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An Assessment of Potential Health Effects from Exposure to Pave Paws Low-Level Phased-Array Radiofrequency Energy 5 PAVE PAWS Exposure Conditions EXPOSURE CHARACTERISTICS The Radar and Its Signal To briefly review the radar description provided in Chapter 4, the PAVE PAWS radar is pulsed; it transmits a pulse sequence, and then is quiescent while the radar echoes return. Then another pulse sequence is transmitted and the process is repeated. Pulse widths vary from 250 microseconds to 16 milliseconds, and the listening period is at least 38 milliseconds. Some pulses vary in carrier frequency during the pulse, using a technique called “chirping” to improve range resolution. The carrier frequency varies from 420 MHz to 450 MHz. Signal bandwidths at the input to the final amplifiers range from 8 kHz for the narrowest pulse to 125 Hz for the widest pulse. The “chirp” bandwidth is 2 MHz. The antenna is comprised of two phased arrays, each located on a planar face, tilted back 20 degrees from vertical. The elements are located on a regular hexagonal lattice, and there are 1792 active elements per face and 885 passive elements. The elements are deployed in quadrantal symmetry to allow precise monopulse tracking of targets. The diameter of each array is approximately 72.5 ft. Each array face will support many more elements, but that expansion has not occurred, and the committee has been informed that there are no plans to expand the number of elements on the array. The elements are bent dipoles, each supported by a two-post balun. Bending down the arms avoids blind angles produced by dipole-balun mode interference. Crossed dipoles are used, thus providing both vertical and horizontal polarization. Both arms are hot; the two conductors supporting the dipole arms constitute a balun, which transforms the balanced dipole arm connection to an unbalanced coax; the latter connects to the module contain-
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An Assessment of Potential Health Effects from Exposure to Pave Paws Low-Level Phased-Array Radiofrequency Energy FIGURE 5-1 Measured module filter response. The filter minimizes the interference of PAVE PAWS to services such as cell phones, GPS, and other communications systems. Filter bandwidth is 115 MHz at 10 dB points. This figure shows the pass band (low attenuation for the radar frequencies [425-450 MHz], and high attenuation for harmonics; attenuation of 70 dB for second harmonic at 850 MHz; 68 dB for third harmonic at 1350 MHz; 31 dB for 4th harmonic at 1800 MHz; and 59 dB for fifth harmonic at 2100 MHz). This filter insures that the PAVE PAWS signal has very small harmonic content. Figure is reproduced with permission from Raytheon Company. ing the amplifier. This is a well known and widely used technology. Each quadrant has 14 subarrays, and each subarray has 32 transmit-receive (TR) modules and 32 active elements. The array main beam is steered by applying phase shift to each TR module. All modules are excited simultaneously; beam scan is provided by phase shift. Sidelobe levels are held 20 dB below the main beam by tapering: the inner subarrays have all active elements, while middle subarrays have some passive elements, and outer subarrays have more passive elements. Thus an amplitude taper is produced over the array (see Figure 5-4). Each TR module includes a bandpass filter to minimize interference caused by the radar. Filter bandwidth is 115 MHz at 10 dB points; the measured filter response is shown in Figure 5-1. Note that the filter skirts around 420 and 450 MHz are quite steep. This filter affects the pulse buildup and decay.
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An Assessment of Potential Health Effects from Exposure to Pave Paws Low-Level Phased-Array Radiofrequency Energy Measurements of the exciter output RF waveform are shown in Figures 5-2a, 5-2b, and 5-2c. Note that these appear inverted, due to the measuring equipment using negative detection. In Figure 5-2b the rise time is approximately 1 microsecond, with a gradual rise and gradual leveling off. Finally Figure 5-2c shows fall time, which is much slower, roughly 12 microseconds, and therefore no abrupt changes are evident. Note that the rise-time bandwidth is narrow (roughly 2 MHz). WAVEFORM DECAY Each PAVE PAWS dual polarized element is driven by a Class C (highly non-linear) amplifier; a second Class C amplifier drives all 64 element amplifiers in a sub-array; a third Class C amplifier drives all 56 sub-arrays. All of these amplifiers are “on” all the time; the radar exciter unit applies the waveform (pulse) to the amplifier driving the sub-arrays. Beam steering is provided by a phaser at each element module. Class C amplifiers tend to sharpen up transients, so the exciter buildup and decay times of roughly 1 and 12 microsec (Figures 5.2b and 5.2c) become typically 200 and 1000 nsec for the radiated signal. An examination of Phase IV buildup and decay pairs shows that these times are roughly equal, about 200 nsec (see Figures 5-6 and 5-11, which are expansions of Figures 3-48e and 3-53e in the AFRL (2003) Phase IV Time-Domain Waveform Characterization report. In a number of cases, a trailing-edge spike is larger than the main waveform. All of these are at wide angles from the main beam, where the sidelobe envelope is much lower. These spikes are probably due to two factors working together. First, the individual Class C amplifiers do not turn off alike, due to different resonant circuit Q (ratio of stored energy to dissipated energy), different gain, and other factors. Second, when all element contributions add in phase, the main beam is produced. Sidelobes and nulls are produced when the element contributions partly cancel, producing sidelobe levels away from the main beam 30-40 dB down (in power down to 0.001-0.0001 from 1). If amplifiers have typical gain variation of ±1 dB or even more, field-strength levels well above the steady-state sidelobe level are possible as the elements variously shut down. This is substantiated by calculations made by Tomlin for the PPPHSG.1 It should be noted that the discrete delay is not a possible cause here. Signal Propagation The radar signal power decays as 1/R2 in free space, but multipath signals are usually a problem at UHF. Multipath is caused by diffraction and reflection. For example, if a hill or slope blocks the direct radar signal, the signal can be re- 1 Jim Tomlin, Charts and Notes prepared for the PPPHSG, January 6, 2004. Jim Tomlin is a technical advisor to the PPPHSG.
