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Symmetricom 5115A Скачать руководство пользователя страница 94

88

Appendix B: Theory of Operation

The concept for direct-digital phase-noise measurements is shown in

.

Figure B-2: The RF signals are immediately converted to digital samples in order to perform direct-digital phase-noise

measurements.

B.2 Theory

The analog-to-digital converters have 14 bits of precision and maximum sampling rates of
80 MHz. In order to prevent harmonics, spurs, and noise from aliasing into the measured
spectrum, a 30 MHz analog anti-alias filter is employed before the RF signals are sampled. The
heart of the approach is the down converter that immediately follows the sampler. In-phase
samples of each input signal are multiplied by the sine and cosine of a synthesized local oscillator
and low-pass filtered. When the LO frequency is approximately equal to the input frequency, the
output of the filters are in-phase (I) and quadrature (Q) base-band samples. The phase difference
between the input signal and the synthesized LO is computed using the arctangent function as
shown in

Figure B-3: A local oscillator synthesized from the internal clock down-converts the input to base-band where the

samples are used to compute the phase difference between the LO and the input.

This step is the heart of the direct-digital technique. It is not necessary to down-convert to DC
before computing the phase difference. A small DC offset causes the phase to accumulate nearly
linearly. Although the arctangent function repeats every

π

radians, it is possible to unwrap the

phase and recover the correct linear function. This should be contrasted with the analog approach.
The double balanced mixer produces a distorted sine function of the phase difference. As the two
inputs approach the in-phase condition, the output of the mixer is insensitive to the phase
difference between the signals, and the distortion makes it impossible to accurately compute the

Analog/Digital

Converter

Analog/Digital

Converter

Input

Reference

Digital Signal Processing

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Содержание 5115A

Страница 1: ...5120A 5120A 01 5115A Phase Noise Test Set Operations and Maintenance Manual For Software Revision 276 and Above Part Number DOC05120A Rev M ...

Страница 2: ...ments 5115A Updates for software changes 12 19 2005 PKS F Software changes noise floor specs and DOCSIS 01 19 2006 GAR G Frequency counter precision and spur detection 05 16 2006 GAR H Documents 5120A 01 noise floor and time constant 04 16 2007 GAR J Correct number of Telnet sessions for data port 01 18 2008 GAR K Revise 5120A 01 specifications printer update photos 03 17 2008 GAR L Add power down...

Страница 3: ...ower 13 3 2 3 User in Control 14 3 2 4 User Specified Title 14 3 3 Types of Screens 15 3 3 1 Plots 15 3 3 2 Tables 15 3 3 3 Configuration Screens 15 3 4 Parameters Input Components and Editors 16 3 4 1 Numeric Parameters 16 3 4 1 1 The Number Pad Editor 17 3 4 1 2 The and Integer Parameter Interface 18 3 4 2 Mutually Exclusive Options 18 4 Global System Settings 21 4 1 The Settings Screen 21 4 1 1...

Страница 4: ... the Frequency Difference Plot 48 5 4 1 Scaling the Frequency Difference Plot 49 5 4 2 Pausing or Resuming Updates 49 5 5 Configuring the Frequency Counter 49 5 5 1 Changing the Reference Frequency 50 5 5 1 1 Automatically Setting the Reference Frequency 51 5 5 1 2 Manually Setting the Reference Frequency 51 6 Collecting and Viewing Data Locally 53 6 1 Starting and Stopping Data Collection 53 6 2 ...

Страница 5: ...sing the DOCSIS Option Locally 70 8 0 3 Using the DOCSIS Option Remotely 71 8 1 5120A 01 Internal Reference 72 8 1 1 5120A 01 Internal Reference Calibration 72 8 1 1 1 Calibrating 5120A 01 Internal Reference 72 8 1 1 2 Calibrating 5120A 01 Internal Reference Remotely 73 9 Maintaining a PNTS 75 9 1 Calibrating the PNTS 75 9 2 Cleaning the PNTS 75 9 3 Cleaning the Fan Filter 75 10 Troubleshooting 77...

Страница 6: ...iv Contents Index 97 ...

Страница 7: ...bol means the following information is a note that gives you important information that may affect how you use the PNTS Caution refer to manual Read all instructions in this manual before using this product Caution Risk of Electrical shock Fuse symbol LAN port network DO NOT CONNECT TO TELECOM CONNECTIONS THAT CARRY HAZARDOUS VOLTAGES Universal Serial Bus USB port Mains power on and off Mains powe...

