Showing papers on "Frequency band published in 1984"

Stimulated electromagnetic emission: A new technique to study the parametric decay instability in the ionosphere

Abstract: A powerful HF wave, transmitted in the O mode with a frequency not exceeding the critical F region frequency, gives rise to secondary electromagnetic radiation, filling a frequency band of several 10 kHz around the frequency of the primary wave. The spectrum of these secondary waves is richly structured. The systematically occurring spectral features are identified and described. The majority of these features can be understood by scatter processes involving Langmuir waves and low-frequency density perturbations excited by the parametric decay instability. Other features, including a broad spectral maximum at 20 to 40 kHz on the upshifted side, are not as yet fully understood.

Dual mode feed horn or horn antenna for two or more frequency bands

Abstract: A microwave feed horn or horn antenna (11,12) for at least two frequency bands comprises a conical waveguide section (42) whose aperture at the large end has an inside diameter (D1) approximately equal to one wavelength in the lower frequency band so as to produce substantially equal power patterns in the E and H planes in the lower frequency band. The slope (s) of the inside wall of said conical section (42) is selected to cancel the electric field at the aperture of the horn in the higher frequency band, thereby producing substantially equal power patterns in the E and H planes in the higher frequency band. A pair of straight waveguide sections (40,41) connects the opposite ends of the conical waveguide section (42).

Directional coupler for separation of signals in two frequency bands while preserving their polarization characteristics

Abstract: The coupler comprises a principal corrugated waveguide (10) and four identical secondary waveguides (11) regularly disposed on the perimeter of the principal waveguide and in such a way that the five axis are parallel. Coupling units (12) allow transfer of energy between principal and secondary waveguides. Due to reactance boundary conditions and size, only the HE11 mode in the higher frequency band and the EH11 mode in the lower frequency band can propagate in the principal waveguide. This perserves the polarization characteristics. Directional filtering is obtained by close agreement of phase constants in the different waveguides and 90o phase change between two successive coupling units in the higher frequency band, and evanescence or very low phase constant in the secondary waveguides in the low frequency band.

Full duplex frequency division multiplex communication system

Abstract: A full duplex frequency division multiplex communication system which comprises a number of transceivers constituting user stations which communicate with one another over a common channel, such as a wireless link or a two-direction coaxial cable, with each transceiver operating on a single fixed intermediate frequency for transmission and reception. The system includes a network frequency converter for shifting the transmission frequency band used by the transceivers into a different receiving frequency band which does not overlap the transmission frequency band. Single sideband modulation of the intermediate frequency carrier is used, and full duplex communication is achieved by using one of the sidebands of the intermediate frequency carrier for transmission, and the other sideband for reception. Each transceiver includes a programmable frequency synthesizer for channel selection, and upper and lower sideband filters, with one of the filters being used for transmission and the other for reception.

System for carrying out spread spectrum communication through an electric power line

Abstract: A communication system for carrying out communication between a plurality of stations through an electric power line operating in a commercial power frequency band. Spread spectrum modulation of an information signal, employing a pseudorandom code sequence is used at a transmitting station. Spread spectrum demodulation is carried out in a receiving station to reproduce the information signal. The modulated signal is spread over a wide frequency band different from the commercial frequency band. Each station may comprise both of a transmitter and a receiver, and may be specified by a an assigned destination address that also is transmitted. The destination station address may be indicated either by an address signal or by an additional pseudorandom code sequence peculiar to a destination station. Alternatively, polling operation is carried out through the electric power line by a polling station to select one of the stations. Preferably, another pseudorandom code sequence is superposed on the modulated signal so as to specify a synchronization signal and different from the pseudorandom code sequences conveying the information signal and/or the destination address.

