Order this document AN1526/D Power Device Impedances: Practical C

The Datasheet Archive - 100 Million Datasheets from 7500 Manufacturers.

Order this document AN1526/D Power Device Impedances: Practical C

Datasheet Thumbnail

Top Searches for this datasheet

SEMICONDUCTOR APPLICATION NOTE
Order this document AN1526/D
Power Device Impedances: Practical Considerations
Prepared Alan Wood Davidson Motorola Semiconductor Products Sector
AN1526
ABSTRACT
definition large-signal series equivalent input output device impedances power transistors explained, together with techniques measuring these parameters. these parameters change under varying load bias conditions examined, impact these variations demonstrated practical broadband test fixture design. point power amplifier design remains published large-signal impedances. These techniques discussed briefly below, outlining their advantages disadvantages. Small-Signal S-Parameters Small-signal designers very familiar with classic s-parameter characterization design methods small-signal linear devices. Data usually available multiple collector bias voltage current conditions over wide range frequencies. ease making these measurements accurately with modern network analyzers done great deal systemizing small-signal amplifier design. availability software analyzing optimizing performance broadband amplifiers establishing their stable operation further improved design methodology. However, when designer asked step into high power design world, immediately confronted with several possible device characterization methods. First all, let's understand term "high power." used this paper, talking about power amplifier devices with output powers from roughly watt several hundred watts. these power levels, small-signal s-parameters lose their usefulness determining appropriate source load reflection coefficients, nothing familiar gain stability circles non-unilateral issues. This because high power class-C amplifiers VERY non-linear. industry standard s-parameters valid only devices operated small-signal linear conditions. These parameters have very limited high power applications. exception presented Frost, using "large-signal s-parameters" stability analysis process. Hejhall, also demonstrates small-signal s-parameters stability analysis power amplifier design shows their utility when large-signal impedances unavailable. Large-Signal S-Parameters availability network analyzers subsequent ease measuring small-signal s-parameters characterization technique referred literature "large-signal s-parameters." Successful measurement usage these parameters been reported [4]-[12]. However, authors aware these parameters being used successfully above watts output power. Measurement these parameters usually accomplished driving device from source achieve collector drain current comparable that expected actual operation.
INTRODUCTION
Many first time power designers, brought diet small-signal s-parameters, previously used solving small signal text book problems, assume these same techniques applicable bipolar class-C class-AB power amplifier design. They consider best match achieved simultaneous conjugate match input output. However, power amplifiers provide higher power gain better efficiency rated output power output purposely mismatched. added benefit doing this potentially unstable devices, conjugately matched, operated stably under these more optimum mismatched conditions. More knowledgeable designers, familiar with large-signal impedances, naively assume published impedances independent operating point. They forever wonder why, although they have designed their impedance transformation networks match device "data book impedances," they have "tweak" circuit optimum performance. This basis much black magic that surrounds power amplifier design, reality circuit designer plagued with paucity good design data, lack adequate tools make initial design "foolproof." This paper intends enlighten these engineers true meaning large-signal series equivalent device impedances. will also show that output impedance most part, under control circuit designer, input device impedance expected change depending upon designers choice output matching (or, some cases, intentional mismatching).
