METHOD AND APPARATUS FOR ESTIMATING ELECTROMAGNETIC ENVIRONMENTAL EFFECTS IN RF-DEPENDENT SYSTEMS.

Abstract

The described systems and related test methods provide a significant improvement in test accuracy, as well as a reduction in test time for system-level electromagnetic environmental effects (E3) testing. The systems may include a real-time spectrum analyzer, a network analyzer, and a switching / filtering / coupling network, controlled by an information processing device such as a general-purpose computer. These systems can scan all frequencies at each receiver.

Description

METHOD AND APPARATUS FOR ESTIMATING ELECTROMAGNETIC ENVIRONMENTAL EFFECTS IN RF-DEPENDENT SYSTEMS TECHNICAL FIELD The embodiments described herein generally relate to systems and methods for estimating the impact of electromagnetic environmental effects (E3) on radio frequency (RF) dependent systems and subsystems, and specifically to electromagnetic compatibility (EMC) and electromagnetic interference (EMI) at the platform level. DESCRIPTION OF RELATED TECHNIQUE The affected RF platform / component RF source test is one of several tests used to provide certification data to demonstrate to an authorizing agency that the EMC platform meets the authorizing agency's requirements. This test is sometimes referred to as the source / victim test because the victim component has an unintended and undesirable response to RF signals transmitted by the source. These tests provide a structured approach to demonstrating EMC, and if EMI is discovered, the interference can be resolved prior to operational use. For complex platforms such as aircraft, these tests can be lengthy and expensive. These tests include ground operation of every electrical and electronic system while monitoring every electrical and electronic system where EMI could adversely affect the safety of the platform or impair the platform's ability to perform its mission.The source equipment operates in modes considered to be more susceptible to RF emissions and electromagnetic transients. RF-dependent systems are monitored while operating in modes considered more susceptible to RF emissions and electromagnetic transients. An instrumented ground radio test is a subset of the source / victim component test. This test consists of connecting a spectrum analyzer to the radio antenna port and sweeping the operating frequency of a radio receiver under test, or victim, for the operation of the source and ambient systems. All onboard systems are energized, but Aeze / n / eznz / q / YiAi do not transmit. Conventionally, this test is performed in a quiet RF environment (e.g., an anechoic chamber). However, these tests take days to set up and can take weeks to take measurements if used to identify receiver performance under comfortable operating conditions. In certain aspects, the present disclosure addresses the need to estimate the impact of E3 on RF-dependent systems and subsystems more efficiently than in the prior art. The present disclosure provides systems and related test methods that provide significant improvement in test accuracy as well as a reduction in test time for system-level testing of electromagnetic environmental effects (E3). Generally, systems according to the present disclosure may include a real-time spectrum analyzer, a network analyzer, and a switching / filtering / coupling network, controlled by an information processing device, such as a general-purpose computer. Systems according to the present disclosure can scan all frequencies at each receiver. For example, in less than six seconds, a system according to the present disclosure can scan from 2 MHz to 26 GHz. In further aspects, the present disclosure provides a method for performing testing of RF receivers affected by an RF source on a platform having a plurality of RF-dependent devices.The method may include: connecting an array of the plurality of RF-dependent devices to an RF signal communication network; connecting a plurality of acquisition antennas to the RF signal communication network; connecting a real-time spectrum analyzer to the RF signal communication network; continuously monitoring an ambient electromagnetic state on the platform using the real-time spectrum analyzer and the plurality of acquisition antennas; operating an RF source to transmit an RF signal, wherein the RF source is one of the RF-dependent devices in the array; estimating an operating parameter of each RF-dependent device in the array using the real-time spectrum analyzer; identifying a signal of interest using the estimated operating parameter and the ambient electromagnetic state; and identifying an affected RF-dependent device using the signal of interest. neze / n / eznz / q / YiAi In still further aspects, the present disclosure provides an apparatus for estimating electromagnetic effects (E3) on a platform having a plurality of RF-dependent devices. The apparatus may include an RF signal communication network having a plurality of signal carriers, each signal carrier configured to couple to an associated RF-dependent device in the plurality of RF-dependent devices, thereby enabling RF switching and / or filtering for selective signal communication with each associated RF-dependent device; a spectrum analyzer in signal communication with the RF signal communication network and configured to take near-instantaneous measurements of induced RF broadband on the signal carriers coupled to the RF-dependent devices;at least one acquisition antenna in signal communication with the RF signal communication network, the at least one acquisition antenna being configured to collect E3 environmental information in at least one frequency range; and an information processor in signal communication with the RF signal communication network, the information processor being configured to generate E3 characterization data using the at least one acquisition antenna and