This paper describes a new approach for fast and accurate determination of the source reflection coefficient in microwave source-pull measurements. To the authors' knowledge, this is the only technique that allows the simultaneous measurement of the source and the DUT gammas. A traditional vector network analyzer is used as a three-channel receiver. The calibration procedure is based on a new reflectometer model that extends the traditional error box concept. Experimental results are presented and compared to data obtained with traditional techniques

Ferrero, Andrea Pierenrico

Madonna, G.L.

Pirola, Marco

Pisani, Umberto

English

G.  Madonna

A. Ferrero

M. Pirola

U. Pisani

Crossref

Testing microwave devices under different source impedance values-a novel technique for on-line measurement of source and device reflection coefficients

FERRERO, ANDREA PIERENRICO

PIROLA, Marco

MADONNA G

PISANI U.

PORTO@iris (Publications Open Repository TOrino - Politecnico di Torino)

05 August 2020POLITECNICO DI TORINORepository ISTITUZIONALETesting microwave devices under different source impedances: a novel technique for on-line measurement of sourceand device reflection coefficients / FERRERO A; MADONNA G; PIROLA M.; PISANI U. - In: IEEE TRANSACTIONS ONINSTRUMENTATION AND MEASUREMENT. - ISSN 0018-9456. - im-49(2000), pp. 285-289.OriginalTesting microwave devices under different source impedances: a novel technique for on-linemeasurement of source and device reflection coefficientsPublisher:PublishedDOI:10.1109/19.843065Terms of use:openAccessPublisher copyright(Article begins on next page)This article is made available under terms and conditions as specified in the  corresponding bibliographic description inthe repositoryAvailability:This version is available at: 11583/1404418 since:IEEETesting Microwave Devices under Different Source Impedances: a Novel Technique for On-Line Measurement of Source and Device Reflection Coefficients G.L.Madonna, M.Pirola, A.Ferrero and U.Pisani Dipartimento di Elettronica Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy ferrero @polito.it Abstract This paper describes a new approach for fast and accurate determination of the source reflection coefficient in microwave source-pull measurements. To the authors' knowledge, this is the only technique that allows the simultaneous measurement of the source and the DUT gammas. A traditional vector network analyzer is used as a three-channel receiver. The calibration procedure is based on a new rejlectometer model that extends the traditional error box concept. Experimental results are presented and compared to data obtained with traditional techniques. 1. Introduction Microwave source-pull measurement techniques consist in monitoring the desired performance of a device under test (DUT) while driving it with different source impedances. This approach is widely used for microwave active device characterization, both in small and large signal conditions. A typical application is low noise amplifier (LNA) design to experimentally obtain the optimum noise impedance [l] or the matching network for mixers, oscillators and high efficiency amplifiers To complete an accurate characterization of the DUT in a reasonable time, both automatic source impedance setting and measurement capabilities are mandatory. Different systems have been proposed for the former need, based on either passive tuners [2, 41 or active-load techniques [3, 5 - 71. This paper mainly deals with the second topic, i.e. the fast and accurate determination of the source impedance along with the measurement of the DUT input characteristics. [2 - 41. 