Showing papers on "Frequency band published in 1973"

A wide-band square-waveguide array polarizer

Abstract: A stepped-septum polarizer has been designed that is capable of at least 26 dB of isolation over a 20 percent frequency band. The three-port device may be used to excite high purity left or right circular, as well as tilted linear polarizations in a phased array of square waveguides.

Control of doppler shift compensation in the greater horseshoe bat, Rhinolophus ferrumequinum

Abstract: FlyingRhinolophus ferrumequinum lower the frequency of the constant frequency part (f A ) of the emitted sounds in order to compensate for Doppler shifts caused by the flight speed. The echo frequency (f E ) is kept constant within a frequency band of about 200 Hz, the center frequency of which is about 150 Hz above the average or resting frequency (f R ) emitted by roosting bats shortly before take off. For the compensation they use a feedback control system in which the emission frequency is changed to hold the echo frequency at a criterion value. This feedback system was demonstrated by experiments with bats flying in an experimental wind tunnel and in a He-O2-micture. In the wind tunnelRhinolophus lowers the emission frequency in order to compensate for Doppler shifts which are caused by the ground speed flown by the bat. In the He-O2-mixtureRhinolophus compensates for Doppler shifts which correspond to the different sound speeds in the gas mixture.

Psychophysiological effects of extremely low frequency electromagnetic fields: a review.

Abstract: Extremely low frequency (ELF) electromagnetic field-waves, defined in this paper as occupying the frequency band of .01 to 100 Hz, are associated with geomagnetic disturbances, weather perturbation...

Sonobuoy receiver system, floating coupler

Abstract: A modulation-demodulation floating coupler for use in a Sonobuoy Receiver to perform the function of an isolation transformer operating over a wide frequency band with very little phase shift is disclosed. The coupler is responsive to a high frequency composite input signal having a carrier portion on which is modulated a baseband information portion which is to be coupled and includes a transformer for coupling the composite signal to a pair of demodulators, the first of which provides an output with no ground reference, and the second demodulator produces a local feedback signal for gain and distortion control.

Stereophonic signal reproducing apparatus

Abstract: In a stereophonic signal reproducing apparatus, there are provided left and right loudspeaker systems for reproducing sounds in response to oppositely phased difference signals (L-R) and (R-L) that are supplied thereto, a central loudspeaker system disposed between the left and right loudspeaker systems for reproducing sounds in response to a sum signal (L+R) supplied thereto, and a frequency characteristic compensating circuit operable upon the oppositely phased difference signals to vary the frequency response of a signal reproduced from the difference signals such that the reproduced signal strength is relatively high in a low frequency band but relatively low in a high frequency band as compared to the frequency dependent signal strength of the sum signal (L+R). The stereophonic signal reproducing apparatus further has an auxiliary output terminal to which a sound reproducing device of the headphone-type is connected and means for terminating the variation in the frequency response of the reproduced signal by the frequency characteristic compensating circuit when the headphone is connected to the auxiliary output terminal.

Resonance control in interdigital capacitors useful as dc breaks in diode oscillator circuits

Abstract: A modified stripline interdigital capacitor has slots coupled into the capacitor gap. These slots provide reactive loading to the slot transmission line formed by the gap. They are positioned and dimensioned to shift the frequency of the slot line resonance so that it is out of a selected frequency band without affecting the capacitance of the structure. This interdigital structure may be used in diode oscillator circuits to provide a dc block for isolating the input and output from the diode bias.

Method of recording a video signal

Abstract: Method of recording a video signal, in particular a colour video signal, on a record carrier, in which method a combined signal is produced which contains a carrier which is modulated in frequency by the luminance information, and a subcarrier which lies below the frequency band of this modulated carrier and is modulated, for example, by the colour information. The zero crossings of the ascending and descending edges of the modulated carrier are shifted in opposite dependence upon the modulated subcarrier and recorded on the record carrier as information-containing quantities.

