Showing papers on "Frequency band published in 1982"

Improved empirical model for the Jerusalem cross

Abstract: The frequency transmission characteristics of Jerusalem cross grids at oblique angles of incidence are investigated experimentally, and an improved equivalent circuit model for the cross is proposed. Particular attention is given to the properties of the upper resonant frequency band and its application to dichroic reflector antennas. This upper resonance is essentially dipole in nature, changing in frequency as the angle of incidence is varied. It occurs at a higher frequency than expected and is influenced not only by the length of the end caps but also by the mutual reactance between the end caps and the main arm of the cross. An equivalent circuit model for the cross is presented, which more closely matches the observed responses than previous models. Experimental results for a complementary Jerusalem cross grid are also discussed.

Ultrasound recognition in house mice: key-stimulus configuration and recognition mechanism

Abstract: 1. We determined the ability of lactating female house mice (Mus musculus, strain NMRI) to recognize natural ultrasonic calls (USC) of their pups or synthesized USC models. Recognition was shown by the mice preferentially responding to these sounds in the presence of an alternative sound signal. 2. Preferred USC models had total durations (flat top + rise and fall times) between 30 and 270 ms. Shorter and longer ones were not preferentially responded to. Response to USC models with major frequency components above 40 kHz was the same as that to natural ultrasonic calls of mouse pups. 3. The key-stimulus configuration for recognition of mouse pup ultrasound in the frequency domain can be characterized as pulses of sound energy in a narrow frequency band in the ultrasonic range with significantly less energy in adjacent frequency bands. The decisive units for call recognition are frequency bandwidths which are almost identical in width with the critical bands of hearing, a measure of frequency resolution in the auditory system. The critical frequency bands for the recognition of USC models have a bandwidth of 22.5 kHz at a center frequency near 50 kHz (the critical band of hearing is 22 kHz wide), and 15 kHz at a center frequency near 40 kHz (the critical band of hearing is 18 kHz wide). We conclude that the discrimination of ultrasonic mouse pup calls from other mouse calls and their recognition is most probably directly related to the critical band analysis in the auditory system.

Periodic wave elimination by negative feedback

Abstract: Means and method for substantially eliminating a selected periodic wave from a frequency band-limited combined wave containing other waves. The combined wave is sampled in a sampling gate, opened by short gating pulses with a frequency equal to the selected frequency divided by an integer, and greater than the Nyquist frequency for the combined wave, timed from the selected periodic waves. The samples are reconstructed in a filter with the pass-band equal to the frequency band of the combined wave. The direct-current component in the output of the sampling gate, due to any error in the timing of the instants, is used in a negative-feedback circuit to adjust the sampling instants so that the periodic wave is substantially completely eliminated.

Endoscope with signal transmission system and method of operating same

Abstract: A signal transmission system for use in an endoscope includes a solid state image sensor for picking up an image of a part of the inside of a cavity of a living body to produce a video signal indicative of the image, a frequency modulator for frequency modulating a carrier frequency with the video signal to produce a frequency modulated signal, video circuitry for receiving the modulated signal to visualize the video signal on a video display, and a transmission circuit for transmitting the modulated signal from the modulator to the video circuitry A frequency band of the frequency modulated signal is selected outside a frequency band of a noise source including an electrical instrument, such as an electrical scalpel

GaAs Monolithic Wideband (2-18 GHz) Variable Attenuators

Abstract: GaAs monolithic variable attenuators have been developed They operate in a very wide frequency band, are very small, and are controlled by one voltage Insertion loss of 2-3 dB and a dynamic range of attenuation of 10 dB were obtained in the 2-18 GHz frequency range,

Light scattering immunoassay involving particles with selective frequency band apparatus

Abstract: A technique for measuring the degree of an antigen-antibody reaction by preparing a suspension of insoluble microscopic carrier particles of at least one type carrying an antigen, an antibody or a hapten, forming an agglutination promoting or inhibiting reaction system among the insoluble carrier particles based on an antigen-antibody reaction using the suspension and one or more antigen, antibody or hapten, irradiating the solution of the reaction system with laser light and detecting the light scattered from the reaction system at one or more specific angles, detecting a signal indicative of one or more specific frequency bands from the resulting scatter spectrum, and thenceforth calculating the quantity of antigen, antibody or hapten in a specimen on the basis of the detected signal. The intensity spectrum output of filter 11 for frequency band selection is in the form of a square root and is converted into the original intensity spectrum by means of a squaring circuit 12. The output of the squaring circuit is recorded by a recorder 10.