information generated by the real-time spectrum analyzer. In still further aspects, the present disclosure provides an apparatus for estimating electromagnetic effects (E3) on a platform having a plurality of RF-gated devices. The apparatus may include: an RF signal communication network having a plurality of signal carriers, each signal carrier configured to couple to an antenna of each of the plurality of RF-gated devices, the RF filter thereby enabling selective signal communication with each antenna; a real-time spectrum analyzer, in signal communication with the RF signal communication network and configured to take near-instantaneous measurements of induced RF broadband on the signal carriers coupled to the RF-gated devices;a network analyzer in signal communication with the RF signal communication network and configured to measure an operating parameter associated with each of the plurality of RF devices; and an RF amplifier and one or more antennas, the RF amplifier and at least one acquisition antenna cooperating to collect environmental E3 information in at least one frequency range; and an information processor in signal communication with the RF signal communication network, being; Aeze / n / eznz / q / YiAi configured the information processor to generate E3 characterization data using the RF signal acquisition unit, information generated by the real-time spectrum analyzer, and information generated by the network analyzer. In further aspects, the present disclosure provides a method for performing testing of RF receivers affected by an RF source on a platform having a plurality of RF dependent devices. The method may include the steps of: connecting an array of the plurality of RF dependent devices to an RF signal communication network; estimating an environmental E3 using at least one acquisition antenna and a real-time spectrum analyzer; estimating an operating parameter associated with each RF dependent device of the array using a network analyzer in signal communication with the RF signal communication network; and selectively switching between each antenna of each RF dependent device in the array using the RF signal communication network, wherein the environmental E3 and each operating parameter are estimated over a predetermined frequency range and a selected bandwidth. It should be understood that the examples of certain features of the disclosure have been summarized fairly broadly to facilitate a better understanding of the detailed description that follows and to allow appreciation of the contributions to the art. Of course, there are additional features of the disclosure that will be described below and, in some cases, will form the subject of the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS For a detailed understanding of the present disclosure, reference should be made to the following detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, in which like elements have like numerals and in which: Figure 1 schematically illustrates a platform having one or more RF sources and one or more RF dependent devices; Figure 2 schematically illustrates an embodiment of an electromagnetic environmental effects (E3) test system according to an embodiment of the present disclosure; Aeze / n / eznz / q / YiAi Figure 3 is a flowchart illustrating one embodiment of a method for performing calibration on a platform having one or more RF sources and one or more RF dependent devices according to one embodiment of the present disclosure; Figure 4 schematically illustrates an embodiment of an E3 test system according to an embodiment of the present disclosure for evaluating RF shielding effectiveness; Figure 5 is a flow diagram illustrating one embodiment of a method for testing shielding effectiveness using the system of Figure 4; Figure 6 schematically illustrates an embodiment of an E3 test system according to an embodiment of the present disclosure for evaluating a noise floor for a platform; and Figure 7 shows a flowchart illustrating one embodiment of a method for identifying a change in RF procedure using the system of Figure 6. DETAILED DESCRIPTION Referring to Figure 1, a platform 10 is shown schematically on which a plurality of RF dependent devices 12 are placed. During testing, each of these RF dependent devices 12 may function as an RF source transmitting an RF signal that causes interference and also as an affected (or victim) RF device that is affected by the interference. That is, at different times, a particular RF dependent device may act as an RF source and then as an affected device or vice versa. For convenience, Figure 1 shows some RF dependent devices 12 acting as radio frequency (RF) sources 13 and some RF dependent devices 14 that are affected RF devices. The platform 10 may be mobile; for example, aircraft, spacecraft, land vehicles, or watercraft.RF sources 12 are generally any device capable of emitting RF signals, and RF-dependent devices 12 are devices whose operation may be affected by such emitted RF signals. In some applications, the RF-dependent devices 12 may each have antennas 16 or other similar RF signal receiving components. In addition, RF shielding 18 may be used to enclose portions of RF-dependent devices 12. As described in more detail below, an electromagnetic environmental effects (E3) test system 100 according to the present teachings may be used to estimate E3 effects on the RF-dependent devices 12 and as well as perform system diagnostics and characterization. Testing may be performed on an array of RF-dependent devices 12 on the pad 10.The set may consist of all 12 RF dependent devices or fewer than all 12 RF dependent devices on platform 10. Referring to Figure 2, a non-limiting embodiment of the E3 test system 100 according to the present disclosure is schematically illustrated. The test system 100 may include a spectrum analyzer 102, a network analyzer 104, an RF