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A Major concern in the past years was the traditional static spectrum allocation which gave rise to spectrum underutilization and scarcity in wireless networks. In an attempt to solve this problem, cognitive radios technology was proposed and this allows a spectrum to be accessed dynamically by Cognitive radio users or secondary users (SUs). Dynamic access can efficiently be achieved by making necessary adjustment to some MAC layer functionalities such as sensing and channel allocation. MAC protocols play a central role in scheduling sensing periods and channel allocation which ensure that the interference is reduced to a tolerable level. In order to improve the accuracy of sensing algorithm, necessary adjustments should be made at MAC layer. Sensing delays and errors are major challenges in the design of a more accurate spectrum sensing algorithm or MAC protocol. Proposed in this study, is a scheme (EXGPCSA) which incorporate sensing at the MAC layer and physical layer. Energy detector was used to detect the presence of primary users (SU). A choice of how long and how often to sense the spectrum was addressed at the MAC layer. The focal point of this study was on minimizing delays in finding available channels for transmission. EXGPCSA used channel grouping technique to reduce delays. Channels were divided into two groups and arranged in descending order of their idling probabilities. Channels with higher probabilities were selected for sensing. Three network scenarios were considered wherein a group of SUs participated in sensing and sharing their spectral observations. EXGPCSA was designed such that only SUs with higher SNR were allowed to share their observations with other neighbouring SUs. This rule greatly minimized errors in sensing. The efficiency of EXGPCSA was evaluated by comparing it to another scheme called generalized predictive CSA. A statistical t-test was used to test if there is significant difference between EXGPCSA and generalized predictive CSA

Communications, electronics, and sensor systems aboard U.S. naval ships and submarines must operate effectively in order to support the execution of military missions and operations. Whether operating alone or with coalition forces, the Navy must be prepared to execute its missions anywhere in the world and under any condition. We must also be prepared to operate effectively throughout the entire frequency spectrum. As such, the Navy's systems must operate and interoperate safely and effectively without interfering with or degrading the system performance of other systems aboard ship. It is also necessary that U.S. systems do not impact, or be impacted by, other coalition or adversary systems operating in the same electromagnetic environment. This issue of The Leading Edge, sponsored by the NAVSEA Warfare Centers, is dedicated to the critically important area of electromagnetic environmental effects, otherwise referred to as E3. It is an area that touches all naval operations -- afloat and ashore, and all spectrums of conflict. So, whether the Navy's actions involve combating traditional adversaries, countering terrorism, thwarting pirates, responding to natural disasters, or supporting humanitarian operations, the Navy's systems must operate effectively and reliably in the electromagnetic environment in order for its missions to succeed. Ensuring that the Navy's missions succeed underlies one of the NAVSEA Warfare Centers' most important roles., Published in LeadingEdge, v7 i1, 2009.

Surgical resection is the best option for both liver and kidney cancers, which providing the long term survival. However intraoperative bloodloss can be a significant challenge, and is clearly associated with morbidity and mortality. Radiofrequency ablation (RFA) precoagulationhas been introduced into liver and kidney surgery. Promising results have already achieved in reduction of intraoperative blood loss. In thisthesis, a detailed explanation on precoagulation by RFA has been given.Our group developed a novel bipolar multi-array RFA device – InLine (ILRFA). In this thesis, we have investigated the performance in a variety of fields. In the study of ILRFA-assisted laparoscopic liver resection, ILRFA was easily employed through a hand port and achievedsignificant decrease of blood loss compared to control group (p < 0.05).In the liver trauma study, ILRFA produced a 63.88% reduction of blood loss in peripheral injury and 53.57% in central injury respectively. Inpostoperative evaluation of ILRFA-assisted liver resection, animals underwent an uneventful recovery, no complications occurred.Histological examination revealed a typical post RFA evolution. In ILRFA-assisted partial nephrectomy, the mean intraoperative blood loss35 ± 7 ml in the ILRFA and 152 ± 94 ml in the control, a 77.0% reduction (P = 0.024). The mean blood loss per centimetre resection area was 2.09 ± 1.41 ml/cm2 in the ILRFA compared with 12.79 ± 1.68 ml/cm2 in controls, the reduction was 79.0% (P = 0.019). In ILRFAassisted laparoscopic partial nephrectomy, the mean intraoperative blood loss was 32 ± 15 ml in the ILRFA and 187 ± 69 ml in the control group, a 77.0% reduction (P = 0.043). The mean blood loss per centimetre resection area was 2.27 ± 0.95 ml/cm2 in the ILRFA compared with26.46 ± 8.81 ml/cm2 in controls, the reduction was 79.0% (P = 0.047). In the renal trauma experiment, ILRFA also achieved promising results inhaemostasis. We believe that ILRFA is a useful device which may help in th