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An Assessment of Potential Health Effects from Exposure to Pave Paws Low-Level Phased-Array Radiofrequency Energy FIGURE 5-2a Entire exciter waveform pulse (negative direction) taken from RF monitor example in T.O. 31P6-2FPS115-51, Chapter 6. FIGURE 5-2b Exciter output pulse (negative direction) rise time taken from RF monitor example in T.O. 31P6-2FPS115-51, Chapter 6. FIGURE 5-2c Exciter output pulse fall time (negative direction) taken from RF monitor example in T.O. 31P6-2FPS115-51, Chapter 6.
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An Assessment of Potential Health Effects from Exposure to Pave Paws Low-Level Phased-Array Radiofrequency Energy flected or diffracted by towers, buildings, power lines, or other obstacles and can reach areas that are not line-of-sight from the radar. These multipath signals need not be in the direction of the observer; they may arrive sideways. Reflected multipath is provided by many types of metallic structures: metal lighting poles; fence poles and wire; rebars in concrete; and telephone cable and power wires, to mention a few. These multipath signals are well known, and can easily disrupt the 1/R2 energy falloff. Almost certainly the anomalous Phase IV measurements are due to multipath. The question of surface waves has been raised by concerned Cape Cod citizens. However, it has been accepted for 50 years that the longitudinal field component that may exist at HF, VHF, and UHF is not a surface wave. Sommerfeld in his classic 1909 work (Sommerfeld 1914) made a sign error, according to Norton (1937) and others in several papers. There is recent evidence by Collin (2004) that the original sign was correct, but in either case the earth does not support a surface wave. The waves are now called “ground waves”; the vertical electric field tilts just enough to satisfy the lossy boundary conditions in the ground. The term “surface wave” has for at least 40 years referred to slow waves, waves with velocity less than that of light, and usually supported by reactive surfaces. At 435 MHz, ground waves attenuate rapidly. Using sandy soil (epsilon = 10, σ = .002 S/ m), the radiation is attenuated 40 dB (0.0001 in power, 0.01 in field) over a distance of 120 m (400 ft) . Outside the safety fence, the ground wave should be too small to measure. Use of the formulas of Baños, as suggested, is not recommended. They are excellent for dipoles in earth, or dipoles very close to earth, but are error prone for separations of a wavelength or more. Although it has been implied that the measured radial fields (radial waves) represent a new and unexpected phenomenon, they are just the result of multipath and simple geometry. As sketched in Figure 5-3a, the line of sight during the Phase IV measurements was not horizontal, but was inclined down about 2 degrees. Since the electric field at the measurement point is perpendicular to the line of sight, it can be resolved into a large vertical component and a small horizontal or longitudinal component. For many points on Cape Cod, the line of sight angle is larger, leading to a larger longitudinal component. At UHF frequencies multipath is a well known and serious problem. Metallic structures including towers, power lines, and rebars in concrete, that are inclined or curved, will convert vertically polarized fields into horizontally polarized fields. Even curved earth hills can produce polarization conversion. It is difficult if not impossible to compute the combined multipath effects in a given environment. The multipath contributions and the horizontal field due to line of sight tilt combine to produce a longitudinal E field. (See Figure 5-3b taken from 3-92c, and Figure 5-3c taken from 3-96c of the Phase IV report.) Because this field is parallel to ground, and the sensor is roughly two wavelengths above it, there are also ground reflection effects. The derivative sensors used in the measurements have very broad pat-
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An Assessment of Potential Health Effects from Exposure to Pave Paws Low-Level Phased-Array Radiofrequency Energy FIGURE 5-3a Vector resolution of PP electric field into vertical and longitudinal component. NOTE: This figure has been changed since the original prepublication version to correct an error. FIGURE 5-3b Vertical field amplitude (from 3-92.c of the waveform report). FIGURE 5-3c Radial field amplitude (from 3-96.c of the waveform report).
