Electromagnetic compatibility multi-carrier immunity testing system and method

Provided for in some embodiments is, a method of electromagnetic compatibility multi-carrier immunity testing. The method includes generating a first carrier frequency set including a first plurality of carrier frequencies simultaneously such that a device under test is subjected to the first plurality of carrier frequencies simultaneously. One or more of the first plurality of carrier frequencies is substantially different from other ones of the first plurality of carrier frequencies such that the first plurality of carrier frequencies do not interfere with one another when they are generated simultaneously, and intermodulation products of the first plurality of carrier frequencies are not significant relative to the first plurality of carrier frequencies when the first plurality of carrier frequencies are generated simultaneously.

BACKGROUND

1. Field of the Invention

The present invention relates to electromagnetic compatibility (EMC) immunity testing, and more particularly to electromagnetic compatibility (EMC) immunity testing using multiple carrier frequencies simultaneously.

2. Description of the Related Art

Radio frequency (RF) signals are becoming increasing more prevalent in our environment. Often RF signals are generated by electronic devices, such as radio and cellular communication devices. As a result, most devices are expected to operate in these environments despite being subjected to various radio frequency (RF) signals. To help design for use in these environments, electronic devices are typically subjected to tests that that replicate these environmental conditions in an attempt to identify compatibility issues and improve performance. For instance, devices may be required to undergo electromagnetic compatibility (EMC) immunity test to verify operation of the device while it is exposed to signals that may create electromagnetic interference (EMI).

Electromagnetic compatibility testing (EMC) and similar testing techniques typically include subjecting a device under test (DUT) to a sweep of test signals in a given frequency range. The frequency range may be exemplary of signals that the device is expected to encounter during use. During testing, a DUT may be isolated in a test chamber and subjected to a sweep through a series of carrier frequencies, one at a time, across the given frequency range. During the sweep through each carrier frequency, the DUT may be monitored to determine whether or not each of the frequencies affects the DUT's operation. A particular sweep may include subjecting the DUT to several hundred individual carrier frequencies in series, one at a time. In some instances, the DUT may be subjected to a sweep of 255 carrier frequencies within a range of about 80 Mega-hertz (MHz) to about 1 Giga-hertz (GHz). Unfortunately, sweeping through multiple frequencies in series, one at a time, can take a considerable amount of time, resulting in increased cost, as well as delays in design, testing and production.

Thus, improved systems and methods for electromagnetic compatibility (EMC) immunity testing are desired.

SUMMARY OF THE INVENTION

The following describes various systems and methods for electromagnetic compatibility multi-carrier testing. In one embodiment, provided is a method of electromagnetic compatibility multi-carrier immunity testing. The method includes generating a first carrier frequency set including a first plurality of carrier frequencies simultaneously such that a device under test is subjected to the first plurality of carrier frequencies simultaneously. One or more of the first plurality of carrier frequencies is substantially different from other ones of the first plurality of carrier frequencies such that the first plurality of carrier frequencies do not interfere with one another when they are generated simultaneously. Further, intermodulation products of the first plurality of carrier frequencies are not significant relative to the first plurality of carrier frequencies when the first plurality of carrier frequencies are generated simultaneously.

In another embodiment, provided is a memory storage medium having program instructions for performing electromagnetic compatibility multi-carrier immunity testing stored thereon, wherein the program instructions are executable to implement generating a first plurality of carrier frequencies simultaneously such that a device under test is subjected to the first plurality of carrier frequencies simultaneously. One or more of the plurality of carrier frequencies is substantially different from other ones of the first plurality of carrier frequencies such that the first plurality of carrier frequencies do not interfere with one another when they are generated simultaneously, and intermodulation products of the first plurality of carrier frequencies are not significant relative to the first plurality of carrier frequencies when the first plurality of carrier frequencies are generated simultaneously.

In yet another embodiment, provided is a electromagnetic immunity testing system that includes a generator configured to subject a device under test to a plurality of carrier frequencies simultaneously, wherein quarter-wavelengths of one or more of the plurality of carrier frequencies is substantially different from quarter-wavelengths of others of the plurality of carrier frequencies such that the plurality of carrier frequencies do not interfere with one another when they are generated simultaneously, and intermodulation products of the plurality of carrier frequencies are not significant relative to the plurality of carrier frequencies when they are generated simultaneously.