Страница 8: ...neral Chapter 4 Global System Settings on page 21 describes individual system settings such as system time network configuration and printer settings in detail Chapter 5 Configuring Data Displays on page 31 describes the various data displays for the 5120A 5120A 01 and 5115A and how to manipulate and configure each data set Chapter 6 Collecting and Viewing Data Locally on page 53 describes how to ...

Страница 9: ...he test set Convention Definition Bold Words in bold show Buttons and icons to click Menu options to select Commands to type Non variable information displayed in response to commands Italics Words in italics show Names of windows and dialog boxes Variable information displayed in response to commands State information label and button captions ...

Страница 10: ...ce is 50 Ω and the ideal nominal input level is near 1 VRMS The test set automatically initializes itself measures the frequencies of the input signals configures the signal paths and collects data All models measure phase noise Allan deviation frequency counter frequency difference and phase difference An Ethernet port make remote control measurement retrieval and printing to network printers pos...

Страница 11: ...ly do not attach a a signal to the reference port Consult Appendix A Electrical Specifications on page 82 for internal oscillator performance specifications The phase noise and phase spurs that are present on the Reference port are scaled by a factor of 20 log Finput Fref when displayed Consider the following example A spur on a 10 MHz signal is connected to the Input port with a clean 5 MHz conne...

Страница 12: ...6 1 Introduction ...

Страница 13: ...l cables are properly connected The power cord must be located for easy removal Verify that input line voltage and current capacity from the supply circuit are within specifications before turning on power to the test set Operating and maintenance personnel must receive proper training before setting up or maintaining electrical equipment 2 2 Setting Up a PNTS The test set ships ready to set up on...

Страница 14: ... 4 Plug the female end of the power cord into the male IEC 320 plug on the rear of the test set 5 Plug the male end of the power cord into a 100 240 V AC 50 60 Hz power source Caution Ensure that this power supply cord is connected to a properly grounded mains receptacle 6 Connect one coaxial cable from the Device Under Test DUT signal source to the Input port of the test set 7 Connect another coa...

Страница 15: ...3 2 1 Collecting State on page 13 the instrument is ready for normal operation If the Self test has failed for the following item s message displays call Symmetricom Customer Assistance see page 95 Once Ready is displayed in the status field data can be collected 2 2 2 Turning Off the PNTS There is a small chance that turning off the test set by removing the power cord could cause the operating sy...

Страница 16: ...10 2 Setting Up a PNTS ...

Страница 17: ... major components These are described in section 3 2 Main Screen Components on page 13 Figure 3 Default Main Screen Note When the 5120A 01 is used with internal references the Reference field reads Internal and frequency and power are not shown Current collecting state Frequency and power of input signals Collection Duration User specified title Softkey labels show the function that will be execut...

Страница 18: ...repeatedly executes its function as well Using the mouse to interact through the softkey interface is also useful because it minimizes physical disturbance to the test set Physical disturbance can affect the accuracy of sensitive measurements 3 1 1 Navigation Starting with the phase noise plot as shown in Figure 3 pressing the Allan Deviation Plot button would Display the Allan deviation plot Chan...

Страница 19: ...e and the test set has begun collecting and presenting data When Collecting state is reached the test set starts displaying measurements and tracking how long it has been collecting See the top left corner of Figure 3 for an example of the collection duration You can Stop collecting from either the Initializing or the Collecting state Note that updates to some data sets can be paused The normal ba...

Страница 20: ...user can take control from the local user See 7 2 1 Taking or Yielding Remote Control on page 58 for details on taking Remote control When the test set is powered on neither user is in control The first user to execute a command or make a setting which requires control of the test set implicitly takes control If the Local user were to press the Start button on the front panel they would automatica...

Страница 21: ...ple table on the right side of Figure 4 on page 12 The scroll keys have different effects depending on the type Read only tables scroll the data set one page at a time Interactive tables select the row following or preceding the currently selected row Interactive tables move the selection a row at a time because they allow you to operate on the selection An example of this is the f phase noise plo...

Страница 22: ...ain such as the frequency counter s reference frequency and test mask points x and y coordinates All numeric parameters can be set as described in 3 4 1 1 The Number Pad Editor on page 17 Those in the integer domain can also be set as described in 3 4 1 2 The and Integer Parameter Interface on page 18 Numeric parameters are presented using the following components which can be directly manipulated...

