Using Power Leveling to Control Test Port Output Power
Contents
1. measurement measurements were made using 201 trace points and 128 averaging Figure 5 shows an Sy measurement versus frequency before Power Domain was enabled step 5 of Table 3 The marker marks the frequency of interest interest Figure 6 shows the 85 measurement sweeping in power at Finterest and identifying the 1 dB compression point at that frequency steps 6 9 of Table 3 1 MAG MMARKER 1i RE 2 0 cB x 52 074 i 10 2 c 5 4968 V 6 4968 cB o e c i J A E M Loi i L EE m S START stop 329 JUL 58 Z 045820008 GHz 11 220800000 GHz 11 34 42 Figure 5 An Sg measurement versus frequency with the marker placed at 50 07 GHz and Pi set at 15 dBm before Power Domain was enabled REI 0 0 en top ea fd To o dd TEES 10 0 cB 5 4998 cB 6 4974 dB 23 o 2 c rtt H H M M pe m SS Ee ee amp i START FREQUEN stop 30 Ju sq ERG cfm 50 07 4505000 Gu 4 0 com EE 35 0 dBm 50 074525000 GHz 15 0 dBm 14 37 45 E Figure 6a Figure 6b Figure 6 a An Sg measurement versus power at the frequency specified by the marker in Figure 5 Note the default start and stop stimulus values b By increas ing the s2. Ls log MAG MARKER i Le Me log MAG IRKER ret 5 0 dB 3 8834 2 2 cB 3 8934 5 0 a 38 198 cj 1 2 de 0 9565 18 199 cB oes co 3 z c c A E i E H H m M as wer TI TLIIg START STOP 32 JUL SH START stop 30 Ju B 04520000 GHz 110 00 CO0000 GHz 11 23 49 GrgAsnacooo He 1 2 020000000 Ge Beariae Lingas Figure 4a Figure 4b m log MAG 1 ree 2 0 ds 13 239 GHz 13 239 1 0 de 1 0255 dB 13 637 cH 1 0055 dB fe c A 4 x START stop aa Ju 88 START stop 32 Ju Sq B 245200000 GHz 110 000000000 GHz 11 14 17 B 245m00000 GHz 110 0 9000000 GHz 11 22 43 Figure 4c Figure 4d Figure 4 a At 3 89 GHz the 1 dB compression point happens at Pin 11 dBm and b Sg measures at 18 20 dB c At 13 24 GHz the 1 dB compression point happens at P 6 dBm and d Sg measures at 13 64 dB 10 Measurements in the power domain In the frequency domain measurements are made at one test port power level while sweeping in frequency In the power domain measurements are made at one frequency point while sweeping in power Similar to frequen cy domain measurements but sweeping in power measurements such as gain and gain compression can be easily accomplished without performing a power calibration each time Befor
3. lt lt Less Done Used oO E Probe Def oO o EE EET E o Clear All El x Raw To File 0 S To File S From File 19 References 1 On Wafer Measurements Using the HP 8510 Network Analyzer and Cascade Microtech Wafer Probes HP Product Note 8510 6 literature number 5954 1579 2 Controlling Test Port Output Power Flatness HP Product Note 8510 16 literature number 5091 0467E 3 WinCal Software User Guide Cascade Microtech U HEWLETT PACKARD For more information about Hewlett Packard test and measure ment products applications services and for a current sales office listing visit our web site http www hp com go tmdir You can also contact one of the following centers and ask for a test and measurement sales representative United States Hewlett Packard Company Test and Measurement Call Center P O Box 4026 Englewood CO 80155 4026 1 800 452 4844 Canada Hewlett Packard Canada Ltd 5150 Spectrum Way Mississauga Ontario LAW 5G1 905 206 4725 Europe Hewlett Packard European Marketing Centre P O Box 999 1180 AZ Amstelveen The Netherlands 81 20 547 9900 Japan Hewlett Packard Japan Ltd Measurement Assistance Center 9 1 Takakura Cho Hachioji Shi Tokyo 192 Japan Tel 81 426 56 7832 Fax 81 426 56 7840 Latin America Hewlett Packard Latin American Region Headquarters 5200 Blue Lagoon Drive 9th Floor Miami Florida 33126 U S A
4. This literature was published years prior to the establishment of Agilent Technologies as a company independent from Hewlett Packard and describes products or services now available through Agilent It may also refer to products services no longer supported by Agilent We regret any inconvenience caused by obsolete information For the latest information on Agilent s test and measurement products go to www agilent com find products rg Agilent Technologies Or in the U S call Agilent Technologies at 1 800 452 4844 8am 8pm EST 717 Innovating the HP Way HEWLETT Ka 8510XF Network Analyzer CA PACKARD Using Power Leveling to Control Test Port Output Power Product Note 8510XF 1 Table of Contents Introduction 24A evu4 Rx Ved d se ebb s eres SC heb Rex Power leveling amp usse ee be Pe ede You X Wee RE PY Power leveling operation ss rrsris raskir piteni eee eee Power control ss ese eaa e ae as Measurements in the frequency domain naaa aaa aaan Measurements in the power domain 00000005 Appendix A Test port cable loss compensation Appendix B Wafer probing environment considerations Introduction Designers and manufacturers of active devices and components often need to control the power level at the input port of their power sensitive devices but find it difficult to overcome insertion losses created by compo nents in the measurement path between the RF synthesizer
