Showing papers on "Frequency band published in 1980"

Detection and monitoring device

Abstract: One or more physiological rhythmic functions can be monitored by detecting pressure waves within a predetermined, relatively narrow, frequency band associated with each of said functions, generating a corresponding signal representative of said pressure waves associated with each of said functions and demodulating the signal to detect any amplitude modulation frequency related to the rhythmic rate of each of said functions.

Structural identification in the frequency domain from earthquake records

Abstract: A method has been developed to identify the parameters of the lower modes of a linear, time-invariant model of a structure from its recorded earthquake response. The identification is performed by selecting the parameters to obtain a least squares fit over a specified frequency band between the unsmoothed, complex-valued finite Fourier transform of the recorded acceleration response and the corresponding transform calculated from the response of the model. By including the effects of the initial and final conditions in the analysis, only a portion of the recorded excitation and response acceleration histories need be considered. The method is demonstrated first by an application to generated test data, and then to measured earthquake response.

Artificial illumination of ornamental water fountains with color blending in response to musical tone variations

Abstract: An ornamental water fountain is artificially illuminated by separate sets of differently colored lamps illuminated by a color blending system that responds to variations in musical tones. In one embodiment, there are three sets of lamps in separate principal colors, namely, red, blue and green, and the intensity of light from each set of lamps is independently controlled during the playing of a musical number, producing a multitude of different colors reflected by the fountain in response to variations in the amplitude and frequency of the musical tones. The color blending system operates in response to an input voltage representative of musical tones produced over a wide range of audio frequencies from a phonograph, tape player, radio receiver, or the like. The input voltage is separately coupled to low pass, band pass and high pass filters for producing separate frequency band signals representative of the content, i.e., combined amplitude and frequency, of the musical tones produced within low, intermediate and high frequency ranges, respectively. The three frequency band signals are fed to separate phase control circuits for independently adjusting power supplied to the different sets of lamps, thereby adjusting the intensity of the lamps in proportion to the content of sound produced within each frequency range.

Satellite arrangement providing effective use of the geostationary orbit

Abstract: A satellite squadron or cluster formation is disposed in a predetermined location in the geostationary orbit, including a plurality of controllably maneuverable communication satellites and a centrally located switching and control satellite The satellites comprise a simulated geostationary communications platform made up of discrete modules which are not physically attached together The satellites are grouped together in assigned positions in a relatively close formation, and are provided with cross-link intersatellite radio communications The switching and control satellite detects the relative position of the communication satellites and sends control signals to maintain them in their assigned positions in the formation Communication signals are relayed from one place on the earth to another via the satellite cluster formation by utilizing the control satellite as a switching satellite Each satellite has a communications down link providing communications with selected earth stations in a predetermined frequency band When a signal is received by one of the satellites, it converts the signal to the cross-link frequency band and transmits it to the control satellite, which retransmits the signal to a different satellite, where it is converted to that satellite's down link frequency band, and retransmitted to the earth In this manner, a signal originating in one continent, for example, may travel to the satellite cluster at one frequency band, and may be relayed to another continent at another frequency band Thus, all satellite earth stations at their various frequency bands are mutually compatible

Time-resolved infrared spectral photography

Abstract: TIME-RESOLVED INFRARED SPECTRAL PHOTOGRAPHY ABSTRACT An intense broadband continuum light pulse of uniform spectral intensity and short time duration is generated, then downconverted in frequency to a region of interest, preferably in the infrared region, by applying it as a pump pulse to a molecular or atomic vapor so as to induce stimu-lated Raman scattering. The resulting uniform spectral intensity distribution Raman Stokes pulse is then used to probe a sample. The sample converts the distribution of the probe pulse into a nonuniform spectral intensity distribu-tion which contains the absorption spectrum of the sample. This spectrum pulse has the same spectral bandwidth and time duration as the Raman Stokes pulse and is finally upconvert-ed in frequency to a region where the spectrum pulse can be conveniently recorded. This is done with a four-wave Raman mixing process in an alkali metal vapor. The vapor is simultaneously pumped with the spectrum pulse and with a second pumping light pulse (or beam) having a frequency in the vicinity of a suitable resonance line of the vapor so as to induce SERS. In the alkali metal vapor, the re-sulting Raman Stokes pulse and spectrum pulse beat to-gether with the second pumping light pulse to produce an upconverted pulse at a higher frequency band, which sur-prisingly also tends to have the same spectral bandwidth, intensity distribution (spectrum) and time duration as the spectrum pulse. The upconverted pulse is then recorded either photographically or photoelectrically with conven-tional spectrographic apparatus.

