Showing papers on "Frequency band published in 1969"

System for the parallel transmission of signals

Abstract: A system for transmission of continuous signals wherein the signals are sampled into sections, which sections are subsequently assembled into groups A frequency band is permanently associated with each section dependent upon its position within the group and for each section an alternatingcurrent pulse is produced, the frequency of said alternatingcurrent pulse being within the frequency band associated with said section and which contains the signal contents of the corresponding section The alternating-current pulses are longer than the sections and are temporarily overlapping one another

Method and apparatus for measuring lithological characteristics of rocks

Abstract: A method by which physical and mechanical characteristics of rocks are measured during drilling, comprises picking up a signal representing the vibrations of a train of rods forming part of drilling gear, selecting the components of the said signal which, after peak-clipping, are in a frequency band which is centered on, and preferably is related to, a characteristic frequency of the tool, establishing from the components thus selected, a value which is representative of the amplitude of the vibrations, and correlating this value with the drilling depth.

Computer Optimization of Inhomogeneous Waveguide Transformers

Abstract: The problem of designing broadband multisection stepped rectangular waveguide impedance transformers, when the input and output guides have different cutoff frequencies but propagate the same mode, is formulated in general terms for direct optimization by digital computer. The formulation is sufficiently flexible to allow nonideal junction discontinuity effects and mismatched terminations to be taken into account during optimization. Constraints placed on the width, height, or length of any section need be dictated only by considerations for dominant mode propagation and the requirement of small (but not necessarily negligible) junction discontinuities. The objective of the present formulation is a minimax equal-ripple response over a predetermined frequency band satisfying the constraints selected for the particular problem. The ripple search strategy to locate the maximum reflection coefficient within the band and the razor search strategy to minimize it, as described by Bandler and Macdonald in another paper, were employed. Constrained optimum equal-ripple solutions to examples previously published by Young, Matthaei et al. and Riblet are presented. They demonstrate the considerable improvements made possible by the present formulation with regard to performance, reduction in number of sections, and physical size. The approach used in this paper should also find application in the design of broadband microwave matching or equalizing networks consisting of noncommensurate components and for which exact synthesis techniques may be unavailable.

Dual frequency band,polarization diverse tracking feed system for a horn antenna

Abstract: THE APPARATUS OF THE PRESENT INVENTION CONSTITUTES A FEED TO A SINGLE HORN-TYPE ANTENNA PROVIDING ONE FREQUENCY AND FOR COMMUNICATIONS AND MONOPULSE TRACKING AND A HIGHER FREQUENCY BAND FOR HIGH POWER TRANSMITTING MORE PARTICULARLY, THE HIGHER FREQUENCY BAND IS OF THE ORDER OF 50-100 PERCENT HIGHER THAN THE FREQUENCY BAND FOR THE RECEIVE AND TRACKING FREQUENCIES. IN THIS LATTER FREQUENCY BAND, THE ANTENNA IS CAPABLE OF RECEIVING COMMUNICATIONS AND HAVING MONOPULSE TRACKING CAPABILITY WITH POLARIZATION DIVERSITY, I.E., OTHOGONAL LINEAR, ORTHOGONAL CIRCULAR, ROTATABLE LINEAR OR ARBITRARY ELLIPTICAL POLARIZATIONS. CROSS-POLARIZATION OF ALL PATTERNS IS VERY LOW AND CROSS-TALK BETWEEN AZIMUTH AND ELEVATION TRACKING CHANNELS IS SUBSTANTIALLY ZERO. ALSO, HIGH EFFICIENCY TRACKING CAN BE ACHIEVED OVER A BROAD FREQUENCY RANGE WITHOUT RETUNING OF COMPONENTS SUCH AS COUPLERS OR FILTERS.

Dipole radio antennae

Abstract: Dipole whip antenna arrangements are disclosed which are capable of operating over a wide frequency band without the use of continual manual or automatic tuning. This is achieved by connecting the dipole whip antenna to the ground plane through a reactance network which is specially designed so as to match the impedance at the feed point of the dipole arrangement to a desired value over the desired frequency band. For this purpose, the reactance network is an active network, and operates by effectively cancelling out the reactance of the antenna.

Multiaperture radiating array antenna

Abstract: An integrated function microwave radiating structure capable of radiating electromagnetic energy at several selectively predetermined different frequency bands simultaneously and which can be used as an element of a large microwave array antenna is disclosed. The unitary substantially rectangular structure comprises multiple, closely spaced sets of radiating elements of various possible configurations located and supported in a defined aperture area in an interlaced contiguous manner with respect to each other. Each set of radiating elements radiates over a particular frequency band within the total band over which coverage is required. By energizing each radiating element independently in a predetermined phase and amplitude relationship with respect to the other elements, the radiated composite beam (from each of the elements) can be scanned in either the horizontal or vertical planes. Undesired mutual interaction affects between the closely spaced adjacent elements operating at different frequencies are minimized by cross-polarizing techniques.

Digital waveform generator

Abstract: A digital waveform generator is provided for synthesizing a digital waveform having only the fundamental and prescribed harmonic components present. Additionally, a frequency translation system is provided for selecting a band of frequencies from a given input spectrum and to translate it, either erect or inverted, to a new frequency band. This system is application to both N-path filters or modulators and to R-C digital filters.

Voltage-controlled plural-band tuner for a wave signal receiver

Abstract: Selective tuning to any broadcast channel within a plurality of frequency bands is achieved by voltage-controlled tunable circuitry, such as the type employing varactor or varicap diodes, responsive to an adjustable DC tuning voltage, having unique levels assigned to the various desired channels. The voltage level, in tuning across all of the frequency bands, must be varied over a predetermined amplitude range, portions of which range are effectively assigned to different respective ones of the bands. Band switching of the tunable circuitry occurs automatically and electronically under control of the tuning voltage. Each time its amplitude is changed from a level in one portion of the range to a level in another portion, the tuner is made tunable over a different frequency band. No mechanical switches are needed to accomplish band switching.

Computer Optimization of Inhomogeneous Waveguide Transformers

Abstract: The problem of designing broadband multisection stepped rectangular waveguide impedance transformers, when the input and output guides have different cutoff frequencies but propagate the same mode, is formulated in general terms for direct optimization by digital computer. The formulation is sufficiently flexible to allow nonideal junction discontinuity effects and mismatched terminations to be taken into account during optimization. Constraints placed on the width, height, or length of any section need be dictated only by considerations for dominant mode propagation and the requirement of small (but not necessarily negligible) junction discontinuities. The objective of the present formulation is a minimax equal-ripple response over a predetermined frequency band satisfying the constraints selected for the particular problem. The ripple search strategy to locate the maximum reflection coefficient within the band and the razor search strategy to minimize it, as described by Bandler and Macdonald in another paper, were employed. Constrained optimum equal-ripple solutions to examples previously published by Young, Matthaei et al. and Riblet are presented. They demonstrate the considerable improvements made possible by the present formulation with regard to performance, reduction in number of sections, and physical size. The approach used in this paper should also find application in the design of broadband microwave matching or equalizing networks consisting of noncommensurate components and for which exact synthesis techniques may be unavailable.

Predetection signal-processing system

Abstract: A regenerative signal-processing system in which a multiplicity of incoming signals are combined prior to detection. By heterodyning each incoming signal with a common signal, difference frequency signals are generated. Each of these difference frequency signals controls a phase shift that is applied to the corresponding incoming signal and a resultant signal is formed and all resultant signals have the same phase and are combined to produce an output signal which is in the same frequency band as the incoming signal.

Intrusion detection apparatus having antijamming protection system

Abstract: This disclosure includes an intrusion detection system with a motion alarm which responds to a Doppler frequency signal. The motion-related Doppler frequency signals cover a predetermined frequency band and the alarm circuit is constructed to respond to all signals above a selected minimum amplitude within such band. A supervisory alarm is also provided which responds to a frequency higher than any frequency within such band. A jamming alarm circuit is provided which responds to a signal above a selected amplitude greater than the motion alarm selected amplitude and essentially independent of frequency.

Interference in a dense radio network

Abstract: Radio systems operating at frequencies above 10 GHz are limited to short hops by rain attenuation. A severe interference problem arises from the fact that in a given area many repeaters may mutually interfere through through the back and side lobe responses of their antennas. Introducing the concept of frequency spectrum conservation by maximizing the communication flow through an area, a model of a dense network of radio systems has been studied to determine the effect of antenna discrimination and bandwidth expanding modulation methods upon the total communication capacity in a given frequency band. We conclude that for efficient performance, bandwidth expansion is required; we also conclude that communication capacity can be considerably increased by improving the near side lobe performance of antennas.

Baseband frequency multiplexing scheme

Abstract: A binary data multiplexing system is disclosed wherein data from a binary source is applied to two encoders. One encoder operates to impart a self-clocking coding to the data and to thus cause the data to lie in a frequency band near the upper limits of the baseband frequency spectrum of the system. The second encoder operates to impart a low frequency coding to the data and to thus cause the data to lie in a frequency band near the lower limits of the baseband frequency spectrum of the system. In this way the data transmitted by the two encoders is made to lie in different and separated frequency bands.

Poly-panchromatic target identification

Abstract: In a radar or sonar system, a continuous spectrum of electromagnetic or compressional wave energy is transmitted and defines a wide band of frequencies. The receiver has one or more channels, the multiple channel arrangement defining subbands of the transmitted frequency band which are separately detected so that an identification signal is derived from each channel respectively. Each identification signal represents the response of the target to that particular frequency subband, such signals being combined as desired to provide a suitable readout. For three information signal output logic, a color cathode-ray tube provides an effective display by controlling each color input thereof in accordance with a corresponding one of the identification signals.

Frequency stabilization method and apparatus for parametric amplifiers and oscillators

Abstract: A coherent radiation beam passes in series through a pair of nonlinear elements separated by a modifying element, the nonlinear elements are reversed with respect to each other so that the effect of the beam in passing through the first is cancelled or nullified by the second. The modifying element serves to absorb and shift the phase of a selected frequency band such that cancellation of that band by the second element is prevented and selective amplification of the modified frequency band is achieved.

Transmission system for the transmission of information in a prescribed frequency band

Abstract: A transmission system where at the transmitter a source of information pulses is mixed with frequency modulated pseudorandom pulses, which can serve as synchronization, address signals, etc. At the receiver, the pseudorandom signals are frequency demodulated and used to synchronize a local pulse generator. Then they are frequency modulated and subtracted from the received signal.

Flight control disabling system

Abstract: A flight control disabling system operates by measuring the amplitude and frequency of control signals in the various flight control channels of the system. If in any channel there develops an oscillatory control signal exceeding a certain amplitude and lying within a predetermined frequency band, then either that channel alone or the entire flight control system is disabled.

Airborne pulse doppler radar system

Abstract: An airborne pulse doppler radar system whose sidelobe clutter amplitude is minimized by providing an antenna whose main beam subtends a small angle and whose radiated energy is concentrated in the main beam and the first few sidelobes and by providing a main beam band rejection filter whose rejection band is closely matched to the antenna main beam clutter frequency band

Improved speech articulation frequency modulation communication system

Abstract: The present invention provides a frequency modulation communication system wherein there is disposed in the transmitting side a first filter capable of furnishing transmission signals with such frequency characteristics of the voiced and unvoiced speech signal components as to allow information to be transmitted at the maximum rate possible with said transmission signals as well as with the transmission channel used and in the receiving side a second filter capable of bringing the frequency characteristics of signals received and frequency demodulated there back to the original state when said received signals were initially transmitted, thereby enabling the articulation of transmission signals to be improved with the said transmission channel, or enabling the same articulation of transmission signals to be maintained with a compressed frequency band width of the transmission channel and the prescribed frequency bandwidth to be compressed without any inconvenience.

A Phase-Locked AM Radio Receiver

Abstract: The problems in the microminiaturization of frequency selective circuits have shown the lack of adaptability of the presently used superheterodyne system, particularly in the lower frequency band, to the integrated radio receiver. By using phase-lock technique, the incoming signal can be converted to baseband directly, eliminating the need for intermediate frequency tuned circuits. A preliminary study has been made of the feasibility and the practicality of using phase-lock technique in the consumer AM Tadio receiver. A two-channel, phase-locked receiver is discussed in this paper. It is shown that this system offers not only the advantages of microminiaturization, but in many aspects, better performance as well.

Supervisory system for unattended repeaters

Abstract: A supervisory system for intermediate repeaters enables the gain of a repeater to be determined from either terminal station, and the noise produced by a repeater to be measured from one station without interrupting service. To test for gain, terminal station A(B) transmits a test signal lying in a 1st(2nd) frequency band not used for traffic. At the repeater this signal is converted by a modulator into a signal lying in a 2nd(1st) frequency band, this signal being returned to the A(B) terminal. The repeaters are identified by the frequency of a crystal filter included in the path of the test signals. The circuit can be used with single or double amplifier repeaters.

A Semi-Automatic Method for the Precision Measurement of Microwave Impedance

Abstract: A system is described for the measurement of the magnitude and phase of the reflection coefficient over wide frequency bands. The method consists of recording the voltage at several points along the standing-wave pattern in a coaxial line. A fixed probe is used and the distance between the probe and the load is altered by successively inserting several lengths of precision coaxial line. Knowing these lengths and the frequency of the signal, a curve representing the standing-wave pattern is fitted to the experimental points by means of a computer program performing a least-squares minimization. To cover a given frequency band, the frequency is changed in discrete steps and the corresponding probe voltage recorded automatically. The measured impedance is referred directly to the characteristic impedance of air-dielectric coaxial lines.

Frequency discriminator circuit having a narrow detection band

Abstract: A frequency discriminator circuit comprising means for providing a signal of which the phase is varied with the frequency of an input signal, means for generating two signals by the use of vectorial sums of said signal having the phase thereof varied and said input signal, and means for comparing the amplitude of each of said two vectorial signals and that of a reference signal which is proportional to the amplitude of said input signal and detecting that one of said two signals which has a greater amplitude, wherein the demodulation and frequency detection of an FM signal having a small frequency deviation as compared with the center frequency are limited so as to be effected only in the required frequency band, thus preventing noise disturbance outside the required band from occurring in the output.

Frequency modulation communication system

Abstract: The frequency modulation communication system modifies the frequency spectrum of transmission signals in transmission and reception so as to allow them to have desired characteristics, equivalently improves the signal-to-noise ratio (S/N ratio) and consequently improves the articulation of signals particularly associated with speech, thereby enabling a prescribed frequency band to be prominently compressed. For modification of the frequency spectrum, there are used means for inverting frequency spectra and means for rearranging or interchanging them.

Varactor controlled afc circuit for wide band tuner

Abstract: An AFC control circuit for an oscillator that is tunable over a wide frequency band produces a relatively constant frequency change or ''''pull-in'''' range at any frequency value within the band. The control circuit is connected across the main capacitance of the oscillator''s resonant circuit and is comprised of a varactor and a parallel inductance that define a reference resonant frequency lower than any frequency value within the band. The control circuit exhibits an effective capacity at all frequencies of interest and the varactor provides a change in such effective capacity which is related to operating frequency in a manner to achieve the uniform ''''pull-in'''' characteristic.

Signal-seeking radio receiver

Abstract: A superheterodyne radio receiver is provided for receiving RF signals over a reception frequency spectrum. The radio receiver includes a signal-seeking tuner having a drive mechanism for defining the reception frequency of the radio receiver as a function of the movement of the drive mechanism. The tuner is responsive to a start signal to initiate movement of the drive mechanism to vary the reception frequency of the radio receiver over the reception frequency band. Further, the tuner is responsive to a stop signal to terminate movement of the drive mechanism after the drive mechanism has coasted to a stop over a stopping-frequency range. A control circuit includes a transformer having a primary tuned circuit and a secondary tuned circuit each exhibiting a slightly different resonant frequency. A limiter circuit combines with the control circuit to provide frequency response curves for the IF signal of the radio receiver which are compressed with respect to overall magnitude and skewed with respect to peak frequency. As a result, an IF control signal is developed having an amplitude which exceeds a trigger level only when the nominal magnitude of the received RF signal exceeds a minimum reception level, and only when the reception frequency of the radio receiver differs from the carrier frequency of the received RF signal by an amount approximately equal to the stopping frequency range of the tuner drive mechanism. A stop signal is applied to the tuner when the amplitude of the IF signal exceeds the trigger level so that the drive mechanism coasts to a stop at a frequency approximately equal to the carrier frequency of the next received RF signal having a nominal magnitude in excess of the minimum reception level.

The use of amplitrons as microwave amplifiers in high power radar systems with frequency agility

Abstract: There are two important problems that arise in the use of amplitrons, as broadband microwave amplifiers in high power radar systems with frequency agility. The first one is to modify the conventional high vacuum tube modulator to obtain proper operation with good efficiency in case of very high power levels. The second one is to modify the modulator circuit by increasing its output impodance and thus limiting the poak current variations in the transmitted frequency band. In this paper analyses are made of both these problems, some practical results are given, and the implication in actual transmitter design is examined.