5. averaging port power Perform a 1 port calibration at a test port for example at test port 1 Save the calibration and turn it on 2 Connect the test port cable and then the probe to the test port that is connect the HP 11500J test port cable to test port 1 and then connect in the probe as shown in Figure B2 3 Using WinCal perform Probe Test With WinCal running on a desktop PC controlling the HP 8510XF VNA system via a GP IB cable e Start WinCal This will bring up a screen similar to the one shown in Figure B3 Select Probe Test from the Tools menu This will bring up a screen similar to the one shown in Figure B4 For this example select Port 1 under Method Measure the Open Short and Load standards on the ISS Click Compute and it will display results similar to Figure B1 4 Power slope calculation The S4 trace shown in Figure B1 can be used to approximate the value for power slope Figure B2 Test port cable and probe connection l PCrequirements and detailed information on WinCal can be found in Cascade Microtech s WinCal Software User Guide 18 8 WinCal File Config Calibration Tools No calibration done yet WinCal 2 23 ISS Positions Help Figure B3 WinCal Probe Test Method Load port 1 Load port 2 Short part 1 Short port 2 Figure B4 Probe Test dialog box bd Close Help Setup
6. 305 267 4245 4220 Australia New Zealand Hewlett Packard Australia Ltd 31 41 Joseph Street Blackburn Victoria 3130 Australia 1 800 629 485 Asia Pacific Hewlett Packard Asia Pacific Ltd 19 F Cityplaza One 1111 King s Road Taikoo Shing Hong Kong tel 852 2599 7777 fax 852 2506 9285 Data Subject to Change Copyright 1999 Hewlett Packard Company Printed in U S A 7 99 5968 5270E 20
7. SOFTKEYS J Power leveling operation The second level of this calibration process is the conversion loss frequen cy response calibration performed to gather the correction factors to counteract the frequency related variations caused by the RF to IF conver sion loss of the coupler and mixer This calibration procedure can be per formed as part of an annual maintenance to be conducted either on site or at the local HP service center by HP customer service engineers with the proper power level flatness kit and equipment This procedure takes approximately 3 to 4 hours The correction factors obtained during the above calibrations are valid only for the system components that are installed at the time of calibration If any component in the system is replaced both calibrations must be repeat ed These components include the HP 8510XF millimeter wave controller the left and right test head modules and the RF and LO synthesizers There are four different RF leveling functions available in the HP 8510XF measurement system These functions can be found in the RF POWER CONFIG menu This menu can be located by pressing the following keys SYSTEM MORE RF POWER CONFIG The four different RF leveling functions are e RF LEVEL SYSTEM RF power is leveled at the test ports and is entirely controlled by the HP 8510XF system This is also the normal operating mode The HP 8510XF system is set in this mode at the time the system leave
8. Set up the analyzer for an S5 measurement CAL Perform a thru calibration to eliminate the fre CAL quency response errors of the path in the mea CALIBRATE RESPONSE surement Be sure to include any adapters that THRU are part of the measurement in the thru DONE RESPONSE calibration CAL SET 1 Save the calibration in Cal Set 1 1 Ifa calibration is being performed or a previously stored Cal Set is being used the power domain frequency of measurement must be a point in the original frequency domain calibration Otherwise calibration will be automatically turned off 11 HP 8510C Keystrokes Description continued 5 Connect amplifier DUT and measure gain Gain is displayed here as S5 versus frequency 6 Set up for a power domain measurement MARKER rotate knob Place a marker at the frequency point of interest Finterest 1 DOMAIN POWER Select power domain 7 Adjust display for 1 dB compression measurement MARKER Place a marker on the left side of the display REF VALUE MARKER Set the marker value to become the new reference value SCALE 1 x1 Set the scale to 1 dB per division for easy viewing 8 To change start and stop test port power levels START Psi x1 Set up the start and stop test port power levels STOP Psi x1 Set Part below the amplifier s compression level 9 Increase P to find the 1 dB gain compression point STOP u
