 channel DC – 125 MHz
4 channel DC – 60 MHz
|Input Impedance||1 MΩ / 15 pF|
|Maximum Input Voltage||± 50 V (± 100 V transient)|
|Sensitivity||10 mv/div to 4 v/div|
|Trigger Level (Universal)||512||2|
|Repetitive Mode||Up to 20 GHz|
|Spectrum FFT||110 MHz (Fast Fourier Transform)|
|Electronics Counter||Maximum 7 digits channel resolution|
|X-Y plot||Allow to graph one channel to another|
|Math||+ , –|
|Digital Channel||D0 ~ D3 (4 Channel) [8 Channel Trigger]
D0 ~ D15 (16 Channel) [Expand Pod]
|Input Bandwidth||D0 ~ D3 (4 Channel) DC – 50 MHz
D0 ~ D15 (16 Channel) DC – 10 MHz
|Sampling Rate||D0 ~ D3 (4 Channel) 0 MHz ~ 125 MHz
D0 ~ D15 (16 Channel) 0 MHz~ 25 MHz
|Record Length||256 K|
|Input Impedance||200 KΩ / 4 pF|
|Maximum Input Voltage||± 50 V (± 100 V transient)|
|Threshold Voltage||-1.8 V ~ +4.5 V|
|Trigger Qualify||0,1,X (don’t care) –settings for all channels|
|Trigger Level (Universal)||512||2|
|Sampling Rate||1 channel||50 MSa/s to 500 MSa/a by 1,2,5 sequence|
|2 channel||1 Sa/s to 250 MSa/s by 1,2,5 sequence|
|External Clock||0 MHz to 100 MHz for logic analyzer
10 MHz to 100 MHz for analog channel
200 KΩ // 4 pF, ± 50 V maximum.
|Record Length||1 channel 2 K/32 K/256 K/1 Mega
2 channel 1 K/16 K/128 K/512 K
|Power Supply||DC Adapter 5.75 V/2.5 A|
|PC Interface||USB 1.1 /2.0|
|Weight||3.09 lbs. (1.4 kg)|
|Dimensions||8.66 in x 5.59 in x 1.57 in (220 mm x 142 mm x 40 mm)|
- Calibrated Probe (1:1, 10:1) -2 pcs
- Logic Analyzer Pod
- Housing with wires and clips-20 pcs
- USB 2.0 cable
- Software CD
- DC Adapter 5.75 V/2.5 V
- User manual.
- Turn off the computer and all peripheral connected. Remove the computer power cord from the wall outlet
- Locate an available USB interface (USB 2.0 version)
- Connect the included USB cable to USB interface
- Plug in power source from +5.75 V / 2.5 A DC Adapter
- After checking all connections, turn on the computer peripherals. You are now ready to install the software
- Insert the distribution CD into the CD drive
- Select the File menu
- Enter file to run setup.exe installed in the CD drive
- Follow the on-screen instructions
Guide to Operation:
- When making measurements with the Digital Storage Oscilloscope / Logic Analyzer, data should be captured meaningful with some prior knowledge of the characteristics of the circuit under test.
- Before initiating any capture cycles, the DSO must be configured using the control program.
- To connect the DSO to the test circuit, there are two standard BNC probes, one for each Analog input channel and a series of mini-clips on the Logic Analyzer Pod for the Logic input channels.
- The scope probes have removable hook clips on their ends and an attached alligator clip for the signal ground connection.
- The Logic Analyzer Pod has inputs for 8 channels, D0 channel is the external clock input, and 3 ground points. For synchronous data capturing, connect the external clock sources to the D0 channel.
Connect the test circuit to the computer system. This will eliminate more noise in the test application due to ground level differentials. It is important when dealing with high speed timing analysis. Use a heavy gauge wire to make a connection between the test circuit ground and the case of the computer. Each Analog channel probe has a calibration adjustment. It is important that this calibration be made at least twice a year.
When connecting the probe to any signal, make sure that the signal voltage is within the limits of the DSO.
Logic Analyzer Pod markings:
This oscilloscope supports D0~ D3 channel data inputs.
GND –Signal ground connection.
The wires and the clips that come with the pods are modular. The pods, wires, and clips are disconnected from each other by gently pulling them apart. Removing just the clips, and leaving the wires connected to the pods and this allows the connections to the wires and posts test circuit of up to 0.025 in (0.64 mm).
