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Showing papers on "Frequency band published in 1978"


Journal ArticleDOI
TL;DR: In this paper, the spectral content and variations in time of the coda of seismic oscillations following the body and surface waves of local earthquakes were studied, and it was shown that the spectrum of a coda as a function of time can be described as the product of two factors, independent of time, reflecting the effects of the medium and the same for all sources.
Abstract: We studied the spectral content and variations in time of the coda of seismic oscillations following the body and surface waves of local earthquakes. Within narrow frequency bands, the form of the envelope of the coda is remarkably stable—independent of epicenter (and therefore epicentral distance), depth of focus, and all other parameters of the source. Only the absolute amplitude of the coda differs from event to event. Similarly, the forms of the coda at two stations from the same earthquake overlap one another, differing only in absolute amplitude by a factor that is the same for all events. Hence given the form of the coda, its amplitude in any frequency band may be parameterized by one number—the amplitude at a certain time. Therefore, the spectrum of the coda as a function of time can be described as the product of two factors—one, independent of time, is dependent only on the source, and the other, reflecting the effects of the medium and the same for all sources, gives the time dependence for each frequency band. Segments of the envelopes with time can be matched by simple theories of scattering. Using the theoretical relationships, estimates of Q can be made and show that for any time interval, Q increases with frequency, approximately proportional to the square root of frequency. As longer elapsed times are considered, the estimates of Q increase, suggesting greater penetration of seismic energy into the higher Q parts of the Earth. The spectra of different events can be compared directly by comparing the spectra of the codas at the same elapsed time. Such a comparison reveals a wide variety of different source spectra. By using empirical relations among coda spectra, observed S -wave spectra, and theoretical constraints, an estimate of the spectrum radiated by the source can be calculated from the coda spectrum. Source parameters (seismic moment, corner frequency of the radiated spectrum, calculated stress drop, etc.) can be determined from coda spectra of events with many different moments and in different regions, with the same station. The results show several interesting features dependent on the seismic moments and on the regions in which the earthquakes occurred.

523 citations


Patent
31 Jan 1978
TL;DR: In this paper, a tunable local oscillator supplies a heterodyning signal to the mixer to convert any selected channel of the received signal to an intermediate frequency (i.f.) band chosen to avoid image interference from undesired channels.
Abstract: A tuner for receiving signals broadcast on two spaced bands, each divided into several channels, has two fixed bandpass filters, one to pass all of the channels in the lower frequency band and the other to pass all of the channels in the higher frequency band. The tuner includes a mixer to which signals of either band are supplied by selective operation of a double-throw switch. A tunable local oscillator supplies a heterodyning signal to the mixer to convert any selected channel of the received signal to an intermediate frequency (i.f.) band chosen to avoid image interference from undesired channels, whether the local oscillator frequency is above or below the selected channel. To ease the constraints on the choice of the i.f. band, different i.f. filters tuned to first and second i.f. bands may be used for the higher and lower received bands. A second double-throw switch ganged with the first switch can then be used to direct the heterodyned signals to the proper i.f. filter.

98 citations


Patent
26 Oct 1978
TL;DR: In this paper, the authors proposed a means and method of eliminating a selected wave from a frequency band containing a plurality of waves, by sampling the plurality of wave at a rate greater than the nyquist rate for the frequency band in herz, at instants at which the selected wave has zero amplitude.
Abstract: This invention provides means and method of eliminating a selected wave from a frequency band containing a plurality of waves, by sampling the plurality of waves at a rate greater than the nyquist rate for the frequency band in herz, at instants at which the selected wave has zero amplitude, and integrating the sequence of samples so obtained to produce a replica of the plurality of waves less the selected wave. The plurality of waves less the selected wave may be subtracted from the plurality of waves, after adjustment of relative amplitude and delay, so that the selected wave is obtained substantially free of other waves of the plurality of waves. Thus a selected undesired wave, with a maximum period between successive instants of zero amplitude of less than the nyquist interval for the frequency band, may be substantially eliminated without affecting other waves; a selected desired wave, with a maximum period between successive instants of zero amplitude of one-half the period of the bandwidth of the frequency band, may be recovered substantially free from noise.