Broadband matching a complex generator to a complex load

Abstract: Simplified analytic and computer aided design (CAD) techniques are presented for designing interstage equalizers which transfer signal power from a complex generator to a complex load impedance over a frequency band. As compared to analytic design procedures, a CAD oriented "Real Frequency Technique" requires neither a choice of a transfer function nor circuit models for complex load and generator impedances. The problem is to determine the thevenin impedance of the resistive terminated equalizer such that the transducer power gain is optimized over a prescribed frequency band when the equalizer is terminated with complex generator and load. In this process, complicated gain-bandwidth restrictions are implicitly satisfied. Realization of the positive-real input immitance to the lossless matching network terminated in one-ohm resistor completes the design. Finally, removal of this one-ohm resistor yields the desired lossless matching network or equalizer. Examples are given to exhibit the merits of the Real Frequency Technique. It is shown that results obtained utilizing the CAD procedure are superior to those of analytic methods.

Frequency response of a synthesis array: performance limitations and design tolerances.

Abstract: The frequency responses of the receiving channels of a radio astronomy synthesis array and, in particular, the variations between them for different antennas are factors that limit the accuracy and sensitivity of the instrument. A response that approximates a rectangular passband as closely as possible is advantageous from considerations of maximizing sensitivity within a given frequency band and minimizing the smearing of detail in the outer regions of a map. Tolerances on slopes, ripples, and other bandpass distortions can be determined by examining their effects with regard to loss in sensitivity and the introduction of errors in the assignment of complex gain factors for individual antennas by using calibration observations. These calibration errors are generally larger in amplitude than in phase and their effect is usually more serious than the loss in sensitivity. Velocity dispersion in waveguide transmission systems and the accuracy in adjustment of compensating time delays also affect the phase responses of the signal channels, and examination of these effects also leads to limits on system design parameters. Implementation of the tolerances derived, including some details of the filter specifications, is discussed for the very large array radio telescope of the National Radio Astronomy Observatory. Appendices contain an algorithm for performing a least squares solution for antenna gains and an analysis of the variation of the signal-to-noise ratio over the channels of a spectral line correlator system.

The computer-controlled solar radio spectrometer ‘IKARUS’

Abstract: The radiospectrometer IKARUS is a fully computer-controlled instrument covering the frequency band 0.11 to 1 GHz in steps of 1 MHz. It can automatically detect solar radio bursts and then write, on magnetic tape, 2000 measurements per second of intensity and circular polarization. The frequencies to be measured can be readily programmed in the band, compromising between frequency and time resolution. Reference noise sources are switched in automatically by the computer to calibrate the receiver at each frequency. The dynamic range is about 50 dB, recorded logarithmically with 8 bit resolution. The novelty of the instrument is its ability to measure broadband calibrated spectra (flux and degree of polarization) in the very interesting region of the lower corona.

Method and apparatus for locating pipeline damage

Abstract: Apparatus and method are provided for the location of pipeline damage and medium leak therefrom by acoustical monitoring of the soil about a pipe and recording emission noise by microphone and an amplifier which controls a peak noise indicator. Each measurement point detected by the amplifier is applied to a digital memory to display a histogram showing noise distribution along the pipe. The main frequency of the loudest measurement point is determined, and an octave filter is utilized to determine the frequency characterizing medium leakage to precisely locate the pipeline damage. Bar diagrams may be provided on a viewplate by bands of parallel arrays of light emitting diodes to display noise distribution along the pipeline. A frequency analyzer may transmit from the amplifier to the memory the peak frequency value of each observed frequency band to enable frequency analysis of the loudest measurement point. The apparatus may have a case with a lid defining openings sized for viewing the bar diagrams.

Some Experimental Results on In-Band Amplitude Dispersion and a Method for Estimating In-Band Linear Amplitude Dispersion

Abstract: In-band amplitude measurement was conducted on a 634 km test path with an oversea section (normal reflection point was on the ground), using a frequency band from 4440 to 4500 MHz Results on peak-to-peak amplitude dispersion and linear amplitude dispersion were obtained for both nondiversity and idealized space diversity receptions Potential improvements by space diversity in terms of reductions of amplitude dispersion were remarkable in the large amplitude dispersion region An analysis of the in-band amplitude pattern was made in order to identify which multiray is most responsible for amplitude dispersion during multipath fading The main cause of amplitude dispersion was found to be waves irregularly reflected from the sea surface and waves reflected from the ground, with a long delay but small amplitude A frequency correlation function for received power, which is necessary for estimating linear amplitude dispersion, was derived theoretically, for the three-path model The theoretical frequency correlation agrees well with that measured on this path

Band pass filter

Abstract: A band-pass filter circuit has series elements, comprising a parallel resonant circuit and a first inductance, and shunt elements comprising a series resonant circuit and a second inductance, the resonant circuits comprising variable capacitances to permit variation of the frequency over a frequency band. The second inductance may be a transformer. The variable capacitances may be constituted by a plurality of switchable component capacitances, having switches connected between the capacitances and ground.

Radio-frequency hazards in the VLF to MF band

Abstract: The body currents induced in a human in conductive contact with various ungrounded metallic objects like cars, trucks, fences, etc, are calculated for the frequency band 10 kHz to 10 MHz The calculated incident E-fields required to produce thershold perception and let-go currents indicate that the recently proposed ANSI guideline of 100 mW/cm2(∼615 V/m) in the frequency band 03 to 30 MHz may result in a potential for RF burns

Medium frequency linear vibrations of anisotropic elastic structures

Abstract: A new numerical method is proposed for studying medium frequency linear vibrations of anisotripic viscous elastic structures, based on an energy principle and without using the base of the vibration eigenmodes of associated conservative system. The values generated are all deterministic. These can be used to characterize the vibratory state by frequency band, to study the response to a medium frequency deterministic or random steady excitation, to determine for a fixed frequency band the space distributions of the excitation forces that, when applied to the entire structure or to a given part of the structure, produce the maximum vibrations of the entire structure or an a specified part. The method also facilitates the study of the spatial propagation of vibrations in the elastic medium and makes it possible to compute the modal density.

Multi-port combiner for multi-frequency microwave signals

Abstract: A combiner for transmitting and receiving co-polarized microwave signals in a selected propagation mode in at least two different frequency bands, the combiner comprising a main waveguide dimensioned to simultaneously propagate signals in the different frequency bands, at least a portion of the main waveguide being overmoded; at first and second junctions spaced along the length of the main waveguide for coupling signals in the different frequency bands in and out of the main waveguide, at least the first junction being located in an overmoded portion of the main waveguide and having side-arm waveguide means associated therewith for propagating signals in one of the different frequency bands; filtering means disposed within the main waveguide and operatively associated with the first and second junctions, the filtering means having (1) a stopband characteristic for coupling signals in a first one of the frequency bands between the main waveguide and the first junction and the side-arm waveguide means associated therewith, and (2) a passband characteristic for passing signals in a second one of the frequency bands past the first junction, the filtering means and the first junction suppressing spurious excitation of signals in undesired propagation modes different from the selected mode; and means for coupling signals in the second frequency band between the main waveguide and the second junction.

Method and apparatus for controlling or measuring the thickness of material layers

Abstract: In a method of controlling or measuring layer thicknesses, wherein a continuous frequency-modulated ultrasonic signal that periodically scans a frequency band is transmitted and wherein the resultant signal is evaluated. The frequency bandwidth is selected large enough that a multiple of the interference interval is covered. The spectral maxima or minima which periodically recur in the frequency spectrum of the received signal are evaluated. At a fixed modulation rate of the transmitted signal, an unambiguous interrelation exists between the repetition frequency of the maxima or minima in the spectrum and the thickness of the layer under examination. The repetition frequency increases with increasing layer thickness. According to an alternative embodiment of the invention, a ratio of harmonic amplitudes corresponding to the layer thickness is evaluated. The harmonics are produced by selecting a narrow frequency band, so that only part of the interference interval is covered. The repetition frequency of modulation is determined as a function of the desired measuring range.

System and method for encrypting a voice signal

Abstract: A system and method are disclosed for encrypting a voice signal. The input signal is filtered to provide a signal in a first path with components in a higher frequency band and a signal in a second path with components in a lower frequency band. Analog-to-digital conversion is carried out at a rate such that the frequency composition of the higher frequency path is inverted and shifted into the lower frequency band. Signals from the two paths are intermixed and converted to analog form at a rate greater than twice the rate of analog-to-digital conversion, so as to provide a randomized sequence of time segments of signals from the two paths, interspersed with gaps.