In yet another embodiment, provided is a computer-implemented method of electromagnetic compatibility immunity testing. The method includes, assessing, by a computer, an initial forward power associated with a first carrier frequency of a plurality of carrier frequencies, wherein the initial forward power is configured to generate a field strength. Assessing, by the computer, a first subset of carrier frequencies of the plurality of carrier frequencies, wherein the first subset comprises the first carrier frequency, the first carrier frequency is substantially different from others ones of the first plurality of carrier frequencies of the first subset such that the plurality of carrier frequencies of the first subset do not interfere with one another when the plurality of carrier frequencies of the first subset are generated simultaneously, and intermodulation products of the first plurality of carrier frequencies of the first subset are not significant relative to the plurality of carrier frequencies of the first subset when the plurality of carrier frequencies of the first subset are generated simultaneously. The method also includes assessing, by the computer, a first adjusted drive level for the first carrier frequency, wherein assessing the adjusted drive level for the first carrier frequency includes generating the first subset of carrier frequencies simultaneously and adjusting a drive level associated with the first carrier frequency to an first adjusted drive level configured generate the initial forward power associated with a first carrier frequency. The method also includes generating the first subset of carrier frequencies simultaneously. Generating the first subset of carrier frequencies simultaneously includes generating the first carrier frequency using the first adjusted drive level to perform electromagnetic compatibility immunity testing of a device under test.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Measurement Device—includes instruments, data acquisition devices, smart sensors, and any of various types of devices that are operable to acquire and/or store data. A measurement device may also optionally be further operable to analyze or process the acquired or stored data. Examples of a measurement device include an instrument, such as a traditional stand-alone “box” instrument, a computer-based instrument (instrument on a card) or external instrument, a data acquisition card, a device external to a computer that operates similarly to a data acquisition card, a smart sensor, one or more DAQ or measurement cards or modules in a chassis, an image acquisition device, such as an image acquisition (or machine vision) card (also called a video capture board) or smart camera, a motion control device, a robot having machine vision, and other similar types of devices. Exemplary “stand-alone” instruments include oscilloscopes, multimeters, signal analyzers, arbitrary waveform generators, spectroscopes, and similar measurement, test, or automation instruments.

A measurement device may be further operable to perform control functions, e.g., in response to analysis of the acquired or stored data. For example, the measurement device may send a control signal to an external system, such as a motion control system or to a sensor, in response to particular data. A measurement device may also be operable to perform automation functions, i.e., may receive and analyze data, and issue automation control signals in response.

Subset—in a set having N elements, the term “subset” comprises any combination of one or more of the elements, up to and including the full set of N elements. For example, a subset of a plurality of signal may be any one signal of the plurality of the signals, any combination of one or more of the signals, or all of the signals in the plurality of signals. Thus, a subset of an entity may refer to any single element of the entity as well as any portion up to and including the entirety of the entity.

FIGS. 1A and 1Billustrate embodiments of a system10configured to implement electromagnetic compatibility (EMC) multi-carrier immunity testing. Embodiments of a method for electromagnetic compatibility (EMC) multi-carrier immunity testing are described below.

As depicted inFIG. 1A, in some embodiments, the system10includes a generator11and a receiver14. The generator11may be used to generate and/or transmit signals that are received at the receiver14. For example, the generator11may include a signal generation device that provides test signals and the receiver14may include a device under test (DUT) that is subjected or otherwise receives the test signals.

In one embodiment, generator11is capable of providing signals used in electromagnetic compatibility (EMC) testing. For example, in one embodiment, generator11may be capable of generating and transmitting various carrier signals that a DUT is ultimately subjected to during EMC testing. In the embodiment illustrated ofFIG. 1A, generator11includes a device capable of providing signals used for radiated radio-frequency (RF) immunity tests. Radiated RF immunity testing may require that the generator11generate RF fields of one or more carrier frequencies, referred to hereafter as “test frequencies.” For example, the generator11may provide an RF field sweep in a range of 80 MHz to 1000 MHz. As described in more detail below, the generator11may be capable of providing a plurality of test frequencies simultaneously.

In the illustrated embodiment, the generator11includes signal generator12, an amplifier20, and a transducer22. In one embodiment, the signal generator12includes a waveform generator16and a frequency synthesizer18. Waveform generator16may include a device, such as an arbitrary waveform generator, that is capable of producing a signal of a given waveform type and frequency. In one embodiment, frequency synthesizer18may include a device for generating any of a range of frequencies from a single fixed timebase or oscillator, such as an upconverter capable of modulating the output of the waveform generator16with a carrier frequency. For example, in one embodiment, such as those in which generator11provides an RF field, the signal generator16may provide a base signal, such as 1 kHz sine or cosine wave, that is input to the frequency synthesizer18, and the frequency synthesizer18may modulate the signal onto an RF carrier signal of a given frequency, such as a carrier signal having a frequency in the range of about 80 MHz to about 1 GHz. Although a base signal including a 1 kHz wave may be used in certain embodiments, other frequencies may be used. For example, the base signal may include another frequency, or a different waveform altogether. Further, although carrier frequencies in the range of about 80 MHz to about 1 GHz may be used in certain embodiments, other embodiments may include various frequencies, ranges of frequencies, and various sweeps through frequency ranges. In one embodiment, the frequency synthesizer18may be capable of generating carrier signals within the range from about 40 MHz to about 300 Ghz.

In the illustrated embodiment, an output of the frequency synthesizer18is provided to an input to the amplifier20. Amplifier20may include a power amplifier that is capable of providing a signal of sufficient output power at the frequency of the input. For example, the amplifier20may amplify the signal power such that it is capable of driving a signal to be transmitted by the transducer22, e.g., an antenna. In an embodiment in which more than one frequency is output by the generator11, such as during a frequency sweep provided during EMC testing, the amplifier20may be capable of providing the desired power output over the entire frequency range of the test. As discussed in more detail below, the amplifier20may be capable of providing enough power to drive multiple signals simultaneously at a desired power level.

In the illustrated embodiment, an output signal of the amplifier20is provided to the transducer22. Transducer22may include a device that is capable of transmitting the amplified signal such that it may be received by the receiver14. In one embodiment, transducer22may include antenna, such as a broadband antenna. In some embodiments, the transducer22may be positioned such that the signals are generated in particular orientation. For example, during ENC testing, an antenna transducer22and/or the receiver14(e.g., a device under test) may be positioned such that the signals are transmitted and/or received in a particular direction relative to the DUT. In one embodiment, the transducer22and the receiver14are both positioned in an anechoic room/chamber23, such as those typically used for electromagnetic immunity testing.