Radiofrequency ablation (RFA) is an established treatment option for patients with inoperable liver tumours and is now being investigated for the treatment of lung and other solid tumours. The aim of this thesis was to investigate the use RFA to decrease blood loss during liver resection, for the treatment of the liver resection edge and to investigate the safety and efficacy of brain RFA. Blood loss is an important factor affecting both the morbidity and mortality following liver resection. The use of a novel in line RF probe to ablate the transection plane prior to liver resection resulted in decreased blood loss with easier resection. This has potential in the treatment of liver tumors in cirrhotic livers and also in other vascular organs. The other important prognostic factor affecting long-term survival in patients undergoing liver resection for liver tumors is the surgical margins. Positive margins which cannot be treated with repeat resection may be treated with cryotherapy. The use of a novel probe to ablate the resection edge with RFA was found to be equally effective as cryotherapy and superior to argon beam coagulation or diathermy in an ex-vivo model. The radiofrequency ablation of the brain was found to be safe with no hemorrhage or damage to the surrounding brain parenchyma. There was no rise in intra-cranial pressure in the animals treated with RFA. The brain RFA was found to be effective and has potential for the treatment of brain tumours. Dispersive pad site burns was a significant problem in patients treated with radiofrequency ablation for lung and liver tumours occurring in 5% of patients. Pad tissue temperature of 45oC was found to be the threshold temperature above which burns occurred. Monitoring of pad-tissue temperatures with thermocouples and application of ice packs in addition to increasing the number of pads may help decrease this complication.

"March 2, 1949.", Signal Corps Contract no. W36-039-sc-32037. Project no. 102B Dept. of the Army Project no. 3-99-10-022, F. Bitter.

We describe new Chandra spectroscopy data of the cluster which harbors the prototypical head tail radio galaxy 3C 129 and the weaker radio galaxy 3C 129.1. We combined the Chandra data with Very Large Array (VLA) radio data taken at 0.33.5 and 8 GHz (archival data) and 1.4 GHz (new data). We also obtained new H I observations at the Dominion Radio Astrophysical Observatory (DRAO) to measure the neutral hydrogen column density in the direction of the cluster with arcmin angular resolution. The Chandra observation reveals extended X-ray emission from the radio galaxy 3C 129.1 with a total luminosity of 1.5 10(exp 41) erg s(-1). The X-ray excess is resolved into an extended central source of approximately 2 arcsec (1 kpc) diameter and several point sources with individual luminosities up to 2.1 10(exp 40) erg s(- 1). There is no evidence for a correlation between the 3C 129.1 X-ray and radio morphology. In the case of the radio galaxy 3C 129, the Chandra observation shows, in addition to core and jet X-ray emission reported in an earlier paper, some evidence for extended, diffuse X-ray emission from a region east of the radio core. The 12 36 arcsec squared (6 kpc 17 kpc) region lies in front of the radio core, in the same direction into which the radio galaxy is moving.We use the radio and X-ray data to study in detail the pressure balance between the non-thermal radio plasma and the thermal intracluster medium (ICM) along the tail of 3C 129 which extends over 15 arcmin (427 kpc). Depending on the assumed lower energy cut-off of the electron energy spectrum, the minimum pressure of the radio plasma lies a factor of between 10 and 40 below the ICM pressure for a large part of the tail. We discuss several possibilities to explain the apparent pressure mismatch., Pub. in Monthly Notices of the Royal Astronomical Society (MNRAS), v345 p1255-1265, 2003. Sponsored in part by NASA grants GO1-2135B and GO1-2135A and NASA contract AS8-39073.

We present optical and near-infrared ground-based imaging results on four low-redshift damped Ly-alpha (DLA) galaxies. The corresponding DLA systems were discovered in our Hubble Space Telescope spectroscopic surveys for DLA lines in known strong Mg ii absorption-line systems toward the quasars B2 0827+243, PKS 0952+179, PKS 1127 145, and PKS 1629+120. Two of the four DLA galaxies have confirmed slit redshifts, one has a photometric redshift consistent with the absorption-line redshift, and the fourth identification is based on the galaxy's proximity to the quasar sight line. The DLA galaxies span a mixture of morphological types from patchy, irregular, and low surface brightness to spiral galaxies. We also discovered several extremely red objects (EROs) in two of these fields and discuss the possibility that they are associated with the DLA galaxies. These observations add to the small but growing list of DLA galaxies at low redshift. At the present time, 14 DLA galaxies in the redshift range 0.05 smalller or approx. Z smaller or approx. 1 have been studied. The distributions of DLA galaxy properties for these 14 cases are discussed, and some important trends emerge. Low-luminosity dwarf galaxies with small impact parameters dominate this small sample. Also, four of the five highest column density systems, which dominate in the determination of the cosmological neutral gas mass density, arise in low surface brightness dwarf galaxies. Zwaan et al. have shown that only 15% of the neutral gas at the present epoch is contained in low surface brightness galaxies. Thus, if the low-redshift DLA galaxy trends hold up with larger samples, it would indicate that a different population of objects is responsible for the bulk of the neutral hydrogen gas in the universe at Z approx. 0.5., Prepared in collaboration with the Naval Research Laboratory, Washington,DC; the Department of Astronomy, Ohio State University, Columbus,OH; and the Institut d' Astrophysique de Paris, Paris, France. Published in The Astrophysical Journal, v595, p94-108, Sep 2003.

This report discusses our analysis of whether (1) the capabilities of the Cooperative Engagement Capability (CEC) program could be adversely affected by this transfer, (2) other systems could also be adversely affected by this transfer, and (3) DoD, FCC, and the Department of Commerce are taking appropriate and adequate steps to prevent or minimize such impairment. We also discuss potential actions that could more effectively achieve the intent of the Omnibus Budget Reconciliation Act of 1993 to minimize negative impacts of frequency reallocation on the federal government. This review was performed under our basic legislative responsibility and contains recommendations to the National Security Council, the Department of Commerce, FCC, and the Department of Defense. The report also includes a matter for congressional consideration.

The US military requires a high capacity, high availability broadcast capability to provide timely dissemination of standard products to users who cannot rely on terrestrial links. The Global Broadcast Service (GBS) is being developed to meet this requirement. The key limiting factor in GBS availability is environmental losses, specifically atmospheric absorption and rainfall loss. The optimum frequency band for GBS would have been between 1-10 GHz. At this frequency range, environmental losses are negligible. However, congestion in this frequency range has forced DoD to choose a much higher frequency band for GBS, 20/30 GHz (K/Ka band). At this frequency band environmental losses, specifically rain loss, will be a key limiting factor to GBS availability. This thesis analyzes GBS Phase 2 performance taking into account atmospheric limitations. A key problem in determining the performance of GBS lies in the accuracy of existing rain loss models. Several rain loss prediction models were considered, and based on studies conducted by the ITU-R and Stanford Telecom, the USA rain model was chosen for this analysis. This thesis has shown that, due to environmental losses, high availability can best be achieved if GBS is capable of lowering its data rate during periods of precipitation.

An instrumentation grant for the purchase of an tunable diode laser-amplifier, a rf synthesizer, and a rf spectrum analyzer is used to significantly enhance current research and support new investigations in optical parametric oscillators and wide-span optical frequency comb generation. Areas of research that benefit from the new capabilities include precision frequency metrology, optical communications, and multi-wavelength information processing. The fabricated diode laser at 790 nm has been utilized to generate tunable 1.6 um light using difference-frequency mixing in a quasi-phase matched periodically-poled lithium niobate substrate. It will also be used to pump an optical parametric oscillator for the generation of tunable 1.5-1.6 um radiation in the mW power range. The spectrum analyzer and synthesizer are to be used for evaluating the beat-note and phase noise characteristics of optical parametric oscillators and optical frequency comb generators.

A new measure of event-related brain dynamics, the event-related spectral perturbation (ERSP), is introduced to study event-related dynamics of the EEG spectrum induced by, but not phase-locked to, the onset of the auditory stimuli. The ERSP reveals aspects of event-related brain dynamics not contained in the ERP average of the same response epochs. Twenty-eight subjects participated in daily auditory evoked response experiments during a 4 day study of the effects of 24 h free-field exposure to intermittent trains of 89 dB low frequency tones. During evoked response testing, the same tones were presented through headphones in random order at 5 sec intervals. No significant changes in behavioral thresholds occurred during or after free-field exposure. ERSPs induced by target pips presented in some inter-tone intervals were larger than, but shared common features with, ERSPs induced by the tones, most prominently a ridge of augmented EEG amplitude from 11 to 18 Hz, peaking 1-1.5 sec after stimulus onset. Following 3-11 h of free-field exposure, this feature was significantly smaller in tone-induced ERSPS; target-induced ERSPs were not similarly affected. These results, therefore, document systematic effects of exposure to intermittent tones on EEG brain dynamics even in the absence of changes in auditory thresholds. EEG Spectrum, Auditory evoked response, Temporary threshold shift, Pub. in EEG and Clinical Neurophysiology, v86 p283-293 1993.

We present 330 MHz images and integrated flux densities for 20 previously identified 1st quadrant Galactic Supernova Remnants (SNRs). The observations were made in the D configuration of the VLA giving an angular resolution of -3' and providing good sensitivity to extended structure. Such emission, particularly if it is nonthermal, might be missed on higher frequency surveys due to confusion with the Galactic background and confusion with thermal sources in complex regions. Both problems are reduced by interferometric observations at this lower frequency. The flux densities presented can be used to anchor the low frequency end of the radio spectra of these sources, which are often poorly determined by previous observations at both high and low frequencies. The measurements presented here are also useful for distinguishing steeper spectrum shell-type emission from flatter spectrum plerionic emission for SNRs whose intrinsic morphological type is not well established., Published in The Astronomical Journal v103, n3, Mar 1992.

The Patent concerns the field of radioengineering and is designed for the analysis of radio signal spectra. An opticoacoustic correlation spectral analyzer is known, containing a mixer, a band filter, a radio pulse generator and an indicator. The aim of the invention is to increase the product of the analysis band with times the analysis time and to speed up the analysis process. This is achieved by the fact that an opticoacoustic correlator with two ultrasonic light modulators is introduced into the analyzer, in which ultrasonic waves propagate in opposite directions. One of the modulators is connected to the output of the band filter, the other to the output of the radio pulse generator. (Translations, USSR, Russian Language)., Edited trans. of Patent (USSR) 337 730 p1-2, 5 May 72.

The potential of the radiofrequency resonance absorption spectroscopy (RRAS) techniques for detecting specified quantities of specific explosives in checked airline luggage was investigated. The RRAS techniques considered in this study included nuclear magnetic resonance (NMR), electron spin resonance (ESR) and nuclear quadrupole resonance (NQR). It was found that all the explosives, except black powder, could be detected by NMR and that the NMR response from explosives could be separated from the response produced by other materials likely to be found in luggage. It was also found that black powder and smokeless powders could be detected by ESR but none of the other explosives produced an ESR response. NQR was found useful only for the detection of the RDX base explosive C-4 but even this material could be more sensitively detected by NMR. The results were sufficient to demonstrate the basic feasibility of using NMR for detection of responses from materials in the large volumes required to inspect checked baggage, but limitations on the available laboratory equipment prevented positive detection of explosives or explosives simulants in this space.

This Directive reissues reference (a) to: a. Provide DoD policy. b. Assign responsibility. c. Specify procedures for DoD management and use of the radio frequency spectrum.

We have reexamined the relationship between U-shaped peak-flux-density microwave spectra and solar proton events for approx 200 large (Sp( or = 2GHz) or = 800 solar flux uits (sfu) microwave burst (1965 - 1979). The radio spectra fell into two basic classes: (a) U-shaped with two maxima ( or = 800 sfu) in the range from 200 MHz to or = 10 GHz (59 percent of all events), and (b) cutoff spectra with a maximum or = 800 sfu at f or = 2 GHz and Sp (200 MHz) 100 sfu (18 percent). Nine percent of the events had intermediate spectra with a maximum or = 800 sfu at f or = 2 GHz and 100 sfu or = Sp (200 MHz) 800 sfu. We were unable to classify 15 percent of the events because of incomplete data. The associations of the three classes of spectra with Type II (and/or Type IV) meter wavelenght bursts and 10 MeV proton events of any size ( or = 0.01 pr per sq cm per sec per sr) are as follows: U-shaped Type II/IV (90 percent of large microwave bursts with U-shaped spectra are associated with Type II/IV events), protons (77 percent); intermediate Type II/IV (78 percent), protons (73 percent); and cutoff Type II/IV (22 percent), protons (33 percent). These statistics affirm various lines of evidence linking coronal shock waves and interplanetary proton events. They also suggest that the meter wavelength branch of the U-shaped spectrum may be attributable to second phase (vs flash phase) accelerated electrons., See also Rept. no. AFGL-TR-85-0176, AD-A158 566.

The phenomenon of photochemical hole burning makes it possible to utilize optical frequency as an additional dimension for the organization of an optical data store. Storage densities of 10 to the 11th power bits/cm squared may ultimately be achieved. The basic principles of photochemical hole burning are reviewed in this paper and recent research results are presented. (Author)

A system built largely from readily available amateur radio gear which uses radio frequency and audio modulation of pump and probe light beams allows the detection of very weak signals (rms noise approx. 3 times 10 to the -11th power W for a 10-second time constant) even in the presence of a much larger (0.036 W) background of pump and probe light.

Various studies undertaken for relating the proton event time characteristics to radio burst data are described. Eastern hemispheric events generally have a much larger onset time compared to the Western events. For western hemispheric events, the rise time of the radio burst is found to be well correlated with the delay before onset and the time to reach the peak flux level of the protons. Directions for improvements and extensions are also discussed. (Author)

This report presents the description, analysis and results of a set of measurements made to obtain statistics about the distortion of the frequency spectrum amplitude across the IF band of a 3-level-partial-response, digital line-of-sight, microwave radio system. The length of path was about 90 km. Results show that for line-of-sight systems: (1) Large values of distortion (1 dB/MHz) were observed during multipath fading events; (2) Diversity reception looks very promising as an effective tool in counteracting these distortion effects; (3) Multipath received-signal-level statistics can be used to predict the frequency and severity of this type of distortion on a line-of-sight-path; and (4) The 3-level-partial-response modulation system used here was very robust in terms of its susceptibility to the severity of amplitude distortion observed on this path during the measurements. (Author)

The interatomic forces in a crystal are usually strongly dependent on the interatomic spacing and consequently the lattice potential energy for a crystal can generally be written as a power series in the displacements of the atoms from their equilibrium positions. If such an expansion is terminated at the quadratic terms, then this constitutes the so-called harmonic approximation. In the harmonic approximation the lattice vibrations are true normal modes such that if energy is channeled uniquely into any one lattice mode, then it will remain undissipated in that mode. The harmonic approximation would therefore predict, for instance, that the scattering cross section for neutrons by a Bravais lattice would consist of a set of 8 function peaks or, analogously, that the spectral profiles of lattice vibrations would be a set of undamped temperature independent resonances. These and other such predictions are, of course, in marked discord with experimental results. It is therefore clear that the anharmonic terms in a lattice potential must be considered if a full understanding of many of the physical properties of solids is to be achieved. (Author)

This report covers in detail the solid state research work of the Solid State Division at Lincoln Laboratory for the period 1 August through 31 October 1978. The topics covered are Solid State Device Research, Quantum Electronics, Materials Research, Microelectronics, and Surface-Wave Technology. (Author)

Application of advanced radar clutter rejection techniques to FAA airport surveillance and enroute radars is constrained by inherent instabilities and spectral properties of the device used in the radar transmitter to generate high level RF pulse energy, and the degree to which its spectrum can be influenced by the circuit in which it operates. Coaxial magnetrons are believed to be spectrally pure, controllable and stable, and to embody other characteristics such as long life, which make them attractive replacements for the magnetrons presently employed. This report summarizes the results of extensive measurements made on a conventional S-band magnetron (presently employed in the ASR-7 radar) and a coaxial magnetron of equivalent pulse and power rating to compare their instabilities and spectral properties. (Author)

The broadening of second derivative Gaussian and Lorentzian absorption lines has been calculated as a function of modulation amplitude. It is shown that Lorentzian lines are more sensitive to modulation-induced distortion than Gaussian lines. For modulation levels less than 0.2 (half-width at half-height), broadening is less than 1% for Gaussian lines and 2% for Lorentzian lines. (Author), in French.