64 citations


Patent
20 Mar 1978
TL;DR: In this paper, a frequency band dividing filter comprises at least two unit circuits connected in cascade connection, and at least one supplemental delay circuit, each of which comprises a low-pass filter having a specific filtering frequency band with a steep cut-off characteristic, a delay circuit connected in parallel with said lowpass filter and having a frequency phase characteristic substantially equal to the frequency phase characteristics of said low pass filter in the pass band thereof, and a subtraction circuit connected to the output sides of the low pass filters and said delay circuit thereby to carry out subtraction of the outputs of
Abstract: A frequency band dividing filter comprises at least two unit circuits connected in cascade connection of at least two stages, and at least one supplemental delay circuit. Each of the unit circuits comprises a low-pass filter having a specific filtering frequency band with a steep cut-off characteristic, a delay circuit connected in parallel with said low-pass filter and having a frequency phase characteristic substantially equal to the frequency phase characteristic of said low-pass filter in the pass band thereof, and a subtraction circuit connected to the output sides of said low-pass filter and said delay circuit thereby to carry out subtraction of the outputs of said low-pass filter and said delay circuit. The supplemental delay circuit is connected in parallel with the second stage unit circuit, which is connected to the first stage unit circuit in cascade connection, and has the same characteristic as the characteristic of the delay circuit of the second stage unit circuit.

58 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that in the audible range of frequencies, neither the approximation which treats the shear layer as a scattering interface with a convected undulating shape nor the opposite, high frequency limit obtained by means of asymptotic estimation of integrals derived for the diffraction of rays in turbulence is sufficient to provide a satisfactory theory of the observations.
Abstract: It has been observed experimentally by Candel, Julienne & Julliand (1975) that a monochromatic test tone generated by a source inside a jet is received outside as a broad frequency band of definite shape. This phenomenon of spectral broadening occurs during transmission through the shear layer, which generally has a randomly irregular and unsteady shape, contains in addition distributed turbulence, and separates the jet and the ambient medium. We show in the first place that, in the audible range of frequencies, neither the approximation which treats the shear layer as a scattering interface with a convected undulating shape nor the opposite, high frequency limit obtained by means of asymptotic estimation of integrals derived for the diffraction of rays in turbulence is sufficient to provide a satisfactory theory of the observations. The refraction integrals obtained in part 1 have to be evaluated exactly in order to account for the phenomenon of spectral broadening, the methods used possibly being of interest in other branches of wave theory. The formation of the transmitted spectrum from an incident tone can be illustrated by representing a simple shear layer as an array of elements each re-radiating energy received from the source with its own characteristic attenuation and frequency shift. A computer program is used to obtain spectra under conditions corresponding to the experiments of Candel, Guedel & Julienne (1975) and gives encouraging agreement with their measurements, which were made with high frequency sources immersed in low speed jets. The theory can also be applied to the prediction of spectra received at various angles to the axis of high subsonic jets, but depends on extrapolation when supersonic exhausts are considered. We conclude with an example of the possible relevance of spectral broadening as a means of reducing the noise disturbance from current jet-powered aircraft, such as Concorde.

52 citations


PatentDOI
TL;DR: In this paper, a vibratory seismic energy source capable of generating significant energy over a broad frequency band is proposed. But the vibrating baseplate and associated structure are designed to have minimum weight while still retaining sufficient structural integrity to permit the use of high actuator forces.
Abstract: A vibratory seismic energy source capable of generating significant energy over a broad frequency band. The vibrating baseplate and associated structure are designed to have minimum weight while still retaining sufficient structural integrity to permit the use of high actuator forces. This, coupled with a large reaction mass results in the generation of significant energy levels in the earth at high frequencies.

36 citations


Patent
18 Aug 1978
TL;DR: In this paper, a dual frequency band directional antenna with a cavity reflector antenna and an electrically separate loop radiator was proposed, with the radiation patterns of both sources being unidirectional over both frequency bands and with their radiation maxima directed into the center axis normal to the bottom plate of the cavity structure.
Abstract: A dual frequency band directional antenna or system in the form of a cavity reflector antenna mechanically combined and radiation-coupled with a loop of approximately the same shape and periphery as the rim edge of the cavity reflector, which loop is arranged outside and in front of, and in close proximity and parallel to the cavity rim edge, and, when properly energized, acts for the lower frequency band as a loop radiator with preselected field polarization, whereby the entire cavity structure serves two purposes by acting simultaneously as reflector for the higher frequency band cavity reflector antenna and for the lower frequency band, electrically separate loop radiator, with the radiation patterns of both sources being unidirectional over both frequency bands and with their radiation maxima directed into the center axis normal to the bottom plate of the cavity reflector structure.