Satellite-Aircraft Multipath and Ranging Experiment Results at L Band

Abstract: Results of a flight test program involving a KC-135 jet airplane, the synchronous ATS-5 L -band satellite, and a ground station are presented. Tests included over-ocean multipath measurements and one-way tone ranging within the 1545-1655 MHz frequency band. Amplitude characteristics, polarization, power spectral density, and selective fading properties were measured for sea-reflected and composite signal channels. CW tone-ranging performance was determined in both the thermal noise and multipath environments. Comparison of experimental results with theoretical expectation is given.

Masking of auditory responses in the medulla oblongata of goldfish.

Abstract: 1. The nervous activity of single auditory neurones in goldfish brain have been measured. 2. Four types of acoustic stimuli were used, (1) pure tones, (2) noise of one-third octave band width, (3) noise of one-octave band width with centre frequency equal to the pure tone, and (4) white noise. 3. Except for white noise, these stimuli produced the same response to equal sound pressures. The white noise response was less, presumably because the frequency range covered by a single neurone is far narrower than the range of white noise. 4. The conclusion has been reached that for low-frequency acoustic signals, the acoustic power over a frequency band of one to two octaves is integrated by the nervous system. 5. The masking effect of background noise on the acoustic threshold of single units to pure tones is strongest when the noise band has the same centre frequency as the test tone. In this case the tone threshold increases linearly with the background noise level. 6. When the noise band was centred at a different frequency from the tone, the masking effect decreased at a rate of 20-22 dB/octave for the first one-third octave for a tone frequency of 250 Hz. For a tone of 500 Hz the masking effect of lower frequencies was stronger and was reduced by only some 9 dB/octave for the first one-third octave.

The performance of transistor fed monopoles in active antennas

Abstract: The performance of radiating elements in the form of monopoles and driven by transistors is examined theoretically and experimentally. A single element comprising a printed monopole over a ground plane and fed at its terminals by a microwave transistor is shown to have superior frequency characteristics compared to the passive element. Using a two-element array configuration, it is verified that the mutual impedance values are suppressed. The improved individual characteristics of the active elements together with their mutual behavior combine to produce a significantly improved frequency performance of the array. The results presented suggest that the transistorized array principle offers a means both of maintaining directivity of a transmitter, and discriminating against interfering sources by a receiver, over a greater frequency band.

Frequency band converter

Abstract: A frequency band converter wherein a signal whose frequency band is to be converted is written in a random access memory at a predetermined cycle while the contents of the random access memory are read out sequentially at a cycle different from the writing cycle thereby to obtain a frequency band converted output signal.

Chrominance signal correction

Abstract: In a video disc player, a recorded composite signal, recovered during disc playback, includes a chrominance signal component buried in the midband of the accompanying luminance signal component. The player includes video processing circuits converting the recovered signal to an output composite signal in which the chrominance signal component occupies a higher frequency band, and employing the step of heterodyning the recovered chrominance signal with oscillations at a nominal frequency of fs + fs'' (where fs is the color subcarrier frequency of the output, and fs'' is the buried color subcarrier frequency of the disc signal). To stabilize the output chrominance signal component against spurious frequency variations accompanying disc playback, a phase locked loop (PLL) system is established to cause the fs + fs'' oscillations to track the disc frequency variations. The PLL system employs a voltage controlled oscillator (VCO) operating at a nominal frequency of fs + fs'', and responding to the output of a phase detector, comparing the synchronizing burst component of the output chrominance signal with the highly stable output of a reference oscillator operating at fs. The recorded synchronizing burst component includes bursts of conventional short duration following each horizontal sync pulse but additionally includes an elongated burst component (of the same subcarrier frequency and phase) occupying a line interval during the ''''backporch'''' portion of the vertical blanking interval. The PLL system phase detector is supplied with both short and elongated burst components through use of appropriate line rate and field rate gating of the output chrominance signal. Presence of elongated burst component in the phase detector input substantially precludes ''''sidelock'''' condition (i.e., PLL system locking to a sideband component of the color synchronizing waveform under turn-on conditions when turntable speed is incorrect, and maintaining such a locked state as speed is corrected).

Frequency shift keying system and method

Abstract: A frequency shift keying method which comprises the steps of transmitting N signals having different shift patterns which correspond to N code elements and whose frequency is varied in the entire allocated frequency band during one clock period, comparing N heterodyne detector outputs provided by N local signals for receiving, having each frequency shift pattern synchronized to N transmitting signals, each of said local signals having a constant frequency difference from the transmitting signals, and detecting the heterodyne detector circuit having the maximum output whereby the transmitted code element is detected and reproduced.

Diplexing coupler for microwave system

Abstract: A coupler is described for coupling two microwave transmitters or receivers in one frequency band and two microwave receivers or transmitters in a second frequency band to a common central wave guide. The device provides high isolation between the four ports. Energy in a first band of frequencies is coupled to feed wave guides which are dimensioned to transmit this first band of frequencies. These feed wave guides are arranged to handle a pair of separate channels for the first band of frequencies, the signals in one of the channels having the same frequencies but a polarization which is orthogonal to that of the signals of the other channel. A pair of channels in the second band of frequencies, the signals in one channel having the same frequencies but a polarization orthogonal to that in the other channel, may be fed directly to the central wave guide. A branch wave guide is interposed between each of the feed wave guides and the central wave guide for coupling the energy in the first band of frequencies to the central waveguide, the branch wave guides being dimensioned to operate as a cutoff filter at the second band of frequencies (thus preventing such signals from entering the feed wave guides) and a high pass filter at the first band of frequencies.

A traveling-wave maser system for radio astronomy

Abstract: The design of a traveling-wave maser (TWM) for radio astronomy is discussed with particular reference to the Onsala system, which at present includes eight masers covering most of the frequency range 1-8 GHz (the frequency range in which the telescope is useful). Data are presented on the maser crystals iron- and chromium-doped rutile. A short discussion of different types of slow-wave structures (SWS's) used as maser interaction circuits, and some design criteria are given. We briefly consider the design of the ferrimagnetic isolator. A new method for rapidly retuning the maser to within a frequency band of the order of 100 MHz is introduced. The cryogenic system and the low-noise front-end waveguide are discussed. Also some general conclusions about the TWM bandwidth and a short survey of masers for frequencies above 10 GHz are given. Finally, we discuss which types of radio-astronomical research programs could most benefit from these extremely low-noise amplifiers.

Spectrum analyzer establishing a nonlinear frequency distribution of power-density spectra

Abstract: Precalculated samples of a power-density spectrum, taken at equispaced frequencies, are converted into modified samples with a nonlinear (e.g. logarithmic) distribution by being selectively weighted with the aid of several groups of coefficients defining a series of overlapping windows of mutually different widths. The system determines the weighting coefficient whose position in the frequency band of any window is closest to that of a precalculated sample appearing within that window; for each window, any sample appearing therein is multiplied by its closest coefficient and the sum of the resulting products is then divided by a factor proportional to the width of the window.

Selectively damped travelling wave tube

Abstract: Selectively damped travelling wave tubes having particularly periodically alternating magnetic field for guiding the electron beam comprise a delay line consisting of cells which are separated from each other by partitions and which are positioned one behind the other in the direction of beam travel. At least one resonator chamber is provided with damping material and coupled to at least one of the cells, the resonant frequency of the resonator chamber being at least almost equivalent to a predetermined interference frequency and each of the chamber resonators formed by a recess in a partition and its resonant frequency having the most energetic oscillation corresponding at least approximately to the frequency of an interference mode which is above the operational frequency band.

Multiple-beam antenna for domestic communication satellites

Abstract: This communication describes the design method of and experimental results obtained from a new multiple-beam antenna for domestic communication satellites. A seven-beam model antenna 1.98 m in diameter has been fabricated and evaluated in the 50-GHz frequency band, and the measurement data are reported here.

In-Band Generation of Synchronous Linear Data Signals

Abstract: In-band generation of synchronous linear data signals eliminates the need for preliminary generation of a baseband signal and sharp cutoff filtering. However, the ratio of carrier frequency to pulsing rate must, in general, be an integer if the signal is to be produced by successive pulsing of a single fixed filter. As a consequence, a singlesideband signal of bandwidth W and transmission rate 2W must occupy the frequency band [ 2NW,(2N +1)W ], N an integer, when it is generated from a single fixed filter. A partial-response signal satisfying this condition is described in this paper. A further analysis demonstrates that a finite number of fixed filters can be used to produce a pulse train in any band where the ratio of carrier frequency to pulsing rate is a rational number. Since this relaxed condition allows any transmission band to be approximated to an arbitrary degree of accuracy, frequency translation can be avoided. A single transversal filter with periodically varied tap weights is shown to be a practical realization.

Multiple frequency band frequency synthesizer

Abstract: There is disclosed herein a dual frequency band frequency synthesizer employing a single phase locked loop to control the frequency of the output signal of a voltage controlled oscillator so as to provide signals having a selected frequency in a selected one of the two frequency bands with the frequency of the signals in each of the two frequency bands having different incremental frequency steps. The phase locked loop includes therein a programmable binary divider having a different range of division factors for each of the two frequency bands with the output of the programmable divider being coupled directly to the phase detector of the phase locked loop when the lower frequency band is selected and through a modulo-6 binary counter when the higher frequency bands is selected. The programmable binary divider is programmed by frequency setting switches which produces 9's complement binary coded output for each of the selected decimal values. The coded decimal values of each of the frequency selecting switches are employed directly or through a decoding circuit to select the appropriate one of the two frequency bands, to program the programmable binary diver to the proper division factor for the frequency selected by the frequency setting switches and to bypass or incorporate the modulo-6 counter. The decoding circuit includes binary adders coupled to each of the switches intermediate the most significant switch and the least significant switch so as to add in digital form a first given constant value to the digital output of the switches when operating in the lower of the frequency bands and a second constant value in digital form when operating in the higher of the frequency bands so as to provide the proper division factor for the programmable binary divider for the frequency selected by the frequency setting switches. An automatic level control arrangement is also incorporated in the phase locked loop responding to the output signal in each frequency band to maintain a constant amplitude of output signal in each of the frequency bands.

A New Slot Line Broadband Isolator

Abstract: The present paper is devoted to a study of displacement effect on a slot line structure. shown a broad frequency band of operation. An described. non reciprocal devices using a field First experimental results have isolator and a 4-port circulator are It is well known that the dominant mode on a slot line exhibits regions where the magnetic field is elliptically polarized, both in the substrate and in the air outside the substrate. It is possible to turn to good account this particularity for the design of non reciprocal microwave components, such as isolators, using a resonance effect. However, such a device does not offer a broad frequency band of operation. Other experiments achieved on various geometries of slot lines on a ferrimagnetic substrate have shown that it is possible to obtain a non reciprocal behaviour on a broad frequency band and this characteristic allows us to distinguish this mode of operation from the resonant one. To obtain this effect, a suitable choice of the slot line and substrate geometry and ferrimagnetic material is necessary. A field displacement effect then appears on a broad band (more than an octave). The direct wave is travelling along the slot line while the reverse one is travelling on the opposite side of the substrate. It is now possible to absorbe this reverse wave by the means of a lossy dielectric material or a ferrite used in a lossy region of polarization (figure 1).

Wideband hybrid system

Abstract: An input diplexer separates wide frequency range signals by frequency to provide, at a plurality of outputs, signals within different narrow frequency bands. A plurality of quadrature hybrids are adapted so that each hybrid achieves equal power division and 90* relative phase shift with low distortion over one of the narrow frequency bands. A hybrid is coupled to each output of the input diplexer. Output diplexers are coupled to the two outputs of each of the hybrids to combine the power divided narrow frequency band signals into two wide frequency band signals of substantially equal power and of 90* differential phase.

Radio receiving aerial for motor vehicles - has single lead for taking off amplitude and very high frequency signals

Abstract: The application is to glass mounted aerials which may be included in windows or windscreens, having elements for AM and VHF signals. To match the two signals for transmission through a single aerial lead a buffer amplifier is inserted into the VHF lead before the commoning point. The screen of the common aerial lead is attached to the metallic frame of the window. The frequency range of the buffer amplifier must correspond to the frequency band of the VHF transmission. The aerial gives very little reduction in transparency of the glass.