In one embodiment, the receiver14may include one or more devices that receive/sense/detect or are otherwise subjected to the signals provided by the generator11. During EMC testing, for instance, receiver14may include a device under test (DUT), such as a computer, cable, or similar electronic device, that is subjected to the generated sweep of test signals. In one embodiment, receiver14may include a broadband antenna, a field probe, or similar receiving device that is capable of sensing the signals transmitted by generator11. A broadband antenna may include an antenna capable of measuring both magnitude and orientation of a field associated with a received signal. A field probe may include an isotropic probe that is capable of measuring magnitude of a field irrespective of the direction of the field or the orientation of the field probe. In one embodiment, a field probe measures field in each of three orthogonal directions and provides a measurement based on their vector sum in all of the directions.

In one embodiment, a plurality of the receivers14may be provided. For example, a plurality of the receivers14may be exchanged throughout EMC testing. For example, during calibration, the receiver14may include a field probe, broadband antenna, and/or an oscilloscope, and during testing, the receiver14may include the DUT. In some embodiments, multiple receivers14may be provided simultaneously. For example, one or more antennas and/or probes may be positioned in the chamber during calibration, and the antennas and/or probes may remain in the test area while the DUT is being tested. The additional receivers14may be used for calibration, validation, and similar assessments.

In some embodiments, the system10may include devices for the measurement and control of various aspects of the immunity test and test system. In one embodiment, devices may be provided to measure forward power associated with generated RF fields, drive levels, and/or the signature of the RF field at a test location. For example, in the illustrated embodiment, a probe24(e.g., directional coupler) is provided in-line between the amplifier20and the transducer22, and is coupled to measuring devices26(e.g., a spectrum analyzer or power meter). The probe24may enable measuring device26to measure a forward power between the amplifier20and the transducer22. In one embodiment, a field meter28(e.g., a spectrum analyzer or power meter) may be coupled to the transducer22, as depicted. The field meter28may be capable of measuring characteristics (e.g., field strength, frequency, and/or orientation) of the RF field at the receiver14.

In certain embodiments, system10and its associated devices may be controlled manually by an operator, automatically by a controller, or a combination thereof. For example, during manual operation, an operator may make necessary adjustments to the generator11to ensure that it is providing a signal at a given frequency and power. In one embodiment, a controller may be provided to control and/or monitor operation of various components of system10. For example, in the illustrated embodiment, a controller30is coupled to the generator11and the receiver14. In one embodiment, the controller30may include a computer system (e.g., a personal computer) that regulates and monitors at least a portion of their operation. For example, in the illustrated embodiment, controller30may communicate with the signal generator12, the amplifier20, measuring instruments26and/or field meter28to control and monitor various aspects of system10. For example, the controller may execute operations in accordance with stored routines or other inputs (e.g., user input) to manipulate operation of the signal generator12and the amplifier20, and to monitor feedback from the measuring instruments26and field meter28. Such an embodiment may enable system10to operate in a closed loop.

In one embodiment, controller30may be provided as a one or more stand alone units that interface with portions of the signal generator12and/or the receiver14, as depicted inFIG. 1A. In one embodiment, one or more controllers may be provided integral with one or more portions of the signal generator12and/or the receiver14. For example, the signal generator12and/or the receiver14may include an integral computer system that controls at least a portion of their operation. Such a computer system may be used to control various parameters of signals provided by signal generator12and/or may be used to assess signals received by the receiver14. Embodiments of the controller30are discussed in more detail below.

As depicted inFIG. 1B, in one embodiment, signal generator12may include a device that provides signals used for conducted radio-frequency (RF) immunity tests. Conducted RF immunity testing may be well suited for lower frequency signals that are note efficiently and reliably transmitted through the air, for instance. Similar to radiated RF immunity testing, conducted RF immunity testing may require the signal generator12provide RF fields of various frequencies. For example, the signal generator14may generate an RF filed sweep in a range from about 150 kHz to 80 MHz.

Due to the low frequency of test signals that may be associated with conducted RF immunity test, a generated signal may be provided from the signal generator16to the transducer22with little to no manipulation. For example, in the illustrated embodiment, a test signal output from the signal generator16may be routed directly to transducer22. In such an embodiment, signal generator12may not include, or at least may not make use of, a frequency synthesizer and/or an amplifier. In one embodiment, the signal output by the signal generator16may be routed to amplifier20before the transducer22, but may not pass through a frequency synthesizer.

In the illustrated embodiment, the signal generator12may include a transducer that couples to the receiver14(e.g., the device under test). A transducer coupled to the receiver14may be well suited for conducted RF immunity testing. In one embodiment, the transducer22includes an inductive and/or capacitive coupling to the device under test. For example, transducer22may include a clamp that is secured about a portion of a cable under test to provide inductive and/or capacitive coupling. In one embodiment, transducer22may include a current injection probe. A current injection probe may provide inductive coupling without capacitive coupling.