This GAOTek Digital Oscilloscope has Main screen, Menu Bar, Timing Window, State List and Tool Bar.
The picture describes the tool bar:
Data is displayed in state list format in this window.
Ground Point Tick Marks
Located to the right of the Analog Display. The Ground Point Tick Marks are `-|’ shaped. These display the ground points of each analog channel. Ground Point Tick Marks associated with Channel A1 are leftmost and Channel A2 through A4 are successively further to the right. They are color coded the same as the data channels that they refer to. These Tick Marks can be moved by grabbing and dragging with a pointing device, or from the Channel dialog box.
Trigger Level Tick Marks
Located to the left of the Analog Display. The active Trigger Level (s) are displayed here with Level 1 displayed to the right of level 2. The Trigger Level Tick Mark is ‘→’ shaped. They display the trigger levels and are color coded the same as the trigger cursor. These tick marks can be moved by grabbing and dragging with a pointing device, or by the trigger dialog box.
Logic Analyzer Binary data
To the left of the Logic Display are the binary values of each logic input at the Vertical Cursor A and Vertical Cursor B positions. To the right of the Logic Display are the binary values of each logic input at the Trigger Cursor position.
The Trigger Cursor is a vertical cursor that defines the actual trigger position within the data buffer of the trigger channel. Pre and post trigger information are directly related to the Trigger Cursor position.
The trigger cursor position can be changed by:
-Grabbing and dragging the Trigger Cursor with a pointing device
-Selecting the Trigger cursor by clicking on the Trigger button (in the Selection Buttons) and using the Horizontal Scrollbar.
Horizontal V1 Bar and V2 Bar
The Horizontal Cursors provide an easy means of voltage measurements. For a selected channel, the voltage difference between the two cursors is shown in the Parameters Display area.
V1Bar and V2Bar can be moved by:
- Grabbing and dragging the cursors with a pointing device
- Selecting the Cursor by clicking on the V1Bar or V2Bar button and using the Vertical Scrollbar.
Vertical Cursor A and Cursor B
The Vertical Cursors provide an easy means to make time measurements. For a selected channel, the time difference between the two V Bar and the trigger cursor is shown in the Parameters display area. Cursor A and Cursor B can be moved by:
- Grabbing and dragging the cursor.
- Selecting the Cursor by clicking on the Cursor A or Cursor B button and using the horizontal Scrollbar.
- Selecting the trigger cursor from the view menu.
Horizontal Scroll Bar
This scroll bar is used in conjunction with a selected waveform or cursor. The Horizontal Scroll Bar will move a selected waveform or cursor left or right in the display area. The Horizontal Scroll Bar works with Display, Analog input channels, Memory, Logic Analyzer channels, Cursor A, Cursor B, and Trigger Cursor.
Vertical Scroll Bar
This scroll bar is used in conjunction with a selected waveform or cursor. The Vertical Scroll Bar will move a selected waveform or cursor up or down in the display area. The Vertical Scroll Bar works with Display, Analog input channels, Memory, V1Bar, and V2Bar.
- Channel display: Select display Channel (A1, 2, 3, 4 and M1, 2, 3, 4).
- Object point: Set cursor Bar (V1, V2, Trigger, Screen (left or center)) for zoom operates reference. Moves one or more cursors to the display area. These commands are also available by clicking on the toolbar.
- Object is cursor A: Centers waveform display area around Cursor A.
- Object is cursor B: Centers waveform display area around Cursor B.
- Object is cursor trigger: Centers waveform display area around the Trigger Bar.
- Object is cursor A1-4: Let v1 and v2 have reference object.
When Display is checked, the channel will be displayed on the screen. When Display is not checked, the channel will not be displayed on the screen. Turning display off for a channel will both speed up and un-clutter the display. However, the data is still acquired from that channel unless transfer is turned off.
Channel Dialog Box
Show the Channel Dialog Box. All channel parameters are displayed in this box and can be altered in it as well. You can bring up this dialog by clicking on the “view menu”, select tall or wide window. A different channel can be selected by hitting the “A1, A2, A3, A4” Ch. Select button.
This controls the attenuation level for the probe inputs. This should be set to match the probe itself, either 1X, 10X, 100X or 1000X. When working with signal amplitudes within? 0 V, either the 1X or the 10X setting can be used. However, if the signal amplitude is outside of? 0 V, use the 10X setting. Note that using the 10X setting with both the probe and the scope even for signals within? 0 V will provide better frequency response through the system due to smaller voltage swings through to the digitizer.