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An Assessment of Potential Health Effects from Exposure to Pave Paws Low-Level Phased-Array Radiofrequency Energy terns, and pickup signals from many directions. It would be better physics to call the field a “longitudinal component.” Time Delay in Large Antennas It was suggested by Dr. Albanese2 that phased-array radars are different from other radars due to their discrete time delay. This is one of the key issues relating to PAVE PAWS effects and it is examined thoroughly here. In the far-field of a large phased array or reflector antenna, the contributions from all parts of the antenna arrive at the main beam peak simultaneously (broadside beam for a phased array). At other angles, there is a differential delay as the energy from the closest part of the array or reflector arrives first, while that from the farthest part arrives last. Of course this applies primarily to pulsed signals. For the reflector, the pattern buildup starts at 90 degrees from the axis due to the currents on the reflector edge (see Hansen 1987; Hansen and Kramer 1992) and the pattern builds up slowly and continuously. With a phased array, the pattern builds up slowly but in a discrete stair-step fashion. Due to the large number of elements, the stair has many very small steps. As expected, the effect of those small steps does not appear in the waveform measurement (see Figure 5-6). In the near-field region (distance generally less than 2000 ft), there are delays also in forming the main beam. For the phased array, the near-field stair-step buildup of the waveform is expected to be very close to a continuous buildup. For a reflector antenna, the near-field buildup is more complex. At angles away from the normal to the face of the array, there is a time delay between energy arriving from the closest element and that arriving from the farthest element, since all elements are turned on simultaneously. This delay, in amplitude and phase, has been computed for the PAVE PAWS radar. The active array is 72.5 feet wide. A worst case scenario is postulated: the beam is scanned to the farthest left position of 60 degrees azimuth, and to the lowest elevation position −17 degrees (3 degrees above the horizon). The observation point is 60 degrees right azimuth, and −20 degrees elevation (on the horizon). A computer program was written to calculate the waveform buildup. The x-y coordinates of the 1792 excited elements were provided on a disk by Mitre. Figure 5-4 shows the positions of the active elements. They are closely spaced around the center but space tapering is used in the outer portion, to control the sidelobe level. 2 Dr. Albanese presented his theories to the committee in open sessions of committee meetings on several occasions and by letter. A number of causal hypotheses were also presented in a letter to the PPPHSG dated July 30, 2001, and the committee has also evaluated responses to these hypotheses made by Dr. Robert Adair in a journal commentary (Adair, R. K. 2003. Environmental Objections to the PAVE PAWS Radar System: A Scientific Review. Radiat Res 159:128-134).
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An Assessment of Potential Health Effects from Exposure to Pave Paws Low-Level Phased-Array Radiofrequency Energy FIGURE 5-4 Positions of the active PAVE PAWS elements. Using the observation direction, the projected distance from each element to the first element (center row, right side) is calculated for the 1792 elements. The projected distances are calculated using direction cosines, where the polar angle θ is measured from the normal to the array face, and the azimuth angle Φ is measured in a horizontal plane from normal to the surface. Since those with the smallest projected separation contribute first, the array of projected separations is ordered in ascending order by a well-known subroutine called HEAPSORT. Because the excitation phases associated with the main beam position affect the phase of the buildup, the x and y coordinates are sorted in consonance with the projected separations. The delay time across the array is roughly 74 nanoseconds; the delay for the worst case mentioned above is 60 nanoseconds. In order to get a fine-grain picture of how the elements contribute, the time line is divided into 12,000 steps of roughly 5 picoseconds each. The time stepping starts at 0 at the right-most reference element and proceeds on. When it has encompassed the next closest element, the contribution of that element with the appropriate scan phase
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An Assessment of Potential Health Effects from Exposure to Pave Paws Low-Level Phased-Array Radiofrequency Energy and unity amplitude is added in. As the time step proceeds, more and more elements are added until the opposite side of the array is reached. Since the phase and amplitude are both a result of stair-step contributions, no smoothing or interpolation has been used in the plots. Figure 5-5a shows the amplitude buildup for the extreme case mentioned above. This curve is made of 1790 stair steps, although they are not visible due to the scale. But a portion of the delay time is expanded in Figure 5-5b, where the steps are clearly visible. The delays range from 5 psec (or less, as this is the least count) to roughly 100 psec. Note that the height of the large steps is roughly 4 × 10−3 times the final height, and that is the level of a far-out sidelobe, perhaps 1 × 10−4 times the main beam power. So a typical step represents a power step of the order of 4 × 10−7 times the main beam power. Figure 5-5c gives the phase buildup; the first step is an artifact due to the plotting program starting at zero phase. Note that the calculations were made along one of the four directions (axes) of symmetry, which is a worst case. If a slightly different azimuth angle had been used, the distance steps would be less regular, and the buildup would be even smoother. These incremental delays, as radiation from antenna elements appear, are very much smaller by comparison to the rise times (less than a factor of a thousand) produced by the TR modules, as discussed below. Total phase change during buildup is very modest. Thus the phased-array delay is expected to produce a negligible effect; the waveform rise time is very gradual. Buildup is similar to that of a large parabolic dish antenna system. The PAVE PAWS Phase IV measurement program produced data that are relevant to the effects of time delay, both in arrays, and in reflectors. All of the graphs presented below are excerpts of the digital data provided to the committee by AFRL. First, the PP waveform buildup at 60 degrees from the array normal (from Figure 3-48e of the waveform report) (AFRL 2003) is shown in Figure 5-6. The PP waveform buildup near normal (from Figure 3-46b in the waveform report) is shown in Figure 5-7. At center frequency of 435 MHz the maximum delay in Figure 5-6 is 63.8 nsec, or 28 carrier cycles. The time-delay period extends over roughly one-third of the rise time in Figure 5-6. As expected from the buildup calculations just discussed, there is no apparent indication in Figure 5-6 that the discrete delay has any effect. Figure 5-7, near normal, incurs negligible delay; the slight irregularities in amplitude occur equally in both. Before buildup starts, the data show noise and interference; this probably accounts for the later small irregularities. The committee notes that the Air Force Phase IV report revisions incorrectly assume time-delay beam steering, instead of phase beam steering. For comparison Figure 5-8 shows buildup for a single PP element. The envelope is smoother, but the pre-buildup noise is smaller than in Figures 5-6 and 5-7. Similarly, the Phase IV measurements on two PP elements, with an introduced 50 nsec delay, are indistinguishable from those of a single element.