9. compression point for the specified frequency point can be calculated by adding Pcompression compression 1 the test port power level identified when the 1 dB gain compression point was found Example of the frequency domain measurement Figures 3 and 4 illustrate an example of the frequency domain measure ment covered in Table 2 The device under test was a broadband amplifier The measurements were made using 201 trace points and 128 averaging Figure 3 shows the measurement of absolute power at the DUT output port versus frequency step 6 of Table 2 Figure 4 shows that the 1 dB compression point is different for each frequency steps 7 11 of Table 2 For comparison the measurements shown were made at two dif ferent frequency points one at 3 89 GHz and the other at 13 24 GHz As the frequency increases it typically takes more power to reach the 1 dB compression point log MAG gt i log MAG E 2 0 dB E a cB 10 0 dB 10 0 B fe c a D i1X STI ART STOP 3 JUL S8 B Z45022 GHz 110 0000002000 GHz 10 16 53 Figure 3 Measurement of absolute power at the DUT output port versus frequency The top trace shows the Sj measurements of the DUT The bottom trace shows absolute power the equivalent of P added to S5 Pj was set at 15 dBm
10. output and the test device Accurate power control in stimulus response measurement systems is important for several reasons For small signal measurements it is necessary to ensure that the device being measured is operating in its linear region It is also desirable to maintain as high a power level as possi ble to increase the dynamic range of the measurement In some cases it may be necessary to make a measurement at a specified power level or to measure the device parameters as a function of stimulus power Power leveling which uses a feedback loop to set the power incident from the test port along with a power calibration of the stimulus system are used to provide accurate control Without power leveling power variation over a broad frequency sweep could easily be more than 10 dB depending on the power setting The HP 8510XF is the first ultra broadband vector network analyzer VNA system capable of implementing power leveling to set and control the power level at the test ports over the 0 045 to 110 GHz frequency range without requiring a power calibration for each measure ment This note reviews the operational considerations for power leveling with the HP 8510XF 1 Throughout this document input port refers to the point where the test device is connected in other words the input port of the device under test DUT Test port refers to either port 1 or port 2 of the HP 8510XF test head module Power leveling Power l
11. the display to show the opposite function If COUPLE PORTS is pressed the Port 1 power level setting and power slope setting are applied to Port 2 If UNCOUPLE PORTS is pressed the two ports have independent power level settings and power slope settings and the following softkeys will be displayed PORT2 POWER j followed by a number specifies a power level setting for Port 2 in dBm PORT2 SLOPE ON and PORT2 SLOPE OFF j used to enable and disable power slope for Port 2 PORT2 SLOPE ON followed by a number specifies the power slope setting for Port 2 in dB GHz The current port power level is used as the power at the first frequency of the sweep and slope is then applied as frequency increases Power slope has no effect on CW measurements NOTE Since the last two softkeys PORT2 POWER and PORT2 SLOPE ON OFF control the power level from Port 2 they are displayed only if the ports are uncoupled While using the system in this mode RF LEVEL SYSTEM the user may encounter the following error messages RF Unleveled displayed if test port power becomes unleveled This indicates that the specified test port power is too high for the HP 8510XF leveling loop to maintain leveled power over the frequency span This error message should disappear as test port power is reduced and leveling re established e No IF Found displayed if the IF is not found or too low Check to make sure that the RF sour
