Progressive Phase Shift Research Articles

Beam‐steerable meanderline antenna using varactor diodes

AbstractThis study presents a beam‐steerable traveling wave meanderline array at X‐band.Beam steering is achieved by the varactor diodes mounted on the meanderline that provide progressive phase shift between array elements. It is demonstrated that the radiation direction of the eight‐section meanderline array containing eight varactors can be rotated 10° by changing the varactor diode's bias voltage. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:200–204, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25634

Frequency Selective Surface Using Nested Split Ring Slot Elements as a Lens With Mechanically Reconfigurable Beam Steering Capability

The design is described of a double layer frequency selective surface which can produce a differential phase shift of 180° as the wave propagates through it at normal incidence. The hand of an applied circularly polarized signal is reversed due to the 180° phase shift, and it is demonstrated that the exit circularly polarized output signal can be phase advanced or phase retarded by 180° upon rotation of the elements comprising the structure. This feature allows the surface to act as a spatial phase shifter. In this paper the beam steering capabilities of a 10 × 10 array of such elements are demonstrated. Here the individual elements comprising the array are rotated relative to each other in order to generate a progressive phase shift. At normal incidence the 3 dB Axial Ratio Bandwidth for LHCP to RHCP conversion is 5.3% and the insertion loss was found to be -2.3 dB, with minimum axial ratio of 0.05 dB. This array is shown to be able to steer a beam from -40° to +40° while holding axial ratio at the pointing angle to below 4 dB. The measured radiation patterns match the theoretical calculation and full-wave simulation results.

94 GHz Dual-Reflector Antenna With Reflectarray Subreflector

The design, construction and measured performance is described of an offset parabolic reflector antenna which employs a reflectarray subreflector to tilt the focused beam from the boresight direction at 94 GHz. An analysis technique based on the method of moments (MoM) is used to design the dual-reflector antenna. Numerical simulations were employed to demonstrate that the high gain pattern of the antenna can be tilted to a predetermined angle by introducing a progressive phase shift across the aperture of the reflectarray. Experimental validation of the approach was made by constructing a 28 times 28 element patch reflectarray which was designed to deflect the beam 5deg from the boresight direction in the azimuth plane. The array was printed on a 115 mum thick metal backed quartz wafer and the radiation patterns of the dual reflector antenna were measured from 92.6-95.5 GHz. The experimental results are used to validate the analysis technique by comparing the radiation patterns and the reduction in the peak gain due to beam deflection from the boresight direction. Moreover the results demonstrate that this design concept can be developed further to create an electronically scanned dual reflector antenna by using a tunable reflectarray subreflector.

Electrically Steerable Single-Layer Microstrip Traveling Wave Antenna With Varactor Diode Based Phase Shifters

The design of electrically steerable traveling wave microstrip antenna arrays is presented. Varactor diode based phase shifters implemented on the same metallic layer as the patch elements are used to provide a variable progressive phase shift in the array. Two antennas for the 5.8 GHz ISM band, manufactured as single layer printed designs on a standard PTFE soft substrate, are demonstrated. A ten-element beam-tilting vertical array using transmission type phase shifters is realized, yielding between 11.8 to 13.9 dBi gain for the 0deg to 11deg beam tilt tuning range. Using wide phase tuning range reflection type phase shifters a five-element horizontally scanning array with -32deg to 32deg steering range and 10.9-11.3 dBi gain has been realized.

A New Millimeter-Wave Printed Dipole Phased Array Antenna Using Microstrip-Fed Coplanar Stripline Tee Junctions

A new millimeter-wave printed twin dipole phased array antenna is developed at Ka band using a new microstrip-fed CPS tee junction, which does not require any bonding wires, air bridges, or via holes. The phased array used a piezoelectric transducer (PET) controlled tunable multitransmission line phase shifter to accomplish a progressive phase shift. A progressive phase shift of 88.8/spl deg/ is achieved with the 5 mm of perturber length when the PET has full deflection. Measured return loss of the twin dipole antenna is better than 10 dB from 29.5 to 30.35 GHz. Measured return loss of better than 15 dB is achieved from 30 to 31.5 GHz for a 1/spl times/8 phased array. The phased array antenna has a measured antenna gain of 14.4 dBi with 42/spl deg/ beam scanning and has more than 11 dB side lobe suppression across the scan.

Relation between vestigial-sideband filtering and pi/2 progressive phase shift.

We show that a Gaussian-shaped vestigial-sideband (VSB) return-to-zero (RZ) on-off-keying (OOK) optical signal is essentially a RZ OOK signal with pi/2 progressive phase shift. The reduced intersymbol interference of the VSB signal can be explained as a destructive interference effect. We experimentally demonstrate a method for generating an effective 40-Gbit/s VSB signal without relying on the detuning of an optical filter.

