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Approved For Release 2000/08/08 : CIA '9800180 CENTER LANE-3 Interim Report July 1984 GEOPHYSICAL EFFECTS STUDY (U) By: HAROLD E. PUTHOFF MARSHA ADAMS SRI INTERNATIONAL TIME RESEARCH INSTITUTE DEPARTMENT OF THE ARMY USAINSCOM FORT GEORGE G. MEADE, MARYLAND 20755 WARNING NOTICE CENTER LANE SPECIAL ACCESS PROGRAM RESTRICT DISSEMINATION TO THOSE WITH VERIFIED ACCESS. CATEGORY 3 333 Ravenswood Avenue Menlo Park, California 94025 U.S.A. (415) 326-6200 Cable: SRI INTL MPK oved For eX1 ease ~ 910 70~0W/t8/08 : CIA-R 8001800160001-6 4REU- NOT RELEASABLE TO CENTER LANE-3 FOREIGN NATIONALS ed For Release 2000/08/08: C8A27#8R001800160001-6 Interim Report Covering the Period 15 November 1983 to 15 July 1984 GEOPHYSICAL EFFECTS STUDY (U) By: HAROLD E. PUTHOFF MARSHA ADAMS SRI INTERNATIONAL TIME RESEARCH INSTITUTE DEPARTMENT OF THE ARMY SRI Project 6600 USAINSCOM ESU 83-147 FORT GEORGE G. MEADE, MARYLAND 20755 WARNING NOTICE CENTER LANE SPECIAL ACCESS PROGRAM RESTRICT DISSEMINATION TO THOSE WITH VERIFIED ACCESS. CATEGORY 3 0 ROBERT S. LEONARD, Director Radio Physics Laboratory DAVID D. ELLIOTT, Vice President Research and Analysis Division ..... Copy No. ..... This document consists of 54 pages. 941/CL-0022 CLASSIFIED BY: CENTER LANE Security Classification Guide Dated 1 March 1983 DECLASSIFY ON: OADR NOT RELEASABLE TO FOREIGN NATIONALS Aft ro -Q0,00 %ol% 16 1 CENTER LANE-3 oved FOOI2 2QQQla8/Or$e4Ir.R ratDO?46 0OtHO160001-6 (415) 326-6200 ? Cable: SRI INTL MPK ? TWX: 910-373-2046 Approved For ReleaI3 Iq, 6-007888001800160001-6 CONTENTS (U) LIST OF ILLUSTRATIONS . . . . . . . . . . . . . . . . . . . . . V LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . V I OBJECTIVE . . . . . . . . . . . . . . . . . . . . . . . . . 1 II INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . 3 III PRESENT STATUS . . . . . . . . . . . . . . . . . . . . . . 5 A. General . . . . . . . . . . . . . . . . . . . . . . . 5 B. Literature Search . . . . . . . . . . . . . . . . . . 7 C. ELF Measurements . . . . . . . . . . . . . . . . . . . 7 1. Introduction . . . . . . . . . . . . . . . . . . 7 2. Los Altos Site . . . . . . . . . . . . . . . . . 8 3. ELF Data Acquisition Systems . . . . . . . . . . 8 a. Basic System Design . . . . . . . . . . . . 8 b. FFT Program . . . . . . . . . . . . . . . . 10 c. System Electronics . . . . . . . . . . . . . 10 d. ELF Electronics/Software Subtasks (Status) . . . . . . . . . . . . . . . . . . 10 e. ELF System Calibration . . . . . . . . . . . 11 D. Satellite Downlink Geophysical Data-Acquisition System . . . . . . . . . . . . . . . . . . . . . . . . 12 E. Geophysical Data/RV Performance Correlation Analysis . . . . . . . . . . . . . . . . . . . . . . . 14 A FAST FOURIER TRANSFORM ROUTINE FOR ELF DATA . . . . . 19 B ULF TREE POTENTIALS AND GEOMAGNETIC PULSATIONS . . . . 31 C FORMAT FOR SATELLITE BROADCAST OF SPACE ENVIRONMENT SERVICES . . . . . . . . . . . . . . 37 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 Approved For Relea1'N(Cp/h$51E6-00788R001800160001-6 Approved For Release 200tM 9 m1 EItt5788ROO1800160001-6 THIS PAGE INTENTIONALLY LEFT BLANK iv Approved For Release 20dUOM-A1 SU [D0788R001800160001-6 Approved For Release J0 96-00788R001800160001-6 UffA0?5fftW ILLUSTRATIONS (U) 1 ELF Data-Acquisition System . . . . . . . . . . . . . . . . . 9 2 Real-Time Geophysical Data Acquisition Via Westar IV Downlink . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 3 Real-Time Geophysical Data-Acquisition System . . . . . . . . 15 4 Geophysical/Performance Data-Analysis System . . . . . . . . . 16 TABLES (U) 1 Geophysical Data Bases . . . . . . . . . . . . . . . . . . . . 