33 citations


PatentDOI
TL;DR: In this paper, an improved audio signal processing system synthesizes from an audio signal, an enhanced audio signal by sensing signal energy of the audio signal within a preselected frequency portion of the signal, dividing the sensed signal energy into a plurality of discrete bands according to the frequency thereof and generating, responsively to the signal energy in each of the bands, a like plurality of second signals each of which includes frequency components which are subharmonics of the frequencies of the corresponding frequency band.
Abstract: An improved audio signal processing system synthesizes from an audio signal, an enhanced audio signal by sensing signal energy of the audio signal within a preselected frequency portion of the audio signal, dividing the sensed signal energy into a plurality of discrete bands according to the frequency thereof and generating, responsively to the signal energy in each of the bands, a like plurality of second signals each of which includes frequency components which are subharmonics of the frequencies of the corresponding frequency band. The second signals are combined so as to provide a combined signal and the latter is added to the audio signal to provide the enhanced audio signal.

32 citations


Patent
22 Dec 1978
TL;DR: In this article, several channels in each group are continuously measured to find which channels have the least ambient energy levels, then one of those channels is selected in a random manner to transmit data.
Abstract: HF and VHF radio channels which are subject to time-varying propagation aalies and to interference are arranged in groups according to frequency band Within each group are several channels, each spaced sufficiently close so that they experience essentially the same propagation The several channels in each group are continuously measured to find which channels have the least ambient energy levels, then one of those channels is selected in a random manner to transmit data

32 citations


Journal ArticleDOI
TL;DR: A high-precision standard for the calibration of audio-frequency phase meters has been designed using a microprocessor to generate the test signals.
Abstract: A high-precision standard for the calibration of audio-frequency phase meters has been designed using a microprocessor to generate the test signals. The accuracy is better than 0.01 degree over a frequency band from dc to 5 kHz and decreases to 0.1 degree at higher audio frequencies.

27 citations


Patent
27 Nov 1978
TL;DR: In this paper, the authors present a circuit for detecting the presence of a spectrally distributed signal having a known distribution, e.g. spread spectrum, in a strong noise environment.
Abstract: Circuitry and methods are presented for detecting the presence of a spectrally distributed signal having a known distribution, e.g. spread spectrum, in a strong noise environment. The signal is split into two channels, each filtering a predetermined frequency band within the given spectrum. The channels are tuned and balanced so that they pass differential amounts of signal energy that may be present but provide equalized noise outputs. The channels are alternately coupled to the input of an energy detector which provides a DC component responsive to the difference in the signal levels of interest, while effectively cancelling noise energy components in each channel. In the spread spectrum example the frequency bands are typically selected to the maximum and a null location in a ##EQU1## distribution.

Journal ArticleDOI
TL;DR: The DRS-8 is a 91 Mbit/s long haul digital radio system designed for use in the Canadian 8 GHz frequency band and the considerations which lead to the choice of Quadrature Partial Response Signaling (QPRS) are discussed.
Abstract: The DRS-8 is a 91 Mbit/s long haul digital radio system designed for use in the Canadian 8 GHz frequency band. This paper discusses the considerations which lead to the choice of Quadrature Partial Response Signaling (QPRS) for this application. A method of implementing QPRS that circumvents power amplification difficulties and permits the use of simple conventional filtering and equalization is presented. The computer analysis program and the design strategy used in the system filter design are described. Details of the signal shaping filters as well as details of carrier and clock synchronization are given. Finally, measured system performance is presented and compared with computed performance.

Patent
03 Nov 1978
TL;DR: In this paper, a magnetically tunable bandpass filter is proposed for the miwave regions, particularly for frequencies between 0.1-4 GHz, which can pass only certain frequencies from one conductor to a separate conductor depending upon the frequency band and the magnetic field applied across the filter.
Abstract: The invention is a magnetically tunable bandpass filter for use in the miwave regions, particularly for frequencies between 0.1-4 GHz. A magnetically tunable bandpass filter is a filter which will pass only certain frequencies from one conductor to a separate conductor depending upon the frequency band and the magnetic field applied across the filter. The tuning of the center frequency can be achieved at relatively fast electronic switch times. The center frequency is the frequency at which the most coupling exist due to the applied magnetic field. Two striplines are placed at 90° relative to one another with one end of one stripline overlapping one end of the other with the overlapped ends connected to ground. A disc of ferromagnetic material is placed between the two striplines. By applying a dc magnetic field and by changing the angle of the magnetic field within the disc plane, microwave signals can either be transmitted or not from one stripline to the other at a given frequency depending upon the applied magnetic field applied and the angle of application.

Journal ArticleDOI
TL;DR: The nonlinearity measurement technique described in this article uses an adapted conventional lock-in-amplifier that enables us to measure small nonlinearities over a wide frequency band and is more sensitive than the 1/f noise measurement used to detect non-homogeneous structures in conductors, resistors and semiconductor components.
Abstract: The nonlinearity measurement technique described uses an adapted conventional lock-in-amplifier. This technique enables us to measure small nonlinearities over a wide frequency band and is more sensitive than the 1/f noise measurement used to detect non-homogeneous structures in conductors, resistors and semiconductor components. Results illustrating uses of this method are presented for different types of resistor and semiconductor structures.

Journal ArticleDOI
TL;DR: In this paper, a high-field domain at the anode is studied by varying doping density, applied bias voltage, and doping notch depth and width near the cathode, and it is shown that the frequency band of negative conductance of the trapped-domain mode depends significantly on the doping density.
Abstract: The trapping conditions of a high-field domain at the anode are studied by varying doping density, applied bias voltage, and doping notch depth and width near the cathode. It is shown that the frequency band of negative conductance of the trapped-domain mode depends significantly on the doping density, and a diode having the doping density of 3 × 1015/cm3exhibits the negative conductance over the wide range from 4 GHz to 42 GHz. The upper frequency limit of the negative conductance is due to the series resistance in the low-field region and the lower limit is determined by carrier transit-time effects in high-field region. The operation mode of a trapped-domain diode will change into a traveling dipole or accumulation mode from a trapped-domain mode depending on the doping density and the operation frequency for a large-signal operation.


Patent
06 Mar 1978
TL;DR: In this article, a radio frequency burst signal memory system is described, which includes a feedback loop for recirculation of the received RF burst signal when a proper burst signal is detected.
Abstract: A radio frequency burst signal memory system is described which includes a feedback loop for recirculation of the received RF burst signal when a proper burst signal is detected. The output from an RF amplifier is split into separate frequency bands by a diplexer. When one of these bands is sensed at the input, only signals of the sensed frequency band are recirculated.

Patent
02 Oct 1978
TL;DR: In this paper, a scanning microwave detection apparatus provides a moisture profile along the width of a predetermined sample such as a sheet or web, where each sensor couples microwave energy with a finite area of the sample.
Abstract: The scanning microwave detection apparatus provides a moisture profile along the width of a predetermined sample such as a sheet or web. The apparatus includes a number of moisture sensors spaced along the width of the sample, such that each sensor couples microwave energy with a finite area of the sample. Each sensor is preferably a pair of horns with one located on each side of the sample to provide a microwave path through the sample. A first filter is coupled to the input of each sensor and a second filter is coupled to the output of each sensor. The pair of filters associated with each sensor is tuned to the same frequency, and each of the pairs of filters are tuned to a different predetermined frequency within a selected frequency band such that the sensors operate at different frequencies, within substantially non-overlapping frequency band-passes. The filters are preferably directional. A microwave source is coupled to the input filters and is controlled to sweep through the selected frequency band to sequentially energize each sensor. A detector is coupled to the output filters for detecting the sequential energy outputs of the sensors. These sequential outputs are a function of the moisture content of the finite areas of the sample at the sensors.

Patent
03 Jul 1978
TL;DR: In this paper, the authors proposed a method to minimize the negative dynamic pressure or stress excursion of an acoustic signal with respect to the average pressure and stress present in the absence of the signal.
Abstract: Methods and apparatus describedmaximize, within a predetermined frequency band, the continuous or near-continuous transmission of broadband acoustic power into a medium having a finite tensile strength such as water or earth. Such methods and apparatus also minimize, for a given broadband acoustic power level in a given frequency band, the negative dynamic pressure or stress excursion of an acoustic signal with respect to the average pressure or stress present in the absence of the signal. Such signals may be transmitted for geophysical exploration purposes. The signals place the medium alternately under compressive and tensile stresses with respect to some average stress, where the time duration of the application of the compressive stress is short compared with the time duration of the application of the tensile stress. The tensile stress does not exceed the tensile strength of the medium or its interfaces. For highest efficiency, the minimum time duration of the compressive stress is in excess of one-half period of the upper frequency limit of the desired spectral band of the signal, while the maximum time duration of a contiguous tensile and compressive stress pair is approximately one period of the desired lower frequency limit of the band. The tensile stress waveform is preferably rectangular in shape.