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An Assessment of Potential Health Effects from Exposure to Pave Paws Low-Level Phased-Array Radiofrequency Energy FIGURE 5-5a PAVE PAWS waveform buildup, az = 60 degrees, el = 0 degrees. FIGURE 5-5b PAVE PAWS waveform buildup, expanded scale. FIGURE 5-5c PAVE PAWS waveform buildup. az = 60 degrees, el = 0 degrees.
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An Assessment of Potential Health Effects from Exposure to Pave Paws Low-Level Phased-Array Radiofrequency Energy FIGURE 5-6 Array buildup; 60 degrees off normal. FIGURE 5-7 Array buildup; near normal to array face.
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An Assessment of Potential Health Effects from Exposure to Pave Paws Low-Level Phased-Array Radiofrequency Energy Oughstun and colleagues have published many informative papers; almost all concern laser (IR) waveforms. Even their papers in Radio Science are on optical (IR) waveforms. 3. T.M. Roberts, “Radiated Pulses Decay Exponentially in Materials in the Far Fields of Antennas,” Electronics Ltrs., Vol. 38, 4 July 2002, 679-680 This salient paper shows that low-frequency spectral components of a waveform can produce a decay rate in dispersive material that is lower than that of the carrier frequency. In a linear medium, and at low power levels, tissue is linear and all spectral components decay exponentially. See also: 4. T.M. Roberts and P.G. Petropoulos, “Asymptotics and Energy Estimates for Electromagnetic Pulses in Dispersive Media,” J. Opt. Soc. Amer. A, Vol. 13, June 1996, 1204-1217 and “Addendum,” J. Opt. Soc. Amer. A, Vol. 16, 1999, 2799-2800 5. T.M. Roberts, “Measured and Predicted Behavior of Pulses in Debye-and Lorenz-Type Materials.” Trans. IEEE AP-52 Jan. 2004. 310-314. Asymptotic calculations are shown to validate precursor measurements made using liquid-filled coax cables by AFRL contractors (see Annex 2). Results show algebraic decay after significant attenuation has occurred. Signal bandwidth was approximately 10 GHz; the widest PAVE PAWS bandwidth is 5 MHz, or 2000 times smaller. PAVE PAWS precursors will be too small to be measurable. 6. L.D. Bacon, “Calculations of Precursor Propagation in Dispersive Dielectries,” SAND 2003-3040, Aug. 2003, Sandia National Laboratories Dr. Larry Bacon of Sandia National Laboratories has calculated waveform propagation in lossy dispersive media. These cases utilized a carrier frequency of 435 MHz, which is in the middle of the PAVE PAWS band. Pure water was the medium. He used a narrow-band (1 microsecond) pulse train, and a wideband (10 nanosecond) pulse train. Note that the narrow-band pulse has about the same bandwidth as the widest PAVE PAWS waveform. Each pulse train was utilized without, and with, a filter. The 1 microsecond waveform used a 10 MHz wide filter, while the 10 nanosecond waveform used a 200 MHz wide filter. The two filter bandwidths are shown in Figure 5-A3.1. The wideband unfiltered waveform displayed at 1meter depth in the medium a precursor, small compared to the main signal; at 5-meter depth, the precursor was larger than the signal but very small compared to the signal at 1 meter. When the wideband filter was applied, no precursors were visible. The narrow-band unfiltered waveform displayed at 1-meter depth in the medium a very small precursor; at 5-meter depth the precursor was again larger than the signal but very small compared to that at 1 meter. With the filter applied,
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An Assessment of Potential Health Effects from Exposure to Pave Paws Low-Level Phased-Array Radiofrequency Energy FIGURE 5-A3.1 10 MHz (dotted) and 200 MHz (solid) bandpass filter frequency responses. which represents the PAVE PAWS radar, a slow buildup was observed at all depths, as seen in Figure 5-A3.2. No precursors were evident. However, at great depth in the medium, a precursor is visible but its amplitude is below the incident amplitude by a factor of roughly 100 million. Such small values are way below the natural noise level, hence are not measurable. Because of the narrow bandwidth of the 1 microsecond waveform, all spectral (Fourier) components decay essentially exponentially, producing the classic “skin depth.” Figure 5-A3.3 shows waveform decay over a 20-meter depth; this waveform decays exponentially just like all narrow-band waveforms. Exponential decay is linear on a logarithmic scale (decibels). In summary, wideband waveforms do produce observable precursors. Narrowband waveforms, such as those of PAVE PAWS, do not produce measurable precursors. 7. D.C. Stoudt, F.E. Peterkin, and B.J. Hankla, “Transient RF and Microwave Pulse Propagation in a Debye Medium (Water),” NSWC report JPSTC CRF-005-03, Dahlgren, VA, Sept. 2001 This work concerns frequencies below 2 GHz, where water shows a nearly constant permittivity but a varying conductivity with frequency. Accordingly, group and signal velocity dispersion can be neglected, and the Debye dispersion model is adequate. The propagation of waveform is analyzed using Fourier Trans-
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An Assessment of Potential Health Effects from Exposure to Pave Paws Low-Level Phased-Array Radiofrequency Energy FIGURE 5-A3.2 Leading edge of 1 µsec signal at various depths; baselines are offset for clarity. FIGURE 5-A3.3 Energy decay of 1 µsec signal, with 10 MHz filtering.