130 The well-known problem definition is shown in figure 1. Traditional measurement systems are able to obtain calibrated values of a and b and their ratio r, ,b a On the other side, the source reflection coefficient we are looking for is defined as and it is equal to ratio a/b  only if a, = 0 ,  i.e. the internal generator is switched off. A simple technique consists in switching the microwave generator off and measuring the equivalent source reflection coefficient by exciting the test-set back from the DUT port. This solution is accurate, but it cannot be used for automatic characterization since it requires disconnecting the DUT at each tuner position. Figure 1. Definition of the problem. TUNABLE LOAD @ bt D + a  - b  D MICROWAVE SOURCE Figure 2. Simplified block scheme of the source-pull imeasurement test-set. A completely #different approach is described in [ I ] ,  whcrc the reflection coefficient of the tuning elerrlent is continuously moriitorcd by a six-port reflectometer in reverse configuration. This technique is both accurate and suitable for automatic source pulling; however, the problem is just diverted, since now it  is the DUT reflection coefficient that cannot be determined. The solution recently proposed in [6] is probably the most effective, since it allows the accurate measurement of both the DUT and thc source reflection coerlicient, but - again - two distinct acquisition steps arc necessary. This paper describes a novel solution based on a thrce- sampler vector network analyzer (VNA). The test-set is shown in figure 2 and it  is analogous to the systems described in [ l ,  61. The signal from a microwave synthesized source is summed with the wave reflcctcd by the tuning clcmerit and injectcd into the DUT. Signal arpl is drawn from the generator output to provide a stable refcrence to thc receiver and a terminated circuhtor is used to guarantee isolation of the microwave synthesizer. The main breakthrough is that, after the new calibration procedure herc described, the Ineasurements of waves a, and b,,, with respect to aryl’ are sufficient to determine source and DUT reflection coefficients, respectively Ts arid T,. The interesting; features of the novel technique are: * a new model for the input retlectoIncter, which extcnd the well-known err-or-box concept [8]; a new calibration procedure, based on traditional one port standard devices; simultaneous measurements of the source and the DUT gammas; in particular: 0 it is not necessary to disconnect the DUT to measure the source gamma; e it is not necessary to switch the microwave source off, nor to disconnect it. 2. Calibration procedure 2.1. Theoretical aspects The novel error model is shown in figure 3. The flow graphs of figure 3a and 3b are derived from classical load-pull theory [9], [lo]. They allow to link the waves a ,  b at the DUT reference plane with the measured quantities a,,,, b,x and, simultaneously, the same a,  b with the wave a,, b, at the tuner plane T-T’ (see figure 2). Flow graph of figure 3c represents the key point of the new model. The waves at the tuner plane (ar, b,) when the source is turned on are written as a linear function of all three measured quantities, a,,,, 6, and This leads to a novel concept of error-box, which extends the original idea to include the source terms represented by urd Figure 3. Error model. 131 2.2. Calibration sequence and de-embedding Table 1 shows the connection sequence of the standard devices whose measurements are sufficient to compute all the error coefficients. The entire set of connections is divided into two subsets. First, source is plugged to section S-S’ and standard connections from 1 to 6 are made. Afterwards, the microwave source is turned to the DUT port and three additional standards are connected to shift the reference plane from section T-T’ to D-D’. 1 2 3 4 5 6 7 8 9 ~ - __ DUT plane SHORT SHORT SHORT OPEN OPEN LOAD D - D ’  source source source Tuner plane Source plane SHORT source source LOAD source SHORT source ! LOAD source source 4%k+-Er Fable 1. Sequence of standard devices and relative position of the microwave source signal. De-embedding is carried out in three distinct steps: 1. DUT reflection coefficient rL at section D-D’ is computed by the error coefficient of figure 3b; 2. tuner reflection coefficient Tt at section T-T’ is computed by the error box of figure 3a; 3. the same Tt is shifted to the DUT reference plane D- D’; the result is proved to be the source reflection