6 Approved For ReleaU I Sl F 1096-00788R001800160001-6 Approved For Release 20UW 1A Sfl 788R001800160001-6 THIS PAGE INTENTIONALLY LEFT BLANK vi Approved For Release 20UtCLA E4ED0788R001800160001-6 Approved For Release 200^&ND'G'T?P96-00788 R001800160001-6 CENTER LANE-3/NOFORN I OBJECTIVE (U) (S/CL-3/NF) The objective of this effort is to investigate the possible effects of ambient geophysical/low-frequency electromagnetic factors on remote viewing (RV)* performance as a potential aid to increasing the performance levels of Army INSCOM remote viewers. (U) RV (remote viewing) is the acquisition and description, by mental means, of information blocked from ordinary perception by distance or shielding. Approved For Release Jf1(M '. - _ eRR6-00788R001800160001-6 Approved For Release 20MQ8J9$L Ik-R788R001800160001-6 THIS PAGE INTENTIONALLY LEFT BLANK Approved For Release 20U1CLAS ED0788R001800160001-6 Approved For Release 200QM*fN DP96-00788RO01800160001-6 CENTER LANE-3/NOFORN II INTRODUCTION (U) (S/CL-3/NF) SRI International is tasked to conduct a study for Army INSCOM to investigate a potential correlation between remote viewing (RV) performance and ambient geophysical/extremely-low-frequency electro- magnetic (ELF) activity. The possibility of such correlation is indicated, for example, by studies showing psychophysiological effects 102* and behavioral changes3i4 associated with ELF electro-magnetic fields. The geophysical variables of interest include such factors as ELF intensity/ fluctuations, ionospheric conditions, geomagnetic indices, sunspot number, and solar emissions (e.g., X rays and solar flares). The questions to be answered in this program are ? Do geophysical/performance correlations exist such that measurement of the ambient geophysical variables could be used as an indicator of expected performance? ? If so, can optimum performance windows be identified? (U) The structure of the program that will address the above issues consists of - SRI (Menlo Park, California location) - Time Research Institute (Los Altos, California field station). ? Real-time geophysical data acquisition via NOAA (National Oceanic and Atmospheric Administration) Westar IV satellite downlink. ? Computer correlation studies of RV performance versus variables of interest. (U) References are listed at the end of this report. Approved For Release 2000mmuu - P96-00788 R001800160001-6 CENTER LANE-3/NOFORN Approved For Release 200LMCLAISSTFI D788ROO1800160001-6 THIS PAGE INTENTIONALLY LEFT BLANK 4 Approved For Release 20UMCLA00788R001800160001-6 Approved For Release 2000/08/08 : CIA-RDP96-00788R001800160001-6 UNCLASSIFIED III PRESENT STATUS (U) A. (U) General (U) In order to accomplish the goals set out in Section II, the program has been designed as a joint effort between SRI International and Time Research Institute of Los Altos, California, with SRI as the prime contractor. Time Research Institute is a research organization that specializes in temporal analysis of geophysical variables and their po- tential correlation with phenomena of interest, such as weather patterns, earthquakes, and so forth. (U) With regard to the present effort, Time Research Institute is responsible for establishing the appropriate hardware and software systems for collecting and analyzing data concerning environmental conditions and their correlation with RV performance. The purpose of the correlation study is to determine whether RV performance is enhanced or degraded by measurable changes occurring in the geophysical (including solar- terrestrial) environments. The specific data bases under consideration in this effort are given in Table 1. (U) Should correlations between geophysical variables and RV performance be found, the application potential of the effort is twofold: (1) Time periods in which enhanced RV performance might be expected could be identified, resulting in increased quality and accuracy of information obtained through such channels; similarly, time periods in which degraded RV performance might be expected could be avoided. Thus, optimum performance windows would be identified. (2) An increased understanding of the types of environmental changes that correlate with RV performance could provide clues as to the mechanisms involved in RV functioning. Such knowledge would lead to more focussed research on factors that could enhance RV performance, and would also provide information critical to the development of defensive countermeasures against RV. Approved For Releas ffi // 85 SI mFD6-00788R001800160001-6 Approved For Release 2OQQ/Qg/ Al.?tQj788ROOl8OO1 6OOO1-6 (U) GEOPHYSICAL DATA BASES ? Solar-Terrestrial - Geomagnetic Ground-measured indices Ap, K, etc. Satellite-measured intensities - Solar flux (MHz) 15,400 1,415 8,800 606 4,995 410 2,800 245 2,695 - Sunspot number - Solar flares - Interplanetary magnetic field - Solar wind (Pioneer XII) - Protons - Cosmic ray indices (neutron monitor) ? Ionospheric Measurements - Sudden ionospheric