Noise suppressor for electronic endoscope

Abstract: A noise suppressor is provided for an electronic endoscope which incorporates a diathermic cutter or an ultrasonic diagnosis system. The electronic endoscope utilizes a solid-state camera, and in order to prevent noises from being superimposed upon the signal fed to an image display, a transmission line which transmits a high frequency current to the diathermic cutter or a transmission line which transmits an ultrasonic signal to or receives an ultrasonic signal from an ultrasonic probe is shielded by a conductor member. In particular, for a transmission line which conveys the high frequency current, impedance regulating means is connected therewith in order to prevent the high frequency current from leaking through a distributed capacitance between the transmission line and the conductor member. Alternatively, a narrow bandpass filter may be provided which limits the frequency band of the high frequency current. A coaxial cable may be used in which both the transmission line and the conductor member are formed of conductive rubber.

Spectral estimates of seismic shear waves

Abstract: The scaling of seismic sources according to Brune (1970, 1971), with a stress drop of 100 bars, allows accurate prediction of average Fourier spectra of seismic shear waves in the far-field for the frequency band 1 to 10 Hz. Random vibration theory under the assumption of stationary response accurately predicts average linear-elastic response spectrum amplitudes in this same frequency band. These conclusions are reached through comparison of theoretical estimates with strong motion observations during a wide range of California earthquakes (local magnitudes 4.0 to 7.2, distances 9 to 130 km). Thus, these models are an accurate, physically based method of estimating high-frequency strong ground motion for a range of earthquake magnitudes and distances, and offer the advantage (over purely empirical methods) of a physical basis for extrapolating to predict ground motions for magnitudes and distances which are poorly documented with data.