coefficient rs. 3. Experimental results Measurement results are shown in figures from 4 to 6. Source reflection coefficient is limited in magnitude, since a simple passive tuner was used. To validate the novel technique, various gammas source were measured under different conditians. For each tuner position: first gamma source was directly measured with a VNA at DUT port and the source switched off, yielding Tss.o; then, a short was connected to the DUT port to simulate an high-impedance device and gamma source was computed by the described technique at two different source output power levels (10 and 0 dBm), obtaining respectively rS,, and l-s,2. Results computed for a single tuner setting are shown in figure 4 as a function of frequency. l-s,l and rs,2 plots overlap, proving that the technique de-embeds the same Ts for different values of stimulus as. Moreover, they show only small differences with respect to Ts,o, as pointed out in figure 5. Finally, figure 6 shows various source gammas obtained at single frequency for different tuner positions. 4. Conclusions A new calibration technique has been presented, which allows to obtain simultaneous corrected measurements of the source and the device input impedance for fast microwave characterization. Experimental results prove the accuracy of the proposed method against the traditional techniques. References [I1 121 [31 141 151 [61 171 181 D.L. Le and F.M. Ghannouchi, “Noise measurements of microwave transistor using and uncalibrated mechanical stub tuner and a built-in reverse six-port reflectometer,” IEEE Trans. Instrument Meas., vol. IM-44, pp.847-852, Aug. 1995. F.M. Ghannouchi and R. Bosisio, “Source-pull/load-pull oscillator measurements at microwave/mm wave frequencies,” IEEE Trans. Microwave Theory Tech., vol. MTT-41, pp. 32-35, Feb. 1992. D.L. Le and F.M. Ghannouchi, “Multitone characterization and design of FET resistive mixers based on combined active source-pull/load-pull techniques,” IEEE Trans. Microwave Theory Tech., vol. M’IT-46, pp. 1201-1208, Sep. 1998. C. Tsironis, “A novel design method of wideband power amplifier,” Microwave J., pp. 303-304, May 1992. G.P. Bava, U. Pisani and V. Pozzolo, “’Source pull’ technique at microwave frequencies,” Electronic Lett., vo1.20, n.4, pp. 152-154, Feb. 1984. G. Berghoff, E. Bergeault, B. Huyart and L. Jallet, “Automated characterization of HF power transistor by source-pull and multiharmonic load-pull measurements based on six-port techniques,” IEEE Trans. Microwave Theory Tech., vol. M’IT-46, pp. 2068-2073, Dec. 1998. D.L. Le, P. Poire and F.M. Ghannouchi, “Six-port-based active source-pull measurement technique,” Meas.Sci.Technol., vo1.9, pp. 1336-1342, Aug. 1998. H.J.Eu1 and BSchieck, “A generalized theory and new calibration procedures for network analyzer self- calibration,” IEEE Trans. Microwave Theory Tech., vol. M’IT-39, pp. 724-731, Apr. 1991. 132 [9] I. Hecht, “Improved error-correction technique for large- [ 101 A. Ferrero and U. Pisani, “An improved calibration signal load-pull measurement,” IEEE Trans. Microwave technique for on-wafer large-signal trarisistor Theory Tech., vol. MTT-35, pp. 1060-1062, Nov. 19E7. characterization,” IEEE Trans. Instr. Meas., vol. IIM-42, PP. 360-364, Apr. 1993. 8 9 10 11 12 13 14 15 16 Frequency [GHz] Figure 4. Source gamma for tuner position 2 (see also figure 6): rs,o (VNA: 0), Ts,, (new technique, with source power at 10 dBm: V), Ts,2 (new technique, with source power ait 0 dBm: 0). 4 ...... ........................ 10 !mo/yh*N -1 .........,... -2 I , Frequency [GHz] Figure 6. Source reflection coefficient at 12GHz for various tuner positions computed by different techniques: Ts,o (VNA: o), Ts,, (new technique, with source power at 10 dBm: V). Squares (a) represent the corresponding tuner input gamma at section T-’T’: reflectometer attenuation and phase shift are evident. Figure 5. Differences between source gammas comiputed by different techniques. Degradation of phase accuracy is evident for lr,l < 20 dEl, where phase is no more significant. 133 

