RL-875 MICROWAVE TEST FIXTURE CHARACTERIZATION DE-EMBEDDING TECHNIQUES MANUAL BY RHONDA FRANKLIN in Fulfillment of DIRECTED STUDY REQUIREMENTS for Winter 1990 DR. P.B. KATEHI RL-875 = RL-875

CONTENTS PREFACE INTRODUCTION i 1 SECTION I: A. B. C GENERAL INFORMATION EQUIPMENT LIST PROCEDURES: GENERAL OUTLINE LOADING CAL SETS ONTO THE HP 8510 NETWORK ANALYZER SECTION II: CALIBRATION TECHNIQUES A. 7mm CALIBRATION OF THE HP8510 NETWORK ANALYZER B. ONE TIER DE-EMBEDDING TECHNIQUE C TWO TIER DE-EMBEDDING TECHNIQUE SECTION III: APPENDIX A. REFERENCE BOOKS AND PAPER 4 5 6 7 9 10 14 19 23 24

INTRODUCTION Measurements of the microwave circuits require the very good connections at the interfaces of both the circuit to test fixture and test fixture to Network Analyzer (NA). The measurements of the test connections, however, require the movement of the Network Analyzer reference plane. When performing a standard 7mm calibration of the HP8510, the reference plane for measurements will be the boundary of the coaxial cables. Once the device under test (DUT) is connected to the HP8510 NA, it is important to get good coupling to the I/O ports of the NA. Thus, the reference plane of the network analyzer must be moved to the edge of the circuit. This difference in reference planes is due to the transition launcher. ANA SYSTEM o COAX (OR WAVIGUIOE) ES OUTPUT HALfT O MICAOSTRIT TOUT D.U.T. -.-J Figure A. Microstrip Test fixture approach for de-embedding. (Figure by L.P. Dunleavy [2], permission of author) Test fixtures connect the NA and the DUT using inside connections through the launcher-transitions. However, the calibrated NA cannot distinguish between the scattering matrix of the fixture containing the DUT as a whole and the DUT and the test fixture separately. By de-embedding, the scattering parameters of the DUT can be found from the overall data. To do this, the test fixture must be Page 1

characterized to determine the s-parameters separately, called unterminating. [4] The calibration procedure allows the modelling of the system errors by measuring known standards. In de-embedding, the networks representing the launcher-transisiton between the NA and DUT are assumed and known standards are measured in the place of the DUT. These measurements will allow the reference plane at the interface to be moved to the interface of the DUT through deembedding. There are two types of de-embedding techniques. First, two tier requires the NA to be calibrated using its own standards. The test fixture is characterized using the calibration standards of the DUT. Secondly, a single overall calibration at the DUT interface is performed using the calibration standards of the DUT known as onetier de-embedding. The de-embedding one tier is more accurate since propagation of measurements errors are reduced. An additional advantage to one-tier is the NA's ability to provide the de-embedded device sparameters without more data processing. Lastly, it is also possible to display directly de-embedded data through the graphical representation of measurements. However, for repeatability purposes and contact life, two-tier is more favorable. This manual will present both the one-tier and two-tier deembedding techniques. The one-tier technique has the advantage of being displayed on the HP8510. However, the data can only be displayed for one data point for the DUT. The two-tier deembedding technique requires three procedures: 1) the data transfer of the standard measurements, 2) fixture characterization and 3) the device under test de-embedding. However this method cannot be displayed graphically as easily. Since the circuits being measured require microstrip measurements, TSD (Thru, Short, Delay Method) will be used. This method requires the measurement of a thru, short and delay lines to characterize the test fixture. Once the fixture is characterized, the DUT will be de-embedded after measuring. Lastly, the errors will be extracted as a result of Page 2