Patent
Richard Dr Ing Klemm1
24 Nov 1978
TL;DR: In this paper, the order of interference suppression and coherent integration is changed such that the echo values are first fed to a circuit to effect a Fourier transformation, and a sub-optimal detection method suitable for real-time operation is derived from the optimum detection model in that sub-matrices symmetrical with the principle diagonal are formed from the power spectrum matrix.
Abstract: Disturbing components of the Doppler frequency spectrum in a radar receiver, having coherent integration, are suppressed In this technique, the order of interference suppression and coherent integration is changed such that the echo values are first fed to a circuit to effect a Fourier transformation Then, the disturbing components in the frequency band are deliberately suppressed, and a sub-optimal detection method suitable for real-time operation is derived from the optimum detection model in that sub-matrices symmetrical with the principle diagonal are formed from the power spectrum matrix, through which approximate decorrelation of the disturbing components is achieved

Patent
14 Sep 1978
TL;DR: The AF amplifier as discussed by the authors consists of a main channel comprising two amplifiers and at least one secondary channel containing an audio band-pass filter and a dynamic compressor (6, 8, 9).
Abstract: The AF amplifier, for radio receivers and hi-fi equipment, consists of a main channel comprising two amplifiers and at least one secondary channel containing an audio band-pass filter and a dynamic compressor (6, 8, 9). The compressor increases the level in the selected frequency band at low volumes so that it matches the curves of equal audio sensitivity. At greater sound volumes this increase increases only slightly in relation to volume. The compressor consists of a gain-controlled amplifier (6), and amplifier (8) and a rectifier (9) whose output controls the gain-controlled amplifier. The amplifier's filtered output (7) is added (3) to the main channel's signal.

Journal ArticleDOI
TL;DR: The ultrasound carotid vessel imager uses a continuous-wave Doppler flow detector on a hand-guided position sensing arm and a microprocessor-controlled image memory and display to detect directionally separated flow signals.
Abstract: The ultrasound carotid vessel imager uses a continuous-wave Doppler flow detector on a hand-guided position sensing arm. The directionally separated flow signals are passed through a two channel audiofrequency real-time spectrum analyser to a microprocessor-controlled image memory and display. Transducer position defines memory address; image data (16 intensity levels) is set by the Doppler signal power detected within a preset broad frequency band. Early results are illustrated

Patent
10 Apr 1978
TL;DR: In this article, a phase-symmetrical orthomode transducer was used for double polarization in two high frequency bands of different frequency positions, and two 3-dB 90° directional couplers were used to handle right and left circular polarized signals of the lower frequency band and the higher frequency band, respectively.
Abstract: Antenna system for double polarization in two high frequency bands of different frequency positions includes a orthomode transducer, in the following text called polarization filter having an antenna end terminal and two directional terminals, one being for right circular polarized waves, and the other being for left circular polarized waves. These directional terminals connect, respectively, with two frequency filters which separate the signals into the lower of the two high frequency bands, and the higher of the two high frequency bands. There are two 3-dB 90° directional couplers, one of which handles right and left circular polarized signals of the lower frequency band, and the other of which handles right and left circular polarized signals of the higher frequency band. The polarization filter is constructed to be phase-symmetrical with respect to its transit paths. The directional terminals of the polarization filter are connected directly to the frequency filters, respectively, or through two structurally symmetrical 45° twisted components of different twisting directions. The connection lines between the frequency filters and the directional couplers in each case for the two frequency bands occupy dual polarization directions of the same frequency range. These are phase-symmetrical pairs of lines with connection elements which match one another in pairs at the same point of the line.

Patent
Konrad Dr Walliser1
17 Jul 1978
TL;DR: In this article, an electroacoustic transducer has the resonant frequency of the cavity in front of its membrane-like piezoelectric plate determined by an appropriate choice of the number and length of the mouthpiece apertures, the thickness of the plate and the vol. between mouthpiece and plate so that the frequency and the oscillations lie at the upper limit of the frequency band of relevance to telephony (200-4000Hz).
Abstract: The electroacoustic transducer has the resonant frequency of the cavity in front of its membrane-like piezoelectric plate and the oscillations of the plate itself determined by an appropriate choice of the number and length of the mouthpiece apertures, the thickness of the plate and the vol. between mouthpiece and plate so that the frequency and the oscillations lie at the upper limit of the frequency band of relevance to telephony (200-4000Hz). Above this upper frequency limit a low pass filtering effect is achieved. The resonant frequency of the mouthpiece region is c. 2.5 kHz when the number of holes is c. 17, their length c. 3mm and their dia. 3 mm. The plate's oscillation frequency is c. 3.4 kHz, its thickness 150 microns and dia. 43 mm.

Patent
20 Mar 1978
TL;DR: In this paper, a digital magnetic recording system is described that utilizes partial response signalling to achieve the Nyquist data pulse rate with minimum bandwidth, and a C. C. bias is introduced to linearize the magnetic medium which, inter alis, permits reliable multilevel data storage without impairing data accessibility.
Abstract: A digital magnetic recording system is disclosed that utilizes partial response signalling to achieve the Nyquist data pulse rate with minimum bandwidth. A. C. bias is introduced to linearize the magnetic medium which, inter alis, permits reliable multilevel (greater than 2) data storage without impairing data accessibility. Preferably Class IV partial response is utilized with one or more sinusoidal lobes in the data frequency spectrum. The basic binary data to be stored is converted to, for example, ternary and the ternary data is precoded. The precoded ternary data is recorded on the magnetic medium via an interleaved dipulse sequence having a spectral null slightly outside the data frequency band. A pilot tone is inserted at the spectral null for timing recovery and automatic gain control.

Patent
29 Mar 1978
TL;DR: In this article, a tuning apparatus for a broadcast receiver having a dial scale calibrated to represent broadcast frequencies over a predetermined frequency band, and along which an indicator is movable for indicating the broadcast frequency to which the tuning apparatus is actually tuned, is presented.
Abstract: In a tuning apparatus for a broadcast receiver having a dial scale calibrated to represent broadcast frequencies over a predetermined frequency band, and along which an indicator is movable for indicating the broadcast frequency to which the tuning apparatus is actually tuned; a sensor is movable with the indicator, at least one presetting element is movable along the dial scale for indicating a respective preset broadcast frequency and each such element coacts with the sensor whenever the broadcast frequency to which the tuning apparatus is tuned corresponds to the respective preset broadcast frequency, a control signal generator produces a control signal in response to the coaction of the sensor with each of the presetting elements, and a control circuit is responsive to the control signal to control a function of the tuning apparatus, such as, a muting and/or automatic frequency control operation of the tuning Johnson 310 239

PatentDOI
TL;DR: In this paper, the authors proposed a method for seismic exploration on land and on ocean beds by emitting vibrational acoustic signals of long time-duration within a desired frequency spectrum at one or a number of points, the signals corresponding to the waves received from the reflectors being then processed.
Abstract: Seismic exploration on land and on ocean beds is performed by emitting vibrational acoustic signals of long time-duration within a desired frequency spectrum at one or a number of points, the signals corresponding to the waves received from the reflectors being then processed. The method further consists in forming the complex spectrum of the received signal corresponding to the emitted signal in respect of each frequency band, in forming the complex spectrum of a reference of the emitted signal in respect of each frequency band and in dividing the complex spectrum of the received signal by the complex spectrum of the reference of the emitted signal, at least an external portion of each complex spectrum being eliminated in the case of each complex spectrum.

Patent
28 Mar 1978
TL;DR: In this article, the beam width of an antenna constant in a wide frequency band was achieved by making the beam irradiating the main reflective mirror of an opening surface antenna contain at least the 1st side lobe.
Abstract: PURPOSE:To make the beam width of an antenna constant in a wide frequency band by making the beam irradiating the main reflective mirror of an opening surface antenna contain at least the 1st side lobe

Patent
03 Oct 1978
TL;DR: In this article, the subwaveguide is coupled via the coupling holes on E or H plane of the major waveguide so the recommended frequency band is the n th harmonic to the fundamental frequency band.
Abstract: PURPOSE:To pick up only the n th harmonic component with separation, by coupling the subwaveguide via the coupling holes on E or H plane of the major waveguide so the recommended frequency band is the n th harmonic to the fundamental frequency band.

Patent
05 Sep 1978
TL;DR: In this article, a bidirectional telewriting system for two-way transmission of telewriting data over a transmission channel which is shared by a speech link is presented, where a commutator at each terminal causes a reversal in the direction of transmission of the telewriting over the single carrier.
Abstract: A bidirectional telewriting system for two-way transmission of telewritingata over a transmission channel which is shared by a speech link. A frequency window is used within the speech frequency band, within which a single carrier is used. A commutator at each terminal causes a reversal in the direction of transmission of the telewriting data over the single carrier.