Testing microwave devices under different source impedances: a novel technique for on-line measurement of source and device reflection coefficients

PORTO Publications Open Repository TOrino

Testing Microwave Devices under Different Source Impedances: 
a Novel Technique for On-Line Measurement 
of Source and Device Reflection Coefficients 
G.L.Madonna, M.Pirola, A.Ferrero and U.Pisani 
Dipartimento di Elettronica 
Politecnico di Torino, 
Corso Duca degli Abruzzi 24, 10129 Torino, Italy 
ferrero @polito.it 
Abstract 
This paper describes a new approach for fast and 
accurate determination of the source reflection 
coefficient in microwave source-pull measurements. To 
the authors' knowledge, this is the only technique that 
allows the simultaneous measurement of the source and 
the DUT gammas. A traditional vector network analyzer 
is used as a three-channel receiver. The calibration 
procedure is based on a new rejlectometer model that 
extends the traditional error box concept. Experimental 
results are presented and compared to data obtained 
with traditional techniques. 
1. Introduction 
Microwave source-pull measurement techniques 
consist in monitoring the desired performance of a device 
under test (DUT) while driving it with different source 
impedances. This approach is widely used for microwave 
active device characterization, both in small and large 
signal conditions. A typical application is low noise 
amplifier (LNA) design to experimentally obtain the 
optimum noise impedance [l] or the matching network 
for mixers, oscillators and high efficiency amplifiers 
To complete an accurate characterization of the DUT 
in a reasonable time, both automatic source impedance 
setting and measurement capabilities are mandatory. 
Different systems have been proposed for the former 
need, based on either passive tuners [2, 41 or active-load 
techniques [3, 5 - 71. This paper mainly deals with the 
second topic, i.e. the fast and accurate determination of 
the source impedance along with the measurement of the 
DUT input characteristics. 
[2 - 41. 
130 
The well-known problem definition is shown in figure 
1. Traditional measurement systems are able to obtain 
calibrated values of a and b and their ratio 
r, ,b 
a 
On the other side, the source reflection coefficient we are 
looking for is defined as 
and it is equal to ratio a/b  only if a, = 0 ,  i.e. the 
internal generator is switched off. 
A simple technique consists in switching the 
microwave generator off and measuring the equivalent 
source reflection coefficient by exciting the test-set back 
from the DUT port. This solution is accurate, but it 
cannot be used for automatic characterization since it 
requires disconnecting the DUT at each tuner position. 
Figure 1. Definition of the problem. 
TUNABLE 
LOAD 
@ bt D + a  
- b  
D 
MICROWAVE 
SOURCE 
Figure 2. Simplified block scheme of the 
source-pull imeasurement test-set. 
A completely #different approach is described in [ I ] ,  
whcrc the reflection coefficient of the tuning elerrlent is 
continuously moriitorcd by a six-port reflectometer in 
reverse configuration. This technique is both accurate 
and suitable for automatic source pulling; however, the 
problem is just diverted, since now it  is the DUT 
reflection coefficient that cannot be determined. 
The solution recently proposed in [6] is probably the 
most effective, since it allows the accurate measurement 
of both the DUT and thc source reflection coerlicient, but 
- again - two distinct acquisition steps arc necessary. 
This paper describes a novel solution based on a thrce- 
sampler vector network analyzer (VNA). The test-set is 
shown in figure 2 and it  is analogous to the systems 
described in [ l ,  61. The signal from a microwave 
synthesized source is summed with the wave reflcctcd by 
the tuning clcmerit and injectcd into the DUT. Signal arpl 
is drawn from the generator output to provide a stable 
refcrence to thc receiver and a terminated circuhtor is 
used to guarantee isolation of the microwave synthesizer. 
The main breakthrough is that, after the new 
calibration procedure herc described, the Ineasurements 
of waves a, and b,,, with respect to aryl’ are sufficient to 
determine source and DUT reflection coefficients, 
respectively Ts arid T,. 
The interesting; features of the novel technique are: 
* a new model for the input retlectoIncter, which 
extcnd the well-known err-or-box concept [8]; 
a new calibration procedure, based on traditional one 
port standard devices; 
simultaneous measurements of the source and the 
DUT gammas; in particular: 
0 it is not necessary to disconnect the DUT to 
measure the source gamma; 
e it is not necessary to switch the microwave source 
off, nor to disconnect it. 
2. Calibration procedure 
2.1. Theoretical aspects 
The novel error model is shown in figure 3. The flow 
graphs of figure 3a and 3b are derived from classical 
load-pull theory [9], [lo]. They allow to link the waves a ,  
b at the DUT reference plane with the measured 
quantities a,,,, b,x and, simultaneously, the same a,  b with 
the wave a,, b, at the tuner plane T-T’ (see figure 2). 
Flow graph of figure 3c represents the key point of the 
new model. The waves at the tuner plane (ar, b,) when the 
source is turned on are written as a linear function of all 
three measured quantities, a,,,, 6, and This leads to a 
novel concept of error-box, which extends the original 