Radar fuzing system

Abstract: A frequency modulated continuous wave radar signal is transmitted to a tat and the signal reflected from the target is compared with a sample of the continuous wave transmitter to produce a difference frequency signal. The difference frequency signal is band-pass amplified, wide-band limited, and processed by two frequency discriminators displaced from each other in the frequency domain, but both within the frequency band of the limiter and band pass amplifier. Detectors, integrators, and thresholding circuits determine, with suitable false alarm rates, in which half of which discriminator the difference frequency signal is concentrated.

Binary and Quaternary PSK Radio Systems in a Multiple-Interference Environment

Abstract: The planning of a digital radio network requires an evaluation of the effect of quite a large number of interfering sources. These in turn are dependent upon many parameters, such as the network structure, channel arrangement, antenna patterns, and so on. This paper presents a performance analysis of a digital radio-relay system during fading periods. The possibility of attaining a required fading margin is analyzed when many co-channel and interchannel interferences are simultaneously present, both for long-haul and shorthaul radio relay systems. A comparison is presented between two possible techniques for the reusing of the same frequency band in each hop, by taking advantage of the cross-polarization discrimination (XPD). The reduction of the XPD expected during fading periods is also taken into account. Binary and quaternary coherent PSK modulations are considered, with realizable filters (of the Butterworth type), both at the transmitter and at the receiver. The error probability calculations were performed with a combined analytical and computer simulation approach. The results seem to indicate the feasibility of the frequency reuse technique.

A Nondegenerate Millimeter Wave Parametric Amplifier with a Solid-State Pump Source

Abstract: A state-of-the-art nondegenerate millimeter wave parametric amplifier that utilized a reliable solid-state pump source at 105 GHz has been successfully developed and tested in the 55 to 65 GHz frequency band. A gain of 14 dB with a 1 -dB bandwidth of 670 MHz has been obtained. The measured single-sideband noise factor of the paramp averaged 5.9 dB across the operating passband.

Parametric Acoustic Arrays

Abstract: Parametric acoustic array performance has been demonstrated with several different transducers. Three‐inch‐diameter transducers with primary frequencies between 250 and 300 kHz have produced good parametric acoustic beams at 10, 20, and 40 kHz difference frequencies with nearly constant beamwidth across this frequency band. A parametric acoustic array operating at 20‐kHz difference frequency was compared to a 100‐kHz conventional transducer for bottom profiling capability in Lake Washington. Echograms were obtained demonstrating the capability of the lower frequency beam to produce subbottom, as well as bottom returns.

Multiplexer-demultiplexer for microwave antennas

Abstract: The multiplexer-demultiplexer operates in the 3.6 to 4.2, 5.9 to 6.4 and 6.4 to 7.1 kmc frequency bands. For demultiplexing, for example, the system operates as follows: Two serially arranged directional couplers respectively deliver the vertically-polarized signals of the first frequency band and the horizontally-polarized signals of the first frequency band to two outputs of the system, and the remainder of the signals received from the antenna to a polarizer. The latter feeds two waveguides with respective stubs and matching networks, forming the first branches of two Y-junctions; each one of the other branches of these Y-junctions feeds a filter. The four corresponding filters, whose outputs form other outputs of the system, respectively deliver the horizontally-polarized signals in the 6.2 to 6.4 kmc and 6.7 to 7.1 kmc frequency sub-ranges and the vertically-polarized signals in the 5.9 to 6.2 kmc and 6.4 to 6.7 kmc frequency sub-ranges.

Frequency simulator for ew training device

Abstract: Frequency simulator apparatus for use with passive, electronic warfare (EW) training devices to render more effective and realistic signal recognition training of operators. A video switching network is connected between the output of a video tape recorder and the video circuits of a passive EW receiver set. Prerecorded radar video signals will not be displayed on the receiver set until the operator selects at the receiver set the proper frequency band and tunes the receiver to the proper frequency within that band to thereby actuate the switching network with a voltage indicating that the proper band has been selected and another voltage indicating that the proper frequency has been tuned to.