12. ce has an output signal and is properly connected to the millimeter wave controller For more information please refer to the HP 8510C Service Manual under the Running Error Messages section e IF Overload displayed if the IF is overloaded Reducing the test port power will remove this message Measurements in the frequency domain One of the benefits of the power leveling capability of the HP 8510XF mea surement system is the ability to perform power measurements without doing a power calibration each time Since the input power level to the device under test is kept constant the HP 8510XF system can carry out power measurements such as gain gain compression and absolute power on active devices simply at the touch of a few keystrokes Table 2 provides step by step instructions for setting up and performing measurements on an amplifier Included are measurements of gain gain compression and absolute power Table 2 Gain gain compression and absolute power measurements of an amplifier in the frequency domain HP 8510C Keystrokes Description 1 Set up the HP 8510C PRESET Return all instruments to a known state START Fs G n Set up the start and stop frequencies STOP Fstop G n STIMULUS MENU Select the number of analyzer trace points NUMBER of POINTS 7 RESPONSE MENU Set averaging as desired AVERAGING ON RESTART 1x1 2 Verify that power leveling is enabled SYSTEM MORE Sel
13. e beginning power domain measurements the system must be cali brated in the frequency range of choice This calibration is included in Table 3 along with step by step instructions for setting up and performing measurements of an amplifier It is recommended that the chosen frequen cy range provides frequency steps of a convenient size This allows the measurement frequencies to be easily recalled later For example setting start frequency to 1 GHz and stop frequency to 101 GHz with the number of points set to 101 gives measurement frequencies in 1 GHz increments Table 3 Gain and gain compression measurements of an amplifier in the power domain HP 8510C Keystrokes Description 1 Set up the HP 8510C PRESET Return all instruments to a known state START Fstart G n Set up the start and stop frequencies STOP Fstop G n STIMULUS MENU Select the number of analyzer trace points NUMBER of POINTS 7 RESPONSE MENU Set averaging as desired AVERAGING ON RESTART x1 2 Verify that power leveling is enabled SYSTEM MORE RF POWER Select RF system leveling CONFIG RF LEVEL SYSTEM MORE DETECT UNL SMART Select smart leveling detection 3 Set test port port 1 power level STIMULUS MENU POWER MENU Set test port 1 power Pin below the amplifier s PORT1 POWER P x1 device under test DUT compression level 4 Perform a thru measurement calibration S31
14. ect RF system leveling RF POWER CONFIG RF LEVEL SYSTEM MORE DETECT UNL SMART Select smart leveling detection 3 Set test port port 1 power level STIMULUS MENU Set test port 1 power P below the amplifier s POWER MENU device under test DUT compression level PORT POWER P x1 4 Perform a thru measurement calibration S51 Set up the analyzer for an 5 measurement CAL Perform a thru calibration to eliminate the fre CAL quency response errors of the path in the mea CALIBRATE RESPONSE surement Be sure to include any adapters that THRU are part of the measurement in the thru calibra DONE RESPONSE tion CAL SET 1 Save the calibration in Cal Set 1 Considerations If test port cables are used to connect the amplifier see Appendix A for test port cable loss compensation Since leveled power is provided at the test ports power delivered to the input port of the DUT may not be leveled due to the insertion loss of the test port cable HP 8510C Keystrokes Description continued See Appendix B for wafer probing environments 5 Connect amplifier DUT and measure gain Gain is displayed here as S5 versus frequency 6 Measure absolute power at the DUT output port RESPONSE MENU Display absolute power at the DUT output port MORE versus frequency by entering a magnitude offset MAGNITUDE OFFSET P x1 equivalent to the test port 1 p