amplifier 106; one or more antennas 108a, b, c, an RF signal communication network 110, and a general purpose information processor 112. The RF signal communication network 110 may be a modular signal communication network configured to enable selective signal communication with couplers 116a, b, n of the antennas 16 (FIG. 1) of the RF dependent devices 12 (FIG. 1). The RF signal communication network 110 may be in selective signal communication with all or fewer than all of the RF dependent devices 12 on the platform 10. In embodiments, the RF signal communication network 110 may include a digital attenuator 120 in signal communication with the couplers 116a, b, n via associated signal carriers 122a, b, n. It should be understood that while three couplers 116a, b, n and associated signal carriers 122a, b, n are shown, other embodiments may include fewer than or more than three couplers 116a, b, n and associated signal carriers 122a, b, n. In some embodiments, the RF signal communication network 100 may be a switching network. These embodiments may be suitable when extremely low insertion loss is required, signal tolerances are very tight, and the spectrum analyzer is capable of measuring large signals in the vicinity of the measurement of interest without generating spurious emissions. In some embodiments, the RF signal communication network 100 may be a filtering network. These embodiments may be suitable when measurements can be relaxed without problems of slightly increased insertion loss and if the spectrum analyzer generates spurious emissions when measuring signals of interest in the vicinity of adjacent large signals. Aeze / n / eznz / q / YiAi In some embodiments, the RF signal communication network 100 may be a switching network and a filtering network. The spectrum analyzer 102 may be a real-time spectrum analyzer. In embodiments, the spectrum analyzer 102 may be in signal communication with the RF signal communication network 110 and configured to take near-instantaneous (20-50 ms) measurements of broadband (160 MHz) induced RF on the signal carriers 122a, b, n coupled to the RF dependent devices 12 (FIG. 1). The network analyzer 104 may be a network analyzer. In embodiments, the network analyzer 104 may be in signal communication with the RF filter switching network 110 and configured to measure installed VSWR, amplitude, and phase associated with the RF parameters of the RF dependent devices 12. The RF amplifier 106 and antennas 108a-c may be configured to estimate ambient EEE. In a non-limiting arrangement, the antennas 108a-c may include a rod antenna configured to collect ambient EEE in the range of 2 MHz to 50 MHz, a log-periodic antenna configured to collect ambient EEE in the range of 50 MHz to 500 MHz, and a waveguide horn antenna configured to collect ambient EEE in the range of 500 MHz to 26 GHz. The information processor 112 may include microprocessors, memory, algorithms, and input devices suitable for controlling one or more components of the E3 test system 100, for example, the RF filter switching network 110. The information processor 114 may be programmed with algorithms suitable for processing and storing information collected by the network analyzer 104 and / or the spectrum analyzer 102. Referring to Figure 3, a non-limiting method 130 is shown for using the test system of Figure 2 to estimate one or more operating characteristics of the platform 10 of Figure 1. Referring to Figures 1 and 2, at step 132, an antenna, such as an antenna 108a, is positioned at a selected location on the platform 10 (Figure 1). At step 134, the spectrum analyzer 102 is operated to collect environmental EEE data for the RF dependent devices 12 (Figure 1). Steps 132 and 134 may be repeated by repositioning the antenna at different locations on the platform 10 (Figure 1). Steps 132 and 134 may also be repeated using different antennas, e.g., antennas 108b and c. At step 136, a data set is compiled using the measurements from the spectrum analyzer 102. Such a data set may be useful when performing one or more tasks on the platform 10 (Figure 1) such as maintenance, which may unintentionally alter the operating characteristics of the platform 10 (Figure 1). For example, in step 138, maintenance or repair may be performed on one or more subsystems of the platform 10 (Figure 1). After completing step 138, the test system 100 may be used again to estimate one or more operating characteristics of the platform 10 of Figure 1. The positioning and EEE data collection of steps 140 and 142 are generally the same as steps 132 and 134 respectively. After repeating steps 140 and 142 at all selected locations and for all antenna configurations, a post-task data set is compiled using measurements from the spectrum analyzer 102.At step 146 the data sets compiled in steps 136 and 144 are compared and the platform 10 system and subsystems (Figure 1) are tuned, adjusted or reconfigured as needed. Referring to Figure 4, a non-limiting embodiment of an E3 test system 200 according to the present disclosure for evaluating the effectiveness of shielding used to enclose a component onboard the platform is schematically illustrated. The test system 200 may include a spectrum analyzer 102, a network analyzer 104, an RF amplifier 106; one or more environmental antennas 108a, b, c, an RF filter switching network 110, and a general purpose information processor 114. These devices are described above. The test system 200 of Figure 4 also includes one or more radiating modules 116a, b, c configured to emit electromagnetic signals and one or more receiving antennas 117a, b, c that receive the emitted electromagnetic signals. The radiating modules and receiving antennas are paired; for example, 116a and 117a, 116b and 117b, and 116c and 117c.The transmitted and received signals within the pairs may be used to estimate the effectiveness of the EEE shielding. Each