Magnetic island structures and their rotation after pellet injection in FTU

Pellet injection gives rise to a rich variety of observations on m = 1 island dynamics. Pellet ablation near the q = 1 surface triggers fast growth of an island; as the island reaches a large amplitude, magnetic reconnection mixes the plasma centre with the q = 1 pellet fuelled region, so enhancing the effective pellet deposition depth. Long-lived m = 1 islands that coexist with sawtooth crashes are accompanied by higher harmonics (m/n = 1 with m > 1, where m is the poloidal mode number and n is the toroidal one) near the q = 1 surface; progressive phase shifts observed in the phase of such harmonics indicate island deformation by sheared viscous flow. Coupling between m = 1 and m = 2 islands is observed in sawtooth-free plasmas. Reconnection at the q = 2 surface is driven by a toroidal sideband of the m = 1 island; coupling is associated with strong braking of the m = 1 island.

94 GHz zonal ring reflector for helicopter collision avoidance

A single-layer reflector antenna combining eight and four correcting Fresnel zones is presented. The progressive phase shift is achieved by circular and annular patches. The choice of a quarter-wavelength thickness substrate provides naturally 0 and 180° correcting zones that simplify the reflector design. A prototype of reflector antenna working at 94 GHz has been designed, built and measured. Measurement results show 70% improvement of antenna aperture efficiency compared to the half-wave Fresnel zone plate reflector .

Beta and gamma oscillations in the olfactory system of the urethane-anesthetized rat.

Fast oscillations in the beta (15-40 Hz in awake rats) and gamma (50-100 Hz) frequency ranges are prominent in field potentials induced by odorants in the mammalian olfactory bulb (OB) and piriform cortex (PC). Whereas the gamma oscillation has been studied for >50 yr, the beta oscillation has attracted attention only recently, and its origin, mechanism, and relationship to gamma are unknown. To address these questions, we have examined responses induced by odorants in the urethane-anesthetized rat-a preparation well-suited for the analysis of mechanisms. We found that both oscillations could be induced by odorants in a concentration-dependent manner. Analysis with a concentration series and spectral methods revealed that the beta and gamma oscillations were distinct and not harmonically related, indicating generation by independent mechanisms. The beta oscillation was synchronous at sites < or =4 mm apart in the OB, the greatest distance tested. In contrast, the gamma oscillation was synchronous in some experiments and asynchronous in others (frequency differed slightly at different sites, resulting in progressive phase shifts). Current source-density analysis indicated that, for both oscillations, the field potentials in the OB were generated by synaptic currents in granule cells. The two oscillations were differently affected by surgical interruption of the lateral olfactory tract. This lesion abolished the beta oscillation, whereas the gamma oscillation was still induced in the OB. Our results confirm previous reports that the gamma oscillation is generated within the OB but indicate that the beta oscillation requires the participation of PC.

Spontaneous activity of otolith-related vestibular nuclear neurons in the decerebrate rat

The discharge properties of lateral and descending vestibular neurons responsive to constant velocity off-vertical axis rotations (OVAR) in the clockwise (CW) and counterclockwise (CCW) directions, were studied at the stationary and earth-horizontal position of decerebrate adult rats. From the coefficient of variation (CV), the spontaneous activities of OVAR-responsive neurons were classified into regular and irregular patterns. Of the neurons (n = 36) that showed symmetric and stable bidirectional response sensitivity (δ defined as CW gain over CCW gain) to OVAR (10° tilt), some exhibited progressive phase shift with velocity (1.75–15°/s) while others exhibited stable response phase. Most neurons of the former group (93% or 1213) showed regular discharge pattern while only 22% (n = 523) of the latter group showed such a pattern. Though the phase-stable neurons showed a significantly higher average CV than the phase-shifted neurons, there was no significant difference between the mean spontaneous firing rates of these neurons. The neurons (n = 17) that showed asymmetric and variable δ to OVAR velocity can also be grouped - those that exhibited a greater gain with rotations directed towards the side of recording (I neurons) showed irregular discharge pattern while those that exhibited a greater gain with rotations directed towards the side contralateral to recording (C neurons) showed regular discharge pattern. The I and C neurons also exhibited significant difference in mean firing rates. The relationship between the response characteristics of the OVAR-responsive neurons and their spontaneous activity at the stationary and earth-horizontal position is discussed.