the fixture characterization. Below is a flow chart of the basic deembedding process. [2] PERFORM SYSTEM CALIBRATION W/COAXIAL STDS. MEASURE S-PAR'S OF FIXTURE W/STDS. PERFORM FIXTURE CHARACTERIZATION INPUTS: I OUTPUTS: - S-PAR'S OF -eff TSD STDS I -r IFs - PHYSICAL S LENGTH OF FIXTURE S-PAR'S DELAY LINE [S A][SB] 1I MEASURE FIXTURE W/ D.U.T. l1 - DE-EMBED FIXTURE EFFECTS INPUTS: I OUTPUTS: I -- S-PAR'S OF D.U.T. - DE-EMBEDDED S-PAR'S OF D.U.T. -- FIXTURE CHARACTERIZATIONI DATA I I i_ _ _ _ - Figure B: Procedures for measurements and de-embedding. Page 3

SECTION I GENERAL INFORMATION Page 4

EQUIPMENT LIST: 1 8510 B Network Analyzer 1 7mm Calibration Kit 1 7mm Coaxial Cable Set 1 Test: Fixture with 1 Small Holder 1 Medium Holder 1 Large Holder 1 Calibration Kit for Test Fixture Standards: 1 Thru line (shortest delay line) 1 Medium line 1 Long line 1 Open Line ONE-TIER DE-EMBEDDING: 1 Certified Data Cartridge with TRL Calibration Set TWO-TIER DE-EMBEDDING: 3 Basic Programs 1. BAS-UNO: used for fixture characterization 1 RET2: used for data acquistion 1 BAS_SPAR1: used for de-bedding the DUT 1 Device Under Test, DUT (i.e. 2R microstrip filter) Page 5

PROCEDURES: GENERAL OUTLINE: 1. BEFORE BEGINNING, MAKE SURE THE ABOVE ITEMS IN THE EQUIPMENT LIST ARE AVAILBLE. 2 <PRESET> the 8510 [green button] 3. Under the STIMULUS MENU, <SET> the [START] and [STOP] frequencies. a. For the 2-tier measurements, the Start frequency=2 GHz and the Stop frequency =18 GHz. b. For the 1-tier measurements the Start and Stop frequencies can be set in the range of the Network Analyzer. 4. To begin the calibration sequence, this presentation will be in the following order: 1. 7mm Calibration of the HP 851 OB Network Analyzer 2. One-Tier De-embedding Technique 3. Two-Tier De-embedding Technique 5. BEFORE proceeding to the calibration techniques, make sure the following calibration sets (cal sets) are loaded onto the HP 8510B: 7mmn Cal Set and TRL Cal Set. Page 6

LOADING CAL SETS ONTO THE HP 8510B 1. <CHECK> the cal settings by using the [CAL] key. If both settings are correct, proceed to the calibration techniques. Otherwise, proceed to step 2. 2. <LOAD> the TRL measurements onto the NA. To do this, <INSERT> the Data Cartridge into the tape drive. a. <PRESS> [TAPE] key b. <PRESS> [DIRECTORY] to see a listing of the various calibration settings. See Directory Listing Below. DIRECTORY LISTING ON DATA CARTRIDGE File 1 7mm A. 1 File 2 3.5 mm A.1 File 3 K-Conn File 4 TRL CAL* File 5 TRLB (This was added in the solid state lab downstairs.) c. <PRESS> [CAL KIT 1-2]: This will allow the loading of the calibration set into the cal kit. 1. <PRESS> [*1] a. <PRESS> [File 1] 2. <PRESS> [*2] a. <PRESS> [File 4] The procedures in c. allow the calibration kits to be loaded into the correct set. If one of the cal kits is already on the 8510B omit that step and load the proper kit. d. To check the settings, hit the [CAL] key and the display should show: Page 7

I f a I I I I I I - - - - - - I_ CAL1 (7mm*) CAL2 (TRL CAL*) HP 8510 Network Analyzer Page 8