Страница 23: ...rmat The button toggles the sign of the mantissa when it is pushed before the EXP button and toggles the sign of the exponent when pushed after the EXP button Figure 6 The Number Pad Editor Number pad buttons can be clicked with the mouse Note the white rectangle on the button It indicates focus The arrow softkeys move the focus in the direction they indicate wrapping to the first button on the ax...

Страница 24: ...17 for an explanation of focus As focus is changed on mutually exclusive options the focused option is selected The new setting takes effect when the Apply softkey is pressed The following is an example of how to toggle the Address Assignment option assuming the state in Figure 7 as a starting point To change the Address Assignment method 1 Press the down arrow softkey until focus reaches the DHCP...

Страница 25: ...tions and Maintenance Manual 19 Note that the buttons representing the options can be clicked directly with a mouse Clicking an interactive component moves the focus it does not have to be moved with the arrow softkeys ...

Страница 26: ...20 3 The Screen and Basic Concepts ...

Страница 27: ...ngs Screen The Settings screen shows most current settings and serves as a submenu to the settings groups listed above To access the Settings screen 1 Press or click the Settings and Options softkey See 3 1 Softkey Interface on page 12 for basic navigation instructions 2 Press or click the Settings softkey Figure 8 Settings Screen Note that the Settings screen displays the instrument s current IP ...

Страница 28: ...tings to access the Settings Screen shown in Figure 8 on page 21 3 Press Date and Time 4 Use the arrow softkeys to access the date time fields you wish to modify 5 Adjust the numeric fields as described in section 3 4 1 Numeric Parameters on page 16 6 Select the preferred date time format as described in section 3 4 2 Mutually Exclusive Options on page 18 The field labeled Sample shows how time st...

Страница 29: ...See 3 4 2 Mutually Exclusive Options on page 18 and 3 4 1 Numeric Parameters on page 16 for details on how to set them The PNTS ship with the default network settings shown in Table 1 If your network has a Dynamic Host Configuration Protocol DHCP server and the DHCP assignment method is selected the IP address does not have to be configured Once the test set is connected to the network it should r...

Страница 30: ...ow labeled Address Assignment 6 Press the right arrow softkey to toggle the setting to Static Address The spin buttons for the IP address network mask and default route octets become active they are grayed out for the DHCP method 7 Press the down arrow softkey to move to the row labeled IP Address Press the right arrow softkey to access and set the individual octets as described in 3 4 1 Numeric P...

Страница 31: ...fter the next attempt has been scheduled the test set is attached to the network 4 The test set does not request a lease for another 2 minutes it scheduled the next request to run 3 minutes after the failed attempt 1 minute ago The test set can be forced to request a lease by restarting the DHCP client application A push button on the network settings screen is used for this purpose To restart the...

Страница 32: ...ore jobs can be sent to a network printer or retrieved using FTP To configure printing 1 Navigate to the Settings screen see 4 1 The Settings Screen on page 21 2 Press Printing 3 Use the arrow keys to select a destination for print jobs see 3 4 2 Mutually Exclusive Options on page 18 for details If you selected the Network destination the IP address and port number in the fields labeled Remote Hos...

Страница 33: ... PCL5 or PostScript printer no proprietary software is required for it to function If you must install proprietary software on a PC for the printer to function it will usually not work when plugged directly into a test set via USB Configure the test set to print to the Local destination in the format the printer supports 2 Print the data sets of interest using the methods described in sections 6 2...

Страница 34: ... using anonymous login you will not need a password See Figure 8 on page 21 to determine the test set s IP address Note Be sure to configure the ftp client for binary file transfer Most command line based ftp clients accept the bin command for this purpose See your ftp client software documentation for details on how to set binary file transfer 2 Download the files from the printfiles directory Th...

Страница 35: ...access version information 3 Press Return to go back to previous screens 4 1 5 Restoring Factory Default Settings Parameters configured using the Settings submenus persist when the test set is power cycled Other settings such as the frequency counter s user supplied reference frequency and test masks also persist All persisted settings can be reset to the values the 5120A or 5115A was shipped with...

Страница 36: ...of the USB ports on the rear panel of the unit 2 Navigate to the Settings and Options screen see 4 1 The Settings Screen on page 21 3 Press External USB Drive A screen with information about the upgrade process is displayed 4 Press Check for Updates A dialog requesting confirmation that you would like to use this image for upgrade is displayed 5 Press Yes The test set copies the new software image...

Страница 37: ...first displays on the screen after collection starts then the screen updates as often as a few times per second The first range of data displayed is from approximately 0 1 Hz to the maximum The longer the data collection period the more data is available to display phase noise at lower offset frequencies The test set detects spurs caused by its own operation These spurs are referred to as internal...

