WO1988008969A1 - Method for measurement of amplifier s parameters - Google Patents

Method for measurement of amplifier s parameters Download PDF

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Publication number
WO1988008969A1
WO1988008969A1 PCT/US1988/001525 US8801525W WO8808969A1 WO 1988008969 A1 WO1988008969 A1 WO 1988008969A1 US 8801525 W US8801525 W US 8801525W WO 8808969 A1 WO8808969 A1 WO 8808969A1
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WO
WIPO (PCT)
Prior art keywords
load
input
loads
output
under test
Prior art date
Application number
PCT/US1988/001525
Other languages
French (fr)
Inventor
Mark D. Roos
Original Assignee
Eip Microwave, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Eip Microwave, Inc. filed Critical Eip Microwave, Inc.
Publication of WO1988008969A1 publication Critical patent/WO1988008969A1/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N22/00—Investigating or analysing materials by the use of microwaves or radio waves, i.e. electromagnetic waves with a wavelength of one millimetre or more
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/28—Measuring attenuation, gain, phase shift or derived characteristics of electric four pole networks, i.e. two-port networks; Measuring transient response
    • G01R27/32—Measuring attenuation, gain, phase shift or derived characteristics of electric four pole networks, i.e. two-port networks; Measuring transient response in circuits having distributed constants, e.g. having very long conductors or involving high frequencies

Definitions

  • the present invention relates generally to microwave measurement and more particularly to the measurement of phase and amplitude transfer characteristics of an active microwave device such as an amplifier.
  • S parameters of amplifiers may be determined through utilization of currently used network analyzer systems. These systems, however, require the amplifier be connected, measurements taken, the amplifier disconnected, reversed and re-connected after which additional measurements are taken. Even when following these procedures, as a result of the manner in which the standard network analyzers operate, the accuracy of all of the S parameters is limited and typically no results are obtained for S12 or S22.
  • a source of electromagnetic energy is connected to the input of a device under test and measurements are taken of the input and reflected power at both the input and the output of the device under test while the device is terminated by first and second unknown loads to obtain first and second sets of measured values which are then utilized to calculate the S parameters of the device under test.
  • FIGURE l is a schematic block diagram illustrating an apparatus for practicing the method of the present invention.
  • FIGURE 2 illustrates one form of load which can be utilized to terminate the device under test.
  • an active device under test (DUT) 10 has connected to its input terminal 12 a measuring device such as a head 14 which is capable of measuring the energy applied to the device under test as well as the reflected energy.
  • a measuring device such as a head 14 which is capable of measuring the energy applied to the device under test as well as the reflected energy.
  • an additional measuring head 18 is also capable of measuring the output signal of the DUT as well as reflected energy.
  • a source 20 of electromagnetic energy is provided and applies to the conductor 22 a source of electromagnetic energy signal which preferably is constant and maintained so throughout the time all measurements are taken. While the signal (electromagnetic energy) is applied through the head 14 to the input terminal 12 of the device under test which is typically a microwave amplifier, an output signal is generated by the DUT 10 and appears at the output terminal 16. This output signal is applied to the head 18 which has an output terminal 24 which is terminated by either a load 26 or a load 28, the exact value of which is typically unknown. The loads 26 and 28 are alternately connected to the terminal 24 by a switching means 30. During the time that the load 26 is connected to the terminal 24 of the head 18 the input signal from the source 20 is measured and a measured value is provided at the terminal 32.
  • the reflected energy from the amplifier 10 input terminal is measured by the head 14 and provides an output measured value at the terminal34 .
  • the output signal from the amplifier 10 is measured and provides a measured value at the terminal 36 of the head 18, while the reflected energy from the load 26 is measured at the terminal 38 to provide an additional measured value. Typically all four of these measured values are obtained simultaneously.
  • the switch 30 is changed to terminate the DUT 10 with the load 28 which will be different from the load 26 and preferably will have a variation of approximately 10% with respect to the value of the load 26.
  • each of the loads 26 and 28 have a low power reflection characteristic. While the switch 30 is connected to the load 28 the measurements again are made as above described providing a second set of measured values at the terminals 32 through 38 while the device under test is terminated by the load 28.
  • Mason's Gain Rule is then used to determine equations relative to the S parameters S11, S12, S21 and S22. Thereafter normal linear algebra is utilized to solve the equations for the S parameters. Since Mason's Gain Rule and linear algebra are well known to those skilled in the art, no further explanation or description is believed necessary herein.
  • the loads 26 and 28 may take is a PIN diode as is shown in FIGURE 2.
  • the diode 40 is connected to a bias source at the terminal 42 through a resistor 44.
  • the cathode of the PIN diode 40 is connected to ground, as is illustrated, while the anode is connected to the terminal 24.
  • a lossy pad 46 is also connected between the anode of the PIN diode 40 and the terminal 24 to maintain the reflection characteristics of the diode 40 low.
  • the bias applied to the terminal 42 is positive the diode 40 will be effectively a short circuit and would, for example, represent the load 26. Thereafter the bias would be changed to a reverse bias on the diode 40 and it would effectively appear as an open circuit and would represent the load 28.
  • the application of the bias may be controlled by an appropriate electronic switching control circuit represented schematically by the switch 30.
  • the terminals 32 through 38 may, for example, be connected to an appropriate microprocessor 48 which is properly programmed to utilize Mason's Gain Rule and the linear algebra to solve and provide the S parameters for the device under test and if desired display them on an appropriate display 50 such as a screen or printout.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
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  • Pathology (AREA)
  • Amplifiers (AREA)