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An Assessment of Potential Health Effects from Exposure to Pave Paws Low-Level Phased-Array Radiofrequency Energy forms; the resulting frequency spectra are propagated through the lossy media, then inverse transformed into a waveform. Waveforms used include an ideal 10-cycle, 1 GHz pulse, a 6-cycle, 400 MHz pulse, and these two with a more practical trapezoidal envelope on the 1 GHz waveform. These calculations agree with those of Albanese (see reference 13, this section). For the square-wave modulated 1 GHz signal, at a depth of 75 cm (2.5 ft.), the fore and aft precursors are much larger than the main 10-cycle waveform. At the much shorter depths representative of humans, the waveform would be much larger than the precursor. When the modulation is trapezoidal, the precursors are only slightly larger than the main signal, at the same 75 cm depth. Bandwidth of both signals is roughly 200 MHz. For depths so large that the main signal has disappeared due to strong attenuation, the precursor decays approximately as , thus validating the one-term series approximation of Oughstun. The 6-cycle, 400 MHz signal, with ideal square-wave modulation (instant turn on), shows only a precursor slightly larger than the main signal, at a depth of 1.5 m (4.9 ft). Bandwidth is roughly 130 MHz. These calculations show that for 400 MHz, even with the large bandwidth associated with the 6-cycle waveform, precursors are negligible at the limited tissue depth available in humans. 8. K. Moten, C.H. Durney, and T.G. Stockham, “Electromagnetic Pulse Propagation in Dispersive Planar Dielectrics,” Bioelectromagnetics, Vol. 10, 1989, 35-49 This paper investigates a plane-wave pulse-train incident on a lossy dispersive slab, using Fast Fourier Transform techniques. Calculations show that wideband pulses can produce significant precursors. However, “the narrower the bandwidth of the pulse train, the less the difference between the pulse response and CW response.” And, “only very broadband pulsed systems could be expected to produce results that differ significantly from those of CW systems.” Pulse penetration depends on the dispersive nature of the dielectric medium and the Fourier coefficients (bandwidth) of the waveform. 9. R. Albanese, J. Penn, and R. Medina, “Ultrashort Pulse Response in Nonlinear Dispersive Media,” in Ultra-Wideband, Short-Pulse Electromagnetics, H.L. Bertoni, L. Carin, and L.B. Felsen, Eds., Plenum, 1993, 259-265 see also: 10. R. Albanese, J. Penn, and R. Medina, “Short-Rise-Time Microwave Pulse Propagation through Dispersive Biological Media,” J. Opt. Soc. Amer. A, Vol. 6, Sept. 1989, 1441-1446 These papers use Fourier series (of the waveform) as an analysis tool. Their
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An Assessment of Potential Health Effects from Exposure to Pave Paws Low-Level Phased-Array Radiofrequency Energy calculations used a waveform with 10 carrier cycles with a carrier frequency of 1 GHz. The waveform buildup was instantaneous; the envelope was a square wave. At 1.5 m distance the rise time affected the precursor amplitude, with longer rise time reducing the amplitude. However, at this distance the main signal is very small and the precursors are also small. 11. R. Albanese, J. Blaschak, R. Medina, and J. Penn, “Ultrashort Electromagnetic Signals: Biophysical Questions, Safety Issues, and Medical Opportunities,” Aviation, Space, and Environmental Medicine, May 1994, A116-A120 This paper shows a 1 nanosecond wideband pulse of 10 carrier cycles, carrier frequency 10 GHz. Both Sommerfeld- and Brillouin-calculated precursors appear after propagating 1 cm in pure water. Also shows precursors produced by laser (IR) radiation. Possible cellular effects of very high electric fields (hundreds or thousands of kW/m) are discussed. 12. R.A. Albanese, “An Electromagnetic Inverse Problem in Medical Science,” Chapter 2 of Invariant Imbedding and Inverse Problems, SIAM, 1992. 30-41 Using a square-wave modulation containing 5 carrier cycles, with a 3 GHz carrier frequency, a waveform with Brillouin precursors was calculated at 10 cm. depth. With no noise, partial results were obtained, but with very weak added noise there were no results. 13. R.A. Albanese, R.L. Medina, and J.W. Penn, “Mathematics, Medicine, and Microwaves,” Inverse Problems, Vol. 10, 1994, 995-1007 This paper shows a 1 nanosecond wideband pulse of 10 carrier cycles, carrier frequency 10 GHz. Both Sommerfeld-and Brillouin-calculated precursors appear after propagating 1 cm in pure water. Most of the paper concerns the inverse problem: given the response, find the dielectric and loss properties of the material. 