In one embodiment, system10may include a computer system used to control, monitor, regulate, or otherwise interact with system10. For example, in one embodiment, controller30may include a personal computer (PC) system.FIGS. 2A and 2Bdepict exemplary embodiments of a computer system82in accordance with one or more embodiments of the present invention. The computer system82may be analogous to one or more portions of controller30. In one embodiment, the computer system82may include a display device operable to display a graphical user interface for implementing and using embodiments of the present invention. The computer system82may include one or more memory mediums on which one or more computer programs or software components according to one or more embodiments of the present invention may be stored. For example, the memory medium may store one or more programs, e.g., graphical programs, which are executable to perform the methods described herein. Also, the memory medium may store a programming development environment application, e.g., a graphical programming development environment application, used to create and/or execute such programs. For example, in certain embodiments, the programming development environment may facilitate the development of programs that include performance, timing, and I/O constraint information as part of the program. In other words, a programming language provided by the programming development environment may allow such performance, timing, and I/O constraint specifications or criteria to be included in the program itself, e.g., as part of the source code of the program, and/or may be accessed by the program or tools, e.g., profiling tools, to check the program against the criteria, as will be described in more detail below. The memory medium may also store operating system software, as well as other software for operation of the computer system. Various embodiments may include receiving or storing instructions and/or data implemented in accordance with the foregoing description upon a computer-accessible medium.

In one embodiment, computer system82may be coupled to one or more other computer systems. For example, the computer system82may be coupled via a network (or a computer bus) to a second computer system. The computer systems may each be any of various types, as desired. The network can also be any of various types, including a LAN (local area network), WAN (wide area network), the Internet, or an Intranet, among others. The computer systems may execute a program in a distributed fashion. For example, computer82may execute a first portion of the block diagram of a program and the other computer system may execute a second portion of the program. As another example, computer82may display the graphical user interface of a graphical program and the other computer system may execute the block diagram of the graphical program.

FIG. 2Aillustrates an exemplary instrumentation control system100which may implement embodiments of the invention. The system100comprises host computer system82that connects to one or more instruments. The host computer system82may comprise a CPU, a display screen, memory, and one or more input devices such as a mouse or keyboard as shown. The computer system82may operate with the one or more instruments to analyze, measure or control a DUT or process150. According to embodiments of the present invention, one or more of the instruments and devices ofFIG. 2A(andFIG. 2Bdescribed below) may include a programmable hardware element (e.g. an FPGA) configured with a processor and/or memory, and may be further configured with one or more portions of user code, as will be described below in more detail.

The one or more instruments may include a GPIB instrument112and associated GPIB interface card122, a data acquisition board114and associated signal conditioning circuitry124, a VXI instrument116, a PXI instrument118, a video device or camera132and associated image acquisition (or machine vision) card134, a motion control device136and associated motion control interface card138, and/or one or more computer based instrument cards142, among other types of devices. The computer system may couple to and operate with one or more of these instruments. The instruments may be coupled to a device under test (DUT) or process150, or may be coupled to receive field signals, typically generated by transducers. The system100may be used in a data acquisition and control application, in a test and measurement application, an image processing or machine vision application, a process control application, a man-machine interface application, a simulation application, or a hardware-in-the-loop validation application, among others.

FIG. 2Billustrates an exemplary industrial automation system160that may implement embodiments of the invention. The industrial automation system160is similar to the instrumentation or test and measurement system100shown inFIG. 2A. Elements which are similar or identical to elements inFIG. 2Ahave the same reference numerals for convenience. The system160may comprise a computer system82which connects to one or more devices or instruments. The computer system82may comprise a CPU, a display screen, memory, and one or more input devices such as a mouse or keyboard as shown. The computer system82may operate with the one or more devices to a process or device150to perform an automation function, such as MMI (Man Machine Interface), SCADA (Supervisory Control and Data Acquisition), portable or distributed data acquisition, process control, advanced analysis, or other control, among others.

The one or more devices may include a data acquisition board114and associated signal conditioning circuitry124, a PXI instrument118, a video device132and associated image acquisition card134, a motion control device136and associated motion control interface card138, a fieldbus device170and associated fieldbus interface card172, a PLC (Programmable Logic Controller)176, a serial instrument182and associated serial interface card184, or a distributed data acquisition system, such as the Fieldpoint system available from National Instruments Corporation, having headquarters in Austin, Tex., among other types of devices.

FIG. 3is a block diagram representing one embodiment of the computer system82. It is noted that any type of computer system configuration or architecture can be used as desired, andFIG. 4illustrates a representative PC embodiment. It is also noted that the computer system82may be a general-purpose computer system, a computer implemented on a card installed in a chassis, or other types of embodiments. Certain elements of a computer not necessary to understand the present description have been omitted for simplicity.

The computer system82may include at least one central processing unit or CPU (processor)161that is coupled to a processor or host bus162. The CPU161may be any of various types, including an x86 processor, e.g., a Pentium class, a PowerPC processor, a CPU from the SPARC family of RISC processors, as well as others. A memory medium, typically comprising RAM and referred to as main memory,166is coupled to the host bus162by means of memory controller164. As noted above, the main memory166may store a programming development environment, e.g., a graphical programming development environment, as well as one or more programs implementing and/or used in embodiments of the present invention. The main memory166may also store operating system software, as well as other software for operation of the computer system82. The host bus162may be coupled to an expansion or input/output bus170by means of a bus controller168or bus bridge logic. The expansion bus170may be the PCI (Peripheral Component Interconnect) expansion bus, although other bus types can be used. The expansion bus170includes slots for various devices such as described above. The computer system82further comprises a video display subsystem180and hard drive182coupled to the expansion bus170. As depicted, a device190may also be connected to the computer. The device190may include a processor and memory implemented on (e.g., configured on or included in), or coupled to, a programmable hardware element, e.g., an FPGA. The computer system82may be operable to deploy a program, e.g., a graphical program, to the device190for execution of the program on the device190, with respective portions of the program possibly implemented on the programmable hardware element, and stored in the memory for execution by the processor. The device may be any of a variety of device types, such as those described above with reference toFIGS. 2A and 2B.