DEFINITIONS
Small-signal s-parameters have gained great deal acceptance power linear amplifier design. Unfortunately, progress large-signal power amplifier design been less substantial. Techniques have been published over years, e.g. large-signal s-parameters; load-pull; stability analysis using small-signal s-parameters, they have gained wide spread acceptance number reasons, including degree applicability ease accuracy measurements. universal starting Application Notes Motorola, Inc. 1991
AN1526
Devices with output power ratings above watts have input reflection coefficient magnitudes very close one, requiring drive levels beyond capability standard network analyzer merely turn device operated class-C. This restriction alleviated some extent, providing degree impedance matching between network analyzer ports device, de-embedding device from impedance transforming network. There also question validity measurements class-C design. device biased off, normally case class-C, measurements these parameters will err. Ideally, transistor should operating with drive applied input when making these measurements. test signal then applied output port reverse gain output reflection coefficient measured with device normal operating bias. This method described more detail Mazumder [8]. Harmonic loading device factor addressed most large-signal s-parameter proponents plays significant part non-linear operation power amplifiers. addition, these measurements require EXTREME caution. Making direct connection network analyzer potentially unstable 100+ watt device could very hazardous network analyzer. Custom built test sets measurement systems almost always required. Further, this type characterization gives designer information other parameters, such efficiency, behave with fundamental load impedance variations. Load-Pull Another characterization technique referred literature "load-pull" [16]-[24]. This technique results graphical presentation performance parameter such gain, efficiency IMD, versus source load impedance. Although technique been known some time, widespread availability desktop computers automatic tuning systems just making this method more attractive, particularly higher power devices. characterization process conceptually quite simple. variety load impedances presented device shown Figure performance device measured each these points, into surface generating program. (See appendix further information). Figure shows example gain watt MRF873 varies with various fundamental frequency load impedances. Figure shows collector efficiency this device varies under same conditions. influence output load impedance input impedance, finite reverse transfer, illustrated input return loss surface Figure These surface plots converted contour plots Figures 4-15. designer easily areas reflection coefficient plane where matching network should centered, high degree variability particular performance parameter. method been proposed Stancliff Poulin [25] examine load-pull performance device varying only fundamental frequency impedance presented device, also second harmonic impedance well. This technique provide designer with extremely useful information about device's behavior. These benefits come without some labor. general, load-pull data usable only operating conditions which measured. seen Figure large load impedance points must presented device output, order construct power gain efficiency contours. Changes bias voltage output power require re-taking data over same range load impedance conditions. Without proper equipment this type characterization very tedious, time consuming, prone errors. With advent automated tuners measurement data time intensive some earlier methods, computer software used manipulate data contours. power devices does require test fixture with some degree impedance matching, matching networks must characterized that device impedances de-embedded. data available over whole band, gain response with frequency optimized flatness best efficiency, selecting frequency load line impedance constant gain circle that compensates inherently higher gain transistor lower frequency. Broadband solutions from network design programs i.e. SuperCompact Touchstonecan evaluated assess much they have comprised gain efficiency throughout band arriving broadband match. Large-Signal Series Equivalent Impedances classic technique high power device characterization used Motorola that large-signal series equivalent input output impedances presented Hejhall [13]. Almost every power device Motorola's Device Data Book section identifying device's large-signal series equivalent input output impedances. Most often, device output impedance referred "the complex conjugate optimum load impedance into which device output operates given output power, voltage frequency." That certainly statement requiring some careful thought, especially since term "output impedance" somewhat misleading. designer high power devices should aware that this called "output impedance" connection with small-signal measurement. Rather, described [13], conjugate LOAD impedance fundamental operating frequency which allowed transistor "function properly." designer should also aware that characterizations device's data sheet valid some very specific conditions frequency, supply voltage, input output power, bias levels, harmonic loading even flange temperature. output impedance published data sheet usually conjugate LOAD impedance that provides maximum gain given output power. Suppose designer interested maximum efficiency, maximum gain. seen load-pull contours fundamental frequency load impedance producing maximum efficiency does coincide with maximum gain impedance. device designer choose which impedance gets published. just valid other. However, quite frankly, gain what sells devices. Likewise, Figures show input return loss, thus device input impedance, also function load impedance. input impedance higher power