14. E.L. Mokole and S.N. Samaddar, “Transmission and Reflection of Normally Incident, Pulsed Electromagnetic Plane Waves upon a Lorentz Half-Space,” J. Opt. Soc. Amer. B, Vol. 16, May 1999, 812-831 Both reflected and transmitted fields are calculated for a semi-infinite medium; the incident waveform is a single laser pulse at IR (frequency ~2 THz). As expected, this extremely wideband waveform produces strong Sommerfeld precursors. 15. S.L. Dvorak, “Exact, Closed-Form Expressions for Transient Fields in Homogeneously Filled Waveguides,” Trans. IEEE, Vol. MTT-42, Nov. 1984. 2164-2170
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An Assessment of Potential Health Effects from Exposure to Pave Paws Low-Level Phased-Array Radiofrequency Energy see also: 16. S.L. Dvorak and D.G. Dudley, “Propagation of Ultra-Wide-Band Electromagnetic Pulses through Dispersive Media,” Trans. IEEE, Vol. EMC-37, May 1995, 192-200 Using the Incomplete Lipschitz-Hankel Integrals (ILHI), waveform propagation in a waveguide is studied. Waveguides provide dispersion. The waveform used is a single cycle of a sine wave. Calculations show significant precursors; the waveform bandwidth is very wide. Prior experimental work of Pleshko is not mentioned, but the precursor increases in frequency as it propagates, just as measured by Pleshko. ANNEX 5-4: RELATED PAPERS ON PRECURSORS 1. Albanese, R.A. and E.L. Bell, Radiofrequency Radiation and Living Tissue: Theoretical Studies, report SAM-TR-79-41, Dec. 1979 This interim report models possible interactions of RF energy and cells. No distinction is made between thermal effects and pulsed effects. 2. Albanese, R.A. and E.L. Bell, “Radiofrequency Radiation and Chemical Reaction Dynamics,” in Nonlinear Electrodynamics in Biological Systems, W. R. Adey and A. F. Lawrence, Eds., Plenum, 1984, 277-285 Treated in this paper are high field strengths (100 to 2000 V/m) where the media are non-linear. There is no relevance to PAVE PAWS, where the field strengths are low, and the media are linear. 3. Albanese, R.A., R. Medina, and J. Penn, “Mathematics and Electromagnetic Theory,” unpublished and undated paper, circa 2001 The statement “frequency dependence in the frequency domain implies local tissue memory in the time domain” is too general to have meaning. Certainly, frequency spectrum and time waveform are related. But this does not necessarily imply tissue memory. The entire paper is not concerned with pulses. 4. Papazoglou, T.M., “Transmission of a Transient Electromagnetic Plane Wave into a Lossy Half-Space,” J. Appl. Phys., Vol. 46, Aug. 1975, 3333-3341 see also: 5. Dudley, D.G., T.M. Papazoglou, and R.C. White, “On the Interaction of a Transient Electromagnetic Plane Wave and a Lossy Half-Space,” J. Appl. Phys., Vol. 45, March 1974, 1171-1175 Propagation of a single Gaussian type pulse (slow rise time and fall time) into a lossy medium is considered. One case of interest uses a lossy and disper-
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An Assessment of Potential Health Effects from Exposure to Pave Paws Low-Level Phased-Array Radiofrequency Energy sive medium (earth). Waveforms with and without dispersion are very much the same, probably due to the narrow bandwidth of the incident pulse. No precursors were evident. 6. Devaney, A.J., “Linearized Inverse Scattering in Attenuating Media,” Inverse Problems, Vol. 3, 1987. 389-397 Dr. Devaney has extended this work to dispersive media, but it has not been published. The aim was to see if precursors could help in the inverse problem. Note, the inverse problem is: given the response, find the details of the scatterer or the details of the medium. Pulse Propagation in Lossy Media Researchers from Harvard have published papers on pulse propagation in sea water, a highly lossy medium. Single pulses and a pulse of carrier oscillations have been considered. These papers utilize a dipole as source, unlike the plane-wave source of Oughstun and colleagues. The dipole near-field greatly complicates the analysis. The papers show that the rise and fall times each produce a transient, with the carrier oscillations in between. When the rise and fall times are slow, two things occur. First, the lower frequencies in the transient allow them to decay more slowly than does the carrier. So after some distance, the carrier may be smaller than the transient