Страница 38: ... floor of the instrument is above this level outside the flicker region In the case where phase noise measurements are less than 10 dB above the measurement noise floor a correction factor can be subtracted from the Phase Noise measurement to provide a best estimate of the phase noise of the signals Table 2 lists the suggested correction factors The 5115A does not perform cross correlation and can...

Страница 39: ... and 30 Automatically scale the x axis Sets the x scale to logarithmic Sets the minimum and maximum frequency to fit all data Fixed logarithmic scale x Shows from 1 to 9 decades Allows the following values Hz 10 4 10 3 10 2 10 1 100 101 102 103 104 105 and 106 Fixed linear scale x Forces minimum x value of 0 Hz Allows the following maximum values Hz 10 3 10 2 10 1 100 101 102 103 104 105 and 106 N...

Страница 40: ...y zooming in on a region of interest This region is designated by dragging a rectangle around it To scale the phase noise plot using a mouse 1 Right click anywhere on the plot and select Scale Zoom The mouse cursor changes to a cross hair Tip Invoke this function by pressing the Z key on a USB keyboard Tip Cancel the zoom operation by clicking the right mouse button Do so at any point in this inst...

Страница 41: ...re repositioned or trace a new measurement at their designated frequency When both markers are positioned the difference between their coordinates is calculated and displayed When either marker is tracing a measurement that is part of a spur a small color coded window pops up to indicate the spur s frequency and power The power displayed in the window should be used to determine the power level of...

Страница 42: ...ng softkeys Pressing and holding the key the marker moves by a single point a few times then in increments of 2 points a few times then 4 increasing by a factor of 2 until 64 points at a time are skipped at this rate the entire data set can be traced in a reasonable amount of time Note that movement in terms of data points is not possible while no data set is plotted The and softkeys move the mark...

Страница 43: ...position the marker To remove all markers and related information windows 1 From the front panel press Phase Noise Plot 2 Press Config Phase Noise 3 Press Markers 4 Press Hide Markers All markers and windows are removed from the screen Alternatively right click the phase noise plot at any time and select Markers Hide The marker softkey interface need not be active Once a marker is placed at a freq...

Страница 44: ...dered to be the current test mask The current test mask changes as masks are loaded and saved The current mask is highlighted in the editor s load and save softkey interfaces It is marked with a dot in the mouse popup menu Loading saving and editing of test masks is done with the test mask editor To access the test mask editor 1 Select the Phase Noise Plot see 3 1 1 Navigation on page 12 for detai...

Страница 45: ...s Add Point to add a new point to the test mask or go to Step 4 to edit existing points or Step 6 to delete points Tip Right click the test mask table and select Add Point in the menu without entering the Edit Mask interface 3 4 1 1 The Number Pad Editor on page 17 is displayed for the first coordinate Enter the Offset Frequency coordinate in Hz for the new point and press Apply or press Cancel to...

Страница 46: ...icking and selecting Delete Point from the popup menu This can be done without entering the Edit Mask softkey interface as stated in Step 2 Any added edited or deleted points mark the test mask as changed A warning is displayed upon Return to the phase noise plot if a changed mask has not been saved The message states that modifications will be lost if the test set is powered off To save a test ma...

Страница 47: ...ase noise data set grows additional rows appear for even lower limits See 3 3 2 Tables on page 15 for more information about read only tables Integrated phase noise includes phase noise out to 1 MHz Time Constant described in detail in the following section 5 1 4 1 Setting the Time Constant The time constant determines the length of the running average used for f phase noise and Allan deviation co...

Страница 48: ... tables The test set detects spurs caused by its own operation These spurs are referred to as internally generated spurs Internally generated spurs are removed from calculations All spurs listed in the spur table are part of the signals attached to Input or Reference port Every spur s frequency and power is listed regardless of how the phase noise plot is scaled Spurs that do not appear on the plo...

Страница 49: ...A and 5120A 01 perform cross correlation They are able to compute the noise floor and shade the region below the measurement noise floor in gray The 5115A does not perform cross correlation and cannot shade the measurement noise floor region Instead it computes error estimates and presents those estimates using red vertical bars along with each measurement The following can be configured Plot scal...

Страница 50: ...n Table Allan deviation data can be viewed in tabular format by pressing the View Table softkey The table lists all Allan deviation values regardless of how the plot is scaled To access the table with a mouse right click the Allan deviation plot and select View Table from the menu The table provides both the softkey and mouse interfaces to change the τ0 value 5 2 4 Setting Up Allan Deviation Test ...