Temporal shifts in peak daily activity in Alzheimer's disease

AbstractClinicians caring for Alzheimer patients have observed that some individuals show increased agitation, restlessness and confusion in the late afternoon, evening or at night. This has popularly been named ‘sundowning’ or ‘the sundowning syndrome’. Despite its obvious clinical importance, little research has been conducted to investigate abnormal activity patterns in patients with Alzheimer's disease. In this study, rest–activity patterns were examined using and electronic monitor with a movement sensor. Eighteen patients diagnosed with Alzheimer's disease were monitored for 48 consecutive hours each. Analyses indicated that some subjects showed increased activity around the time of sunset, and that these individuals were most likely to be in the middle stages of the disease. Subjects in the early stages of the disease showed peak activity before sunset, while those in the late stage showed peak activity after sunset. This progressive phase shift with increasing years of illness is a previously unreported phenomenon which may offer an explanation for the ‘sundowning syndrome’.

Independent null steering in the sum and difference patterns of antenna arrays using real weights

A method for steering nulls in the sum and difference patterns of a phased linear antenna array using only real weights is introduced. The proposed method decouples the weights so that a given jammer is associated with a given weight value. A change in the jammer's direction changes only its corresponding weight value without affecting the other nulls. The main beam is steered independently using a progressive phase shift. This allows the signal-to-jammer power ratio to be maximized with relative ease. The drawback of this method is that the number of jammers that can be nulled will be reduced to about a quarter of the number of array elements.

Computer analysis of vertical radiation patterns of dipole panel array antennas

A GW BASIC computer program has been developed to analyze any azimuth vertical radiation pattern of a dipole panel array antenna, fixed on a square tower structure, under different conditions of horizontal progressive quadrature current phase shifting, mechanical panel displacement, beam tilt, feeding current coefficients (null filling) and asymmetric arrangements with and without panel centering. The final effects are singled out by comparing vertical radiation pattern diagrams corresponding to each condition. The result obtained in regard to simultaneous horizontal progressive current phase and mechanical shift show appreciable variations in the vertical radiation patterns, corresponding to arrays of one or two dipole per tower face (omnidirectional arrangement), while for more elements there is a negligible effect on the main beam, but noticeable changes on the sidelobes. On the other hand, for any omnidirectional arrangements under the forementioned conditions of current phase and mechanical shift, almost no vertical radiation is produced by an array of eight dipoles at 0 degrees along the tower (compensation effect). For an array with binomial current coefficients, almost no changes on the beam pattern has been observed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A pulse ribbon model of monaural phase perception.

This article presents two sets of experiments concerning the ability to discriminate changes in the phase spectra of wideband periodic sounds. In the first set, a series of local phase changes is used to modify the envelopes of the waves appearing at the outputs of a range of auditory filters. The size of the local phase change required for discrimination is shown to be strongly dependent on the repetition rate, intensity, and spectral location of the signal. In the second set of experiments, a global phase change is used to produce a progressive phase shift between the outputs of successive auditory filters, without changing the envelopes of the filtered waves. Contrary to what is often assumed, listeners can discriminate between-channel phase shifts once the total time delay across the channels containing the signal reaches 4-5 ms. In this case, however, the discrimination is largely independent of signal parameters other than bandwidth. A highly simplified model of the cochlea, consisting of an auditory filter bank and units that record the times of the larger peaks in the filter outputs, is developed to explain the two contrasting sets of results.

Smoothing of Omnidirectional Horizontal Radiation Patterns of tfd TV Panel Antenna Arrays With Progressive Current Phase Shift Feeding

This paper shows how the mechanical panel displacement technique can be used effectively in order to smooth out omnidirectional patterns of TFD TV panel antenna arroys fed by progressive phase shift currents (Fig. la).

Discharges of pyramidal tract and other motor cortical neurones during locomotion in the cat.

A method is described for chronically implanting fine flexible microwires into cat motor cortex, which permitted extracellular recordings to be made from 165 single neurones. Most units were recordable for 12 h and some for up to 2 days. Of the neurones tested, 57% were shown to project to the medullary pyramid (pyramidal tract neurones, p.t.n.s). Antidromic latencies corresponded to a range of conduction velocities from 63 to 9 m/s. In the animal at rest neurones discharged at rates from 0.5 to 44 impulses/s. During locomotion at 0.5 m/s (a slow walk) 56% of cells discharged faster than at rest and 80% showed frequency modulations time-locked to the step cycle. Most fired one discrete burst of impulses per step or one peak period superimposed on a maintained discharge. In different cells peak activity occurred at widely different times during the step cycle. A few cells peaked twice per step. Peak rates (averaged over twenty steps) ranged from 10 to over 120 impulses/s, the values for most slow-axon p.t.n.s (conduction velocity less than 21 m/s) being lower than for any of the fast-axon p.t.n.s. For locomotion at speeds between 0.37 and 1.43 m/s a roughly linear relationship existed between discharge rate and speed in 14% of cells. However, the changes were modest and in most cells both mean rate and peak rate were unrelated to speed. In some cells discharge phasing was fixed (relative to the step cycle in the contralateral forelimb); in others there were progressive phase shifts (or more complex changes) as speed increased. During locomotion up a 10 degrees incline discharge phasings were the same as on the flat in all of the twenty-seven neurones studied and most showed no substantial change in mean rate or peak rate (although there were substantial increases in limb muscle electromyogram amplitudes).