Application Notes
AN1526
devices much stronger function load impedance than shown this small device. Device impedances published vendors power transistors should only used approximation first circuit design. broadband amplifier design often difficult obtain good match over full frequency range certain circumstances input output deliberately mismatched compensate gain increase lower frequencies provide level gain response. Good design would load-line where lower gain corresponds higher efficiency operating point. output reactance transistor. required peak output power collector bias voltage determine operating load line. output reactance device under these conditions conjugately matched achieve maximum power transfer, although this condition modified, expense gain, attain higher efficiency. load line resistance given approximately
VCE(sat)RF)2 Pout
MRF873 DEVICE IMPEDANCE COMPARISON DIFFERENT MODES OPERATION
Device characterization techniques only difference high power device specified. Many devices specified characterized class-C operation. Common questions when using device differently from characterized data sheet are: "What will gain be?", "What impedances?" general, power gain highest when device operated class-A slightly lower when device operated class-AB. Power gain lowest when operating class-C decreasing more reverse bias applied base transistor conduction angle decreases. designer should beware, transistor designed rugged, i.e. capable withstanding specified output mismatch under class-C conditions, will LESS RUGGED with forward bias applied base. Device impedances depend only internal structure device, also that device operated. small-signal operation with device biased class-A, optimum device input output impedances, stable device, simultaneous conjugately matched impedances which derived from s-parameters. power operation optimum output impedance function output power, collector bias voltage
where collector supply voltage, Pout required peak power, VCE(sat)RF collector-emitter saturation voltage under frequency operation. value this parameter particularly difficult measure, normal range Volts depending geometry, epitaxial doping thickness. good approximate value 12.5 Volt devices Volts Volt transistors Volts. load line resistance optimum load impedance internal collector node transistor, neglecting junction parasitic device capacitance. These parallel with load line resistance. transistors, operating VHF, above internal collector lead inductance package becomes significant, series with previously defined parallel Cobo network. CS-12 package internal collector lead series inductance represented 0.65 lumped inductor. Some devices have internal collector matching, transforming internal load line impedance higher value ease broadband matching. Comparison impedance data taken small-signal methods, assuming simultaneous conjugate match, large-signal measurements, shows dramatic shifts input impedance (see Table More subtle, measurable differences, seen change input impedance between class-C class-AB data. small-signal s-parameter data given Table below collector bias current both
Table Comparison Input Impedance Different Operating Modes
Frequency (MHz) Simultaneous Conjugate Match (ICQ 0.478 j3.19 0.503 j3.41 0.568 j3.48 Class-AB (ICQ 1.33 j3.34 1.43 j3.41 1.50 j3.32
Class-C 1.10 j3.26 1.19 j3.24 1.24 j3.34
Table Small-Signal S-Parameter Data MRF873 12.5
Frequency (MHz) 0.963 0.877 0.961 0.858 0.958 0.861 172.8 170.9 172.4 172.7 172.3 175.3 0.006 0.024 0.005 0.022 0.004 0.018 7.72 27.9 4.12 17.5 8.35 6.31 0.437 1.567 0.436 1.639 0.435 1.592 4.95 12.7 11.0 3.30 17.7 21.7 0.910 0.697 0.928 0.723 0.948 0.789 163.5 174.5 164.5 169.9 165.4 166.8
Application Notes
AN1526
Table MRF873 Impedance Data Computed from S-Parameters
Freq. (MHz) Input [S11] 0.95 j3.15 1.00 j3.31 1.07 j3.37 Simul. Conjugate. Match 0.48 j3.19 0.50 j3.41 0.57 j3.48 Output Impedance 2.41 j7.24 1.90 j6.79 1.35 j6.41 Simul. Conjugate Match 1.19 j7.15 0.94 j6.61 0.71 j6.27 Data Book 2.93 j1.39 2.92 j1.10 2.92 j0.81 Optimum Impedance From Load Pull 3.60 +j1.26 3.60 +j1.02 3.39 j0.75
1.62 1.61 1.71
0.336 0.270 0.197
Table MRF873 Impedance Data Computed from S-Parameters
Freq. (MHz) Input [S11] 3.29 j3.95 3.83 j3.18 3.74 j2.02 Simul. Conjugate. Match 1.13 j2.98 1.06 j2.90 1.02 j2.86 Output Impedance 8.94 j2.31 8.09 j4.32 5.99 j5.72 Simul. Conjugate Match 2.86 j5.52 2.10 j5.14 1.57 +j4.69 Data Book 2.93 j1.39 2.92 j1.10 2.92 j0.81 Optimum Impedance From Load Pull 3.60 +j1.26 3.60 +j1.02 3.39 j0.75
1.145 1.12 1.12
0.941 0.871 0.693
Since class-C circuits biased cut-off class-AB quiescent current compared collector current peak output power there question which bias point take s-parameters. Below comparison device impedances computed from s-parameters typical bias current class-AB operation same measurements collector current corresponding operation device rated output power under class-C conditions. This data shows large shift impedances computed from s-parameter data introduced changing bias point. this particular transistor, indicates simultaneous conjugate match impedances, taken collector current more line with current under class-C conditions, better match conjugate class-C impedances. Comparison output simultaneous conjugate match impedance with relatively higher optimum load line impedance from load-pull measurements, illustrates load line been shifted increase efficiency amplifier. rough calculation collector efficiency from (Re(Zopt)/[Re(Zopt) Re(ZM1)]) gives value MHz, very close actual value from efficiency contours with same load-line. Note maximum power transfer cannot usually achieved with simultaneous conjugate match because non-linear current limiting characteristics device.