SECTION II CALIBRATION TECHNIQUES Page 9

7mm CALIBRATION OF THE HP 8510 NETWORK ANALYZER PART A. A 1 To begin, <CONNECT> the 7mm Coaxial Cables to Ports 1 and 2 of the HP 8510 Network Analyzer. A2. Using the [CAL] key, <SELECT> calibration set. [CALl] key for the 7mm If the user is familiar with the procedures for 7mm calibration proceed to De-embedding techniques when complete. The 7mm calibration is not necessary for the one tier de-embedding techniques, however it does provide a comparison between the de-embedded measurements and the uncalibrated (embedded) measurements. PART B..SCREEN: ILL' I - I I I z I I HP 8510 Network Analyzer | IL B-I. <SELECT> [Full 2port] Page 10

a — R EIENY Reflection Transmission Isolation t HP 8510 Network Analyzer ] Full 2 Port done 1% Bl. <SELECT> [refletion] SCREEN: Sll Open Short Load S22 Open Short Load HP 8510 Network Analyzer Reflection done a. Using the 7mm Calibration Kit, perform Open and Short measurements by <CONNECTING> the Open standard then the Short Standard to Ports 1 and 2. b. For Loads <CONNECT >the 50 ohm and proceed with the following. 1. For low frequencies, use the lowband measurements with the 50 ohm load. Page 11

2. For wide frequency ranges, use the broadband measurement with the 50 ohm load. For a more accurate calibration also use the sliding load. See the HP 8510 Manual for instructions on using the Sliding Load. c. In the above measurements, using a torque wrench will also increase the accuracy of the measurements and reduce the error introduced due to connector leakage. d. When complete, <PRESS> [Reflection done]. B2. <SELECT> [transmission] N I A I v II - I I I Fwd. Transmission Fwd. Match Thru Rev. Transmission Rev. Match Thru Transmission done [ HP 8510 Network Analyzer | I&1 - a. <CONNECT> the cables for Ports 1 and 2. b. <PRESS> [Fwd. Transmission] [Fwd. Match Thru] [Rev. Transmission] [Rev. Match Thru] c. When complete, <PRESS> [Transmission done] B3. <SELECT > [Isolation] Page 12

SCREE1N: I X I I I Omit isolation Isolation done HP 8510 Network Analyzer a. <PRESS> [omit isolation] b. <PRESS> [Isolation done] c. If Isolation is necessary, see the HP 8510 Manual for further instructions. B4. Returning to the Full 2 Port screen, <PRESS> [Save 2-Port Cal]. The calibration can be saved in any of the open sets. Aside: Sometimes the calibrations sets are full, so the NA will indicate to delete some of the old settings. It is good practice to do this procedure before beginning calibrations. B5. The calibration can be checked by putting on various loads standards. To check Sll, connect the 50 ohm line. It should show at least -20 dB insertion loss. The open circuit or short circuit should show a IS ll of zero, and phase of Sll at +/- 180 degrees. B6. This is the end of the 7mm Calibration. B7. The circuit can be measured to obtain em-bedded data. Page 13

ONE TIER DE-EMBEDDING TECHNIOUE PART A: IMPORTANT: FOR THE MOST ACCURATE AND RELIABLE MEASUREMENTS, A MICROSCOPE SHOULD ALWAYS BE USED TO ENSURE GOOD CONNECTIONS FOR CALIBRATING THE FIXTURE CHARACTERIZATION. THIS IS ABSOLUTELY NECESSARY TO AVOID DAMAGE TO THE LAUNCHERS & MICROSTRIP CONDUCTOR. (See the figure below.) - Micr ostrp Figurel. the end Continuous taper transmission (taper from Eisenhart [ of the transition. ]); at Al. Under the [CAL] menu, <PRESS> [CAL2 TRL CAL*] SCREEN: CAL1 (7mm*) CAL2 (TRL CAL*) I HP 8510 Network Analyzer I A2. <PRESS> [TRL 2 Port] Page 14