The radiative lifetimes of some doublet P(3/2) states of metal atomic ions have been measured in a flowing helium afterglow by using the method of zero field level crossing (Hanle effect). The use of the flowing helium afterglow provides an efficient means for producing the ions to be studied (by Penning Ionization) in an environment where system parameters can be easily modified. The optical emission spectra of I2 obtained in the flowing afterglow has been observed. A pulsed xenon ion laser and its application as a pump source for a tunable dye laser is described. The lifetimes of the rotational levels of the v'=0,1, and 2 levels of the A doublet Delta state of CH have been measured. The rotational lifetimes of the v'=0 level of the B doublet Sigma(-) state of CH have also been examined.

The development of a feasibility model for an integrated optic real-time rf spectrum analyzer is reported. The integrated optic spectrum analyzer consists of an injection laser diode, a thin-film optical waveguide incorporated onto a substrate with geodesic lenses, a surface acoustic wave (SAW) transducer, and a linear detector array. Functionally, rf spectrum analysis is effected as follows. An incoming radar signal is down shifted to the appropriate bandwidth, amplified, and used to drive the SAW transducers. The resultant SAWs interact through the acoustooptic effect with a collimated optical beam resulting in Bragg-diffracted beams whose intensities are proportional to the power level and whose directions are uniquely related to the frequency composition of the rf signal. The diffracted beams are focused onto unique positions at the focal plane detector array resulting in the spectrum analysis. (Author)

Calculations are described which yield absorption line parameters for the three isotopes of molecular oxygen: (16)O2, (16)O(18)O, and (18)O2, in the format of the AFCRL Atmospheric Absorption Line Parameters Compilation. The line parameters are: transition frequency, integrated line strength at 296K, line width, lower-state energy, and identifying quantum numbers. These parameters are required as input to the SLAM program (described elsewhere) which calculates the attenuation vs. altitude at any fixed frequency in the millimeter-to- submillimeter wave region.

High-sensitivity observations at the carbon 140 alpha and 141 alpha recombination line frequencies in the direction of the Rho Ophiuchi dust cloud show the presence of recombination lines of carbon and sulfur, but not of other heavy elements. These results require: that the elements Si, Fe and Mg are depleted by factors greater than 15, 10 and 2 respectively, most likely into interstellar grains, whereas sulphur is undepleted: and that only approximately 1/6 of the carbon is present in the gas phase in the cloud. From the observed size of the CII region, theta is approximately equal to 3.2 arcmin, together with the observed carbon depletion, the authors infer that the density in the carbon-line-emitting region is n(H) approximately equal to 25000/cc, and that the size of the SII region is significantly larger than that of CII region. The agreement between the widths of the recombination lines (which arise in a small region of the cloud) and those of the more widely distributed molecular species suggests that the lines in this cloud are broadened by microturbulence on a scale much 0.1 parsecs.

A particular observation scheme based on the twofrequency correlation function approach for the measurement of time-varying spread channels having timestationary Gaussian statistical properties is analyzed. It is shown that the scheme works well for underspread as well as overspread channels. The method also appears to be useful in cases where there is correlation between the signals arriving with different delays. Expressions are derived for the variances of the determined correlation and target-scattering functions derived by double Fourier transformation of the observed correlation function.

Videofrequency spectra data, from the modulating source as well as the incorporated amplifier, of an electronic countermeasures equipment are often required in determining the equipments' effectiveness. Previous facilities utilized for video analysts were characterized by slow operational point-to-point sampling procedures, and by uncertainty of resolution figure due to possible Q variation of each of the multiple-tune circuits used in the analyzer. After a brief discussion on the merits and limitations of tuned circuit type analyzers as contrasted with superheterodyne types,a quasi-instantaneous video analyzer which was developed principally for the rapid analysis of modulation spectra is described. The instrument presents the frequency analysis of a complex voltage visually, with an alternative provision for instrumental analysis by manual control. it is essentially a double conversion superheterodyne receiver without preselection. A magnetically controlled local oscillator is used as a sweep for visually displaying the complete spectrum from 50 kc to 10 Mc, on a cathode ray tube. in addition, a manually tuned local oscillator is used in conjuction with a thermistor bridge indicator for a point-by-Point analysis. The superhoterodyne principle permits a suitable, constant, and controlled resolution value to be used, and allows a visual analysis to be made in 1/30 second by sweeping the local-oscillator frequency over the desired frequency band at a 30-cps repetition rate. A relation exists between the three factors - the video frequency band to be analyzed, the time required to give a complete analysis, and the final resolution bandwidth of the analyzer. For a video frequency band of 50 kc to 10 Mc, and an analysis time of 1/30 second, the minimum permissible resolution bandwidth is 17.5 kc.. The resolution may be increased by using a smaller video band to be analyzed, or by increasing the time permitted for a complete analysis.