idea to include the source terms represented by urd 
Figure 3. Error model. 
131 
2.2. Calibration sequence and de-embedding 
Table 1 shows the connection sequence of the 
standard devices whose measurements are sufficient to 
compute all the error coefficients. The entire set of 
connections is divided into two subsets. First, source is 
plugged to section S-S’ and standard connections from 1 
to 6 are made. Afterwards, the microwave source is 
turned to the DUT port and three additional standards are 
connected to shift the reference plane from section T-T’ 
to D-D’. 
1 
2 
3 
4 
5 
6 
7 
8 
9 
~ 
- __ 
DUT plane 
SHORT 
SHORT 
SHORT 
OPEN 
OPEN 
LOAD 
D - D ’  
source 
source 
source 
Tuner plane Source plane 
SHORT source 
source 
LOAD source 
SHORT source ! LOAD source 
source 4%k+-Er 
Fable 1. Sequence of standard devices and 
relative position of the microwave source 
signal. 
De-embedding is carried out in three distinct steps: 
1. DUT reflection coefficient rL at section D-D’ is 
computed by the error coefficient of figure 3b; 
2. tuner reflection coefficient Tt at section T-T’ is 
computed by the error box of figure 3a; 
3. the same Tt is shifted to the DUT reference plane D- 
D’; the result is proved to be the source reflection 
coefficient rs. 
3. Experimental results 
Measurement results are shown in figures from 4 to 6. 
Source reflection coefficient is limited in magnitude, 
since a simple passive tuner was used. To validate the 
novel technique, various gammas source were measured 
under different conditians. For each tuner position: 
first gamma source was directly measured with a 
VNA at DUT port and the source switched off, 
yielding Tss.o; 
then, a short was connected to the DUT port to 
simulate an high-impedance device and gamma 
source was computed by the described technique at 
two different source output power levels (10 and 0 
dBm), obtaining respectively rS,, and l-s,2. 
Results computed for a single tuner setting are shown 
in figure 4 as a function of frequency. l-s,l and rs,2 plots 
overlap, proving that the technique de-embeds the same 
Ts for different values of stimulus as. Moreover, they 
show only small differences with respect to Ts,o, as 
pointed out in figure 5. Finally, figure 6 shows various 
source gammas obtained at single frequency for different 
tuner positions. 
4. Conclusions 
A new calibration technique has been presented, 
which allows to obtain simultaneous corrected 
measurements of the source and the device input 
impedance for fast microwave characterization. 
Experimental results prove the accuracy of the proposed 
method against the traditional techniques. 
References 
[I1 
121 
[31 
141 
151 
[61 
171 
181 
D.L. Le and F.M. Ghannouchi, “Noise measurements of 
microwave transistor using and uncalibrated mechanical 
stub tuner and a built-in reverse six-port reflectometer,” 
IEEE Trans. Instrument Meas., vol. IM-44, pp.847-852, 
Aug. 1995. 
F.M. Ghannouchi and R. Bosisio, “Source-pull/load-pull 
oscillator measurements at microwave/mm wave 
frequencies,” IEEE Trans. Microwave Theory Tech., vol. 
MTT-41, pp. 32-35, Feb. 1992. 
D.L. Le and F.M. Ghannouchi, “Multitone 
characterization and design of FET resistive mixers based 
on combined active source-pull/load-pull techniques,” 
IEEE Trans. Microwave Theory Tech., vol. M’IT-46, pp. 
1201-1208, Sep. 1998. 
C. Tsironis, “A novel design method of wideband power 
amplifier,” Microwave J., pp. 303-304, May 1992. 
G.P. Bava, U. Pisani and V. Pozzolo, “’Source pull’ 
technique at microwave frequencies,” Electronic Lett., 
vo1.20, n.4, pp. 152-154, Feb. 1984. 
G. Berghoff, E. Bergeault, B. Huyart and L. Jallet, 
“Automated characterization of HF power transistor by 
source-pull and multiharmonic load-pull measurements 
based on six-port techniques,” IEEE Trans. Microwave 
Theory Tech., vol. M’IT-46, pp. 2068-2073, Dec. 1998. 
D.L. Le, P. Poire and F.M. Ghannouchi, “Six-port-based 
active source-pull measurement technique,” 
Meas.Sci.Technol., vo1.9, pp. 1336-1342, Aug. 1998. 
H.J.Eu1 and BSchieck, “A generalized theory and new 
calibration procedures for network analyzer self- 
calibration,” IEEE Trans. Microwave Theory Tech., vol. 
M’IT-39, pp. 724-731, Apr. 1991. 
132 
[9] I. Hecht, “Improved error-correction technique for large- [ 101 A. Ferrero and U. Pisani, “An improved calibration 
signal load-pull measurement,” IEEE Trans. Microwave technique for on-wafer large-signal trarisistor 
Theory Tech., vol. MTT-35, pp. 1060-1062, Nov. 19E7. characterization,” IEEE Trans. Instr. Meas., vol. IIM-42, 
PP. 360-364, Apr. 1993. 
8 9 10 11 12 13 14 15 16 
Frequency [GHz] 
Figure 4. Source gamma for tuner position 2 
(see also figure 6): rs,o (VNA: 0), Ts,, (new 
technique, with source power at 10 dBm: V), 
Ts,2 (new technique, with source power ait 0 
dBm: 0). 
4 
...... ........................ 
10 
!mo/yh*N -1 
.........,... 
-2 I , 
Frequency [GHz] 
Figure 6. Source reflection coefficient at 
12GHz for various tuner positions 
computed by different techniques: 
Ts,o (VNA: o), Ts,, (new technique, with 
source power at 10 dBm: V). 
Squares (a) represent the corresponding 
tuner input gamma at section T-’T’: 
reflectometer attenuation and phase shift 
are evident. 
Figure 5. Differences between source 
gammas comiputed by different techniques. 
Degradation of phase accuracy is evident for 
lr,l < 20 dEl, where phase is no more 
significant. 
133 


A novel design method of wideband power

Automated characterization of HF power transistor by source-pull and multiharmonic load-pull measurements based on six-port techniques,”

Improved error-correction technique for large-

Multitone characterization and design of FET resistive mixers based on combined active source-pull/load-pull techniques,”

Noise measurements of microwave transistor using and uncalibrated mechanical stub tuner and a built-in reverse six-port reflectometer,”

Six-port-based active source-pull measurement technique,”

Source pull’ technique at microwave frequencies,”

Testing devices under different source impedances: a novel technique for on-line measurement of source and device reflection coefficients

G. L. Madonna

PISANI, Umberto

04 August 2020POLITECNICO DI TORINORepository ISTITUZIONALETesting devices under different source impedances: a novel technique for on-line measurement of source and devicereflection coefficients / G. L. Madonna; M. Pirola; A. Ferrero; U. Pisani. - STAMPA. - 1(1999), pp. 130-133. ((Interventopresentato al convegno IMTC, Instrumentation and Measurement Technology Conference tenutosi a Venezia (Italia) nel24-26 May 1999.OriginalTesting devices under different source impedances: a novel technique for on-line measurement ofsource and device reflection coefficientsPublisher:PublishedDOI:10.1109/IMTC.1999.776733Terms of use:openAccessPublisher copyright(Article begins on next page)This article is made available under terms and conditions as specified in the  corresponding bibliographic description inthe repositoryAvailability:This version is available at: 11583/2497920 since:Testing Microwave Devices under Different Source Impedances: a Novel Technique for On-Line Measurement of Source and Device Reflection Coefficients G.L.Madonna, M.Pirola, A.Ferrero and U.Pisani Dipartimento di Elettronica Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy ferrero @polito.it Abstract This paper describes a new approach for fast and accurate determination of the source reflection coefficient in microwave source-pull measurements. To the authors' knowledge, this is the only technique that allows the simultaneous measurement of the source and the DUT gammas. A traditional vector network analyzer is used as a three-channel receiver. The calibration procedure is based on a new rejlectometer model that extends the traditional error box concept. Experimental results are presented and compared to data obtained with traditional techniques. 1. Introduction Microwave source-pull measurement techniques consist in monitoring the desired performance of a device under test (DUT) while driving it with different source impedances. This approach is widely used for microwave active device characterization, both in small and large signal conditions. A typical application is low noise amplifier (LNA) design to experimentally obtain the optimum noise impedance [l] or the matching network for mixers, oscillators and high efficiency amplifiers To complete an accurate characterization of the DUT in a reasonable time, both automatic source impedance setting and measurement capabilities are mandatory. Different systems have been proposed for the former need, based on either passive tuners [2, 41 or active-load techniques [3, 5 - 71. This paper mainly deals with the second topic, i.e. the fast and accurate determination of the source impedance along with the measurement of the DUT input characteristics. [2 - 41. 130 The well-known problem definition is shown in figure 1. Traditional measurement systems are able to obtain calibrated values of a and b and their ratio r, ,b a On the other side, the source reflection coefficient we are looking for is defined as and it is equal to ratio a/b  only if a, = 0 ,  i.e. the internal generator is switched off. A simple technique consists in switching the microwave generator off and measuring the equivalent source reflection coefficient by exciting the test-set back from the DUT port. This solution is accurate, but it cannot be used for automatic characterization since it requires