disturbances (SIDS) - Auroral electrojet - Radio propagation quality indices ? ULF/ELF - 30 frequencies (from 1 to 30 Hz) (U) The tasks listed in Section II (literature search, real-time ELF measurements, real-time geophysical data acquisition via satellite downlink, and correlation studies of RV performance versus geophysical variables of interest) have been prioritized with the goal of producing the longest possible ELF data base during the period of this contract. Therefore, while all of the tasks are being pursued in parallel, ELF- related tasks have been the focus of attention to date. Approved For Release 2LpLsmft788ROO1800160001-6 Approved For Release 2000/08/08 : CIA-RDP96-00788R001800160001-6 UNCLASSIFIED B. (U) Literature Search (U) The purpose of the literature search is to acquire and integrate information from recent work done in the field of biological response to ELF and geophysical conditions. Approximately 30 keywords are in use as input to a computerized literature search. Forty manu- scripts have been obtained to date and are in the process of being reviewed, plus additional sources of literature have been identified and will be retrieved as priorities permit. C. (U) ELF Measurements 1. (U) Introduction (U) Although the ELF frequency range (3 to 300 Hz) has been studied in some detail, many unknowns remain. For example, although it is known that ELF frequencies generated by geophysical means (e.g., elec- trical storm activity) tend to distribute themselves globally, little information is available on the variation of the ELF environment from location to location. Therefore, local variations may exist that are caused by both manmade sources, and by the geological structure of the area. In the San Francisco Bay Area, manmade sources that generate ELF on a local scale include motors, telephone lines, power lines, and electrical subways [Bay Area Rapid Transit (BART)], and it needs to be determined whether the emission from such sources constitutes a signif- icant contribution to the omnipresent global ELF field. (U) In order to address the above issue, two ELF monitoring stations are being set up--one at SRI Menlo Park (in the RV Laboratory), the other at the Time Research Institute field station, 17 km distant. It is anticipated that the SRI environment may be a "noisy" one due to the large amount of electronics known to be in the area. Data from the two sites, taking the field site as a reference, are to be compared in order to begin to differentiate the naturally-occurring ELF from the manmade noise occurring at the location where RV is being carried out. Approved For Releasue 1 t8KS: ft. 6-00788RO01800160001-6 Approved For Release 203 :A f.f5788ROO18OO16OOO1-6 v. LO 2. (U) Los Altos Site (U) Since May 1982, Time Research Institute has been operating an ELF monitoring site in Los Altos, collecting data twice daily for the purpose of correlating ELF disturbances with various phenomena of interest. In this period, analysis techniques were developed that are directly applicable to the present task. (U) One of the first tasks was the upgrading of the Los Altos ELF monitoring site to provide coverage during power interrupts. Research was performed to determine the best power-interrupt system, including generators. The selection criteria chosen for the generator sought to optimize power output, cost effectiveness, and reputation for reliability, with the consideration that this system might serve as a model for addi- tional sites in the client community. On this basis, a 3500-W Kubota generator was bought and installed at the site. A PTI',Industries "Data- shield" device was also purchased and installed, for use in conjunction with the generator (which must be started manually). This device powers the required electronics for a period of twenty minutes on its own while awaiting generator startup. Furthermore, an automatic alarm telephone dialing system dials up as many as four individuals should a power failure occur while no one is at the site. The two devices working together have protected the system on numerous occasions from power interruptions-- including an 8-hr outage planned by Pacific Gas and Electric Company. Thus, since installation of the power-interrupt equipment, there has been no loss of data collection/storage. 