The report describes the theoretical study and experimental circuit investigations conducted on the Allison effect apparatus used for chemical analysis. The inherent electrical behavior of an Allison effect apparatus was well defined by using modern high speed oscillographic techniques and frequency selective equipment. A continuous radio frequency spectrum characterized by numerous resonances rapidly diminishes into the noise level at 4000 megahertz. A theoretical analysis of the apparatus generated a valid equivalent circuit model. A review of the extensive data indicates that the Allison effect apparatus functions primarily as a phase comparator for radio frequencies in the 30 to 100 megahertz range. An rf-optical interaction in the cells, possibly by means of the Cotton-Mouton effect, is thought to produce a characteristic light modulation effect when phase matching occurs.

This research memorandum describes a data processing technique for analyzing the Doppler-shift properties of a radio channel. A computer program has been developed that computes the power spectrum of power scattered by the radio channel as a function of Doppler shift. This program was developed in conjunction with phase-stable CW experiments which were performed on two HF paths. The program computes the power spectrum of the time variations of the response of the radio channel to a CW tone relative to the transmitted frequency.

An analyzer is being developed which will be continuous over the 150-kc to 1-kmc range and will be used in the measurement of the absolute spectral intensity of very short, separated, repetitious pulses. Research indicated that a possible solution to the problem is the use of a series of cascaded and synchronously tuned RLC shunt circuits (designated as a CASTA) with vacuum-tube isolation between stages. An approximate expression for the impulse response of n-cascaded shunt-tuned circuits is given. A search for some relationship between this expression and an easily measurable characteristic was made. The results showed that when the envelope function itself was considered to be a driving pulse for a succeeding cascaded parallel-tuned RLC circuit, a simple relationship existed between the initiating impulse and the response of this second cascaded set of tuned circuits. An analysis of the response of a CASTA for both single and repeated impulses is appended. An area method for measuring the absolute spectral intensity is also described in an appendix.

A general theory to explain the propagation characteristics of very low frequency (VLF) waves which travel between the earth and the ionosphere is presented. From this theory, two methods for range determination are suggested by analyzing the received energy spectrum. The magnitude and the cause of the errors which can be expected in both range and azimuth measurements are predicted.

An experimental investigation of lunar echoes at 915 mc has been conducted. The transmission loss between isotropic radiators over the earth-moon-earth path was established as being 280 dbAT 915 MC. This result, in conjunction with transmission losses reported by other investigators in the frequency range from 200 mc to 3000 mc, leads to the conclusion that the radar cross section of the moon is frequency dependent and decreases with increasing frequency at a rate of about 6 db per octave. At 915 mc, the lunar radar cross section was equal to 4.2 x 10 to the 10th power square meters. After detection, the lunar echo at 915 mc exhibits Rayleigh-like fading with an average 10- to 90-percent fading range of about 14 db. There is evidence that the lunar echo is not entirely randomly phased but contains a steady-signal component which is in the ratio of 1.5 to 1 with the rms scattered-signal components, i.e. 47 percent scattered power and 53 percent specular reflected power.

A discussion is presented of several of the items of equipment necessary in a radio frequency compatibility accessory equipment set. Major items discussed are the frequency measurement system and a standard response indicator for both CW and pulse systems. The specifications for other accessory items such as directional couplers, isolators, attenuators, dummy loads, and filters are also reviewed. Experimental work on the deposition of thin film alloys to obtain a film with a temperature coefficient of resistance which exhibits a minimum change of resistance over the temperature range of interest was conducted. Results of this work are shown. A receiver input coupler which provides for coupling from 50 to 300 ohm transmission systems was designed and its characteristics are shown. The problems associated with the audio susceptibility tester are discussed. Results of the evaluation of a rejection filter operating in the frequency range 100 to 400 Mc are presented.