Страница 51: ... Scale Y Axis then press one of the following Use Shift Up 1 Div and Shift Down 1 Div to shift scroll the data up or down one division on the screen Use Increase Time Div or Decrease Time Div to increase or decrease the values for each division on the plot Use Center Median to center the data s median vertical value 5 3 2 Removing the Linear Trend Phase difference measurements often exhibit a line...

Страница 52: ...ine towards the end of the region Region 2 contains measurements near or on the trend line segment Region 3 holds measurements which approach the trend line segment from above Once the trend has been measured it can be removed from the plotted measurements by pressing the Remove Linear softkey shown in Figure 13 Linear Trend in Phase Difference Measurements Removing the linear trend from this data...

Страница 53: ...iceable in Figure 13 Linear Trend in Phase Difference Measurements can readily be seen The Remove Linear softkey has changed to Don t Remove Linear Pressing it at this time will stop removing the trend from the data and display data set as seen in Figure 13 Linear Trend in Phase Difference Measurements The linear trend can be measured whenever there are at least two phase difference measurements a...

Страница 54: ...updates press the Resume Updates softkey As with all data sets that can be paused the test set continues to collect data while updates are paused and presents the latest data set when they are resumed 5 4 Configuring the Frequency Difference Plot The PNTS can display the frequency difference between the Input and the Reference signals The measurements are plotted in real time each second All measu...

Страница 55: ...requency Counter The PNTS collect data that measures the frequency of the Input signal using the Reference signal as a reference The test set continually computes and displays frequency averages for the Input signal port for the last 1 10 100 and 1000 seconds When set automatically the Reference Frequency value may be displayed as not yet set until data collection begins then the frequency of the ...

Страница 56: ...m precision 5 5 1 Changing the Reference Frequency The frequency used to compute frequency averages when an external reference signal optional on 5120A 01 using the internal reference is used can be set in one of two ways Automatically The test set uses the Reference signal s measured frequency Manually The user specifies a more precise reference frequency The current reference frequency displays ...

Страница 57: ...ing begins The automatic reference frequency is the frequency of the Reference signal in MHz to a precision of one decimal digit at the time collection starts Automatic setting of the reference frequency is the default setting To automatically set the reference frequency 1 From the front panel press Freq Counter see 3 1 1 Navigation on page 12 2 Press Config Freq Counter 3 Press Auto Reference Fre...

Страница 58: ...ference frequency in MHz See 3 4 1 1 The Number Pad Editor on page 17 for help with entering numbers The table of frequencies updates with calculations using the new frequency The instrument retains the manually set reference frequency until a new one is entered or automatic setting is selected The frequency setting persists when the test set is powered off ...

Страница 59: ... the signal cables during operation as this may influence the accuracy of data collection and results Pressing the front panel buttons other than STOP during collection could also influence the measurement Use of a mouse or control of the instrument via Ethernet is recommended for best results if settings need to be changed during collection The action field displays Initializing and then transiti...

Страница 60: ...54 6 Collecting and Viewing Data Locally Note The most recent data is retained on all screens until a new data collection starts or the instrument is powered off ...

Страница 61: ...n the front panel Right click the current plot or table and select Control Print from the menu Note The test set can queue up to 15 print jobs All print jobs will go to the currently selected printer or file system The number of pending print jobs is displayed in the top left corner of screen To cancel pending print jobs 1 Access the Settings page see 4 1 The Settings Screen on page 21 for details...

Страница 62: ... test set is under Local control any function that requires control can be executed using the softkey interface mouse or keyboard To yield Local control of the test set 1 Access the Settings page see 4 1 The Settings Screen on page 21 for details 2 Press Network 3 Press the down arrow softkey until a push button on the row labeled Operations has focus denoted by a white rectangle The softkey inter...

Страница 63: ...e page 59 Retrieve or print any other data set including f Phase Noise Allan Deviation One Second Phase Difference One Second Frequency Difference Frequency Counter Data See 7 2 3 Retrieving Data from Command Port on page 59 and 7 2 4 Printing from the Command Port on page 60 for details Configure Data Sets Pause and resume updates to phase and frequency difference see page 62 and removing the lin...

Страница 64: ...pping Data Collection on page 59 2 The command port outputs a short welcome message and displays a prompt with the test set s IP address All commands described in the following sections are entered at this prompt Many commands produce output before re displaying the prompt 3 To close the command port connection enter quit If there are multiple test sets on your network it may be beneficial to the ...