Abstract

A constant power source (20) of electromagnetic energy is applied to a device under test (10). The device under test (10) is terminated alternately by first and second unknown loads (26, 28) having a low power reflection characteristic. While the device is terminated by each of the loads the input and reflected power at the input (14) and output (18) terminals of the device under test (10) is measured to obtain first and second sets of measured values. The measured values are then used to calculate the S-parameters of the device under test.

Description

METHOD FOR MEASUREMENT OF AMPLIFIER S PARAMETERS
Background of the Invention The present invention relates generally to microwave measurement and more particularly to the measurement of phase and amplitude transfer characteristics of an active microwave device such as an amplifier.
As system requirements become more and more stringent it becomes necessary to more accurately ascertain the true characteristics of an active device in a microwave system such for example as an amplifier. In the past the exact characteristics have typically only been obtainable in laboratory apparatus utilized traditionally during the design of the microwave amplifiers. Such measurements have been made utilizing a technique characterized as the load pull technique which provides accurate results but is very time consuming and difficult to calibrate. Therefore, the technique is seldom, if ever, used during manufacture to test the characteristics of production amplifiers.
S parameters of amplifiers may be determined through utilization of currently used network analyzer systems. These systems, however, require the amplifier be connected, measurements taken, the amplifier disconnected, reversed and re-connected after which additional measurements are taken. Even when following these procedures, as a result of the manner in which the standard network analyzers operate, the accuracy of all of the S parameters is limited and typically no results are obtained for S12 or S22.
Summary of the Invention
A source of electromagnetic energy is connected to the input of a device under test and measurements are taken of the input and reflected power at both the input and the output of the device under test while the device is terminated by first and second unknown loads to obtain first and second sets of measured values which are then utilized to calculate the S parameters of the device under test.
Brief Description of the Drawings
FIGURE l is a schematic block diagram illustrating an apparatus for practicing the method of the present invention; and
FIGURE 2 illustrates one form of load which can be utilized to terminate the device under test.
Detailed Description As is shown in FIGURE 1 an active device under test (DUT) 10 has connected to its input terminal 12 a measuring device such as a head 14 which is capable of measuring the energy applied to the device under test as well as the reflected energy. Connected to the output terminal 16 of the device under test 10 is an additional measuring head 18 which is also capable of measuring the output signal of the DUT as well as reflected energy.
A source 20 of electromagnetic energy is provided and applies to the conductor 22 a source of electromagnetic energy signal which preferably is constant and maintained so throughout the time all measurements are taken. While the signal (electromagnetic energy) is applied through the head 14 to the input terminal 12 of the device under test which is typically a microwave amplifier, an output signal is generated by the DUT 10 and appears at the output terminal 16. This output signal is applied to the head 18 which has an output terminal 24 which is terminated by either a load 26 or a load 28, the exact value of which is typically unknown. The loads 26 and 28 are alternately connected to the terminal 24 by a switching means 30. During the time that the load 26 is connected to the terminal 24 of the head 18 the input signal from the source 20 is measured and a measured value is provided at the terminal 32. The reflected energy from the amplifier 10 input terminal is measured by the head 14 and provides an output measured value at the terminal34 . At the same time, the output signal from the amplifier 10 is measured and provides a measured value at the terminal 36 of the head 18, while the reflected energy from the load 26 is measured at the terminal 38 to provide an additional measured value. Typically all four of these measured values are obtained simultaneously.
Thereafter the switch 30 is changed to terminate the DUT 10 with the load 28 which will be different from the load 26 and preferably will have a variation of approximately 10% with respect to the value of the load 26. Preferably also each of the loads 26 and 28 have a low power reflection characteristic. While the switch 30 is connected to the load 28 the measurements again are made as above described providing a second set of measured values at the terminals 32 through 38 while the device under test is terminated by the load 28.
Utilizing these measured values, Mason's Gain Rule is then used to determine equations relative to the S parameters S11, S12, S21 and S22. Thereafter normal linear algebra is utilized to solve the equations for the S parameters. Since Mason's Gain Rule and linear algebra are well known to those skilled in the art, no further explanation or description is believed necessary herein.
One form which the loads 26 and 28 may take is a PIN diode as is shown in FIGURE 2. As is therein illustrated the diode 40 is connected to a bias source at the terminal 42 through a resistor 44. The cathode of the PIN diode 40 is connected to ground, as is illustrated, while the anode is connected to the terminal 24. A lossy pad 46 is also connected between the anode of the PIN diode 40 and the terminal 24 to maintain the reflection characteristics of the diode 40 low. When the bias applied to the terminal 42 is positive the diode 40 will be effectively a short circuit and would, for example, represent the load 26. Thereafter the bias would be changed to a reverse bias on the diode 40 and it would effectively appear as an open circuit and would represent the load 28. Obviously the application of the bias may be controlled by an appropriate electronic switching control circuit represented schematically by the switch 30. It will also be obvious to those skilled in the art that the terminals 32 through 38 may, for example, be connected to an appropriate microprocessor 48 which is properly programmed to utilize Mason's Gain Rule and the linear algebra to solve and provide the S parameters for the device under test and if desired display them on an appropriate display 50 such as a screen or printout.