Voltage range Probe and probe settings:
- 10 mv/div to 2 v/div @probe 1:1
- 100 mv/div to 20 v/div @probe 10:1
- 1000 mv/div to 200 v/div @probe 100:1
- 10 v/div to 2000 v/div @probe 1000:1
The three selections available are AC, DC, and GND couple. Coupling can also be changed by Channel dialog box. In the AC setting, the signal for the selected channel is coupled, effectively blocking the DC components of the input signal and filtering out frequencies below 10 Hz. The input impedance is 1MΩ || 5pF. In the DC setting, all signal frequency components of the signal for the selected channel, are allowed to pass through. The input impedance is 1MΩ || 5pF. In the GND setting, both the input and the A/D converter are connected to ground. Again, the input Impedance is 1MΩ || 5pF. Use for setting the ground reference point on the display or if calibrating the DSO board.
- The Go command tells the DSO to start acquiring data when the trigger conditions are satisfied. Pressed means start capture.
- Pressed means stop capture.
- Automatic setup parameters for capture.
- Force hardware to get capture data even trigger has not happen
1 Sa/s to 250 MSa/s Sampling rate
1 Sa/s to 500 MSa/s for reducing channel mode.
Time base: 50ps / Division to 10000s / Division displayable.
0 to 100 MHz for Logic Analyzer.
10 to 100 MHz for Analog channel.
External Clock Delay: ~10ns
Analog to Digital skew
Analog channels to channels skew are 1ns. Analog channels are 5ns tolerance compare to Logic channels. External Clock: 2/0 ns relative to clock edge. Minimum required: a minimum of 256 Mbytes RAM is necessary to use the DSO control program. 1 Giga Bytes system RAM will be better.
Magnification: from 1/1000X to 50X
Cursors: There are two cursors. Cursor-A Cursor-B, V1 and V2 they are time and voltage cursor.
They can be moved using the horizontal and vertical scroll bars or by grabbing and dragging them. Differences are automatically calculated and displayed on the screen.
- Connect the scope probe Ground Connection to the BNC GND.
- Hold the probe’s tip against the calibration point on the BNC center Hole.
- A Square wave signal should appear on the screen.
- Adjust the probe calibration until a true square wave is shown on the screen, noting the Corners of the waveform which should be sharp and square, not rounded over or peaky.
The VISUAL BASIC programming library is a source code level set of procedures that allow full control of the GAOTek Digital oscilloscope from your own programs. This is an optional package. The package includes the source files for the library, example code for using the library. The library consists of subroutines for full control of the GAOTek Digital oscilloscope. This includes routines to initialize the board, setup trigger conditions, setup acquisition parameters like sample clock rate and source, choose the gain and coupling settings, transfer data from the board to the PC, and save and load data to files.
GAOTek Digital oscilloscope support high accuracy and high resolution electronic counter base on oscillator inside. It can reach 7 digits resolution by selecting large memory one of 512K, 1Mega. It also has frequency calibration offset. User need use atomic clock to make sure you have an extra high accuracy clock to calibrate.
Clock Jitter Analyzer
GAOTek Digital Oscilloscope support high accuracy Clock Jitter Analyzer base on oscillator inside. It has following function.
- M1 ← A1 Period Jitter, M2 ← A1 Cycle to Cycle Jitter.
- M1 ← A2 Period Jitter, M2 ← A2 Cycle to Cycle Jitter.
- M3 ← A1 Time Interval Period Jitter.
- M3 ← A2 Time Interval Period Jitter.
Period jitter is maximum change deviation in a clock transition from an ideal clock. This Software support two reference ideal clock. One is user input interval period value (M3← A1 Time Interval Period Jitter). Another is program automatic search all memory to get mean clock period (M1← A1 Period Jitter). Then put jitter to every clock cycle in backup memory.
Cycle to cycle period jitter is the change in a clock transition from its corresponding position in the previous cycle.
Cycle to cycle Jitter j1 = t2 – t1
Cycle to cycle Jitter j2 = t3 – t2
Long term period jitter is the change in a clock transition from first clock to end of clock in memory compare to ideal clock.
It can get Long term period jitter T1 from diagram after choose M3 ← A1 Time Interval Period Jitter. It also shows the first and ending lock position.
Setting up group
Set following after select group edit.
- Select which group to display. Groups can be in different bases
- Set Base.
- Set channel combination.