15. ed From Hewlett Packard e HP 8510XF 0 045 to 110 GHz VNA system e HP 11500J 1 0 mm test port cable male to female 16 cm in length e HP 85059A DC to 110 GHz calibration kit From Cascade Microtech e Summit 9100 manual probe station e ACP110L GSG DC to 110 GHz low loss probe 150 um pitch ground signal ground G S G configuration e P N 104 783 W band Impedance Standard Substrate ISS in G S G configuration usable through 110 GHz WinCal automated calibration software for vector network analyzers 1 Cascade Microtech is an HP Channel Partner and can be reached at Cascade Microtech Inc 2430 NW 206th Avenue Beaverton Oregon 97006 General 1 800 854 8400 Sales 1 800 550 3279 Support 1 800 626 9395 www cmicro com 2 Different lengths of 1 0mm test port cables are also applicable There are three lengths available HP 11500J 16cm HP 11500K 20cm and HP 11500L 24cm 3 A manual probing station was used in this example Other probing stations are also applicable such as semiautomatic probe stations 16 The following sequence of events took place 1 A l port coaxial calibration was performed at the test port of the HP 8510 VNA 2 The test port cable and the probe were connected to the same test port that was just calibrated 3 Using WinCal and with the test port calibration active on the VNA the probe test was performed 4 The result was an S parameter graph of the cable probe see Figu
16. eveling capability is standard with the HP 8510XF system With power leveling power levels at the test ports are controlled with a typical accuracy of 1 0 dB and a control range greater than 20 dB over the entire frequency range 0 045 to 110 GHz The system comes with power level ing ready Figure 1 shows test port power versus frequency with power lev eling turned on in an HP 8510XF measurement system Leveled Power Port 1 Leveled Power Port 2 _ 4 6 7 E 7 a 8 m 8 9 9 o 10 Z 10 o amp al c2 zu 13 a 13 Co EE a a 2 2 7 2 obs P 5 22 7 77 bp d Z Or 6 DAD Z 3 ur eu io Qut BoD Koo Uy Bo Vig Im dp I S ra e ig To Eg te up TO RR NAA Z Frequency GHz Frequency GHz Figure 1 Leveled test port output power versus frequency with power set to 10 dBm at the test ports and frequency coverage from 0 045 to 110 GHz Figure 2 shows the HP 8510XF leveling loop Power from the RF source is first sampled by the directional coupler The coupler output is down con verted by a mixer to the IF frequency 20MHz which is then amplified using programmable gain steps filtered and scaled prior to detection After the IF signal is converted to a DC voltage by the detector the detec tor DC output is applied to a multiplying DAC increasing the power setting resolution This signal is passed through the blanking switch before being compared to the reference voltage T
17. he output of this comparison differ ence signal drives an integrator which in turn drives the power modula tor forcing the difference to zero Power adjustment is done by changing the reference voltage setting HP 8510XF NETWORK ANALYZER Blank Strobe gt mm Wave Controller Loop Reference Voltage i RF Out gt lt to Test Port Modulator HP E7350A compentr cdr Rev 2 10 20 97 Figure 2 HP 8510XF leveling loop To provide accurate power control a two level calibration process is used to characterize the frequency response and the absolute gain step values of the system These two levels are designed to counteract two different sources of error 1 imprecision in the step attenuators a programmable gain calibration and 2 frequency related variations in coupler and mixer performance a frequency response calibration Both procedures are per formed on each system at Hewlett Packard before it leaves the factory The first level of this calibration process is the detector gain programma ble gain calibration performed to collect the correction factors of the step attenuators in the programmable gain circuit This calibration procedure can be performed anytime by the user it takes approximately two min utes For measurements in which absolute power levels are critical per form this calibration before every measurement calib