Страница 65: ...ge 58 When the test set reaches the Collecting state phase difference begins to arrive on any open data port connections see page 67 3 To stop data collection enter stop This is a good time to permit either Local or Remote use by others using the control yield command though control can be yielded at any time see page 58 7 2 3 Retrieving Data from Command Port All the data sets presented by the gr...

Страница 66: ...All phase difference measurements are output with their corresponding x coordinate so the measurement can be related to the linear trend s y intercept For more information about linear trend removal see Chapter 5 Removing the Linear Trend on page 45 Use the show freqdiff command to retrieve the one second frequency difference strip chart data The test set outputs a header showing that frequency di...

Страница 67: ...d print spectplot spectplot spurtable Does not result in a print job that prints the phase noise plot twice Neither does the following print all spectplot The print command is also used to cancel all pending print jobs To cancel print jobs enter print cancel Note The Allan deviation data printed corresponds to the current τ0 value See 7 2 6 4 Setting the Allan Deviation t0 Value on page 63 for inf...

Страница 68: ...e resume command with the same parameter value passed with pause command The show command will now return the current data set and the user interface will plot it 7 2 6 2 Removing the Linear Trend The phase difference cache supports measuring and removal of its linear trend See Chapter 5 Removing the Linear Trend on page 45 for conceptual details You can perform both functions on a command connect...

Страница 69: ...y each time data collection starts enter set referencefreq auto To manually set it to a more precise value provide the frequency in MHz as the last parameter to the set referencefreq command To set it to 5 0000003 MHz enter set referencefreq 5 0000003 Future show fcounter commands return the averages calculated using the new reference frequency The user interface table is also updated immediately ...

Страница 70: ... common to many of the screen shots in this manual is set as follows set title Quartz Oscillator vs Self The test set will return a confirmation message showing what the title has been set to This provides immediate feedback in case the string you provided is truncated because it exceeds the maximum length 7 2 9 Showing the Software Version Version information useful for troubleshooting can be acc...

Страница 71: ...ide a list of valid parameters if arguments are found to be invalid This too can serve as a source of help using a command 7 2 11 Setting Data Port Output Rate The output rate of the data port can be set in samples per second using the set phaserate rate command where the output rate rate can be either 1 10 100 or 1000 The show phaserate command can be used to determine what the current value of p...

Страница 72: ...or yields remote control of the test set help Display help for a command or list all commands history Lists previously entered commands measurelinear Measures linear trend in show phasediff data set pause Pauses updates on phase or frequency difference cache print Prints a plot or table prompt Turns command prompt on or off quit Closes the command connection removelinear Enables Disables phase dif...

Страница 73: ... to 34 characters show adev Returns snapshot of Allan deviation tables show date Returns current date and time in selected format show dateformat Returns selected printout date stamp format show fcounter Returns snapshot of frequency counter table show freqdiff Returns snapshot of frequency difference strip chart show inputs Returns input frequency and amplitude on input signal ports show ipn Retu...

Страница 74: ...ans that a data port connection can be kept open while collection is stopped input or reference signal sources are changed and collection is restarted To retrieve phase difference data remotely 1 Access the Data port For more information see 7 1 Accessing the PNTS Remotely and Exiting the Remote Session on page 58 If you want to store the data in a file tell your Telnet software to capture the dat...

Страница 75: ...meters on a single channel or the single test port Other channels are assumed to behave in the same manner The jitter calculation uses frequency counter s reference frequency 100 second frequency average integrated phase noise with a low limit of 1 mHz and the user supplied DRFI ratio as inputs It computes jitter resulting from frequency error J1 and jitter resulting from random variations J2 and ...

Страница 76: ...ering numbers Both M and N must be positive integers representable as an unsigned 16 bit value These values persist when the test set is powered off 4 Press Enter Reference Freq and enter the frequency counter s reference frequency 5 Press Start and collect data for at least 45 minutes 6 Press Calculate Jitter If a dialog stating that more data must be collected is displayed press Dismiss Dialog w...

Страница 77: ...Reference Frequency on page 63 for details Once the reference frequency has been set it persists until it changed by the user 6 Use the docsis command to calculate jitter The docsis command has two variations they are explained in the example below The command returns the J1 J2 Total Jitter and Overall Result values The user interface reports the same values If the command returns an error message...