will probably ask, fixture used produce consistent device, what produced fixture?" answer lies device development process. During development power transistor, sample devices typically evaluated narrowband tuneable fixtures. During this evaluation period, device designer balancing multitude performance parameters with customer manufacturing requirements. evaluation period, devices from quite wide distribution will have been constructed. These devices then used design broadband fixture used characterization factory testing production part. typical broadband fixture circuit schematic shown Figures MRF873 power transistor. Broadband performance this fixture shown Figure Specifications device based this fixture devices that defined portion these evaluation devices locked away referred "master engineering correlation units." Motorola's philosophy that event damaged irreplaceable fixture, these master devices sufficient duplicate fixture. sure, there considerable data taken original fixture. This data limited performance also includes such information broadband source load impedance sweeps. engineer power design must understand that impedances presented data sheet impedances broadband fixture. Data Book Impedances Data book impedances normally taken rated output power nominal supply voltage. transistor operated test fixture with range tuning either on-board trimming capacitors external tuners combination both methods. impedances seen data sheet represent average several devices placed narrowband fixture tuned, usually maximum gain, specific output power, supply voltage frequency with reflected power minimized least input return loss. device removed SOURCE LOAD impedances measured with reference plane device package edge. piece information specified Motorola data sheets other vendor's data sheet known authors) impedances
CURRENT METHODS ENSURING CONSISTENT DEVICE IMPEDANCES
Users power transistors have main concerns with regard long term consistency device, minimum gain requirements consistent impedances. Most recent devices characterized land mobile environment utilize broadband fixture demonstrate performance over range frequencies. recently introduced MRF650 goes step further specifies gain, efficiency input return loss three frequencies operation specified test fixture. Motorola found over years that this most cost effective producing power devices with minimum variability. course, testing characterization techniques constantly being evaluated. engineer unfamiliar with power devices
Application Notes
AN1526
harmonic frequencies presented device. most cases, first shunt capacitance combined with device package series inductance that determines second harmonic impedance present INTERNAL collector-emitter terminals. designer should simply aware that possible have perfect match fundamental frequency published performance improper harmonic terminating impedances. further point clarification measurement technique these very impedances. Several techniques exist measurement source load impedances presented device. simplest approach construct impedance measuring probe similar those shown Figures 17-19. These probes nothing more than blank device package appropriate fixture being used, with short piece small semi-rigid coax carefully soldered place. most convenient method calibration first perform full one-port calibration network analyzer using calibration kit. Then, with probe clamped into tuned test fixture piece copper foil slipped under probe's center tab, port extension reset phase angle frequency interest degrees. This technique valid packages through MHz. Square packages such CS-12 used GHz. error present discontinuity between semi-rigid coax package edge. This discontinuity been de-embedded found negligible. Break-Apart Test Fixture technique which avoids these discontinuities involves fixture which "broken apart" reference planes. Figure shows construction break-apart test fixture. After tuning circuit desired performance test fixture broken apart, bridge which device sits removed, co-axial connectors installed reference planes (Figure 23). impedances presented device then measured using network analyzer calibrated with standard type calibration kit, port extension applied rotate reference plane. off-line impedance measurement techniques described above, break-apart test fixture offers advantages improved repeatability more consistent measurement plane location. This expense more time intensive measurements, since each frequency point, fixture partially disassembled connectors installed before impedances measured. break-apart test fixture really comes into when used in-line impedance measurements. Each half fixture characterized port using network analyzer, with knowledge impedances presented externally test fixture, device impedances de-embedded [26]-[30]. test fixture provides important "close match measure broadband performance, while external tuners provide fine tuning measurement frequencies within operating band. test fixture also provides biasing transistor current levels higher than normally accommodated external bias tees, correctly bypassed, improves stability under mismatch conditions. Automated Tuners Automated tuners offer number advantages. used wisely, they provide in-line impedance measurement capability, allow rapid characterization device under load-pull conditions. In-line measurement device impedances makes practical measure sufficient number devices establish impedance distributions particular device type. Currently available systems are, however, still slow production environment 100% testing transistors. Load-pull characterization performed under custom conditions enabling amplifier designer start matching network synthesis with impedance data representative final operating conditions. Automated tuners need coupled with some type impedance matching test fixturing three very important reasons. impedance transformation range normally limited 10:1 precluding their with most power transistors that have relatively input impedances outside this range. Optimum performance power amplifier requires careful attention harmonic loading, which many cases requires shunt capacitance close package. input/output impedances also require loss return paths circulating ground currents. Bias networks designed test fixture minimize potential instability necessary correct operation automated tuner search algorithms. Measurement Accuracy Factors There some tolerance package dimensions which dictates that test fixture designed with some mechanical tolerance allow devices tested maximum extremes device width height over seating plane. contact leads test fixture pads therefore variable contributing additional series inductance input, output ground leads. This results more inductive device impedances than expected careful steps taken minimize this error. Absolute Accuracy Measurement Instrument, Network Analyzer Great improvements have been made network analyzer measurement accuracy over last years [32]-[37]. many years device impedances were routinely measured with vector voltmeters, using only single correction term frequency response couplers. Now, port measurements, three term error correction norm, correcting directivity, source mismatch frequency response. network analyzer does still introduce degree measurement uncertainty proportional magnitude reflection co-efficient. This more problem with higher power devices where real part impedances below ohm. reader referred manufacturers operating manuals maximum possible magnitude error. worst case, transistor with real part impedance, error large ohm.