SCIREEN: THRU THRU I I I I1 1 H4P 851 0 Network Analyzer Sil RELECT OPEN S22 REFLECT OPEN ISOLATION LINES LINES LOWBAND REFLECTION A3. From this point on the following fixture holders and standards are required for the characterization of the test fixture. Fixture Holders: Standards: 1. small 2. medium 3. large 1. thru line open line 2. med. line 3. long line A4. When making a connection, always check the phase terms. Depending on the frequency range and length of standards, the variation in the number of slopes per division should be noticeable before and after the connection is established. As an example (see below) a good connection has about 1 slope per horizontal division whereas a bad connection is about 1 slope per 3 horizontal divisions. Page 15

w I I I C Good Connection j All-C A k I Bad Connection I...e N f PART B: B 1. Thru menu <CONNECT> <PRESS> [thru] Thru line to Port 1 and 2. B2. Open a. Menu <CONNECT> <PRESS.> [S 1 Open standard to Port Reflect Open] 1 b. <CONNECT> <PRESS> [S22 Open standard to Port 2. Reflect Open] The connectors are labeled IN and OUT. Always connect the IN connector to Port 1 and the Out connector to Port 2. B3. Lines Menu: <PRESS> [Lines] a. <CONNECT> Medium line standard to Ports 1 and 2. <PRESS> [Med. line] b. <CONNECT> Long line standard to Ports 1 and 2. <PRESS> [Long line] c. When complete, <PRESS> [Lines Done] Page 16

B4. <PRESS> [Isolation] a. <PRESS> [Omit Isolation] b. <PRESS> [Isolation done] B5. <PRESS> [Save TRL 2-Port] This calibration can be saved in any of the open calibrations sets. B6. Once the calibration is saved, the HP 8510B will automatically turn the calibration on. B7. Now connect the device under test. To compare the de-embedded measurements with the embedded measurements, choose the cal set storage number and that calibration will be loaded to the network analyzer. A comparison of the phase terms between the embedded and de-embedded fixture will show the most significant difference. As the test fixture is de-embedded, the phase term should become more flat. Also the magnitude of the s-parameters will show a slight decrease when the errors due to the fixture are calibrated out. of the system. See the example of a 2 Resonator filter below. ~12 I*g t AG 46.3 d:MARKER:..... a.. ---,.- --,t,...."S" ' - - -"- r L.........................., _ 1.l iS az '! G; STAR 2. O.0.909900.L. e STEP 18 0 it0eeWe9 Qe De-embedded magnitude measurements Page 17

MI *nly Z EgF.9 ' P 0. @ A 199.9 A S. " T1C6.7 V F -F.6 * C MAi ER --- —- --! ---- - ---- r --- —— S GG.. -- * 2- - * Wi TART 9* 999 sWo a- 19, 9919999 oft De-embedded phase measurements (The flatter response is the de-embeded measurement while the other phase is the nonde-embedded measurerlient.) Page 18

TWO TIER DE-EMBEDDING TECHNIQUES INTRODUCTION: The following set of instructions will be using the HP9000 workstations. The directions will include command instructions, <COMMANDS>, theUSER'SKEYRESPONSE, [KEYRESPONSE],andthe computer response "< >". PART I: 1. Perform a standard 7mm Calibration on the HP8510 Network Analyzer. Set the Number of Points to 51 or 101 on the HP8510 and in the program RET101. The RET101 program has 101 points stored initially. 2. Connect the HP8510 to the HP computer workstation using the external HPIB bus inside the HP8510. PART II: RET101 OR RET2 WILL PERFORM THE DATA TRANSFER BETWEEN THE HP8510 AND THE HP COMPUTER. 1. On the HP computer, Run Program RET101 or RET2(101) 2 <CONNECT> the THRU line THE COMPUTER PROMPTS ARE: 2-1. "<Header(Title, Date, Etc.)>", [CONTINUE] 2-2. "<Press to Continue>" 2-3. "<Select S-Parameters to store>" all or [K3] key example: [restart] [Sll only] [S22 only] [all] 2-4. "<Filename?>" Page 19