Cold plasma waves

Abstract: 1 Elementary properties of a plasma- Plasma- Equations of drift motion- Isothermal atmosphere in equilibrium- Types of wave- Effect of collisions- The continuity equations- 2 Maxwell's equations- Equations in terms of current and charge densities- Equations in terms of electric moment per unit volume- The exponential wave function- The concept of a dispersion relation- Calculation of the dispersion relation (electric current method)- Calculation of the dispersion relation (electric moment method)- 3 Isotropic plasma- Mobility and conductivity of an isotropic plasma- Susceptibility and dielectric constant of a collisionless isotropic plasma- The plasma frequency- Refractive index of a collisionless isotropic plasma- Wave dispersion in a collisionless isotropic plasma- Effect of collisions in an isotropic plasma- Importance of ordered kinetic energy in a plasma- Poynting's theorem in a plasma- The energy significance of the complex dielectric constant of an isotropic plasma- 4 Alternating current in a magnetoplasma- Mobility tensor for a magnetoplasma- Conductivity tensor for a magnetoplasma- Low-frequency conduction properties of an infinite homogenous magnetoplasma- Low-frequency conduction properties of a slab of magnetoplasma- Effect of plasma scale on wave propagation- 5 General properties of phase propagation in a magnetoplasma- Susceptibility tensor for a magnetoplasma- Alternative expressions for the susceptibility tensor components in the absence of multiple ion species- Dispersion relation for a magnetoplasma- Elliptic polarization- Alternative derivation of the dispersion relation for a magnetoplasma- The radio and hydromagnetic approximations- Effect of collisions in a magnetoplasma- 6 General properties of group propagation in a magnetoplasma- Frequency and angular spectra- Velocity of a wave packet- Relation between phase and group propagation- Method for calculating group velocity in a magnetoplasma- Formulae for group velocity in a magnetoplasma- Beam radiation in a magnetoplasma- 7 Propagation of phase along the imposed magnetic field- Circular polarization- The dispersion relation for longitudinal propagation- Longitudinal Alfven waves- The violin-string approach to longitudinal Alfven waves- The hydromagnetic approximation for longitudinal propagation- The radio approximation for longitudinal propagation- The Eckersley approximation for longitudinal propagation- Comparison of approximations- Pass and stop bands of frequency for longitudinal propagation- Particle vibration for longitudinal propagation- Plasma motion in a longitudinal Alfven wave- Longitudinal propagation in low-density and high-density magnetoplasmas- Effect of collisions on longitudinal propagation- Effect of an additional ion species on longitudinal propagation- Pass and stop bands of ionization density for longitudinal propagation- 8 Energy flow and group velocity for longitudinal propagation- Electromagnetic energy density for longitudinal propagation- Kinetic energy density for longitudinal propagation- Energy flow and group velocity for longitudinal propagation- Energy in a longitudinal Alfven wave- Faraday rotation for longitudinal Alfven waves- A resonator for longitudinal Alfven waves- The mode of operation of a hydromagnetic violin-string- Freezing of the magnetic field in the plasma (longitudinal Alfven waves)- Energy in a longitudinal whistler wave in the band ?Mi ? ? ? ?Me- A resonator for longitudinal whistler waves in the band ?Mi ? ? ? ?Me- Freezing of the magnetic field in the electron gas (longitudinal whistler wave)- Solid-state plasmas- 9 Propagation of phase transverse to the imposed magnetic field- The O wave- The X wave- Superposition of the O and X waves- Pass and stop bands of frequency for transverse propagation- The hybrid resonant frequencies- Transverse propagation in a low-density magnetoplasma- Pass and stop bands of ionization density for transverse propagation- Effect of collisions on transverse propagation- 10 Elliptic polarization of the X wave for transverse propagation- The electric ellipse for transverse propagation of the X wave- Frequency dependence of the electric ellipse- Particle vibration for transverse propagation of the X wave- Plasma compressions and dilations for transverse propagation of the X wave- Non-reciprocity- 11 Energy behaviour of the X wave for transverse propagation- Electromagnetic energy density for transverse propagation of the X wave- Kinetic energy density for transverse propagation of the X wave- Energy flow and group velocity for transverse propagation of the X wave- A resonator for transverse Alfven waves- The mode of operation of a hydromagnetic organ-pipe- Freezing of the magnetic field in the plasma (transverse Alfven waves)- 12 Propagation at any angle to the imposed magnetic field- The zeros in the frequency dispersion curves- Nomenclature for the characteristic waves- The cross-connection phenomenon for frequency dispersion curves- Frequency dispersion curves for nearly transverse propagation- Frequency dispersion curves for nearly longitudinal propagation- The elliptic polarizations of the O and X waves at the plasma frequency- Effect of an additional ion species on cross-connection phenomena- The infinities in the frequency dispersion curves- Permitted regions for the frequency dispersion curves- The cross-connection phenomenon for ionization dispersion curves- Permitted regions for the ionization dispersion curves- Propagation into a magnetoplasma from free space- 13 The radio approximation- The radio approximation to the dispersion relation- Frequency dispersion curves in the radio band- Frequency dependence of elliptic polarization in the radio band- Frequency dependence of the direction of group propagation in the radio band- Variation in the angle of squint of a rotating broadside antenna in the radio band- Dependence of refractive index on ionization density in the radio band- Dependence of elliptic polarization on ionization density in the radio band- Dependence of the direction of group propagation on ionization density in the radio band- 14 The hydromagnetic approximation- The hydromagnetic approximation to the dispersion relation- Frequency dispersion curves in the hydromagnetic band- Effect of ionic collisions in the hydromagnetic band- The fit between the hydromagnetic and radio approximations- Frequency dependence of elliptic polarization in the hydromagnetic band- Frequency dependence of the tilts of the electronic and current ellipses in the hydromagnetic band- Frequency dependence of the direction of group propagation in the hydromagnetic band- Polar diagrams for group velocity in the hydromagnetic band- Dependence of refractive index on ionization density in the hydromagnetic band- Dependence of elliptic polarization on ionization density in the hydromagnetic band- Dependence of the direction of group propagation on ionization density in the hydromagnetic band- 15 The quasi-longitudinal and quasi-transverse approximations- The transition angle between the quasi-longitudinal and quasi-transverse approximations- The regions of validity for the first- order angular approximations- Importance of avoiding angular approximations that upset an infinity of a refractive index- The regions of validity for angular approximations of practical value- Accuracy of ?2n/??p2 using angular approximations- The quasi-transverse approximation when ? ? ?Mi- The quasi-longitudinal approximation when ? ? Max(?N,?Me)- The quasi-longitudinal approximation when ?Mi ? ? ?C2- Group propagation of the O wave in the pass band ? > ?N- Group propagation in the upper part of the whistler band [??1 ? > ??2- Radiation in the frequency band ?? > ? > ?N- Radiation in the frequency band ?N > ? > ?C1- Radiation in the frequency band ?Me > ? > ??1- Radiation in the frequency band ??1 > ? > ?Mi- Radiation in the frequency band ? < ?Mi- Frequency dependence of radiation resistance- The relation between beaming and guidance in a homogeneous magnetoplasma- The relation between beaming and guidance for the whistler wave when ??1 < ? ? Min (?N, ?Me)- The relation between beaming and guidance for the O wave when ? ? ?Mi- The relation between beaming and guidance for the combined O and X waves when ? ? ?Mi- Effect of energy absorption on Alfven guidance- Symbols- Index of subjects