Application Notes
AN1526
MHz, Class-C, 12.5 VDC, Watts Figure MRF873 Gain Surface Fundamental Load Impedance
MHz, Class-C, 12.5 VDC, Watts Figure MRF873 Efficiency Surface Fundamental Load Impedance
MHz, Class-C, 12.5 VDC, Watts Figure MRF873 Return Loss Surface Fundamental Load Impedance
Application Notes
AN1526
j3.0 j1.5 j6.0 j9.0 j0.6 j0.6 j0.6 j9.0 j9.0 j0.6 j1.5 j3.0 j6.0 j9.0
j1.5 j3.0
j6.0
j1.5 j3.0
j6.0
Load Impedance Chart Ohms MHz, Class-C, 12.5 VDC, Watts Figure MRF873 Constant Gain Contours
Load Impedance Chart Ohms MHz, Class-C, 12.5 VDC, Watts Figure MRF873 Constant Efficiency Contours
j3.0 j1.5 j6.0 j9.0 j0.6 j0.6 j9.0 j0.6 j0.6 j1.5
j3.0 j6.0 j9.0 j9.0
j1.5 j3.0
j6.0
j1.5 j3.0
j6.0
Load Impedance Chart Ohms MHz, Class-C, 12.5 VDC, Watts Figure MRF873 Combined Gain Efficiency Contours
Load Impedance Chart Ohms MHz, Class-C, 12.5 VDC, Watts Figure MRF873 Constant Input Return Loss Contours
Application Notes
AN1526
j3.0 j1.5 j6.0 j9.0 j0.6 j0.6 j1.5 j3.0 j6.0 j9.0
j0.6
j9.0
j0.6
j9.0
j1.5 j3.0
j6.0
j1.5 j3.0
j6.0
Load Impedance Chart Ohms MHz, Class-C, 12.5 VDC, Watts Figure MRF873 Constant Gain Contours
Load Impedance Chart Ohms MHz, Class-C, 12.5 VDC, Watts Figure MRF873 Constant Efficiency Contours
j3.0 j1.5 j6.0 j9.0 j0.6 j9.0 j0.6 j0.6 j1.5
j3.0 j6.0 j9.0
j0.6
j9.0
j1.5 j3.0
j6.0
j1.5 j3.0
j6.0
Load Impedance Chart Ohms MHz, Class-C, 12.5 VDC, Watts Figure MRF873 Combined Gain Efficiency Contours
Load Impedance Chart Ohms MHz, Class-C, 12.5 VDC, Watts Figure MRF873 Constant Input Return Loss Contours
Application Notes
AN1526
j3.0 j1.5 j6.0 j9.0 j0.6 j0.6 j1.5 j3.0 j6.0 j9.0
j0.6 j9.0
j0.6
j9.0
j1.5 j3.0
j6.0
j1.5 j3.0
j6.0
Load Impedance Chart Ohms MHz, Class-C, 12.5 VDC, Watts Figure MRF873 Constant Gain Contours
Load Impedance Chart Ohms MHz, Class-C, 12.5 VDC, Watts Figure MRF873 Constant Efficiency Contours
j3.0 j1.5 j6.0 j9.0 j1.5
j3.0 j6.0 j9.0 j0.6
j0.6
j9.0 j0.6
j0.6
j9.0
j1.5 j3.0
j6.0
j1.5 j3.0
j6.0
Load Impedance Chart Ohms MHz, Class-C, 12.5 VDC, Watts Figure MRF873 Combined Gain Efficiency Contours
Load Impedance Chart Ohms MHz, Class-C, 12.5 VDC, Watts Figure MRF873 Constant Input Return Loss Contours
Application Notes
AN1526
j3.0 j1.5 j6.0 j9.0 j0.6
MSUB MSUB WIRE
2000 0.29
j0.6 j9.0
j1.5 j3.0
j6.0
Chart Ohms Figure Load-Pull Impedances Presented MRF873 Figure Drawing Package Impedance Measurement Probe Including De-Embedding Circuit Model
Figure Photograph CS-12 Impedance Measurement Probe
Figure Photograph Impedance Measurement Probe
Figure Photograph MRF873 Broadband Production Test Fixture