waveform. These are probably not precursors in the Brillouin sense. Second, the amplitude of the transient is reduced by f2rs/(f2 + f2rs), where f is the carrier frequency and frs is the principal frequency of the rise time. Thus, if the rise time equals 20 carrier cycles, the rise-time transient amplitude is reduced by 0.0025, or 52 dB. 1. King, R.W.P. and T.T. Wu, “The Propagation of a Radar Pulse in Sea Water,” J. Appl. Phys., Vol. 73, 15 Feb. 1993, 1581-1590 see also: 2. King, R.W.P. and T.T. Wu, Erratum: “The Propagation of a Radar Pulse in Sea Water,” J. Appl. Phys., Vol. 77, 1 April 1995, 3586-3687 3. King, R.W.P., “The Propagation of a Gaussian Pulse in Sea Water and Its Application to Remote Sensing,” Trans. IEEE, Vol. GRS-31, May 1993, 595-605 4. King, R.W.P., “Propagation of a Low-Frequency Rectangular Pulse in Seawater,” Radio Science, Vol. 28, May-June 1993, 299-307 5. Margetis, D., “Pulse Propagation in Sea Water,” J. Appl. Phys., Vol. 77, 1 April 1995, 2884-2888
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An Assessment of Potential Health Effects from Exposure to Pave Paws Low-Level Phased-Array Radiofrequency Energy 6. Margetis, D., “Pulse Propagation in Sea Water: The Modulated Pulse,” Progress in Electromagnetics Research, Vol. 26, 2000, 89-110 The prediction by Song and Chen that early arrival and late arrival parts of a waveform in lossy media decay algebraically (as 1/R3 or 1/R5) has been shown to be incorrect by Margetis and King: 7. Song, J. and K-M Chen, “Propagation of EM Pulses Excited by an Electric Dipole in a Conducting Medium,” Trans. IEEE, Vol. AP-41, 1993, 1414-1421 8. Margetis, D. and R.W.P. King, “Comments on ‘Propagation of EM Pulses Excited by an Electric Dipole in a Conducting Medium,’” Trans. IEEE, Vol. AP-43, Jan 1995, 119-120 9. Wait, J.R., “Electromagnetic Fields of Sources in Lossy Media,” Chapter 24 in Antenna Theory, Part II, R.E. Collin and F.J. Zucker, Eds., McGraw-Hill, 1969 This paper treats single-pulse propagation in lossy (non-dispersive) media. Extensive references are provided. ANNEX 5-5: PAPERS BY PROFESSOR OUGHSTUN AND COLLEAGUES These papers are concerned with wideband optical (laser) short pulses in media that are lossy and dispersive. No discussions of the effects of waveform bandwidth are given. These papers are listed because they are often cited for PAVE PAWS. However the very narrow-band nature of the PAVE PAWS signal makes all of these papers irrelevant to the PAVE PAWS problem. And the laser frequency is roughly 10,000,000 times higher than that of PAVE PAWS. 1. Oughstun, K.E. and G.C. Sherman, “Propagation of Electromagnetic Pulses in a Linear Dispersive Medium with Absorption (the Lorentz Medium),” J. Opt. Soc. of Am. B, Vol. 5, April 1988, 817-849 2. Oughstun, K.E. and S. Shen, “Velocity of Energy Transport for a Time Harmonic Field in a Multiple-Resonance Lorentz Medium,” J. Opt. Soc. of Am. B, Vol. 5, Nov. 1988, 2395-2398 3. Shen, S. and K.E. Oughstun, “Dispersive Pulse Propagation in a Double-Resonance Lorentz Medium,” J. Opt. Soc. of Am. B, Vol. 6, May 1989, 948-963
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An Assessment of Potential Health Effects from Exposure to Pave Paws Low-Level Phased-Array Radiofrequency Energy 4. Wyns, P., D.P. Foty, and K.E. Oughstun, “Numerical Analysis of the Precursor Fields in Linear Dispersive Pulse Propagation,” J. Opt. Soc. of Am. A, Vol. 6, Sept. 1989, 1421-1429 5. Oughstun, K.E. and J.E.K. Laurens, “Asymptotic Description of Ultrashort Electromagnetic Pulse Propagation in a Linear, Causally Dispersive Medium,” Radio Science, Vol. 26, Jan.-Feb. 1991, 245-258 6. Oughstun, K.E., “Pulse Propagation in a Linear, Causally Dispersive Medium,” Proc. IEEE, Vol. 79, Oct. 1991, 1379-1390 7. Oughstun, K.E. and J.E.K. Laurens, “Asymptotic Description of Electromagnetic Pulse Propagation in a Linear Dispersive Medium,” in Ultra-Wideband, Short-Pulse Electromagnetics, H. Bertoni et al,. Eds., Plenum Press, 1993, 223-240 8. Balictsis, C.M. and K.E. Oughstun, “Uniform Asymptotic Description of Ultrashort Gaussian Pulse Propagation in a Causal, Dispersive Dielectric,” Phys. Rev. E, Vol. 47, 1993, 3645-3669 9. Balictsis, C.M. and K.E. Oughstun, “Uniform Asymptotic Description of Gaussian Pulse Propagation of Arbitrary Initial Pulse Width in a Linear, Causally Dispersive Medium,” in Ultra-Wideband, Short-Pulse Electromagnetics 2, L. Carin and L.B. Felsen, Eds., Plenum Press, 1994, 273-283 10. Smith, P.D. and K.E. Oughstun, “Electromagnetic Energy Dissipation of Ultrawideband