Signal representation generator

Abstract: An apparatus and method for generating a representation of an arbitrary signal wherein the signal is represented as a sum of reference signals derived from a standard wavelet defined on a grid in the frequency-time plane. The apparatus comprises a plurality of octave circuits, each octave circuit, in turn, comprising a plurality of band circuits that divide a frequency range covering the spectrum of the signal into equal intervals of logarithm of frequency. Each band circuit comprises a bandpass filter to select a frequency component of the signal and a correlator to correlate the signal component with a reference signal derived from a standard wavelet to produce a series of correlation values representing the signal for recordation in response to clock pulses received by the octave circuits. The octave circuits are clocked at rates which increase by a factor of two with increasing octave of frequency with which the octave circuits are associated so that correlation time intervals decreasing by a factor of two for successively higher frequency octaves are defined for all frequency bands within each octave and one correlation value is associated with each octave and one correlation value is associated with each frequency band and with each correlation time interval to effect the representation.

Satellite communications system and method therefor

Abstract: A satellite communications system and method of communication which results in increased frequency-reusage within assigned frequency bands and allows for a reduction in satellite transponder requirements per unit of bandwidth employed The disclosed system employs a satellite in a geostationary orbit having transponders and one or more large-aperture, high-gain antennas that provide a broad-area beam for a relatively wide service area and for transmitting to and receiving signals from N narrow-area beams for N respective sub-areas, the sub-areas corresponding to the high-traffic nodes Both beam types operate in the same allocated frequency bands but with opposite linear or opposite handed circular polarizations, or, alternatively, with arbitrarily determined portions of the allocated frequency band pairs with dual polarization so that the allocated frequency spectrum is used at least N+1 times Since the narrow-area beams provide a substantially smaller illumination pattern than the broad-area beam, substantially less power is required to form each narrow-area beam at the satellite antenna so that each additional narrow-area beam results in a frequency reuse with only a relatively small incremental increase in drive power requirements Because of the reduced incremental satellite power requirements associated with the multiple additional frequency reusages, the high power amplifiers (HPA's) of the satellite transponders for the narrow-area beams can be backed-off from non-linear operation into their linear regions to allow multiple signal carrier amplification in each HPA to thus reduce the total HPA requirements for the system

Doppler sonar observations of internal waves: the wavenumber-frequency spectrum

Abstract: In May 1980 an 18-day sequence of velocity profiles of the top 600 m of the sea was collected off the coast of Southern California. The measurements were obtained using a pair of Doppler sonars mounted on the Research Platform FLIP. From these data, estimates of the wavenumber-frequency spectrum of the oceanic internal wavefield are obtained. The spectra are characterized by a series of ridges, which occur at near-internal and tidal frequencies as well as higher harmonics and sums of these fundamentals. The ridges run parallel to the wavenumber axis. There is a pronounced near-inertial spectral peak. The near-inertial motions are dominated by a few identifiable wave groups. There is a net downward energy propagation in the near-inertial frequency band. The vertical-wavenumber dependence of a the spectrum is decidedly asymmetric in this region. The asymmetry extends to five times the inertial frequency, making much of the so-called continuum asymmetric. A high-wavenumber cutoff at approximately 60...