Application Notes
AN1526
SHORTING PLUG PORT INPUT D.U.T. SOCKET OUTPUT 12.5
Tantalum 1000 Unelco Mil, Chip Capacitor Mini-Unelco Johansen Gigatrim 7290 Variable Mini-Underwood Mini-Underwood Mini-Underwood NOTE:
Turn, Around Resistor Ferroxcube Bead #56-590-85-38 Turns, Choke Turns, Choke Microstrip Microstrip Microstrip Board Material 0.032 Glass Teflon Copper Clad 2.55
down from socket edge.
Figure MRF873 Boardband Production Test Fixture Schematic
Figure Photograph Break-Apart Test Fixture Fully Assembled
Figure Photograph Break-Apart Test Fixture Setup Impedance Measurements
Application Notes
AN1526
GPIB BENCH CONTROLLER
OUTPUT POWER METER INPUT POWER METER REFLECTED POWER METER
VECTOR VOLTMETER
POWER SPLITTER
POWER AMPLIFIER
DUAL DIRECTIONAL COUPLER
TEST FIXTURE
DUAL DIRECTIONAL COUPLER
LOAD TERMINATION VARIABLE POWER ATTENUATOR VARIABLE SHORTED STUB
SYNTHESIZED SIGNAL GENERATOR
BIAS SUPPLY
Figure Load-Pull Test Setup
POWER GAIN (dB) FREQUENCY, (MHz) INPUT VSWR
COLLECTOR EFFICIENCY
INPUT VSWR
12.5 Pout WATTS
12.5 VDC, Pout Watts Figure Broadband Performance MRF873 Production Test Fixture
Application Notes
AN1526
12.5 VDC, Pout Watts Figure MRF873 Data Book Input Output Impedances
Application Notes
AN1526
CONCLUSIONS
power transistor have demonstrated that input output large-signal device impedances only frequency dependent, also determined operating conditions device. Because wide range possible applications, virtually impossible device manufacturers present impedance data every eventuality. user, therefore, left with choice either measuring device impedances under conditions plans device, resorting classical methods tweaking circuit impedances into approximately optimum match. future does hold some promise areas. Automated tuners will enable impedance data gathered faster, enabling more comprehensive data included data sheets with eventual possibility publishing device impedance distributions. Compact device models conjunction with non-linear simulators hold best hope simulating device under proposed operating conditions, then permitting software synthesize optimum broadband matching networks. fixture, vector voltmeter monitors test fixture load reflection coefficient Standard three term error correction applied measured reflection co-efficient this value then used correct output power, Pout. system calibrated over range frequencies error correction software. following formula used correct power reading, [16]
e22e24M e21M
Pout
TMSuperCompact trademark Compact Software Touchstone registered trademark EESof, Inc.
APPENDIX Load-Pull Method Corrections Power Measurement Non-50 Environment
Load-pull measurements employ variety test equipment methods. load-pull measurements described earlier this paper used readily available inexpensive equipment. addition usual equipment found power bench including computer instrument controller, only additional pieces equipment needed vector voltmeter, variety attenuation power attenuators, variable length shorted stub. Figure shows block diagram bench set-up. series load mismatch conditions established terminating broadband test fixture with attenuators shorted stub. shorted stub calibrated approximately intervals establish varying phase shifts. varying value attenuation, grid load impedances presented device network VSWR circles reflection coefficient plane. system first calibrated using network analyzer probe device socket measure this series load impedances. vector voltmeter, with error correction, could course have been used measure these impedances. After system calibration, transistor operated with drive level adjusted obtain rated output power under optimum tuning maximum gain into matched load. With drive level fixed this level, output power remeasured over range calibrated load impedances. This procedure repeated each frequency desired. input match tuned zero reflected power with output terminated matched load. input return loss, under mismatched conditions, thereby indicates changes magnitude input impedance. addition usual power meter measure output power from test
where uncorrected load reflection coefficient, e23, e21, e22e24 directivity, source match frequency response errors determined normal vector analyzer correction techniques [32], measured power meter reading corrected directional coupler coupling magnitude, attenuation meter frequency response. Using this method, accurate measurement power hence efficiency obtained system which load impedance perturbed from characteristic impedance transmission line power meter components. Contours generated from this grid data number commercially available software packages. alternative system would tuners place attenuator/shorted stub combination. tuners either manual automated. advantage latter that with suitable software de-embedded load impedance presented device available instantaneously. Also, with suitable software, gain efficiency circles determined contour following techniques real time, instead fitting contours measurements grid load mismatch points [20].
REFERENCES
Kurokawa, "Power Waves Scattering Matrix," IEEE Transactions Microwave Theory Techniques, 194-202, March 1965. Frost, "Large-Signal S-Parameters Help Analyze Stability," Electronic Design, 93-98, 1980. Hejhall, "Small-Signal Parameters Power- Design," Microwaves 141-144, September, 1985. Chaffin, Leighton, "Large-Signal S-Parameter Characterization Power Transistors," Digest Technical Papers, Proceedings 1973 IEEE International Microwave Symposium, University Colorado, Boulder, June 1973. Houselander, Chow, Spence, "Transistor Characterization Effective Large-Signal 2-Port Parameters," IEEE Journal Solid-State Circuits, SC-5, 77-79, April 1970. "Large-Signal S-Parameter Measurements Class Operated Transistors," Nachrichtentech October 1968. Leighton, Chaffin, Webb, Amplifier Design with Large-Signal S-Parameters," IEEE Transactions Microwave Theory Techniques, MTT-21, 809-814, December 1973.
Application Notes
AN1526
Mazumder, "Two-Signal Method Measuring Large-Signal S-Parameters Transistors," IEEE Transactions Microwave Theory Techniques, vol. MTT-26, 417-420, June 1978. Mazumder, "Characterization Design Microwave Class Transistor Power Amplifier," Ph.D. dissertation, Carleton University, Ottawa, Canada, 1976. (10) Mazumder Puije, "Characterization Nonlinear 2-Ports Design Class-C Amplifiers," Microwaves, Optics Acoustics, vol. 139-142, July 1977. (11) Mazumder Puije, Experimental Method Characterizing Nonlinear 2-Ports Application Microwave Class-C Transistor Power Amplifier Design," IEEE Journal Solid-State Circuits, vol. SC-12, October 1977. (12) William Overstreet William Davis, "Measuring Parameters Large-Signal Nonlinear Devices," Microwaves 91-96, November 1987. (13) Hejhall, "Systemizing Power Amplifier Design," Motorola Application Note AN-282, Motorola Semiconductor Products, Inc., Phoenix, Arizona, August 1968. (14) Bostain, Krauss, Raab, Solid State Radio Engineering, John Wiley Sons, Inc., York, 1980, 406-408. (15) Bowick, Circuit Design, Howard Sams Company, Indianapolis, 1982. (16) Rodney Tucker Peter Bradley, "Computer- Aided Error Correction Large-Signal Load-Pull Measurements," IEEE Transactions Microwave Theory Techniques, vol. MTT-32, March 1984. (17) Dennis Poulin, "Load-Pull Measurements