Plane Wave Pulses, in a Causal, Dispersive Dielectric,” in Ultra-Wideband, Short-Pulse Electromagnetics 2, L. Carin and L.B. Felsen, Eds., Plenum Press, 1994, 285-295 11. Oughstun, K.E., “Transient in Chiral Media with Single Resonance Dispersion: Comments, Jour. Opt. Soc. of Am. A, Vol. 12, 1995, 626-628 12. Sherman, G.C. and K.E. Oughstun, “Energy-Velocity Description of Pulse Propagation in Absorbing, Dispersive Dielectrics,” J. Opt. Soc. of Am. B, Vol. 12 Feb. 1995, 229-247 13. Oughstun, K.E., “Dynamical Structure of the Precursor Fields in Linear Dispersive Pulse Propagation in Lossy Dielectrics,” in Ultra-Wideband, Short-Pulse Electromagnetics 2, L. Carin and L.B. Felsen, Eds., Plenum Press, 1995, 257-272
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An Assessment of Potential Health Effects from Exposure to Pave Paws Low-Level Phased-Array Radiofrequency Energy 14. Oughstun, K.E., “Noninstantaneous, Finite Rise-Time Effects on the Precursor Field Formation in Linear Dispersive Pulse Propagation,” J. Opt. Soc. of Am. A, Vol. 12, Aug. 1995, 1715-1729 15. Marozas, J.A. and K.E. Oughstun, “Electromagnetic Pulse Propagation Across a Planar Interface Separating Two Lossy, Dispersive Dielectrics,” in Ultra-Wideband, Short-Pulse Electromagnetics 3, C. Baum, L. Carin, and A. P. Stone, Eds., Plenum Press, 1996, 217-230 16. Oughstun, K.E. and C.M. Balictsis, “Gaussian Pulse Propagation in a Dispersive, Absorbing Dielectric, “Phys. Rev Ltrs., Vol. 77, 9 Sept. 1996, 2210-2213 17. Oughstun, K.E. and Hong Xiao, “Failure of the Quasimonochromatic Approximation for Ultrashort Pulse Propagation in a Dispersive, Attenuative Medium,” Phys. Rev. Ltrs., Vol. 78, 27 Jan. 1997, 642-645 18. Balictsis, C.M. and K.E. Oughstun, “Generalized Asymptotic Description of the Propagated Field Dynamics in Gaussian Pulse Propagation in a Linear, Causally Dispersive Medium,” Phys. Rev. Ltrs. E, Vol. 55, Feb 1997, 1910-1921 19. Xiao, H. and K.E. Oughstun, “Hybrid Numerical-Asymptotic Code for Dispersive Pulse Propagation Calculations, Jour. Optical Society of America A, Vol. 15, 1998, 1256-1267 20. Solhaug, J.A., K.E. Oughstun, J.J. Stamnes, and P.D. Smith, “Uniform Asymptotic Description of the Brillouin Precursor in a Lorentz Model Dielectric,” Jour. European Opt. Soc. A., Pure and Applied Optics, Vol. 7, 1998, 575-602 21. Oughstun, K.E., “The Angular Spectrum Representation and the Sherman Expansion of Pulsed Electromagnetic Beam Fields in Dispersive, Attenuative Media,” Jour. European Opt. Soc. A., Pure and Applied Optics, Vol. 7, 1998, 1059-1078 22. Solhau, J.A., J.J. Stamnes, and K.E. Oughstun, “Diffraction of Electromagnetic Pulses in a Single-Resonance Lorentz Model Dielectric,” Jour. European Optical Soc. A., Pure and Applied Optics, Vol. 7, 1998, 1079-1101 23. Smith, P.D. and K.E. Oughstun, “Electromagnetic Energy Dissipation and Propagation of an Ultrawideband Plane Wave Pulse in a Causally Dispersive Dielectric,” Radio Science, Vol. 33, 1998, 1489-1504
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An Assessment of Potential Health Effects from Exposure to Pave Paws Low-Level Phased-Array Radiofrequency Energy 24. Xiao, H. and K.E. Oughstun, “Failure of the Group-Velocity Description for Ultrawideband Pulse Propagation in a Causally Dispersive, Absorptive Dielectric,” J. Opt. Soc. Am. B, Vol. 16, Oct. 1999, 1773-1785 25. Laurens, J.E.K. and K.E. Oughstun, “Electromagnetic Impulse Response of Triply-Distilled Water,” Ultra-Wideband, Short-Pulse Electromagnetics 4,” Heyman et al,. Eds., Kluwer Academic/Plenum Publ., 1999, 243-264 26. Smith, P.D. and K.E. Oughstun, “Ultrawideband Electromagnetic Pulse Propagation in Triply Distilled Water,” Ultra-Wideband, Short-Pulse Electromagnetics 4,” Heyman et al, Eds., Kluwer Academic/Plenum Publ., 1999, 265-276 27. Oughstun, K.E. and H. Xiao, “Influence of Precursor Fields on Ultrashort Pulse Autocorrelation Measurements and Pulse Width Evolution,” Optics Express, Vol. 8, 9 April 2001, 481-491 28. Oughstun, K.E. and H. Xiao, “Influence of the Precursor Fields on Ultrashort Pulse Measurements,” in Ultra-Wideband, Short-Pulse Electromagnetics 5, P.D. Smith and S.R. Cloude, Eds., Kluwer Academic/Plenum Publ., 2002, 569-576 29. Oughstun, K.E. “Asymptotic Description of Ultrawideband, Ultrashort Pulsed Electromagnetic Beam Field Propagation in a Dispersive, Attenuative Medium,” in Ultra-Wideband, Short-Pulse Electromagnetics 5, P.D. Smith and S.R. Cloude, Kluwer Academic/Plenum Publi, 2002, 687-696
Representative terms from entire chapter: