Showing papers on "Frequency band published in 1974"

Multiple band scanning radio

Abstract: To scan channels in a plurality of bands using a single first mixer, an FET transistor in an adaptive first mixer of the scanning radio, in response to a signal from a counter in the scanning local oscillator representing the frequency band of the channel being scanned, has: (1) its gate electrode connected to the output of a selected RF amplifier of a plurality of RF amplifiers for different bands; and (2) its source electrode electrically connected to receive local oscillations through a selected one of a plurality of different impedance networks. These connections enable the adaptive first mixer to maintain sufficiently high conversion gain when receiving signals on channels in any one of a plurality of different frequency bands.

Method and apparatus for bi-directional communication via existing CATV system

Abstract: Existing CATV coaxial cable systems are found to present a transparent window, in both the upstream and downstream directions, to communications signals over a frequency band from 10-300KHz, whereby such signals follow the path of the 60Hz power signal throughout the system. Signals in this band do not interfere with the high frequency TV signals being transmitted, and are not subject to interference by such TV signals. This discovery is thus utilized to implement bi-directional communications between any two or more points linked by such a CATV system without requiring any substantial modifications or additions to the existing system components. A specific application utilizes such a communications link to remotely control non-duplication switching in the head or antenna end of a CATV system.

Loop fault locater

Abstract: Faults on a telephone cable pair are located by a frequencydomain detection system. The derivative, with respect to frequency, of the phase angle of the complex input impedance of the pair is measured periodically across a predetermined frequency band to produce a periodic time function. The power spectrum of this function is determined and the frequencies of the spectrum maxima are used to estimate the distances to all of the faults from the measurement point.

Three frequency band antenna

Abstract: Disclosed is an antenna for radiating wave energy signals in three frequency bands. Signals having frequencies in the first and third bands are radiated by a first radiator. Signals having frequencies in the second, intermediate frequency band are radiated by a second radiator. The impedance characteristics of the radiators are used to selectively couple signals from the input to the appropriate radiator.

Extremely Low Frequency (ELF) Ionospheric Radio Propagation Studies Using Natural Sources

Abstract: The purpose of this paper is to describe methods of studying the propagation of radio waves over the earth's surface in the extremely low frequency (ELF) frequency band (3 Hz-3 kHz) using natural (as distinct from "man-made") sources of radiation. Attention is focused on the characteristics of the radio wave field and on methods of analysis of acquired data in order to obtain information on propagation parameters of interest in Project Sanguine. Wave impedance measurements are identified as being of particular importance in these investigations.

Electric wave resonators

Abstract: In a resonant cavity which has multiple modes of resonance within a desired frequency band, certain undesired modes are selectively detuned out of this frequency band, leaving a single desired mode within this band. This is accomplished by the insertion of elongated conductive members into the cavity, so placed and oriented that they cause strong field distortion and detuning of the undesired modes, but cause little effect on the field pattern of the desired mode with little detuning. In the case of a cylindrical cavity operating in a TE011 mode, coupling can be accomplished through an end wall of the cavity substantially without mode interference effects, permitting more economical methods of construction. The principle has been applied to single cavity and multiple cavity resonators and wave filters.

Frequency selection and control

Abstract: An automatic oscillator frequency control is provided for operations such as employed in channel selection in radio and television receiver systems. A code is stored representative of a selected frequency band within which a selected channel is located. The frequency of an oscillator is varied monotonically from a reference frequency at one extremity of a selected frequency range successively to traverse a plurality of such frequency bands. A frequency marker is generated at the margin of each band and the markers are counted. The number of counted markers is compared with the stored code to generate a control state. In response to the control state, a pattern control causes it to dither between limits of the selected band until a signal is encountered at the selected frequency within the selected band. At that point, the oscillator is locked to the frequency of the received signal. In a preferred embodiment, the frequency markers are generated by use of an interferometer, preferably of the surface wave device type wherein a pair of sensor arrays are spaced to sense acoustic waves at the oscillator frequency and are mixed to produce voltage nulls at the margin of each of a plurality of frequency bands of uniform width. Three control loops are provided, an acquisition loop, a control loop and a tracking loop. The loops are asynchronous and provide for operation without imposition of critical time responses in the manual control thereof.