3. (U) ELF Data Acquisition Systems a. (U) Basic System Design (U) With the requirement that two ELF monitoring sites be implemented for the program--one at SRI and one at Time Research Institute--it was decided that the two systems would be made identical. In this way, differences between the two systems would be minimized, thus reducing the opportunity for artifactual differences between the two sys- tem outputs. Approved For Release 2 c U . N LkS64 ft788ROO1800160001-6 Approved For Release n=?/q$ s~f ffff-00788RO01 800160001-6 14V an N-S (U) Figure 1 is a block diagram of the basic ELF data acquisition system. The ELF signal is collected by an antenna, amplified, and then digitized by an analog-to-digital (A/D) converter so that the signal can be input into an IBM PC Jr. computer for the purpose of analy- sis by a fast-fourier-transform (FFT) program on at least an hourly basis. The recorded data are then transferred by floppy diskette to an IBM XT computer for further handling. ELF INPUT DATA A/D CONVERTER COMPUTER IBM PC JR. HOURLY DATA UNCLASSIFIED MAKES SIGNAL READABLE BY COMPUTER, DETERMINES INTENSITY OF SIGNAL FREQUENCY COMPONENTS ,.FLOPPY DISKETTES TRANSPORTED TO IBM XT COMPUTER (U) As indicated in the above system description, an integral part of the data acquisition system is computerized record keeping, using IBM systems--both the IBM PC Jr. and the IBM XT. The software is written and compiled on the XT, used as a master system, and then run on the PC Jr. (the PC Jr. is not itself large enough to run a compiler, nor are there compilers written for it). Beyond this, however, in spite of the much publicized "compatibility" between the various Approved For Releas N(Gk/IS 611HL-00788 R001800160001-6 Approved For Release 20QQ/ ,L$ : j&I??pV?ttj788R001800160001-6 IBM PC systems, some development time had to be expended to ensure that programs compiled on the XT (that were concerned with communication with external devices) could be run on the PC Jr.--because they handle the addressing of communication ports differently. b. (U) FFT Program (U) A consultant was hired from the Radioscience Labora- tory at Stanford University to critique the ELF system at Time Research Institute as it stood at program start. As part of that critique, he recommended changes in the FFT software to increase its accuracy and running speed. As a result, new FFT software was written in compiled BASIC and then debugged. The program description is given in Appendix A. This task was completed in mid-April. c. (U) System Electronics (U) The prototype system of Figure 1 was assembled and installed for our purposes at the Los Altos site. Early tests indicated that modification of the existing electronics was required because (1) the system was sensitive to ground-loop problems, thus the preamplifier had to be redesigned to include an isolation amplifier, and (2) when the new system was installed in mid-June, it was found that a slowly-varying dc level was superimposed on the incoming ELF signal, resulting in ex- cursions that exceeded the limits of the A/D converter at amplification levels required for good signal analysis. Therefore, new circuitry was designed to eliminate the dc problem. With these changes, the ELF detec- tion system is scheduled for completion of testing, debugging, and calibration at the Los Altos site in August, before its sister system is installed at SRI. d. (U) ELF Electronics/Software Subtasks (Status) (U) The status of the ELF electronics/software subtasks Approved For Release 20I Q ,A6-StH-PbE-D788R001800160001-6 Approved For Release 'J NOtA S IFF1FE D00788R001800160001-6 (U) ? Subject to the requirement that the basic microprocessor units to be used in the program would (1) be able to com- municate with an IBM XT, (2) have at least 64K of memory, (3) possess diskette storage capability, and (4) be cost effective, the IBM PC Jr. was selected from among the various alternatives, and two units were purchased. ? Preamplifiers, low bandpass filters, and amplifiers have been designed, and one complete prototype system has been assembled. Amplifiers and filters have been assembled for the second system to be installed at SRI. ? Design specifications have been completed for the ELF antenna. Assembly of this antenna is pending the results of a calibration task (described in Section III.D.3.e). ? A survey of A/D converters that would be compatible with the other system components was completed, and the selected units were purchased. ? Communication between the IBM PC Jr. and the A/D con- verter has been established, enabling the computer to read the incoming signal. ? Software has been developed and debugged that: (1) reads the communications RS 232 port of the PC Jr. input from the A/D converter, (2) performs FFT analysis of the signal, and then (3) writes half-hourly averages of 19 different frequencies (from 1 to 29 Hz) to a computer diskette. Further software refinements will continue to be made, such as determining daily maximum values for each frequency. This software has been implemented and debugged. The sys- tem is ready to begin data acquisition upon implementation of the dc-level-controlling hardware. Minor enhancements of the software will continue. ? The Los Altos system is now in operation and is being tested. It is anticipated that the SRI system will be implemented in August. e. (U) ELF System Calibration (U) System calibration is proceeding. The Stanford University consultant mentioned earlier is an expert in the areas of ELF and VLF measurement, antenna design, and spectral analysis. His cali- bration program is being carried out at the present Los Altos site using specialized, sophisticated instruments from the Stanford Radioscience Laboratory. Approved For ReleasynQ/O'8108`q W I1 lP6-007888001800160001-6 Approved For Release 20l( /l:AIS-glf 1t15788RO01800160001-6 (U) As part of the calibration process, certain power- line and power-supply "noise" sources were identified that could have produced artifacts in the historical and ongoing data.' Therefore, in- creased electronic-filtering measures are being incorporated into the system, including software changes to recalibrate past data already in (U) Finally, as part of the calibration process, three systems are to be monitored simultaneously: (1) the original unmodified Los Altos system on which the historical ELF data have been acquired; (2) a new system (described in this report) using an ELF wire-coil antenna designed by and on loan from the Radioscience Laboratory at Stanford University; (3) the new system, but with a bioantenna (oak tree) as an antenna, which is a procedure recommended by Stanford (see Nature reprint, Appendix B). The results from the calibration tests will be used to calibrate the historical data base, and to fix the final antenna design. D. (U) Satellite Downlink Geophysical Data-Acquisition System (U) A near real-time satellite downlink system for solar-terrestrial data has recently become available from NOAA (National Oceanic and Atmo- spheric Administration). With this unit, it is possible to provide immediate feedback and/or analysis in conjunction with RV sessions. (Normally, there are long delays in procuring solar-terrestrial data; without the downlink, delays of 10 days to 6 months are standard.) The downlink system provides for accumulation of a detailed data base directly on computer diskettes. (See Appendix C for an item-by-item description.) (U) A satellite controller and a dish antenna for the downlink system were ordered and installed at the Los Altos site early in the project (see Figure 2). At the time of this writing, specifications for data-acquisition software for the IBM PC Jr. have been completed, and first-order software has been written that captures the data to computer diskettes. Because of the large volume of data transmitted each minute, a double-density, double-sided diskette fills in about 21 hours. Disk- Approved For Release 2L1kA11788ROO1800160001-6 Approved For Releas N nin ~/H SIf r -00788 R001800160001-6 CONTROLLER DATA DISKETTE IBM XT COMPUTER .BURROUGHS B6900 COMPUTER FIGURE 2 (U) REAL-TIME GEOPHYSICAL DATA ACQUISITION VIA WESTAR IV DOWNLINK (U) ettes have been changed on an almost daily basis since early April in order to begin to acquire a long-term data base. (U) To increase the amount of data that can be stored on a diskette, it is necessary to separate numerical data of interest. The necessary software is now being written that will be able to identify the various data types as they are transmitted, so that only the data of interest will be transferred to an appropriate data file on the diskette. Statistical analysis can then be done on the data in this