In some embodiments, the deployed program may take the form of program instructions, e.g., graphical instructions, or data structures that directly represent the program. Alternatively, the deployed program (or a portion of the program) may take the form of text code (e.g., “C” code) generated from a graphical program. As another example, the deployed program (or a portion of the program) may take the form of compiled code generated from either the graphical program or from text code that in turn was generated from the graphical program. The computer system82, e.g., via the programming development environment, may be operable to target, i.e., compile, respective portions of the user code for execution by the processor, and for implementation as hardware on the programmable hardware element, e.g., the FPGA, as needed to meet performance criteria, e.g., resource use, timing, and I/O constraint criteria, and may be further operable to deploy the portions to their respective targets.

FIG. 4illustrates a method200for electromagnetic compatibility (EMC) testing. The method200in one embodiment may be implemented using a test system, such as system10described above. For example, method200may be employed via computer system82to implement some or all portions of method200.

In the exemplary embodiment shown inFIG. 4, illustrated is a method for electromagnetic compatibility (EMC) multi-carrier immunity testing. The method shown inFIG. 5may be used in conjunction with any of the computer systems or devices described herein, among other devices. In various embodiments, some of the method elements shown may be performed concurrently, in a different order than shown, or may be omitted. Additional method elements may also be performed as desired. As shown, this method may operate as follows. In one embodiment, portions of method200may be performed in accordance with certain test standards. For example, in one embodiment, method200may be performed in accordance with International Standard IEC61000-4-3 (Ref. No. CEI/IEC 61000-4-3:2002+A1:2002) which is herein incorporated by reference in its entirety, and/or International Standard IEC61000-4-6 (Ref. No. CEI/IEC 61000-4-6:2003) which is herein incorporated by reference in its entirety. Embodiments may employ a similar version of this or another standard, such as current versions of this or another standard at the time of testing.

In one embodiment, method200includes providing a test carrier frequency set202(hereinafter a test frequency set), based on assessing a test frequency set, as depicted at block204. In one embodiment, assessing a test frequency set may include assessing a frequency range and one or more test frequencies within that range for a given test. For example, in an embodiment that includes EMC testing, a standard may require that a particular test sweep include a test frequency set of several hundred carrier frequencies, such as testing two-hundred fifty-five carrier frequencies in the range of 80 MHz to 1.0 GHz. Other embodiments may include a test frequency set that includes various other radio frequency (RF) ranges. For example, ranges may include lower frequencies, such as 3 Hz, and higher frequencies, such as those up to 300 GHz. In one embodiment, the number of test frequencies in a given test frequency set may be dictated by the test frequency range and a step size, such as a maximum or minimum step size required by the test standard. For example, a standard may require that a step size is less than 1% of the prior frequency. In an embodiment that includes a sweep in a range from 80 MHz to 1.0 GHz, the test frequency set may include 80.00 MHz, 80.80 MHz, 81.61 MHz, 82.42 MHz, 83.25 MHz, and so forth up to a frequency of 1.0 GHz. In such an embodiment, there may be about two-hundred fifty-five test frequencies, in the range of 80 MHz to 1.0 GHz. In one embodiment, test frequency sets may be dictated by a controlling test standard.

In one embodiment, method200includes providing a calibration set206based on calibrating the field, as depicted at block208. Calibrating the field may ensure that the uniformity of the generated field over the test sample is sufficient to ensure the validity of the test results. In other words, calibration of the field may ensure that the DUT is subjected to a field of sufficient power at each carrier frequency during testing. The calibration set206may include one or more values, settings, or the like associated with the system based on the calibration of the field. For example, the calibration set206may include one or more settings/configurations for the signal generator of the system at each of the test frequencies in the test frequency set202. In one embodiment, calibrating the field includes calibrating test levels, e.g., forward power levels, for each test frequency of the test frequency set202. In one embodiment, each frequency is generated individually (e.g., one at a time) and the associated forward power level and associated settings for the system are recorded. For example, in one embodiment, a probe (e.g., a field probe or current probe) is placed in the test setup at or near a location where the DUT will be located during testing. The signal generator is operated to generate a field at one of the test frequencies, settings of the signal generator are adjusted until the required field strength measured by the probe is in accordance with the standards, and a forward power level of the signal generator associated with the generated/required field strength is recorded. These steps may be repeated for each test frequency of the test frequency set202. In one embodiment, the forward power may be measured at an input of the transducer of the signal generator. For example, the forward power may be measured at the probe between the output of the amplifier and the input to the transducer (e.g., antenna) of the signal generator. As discussed in more detail below, the forward power may be referenced at a later time to fine tune the signal generator as various components of the system are exchanged.