- Set serial or parallel bus in serial protocol combo.
Setting up the Channel/State/Timing window
Setting up the state / timing display.
- Set group.
- Select which group to display. Groups can be in different bases.
- Select display channel on or off. Timing display also can define timing height.
Setting up the serial bus definition
System has default popular I2C SPI UART standard protocol. These bus definition are the universal structure. User can define their own serial protocol.
- Sum of all voltages * sample time.
- Cursor A (time) Position of Cursor A in time.
- Cursor B (time) Position of Cursor B in time.
- V1Bar (voltage) Position of V1Bar in voltage.
- V2Bar (voltage) Position of V2Bar in voltage.
- Trigger cursor Position of trigger cursor in time.
- A – B (time) Time difference between Cursor A and Cursor B.
- V1 – V2 (voltage) Voltage difference between V1Bar and V2Bar.
- A – T (time) Time difference between Cursor A and trigger cursor.
- B – T (time) Time difference between Cursor B and trigger cursor.
V_max: Maximum voltage.
V_min: Minimum voltage.
Peak to peak: The difference between maximum and minimum voltages.
Average: Average of minimum and maximum voltages.
rms SQRT: ((1/ # samples) * (sum ((each voltage) * (each voltage))))
rms (AC): SQRT ((1/ # samples) * (sum ((each voltage – mean) * (each voltage – mean))))
period: Average time for a full cycle for all full cycles in range.
duty cycle (rising) A ratio of width (rising) to period. Starting with a positive edge using midpoint.
duty cycle (falling) A ratio of width (falling) to period. Starting with a negative edge using midpoint.
rise time(10..90) Average time for a rising transition between the 10 % to the 90 % points.
rise time(20..80) Average time for a rising transition between the 20 % to the 80 % points.
fall time(10..90) Average time for a falling transition between the 10 % to the 90 % points.
fall time(20..80) Average time for a falling transition between the 20 % to the 80 % points.
pulse width (positive) Average width of positive pulses measured at 50 % level.
pulse width (negative) Average width of negative pulses measured at 50 % level.
frequency Average frequency of waveform.
Trigger menu commands
|GAOTek Digital Oscilloscope
|With IF word xx happen yy times then next level else go to level 0 trigger structure. 4095 event counter/every level. 1 to 4095* (1 sec to 10nsec) delay time /every levels.
Width pulse detect from <15 nsec to 4095 sec / every levels.
trigger before delay (YES)
SPI interface (NO)
serial trigger (RS-232…) (NO)
I²C serial trigger (NO)
|GAOTek Digital Oscilloscope
|With IF word xx happen yy times then next level else go to level 0 Trigger structure. 4095 event counter/every level. 1 to 4095* (1 sec to 10nsec) delay time /every levels.
Width pulse detect from <15 nsec to 4095 sec /every levels.
Trigger before delay (YES)
SPI interface (YES)
serial trigger (RS-232…) (YES)
I²C serial trigger (YES)
all kind of trigger (YES)
It is universal trigger structure.
A trigger word is the pattern that the Logic Analyzers needs to see before it will start to acquire data. The trigger word is made of a series of “1”, “0” and “x” (don’t care) bits.
It can set at trigger form or parameters form as following.
Ch7…0 Edit pattern for channels 7 to 0 Logic Trigger if condition is true or false. “Enter” logic need trigger condition from false to true.
“Exit” logic need trigger condition from true to false.
How to set trigger word
- Edit all 8 channels at a time. Edit the pattern: The LSB is to the right. Each bit can be set to “0”, “1” or “x” (don’t care, true, false).
- Set the trigger logic to “Enter” (trigger when pattern matches) or “Exit” (trigger when pattern stops matching).
The trigger position defines how much data is captured prior to the trigger event and how much data stored after it. You set the Trigger position by moving the trigger cursor. This feature allows you to see the data that led up to the trigger as well as what happened after the trigger.
GAOTek Digital Oscilloscope support 2, 512 trigger levels. All trigger source can come from analog channel A1~A3 or 8 channel logic analyzer. Because logic world now is very complex, like SPI, RS232, I²C…. need a lot of trigger level to complete it. Every trigger level support ” if xx happen yy times then next level else go to level 0″.
Event: allow trigger happen after match trigger condition max 4095 times delay: wait 1 to 4095*(1 sec to 10nsec).
<Pulse Width: Detect pulse width small than xx sec.
<Pulse Width: Detect pulse width big than xx sec.