form. (U) Other data bases are continuing to be maintained for this project by Time Research Institute. Files of 2800-MHz solar flux, the planetary magnetic activity index (Ap), the Anchorage magnetic index, 13 Approved For ReleasUN &S'6I -00788R001800160001-6 Approved For Release 20U/l,AIS4fVjt16788ROO1800160001-6 (U) and the Stanford mean solar magnetic field are updated on a weekly or monthly basis as the data are available. ELF data from the "old" system are recorded twice daily; ELF data from the "new" system are being recorded at the following intervals: half-hourly averages (48 times a day), and two sets of half-daily averages (twice a day) at 00:00 and 12:00 UT, and at 04:30 and 16:30 UT. Whole-day averages are also being recorded. (U) To summarize the status of the satellite-downlink data- acquisition system: ? The downlink-geophysical system is in place and in operation at the Los Altos site. ? Partial data acquisition from the downlink is in place. ? Software for the final data-acquisition system will be completed and implemented in August. E. (U) Geophysical Data/RV Performance Correlation Analysis (U) Data for RV sessions are to be analyzed for statistical cor- relation with respect to the battery of geophysical data sets listed in Table 1, and those acquired by Time Research Institute via measurement (Figure 3). Recording of RV and geophysical data is now in progress. The overall system for data acquisition and analysis of RV performance/ geophysical data is depicted in Figure 4. When enough data have been collected toward the end of the contract period, analysis will be performed. The tasks described in earlier sections are in preparation for this task, and therefore have received the bulk of the effort. Certain subtasks in the analysis task, which require a longer leadtime, have, however, already been completed in preparation for the analysis. (U) The primary statistical program that will be used to scan the data for possible relationships is called EPOCH ANALYSIS. This program reads two files simultaneously. The first file is an event file, the second a data file. The program first reads an event, then scans the data temporally backward and forward in time around the event. This information is stored, a second event is read, and so forth. When all Approved For Release 20 10&AS{PLE-788ROO1800160001-6 Approved For Releasi jN s SIl E -00788R001800160001-6 DATA DISKETTE DATA DISKETTE DATA DISKETTE FIGURE 3 (U) REAL-TIME GEOPHYSICAL DATA-ACQUISITION SYSTEM (U) the events and surrounding data have been read, a printout is created that lists appropriate cross-correlation statistics between event and data elements. (U) Preliminary scans of data generated during an approximate 100-site series with one remote viewer have been carried out. The session quality was graded on a scale of 0 to 3+, and correlations between solar magnetic field and solar sunspot number were investigated. Some correlation between RV performance and solar sunspot number was found, which, if substantiated by further data, would indicate the possibility that performance might improve immediately after a peak in the sunspot number, and would deteriorate just before the sunspot number peaks in its 27-to-29-day cycle. This result is based on data points that are too small in number to be taken seriously at the point, however, and is mentioned only to give an example of the types of correlations that will be sought out and examined during the course of study. Approved For ReleasUNQ SIIH -00788RO01800160001-6 Approved For Release 2001f4AlS-?ff JtJ5788R001800160001-6 PERFORM- ANCE DATA ELF DATA GEO- PHYSICAL DATA DATA BASE MANAGEMENT SYSTEM EPOCH ANALYSIS GRAPHS/ STATISTICS STATISTICAL ANALYSIS GRAPHS/ STATISTICS (GEOPHYSICAL DATA) BURROUGHS B6900 COMPUTER ANALYSIS REQUIRING LARGE MAINFRAME (e.g., MULTIVARIATE ANALYSIS) AND GRAPHS MANUAL ANALYSIS FIGURE 4 (U) GEOPHYSICAL/PERFORMANCE DATA-ANALYSIS SYSTEM Approved For Release 2 0LA$ DJ788R001800160001-6 Approved For Releas,p~OQQ(Q8/Q8S jJPd6OO788ROOl 800160001-6 IV SUMMARY (U) (U) Approximately 80 percent of the project's data-acquisition tasks have been completed, and all of the equipment and hardware have been purchased and delivered. (U) System calibration should be completed in the near future, and ELF and downlink-data acquisition will have begun in their