Interleaved waveguide and dipole dual band array antenna

Abstract: A dual band array antenna is disclosed having interleaved waveguide and dipole arrays, each operating in a different frequency band. The orientation of the waveguides and dipoles is such that polarization of the signals of the two frequency bands is perpendicular to each other, thus reducing mutual coupling. The waveguides are used for the higher frequency band and their cutoff frequency is selected to be above the lower frequency band at which the dipoles operate, in order to reduce mutual coupling into the waveguides. In one embodiment the dipoles are printed on a substrate having a dielectric constant selected so that dipole spacing is the same as the waveguide spacing. This eliminates grating lobe formation in the radiation pattern of the waveguide array. A low pass filter is included in the dipole feed circuit to reject the frequencies at which the waveguides operate. As a result of the invention, two beams of two different frequency bands are independently and simultaneously steerable in a single antenna aperture.

Method for interference-resistant radio transmission

Abstract: In communications via radio paths, transmission quality is impaired not only by atmospheric interference but also by signals which desirably or undesirably make use of the same or of an immediately adjacent frequency. To achieve greater resistance in such cases to interference from signals of this type, it is known for a frequency jumping method to be used in the signal transmission in which the radio carrier frequency is modified in jumps at short intervals according to a pseudo-random pattern within a pre-defined frequency range. Practical experience has shown that here too the noise power produced by signals within the frequency band used by the jump frequencies can still be relatively high. It is proposed for further improvement of resistance to interference to monitor the jump frequencies for possible interference and to prevent their further use if an interference frequency occurs which can no longer be tolerated.

Method for digital transmission of a broadcast radio programme signal

Abstract: For digital transmission of a broadcast radio programme signal, the frequency band of the broadcast radio programme signal is split into sub-bands. The individual sub-bands are differently quantised and are subsequently transmitted using time-division multiplex. In this case, the quantisation of each sub-band is carried out on the basis of the quiescent audibility threshold and/or on the basis of the monitoring threshold which is applicable to the respective bandwidth of the sub-band, and/or on the basis of the amplitude statistics of the broadcast radio programme signal which are applicable to the respective frequency of the sub-band.

Analysis of frequency

Abstract: PURPOSE:To enable analysis of frequency portions relatively with the same capacity regardless of the level thereof, low and high, and with a limited number of data by selecting frequency to take in data from in a manner of geometric series. CONSTITUTION:The pass band width of a variable frequency band pass filter 10 with which a pass band is swept and controlled is proportional to the center frequency fo so that Q is unchanged regardless of variation in the center frequency fo. Gains Gn and Gn+1, namely, pass bands of a filter 10 are arranged very closely with respect to center frequencies fn and fn+1 as specified by a frequency setter 11 for outputting a control signal setting the pass bands of the filter 10 and a gate timing signal. The analysis data is as illustrated [frequency (f) on the axis of abscissa and component sound pressure P on the axis of ordinate]. Compared with the selection of arithmetic progression, this can reduce the number of data and also enables analysis relatively with the same capacity even at a low rotation to reduce the processing time.

Normalization of speech signals

Abstract: A method and a system are disclosed for normalizing a speech signal prior to a speech recognition process. In a preparatory procedure, a sample interval of speech is separated into thirty-one frequency bands and an amplitude histogram is generated for each band. From these histograms, the 5% percentile amplitude value P(05) and the 95% percentile amplitude value P(95) are extracted for each band and these values are stored for later reference. For actual normalization, the current speech signal is also divided into the same frequency band as in the preparatory procedure, and consecutive input amplitude values A(in) of each frequency band are modified, using the percentile values of the respective band, to obtain output values according to ##EQU1## The essential effect of this normalizing treatment is that the resulting long-term spectrum is given by the P(95) values and the spectrum of silence is given by the P(05) values. After normalization, all speech has the same silence spectrum and long-term spectrum.

Linear gain voltage controlled oscillator with modulation compensation

Abstract: In a compensated VCO circuit arrangement for providing constant modulation level over a wide frequency band a VCO (55) is disclosed having a linear VCO gain factor vs. control voltage curve over the wide frequency band of interest. A compensation network (65) is coupled to the VCO to provide an audio output having linear output level vs. control voltage curve. By appropriately matching the two linear curves the variation in modulation level over the frequency band of interest is substantially reduced.