2-5. "<Pause and rerun program for next Data Transfer>" 3. Measure the medium standard. 3a. <CONNECFT MEDIUM line Repeat procedures 2-1 thru 2-5. 4. Measure the long standard. 4a. <CONNECT> LONG line Repeat procedures 2-1 thru 2-5. 5. Measure the Sll open standard. 5a. <CONNECTI OPEN line Repeat procedures 2-1 thru 6. Measure the S22 open standard. 6a. <CONNECT> OPEN line Repeat procedures 2-1 thru to Port 2-5. to Port 2-5. 1 for Sll. 2 for S22. 7. Measure the device under test DUT. This measurement is without de-embedding of the test fixture. 7a. <CONNECT> Device Under Test Repeat procedures 2-1 thru 2-5. PART III: BASUNO1 CHARACTERIZES THE TEST FIXTURE. 1. <LOAD> TYPE: "BAS_UNO1:INTERNAL,4,1" (the left 5-1/2" drive) and <RUN>. 2. "< Output to screen (1) or Printer (0)? >" printing the data. 3. "< Enter file for SHORT LINE? >" (filen 4. "< Enter file for MED LINE? >" Choose (1) unless tame} <RETURN> {filename) <RETURN> Page 20

5. "< Enter file for LONG LINE? >" (filename) <RETURN> 6. "< Enter file for OPEN STD PORT 1? >" {filename} <RETURN> 7. "< Enter file for OPEN STD PORT 2? >" {filename} <RETURN> 8. The next prompt shown should say "Working on Gamma". 9. S11[A], S11[B], S22[A], S22[B] are calculated. 10. The computer screen will say the following after the files have been entered: " LAST FILE ENTERED WAS " {filename}. 11. "Write the Data to Disk" {filename 12. " Store data in ASCII <A> OR BDAT<B>? " <CHOOSE B> 13. " That's all folks. " THIS THE LAST LINE OF THE PROGRAM. PART IV: BAS_SPAR1 performing de-embedding of the DUT. 1. <LOAD> TYPE: "BAS_SPARl:INTERNAL,4,1", then, <RUN> 2. <PRESS> [Continue] whenever interrupted. 3. "File name": {filename} 4. Select the Desired operation. PRINT PRINT SCREEN GET FILE PROGRAM INFO 5. "DB/PHASE": [K2] Key This tell the computer the form of the output. 6. Print about 50 points. 7. <EXTRACT> De-embed <RETURN> 8. <FIXTURE CHARACTERIZATION FILENAME> { filename } Page 21

9. "< Write data to Disk?>" (y) 10. "< Storage filename for S-Port: >" {filename} 11. <PRINT> 12. <Db/Phase> Page 22

SECTION III APPENDIX Page 23

REFERENCE BOOKS AND PAPERS 1. Bauer, R.F. and P. Penefield, Jr., "De-embedding and Unterminating", IEEE Trans. Microwave Theory Tech., VOL MTT-22, No. 3, March 1974. 2. Dunleavy, L., " Discontinuity Characterization in Shielded Microstrip: A Theoretical and Experimental Study"., Dissertation, University of Michigan, 1988. 3. Eisenhart, R. L., " A Better Microstrip Connector ", IEEE International Microwave Theory and Techniques Symposoium Digest, 1978, P. 318. 4. Frazen, N.R. and R. A. Speciale, " A New Procedure for System Calibration and Error Removal in Automated S-Parameters Measurements", 5th European Micro. Symp., 1975. 5. HP8510 Automatic Network Analyzer, Palo Alto, CA. 6. Izadian, J.S. and S. M. Izadian, Microwave Transition Design, Artech House, Massachusetts, 1988. 7. Speciale, R.A., " A Generalization of a TSD Network-Analyzer Calibration Procedure, Covering n-Port Scattering-Parameter Measurements Affected by Leakage Errors", IEEE Trans. Microwave Theory Tech., Vol. MTT-25 No 12, Dec. 1977. 8. Speciale, R.A. and N. R. Frazen, "Super TSD Generalization of the TSD Network Analyzer Calibration Procedure, Covering n-Port Measurements with Leakage", IEEE Trans. Microwave Theory Tech., vol MTT-5, 1977. Page 24