Record carrier for a television signal

Abstract: In a record carrier for the storage of a television signal in an optically readable track-shaped structure, the information is contained in the frequency and/or amplitude of an undulation of the tracks of constant trackwidth. Via a phase-reading mechanism an electric signal can be obtained which is substantially linear with the television signal to be written. When transferring a television signal via such a record carrier the electric signals need not be limited abruptly. As a result, no higher harmonics occur, and substantially no mixing products occur in the frequency band of the luminance information and in the frequency band(s) of other information, for example chrominance and sound information.

Multiband tuner control system

Abstract: A multiband tuner control system, particularly adapted for television receivers, utilizes, a three-band varactor VHF tuner. The bands include low and high band VHF signals and a third band of signals obtained from the UHF signals following a first conversion to a third VHF frequency band. This third band is selectively switched to the tuner under the control of channel selection switches. The channel selection switches also cause the conversion of UHF signals to the VHF band to be effected by mixing the UHF signals with a different fixed frequency local oscillator signal in the first converter for each different decade of channels of the UHF signal. The channel selection switches automatically cause this to happen and also select a proper tuning potentiometer associated with the selected UHF or VHF band directly in accordance with the two-digit channel number. The switching of the bands of the tuner is effected automatically by the channel selection switches, as is the switching between the VHF input signals and the converted UHF signals.

Rejection filter to remove TV channel 6 and FM radio interference

Abstract: A two terminal electronic filter network is provided for connection across TV antenna input terminals to reduce interference from noncommercial FM radio stations operating within a frequency band near the TV channel 6 frequency band. The two terminal electronic filter circuit which exhibits a rapid change of reactance for changes in frequency, and having a resonant frequency provides sufficient FM signal rejection without significant attenuation of any VHF channel by the provision of a highly reactive network tuned below the resonant frequency of the filter network as a whole.

A Matched-Load Type Thermoelectric Transducer for Power Measurements in the Millimeter-Wave Region

Abstract: As a power detector in the millimeter-wave region, a matched-load-type thermoelectric transducer is proposed. Experimental investigations have been carried out to obtain the design criteria of this device. The investigations have two aspects. One of them is macroscopic and related to the matching characteristics of the transducer. The other is microscopic and related to the sensitivity characteristics. The analysis of the temperature distribution on the power-sensing element is the main problem in the latter respect. Through these investigations, tentative design criteria have been obtained. Transducers manufactured on the basis of these criteria have shown excellent performance as practical millimeter-wave power detectors. Outstanding characteristics of this device are low VSWR and small deviations of the sensitivity in the entire waveguide frequency band. The stability of this device over long periods of use was also confirmed.

Radio communication transmitter

Abstract: A multi-channel radio communication system comprising a number of stations for the transmission of speech between the stations, each station transmitting not only the speech signal but also a special so-called busy signal located in a frequency band beyond the speech frequency band, which busy signal informs the remaining stations in the group of which are not occupied by a call to another station that the actual carrier frequency or channel is occupied and cannot be selected for a new connection. According to the invention the busy signal is automatically controlled in amplitude as a function of the instantaneous value of the speech signal and this in such a manner that the envelope of the combination of the speech signal and the busy signal is maintained substantially constant so that as a result of the normal interruptions in a conversation the busy signal will be automatically and repeatedly adjusted to full amplitude.

Superdirectivity with Appreciable Bandwidth in Arrays of Radiating Elements FED by Microwave Transistors

Abstract: The incorporation of transistors into the radiating elements of an array antenna leads to a suppression of the elemental mutual coupling effects in the feed network. Because of this suppressed interaction, it is possible to re-appraise the practical exploitation of Schelkunoff's principle that an arbitrarily high gain can be obtained from a given array size by suitably feeding the individual elements. A four-element end-fire superdirective array with a total length of 3?/8 and a theoretical beam width of 60° has been investigated. The computed radiation patterns of the passive array indicate the extreme sensitivity to changes in frequency consistent with the classical limitations of supergain arrays. An experimental active array is described which permits the superdirective performance to be maintained over an appreciable frequency band.

Multi-speed ramp for a varactor tuning system

Abstract: An electronic all channel television tuning system has a presettable counter for deriving the number of the receivable television channel by counting, on a continuing sample basis, the varactor diode tuner local oscillator frequency. The derived channel number is supplied as an input of a comparator which includes separate tens and units channel number comparison sections. A channel number selector supplies an encoded desired channel number to another input of the comparator and to a frequency band decoder which establishes appropriate preset information for the counter. The system local oscillator frequency is varied by a voltage ramp circuit having two pairs of matched current sources and sinks of different capacity for supplying current, through respective transmission gates, to charge or discharge a tuning capacitor at different rates. A difference in the tens section of the comparator activates the transmission gates for both the larger and smaller capacity source-sink pairs, producing the high ramp speed. After equality in the tens digits only one of the small capacity source-sink pair is activated, under control of the units section of the comparator, to produce the low ramp speed.

System and apparatus for electronic spectral analysis

Abstract: Frequency response of a signal path over which frequency-spaced signals are transmitted is analyzed by sweeping relatively narrow pass band tunable receiving means across the frequency band expected to be received at the location to be analyzed. Incoming signal to which the tunable receiving means is tuned at any instant is used to control the frequency of a voltage controlled oscillator. The frequency of oscillations produced by the oscillator has a known relationship to the amplitude of the instantaneously received signals, and these oscillations are transmitted to a frequency-to-amplitude converter at a measuring location. The converter produces an output signal that has an amplitude which is a function of the frequency of oscillations applied to it. A spectrum indicator at the measuring location is connected to the converter to produce a visual display of the amplitude of signals received at the location at which the characteristics of the transmission path are being analyzed.

A Quest for a Controllable ULF Wave Source

Abstract: Natural geomagnetic phenomena indicate that wave generation and amplification processes occur spontaneously in the magnetosphere and may be available under certain conditions to permit the frequency band near 1 Hz to be used for communications. An ionospheric duct provides low-loss propagation for waves in this band to distances of thousands of kilometers, and their large skin depth in seawater permits penetration to several hundred meters below the ocean surface. Several methods by which the generation of waves in this band might be possible are described. Methods involving the modulation of ionospheric conductivity include the injection of plasma clouds into the ionosphere and heating of the lower E region with powerful radio transmitters. Methods involving nonlinear processes in the magnetosphere include cold plasma injection and very low frequency (VLF)/ultralow frequency (ULF) three-wave interactions.

Broadband beacon antenna system

Abstract: Tactical radio navigation systems provide bearing information to an interrogating aircraft in response to pairs of interrogation pulses received at a beacon transponder, the system also provides distance measuring and identification information. To provide the required bearing information, pulses radiated from the central antenna array are modulated at a 15 Hz frequency and by 135 Hz frequency, by parasitic elements rotating around a stationary central array. Broadband operation of the system is provided by a distribution pattern of the 135 Hz parasitic elements mounted radially from the central antenna array on a dielectric disc. Nine groups of radially displaced 135 Hz elements are circumferentially arranged around the dielectric disc and each element of a group is tailored to a particular frequency band in the frequency spectrum allotted to radio navigation systems.

A wide-band digital magnetotelluric recording system *

Abstract: A six-channel wide-band digital system for magnetotelluric measurements is described The system is designed to operate in the frequency band 10-.0001 Hz. The recording is made on a 7 track tape in an IBM compatible 12 bit format. The amplitude and phase responses of the system and sample records are presented.

Television tuning system indicator

Abstract: An all channel television varactor diode tuning system has a presettable counter for deriving the number of the receivable television channel by counting pulses indicative of the tuner local oscillator frequency, which is varied by a voltage ramp circuit under the control of a comparator. The derived channel number is supplied to one input of the comparator, and a channel number selector supplies an encoded desired two digit channel number to the other comparator input and to a frequency band decoder. The band decoder supplies signals to establish appropriate preset counts for the counter in accordance with the frequency band. The channel number selector includes a keyboard coupled to a multi-location tens and units memory for encoding and storing desired channel numbers. The keyboard is also coupled to a function/number decoder which distinguishes between digits and controls the state of a flip/flop in decoder circuitry which subsequently controls a units and tens position display device. The flip/flop, through logic circuitry, enables display of a first digit entered at the keyboard in the tens display position while blanking the units position and enables both display positions only for completed two digit channel number entries.

Compression and expansion system using a subtraction circuit

Abstract: A compression and expansion system comprises: a first frequency characteristic changing circuit for increasing the level of the high frequency band component of an input signal and carrying out compression; first subtraction circuit for carrying out subtraction operation of an input signal to the first frequency characteristic changing circuit and the output signal thereof; first frequency characteristic control circuit for supplying a control signal to the first frequency characteristic changing circuit in accordance with the output of the first subtraction circuit; second frequency characteristic changing circuit supplied with the output signal of the first frequency characteristic changing circuit transmitted through a transmission system and operating to decrease the level of the high frequency band component of this output signal and to carry out expansion; second subtraction circuit for carrying out subtraction operation of an input signal to the second frequency characteristic changing circuit and the output signal thereof; and second frequency characteristic control circuit for supplying a control signal to the second frequency characteristic changing circuit in accordance with the output of the second subtraction circuit. The subtraction circuit produces as output a signal which is equivalently of high-pass filtering characteristic of which cut-off frequency varies in accordance with the level of the input signal.

Comments on “Finite element analysis of acoustically radiating structures with applications to sonar transducers” [R. R. Smith, J. T. Hunt, and D. Barach, J. Acoust. Soc. Am. 54, 1277–1288 (1973)]

Abstract: Transmitting voltage responses are calculated for several free‐flooded cylinder transducers. It is shown that redesigning a cylinder to have breathing and bending resonances that are close in frequency does not create a flat response over a much wider frequency band. A significant improvement can be made, but maxima and minima in the response that are associated with cavity resonances cannot be eliminated without degrading the reponse at other frequencies.

Delay time controller for use in a group-delay equalizer

Abstract: A delay circuit provides a flat delay versus frequency characteristic over a first band of frequencies by combining two delay equalizers having opposite signed and equal magnitude slopes of delay versus frequency over two different bands of frequencies. The first frequency band is translated to a second band which is applied to the first of two delay equalizers. The latter has a transfer characteristic which is a substantially constant slope of delay versus frequency for a band encompassing and much wider than said second band. The output of the latter element is translated back to the first frequency band. The first band, either prior to the initial frequency translation or subsequent to the second frequency translation, is applied to a second delay equalizer. The characteristic slopes of the two delay equalizers are of substantially equal magnitude but of opposite sign.

A Design Theory for Wide-Band Parametric Amplifiers

Abstract: A new exact design theory for a nondegenerate parametric amplifier with double-tuned signal circuit and single-tuned idler circuit is described. If the resistance of the signal circuit, which is neglected in previous papers, is considered, there exists a frequency band in which the amplifier gain is positive. In this paper the band characteristics of the gain are related to this frequency band. Slope parameters of the idler and signal circuits are normalized by the slope parameters which are associated with the diode itself. These normalized slope parameters are used to relate the actual circuit and gain-bandwidth characteristics. The slope parameter of the external signal resonator is related to the negative slope parameter of the diode, and bounds on this ratio are given over which stable amplification is possible. A design table which gives the coupling ratio and slope parameter of the external signal resonator is derived by computer calculation. Experiments were made at 19 GHz. Positive-gain bandwidth was around 4.0 GHz, and flat bandwidth at 10-dB gain was 2.4 GHz. The ratio of these bandwidths coincided with the theory.