Refinements in methods of generation and detection of microwave harmonics at wavelengths down to the 1 - 2 mm region are discussed. Preferred methods are given for selection, shaping, mounting and adjustment of the point- contact diodes used. Other refinements of instrumentation have allowed the measurement of spectra of unstable and involatile molecules with the ability to resolve important hyperfine structures. New microwave spectroscopic measurements included evaluation of precise interatomic distances in fluorine cyanide and chloroacetylene, of electrondistribution properties of cyanamide and diazomethane from nuclear quadrupole effects, and the first precise structural information regarding nitramide in the gas phase. Refined values of centrifugal distortion constants were obtained for several molecules.

The design and development is described of a Broadband Spectrum Analyzer, Converter-Measuring, Frequency 'S', and Converter-Measuring, Frequency 'L'. Additional work is being accomplished on Converter-Measuring, Frequency 'X'.

Atmospherics formed from lightning discharges are a convenient object for investigating long and super-long electromagnetic waves. In previous works it was shown that the phase velocity of the electromagnetic waves comprising atmospherics and the effective conductivity of the lower ionosphere can be determined by analyzing the phase (and to some extent the amplitude) characteristics of single atmospherics. A reasonably correct solution of the opposite problem was also of great interest, viz., to calculate theoretically, on the basis of a specific model of the ionosphere evolving from experimental data and on the basis of experiments on the spectral properties of the source, the forms of atmospherics expected at various distances. Comparison of the signals thus calculated with the atmospherics observed experimentally would make it possible to verify the correctness of the general theoretical assumptions used for this and to explain whether the effective parameters obtained theoretically for the selected ionosphere model were observed during the experiment.

IT WAS DESIRED TO OBTAIN THE SPECTRUM OF A BIPHASE SUBCARRIER, THAT SWITCHES PHASE EVERY BIT PERIOD, PHASE-MODULATING A CARRIER. Much information on system requirements can be obtained from this spectrum. The condition described above implies the worst case with regard to bandwidth. As will be seen, the minimum IF bandwidth is twice the sum of the subcarrier frequency and one-half the switching frequency. It will also be seen that components beyond the third harmonic are appreciably small and may be neglected. The means of mechanizing the above system, important waveforms, the power spectrum of the bi- phase subcarrier, and the relative magnitudes of the phase modulator output are shown. The derivation of the latter is given.

The results of a program of research in the rf spectroscopy of stored atomic and molecular ions are described. Work has been done on the study of magnetic resonance and hfs of e(-), He(+), 3He(+), and H2(+). Techniques for measuring the temperature of ion gases and their radiative cooling have been developed. Extension of the techniques developed under the grants resulted in the highest resolution for any atomic line (199Hg(+) hfs) ever achieved.

An extension is made of previous analysis of infrared emission of diatomic gases to the case of a Doppler-broadened line shape, which is of particular importance at low pressures and long path lengths.

Approaches which will permit monitoring the RF Spectra emitted by pulse radar transmitters from 200 MC to 40 GC were investigated. Techniques for monitoring levels of peak effective radiated power down to the permissible levels of MIL-R- 27055 have been sought. Th-nitor approach which is described employs multiband swept tuned receivers, each covering approximately octave bandwidths simultaneously. Identification of the source of received spurious signals is provided by correlation with trigger pulses derived from the radars via coaxial cable. A breadboard monitor has been constructed in order to permit demonstration of the approach. The breadboard, operating in the range from 2 to 4 GC, will be tested at the Verona Test Site.

The objective of the study program is to pursue a continued research and development effort with the goal of increasing the capability of automated interference measurements in the frequency range of 100 kc to 40 gc. Investigation is being directed toward the design, on paper, of a single receiver having the combined capabilities of a spectrum signature, field surveillance, field intensity and other types of broadband receivers. During the course of this study pro gram, major emphasis will be placed on investigation of techniques in two specific areas: (1) voltage-tunable, solid-state receivers; and (2) automated techniques for the presentation. Where necessary, various techniques will be breadboarded for comparison or feasibility purposes. The program output will be a final report describing the relative merits of the techniques investigated. The design of a receiver utilizing the techniques which best fulfill the program goals will also be presented on paper. Field tests were run on the existing AN/GRR-9, a voltage-swept field surveillance receiver. The results of these field tests were applied as inputs to the present receiver study program.