Claims

WHAT IS CLAIMED IS:
1. A method of measuring the S parameters of a device having an input and an output comprising: connecting an electromagnetic signal to the input of said device; connecting a first unknown load to the output of said device; measuring the input and reflected power of said signal at said input and said output of said device with said first load connected to obtain a first set of measured values; connecting a second unknown load to the output of said device; measuring the input and reflected power of said input and said output of said device with said second load connected to obtain a second set of measured values; and calculating the S parameters using said first and second sets of measured values.
2. The method as defined in claim 1 wherein said unknown loads are connected by switching between said first and second loads.
3. The method as defined in claim 1 wherein said first and second loads include a PIN diode which is forward biased to serve as one of said first and second loads and is reverse biased to serve as the other of said first and second loads.
4. The method as defined in claim 1 wherein the power of said applied signal is maintained constant throughout said measurements.
5. The method as defined in claim 1 wherein said first and second loads have low power reflection characteristics.
6. The method as defined in claim 1 wherein said measurements are taken simultaneously while said first load is connected and simultaneously while said second load is connected.
PCT/US1988/001525 1987-05-15 1988-05-03 Method for measurement of amplifier s parameters WO1988008969A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US5081987A 1987-05-15 1987-05-15
US050,819 1987-05-15

Publications (1)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1296149A1 (en) * 2001-09-24 2003-03-26 Agilent Technologies, Inc. (a Delaware corporation) Characterizing non-linear behavior
CN104459339A (en) * 2013-09-25 2015-03-25 特克特朗尼克公司 Two-port vector network analyzer using de-embedding probes

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4680538A (en) * 1985-01-15 1987-07-14 Cornell Research Foundation, Inc. Millimeter wave vector network analyzer

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4680538A (en) * 1985-01-15 1987-07-14 Cornell Research Foundation, Inc. Millimeter wave vector network analyzer

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
ELECTRONIC INSTRUMENTS AND SYSTEMS: HEWLETT PACKARD MEASUREMENT COMPUTATION, 1983, pp. 428-429. See "High Frequency Network Analysis", and "Additional Capabilities". *
ELECTRONIC MEASUREMENTS AND INSTRUMENTATION, 1971, (OLIVER et al.), pp 671 703. See entire reference. *
H/P JOURNAL, February 1967, "S-Parameter Techniques for Faster, More Accurate Network Design", pp 13-23. See entire reference. *
IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT, Vol. IM-26, No. 2, June 1977, (KOTZEBUE), "A New Technique for the Direct Measurement of Y Parameters as Microwave Frequencies", pp 119-123. See entire reference. *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1296149A1 (en) * 2001-09-24 2003-03-26 Agilent Technologies, Inc. (a Delaware corporation) Characterizing non-linear behavior
US6839657B2 (en) 2001-09-24 2005-01-04 Agilent Technologies, Inc. Method of and an arrangement for characterizing non-linear behavior of RF and microwave devices in a near matched environment
CN104459339A (en) * 2013-09-25 2015-03-25 特克特朗尼克公司 Two-port vector network analyzer using de-embedding probes
EP2853911A1 (en) * 2013-09-25 2015-04-01 Tektronix, Inc. Two port vector network analyzer using de-embed probes

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Publication number Publication date
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