You can set the trigger logic to “Enter” (trigger when pattern matches) or “Exit” (trigger when pattern stops matching).
Two trigger check be selected “trigger group” and serial trigger.
Trigger group check: Select which base you want to edit in.
Serial trigger: 7 kind of serial trigger
- Width Bit
- Width Bit with timing
- Width bit by rising (falling) clock
- 1 Bit data by rising clock (SPI)
It is same as “one bit by rising clock”. A serial of bit stream synchronous with clock. LA0 default as data, LA1 default as clock in I²C format. Level 0 ~ 1 is I²C start format.
I²C need 73 trigger levels to complete trigger. That is why GAOTek Digital Oscilloscope design need 512 trigger levels
X-Y Oscilloscope plot screen
An X-Y Plot allows you to graph one channel vs. another.
FFT commands (Window menu)
The FFT window allows control and display of FFT’s.
The following controls are available:
Window Select the FFT window type: (Triangular, Hanning, Hamming, Blackman-Harris, Rectangular, Wetch and Parzen).
Sample points select how many points the FFT will sample, points can’t exceed memory depth. Horizontal zoom Select horizontal zoom ratio.
The FFT routines will process the selected channel starting at Cursor A and continue until “Sample Points” number of points has been reached. If Cursor A is not within the buffer, start of buffer will be used.
Waterfall display shows successive FFT breakdowns simultaneously on the screen offset from each other. This creates a waveform that shows the frequency behavior overtime. Up to 10 FFT break downs are shown at one time with the oldest furthest back. Typical use include impulse response decay time in audio work.
To save FFT data go to File Save and choose a file type of “FFT”.
USB driver Install:
Windows 2000 USB driver install
- Connect the USB 2.0 control Interface to the computer.
- Click Next to continue
- Choose the option “Search for a suitable driver for my device (recommended)” and click next to continue
- Check the box “Specify a location” and browse the path to be installed. Press OK and click next to continue.
- Below window displays.
- Click yes to continue
- Click Finish the installation completed.
Fast Fourier Transformations
Understanding FFT’s Application
Introduction to FFT
Detecting and measurement are the basic functions of signal processing. In some application, it is important to analyze the periodic components of sinusoidal signals. FFT can serve as a tool to dismember a signal into its periodic components for analysis purposes.
- Testing of signal voltage in radio broadcasting equipment and circuit debugging
- Jitter and power analysis
- For research and design
- Cursor and pulse width readings
- Rise time and propagation delay measurements
- Acts as a simple signal tracer
- Measurement of the functions of the individual component of the device
- Measurement of components’ minor variations in operations
- Prevention of erroneous replacement of parts
Fundamental principles The Fourier Transformation Formula:
Tk : The mapping data value for the Time Domain
F(x): The mapping data value for the Frequency Domain
M : FFT data length
X : The mapping data value for the Frequency Domain
i : Imaginary number
The result of the formula is a vector of complex number. To show this on the screen, we resent the Frequency as horizontal coordinate, we make the leftmost position representing zero frequency that is the direct current component. Harris had pointed out that due to periodic characteristics of FFT, we could observe the phenomena of discontinuation at the binderies of a finite length sequence. Therefore when we select randomly a signal sample, we could see points of discontinuation as a result of periodic expansion. This would produce leakage of Frequency Spectrum across the whole frequency band. To suppress the amplitude of sample around the binderies, we must apply Weight function to it.
The Vertical Axis on the screen is expressed in terms of Magnitude, Decibel (db) and Logarithm.
dBm Ps = 10 log (Mn² / Mref²)
20 log (Mn / Mref)
Here Mref represents the reference value. It is defined as 0 dBm or 0.316 V Peak-to-Peak Value or Effective Value 0.244V. It is defined as 1.0 mW or it is defined as Resistance Value 50 Ω.
In this mode, the display is expressed in decibel and the Measurement is expressed in Magnitude. Generally speaking, the Spectrum Processing System is expressed in the following formula:
This formula utilizes Weighting function that is also known as Window.
For example, Hanning, Hamming, Blackman, Triangle and Rectangle.
These are further explained as following:
Hanning: It is cos α (θ) type window, expressed mathematically as following:
a (n) = 0.5 [ 1-cos (2 πn / N ) ]
Hamming: It is similar to Hanning. The only difference is the coefficients for cosine term.
a (n) = 0.54 – 0.46 cos ( 2 πn / N ) , n = 0, 1, 2…., N-1
Blackman: It is the sum of a series of cosine terms. It is equal to weighting function.