VLF wave growth and discrete emission triggering in the magnetosphere: A feedback model

Doppler‐shifted cyclotron resonance between electrons and narrowband whistler mode waves is employed in a new feedback model to account for observed signal growth and emission triggering in controlled experiments using the Siple Station, Antarctica, VLF transmitter. The interaction region (IR) is centered on the magnetic equator and is treated like an unstable feedback amplifier with a delay line. The temporal growth rate is given by γ = (G−1)/T, where G is the loop gain and T is the effective loop delay. For G&lt;1 the system acts like an amplifier, while for G&gt;1 the system is unstable and can generate self‐excited oscillations. The self‐excited oscillations reach saturation when G falls to unity, which occurs when the electron transit time through the interaction region is comparable with the phase bunching time. At signal levels well below saturation the model predicts exponential temporal growth. Saturation fields just inside and outside the plasmapause are estimated to be 1 mγ and 12 mγ, respectively, consistent with measurements. Because of a progressive loop phase shift the stimulated radiation can cancel the input signal at a certain point (located near the input to the IR) in time and space, giving rise to transient conditions resembling those at the tail‐end of the triggering signal. It is postulated that this temporary null may be the cause of emission triggering, and hence the region around this point is called the ‘triggering window.’

Labyrinthine Influences on Motoneurons Responsible for Vertical Eye Movements in the Rabbit

The analysis of the dynamic response properties of the oculomotor neurons (OMN) innervating three of the four muscles primarily involved in the vertical compensatory movements of the rabbit's eye during sinusoidal lateral tilt has pointed out that both static and dynamic vestibular receptors play a role in the reflex. The different characteristics of vestibular control on OMN can be investigated by choosing the appropriate range of stimulus frequency. At the lowest frequency of stimulation, the peak of the OMN discharge is almost in phase with head position. A progressive phase shift towards head velocity takes place by increasing the frequency of tilt. By lowering the frequency of tilt the analysis of the system was extended into a range of acceleration in which otolithic receptors alone are able to influence the OMN discharge. Because changes in head position represent the adequate stimulus for macular receptors, the pattern of activity of OMN has been correlated with this variable. These observations indicate that in the rabbit, during very slow movements of the head about the longitudinal axis, in the absence of vision, a certain degree of compensation in eye position can still be provided by the otoliths.

An isotropic frequency-independent antenna system for simultaneous omnidirectional Doppler shift removal

Simultaneous omnidirectional Doppler shift removal may be accomplished by using a frequency-scanned line source antenna aligned in the direction of net motion. A progressive phase shift along the antenna, which varies linearly with frequency, is required to match the Doppler variation with angle. Simultaneous omnidirectional radiation is accomplished by transmitting bandlimited white noise into the antenna. The resulting antenna system is isotropic, frequency-independent, and radiates a narrow-band signal, as observed by a distant receiver.

Ceramic rod array scanned with ferrite phase shifters

Steering a radiation beam originating from a stationary antenna rapidly and at will is one of the most attractive problems in the field of antenna engineering. This paper describes some aspects of the authors' efforts to develop an efficient and reliable electronic scanning antenna system. The prototype of the antenna consists of a linear array, a power distributor, an electronic phase-shift feed scheme, and its driver. The array consists of ceramic rod antennas, which are fed separately from the ends of parallel waveguides lined up in the H-plane. The power distributor is composed of directional couplers and magic tees, and is used for beam forming. The electronic phase-shift feed scheme is provided by inserting a ferrite phase shifter into each of the above-mentioned waveguides. The waveguides are of equal length and are connected in parallel to the microwave source (transmitter, receiver, or both) through the power distributor. The driver generates a number of sawtooth wave currents, which have different repetition frequencies derived from the design equation, and excite the corresponding ferrite phase shifters. Thus a uniform progressive phase shift, which varies in a sawtooth waveform with time, is achieved along the array and the radiation beam is scanned with higher efficiency. The design and engineering of the antenna are discussed, with special attention to performance reliability and reproducibility.