Time- and frequency-domain representation of multipath fading on line-of-sight microwave paths

Abstract: Propagation on a radio path experiencing multipath fading can be modeled in the time domain by an N-path transmission network with each path characterized by gain and delay. We examine the inter∗∗∗relations of such a representation with the more frequently observed frequency domain characteristics of the channel. We show that the decibel gain and envelope delay distortion of the transfer function may both be expressed as summations of elementary functions each associated with a zero in the complex frequency domain. We find that the average frequency spacing of the zeros, and of transmission minima, is determined by the maximum delay. Although published propagation data indicate an average spacing of 100 MHz or more for common carrier radio hops, we verify that closely spaced zeros can occur with nominal path gains and short delay spreads. This is demonstrated by developing multipath synthesis procedures which allow path gains and delays to be determined from a specification of gain and/or delay distortion in a finite frequency band. The resulting networks are not unique; for instance, more than 5000 three-path delay networks with delay spread less than 10 ns can be found to provide a match over a 60-MHz band near 6 GHz to a sample gain shape with two minima. These developments provide the basis for a qualitative comparison of the ability of a channel modeling function to statistically represent the state of the transmission channel. We describe the limitations of both delay and complex power series models of varying degrees of complexity.

Comparisons between wave directional spectra from SAR and pressure sensor arrays

Abstract: Simultaneous directional wave measurements were made at Torrey Pines Beach, California, by a synthetic aperture radar (SAR) and a linear array of pressure sensors. The measurements were conducted during the West Coast Experiment in March 1977. Quantitative comparisons of the normalized directional spectra from the two systems were made for wave periods of 6.9-17.0 s. The comparison results were variable but generally showed good agreement of the primary mode of the normalized directional energy. An attempt was made to quantify the physical criteria for good wave imaging in the SAR. A frequency band analysis of wave parameters such as band energy, slope, and orbital velocity did not show good correlation with the directional comparisons. It is noted that absolute values of the wave height spectrum cannot be derived from the SAR images yet and, consequently, no comparisons of absolute energy levels with corresponding array measurements were intended.

Hearing aid suitable for use under noisy circumstance

Abstract: A hearing aid in which input signals picked up through a microphone are divided to those of two or more frequency bands by means of a frequency division means, signal outputs of frequency band(s) in which noise signals are included are saturated or reduced by a compensating means such as compression or saturation amplifier, and mixed with signals of other signal of frequency band(s) which are not compensated, whereby ambient noises can be removed from voice sounds.

Spectrum analyzer with frequency band selection

Abstract: A spectrum analyzer for FFT analyzing and displaying the frequency spectrum of a digital signal over a given frequency band (background), as well as over a more limited frequency band (foreground). The spectrum of the signal over each frequency band is calculated and displayed so as to appear on a screen as a simultaneous display. The position of the limited frequency band as well as the width thereof, may be varied.

Computation of the frequency response of a class of symmetric N-way power dividers

Abstract: Symmetric n-way power dividers (and combiners) are needed to feed multi-element antennas and to combine the output powers of a number of solid-state amplifiers and oscillators over a broad frequency range. We present a unified method of analysis for computing the frequency responses of symmetric, n-way power dividers of the Wilkinson, radial, and fork types, whose transmission lines are allowed to be coupled and nonuniform and may be surrounded by an inhomogeneous dielectric medium. The method is based on the analysis of a simple one- or two-port network for each of the n eigenmodes of the power-divider structure, resulting in a considerable improvement in the speed of computation, as well as a sizable reduction in storage requirements, as compared to a standard method of nodal analysis. Furthermore, the aforementioned one- and two-port networks facilitate the design and optimization of the power dividers over a desired frequency band.

A Novel Polarization-Independent Beam Splitter

Abstract: This paper presents the design and experimental results of a novel broad-band quasi-optical polarization-independent beam splitter. The novel beam splitter consists of parallel metallic strips formed on a dielectric sheet. The width and spacing of the metallic strips and thickness of the dielectric sheet are optimized. This experimentally manufactured 3-dB beam splitter has a frequency bandwidth from 80 to 110 GHz, and the transmission and reflection coefficients for mutually orthogonal polarisation are within 3/spl plusmn/0.5 dB over this entire frequency band. The insertion losses are 0.2 dB over the abovementioned frequency band. The obtained insertion losses are less than that obtained with any other quasi-optical polarisation-independent beam splitter presented in the literature to date. This type of beam splitter holds great promise as a device for constructing signal-multiplexing and demultiplexing circuits in the millimeter-wave region and above.

A Quadriphase Fin-Line Modulator

Abstract: A hybrid-coupled quadriphase rnodulator which has been realized in fin-line technique is described It operates over a 15-percent frequency band around 15 GHz with an insertion loss of 17 dB The circuit has been scaled to twice the operating frequency The insertion loss then amounts to 22 dB Furthermore, it is shown experimentally that the performance of the modulator does not degrade if the dimensions of the waveguide housing are altered to amounts of up to 10 percent

Frequency modulated signal demodulation process and demodulator putting this process into operation

Abstract: 1. Method of demodulating a signal which is frequency modulated about a frequency F and has a passband which is small in comparison to F, characterized in that the signal is sampled at a rhythm which is equal to 4F', F' being an arbitrary frequency of the frequency band of the signal ; in that one calculates the ratio N/D of a first linear combination N=x(t1 - 3/4F')-x(t1 ) - x(t1 - 2/4F') + x(t1 - 1/4F') and a second linear combination D=2.x(t1 - 2/4F'), - 2.x(t1 - 1/4F') of four successive samples : x(t1 ), x(t1 - 1/4F'), x(t1 - 2/4F'), x(t1 - 3/4F'), of the signal to be demodulated ; and in that one calculates 2F'/pi arc sin (N/D) this value corresponding to the value of the frequency variation delta F of the modulated signal.

Internal wave kinematics in the upper tropical atlantic

Abstract: Horizontal velocity and temperature measurements observed from a two-dimensional array of moored instruments, mooring Fl, are analysed to describe the near-surface internal wave field in the GATE (GARP Atlantic Tropical Experiment) C-scale area. Spectral properties indicate strong deviations from the Garrett and Munk (1972, 1975) deep ocean internal wave models. The frequency spectrum in the upper pycnocline is dominated by three energetic bands centered at 0.0127 (inertial frequency), 0.08 (M2-tidal frequency) and 3 cph. The latter frequency band does not correspond to the local Brunt Vaisala frequency (< 10 cph) and contains about one half of the total internal wave energy of fluctuations with periods less than 10 hours. Cross-spectral analysis of the high frequency internal waves yields corresponding wavelengths of order 1 km consistent with westward propagating first mode wave groups, if the effect of Doppler shift due to a strong mean current is taken into account

Speed control system for a multiple speed tape recording and reproducing apparatus

Abstract: A tape speed control system for a multiple speed tape recording and reproducing apparatus comprising a transducer head for reproducing a tape speed indicative signal which has been recorded along an edge of a recording tape. The frequency of the reproduced speed indicative signal is compared with a plurality of reference values to determine to which one of separate frequency bands the frequency of the reproduced speed signal belongs. If the latter belongs to the frequency band other than the frequency band which includes a predetermined frequency derived when the playback speed equals to the recording speed, a corresponding motor drive signal is generated to vary the speed of the tape until the frequency of the reproduced speed signal reaches the predetermined frequency.

Frequency converter capable of eliminating local power leak

Abstract: A frequency converter has first, second and third terminals which receive a first signal having a first frequency band, a local oscillation signal, and a second signal having a second frequency band. The first signal and the local oscillation signal are mixed to generate the second signal. A first branching circuit is connected between the second terminal and the frequency mixer, for branching part of the local oscillation signal. A first part of the branched local oscillation signal, which is supplied from the first branching circuit, and a first leaked local oscillation signal are applied from the frequency mixer to the first terminal. The phase and amplitude of the first branched local oscillation signal are adjusted so that the first branched local oscillation signal and the first leaked local oscillation signal have equal amplitude and are reversed in phase to cancel each other.

Mic connecting structure

Abstract: PURPOSE:To avoid a trouble that is caused by the heat expansion or the like, by connecting the high frequency signal of an MIC (IC element of high frequency band circuit) via a waveguide. CONSTITUTION:The prescribed high frequency signal is transmitted to the projected end part 51 from one MIC5, and thus the high frequency signal is changed to the waveguide mode from the strip line transmission mode at the part 51 to be radiated to the short-circuit line 7 as well as the through-hole 61 of the carrier 6. While the high frequency signal arrived at the projected end part 51' of the other MIC5' is changed to the strip line transmission mode from the waveguide mode to the strip line of the MIC5' and then transmitted to the MIC5.

Four band VHF varactor tuner

Abstract: A varactor controlled television receiver tuning system is operable for tuning all VHF and CATV television channels in four frequency bands including the low VHF band extending between 54-88 MHz, the mid/high VHF band extending between 120-216 MHz, the CATV superband extending between 216-300 MHz and a CATV hyperband extending between 300-400 MHz. The tuning system comprises a plurality of identically configured resonant circuits each responsive to a pair of band switching signals for assuming a total inductance for tuning each of the four different frequency bands, each of the resonant circuits being alignable by adjusting a different variable reactance element in each frequency band.

Electro-acoustical measuring device and method

Abstract: In an exemplary embodiment, for testing the chronological resolution of hearing, acoustic signals are supplied to the ear to be tested via an earpiece and consist of a test tone which can be interrupted and of a masking sound which can be modulated, their frequency and amplitude level being adjustable. Complicated measures are necessary for the measurement of the so-called listening threshold period pattern in order to present a complete pattern for identifying the chronological resolution of the hearing. In contrast, the disclosure provides an uncomplicated measuring device which is also easy to operate and with which the maximum and the minimum of the listening threshold period pattern or, respectively, their difference can be determined. To this end, the disclosure provides a device with channels generating respective sound signals, each of the channels having its own generator. Whereas the first generator is designed in the manner standard given electro-acoustical audiometers, that for the second channel has a noise generator whose output is modified by means of frequency band selection filters to provide a noise band with a mean frequency which can be matched to changes in the selected frequency of the first channel, and whose output amplitude level can be increased to a suitable value in comparison to the quiescent hearing threshold level (RHS) of the test tone. The disclosed device is particularly suitable for use in testing hearing.

Apparatus for regenerating signals within a frequency band

Abstract: Apparatus for generating signals to interfere with or jam signals detected as unfriendly in a given input frequency band comprises a spectrum analyzer circuit using surface acoustic wave (SAW) chirp filters to provide a transformation of input frequency signals to a series of time displaced signals in a linear frequency-to-time relationship. The analyzer circuit uses the SAW devices to perform multiply-convolve functions that separate the different frequency signals in time and the analyzer is repetitively triggered to perform a spectrum analysis. The time series signals are selectively applied to a frequency synthesizer having a time-to-frequency relationship that matches the analyzer characteristic so as to regenerate signals at the input frequencies. The synthesizer uses two matched chirp filters one activated by a fixed time signal and the other by the time series to generate swept frequencies that are mixed to provide the required frequency outputs. The time series is processed to inhibit those signals corresponding to frequencies identified as friendly. In an alternative synthesizer the time series signals are converted to frequency-representing digital codes which are applied to a programmable frequency generator. Signal processing to protect friendly frequencies is performed on the digital codes.

Synchronous demodulator for multi-phase PSK signal

Abstract: An N-phase PSK demodulator is disclosed wherein all circuits therein operate in a frequency band equal to or below the carrier band. The locally reproduced carrier is generated by a phase locked loop in combination with a frequency converter means and a divide-by-two frequency divider. The frequency converter means consists of n identical frequency converter circuits connected in series, where 2 n =N. For a 2-phase PSK demodulator where n=1, the 2-phase PSK modulated wave is applied as a first input and the reproduced carrier divided by two is applied as a second input to the frequency converter circuit. A mixer and filter provide as an output the difference frequency between the first and second inputs. The latter output is multiplied by two and applied as the input to the phase locked loop. Where n>1, the first input of each frequency converter circuit except the first is the output from the preceeding circuit, and the output from the last frequency converter circuit is the input to the phase locked loop.

Mos transistor circuit

Abstract: PURPOSE:To realize the increase of the amplification factor, expansion of the frequency band, reduction of the chip size, reduction of the input conversion noise and lowering of the power consumption respectively by using the MOS transistor (DSATr) formed through the double diffusion for the differential amplifier circuit. CONSTITUTION:With use of DSATr to transistor Tr 202 and 203 of the differential amplifier, the Tr size can be reduced even in case the channel length of DSATr is set under 6mum if the gate length is set to more than 6mum and thus with the gain of the low frequency of more than 10. As a result, an extremely high gain is secured with the same size. In addition, the frequency band can be expanded greatly since gm is extremely high, and at the same time the input conversion noise can be reduced greatly. And also the chip size can be reduced as long as the gain is not changed. The same effect can be obtained with use of depression-type MOSTr 501 and 502 without forming the DSATr into the complementary type.

Four band VHF varactor tuner to cover extended CATV band utilizing two switching diodes per resonant circuit

Abstract: A television receiver tuning system includes a bandswitchable impedance transformation circuit operable for improving the impedance match between a varactor tuned resonant circuit and the gate electrode of a field effect transistor (FET) at the low ends of a plurality of television signal frequency bands. The impedance transformation circuit comprises a capacitor connected in series between the varactor tuned circuit and the gate electrode of the FET and a bandswitchable inductive network connecting a different selected inductance in shunt with the gate electrode of the FET for each tuned frequency band, each value of selected inductance providing, in association with the series connected capacitor, a resonant point below the lowest frequency of the associated frequency band.

Measurement of Impulsive Noise on Electric Distribution Systems

Abstract: Impulsive noise measurements were made on two electric distribution systems as part of Electric Power Research Institute Project RP1024-1, Study of Distribution System Surge and Harmonic Characteristics. This paper describes the instrumentation system used to measure impulsive noise conducted along, and emanated from, distribution lines in the 3-300-kHz frequency band. A significant source of this noise was identified as synchronously switched power converters. The concern is that such noise on distribution systems might cause interference to digital data carrier systems proposed for distribution systems. Test data from one of the utility systems are presented; potential problems caused by interference are discussed. Additional work utilizing the same or similar instrumentation on a relatively broad spectrum of distribution systems is recommended to identify and characterize impulsive noise.

Physiological Radio Telemetry of Vertebrates

Abstract: Recent advances in the technology of multichannel radio telemetry have made possible the simultaneous measurement of several physiological parameters from free ranging or captive animals. Data obtained under natural conditions are essential to our understanding of the behavior, ecology and environmental physiology of any species. A subcarrier radio transmitter is described in detail. It operates on the 88–108 MHz broadcast band or in the 150 MHz VHF range. Subcarrier frequency is 1 KHz, facilitating the use of inexpensive portable receivers and cassette tape recorders. A magnetic switch and CMOS integrated circuitry are used to provide on/off switching of the surgically implanted radio transmitter. Problems requiring attention in the future include transmitter costs, improvement of ‘battery free’ transmitters, radio telemetry frequency band allocations and data analysis.

Simulation studies in both the frequency and time domains of InGaAsP-InP avalanche photodetectors

Abstract: The purpose of this brief is to analyze the relation between the physical structure of the quaternary InGaAsP avalanche photodetector and the speed of temporal response. The small-signal time-domain differential equations dealing with the current multiplication in a p-n junction structure operating in the avalanche mode are obtained. The structure is a mesa diode made of an n-type quaternary material In 1-x Ga x As y P 1-y grown on a heavily doped InP substrate. For the first time, both magnitude and phase of the frequency response are computed in a frequency band extending up to 256 GHz, from which the time-domain impulse responses are obtained. Simulation studies are performed using light pulses with an FDHM of 48.8 ps and a base duration of 97.7 ps. The FDHM of the detected waveform is less than 70 ps, and the leading edge duration is less than 100 ps.

Radio method and apparatus for gathering and processing information coming from a plurality of stations

Abstract: In a satellite which asynchronously receives radio frequency signals from alurality of beacons scattered at the surface of the earth, each signal received has a pure carrier wave portion followed by a phase modulated message carrying portion. The frequencies of the signals are not known within a predetermined frequency band. The satellite has a plurality of essentially identical processing units which each receive on their input all the signals present at any given instant in the input frequency band. Each processing unit has a phase locked loop which may be progressively tuned to the frequency of one of these input signals in response to a frequency estimate of this signal to which the operating frequency of the phase locked loop is preset. This frequency estimate is updated until the phase lock occurs on this input signal, ready for demodulation of the message part to begin. The estimate frequencies are derived from an input band frequency spectrum analyzer. A command unit selectively allocates each new frequency estimate to a respective processing unit as a result of a comparison therof with the previously allocated frequency estimates to accelerate the tuning of the processing units and prevent any duplication of the processing of a same input signal.

Method and apparatus for acoustically monitoring the flow of suspended solid particulate matter

Abstract: A method and apparatus for monitoring char flow in a coal gasifier system cludes flow monitor circuits which measure acoustic attenuation caused by the presence of char in a char line and provide a char flow/no flow indication and an indication of relative char density. The flow monitor circuits compute the ratio of signals in two frequency bands, a first frequency band representative of background noise, and a second higher frequency band in which background noise is attenuated by the presence of char. Since the second frequency band contains higher frequencies, the ratio can be used to provide a flow/no flow indication. The second band can also be selected so that attenuation is monotonically related to particle concentration, providing a quantitative measure of char concentration.

Device for inspecting an individual high frequency signal selected according to frequency from a broad frequency band

Abstract: A device for inspecting an individual high frequency signal selected according to frequency from a broad frequency band comprises a voltage controlled oscillator which can be controlled with respect to frequency by a periodic sweep voltage, in particular a linear sawtooth voltage, in such a manner that all signals occurring in the frequency band can be displayed as a spectrum in the picture screen of a cathode ray tube. The device further comprises a frequency marker generator which has a device for generating a frequency mark voltage and a voltage comparator for, given sweep operation and equality between an adjusted frequency marker voltage and a momentary sweep voltage, generating a frequency mark on the picture screen which is adjustable to identify a corresponding fixed frequency after termination of the sweep operation for inspecting an individual frequency-selected signal. The oscillator is a phase controlled oscillator of a synthesizer in whose control loop a transfer switch is provided and operates in such a manner that the sweep voltage switches off in a first position of the switch and the control loop is closed, and the momentary tuning voltage of the control loop is stored. Subsequently, the control loop is opened in a second switch position and the sweep voltage is connected to the control input of the oscillator. In this mode, the stored tuning voltage is compared to the sweep voltage in the voltage comparator of the frequency mark generator for generating the frequency mark. The transfer switch is held in the first switch condition for evaluating the individual signal.

The resolution limits of the imaging of conducting bodies using multistatic scattering

Abstract: The well-known inverse scattering problem is discussed for the multistatic case. With physical optics a reconstruction of the equivalent sources of the scattered field is proposed giving the location of the scatterer's surface as well as its inclination. The resulting multidimensional Fourier transform relationships can be discussed regarding resolution, which can be achieved provided the range of aspects and the available frequency band are limited. When the object domain is given the application of the sampling theorem ensures the minimum possible number of measurements without degradation of the results.