Triangle: Triangle Weighting Function, It is define as following:
Rectangle Weighting Function
The Characteristics of Weight Function:
|Window||Highest Side Lobe||3db Bandwidth (bins)||5db Bandwidth (bins)||Scallop Loss (db)|
The functionality of FFT can be achieved through the use of Utility. To use the Utility, We must set Channel/Math first, and then turn on FFT or Bw.sweep. We have to bear that in mind that we could only analyze one channel at a time. After finish all the settings the screen will display the FFT Channel. The differences between FFT and Bw.sweep as follow:
If we are using this mode, we are analyzing Channel A1 or Channel A2 in a Real-Time Mode. To achieve the state of Synchronized Display. We are measuring time Domain while we are displaying Fourier Frequency Domain. In addition to that, we are able to analyze the stored signal easily. We only need to read the file on A1 Channel or A2 Channel, and then thrown on FFT. Whether we turn on Go or not is the difference in retrieving signals.
When turning on this mode, we are analyzing A1 Channel or A2 Channel through the Frequency Sweep Mode to achieve the State of Frequency Output. The user must apply additional frequency to the point of measurement. Also we have to increase the frequency from small to large gradually. The finer the increment of frequency, the better the obtained data will be. Attention must be made to clear the Frequency and record Sweep Frequency again every time when we turn on Go to retrieve signal. When a user set the Mode, he can also set the FFT parameters. These are the required settings and they are explained as following:
From channel A1, A2, M1 or M2.
The points to be used are 256, 512, 1024, 2048, 4096, 8192, 16384 and 33678. The user could think of these points as the scope of period. It can be understood that the more points we are taking, the better the results will be except the speed of it would be sacrificed. This is because the more you analyze the more time it takes to get the job done. It is a user’s responsibility to make a judgment as to how a compromise should be achieved.
The window is also known as (Weighting function), it includes Hanning (a fixed value, generally is peaking), Hamming, Blackman, Triangle and Rectangle. Due to periodic characteristics of FFT, we observe the discontinuation Phenomena around the boundaries of the finite length sequence. We must use Window to suppress the amplitude of the sample around the boundaries.
Rectangle Weighting Function
The Vertical Axis on the screen is expressed in terms of magnitude, Power Spectrum and Logarithm.
- Magnitude: The magnitude of the Polar Coordinates on the screen.
- Logarithm: In this mode, it displays Power spectrum and the measurement is expressed as Magnitude.
- Power Spectrum: By formula Ps = 20 log (Mn/Mref).
Here Mref represents the Reference Value of 0.316 V.
- It is defined as 0 dBm. 0.316 V p-p or 0.244 V
- Effective Value also known as 1.0 mW and the Resistance of 50 Ω.
- The Vertical Axis on the screen is expressed in terms of Magnitude, db or Logarithm.
These are explained as following:
DB/div: It is active only when Gain Type is set to Power spectrum. It is the unit of the Vertical coordinate. It represents DBm. There are four different scales: 5, 10, 20, and 50 DBm.
DB/offset: It is active only when Gain Type is set to Power spectrum. It can change the position of FFT to make it going up and down.
To obtain the measured data, using Ctrl and Alt keys plus Left or Right key to measure frequency.
To measure Magnitude, we can use Ctrl or Alt key plus up or down key. After that we can get the data displayed in the rectangle frame of FFTb parameter.
Notes: It is highly desirable to confirm the following items before doing analyzing:
- If the measurement is for low frequency, we ought to make sure the frequency of the sample is not too large. Since the larger the frequency of the sample is the large the Bandwidth. The sample frequency needs to be as twice as large as the frequency to be measured.
- It is undesirable to use Logic Analyzer and FFT simultaneously.
- It is desirable to have waveform on the Time Domain. The stronger the waveform the better the accuracy of the results.
- To obtain the highest speed on FFT, we could turn all the channels off except for FFT.
- The values of Depth can be 4K, 64K. When using 4K, we are using the real part and Imaginary part of the integer results of the Simulator Output for independent Probability Noise Signal. The MSE calculation results is obtained using 16 bits FFT processor with db less than 75 DB. If using db value greater than 75 DB, we are going to get too great an inaccuracy. When we are using 64K Depth, we are doing floating point calculation therefore the machine we use must have floating point math coprocessor.