In one embodiment, calibrating the field (block208) may include measuring the field strength using another type of a receiver, such as a broadband antenna or a current probe. For example, in an embodiment that includes radiated immunity testing, a broadband antenna may be placed in the test setup at or near a location where the DUT will be located during testing. In an embodiment that includes conducted immunity testing, a current probe may be placed in the test setup in a similar manner as the DUT will be during testing such that it can detect the resulting injected current. For either of radiated or conducted immunity testing, as the signal generator is operated to generate a field/injection current at one of the test frequencies, and settings of the signal generator are adjusted until the required field strength/injected current measured by the receiver is in accordance with the standards, and the field signature (e.g., field strength in multiple direction sensed by the broadband antenna) is recorded. These steps may be repeated for each test frequency of the test frequency set202. In one embodiment, the forward power and the respective field strengths and/or injection current associated with each of test frequencies may be provided in the calibration set206.

In one embodiment of the radiated immunity test, a broadband antenna may record the field signature simultaneous with the use of the field probe. In another embodiment, the field probe may be removed, the broadband antenna installed, and the signal generator may be cycled through the test frequency set202based on the settings derived while using the field probe (e.g., the forward power levels and associated settings), and the field signature is recorded for each respective test frequency of the test frequency set202. In one embodiment, the field signatures may be included in the calibration set. The field signatures may be referenced to verify certain aspects of the system operation at a later time, as discussed in more detail below.

In the illustrated embodiment, method200includes assessing test frequency subsets210, as depicted at block212. In one embodiment, assessing test frequency subsets includes reviewing the test frequency set to determine if one or more of the test frequencies within the set can be generated simultaneously. In other words, can two or more of the test frequencies be generated at the same time instead of being generated separately, one by one. Each of the test frequency subsets210may include one or several of the test frequencies of the test frequency set202. In one embodiment, assessing the test frequency subsets may include considerations of one or more conditions to determine whether or not two or more carrier frequencies of the test frequency set should be included in the same subset.

In one embodiment, the signal generator must be capable of generating all of the test frequencies in the test frequency subset simultaneously. Thus, in an embodiment of the signal generator that includes a signal generator (e.g., a vector signal generator) and/or upconverter (e.g., frequency synthesizer) they must be able to generate all carriers of the test frequency subset210simultaneously. For example, for a given test frequency subset, the components of the signal generator must be capable of handing the bandwidth associated with the test frequency subset. For example, in an embodiment that includes radiated immunity testing, the bandwidth of the frequency synthesizer, the amplifier (e.g., a broadband amplifier), and the transducer (e.g., a broadband antenna) must be equal to or greater than the difference in frequency between the lowest and highest frequency test signals in the test frequency subset. Further, each of the components (e.g., the frequency synthesizer) must be capable of accurately representing the test frequencies of the test frequency subset simultaneously, with and without modulation. Similar consideration may exists for conducting immunity testing. For example the clamp may be capable of transmitting the associated injection current.

In one embodiment, the amplifier must be capable of supplying the total power required to simultaneously drive all of the test frequencies in the test frequency subset to provide sufficient field strength (e.g., the required field strength of a test standard). In one embodiment, the total power required to simultaneously drive all of the test frequencies in the test frequency subset may be less than total power available from the amplifier. For example, the total power required to simultaneously drive all of the test frequencies in the test frequency subset may be about 80% or less of the power output of the amplifier. Such a precaution may help to ensure that the amplifier is not in compression. Similar power limitations may be provided for some or all of the other components of the signal generator. For example, antennas, conductors, couplers, switches, and the like may be rated above the total power that is expected to pass through them to simultaneously drive all of the test frequencies in the test frequency subset.

In one embodiment, each test frequency subset may include test frequencies that should not interfere with any of the other frequencies when they are generated simultaneously. In one embodiment, no two frequencies may have a substantially similar wavelength. For example, in one embodiment, each of the quarter wavelengths of each of the test frequencies should have a difference of about 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15% or more. In other words, the quarter wavelengths of each of the test frequencies should not be within about 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15% or more, respectively, of the quarter wavelengths any of the other test frequencies in the test frequency subset. In one such embodiment, the wavelength of a test frequency may be defined as:

wavelength=cf(1)
wherein c is the speed of light (e.g., about 3×108m/s) and f is the frequency of the test frequency, and the quarter wavelength is defined as:

quarter_wavelength=wavelength4(2)
Accordingly, the quarter wavelength of a 100 MHz test frequency is about 0.75 m and the quarter wavelength of a 112 MHz wavelength is about 0.67 m. In one embodiment, a comparison of the quarter wavelengths for these two frequencies indicates a difference of 0.08 m that is about 11.9% of 0.67 m and 10.6% of 0.75 m. Because these frequencies have a difference that is greater than 10% of their frequencies, they may be tested simultaneously. In other words, they may both be included in the same test frequency subset.