18. ing a change in frequency e DETECT UNL NEVER the HP 8510C does not poll for errors during any sweep 1 The front panel hardkey names are enclosed in brackets HARDKEYS The softkey names are italicized and enclosed in braces SOFTKEYS J 6 Power control Once power leveling is enabled RF LEVEL SYSTEM selected the HP 8510XF leveling loop will control the RF source the millimeter wave controller and the test head modules to provide the user requested test port power The test port power functions described below can be found by pressing the following keys STIMULUS MENU POWER MENU NOTE These port power functions are valid only when the RF LEVEL SYSTEM function is selected e PORT1 POWER j tollowed by a number this specifies a power level setting for Port 1 in dBm If the ports are coupled this setting also applies to Port 2 PORTI SLOPE ON and PORT1 SLOPE OFF j used to enable and disable power slope for Port 1 PORT1 SLOPE ON followed by a number specifies the power slope setting for Port 1 in dB GHz The current port power level is used as the power at the first frequency of the sweep and slope is then applied as frequency increases Power slope has no effect on CW measurements If the ports are coupled this setting also applies to Port 2 COUPLE PORTS or UNCOUPLE PORTS j this softkey toggles between the two labels Pressing this softkey selects the displayed function but changes
19. is system Since leveled power is provided at the test ports of the HP 8510XF system test port cables and probes that are used to connect between the test port and the wafer under test will reduce the power delivered to the wafer This reduction in power is mainly due to the insertion loss of the test port cable and the probe This appendix describes the basic steps one can implement to compensate this loss and deliver leveled power at the probe tip For information relating to on wafer measurements in particular on wafer cali bration see HP Product Note 8510 6 or contact Cascade Microtech By characterizing the insertion loss of the test port cable and the probe together over frequency power slope can be used in conjunction with this data to compensate the loss resulting in leveled power at the wafer Since there are no power sensors for on wafer measurements at this time the steps described below can be used to estimate power at the probes for all practical purposes by taking advantage of the known test port refer ence plane To characterize the combined insertion loss of a test port cable and a probe cable probe it is necessary to follow a two step process Step 1 is to perform a 1 port coaxial calibration at the test port and step 2 is to perform a probe test at the tip of the probe Probe Test is a feature of Cascade Microtech s WinCal software Example In this example the following equipment was us
20. is typically linear with frequency as shown in Figure A1 a best fit line can be used to estimate the slope of the line The slope of the line in Figure Al is approximately 3 dB 110 GHz equivalent to 0 027 dB GHz To compensate for the insertion loss of the cable shown in Figure Al the power slope value would be 0 027 dB GHz To enable power slope follow this key sequence STIMULUS MENU POWER MENU SLOPE ON power slope value x1 In this case power slope value would be 0 027 Using the technique described above the approximated insertion loss of a test port cable can be corrected by applying power slope resulting in approximated leveled power at the end of the test port cable This way power delivered to the input port of the DUT is approximately leveled across frequency 1 As stated above in the power control section power slope has no effect on CW measurements not applicable Thus this is valid in frequency domain not power domain 15 Appendix B Wafer probing environment considerations On wafer S parameter measurements at frequencies up to 110 GHz can be made using the HP 8510XF VNA system and Cascade Microtech or other compatible wafer probers Wafer probing allows immediate evaluation for device characterization and selection before dicing the wafer and packag ing The ability to calibrate on wafer and make real time error corrected measurements with the HP 8510XF are the principle advantages of th
21. ngth gt log MAG MARKER i RB a a cB E 45 0 MHz S 2 0 a 2 V_ 2 6445 cB P E pas START STOP g3 AUG S Q 0430000010 GHz 110 000000000 GHz 41 49 17 Figure A1 Insertion loss versus frequency of a typical HP 11500J 1 0 mm test port cable 14 Figure A2 shows output power versus frequency at the end of the test port cable as connected to the test port of the HP 8510XF system The power setting was 10 dBm Since power at the test port is leveled the slope shown in Figure A2 is mainly due to the insertion loss of the test port cable Notice that the trace resembles that of Figure A1 By approximating the trace as a straight line the insertion loss of the cable can be compen sated by applying power slope End of test port cable Port 1 Power End of test port cable Port 2 Power Output Power dBm 2 LIB LL S a x 201 oO zd a 124 5 13 0 0 gt E 3 P gt 2 9 pa gE 14 E NE ORC PE LM DEO NO Zo RC O OD O 450575 2 0 Z d Dap So do DH 2o gt 4 amp D BOOSIE gs em p am ptg o Tomo 4o Vy aae rtp eoo Cg Big Ceo oY Frequency GHz Frequency GHz Figure A2 Output power at the end of the test port cable versus frequency Power was set at 10 dBm The test port cable used was an HP 11500J Power slope calculation Since the insertion loss of cables