final formats. (U) At the above point, the focus of effort will turn to analysis of past and present geophysical and ELF data, soon to be followed by the initiation of correlation studies of these data against RV performance. lb IMO Approved For Releascu f fe IE,pVS9Nqffl1!ff&-00788RO01 800160001-6 Approved For Release 20MIN?BL AA-121f fg"788ROO1800160001-6 Approved For Release 20I&AgMfqED0788R001800160001-6 Approved For Release 2000/08/08 CIA-RDP96-00788R001800160001-6 UNCLASSIFIED FAST FOURIER TRANSFORM ROUTINE FOR ELF DATA (U) Approved For Release ~QIp~6~0A:fq.rf-00788R001800160001-6 Approved For Release 2000/08/08 : CIA-RDP96-00788ROO1800160001-6 UNCLASSIFIED THIS PAGE INTENTIONALLY LEFT BLANK 20 Approved For Release 20 QMS&788ROO18OO16OOO1-6 UffeL.&W Approved For Releasgdf j d/q8S?Ir4-ff R96-00788R001800160001-6 PROGRAM DESCRIPTION * :THIS PROGRAM USES THE FAST FOURIER TRANSFORM (FFT) ALGORITHM TO ;CALCULATE THE SPECTRAL MAGNITUDES OF AN ARRAY OF CLOSE-PACKED REAL INPUT ;DATA POINTS. THE PROGRAM IS ORGANIZED AS FOLLOWS: 1. AT THE START, DATA POINTS ARE STORED IN THE REAL ARRAY X(1), WHERE i RUNS FROM Z TO NX-1. NX MUST BE AN INTEGRAL POWER OF 2, OF THE FORM NX - 2^MX (IE, MX - LOG2(NX)). SUCCESSIVE ELEMENTS OF X REPRESENT SUCCESSIVE SAMPLES OF AN INPUT SIGNAL, SAMPLED AT REGULAR INTERVALS OF TIME DT. 2. THE REAL ARRAY X(i) IS TREATED FOR THE FFT AS A COMPLEX ARRAY OF NX/2 PAIRS OF REAL AND IMAGINARY ELEMENTS. THAT IS, THE REAL ELEMENTS OF THE ARRAY ARE THE EVEN-NUMBERED INPUT SAMPLES, AND THE IMAGINARY ELEMENTS OF THE ARRAY ARE THE ODD-NUMBERED INPUT SAMPLES. AFTER THE FFT IS CALCULATED, AN ADDITIONAL STEP IS USED TO EXTRACT THE SPECTRUM OF THE REAL INPUT DATA. TRANSFORMING CLOSE-PACKED DATA IN THIS WAY, EVEN THOUGH IT REQUIRES AN ADDITIONAL STEP FOR THE REAL TRANSFORM EXTRACTION, IS FASTER THAN TRANSFORMING A COMPLEX ARRAY OF NX REAL-IMAGINARY PAIRS (2*NX ELEMENTS), WHERE ALL OF THE INITIAL IMAGINARY VALUES ARE ZERO. 3. THE FFT IS CALCULATED AS FOLLOWS: A. THE INPUT PAIRS IN X ARE REARRANGED IN BIT-REVERSED ORDER. B. THE FFT IS CALCULATED USING DECIMATION IN TIME, WITH ANGLE ARGUMENTS IN EACH SUB-DFT APPEARING IN NATURAL (IE, INCREASING) ORDER. C. AFTER THE LAST PASS THROUGH THE FFT ALGORITHM, THE ARRAY X CONTAINS SPECTRAL VALUES IN NORMAL ORDER, WITH EACH EVEN POINT A REAL VALUE AND EACH SUBSEQUENT ODD POINT THE CORRESPONDING IMAGINARY VALUE. 4. FOLLOWING THE FFT THE REAL TRANSFORM IS EXTRACTED. NOTE THAT IF THE SAMPLING INTERVAL (THE TIME BETWEEN SUCCESSIVE SAMPLES) IS DT, THEN THE TOTAL SIGNAL INTERVAL PROCESSED IS NX*DT (THE FFT ASSUMES THAT THE MISSING RIGHT END POINT IS THE SAME AS THE FIRST POINT). THE FFT GENERATES A SPECTRUM CONTAINING VALUES AT INCREMENTS OF DF IN FREQUENCY, WHERE DF - 1/(NX*DT). IF WE WERE TO TRANSFORM AN ARRAY OF NX COMPLEX DATA POINTS (WHOSE IMAGINARY VALUES WERE ZERO, SINCE WE ARE CONCERNED WITH A REAL SIGNAL) WE WOULD GENERATE NX COMPLEX SPECTRAL POINTS RANGING IN FREQUENCY FROM Z TO (NX-1)*DF Hz. HOWEVER, THE POINTS FROM (NX/2+1)*DF Hz TO (NX-1)*DF Hz ARE MERELY THE COMPLEX CONJUGATES OF THE LOWER POINTS, AND CONTAIN NO ADDITIONAL INFORMATION. THIS IS BECAUSE THE NYQUIST RATE, OR THE HIGHEST UNALIASED FREQUENCY THAT CAN BE SAMPLED, IS 1/2*NX*DF. WHEN WE TRANSFORM NX REAL CLOSE-PACKED POINTS AND THEN EXTRACT THE REAL TRANSFORM, WE GET ONLY THE LOWER NX/2 COMPLEX SPECTRAL VALUES, WHICH ARE ALL THAT ARE NEEDED. lirm Approved For Releas c&".l%F 96-00788 R001800160001-6 Approved For Release 2000(RQ L CIA-EWf bO788ROOl800160001-6 5. NEXT, THE SPECTRUM IS CONVOLVED WITH A SHORT WINDOW FUNCTION. THE REAL AND IMAGINARY (EVEN AND ODD) POINTS ARE CONVOLVED SEPARATELY, SINCE THE WINDOW FUNCTION IS A SEQUENCE OF REAL NUMBERS. WINDOWING IS NECESSARY IF THE SIGNAL FILTERS WE ARE EFFECTIVELY SYNTHESIZING ARE TO HAVE A USEFUL SHAPE. WITHOUT WINDOWING WE WOULD FIND THAT EACH SPECTRAL FILTER WOULD HAVE A NARROW PASSBAND BUT SIGNIFICANT SIDELOBE RESPONSES. THAT IS, THE MAGNITUDE OF A SPECTRAL LINE X(1) WOULD DEPEND NOT ONLY ON SIGNAL COMPONENTS NEAR 1*DF IN FREQUENCY, BUT ALSO SIGNIFICANTLY ON COMPONENTS AT OTHER FREQUENCIES AS WELL. WINDOWING BROADENS THE SHAPE OF THE PASSBAND OF EACH SPECTRAL FILTER BUT ;DECREASES THE SIDELOBE RESPONSES. THE AMOUNT OF BROADENING AND SUPPRESSION OF SIDELOBES DEPENDS ON THE WINDOW ORDER, OR THE LENGTH OF THE WINDOW FUNCTION WHICH IS CONVOLVED WITH THE RAW SPECTRUM. 