In one embodiment, each test frequency subset may include test frequencies that do not include significant intermodulation products. In one embodiment, the sum of the intermodulation products must be smaller than the amplitude of the test frequencies of the test frequency subset. If the intermodulation products are significant at a frequency, they may reach a level in which they create an additional test tone at that frequency. For example, they may add to one another, producing an additional carrier frequency during testing. In one embodiment, the forward power of the intermodulation products associated with the test frequency set should be about given number of decibels (e.g., 6 dBm) less in amplitude than the test frequencies to ensure that they do not significantly contribute to the disturbance field. Moreover, a test frequency should not be included in a test frequency subset if it has the same frequency as an intermodulation product of one or more of other test frequencies of the test frequency set. In one exemplary embodiment in which a test frequency of 110 MHz and 112 MHz are in the test frequency set202, and are being considered for inclusion in a test frequency subset, it is noted that intermodulation products may occur at 108 MHz and 114 MHz. Accordingly, if 110 MHz and 112 MHz test frequencies are included in the test frequency subset, test frequencies of 108 MHz and 114 MHz should not be included in the test frequency subset. Further, the significance of the modulation products that may occur at 108 MHz and 114 MHz, must be considered in view of other modulation products that may be the result of other test frequencies included in the test frequency subset. For example, if the test frequencies of 110 MHz, 112 MHz, 116 MHz and 118 MHz, are being considered for inclusion in a test frequency subset, it is noted that modulation products from the test frequencies 110 MHz and 112 MHz may occur at 108 MHz and 114 MHz, and additional modulation products from the test frequencies 116 MHz and 118 MHz may occur at 114 MHz and 120 MHz. Accordingly, the modulation products at 114 MHz should be summed and assessed to determine whether or not the resulting modulation product is significant with respect to the actual test frequencies. For example, if the modulation product is below about 6 dB less than the test frequencies, then the test frequencies in the subset may be satisfactory, however, if the modulation product is higher than about 6 dB less than the test frequencies, then the test frequencies in the subset may be unsatisfactory, and a one or more of the test frequencies may be removed from the test frequency subset. Such an approach may be repeated, e.g., adding, removing, and substituting test frequencies of the test frequency set to the test frequency subset, until the test frequency subsets do not have significant intermodulation products.

In accordance with the above described embodiments, assessing the test frequency subsets210may include, for each of the frequency subsets, assessing whether or not the system is physically capable of generating the given test frequencies simultaneously, assessing whether or not each of the test frequencies in the subsets has a wavelength that is sufficiently different from the wavelengths of each of the other test frequencies to prevent/minimize interference between each of the test frequencies when they are generated simultaneously, and assessing each of the test frequency subset to ensure that significant intermodulation products are not present when the test frequencies are generated simultaneously. Accordingly, each of the test frequency subsets210of the test frequency set202may include a subset of test frequencies that are capable of being provided by the system, that minimize interference and do not include significant intermodulation products when all of test frequencies of the test frequency subset are generated simultaneously.

In one embodiment, the test frequency subsets may include two or more subsets that include test frequencies of the test frequency set. For example, in one embodiment, the test frequency subsets210may include two or more test frequency subsets that include all of the test frequencies of the test frequency set. For example, in an embodiment of immunity testing that includes a sweep from 80 MHz to 1 GHz having two-hundred fifty-five test frequencies, as described above, each of the two-hundred fifty-five test frequencies are included in one of the test frequency subsets. In one embodiment, each of the test frequencies are included in only one of the test frequency subsets.

In one embodiment, method200also includes assessing a subset calibration set214based on calibration of subset field, as depicted at block216. In one embodiment, calibrating a subset field includes calibrating and verifying that a generated field/injection current is sufficient when all of the frequencies in a test frequency subset are generated simultaneously. In one embodiment, calibrating the subset field includes operating the signal generator to generate fields/injection current with the test frequencies of the test frequency subset simultaneously and in accordance with the forward power levels recorded in calibration set206at step208. In one embodiment, while generating the fields/injection current with the test frequencies of the test frequency subset simultaneously, the drive level of the signal generator (e.g., of the frequency synthesizer) is adjusted such that each generated test frequency has the substantially the same forward power levels associated with it in the calibration set206. For example, in one embodiment, the signal generator is adjusted such that a forward power for the test frequencies of the test frequency subset being generated simultaneously, matches the forward power when measured with individual generation of test frequencies at block208. Adjustment of the signal generator should be provided such that it does not overdrive the amplifier. For example, as described above, the total power required to simultaneously drive all of the test frequencies in the test frequency subset may be about 80% or less of the power output of the amplifier. Such a precaution may help to ensure that the amplifier is not in compression.

In one embodiment, a forward power for each generated frequency of the test frequency subset is verified, e.g., checked against the forward power measured for that given test frequency at block208. In one embodiment, the forward power may be measured at an input of the transducer of the signal generator. For example, the forward power may be measured at the probe between the output of the amplifier and the input to the transducer (e.g., antenna) of the signal generator. In one embodiment, the same device used to measure forward power of individually generated frequencies, e.g., at calibration at block208, should be used when measuring forward power during multi-field generation, e.g., at block216. In one embodiment including radiated immunity testing, the receiver may include a field probe and/or the broadband antenna positioned in a similar manner as it was during calibration of the field at block208. In an embodiment that includes conducted immunity testing, the receiver may include a similar device, e.g., the same current probe, used in a similar manner as it was during calibration of the field at block208.

In one embodiment, calibrating the subset field (block216) may include verifying that the settings of the signal generator (e.g., drive levels/forward power levels) derived during generation of the test frequency subsets simultaneously, the amplifier meets linearity standards. In one embodiment linearity of the amplifier can be verified by reducing the drive levels of the generator (e.g., reduced by 5.1 dB) to reduce the forward power of all of the generated test frequencies by a given amount while measuring the forward power to verify that the forward power was reduced by a similar amount (e.g., reduced by 5.1 dB to 3.1 dB). In one embodiment, the drive level may be measured prior to the generated signal reaching the amplifier, e.g., at the probe between an output of the signal generator and an input of the amplifier.