disconnecting the DUT at each tuner position. Figure 1. Definition of the problem. TUNABLE LOAD @ bt D + a  - b  D MICROWAVE SOURCE Figure 2. Simplified block scheme of the source-pull imeasurement test-set. A completely #different approach is described in [ I ] ,  whcrc the reflection coefficient of the tuning elerrlent is continuously moriitorcd by a six-port reflectometer in reverse configuration. This technique is both accurate and suitable for automatic source pulling; however, the problem is just diverted, since now it  is the DUT reflection coefficient that cannot be determined. The solution recently proposed in [6] is probably the most effective, since it allows the accurate measurement of both the DUT and thc source reflection coerlicient, but - again - two distinct acquisition steps arc necessary. This paper describes a novel solution based on a thrce- sampler vector network analyzer (VNA). The test-set is shown in figure 2 and it  is analogous to the systems described in [ l ,  61. The signal from a microwave synthesized source is summed with the wave reflcctcd by the tuning clcmerit and injectcd into the DUT. Signal arpl is drawn from the generator output to provide a stable refcrence to thc receiver and a terminated circuhtor is used to guarantee isolation of the microwave synthesizer. The main breakthrough is that, after the new calibration procedure herc described, the Ineasurements of waves a, and b,,, with respect to aryl’ are sufficient to determine source and DUT reflection coefficients, respectively Ts arid T,. The interesting; features of the novel technique are: * a new model for the input retlectoIncter, which extcnd the well-known err-or-box concept [8]; a new calibration procedure, based on traditional one port standard devices; simultaneous measurements of the source and the DUT gammas; in particular: 0 it is not necessary to disconnect the DUT to measure the source gamma; e it is not necessary to switch the microwave source off, nor to disconnect it. 2. Calibration procedure 2.1. Theoretical aspects The novel error model is shown in figure 3. The flow graphs of figure 3a and 3b are derived from classical load-pull theory [9], [lo]. They allow to link the waves a ,  b at the DUT reference plane with the measured quantities a,,,, b,x and, simultaneously, the same a,  b with the wave a,, b, at the tuner plane T-T’ (see figure 2). Flow graph of figure 3c represents the key point of the new model. The waves at the tuner plane (ar, b,) when the source is turned on are written as a linear function of all three measured quantities, a,,,, 6, and This leads to a novel concept of error-box, which extends the original idea to include the source terms represented by urd Figure 3. Error model. 131 2.2. Calibration sequence and de-embedding Table 1 shows the connection sequence of the standard devices whose measurements are sufficient to compute all the error coefficients. The entire set of connections is divided into two subsets. First, source is plugged to section S-S’ and standard connections from 1 to 6 are made. Afterwards, the microwave source is turned to the DUT port and three additional standards are connected to shift the reference plane from section T-T’ to D-D’. 1 2 3 4 5 6 7 8 9 ~ - __ DUT plane SHORT SHORT SHORT OPEN OPEN LOAD D - D ’  source source source Tuner plane Source plane SHORT source source LOAD source SHORT source ! LOAD source source 4%k+-Er Fable 1. Sequence of standard devices and relative position of the microwave source signal. De-embedding is carried out in three distinct steps: 1. DUT reflection coefficient rL at section D-D’ is computed by the error coefficient of figure 3b; 2. tuner reflection coefficient Tt at section T-T’ is computed by the error box of figure 3a; 3. the same Tt is shifted to the DUT reference plane D- D’; the result is proved to be the source reflection coefficient rs. 3. Experimental results Measurement results are shown in figures from 4 to 6. Source reflection coefficient is limited in magnitude, since a simple passive tuner was used. To validate the novel