Surface wave dispersive acoustic delay line

Abstract: A dispersive acoustic delay line using reflection on slanted gratings is provided. This device comprises slanting input and output transducers each formed of pair electrode fingers. The interval of the electrodes of different polarity varying from nv/2fmin to nv/2fmax, where v is the speed of the waves, fmin and fmax the endmost frequencies of the frequency band and n the number of the harmonic on which the transducers operate. The interval of the gratings varies from kv/fmin to kv/fmax, where k is the number of the operating harmonic of the network, with n≠k.

Doppler effect blood flow sensing device displaying signals lying within a band width related to sampling frequency

Abstract: A pulsed ultrasound Doppler blood flow sensing device includes a band pass filter for extracting only the Doppler frequency shift signals from the sampled and held signals, the band pass filter having a band pass characteristic in which a variation of an attenuation degree is almost flat over at least a frequency band between -f r /2 and +f r /2 except for a region in proximity to frequency O A display displays blood flow signals which represent the obtained Doppler frequency shifts and have frequencies at least between the frequencies -f r and +f r

Equalizer having a substantially constant gain at a preselected frequency

Abstract: An equalizer of a transversal filter type is given a substantially constant gain at a preselected frequency (f p ) in a predetermined frequency band of an input and an output signal. For this purpose, the output signal is given by multiplying the routine transversal filter output by a reciprocal of an absolute value of a sum of complex tap gains (C 1 to C N+1 ). Alternatively, the input signal and successively delayed signals (IN and D 1 to D N ) may be multiplied by the reciprocal before summation. It is possible to approximate the reciprocal by omitting those of the tap gains which are near both ends (as C 1 and C N+1 ).

Small dual frequency band, dual-mode feedhorn

Abstract: The present invention relates to a dual frequency band, dual-mode feedhorn comprising three serially connected waveguide sections (20, 22, 24) and a separate discontinuity (21, 23) at each joint between waveguide sections. More particularly, the feedhorn comprises a first waveguide section (20) for supporting the TE11 mode in both frequency bands. A first discontinuity (21) symmetrically increases the first waveguide size for converting a portion of the TE11 mode in both frequency bands into the TM11 mode. The second waveguide section (22) connected to the first discontinuity comprises an aperture size for supporting the TE11 mode in both frequency bands but only the TM11 mode of the higher frequency band. A second discontinuity (23) symmetrically increases the size of the second waveguide for converting another portion of the TE11 mode in both frequency bands into the TM11 mode. A third waveguide section (24) coupled to the second discontinuity is capable of propagating both modes in both frequency bands with a length to cause the vector sums of each of the remaining TE11 and TM11 modes in each frequency band to be in phase at the exit port of the feedhorn.

Parallel-processing with surface plasmons, a new strategy for converting the broad solar spectrum

Abstract: A new strategy for efficient solar-energy conversion is based on parallel processing with surface plasmons: guided electromagnetic waves supported on thin films of common metals like aluminum or silver The approach is unique in identifying a broadband carrier with suitable range for energy transport and an inelastic tunneling process which can be used to extract more energy from the more energetic carriers without requiring different materials for each frequency band The aim is to overcome the fundamental 56-percent loss associated with mismatch between the broad solar spectrum and the monoenergetic conduction electrons used to transport energy in conventional silicon solar cells This paper presents a qualitative discussion of the unknowns and barrier problems, including ideas for coupling surface plasmons into the tunnels, a step which has been the weak link in the efficiency chain

Method of and apparatus for measuring surface temperature of metallic body

Abstract: Disclosed is a method of measuring the surface temperature of a metallic body. The method comprises: disposing a reflecting member such that the reflecting member constitutes a resonator in cooperation with a substantially flat surface of the metallic body; measuring the mean reflectivity of the resonator over a predetermined frequency band having a center frequency coinciding with the resonance frequency of the resonator, as well as the luminance temperature of the resonator; and computing the surface temperature of the metllic body from these measured values. Disclosed also is an apparatus for carrying out this measuring method. The method and apparatus are suited particularly to the measurement of the surface temperature of a steel sheet heated to a temperature ranging between 500° and 800° C.

Frequency-spreading coupler

Abstract: A wide band travelling wave amplifier including an input waveguide coaxia disposed about an interaction waveguide. Both waveguides are tapered with the same direction of increasing cross-section. The interaction waveguide is a high-pass filter while the input waveguide is a low pass filter. The input waveguide is positioned relative to the interaction waveguide so that each cutoff plane in the input waveguide corresponding to a given frequency, ω c , is displaced in the direction of increasing cross-section from a cutoff plane in the interaction waveguide corresponding to ω c where ω c is any frequency in the frequency band of the amplifier. A slot, disposed between the cutoff planes corresponding to ω c couples the ω c frequency component of an input wave from the input waveguide to the interaction waveguide.