Optical transmission channel with electrical connectors

Abstract: An optical transmission channel permitting terminal electrical connection with operating characteristics in a very wide frequency band, while maintaining the transfer function constant. It comprises an optical cable terminated at each end by a module containing, for each link, an emitting or receiving diode as a function of the particular case and its associated electronic circuit. The optical coupling is performed by a detachable optical connector within the module and each circuit has a frequency compensating circuit to produce a phase lead and accentuate the high frequencies.

Low frequency excitation in amorphous acrylic polymers

Abstract: Two or mutually nonparallel dipoles for operation over a common frequency band. Each of the dipoles has a central feed port and an inner end connected to a junction box with conductive walls. Each feed port is connected through a junction in the box to a receiver for the common frequency band. For diversity, two receivers for the common frequency band are connected to the two feed ports. For pseudodiversity, the dipoles are connected to a common receiver and are positioned to have noncoincident phase centers separated by more than one-quarter wavelength over some part of the common frequency band.

Low frequency/high frequency omnidirectional antenna formed of plural dipoles extending from a common center

Abstract: Two or mutually nonparallel dipoles for operation over a common frequency band. Each of the dipoles has a central feed port and an inner end connected to a junction box with conductive walls. Each feed port is connected through a junction in the box to a receiver for the common frequency band. For diversity, two receivers for the common frequency band are connected to the two feed ports. For pseudodiversity, the dipoles are connected to a common receiver and are positioned to have noncoincident phase centers separated by more than one-quarter wavelength over some part of the common frequency band.

Zero phase shift filtering

Abstract: A frequency band filtering circuit and phase shift free crossover network comprising at each crossover frequency range between band pass filters a low-pass filter means characterized by a transfer function that decays at a second or higher order function of frequency and a high-pass filter means characterized by a transfer function that rises as a second or higher order function of frequency and wherein the respective pair of transfer functions sum to unity. By employing circuit filters characterized by high order polynomial transfer functions that sum to unity, the combination of sharp roll-off and excellent frequency separation is achieved without introducing phase distortion when the signals are recombined or summed. Such a filtering system is useful in high fidelity speaker crossover systems, various electronic signal splitting or filtering circuits (whether analog or digital) wherein the information within individual frequency bands are to be isolated and treated independent of an adjacent frequency band yet ultimately recombined and the like.

Video tape recorder

Abstract: PURPOSE:To improve a resolution by automatically controlling a frequency of a frequency modulating luminance signal so as to interpose a frequency component interfering a frequency range of a low frequency conversion chromaticity signal into a space of frequency spectrum of the low frequency conversion chromaticity signal. CONSTITUTION:An output of an integrating circuit 24 is added to a filter output of a low pass filter circuit 7 in an adder 25, and fed back to a modulating input of an FM modulator 8. Therefore, the modulated output of the FM modulator 8 has a frequency component interfering with an occupying band of a low range conversion chromaticity signal of a lower sideband wave, which is constantly interposed into a space of a frequency spectrum of the low range conversion chromaticity signal. An automatic frequency control is carried out with respect to a frequency modulating luminance signal by an automatic frequency control circuit 22 so as to constantly interpose the lowersideband wave into the space of the frequency band of the low range conversion chromaticity signal. Accordingly, even when the frequency band of the lower side band of the the frequency modulating luminance signal is overlapped on the frequency band of the low frequency conversion chromaticity signal, a beat failure based on the interference of the luminance signal and the chromaticity signal is not produced frequency modulating luminance signal can be widened in band.

Compact broadband rectangular to coaxial waveguide junction

Abstract: A compact waveguide junction for coupling rectangular waveguide of one frequency band to a coaxial waveguide, and a second rectangular waveguide of a second frequency band to the interior of the hollow center conductor of the coaxial waveguide.