22. ower level during the thru calibration P This value can also be calcu lated for any frequency measurement point by adding Pj to So 31 Pou Pin Pout S21xPin 7 Set up 1 dB compression measurement RESPONSE MENU Return the display to show gain S5 by removing MORE magnitude offset MAGNITUDE OFFSET 0 x1 8 Adjust display REF VALUE 0 x1 Set the reference value to 0 and the scale to 1 dB SCALE 1 x1 per division for easy viewing 9 Normalize trace DISPLAY DATA AND MEMORIES By normalizing the measurement the first DISPLAY MEMORY frequency point to drop by 1 dB will be easy to MATH identify 10 Increase power to find the 1 dB gain compression point STIMULUS MENU Increase the test port power 1 dB ata time until POWER MENU one measurement point visibly drops If needed PORT1 POWER use up arrow use the knob to adjust the test port power until a rotate knob 1 dB drop has occurred and note the test port power level Pcompression MARKER rotate knob Measure the frequency by using the knob to place a marker at the 1 dB point 11 Measure gain at the 1 dB compression point DISPLAY DATA AND MEMORIES Display gain S versus frequency The marker DISPLAY DATA will indicate the amplifier s gain at the 1 dB AUTO compression point for that frequency 12 Calculate absolute power at the 1 dB compression point Absolute power at the 1 dB
23. ration If absolute power levels are not important perform this calibration infrequently on a monthly basis for example Table 1 outlines this calibration procedure Table 1 Procedure for Detector Gain Calibration HP 8510C Keystrokes Description SYSTEM MORE Bring up the reset detector gain calibration menu RF POWER CONFIG MORE RESET DET GAIN CAL Considerations The detector gain calibration process causes some settings to change and these are not restored to their original conditions afterward Therefore after the calibration the system needs to be returned to a known state The first two selections below are included as a convenience and as a reminder of the need to save the present settings before running the calibration Select one of the following RUN CAL USER PRST Runs the detector gain calibration routine and is followed by a user preset RUN CAL FACT PRST Runs the detector gain calibration routine and is followed by a factory preset RUN CAL NO PRESET Runs the detector gain calibration routine and is not followed by a preset system settings that are altered by the calibration routine will not be restored to their original conditions afterward CANCEL Exitthe menu without running the calibration routine and return to the previous menu 1 The front panel hardkey names are enclosed in brackets HARDKEYS The softkey names are italicized and enclosed in braces
24. re B1 The trace labeled S5 in Figure B1 shows the insertion loss versus fre quency of a typical HP 11500J test port cable and a typical ACP110L GSG probe together S shows the reflection measurement at the test port and S shows the reflection measurement of the ACP110L GSG probe tip Figure B1 was generated using Cascade s WinCal calibration software Table B1 outlines the steps needed to generate Figure Bl Looking at the trace in Figure Bl the slope of the line can be estimated using straight line approximation The value of the slope can then be applied in power slope to compensate for the insertion loss in the path between the test port and the wafer Refer to Appendix A for power slope calculation 4 Probe Test Port 2 E m Ea File View Help ACP GSG 150 21 dB m e 4 to GS 03 24 1999 11 42 45 C opmm 9 7 F L zhott z48pH L tum 170pH S2lmmx 375dB Sllmm 1305dB S22mm 896dB Figure B1 S9 shows the total insertion loss versus frequency of a typical HP 11500J test port cable and a typical ACP110L GSG probe from Cascade Microtech as measured and computed using Cascade s Probe Test feature in their WinCal calibration software 17 Table B1 Procedure to characterize a test port cable and a probe together Description 1 Coaxial calibration at the test port of the VNA Using the front panel of the HP 8510 Set all desired settings start and stop frequencies number of points