Method for interchanging n partial bands

Abstract: A method for interchanging the frequency positions of n partial bands, each having a bandwidth b, of a signal frequency band, by the steps of: sampling signals in the frequency band at an input sampling rate; separating the sampled signals associated with each partial band into separate channels in stages in each of which sample signals are separated into high frequency and low frequency groups and the sampling rate is reduced; altering the positions of the channels in a scrambling matrix controlled by a random sequence generator; and spectrally recombining the signals in the separate channels into a signal extending across the signal frequency band.

Notch antenna for a wide frequency band

Abstract: Notch antennae consist either of a cut in a metallic structure or of an electrically conductive frame on a metallic body, and of a tuning capability to a specific frequency. This is implemented according to the invention in that the connecting cable is connected at the one end to the notch antenna, i.e. in the region of the open end in the case of a cut, and at its one end in the case of a frame. Connected in parallel with the connecting cable is a capacitor whose value is changed as a function of the frequency band in order to compensate for the reactive components of the antenna internal impedance. In the region of the opposite end, i.e. in the inner part in the case of a cut and at the opposite end in the case of a frame, a terminating reactance is inserted whose value is likewise changed as a function of frequency such that the resistive components of the antenna internal impedance has the desired magnitude. The latter may consist of the parallel connection of variable capacitances and a connected inductor. The capacitances are formed by capacitors which can be connected in parallel and can be switched, for example, by PIN diodes.

Narrow-frequency band acoustic transducer

Abstract: A narrow-frequency band, acoustic transducer of high conversion efficiency over a narrow-frequency band, which transducer comprises: a truncated diaphragm having a depressed, circular area and a peripheral edge about the circular area and a convex cap section extending outwardly from the circular area; a vibration board adhesively secured about the peripheral edge of the diaphragm, to couple acoustically the vibration board to the diaphragm on one side; and a piezoelectric element centrally secured to the other side of the vibration board, with electrical leads to the piezoelectric element, whereby electrical energy input to the piezoelectric element provides a high decibel acoustical output about the natural resonance frequency of the vibration board.

Color solid state image pick-up device

Abstract: A color solid state image pick-up device in which a color filter array is arranged so as to correspond to each picture element of the solid state image pick-up elements and the output from the solid state image pick-up elements is processed so as to obtain the pseudo-brightness signal, being characterized in that at least one of the brightness signal including a high frequency band component used as the image signal, the brightness signal including a low frequency band component and the brightness signal used as the color difference signal is obtained on the basis of the different output signal from that connected with other brightness signal.

Microwave integrated circuit mixer

Abstract: In a mixer using a planar circuit such as a strip line or a microstrip line etc., an IF signal interruption circuit (9, 27) which passes an RF signal but exhibits an open-circuit impedance against an IF signal is provided in shunt with a main line (2,21) on which the RF signal propagates toward a mixer diode (3, 22), and a low-pass filter (10, 11, 28) is connected in the vicinity of the IF signal interruption circuit in order to short-circuit a mount point of the diode for the IF signal by high frequency short-circuiting technique wherein an open-ended quarter wavelength transmission line or a short-circuited half-wavelength transmission line is used, whereby low noise performance can be obtained over a wide frequency band even under such an operating condition that the IF signal is in the GHz band.

Autoregressive Recovery of the Acoustic Impedance

Abstract: This paper presents a method of recovering the acoustic impedance from reflection seismograms using autoregressive (AR) modeling, an approach originally applied to deconvolution by Lines and Clayton (1977). The algorithm which we describe is novel both in the manner in which the missing low‐ and high‐frequency information is predicted, and in the fact that the prediction may be constrained if acoustic impedance information is available. The prediction of the low frequencies treats the missing data as a gap which extends from the low‐frequency cut‐off in the negative frequency band to the corresponding frequency in the positive frequency band. The conjugate symmetry which governs the behavior of the spectrum in the band is taken into account in the prediction. The missing high frequencies are predicted using a modified minimum entropy norm in the frequency domain. Both synthetic and field examples are presented and illustrate the robustness of the new AR algorithm under a variety of conditions. The field e...