In one embodiment, calibrating the subset field includes adjusting the forward power level to a test level. For example, during calibration, standards may require that forward power levels be set to provide a field strength that is 1.8 times the target field strength required during actual testing. Accordingly, in one embodiment, a reduced forward power level is calculated that will provide the target field strength. During testing, the reduced forward power levels and drive levels associated with the target field strength, as opposed to the previously measured forward power levels, may be used.

In one embodiment, the resulting settings, e.g., drive levels, and associated forward power measurements and target field strength may be recorded in the subset calibration set214, may be used for reference at a later time as discussed in more detail below.

Although the above embodiments are described with respect to a signal generator including a single signal generator/source, embodiments may include one or more signal generators using of multiple signal generators/source. In such an embodiment, the above described techniques would be performed in a similar manner, except for calibration adjustments may be performed on the multiple signal generators/sources.

In one embodiment, method200includes performing an immunity test, as depicted at block218. In one embodiment, performing the immunity test includes subjecting the DUT to each of the test frequencies of the test frequency set. In one embodiment, the DUT is subjected to a plurality of the test frequencies simultaneously. In one embodiment, the generator is operated to generate test frequency sets in sequence. For example, in one embodiment, the signal generator is operated to subject the DUT to all of the test frequencies of one of the test frequency subsets simultaneously, followed by subjecting the DUT to all of test frequencies of another of the test frequency subsets simultaneously, and so on until the DUT has been subjected to all of the test frequency subsets210, and has thus been subjected to all of the test frequencies of the test frequency set. In one embodiment, the signal generator is operated based on the subset calibration set214. For example, the drive levels of the signal generator may be set based on the reduced forward power levels, as described above with respect to calibrating the subset field at block216. In one embodiment, modulation (e.g., amplitude modulation) may be applied to the signals provided at the reduced forward power levels.

During testing operation of the DUT may be monitored to assess and determine whether or not any test frequencies of the test frequency set are affecting operation. In one embodiment, the signal generator is operated to subject the DUT to a test frequency subset. If the DUT continues to operate, the signal generator is operated subject the DUT to the next test frequency subset and so on until an error is detected or the DUT has been properly subjected to all of the test frequency subsets and/or test frequencies of the test frequency set. If an error is detected while subjecting the DUT to a test frequency subset, it may be indicative of an error due to one of the test frequencies within the test frequency subset. In one embodiment, the signal generator is operated to subject the DUT to each of the test frequencies in the DUT individually, one at a time. Such a procedure may enable a determination of which test frequency or test frequencies may generate errors for the DUT, or may expose that the errors are caused by a combination of the test frequencies being generated simultaneously; indicating that the DUT is not susceptible to errors when individually subjected to the test frequencies of the test frequency subset.

In one embodiment, if an error is detected while subjecting the DUT to a test frequency subset, the signal generator is operated to subject the DUT to a subset of test frequencies of the test frequency subset. In other words, the DUT is subjected to one or more subsets of the test frequency subset. Such a procedure may help to reduce the testing time associated with subjecting the DUT to each of the test frequencies in the test frequency subset individually, one at a time. For example, the initial test frequency subset that generated the error may be split into two or more subsets. In other embodiments, one or more of the two or more subsets may be further divided into subsets and so on. Such an embodiment may further reduce testing time. In one embodiment, each of the additional subsets may be calibrated with a procedure similar to that described above, such as those described with respect to blocks204-218.

In one embodiment, method200may be performed in series or may be performed at separate times. For example, the initial steps (e.g., blocks204-214) may be performed to setup a chamber for testing, and the test itself (e.g., blocks218and220) may be performed during each test. In one such embodiment, the initial steps for setting up the chamber may be performed when the test setup is initially built, something in the test setup changes that may affect testing operation, during routine maintenance, and/or a calibration of the system is required. Accordingly, multiple test procedures may be performed between initial setup (e.g., calibrations).

Embodiments of the present invention may be involved with performing test and/or measurement functions; controlling and/or modeling instrumentation or industrial automation hardware; modeling and simulation functions, e.g., modeling or simulating a device or product being developed or tested, etc. Exemplary test applications include electromagnetic compatibility (EMC) immunity testing. However, it is noted that embodiments of the present invention can be used for a plethora of applications and is not limited to the above applications. In other words, applications discussed in the present description are exemplary only, and embodiments of the present invention may be used in any of various types of systems. Thus, embodiments of the system and method of the present invention is operable to be used in any of various types of applications, including generation of various signal types and frequencies. Moreover, application may include including the control and testing of various types of devices such as multimedia devices, video devices, audio devices, telephony devices, etc.

Although the embodiments above have been described in considerable detail, numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to embrace all such variations and modifications. Furthermore, note that the word “may” is used throughout this application in a permissive sense (i.e., having the potential to, being able to), not a mandatory sense (i.e., must). The term “include”, and derivations thereof, mean “including, but not limited to”. As used in this specification, the singular forms “a”, “an” and “the” include plural referents unless the content clearly indicates otherwise. Thus, for example, reference to “a transducer” includes a combination of two or more transducers. The term “coupled” means “directly or indirectly connected”.