25. s the factory RF LEVEL INTERNAL RF power is leveled at the output port of the RF source The RF source HP 83651B performs its own leveling using an internal detector For proper operation of this mode the connection between the ALC output of the millimeter wave controller and the ALC input of the RF source must be removed To return to normal operation this connection must be restored RF LEVEL EXTERNAL j the RF source performs its own leveling using an external detector RF LEVEL LEVELING OFF j the RF source is set to the unleveled mode NOTE The last three RF leveling functions are not recommended for nor mal operation of the HP 8510XF They are provided as a convenience for use in applications where different methods of RF leveling are desired With power leveling enabled RF LEVEL SYSTEM selected there are four functions available to detect an unleveled condition for more infor mation refer to the HP 8510XF system manual These functions can be found by pressing the following keys SYSTEM MORE RF POWER CONFIG MORE These functions are e DETECT UNL ALWAYS the HP 8510C polls for errors during every sweep e DETECT UNL SMART the HP 8510C polls for errors during the first sweep following a change in frequency and thereafter only if an error was detected during the first sweep This is the default mode DETECT UNL ONCE the HP 8510C polls for errors only during the first sweep follow
26. se up arrow Increase the stop test port power level 1 dB ata rotate knob time until the right half of the measurement trace visibly drops Then use the knob to adjust the power until a 1 dB drop has occurred and note the test port power level P compression for this frequency point 10 To measure another frequency point DOMAIN POWER Use these keys to select the next fre Select NEXT PT HIGH quency point of interest either higher or Or NEXT PT LOW lower and adjust Pstop as necessary 1 If multiple markers are ON the active marker is the one that will be used for the power domain frequency of measurement 2 In the HP 8510XF system the factory preset default settings for power domain measurements are as follows e Start 35 dBm Stop 15 dBm 3 In the power domain the stimulus keys START STOP CENTER SPAN refer to power and not frequency Since the sweeps are done in power the softkey PORTI POWER under STIMULUS MENU POWER MENU has no effect in this mode 4 Ifa calibration is being performed or a previously stored Cal Set is being used the power domain frequency of measurement must be a point in the original frequency domain calibration Otherwise calibration will be automatically turned off 12 Example of the power domain Figures 5 and 6 illustrate an example of the power domain measurement covered in Table 3 The device under test was a broadband amplifier The
27. top stimulus value the 1 dB compression point at this frequency is found to be at 3 415 dBm 13 Appendix A Test port cable loss compensation Since leveled power is provided at the test ports of the HP 8510XF system test port cables that are used to connect between the test port and the input port of the device under test DUT will reduce the power delivered to the input port of the DUT This reduction in power is due to the inser tion loss of the test port cable This section describes the basic steps one can implement to compensate this loss and deliver leveled power at the end of the test port cable If the insertion loss of the test port cable is characterized over frequency this data can be used in conjunction with power slope to compensate cable loss resulting in leveled power at the end of the test port cable Power slope of the HP 8510XF was covered above in the power control section Example In this example the following sequence of events took place 1 A response thru calibration was performed on the HP 8510 VNA 2 Insertion loss 85 of a test port cable was characterized see Figure A1 In this case the test port cable is the DUT 3 Power vs frequency at the end of the test port cable was examined see Figure A2 4 The power slope value was calculated and applied The test port cable used in this example was an HP 11500J a 1 0 mm test port cable with male and female connectors and 16 cm in le
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