Страница 78: ... calibration this signal is attached to Input port on the front panel Data is collected in internal reference mode until the 1000 second frequency average has been computed by the frequency counter The frequency average is then used to calculate the internal oscillators frequencies For calibration purposes the function of the Input port is thus reversed it actually serves as a reference signal use...

Страница 79: ... the Pending Calibration frame When the Pending Calibration frame presents the measured frequencies the test set is ready to store the oscillator calibration values proceed to the next step 6 Press Calibrate to store frequency calibration data Calibration frequencies are calculated and stored The Previous Calibration frame updates to reflect newly calibrated frequencies and time of calibration 8 1...

Страница 80: ...ate internal oscillators frequencies 6 Issue the calibrate command If calibrated frequencies cannot be calculated at the time the calibrate command is issued the 5120A 01 responds with the reason for the failure If the command does not cause a response calibration was successful 7 Use the calinfo command to verify the newly calibrated frequencies ...

Страница 81: ...oo much liquid when cleaning the test set Liquid can enter the test set and damage sensitive electronic components Clean the main chassis with a soft cloth dampened with a mild soap and water solution 9 3 Cleaning the Fan Filter Units that started shipping in March 2009 include a small fan on the rear cover for commonality with the 5125A chassis and to improve cooling The fan filter can be removed...

Страница 82: ...76 9 Maintaining a PNTS ...

Страница 83: ...ted 4 Determine if any input power circuit breakers have been tripped 5 Ensure that your power source is within specification 6 Press Power to turn the instrument on 7 Check that the green LED on the front panel near the Power button is lit If it does not come on and your power source has been thoroughly checked unplug the instrument from its power source and check both fuses mounted in the power ...

Страница 84: ...nals frequency during data collection 4 If the problem persists contact Symmetricom Customer Assistance see page 95 Input Reference ADC clipping error Stopped Collecting The test set did not properly set attenuators to correctly limit input voltage to the range the ADC can measure 1 Check the signal connections on the input and reference ports If they are within operating range cycle power 2 Do no...

Страница 85: ...ck when the test set was powered on It was restored to factory defaults 1 Reconfigure the test set If this problem persists contact Symmetricom Customer Assistance see page 95 Process processname has failed Please cycle power on the test set where processname is one of a2dReader netd or ui One of the applications has failed at a level indicative of a programming error 1 Power cycle the test set If...

Страница 86: ...his procedure Small flat head screwdriver Replacement fuse for a standard IEC 320 power entry module with fuse 250 volt 1 amp time delay 5 x 20 mm fuse T To replace a fuse 1 Disconnect the power cable from the back of the test set 2 Using a small screwdriver open the fuse cover on the back of the test set 3 Replace the old fuses as necessary 4 Close the fuse cover 5 Reconnect the power cable to th...

Страница 87: ... been designed and manufactured to the following specifications Safety EN61010 1 2001 Safety Requirements for Electrical Equipment for Measurement Control and Laboratory Use Part 1 General Requirements EMC EN61326 1 2001 Electrical Requirements for Electrical Equipment for Measurement Control and Laboratory Use Part 1 General Requirements EN 55011 Class A Radiated Emissions I hereby declare that t...

Страница 88: ... delay 5 x 20 mm Signal Inputs Frequency 1 30 MHz Impedance 50 Ω 5 Ω Input level 3 17dBm Connectors Input Two TNC supplied with BNC adapters Output Two USB 1 1 Type A Network RJ 45 10 or 100 baseT Battery Lithium on single board computer printed circuit board 3V type BR2032 Dispose of the battery in accordance with local regulations Table A 2 f Noise Floor Specifications1 Input Signal 5115A 5120A ...

Страница 89: ...147 dBc Hz 100 000 Hz offset 147 dBc Hz 1 Hz offset 137 dBc Hz 10 Hz offset 150 dBc Hz 100 Hz offset 160 dBc Hz 1 000 Hz offset 170 dBc Hz 10 000 Hz offset 172 dBc Hz 100 000 Hz offset 172 dBc Hz 30 MHz 1 Hz offset 127 dBc Hz 10 Hz offset 137 dBc Hz 100 Hz offset 145 dBc Hz 1 000 Hz offset 146 dBc Hz 10 000 Hz offset 146 dBc Hz 100 000 Hz offset 147 dBc Hz 1 Hz offset 127 dBc Hz 10 Hz offset 138 d...

Страница 90: ...er Voltage Category II for transient over voltages per EN 61010 1EN 61326 1 Class A Equipment suitable for continuous operation Table A 5 lists the environmental specifications for the 5120A 5120A 01 and 5115A Table A 5 Environment Specifications Item Temperature Relative Humidity Altitude In Use 15 C to 40 C 5 to 95 non condensing 3 000 meters 9 843 feet Storage 25 C to 70 C 5 to 95 non condensin...