radiating module 116 may include a radiating element 118 and a dummy load 120. Referring to Figure 5, a flowchart is shown illustrating a shielding effectiveness test method 201 that utilizes the test system 200 of Figure 4 to evaluate the effectiveness of shielding used to enclose a component of interest. At step 202, a calibration test may be performed as described in connection with Figure 3. A reference EEE is then determined. At step 204, an antenna is positioned near the shielding to be evaluated. At step 206, the spectrum analyzer 102 collects data representative of the ambient EEE using antennas 108a, b, c. Steps 204 and 206 are repeated until ambient EEE data has been collected for all desired frequency ranges. At step 208, this ambient EEE data may be compiled as a reference data set. It should be noted that step 208 can be performed at the same time as steps 204 and 206. At step 210, the radiating module 116a may be placed within a shield structure to be tested, and a receiving antenna 117a is placed outside the same shield structure. For this step, the shield panel is removed. Additional pairs of radiating modules 116b, c and receiving antennas 117b, c are similarly positioned within other shield structures. At step 212, with the shield panels removed, the test system 100 is powered up and scanning is performed over one or more frequency ranges; for example, 2 MHz to 50 MHz, 50 MHz to 500 MHz, and 500 MHz to 26 GHz. The network analyzer 104 measures and records the response of the antennas 117a, b, c. At step 214, shielding panels are installed at all locations to evaluate shielding efficiency. At step 216, with the shielding panels present, the test system 100 is energized and sweeping is performed over one or more frequency ranges; for example, 2 MHz to 50 MHz, 50 MHz to 500 MHz, and 500 MHz to 26 GHz. The network analyzer 104 measures and records the response of the antennas 108a, b, c to characterize the electromagnetic signals emitted by the radiating element 118 that have passed through the shielding. At step 218, the shielding effectiveness is estimated by comparing the data from step 212 with the data from step 216. Generally, the difference between the EEE measurements taken before and after the shield is placed represents the shielding effectiveness. In the described method, each shielding location to be tested has a radiating module and a receiving antenna, for example, a radiating module 116a and a receiving antenna 117a. In some variations, a radiating module and a receiving antenna can be moved from one test location to another. It should also be noted that tests can be performed with the shielding first in place and then removed. neze / n / eznz / q / YiAi Referring to Figure 6, a non-limiting embodiment of the E3 test system 100 according to the present disclosure for estimating a platform noise floor is schematically illustrated. The test system 100 may include a spectrum analyzer 102, one or more antennas 108a, b, c, an RF signal communication network 110, and a general purpose information processor 112. These devices have been described above. Referring to Figure 7, a flowchart is shown illustrating an RF noise floor estimation method 300 that utilizes the test system 100 of Figure 6 to estimate an RF noise floor for a platform of interest. At step 302, a calibration test may be performed as described in connection with Figure 3. A reference EEE is then determined. At step 304, an antenna configured for a specific frequency range is placed on the platform. At step 306, the ambient EEE is estimated using the spectrum analyzer 102. Steps 304 and 305 may be repeated using differently configured antennas. At step 306, while the spectrum analyzer 102 continues recording, a discrete component of the platform is energized to a desired operating state. At step 308, this ambient EEE data may be compiled as a reference data set.It should be noted that step 308 can be performed at the same time as steps 304 and 306. At step 310, a discrete component on board the platform is powered to a desired operating state while the spectrum analyzer collects EEE data until a steady-state EEE can be established at step 312. Additional discrete components of the platform 10 may be powered on sequentially. The spectrum analyzer 102 continuously collects EEE data as each of the discrete components is brought to a powered operating state. At step 314, discrete components may be tested for EEE interference. An operating frequency range may be monitored for each discrete component. Parameters such as fundamental frequencies, harmonics, and spurious emissions may be recorded / monitored and analyzed to identify sources of EMI. For example, the system may be tuned to an emission found within a component's frequency range to determine an interference level. In a non-limiting embodiment, step 314 may be a source / affected device (or source / victim) test that includes the steps of connecting an array of the plurality of RF dependent devices to a signal communication network; connecting a plurality of acquisition antennas to the signal communication network; connecting a real-time spectrum analyzer to the signal communication network; continuously monitoring an ambient electromagnetic state on the platform using the real-time spectrum analyzer and the plurality of acquisition antennas; operating an RF source to transmit an RF signal, wherein the RF source is one of the RF dependent devices in the array; estimating an operating parameter of each RF dependent device in the array using the real-time spectrum analyzer; identifying a signal of interest using the estimated operating parameter and the ambient electromagnetic state;and identify an affected RF-dependent device using the signal of interest.; While the foregoing is directed to embodiments of the present disclosure, additional embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