The monopole slot as a two-port diversity antenna for UHF land-mobile radio systems

Abstract: Urban land-mobile communication systems designed to operate over the upper portion of the UHF band are very susceptible to frequent wide signal variations. Deep fades arise due to the presence of many obstructions in the propagation path between the transmitter and receiver. One way to combat the effects of Rayleigh fading due to multipath propagation is to provide a diversity combiner in the mobile receiving system with two signals, each containing the same information, which fade independently of one another. Such a system can virtually eliminate deep fades from the receiver output. Described herein is a method of obtaining two diversity branches, with independent signals if so desired, from a single two-port antenna which is both well matched to the transponder and efficient over the land-mobile frequency band from 820- 890 MHz. A directive pattern is associated with each port. When operating with a direct wave, signal gain over an omnidirectional antenna is therefore possible.

Microwave FET mixer arranged to receive RF input at gate electrode

Abstract: In a GaAs FET microwave mixer, a gate of the FET is used to receive a radio frequency input signal, while a source of the same is used to inject a local oscillator signal therethrough so as to develop an intermediate frequency signal at a drain of the FET. The mixer of the invention comprises, in addition to such an FET, first and second particular circuits respectively connected to the source, where the first circuit is arranged to exhibit a short-circuited impedance at a frequency band of the radio frequency input signal, and the second circuit is arranged to exhibit an open-circuited impedance at a frequency band of the local oscillator signal. The first and second circuits may be actualized by distributed constant circuits, such as stubs, or by lumped constant circuits, such as resonance circuits.

Process and device for measuring the initial permeability of ferrimagnetic materials over a wide frequency band

Abstract: According to the process, a toroidal sample of ferrimagnetic material to be analyzed is placed in a thermostatically-controlled enclosure fitted with temperature regulation and detection means. The toroidal sample is submitted to an electro-magnetic magnetizing field of given frequency and the flux induced in the sample is measured directly using a measuring loop, around the sample and which is connected to a vectorial voltmeter.

Method and apparatus for sampling in-phase and quadrature components

Abstract: In-phase and quadrature components of a waveform are generated by sampling the waveform at a rate of four times the center frequency of the frequency band for which components are generated. The samples are digitized and applied to a digital 90° all-pass phase-splitting network. Each pair of output samples is generated as a function of input samples delayed by an even number of time instants through a first all-pass branch and delayed by an odd number of time instants through a second all-pass branch. A common network may form both branches by switching coefficients of a multiplier and alternating the output between in-phase and quadrature samples. The waveform may be shifted from a higher freqeuncy by a mixer and may be filtered prior to sampling.

A dual band phased array using interleaved waveguides and dipoles printed on high dielectric substrate

Abstract: A dual band phased array using interleaved waveguides and dipoles has been developed. Waveguides are used for high frequency band (e.g., C-band) and printed dipoles are used for low frequency band (e.g., S-band). The dipoles are printed on Hi-K dielectric board to shorten the dipole length. The element spacings for the dipole array are equal to the element spacings of the waveguide array. This densed array environment for dipoles greatly improves impedance matching and completely eliminates the grating lobe formation for both bands.

Wideband Double - Ridged 8 - Way Radial Combiner

Abstract: A new double-ridged 8 - way radial combiner over a 4 to 10GHz frequency band has been developed. The design based on ridged waveguide theory for calculating the bandwidth and impedance. The developed combiner has 0.5dB insertion loss and 1.5 : 1 VSWR over an octave bandwidth, good amplitude and phase balance, ± 0.3dB amplitude flatness and more than 6dB isolation.

Optimum pulse shape for minimum spectral occupancy in FSK signals

Abstract: The characteristics of a frequency shift keying (FSK) signal giving rise to maximum power within a prescribed frequency band are determined. The baseband pulse shape extends over any integer number of bit periods. An integral equation for the optimum pulse shape is derived and some simple properties of the solution are investigated. The equation has been solved for some values of the product of the prescribed band times the pulse duration and the signal shape is shown. Our results for the particular case of pulses only one bit period long are presented for purpose of comparison with results known in the literature. Plots of out-of-band power for some values of the prescribed band and of pulse duration are reported. Finally a comparison with the well-known TFM, Nyquist, and raised cosine signals in terms of psdf and out-of-band power is exhibited.