Страница 91: ...he 5120A 5120A 01 and 5115A Figure A 1 shows the dimensions of the 5120A 5120A 01 and 5115A Figure A 1 5120A 5120A 01 and 5115A dimensions Table A 6 Physical Specifications Item Specification Size 33 8 cm x 17 4 cm x 43 7 cm 13 31 x 6 84 x 17 21 Weight 5120A Approximately 9 1 kg 20 pounds 5115A Approximately 8 4 kg 18 5 pounds ...

Страница 92: ...86 Appendix A Specifications ...

Страница 93: ...ws the analog approach to source phase noise measurements Figure B 1 Analog source phase noise measurements require both calibration and a phase lock loop The digital method samples the RF waveforms rather than the output of the phase detector The phase detection is performed by digital signal processing which results in several advantages the phase detector has 2Nπ range eliminating the need for ...

Страница 94: ...he phase difference between the input signal and the synthesized LO is computed using the arctangent function as shown in Figure B 3 Figure B 3 A local oscillator synthesized from the internal clock down converts the input to base band where the samples are used to compute the phase difference between the LO and the input This step is the heart of the direct digital technique It is not necessary t...

Страница 95: ...ce The computation to this point is shown in Figure B 4 However if the Power Spectral Density PSD of the phase were computed from the DFT the broadband noise floor would be limited by the white noise of the ADCs at a level of 150 dBc Hz or worse with today s best converters This is the price that has been paid for the convenience of operation without a PLL or need for calibration and would make th...

Страница 96: ...tical measurement systems as shown in Figure B 7 The ADC noise and the internal reference oscillator noise are highly uncorrelated and average down allowing improvement of the broadband noise floor to fall below 170 dBc Hz with only one instrument input Figure B 7 5120A 01 with internal references The PSD is computed as the cross spectrum of the DFTs from two identical processing front ends Sample...

Страница 97: ... frequency portions of the spectrum Data for each lower frequency span is obtained by low pass anitalias filtering the higher sample rate data then decimating it appropriately B 3 Measurement Methodology All phase noise measurements are referenced to the frequency of the Input port This has an effect on how you connect the instrument for different measurements One example is listed below Example Y...

Страница 98: ...92 Appendix B Theory of Operation ...

Страница 99: ...P Dynamic Host Configuration Protocol DOCSIS Data Over Cable Service Interface Specification DRFI Downstream RF Interface DSP Digital Signal Processor DTI DOCSIS Timing Interface DUT device under test EQAM Edge Quadrature Amplitude Modulation ESD electrostatic discharge FTP File Transfer Protocol IPP Internet Printing Protocol NEQBW Noise equivalent bandwidth PCL Printer Control Language SSB singl...

Страница 100: ...94 ...

Страница 101: ...ttp www symmetricom com support index aspx or by calling one of the above Customer Assistance Center numbers When calling the worldwide or USA based number select Option 1 at the first prompt Telecom Solutions Division customers should then select Option 1 Timing Test and Measurement Division customers should then select Option 2 Technical Support personnel are available by phone 24 hours a day 7 ...

Страница 102: ...96 ...

Страница 103: ...lly 53 starting and stopping remotely 59 date setting locally 22 setting remotely 65 Default settings restoring locally 29 settings restoring remotely 65 DHCP restarting client 25 using 23 DOCSIS overview 69 testing locally 70 testing remotely 71 E EC Declaration of Conformity 81 electrical specifications 82 environmental specifications 84 error messages troubleshooting 78 Ethernet see also networ...

Страница 104: ...ng print jobs locally 54 cancelling print jobs remotely 61 configuring remotely 61 formats 26 printing locally 54 printing remotely 60 supported printers 26 to files 28 to network printer 29 to USB printer 26 R reference frequency see frequency counter remote commands viewing help for 64 viewing list of 64 replacing a fuse 80 Restoring factory default settings locally 29 factory default settings r...

Страница 105: ...etting locally 14 setting remotely 64 troubleshooting error messages 78 troubleshooting procedures 77 turning on the test set 9 typographic conventions 3 U unpacking a test set 8 Upgrading software 30 USB ports connection to 7 USB printer printing to 26 user specified title 14 V viewing data remotely 67 help for remote commands 64 list of remote commands 64 Y yielding control see control ...

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