1. A method for performing testing of RF receivers affected by a radio frequency (RF) source on a platform having a plurality of RF dependent devices, the method comprising: - connecting an array of the plurality of RF dependent devices to an RF signal communication network; - connecting a plurality of acquisition antennas to the RF signal communication network; - connecting a real-time spectrum analyzer to the RF signal communication network; - continuously monitoring an ambient electromagnetic state on the platform using the real-time spectrum analyzer and the plurality of acquisition antennas; - operating an RF source to transmit an RF signal, wherein the RF source is one of the RF dependent devices of the array; - estimating an operating parameter of each RF dependent device of the array using the real-time spectrum analyzer;- identify a signal of interest using the estimated operating parameter and the ambient electromagnetic state; and - identify an affected RF-dependent device using the signal of interest.

2. The method of claim 1, wherein the operating parameter is at least one of: a fundamental frequency, a harmonic, and a spurious emission.

3. The method of claim 1, wherein a plurality of sources are sequentially operated.

4. The method of claim 1, wherein the set includes all RF-dependent devices on the platform.

5. The method of claim 1, wherein the set includes fewer than all RF-dependent devices on the platform.

6. The method of claim 1, further comprising estimating the ambient electromagnetic state of the platform while all RF-dependent devices on the platform are de-energized.

7. The method of claim 5, further comprising sequentially connecting and powering each RF-dependent device in the array while estimating the ambient electromagnetic state of the platform using the real-time spectrum analyzer.

8. The method of claim 1, wherein the RF signal communication network includes at least one of: (i) a switching network, and (ii) a filtering network.

9. An apparatus for estimating electromagnetic effects (E3) on a platform having a plurality of RF dependent devices, the apparatus comprising: - an RF signal communication network having a plurality of signal carriers, each signal carrier configured to be coupled to an associated RF dependent device of the plurality of RF dependent devices, the RF signal communication network enabling signal communication with each associated RF dependent device; - a spectrum analyzer in signal communication with the RF signal communication network and configured to take near-instantaneous measurements of induced RF broadband in the signal carriers coupled to the RF dependent devices;- at least one acquisition antenna in signal communication with the RF signal communication network, the at least one acquisition antenna being configured to collect E3 environmental information in at least one frequency range; and - an information processor in signal communication with the RF signal communication network, the information processor being configured to generate E3 characterization data using the at least one acquisition antenna and information generated by the real-time spectrum analyzer.

10. The apparatus of claim 9, wherein the RF signal communication network includes at least one of: (i) a switching network, and (ii) a filtering network.

11. The apparatus of claim 9, wherein the operating parameter is at least one of: a fundamental frequency, a harmonic, and a spurious emission.

12. The apparatus of claim 9, wherein the information processor is further configured to estimate the ambient electromagnetic state of the platform while all RF-dependent devices on the platform are de-energized.

13. The apparatus of claim 9, wherein the information processor is further configured to estimate the ambient electromagnetic state of the platform using the real-time spectrum analyzer while sequentially connecting and powering each RF-dependent device in the array.

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