6. FINALLY, THE MAGNITUDE OF THE SIGNAL AT EACH SPECTRAL FREQUENCY IS CALCULATED AS THE ROOT SUM OF THE SQUARES OF THE REAL AND IMAGINARY SPECTRAL COMPONENTS (IE, THE VECTOR MAGNITUDE OF EACH COMPLEX SPECTRAL POINT) AND SCALED TO MAKE THE PROCESSING GAIN INDEPENDENT OF THE SIZE OF THE BLOCK LENGTH NIX. WE COULD ALSO CALCULATE THE PHASE OF THE SPECTRAL POINTS BUT THIS INFORMATION ISN'T TOO VALUABLE FOR OUR USE. NOTE THAT THE HIGHEST MEANINGFUL SPECTRAL FREQUENCY DEPENDS ON THE ANTI- ALIASING LOW-PASS FILTER THAT IS USED WHEN THE SIGNAL IS SAMPLED. THERE IS NOT MUCH MEANING TO SPECTRAL POINTS ABOVE. THE FILTER CUTOFF FREQUENCY, WHERE SIGNALS ARE ATTENUATED AND!FREQUENCY ALIASING BECOMES A PROBLEM. THUS, IN THIS PROGRAM! WE DO NOT CALCULATE SPECTRAL COMPONENTS ABOVE ABOUT 30 Hz (THE NOMINAL CUTOFF FREQUENCY OF THE LOW-PASS FILTER). ,THIS PROGRAM IS WRITTEN IN BASIC FOR THE IBM PC COMPUTER.' HOWEVER, IT ;IS EASILY ADAPTED TO OTHER MACHINES. FOUR THINGS TO WATCH OUT FOR WHEN ;TRANSFERRING THE PROGRAM TO ANOTHER VERSION OF BASIC ARE:' 1. ALL ARRAYS START WITH INDEX 0. THAT IS, THE ARRAY X(NX) RUNS FROM X(0) TO X(NX-1). ARRAY REFERENCES WILL NEED TO BE CHANGED IF THE PROGRAM IS TO BE USED ON MACHINES WHERE THE!FIRST ELEMENT OF ARRAYS HAS INDEX 1. 2. ALL VARIABLES WHOSE NAMES START WITH THE LETTERS "I" THROUGH "N" ARE IMPLICITLY INTEGERS (DEFINT I-N STATEMENT)!. THESE VARIABLES MAY NEED TO BE RENAMED. IT IS IMPORTANT!THAT LOOP COUNTERS AND ARRAY INDEX VARIABLES BE INTEGERS BECAUSE INTEGER ARITHMETIC (WHERE AVAILABLE) IS FASTER THAN FLOATING-POINT ARITHMETIC. 3. THIS PROGRAM USES THE INTEGER DIVISION OPERATOR "\". THIS MAY BE CHANGED TO "/" IN OTHER VERSIONS OF BASIC. 4. THIS PROGRAM USES LOGICAL OPERATORS ("NOT", "AND", "OR") ON INTEGER VARIABLES (NOT LOGICAL VARIABLES) IN THE BIT-REVERSAL ROUTINE. IF THESE OPERATORS ARE NOT AVAILABLE THE!ALTERNATE VERSION OF STATEMENTS 30ZZ-3190 USING ONLY INTEGER ARITHMETIC MUST BE SUBSTITUTED. Approved For Release 20V)FWLikSfflF f E0O788R001800160001-6 Approved For Release 2000/08/08 : CIA-RDP96-00788R001800160001-6 UNCLASSIFIED wwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwww ;w w CHOICE OF SAMPLING TIME AND BLOCK SIZE ;w w wwwwwwwwwwwwwwwwwwwwww,rwwww*wwwwwwwwwwwwwwwww*wwwwwwwwwwwwwwwwwwwwwwww*w ; ;THE SAMPLING TIME DT AND THE BLOCK SIZE NX TOGETHER DETERMINE THE ;NUMBER OF SPECTRAL POINTS CALCULATED AND THEIR SPACING IN FREQUENCY. ;THE CHOICE OF SAMPLING TIME ALSO AFFECTS THE FREQUENCIES AT WHICH POWER- ;LINE HARMONIC INTERFERENCE THAT IS PASSED BY THE ANTI-ALIASING LOW-PASS ;FILTER WILL APPEAR IN THE SPECTRUM. THE FOLLOWING DISCUSSION ASSUMES ;THAT THE 30 Hz LOW-PASS FILTER WILL BE USED TO ATTENUATE HIGH FREQUENCY ;SIGNAL COMPONENTS BEFORE SAMPLING. ; OF THE INPUT SIGNAL THAT IS SAMPLED CONTAINED ONLY FREQUENCIES BELOW 130 Hz IT WOULD BE SUFFICIENT TO SAMPLE AT THE NYQUIST RATE OF 60 SAMPLES ;PER SECOND. HOWEVER, SINCE THE FILTER DOES NOT HAVE INFINITE ;ATTENUATION ABOVE 30 Hz IT IS NECESSARY TO SAMPLE AT A SOMEWHAT HIGHER ;RATE, AND THEN DISCARD THOSE SPECTRAL POINTS REPRESENTING SIGNALS ABOVE ;30 Hz. 1. ONE CONSIDERATION IN CHOOSING THE SAMPLING RATE IS THE ACTUAL RATE AVAILABLE WITH A GIVEN A/D CONVERTER. WITH THE CMC BUSSTER D16 A/D CONVERTER, SAMPLING TIMES CAN BE AS SMALL AS 0.0005 s. HOWEVER, IF MORE THAN ONE SIGNAL IS TO BE DIGITIZED AT ONE TIME, THE MINIMUM SAMPLING TIME IS 0.01 s PER CHANNEL, OR A SAMPLING RATE OF 100 SAMPLES/SECOND. THIS SEEMS LIKE A REASONABLE CHOICE. 2. A SECOND CONSIDERATION IS THE EFFECT OF THE SAMPLING RATE ON THE FREQUENCIES OF ALIASED POWER LINE HARMONICS. ONLY HARMONICS AT 60 AND 120 Hz ARE LIKELY TO BE A PROBLEM. WITH DT ? 0.01 S, THE NYQUIST RATE IS 50 Hz, SO THE SPECTRUM WILL CONTAIN POINTS AT FREQUENCIES FROM 0 TO 50 Hz. ANY 60' Hz SIGNAL THAT IS DIGITIZED WILL APPEAR IN THE SPECTRUM AT 40 Hz, WHICH POINT WILL BE THROWN OUT, SO 60 Hz INTERFERENCE WON'T BE A PROBLEM. HOWEVER, INTERFERENCE AT 120 Hz WILL APPEAR AT 20 Hz IN THE SPECTRUM, AND THIS FACT MUST BE KEPT IN MIND WHEN ANALYZING THE DATA. (HIGHER HARMONICS APPEAR AS: 180 AT 20 Hz, 24Z AT 40 Hz, 300 AT 0 Hz, 360 AT 40 Hz, AND SO ON.) ;GIVEN A SAMPLING TIME DT ? 0.01 s, WE CAN CALCULATE THE SPECTRAL SPACING ;FOR DIFFERENT CHOICES OF BLOCK SIZE NX, AND WE FIND THE FOLLOWING: NX DF NUMBER OF POINTS