technique, various gammas source were measured under different conditians. For each tuner position: first gamma source was directly measured with a VNA at DUT port and the source switched off, yielding Tss.o; then, a short was connected to the DUT port to simulate an high-impedance device and gamma source was computed by the described technique at two different source output power levels (10 and 0 dBm), obtaining respectively rS,, and l-s,2. Results computed for a single tuner setting are shown in figure 4 as a function of frequency. l-s,l and rs,2 plots overlap, proving that the technique de-embeds the same Ts for different values of stimulus as. Moreover, they show only small differences with respect to Ts,o, as pointed out in figure 5. Finally, figure 6 shows various source gammas obtained at single frequency for different tuner positions. 4. Conclusions A new calibration technique has been presented, which allows to obtain simultaneous corrected measurements of the source and the device input impedance for fast microwave characterization. Experimental results prove the accuracy of the proposed method against the traditional techniques. References [I1 121 [31 141 151 [61 171 181 D.L. Le and F.M. Ghannouchi, “Noise measurements of microwave transistor using and uncalibrated mechanical stub tuner and a built-in reverse six-port reflectometer,” IEEE Trans. Instrument Meas., vol. IM-44, pp.847-852, Aug. 1995. F.M. Ghannouchi and R. Bosisio, “Source-pull/load-pull oscillator measurements at microwave/mm wave frequencies,” IEEE Trans. Microwave Theory Tech., vol. MTT-41, pp. 32-35, Feb. 1992. D.L. Le and F.M. Ghannouchi, “Multitone characterization and design of FET resistive mixers based on combined active source-pull/load-pull techniques,” IEEE Trans. Microwave Theory Tech., vol. M’IT-46, pp. 1201-1208, Sep. 1998. C. Tsironis, “A novel design method of wideband power amplifier,” Microwave J., pp. 303-304, May 1992. G.P. Bava, U. Pisani and V. Pozzolo, “’Source pull’ technique at microwave frequencies,” Electronic Lett., vo1.20, n.4, pp. 152-154, Feb. 1984. G. Berghoff, E. Bergeault, B. Huyart and L. Jallet, “Automated characterization of HF power transistor by source-pull and multiharmonic load-pull measurements based on six-port techniques,” IEEE Trans. Microwave Theory Tech., vol. M’IT-46, pp. 2068-2073, Dec. 1998. D.L. Le, P. Poire and F.M. Ghannouchi, “Six-port-based active source-pull measurement technique,” Meas.Sci.Technol., vo1.9, pp. 1336-1342, Aug. 1998. H.J.Eu1 and BSchieck, “A generalized theory and new calibration procedures for network analyzer self- calibration,” IEEE Trans. Microwave Theory Tech., vol. M’IT-39, pp. 724-731, Apr. 1991. 132 [9] I. Hecht, “Improved error-correction technique for large- [ 101 A. Ferrero and U. Pisani, “An improved calibration signal load-pull measurement,” IEEE Trans. Microwave technique for on-wafer large-signal trarisistor Theory Tech., vol. MTT-35, pp. 1060-1062, Nov. 19E7. characterization,” IEEE Trans. Instr. Meas., vol. IIM-42, PP. 360-364, Apr. 1993. 8 9 10 11 12 13 14 15 16 Frequency [GHz] Figure 4. Source gamma for tuner position 2 (see also figure 6): rs,o (VNA: 0), Ts,, (new technique, with source power at 10 dBm: V), Ts,2 (new technique, with source power ait 0 dBm: 0). 4 ...... ........................ 10 !mo/yh*N -1 .........,... -2 I , Frequency [GHz] Figure 6. Source reflection coefficient at 12GHz for various tuner positions computed by different techniques: Ts,o (VNA: o), Ts,, (new technique, with source power at 10 dBm: V). Squares (a) represent the corresponding tuner input gamma at section T-’T’: reflectometer attenuation and phase shift are evident. Figure 5. Differences between source gammas comiputed by different techniques. Degradation of phase accuracy is evident for lr,l < 20 dEl, where phase is no more significant. 133 

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Testing devices under different source impedances: a novel technique for on-line measurement of source and device reflection coefficients

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