Help Meet Your Match," Microwaves, 61-65, Nov. 1980. (18) Hiroyuki Yoichi Aono "11-GHz GaAs Power MESFET Load-Pull Measurements Utilizing Method Determining Tuner Parameters," IEEE Trans. Microwave Theory Techniques, vol. 394-399, 1979. (19) Bava, Pisani, Pozzolo, "Active Load Technique Load-Pull Characterisation Microwave Frequencies," Electronics Lett., vol. 178-179, February 1982. (20) Joseph Cusack, Stewart Perlow, Barry Perlman, "Automatic Load Contour Mapping Microwave Power Transistors." IEEE Trans. Microwave Theory Techniques, vol. MTT-22, vol. 1146-1152, December 1974. (21) David Zemack, Load Pull Measurement Technique Eases GaAs Characterization," Microwave Journal, 63-67, November 1980. (22) Rodney Tucker, Characterization Microwave Power FET's," IEEE Trans. Microwave Theory Techniques, vol. MTT-29, vol. 776-781, August 1981. Yoichiro Takayama, Load-Pull Characterization Method Microwave Transistors," Proc. IEEE MTT-S, 218-220, June 1976. Khilla, "Accurate Measurement High-Power GaAs Terminating Impedances Improves Device Characterization," Microwave Journal, 255-263, 1985. Roger Stancliff Dennis Poulin, "Harmonic Load-Pull," Proc. IEEE MTT-S, 185-187, 1979. Ronald Bauer Paul Penfield, "De-Embedding Unterminating," IEEE Trans. Microwave Theory Techniques, vol. MTT-22, vol. 282-288, March 1974. Lawrence Dunleavy Katehi, "Eliminate Surprises when De-Embedding Microstrip Launches," Microwave 117-112, August 1987. Lance Glasser, Analysis Microwave Embedding Errors," IEEE Trans. Microwave Theory Techniques, vol. MTT-26, vol. 379-380, 1978. Michael Hillbun, "Compensate Analyzer Errors Embed S-Parameters," Microwaves, 87-92, January 1980. Richard Lane, "De-Embedding Device Scattering Parameters," Microwave Journal, 149-156, August 1984. Swanson, "Ferret Fixture Errors With Careful Calibration," Microwaves, 79-86, January 1980. Fitzpatrick, "Error Models System Measurement," Microwave Journal, 63-66, 1978. Kasa, "Closed-Form Mathematical Solutions Some Network Analyzer Calibration Equations," IEEE Trans. Instrumentation Measurement, vol. IM-23, vol. 399-402, December 1974. Kruppa Sodomsky, Explicit Solution Scattering Parameters Linear Two-Port Measured with Imperfect Test Set," IEEE Trans. Microwave Theory Techniques, vol. MTT-19, vol. 122-123, January 1971. Daniel Meeks, "Re-Normalizing Scattering Parameters," Design, 41-42. Stig Rehnmark, Calibration Process Automatic Network Analyzer Systems," IEEE Trans. Microwave Theory Techniques, vol. MTT-24, vol. 457-458, April 1974. Schurmer, "Calibration Procedure Computer- Corrected S-Parameter Characterisation Devices Mounted Microstrip," Electronics Lett., vol. July 1973.
(23)
(24)
(25)
(26)
(27)
(28)
(29)
(30)
(31) (32) (33)
(34)
(35) (36)
(37)
Application Notes
AN1526
Motorola reserves right make changes without further notice products herein. Motorola makes warranty, representation guarantee regarding suitability products particular purpose, does Motorola assume liability arising application product circuit, specifically disclaims liability, including without limitation consequential incidental damages. "Typical" parameters vary different applications. operating parameters, including "Typicals" must validated each customer application customer's technical experts. Motorola does convey license under patent rights rights others. Motorola products designed, intended, authorized components systems intended surgical implant into body, other applications intended support sustain life, other application which failure Motorola product could create situation where personal injury death occur. Should Buyer purchase Motorola products such unintended unauthorized application, Buyer shall indemnify hold Motorola officers, employees, subsidiaries, affiliates, distributors harmless against claims, costs, damages, expenses, reasonable attorney fees arising directly indirectly, claim personal injury death associated with such unintended unauthorized use, even such claim alleges that Motorola negligent regarding design manufacture part. Motorola registered trademarks Motorola, Inc. Motorola, Inc. Equal Opportunity/Affirmative Action Employer. reach EUROPE: Motorola Literature Distribution; P.O. 20912; Phoenix, Arizona 85036. 1-800-441-2447 MFAX: RMFAX0@email.sps.mot.com TOUCHTONE (602) 244-6609 INTERNET: http://Design-NET.com
JAPAN: Nippon Motorola Ltd.; Tatsumi-SPD-JLDC, Toshikatsu Otsuki, Seibu-Butsuryu-Center, 3-14-2 Tatsumi Koto-Ku, Tokyo 135, Japan. 03-3521-8315 HONG KONG: Motorola Semiconductors H.K. Ltd.; Ping Industrial Park, Ting Road, N.T., Hong Kong. 852-26629298
*AN1526/D*
AN1526/D Application Notes

Order this document AN1526/D Power Device Impedances: Practical C

Top Searches for this datasheet

Other recent searches