Magnetic system for discriminating between vehicles and personnel based upon their characteristic frequency signatures

Abstract: An electronic system for the detection of moving objects, such as vehicles or personnel, is disclosed. The system detects the presence of vehicles and personnel by utilization of a characteristic frequency signature of each in a twin channel arrangement with each channel adapted to process signals within its respective frequency band. As vehicles may produce signals within the bandpass of both channels and personnel produce signals within the bandpass of only one channel the system is uniquely adapted to distinguish between the two types of moving objects.

Television tuning system with varactor malfunction detection

Abstract: An all channel television varactor diode tuning system has a presettable counter for deriving the number of the receivable television channel by counting pulses indicative of the tuner local oscillator frequency, which is varied by a voltage ramp circuit under the control of a comparator. The derived channel number is supplied to one input of the comparator, and a channel number selector supplies an encoded desired channel number to the other comparator input and to a frequency band decoder. The band decoder supplies signals to establish appropriate preset counts for the counter in accordance with the frequency band. Malfunction detection circuitry for detecting an improper number of pulses for the presettable counter, when in the low VHF frequency bands, is coupled to the channel number selector and connected through the comparator to force the tuning voltage circuit to drive the varactor in a direction opposite to that indicated by the comparator. This is done by monitoring the tens digit in the counter for occurrence of an 8 or 9.

Surface Wave on a Ferrite Magnetized Perpendicular the Interface (Short Papers)

Abstract: A semi-infinite ferrite magnetized perpendicular to the interface is found to support a nonmagnetostatic surface wave. The wave exists within a finite wavelength band and a finite frequency band. Since the wavelength is typically of the order of 1 cm, large samples of polycrystalline ferrite material may be used for the experiments.

Band decoder for all-channel digital tuning system

Abstract: An electronic all-channel television tuning system has a channel number computer including a presettable counter for deriving the number of the receivable television channel by counting, on a continuing sample basis, the tuner local oscillator frequency. The local oscillator frequency is varied by a voltage ramp circuit under the control of a comparator. The derived channel number is supplied to one input of the comparator, and a channel number selector supplies an encoded desired channel number both to the other comparator input and to a decoder for determining the appropriate frequency band in which the signal corresponding to the desired channel number lies. The decoder develops and supplies signals to establish for the presettable counter appropriate preset information corresponding to each of the four disconnected FCC frequency bands.

Swept comb method of jamming

Abstract: An improved countermeasure technique for providing jamming signals againstobing radar, especially COSRO (conical scan on receive only) radar. A power spectrum (or comb) is generated having specific spectral line separation over a frequency band of the expected range of scan frequencues. The line spectrum, preferably having a flat topped envelope is then swept as a unit so that all frequencies with in a range of expected scan frequencies are traversed at least once by a spectral line. The swept comb is used to modulate a repeater pulse train transmitting to a lobing radar. The sweep of the comb causes at least one spectral line to beat with the scan frequency of the radar resulting in antenna oscillation and sidelobe lockup by deception of the angle-tracking circuits of the radar.

Device for the facilitation and simplification of the adjustment of resonators of an answering device in a microwave railroad vehicle identification system

Abstract: A device for the facilitation and simplification of the adjustment of resonators of an answering device coupled to a high frequency line, for a microwave transmission system for railroad vehicles or information assigned to certain points with several digits employs a separate frequency range with frequencies provided for the characterization of an alphanumeric symbol and periodic switching through the transmission frequency band which transmits an interrogation signal from an interrogation device and receives selectively frequency modulated signals by the resonators of the answering device. Successive frequency ranges of the transmission frequency band are assigned in a sequence differing from the digit sequence of the information to be transmitted. The resonators are optimally coupled with respect to oscillations to the electromagnetic field of the high frequency line and the interrogation device includes, in a receiving branch thereof, a digit sorter which arranges the signals created by the resonators into respective digit stores which are arranged according to the digit sequence.

Narrowing of the emission spectrum of ruby laser by inhomogeneous pumping

Abstract: A conventional ruby laser without mode selection emits spikes with frequencies distributed over a range of about 2×1010 Hz. By a suitable pump light distribution the frequency band of the emission was confined to about 0.3×1010 Hz. This effect can be explained by the model of spatial hole burning.