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The impact of time-frequency hopped multi-band orthogonal frequency division multiplexing (MB-OFDM) on in-band wideband receivers is considered. First, we compare direct-sequence and frequency-hopped ultra-wideband (UWB) systems in terms of power and range characteristics. We then show that in-band receivers with large bandwidths are susceptible to UWB systems, but direct sequence systems are potentially less harmful due to the large relative bandwidth. The MB-OFDM signal introduces less interference for long hop lengths, but the signal peak-to-average power rises. This makes the MB-OFDM signal appear impulsive to a victim receiver, causing destructive interference at high signal-to-noise ratios.

Typical relative bandwidth of transversely coupled resonator filters (TCRF) on quartz wafers varies between BW = 0.05 to 0.1%. In this paper, we investigate the factors restricting the bandwidth and describe some specific features of designing TCRF with more expanded bandwidth BW = 0.15-0.3%, on quartz. The results of investigation are illustrated by experimental characteristics of four TCRF types: 315 MHz filter with BW = 0.28%, 248 MHz filter with BW = 0.18%, 402 MHz filter with BW = 0.125% and 360 MHz filter with BW = 0.064%. All filters are manufactured on quartz wafer, cut 33.3/spl deg/-YX, in packages SMD 3.8 /spl times/ 3.8 /spl times/ 1.4 mm.

A broadband microstrip antenna for DBS (direct broadcasting by satellite) reception is presented. DBS in Europe requires a linear polarisation, a relative bandwidth of 17.5% (from 10.70 GHz to 12.75 GHz) and a cross-polarisation less than -20 dB. According to these requirements, a dual polarised aperture coupled microstrip antenna was designed in two steps. In the first step, a new disposition of the feeding lines was used. A single patch element permits to obtain a bandwidth of more than 26% whereas an additional patch element as a parasitic element is currently used in the literature to increase the bandwidth. In the second step, a perforated patch element was used in order to ameliorate the cross-polarisation.

The paper presents a new approach for designing an ultra broadband coplanar to slotline transition. The procedure is carried out in three steps: design, modeling and fabrication of two new broadband uniplanar CPW to slotline transitions, in the 1 GHz to 50 GHz frequency range. The advantages of these transitions are discussed. Both transitions are modeled using one approach which consists of building a model, based on physical considerations, that is compatible with usual CAD software (discontinuities effects are not taken into account except short/open circuits-end effects). This allows the design and optimization of very broadband transitions in uniplanar technology. The overall agreement between the measured and modeled insertion-loss and return-loss of two back-to-back transitions is good. A maximum relative bandwidth of 7.7:1 is achieved with 10 dB return loss, and the corresponding insertion loss is less than or equal to 2 dB.

A planar 3 dB coupler in the form of an 8-port elliptical disc is investigated theoretically and experimentally. The hybrid consists of additional reactive stubs and impedance steps for tuning purposes. The new device features flat coupling, good return loss and isolation over a 20% relative bandwidth. >

The performance of a conventional branch-line 3-dB hybrid tends to deteriorate with increasing operation frequency because of a pair of low impedance series line sections. This paper treats planar-circuit-type 3-dB quadrature hybrids using a rectangular disk, and realizes good characteristics comparable to those of an ideal branch-line hybrid over a wide operation frequency range by efficacious devices without destroying the simple-shaped configuration. In addition, the way of broadening the hybrid property are examined and hybrids with flat coupling, e.g., a relative bandwidth of 27 percent, are obtained at various operation frequencies. These theoretical results are verified experimentally. >

The problem of designing ultra-narrowband switched-capacitor filters (relative bandwidth >

Summary form only given. Parametric acoustic sources have been used in conventional sub-bottom profiling operation for some time. Due to their narrow acoustic beam, well defined signature and high relative bandwidth, very high spatial resolution can be achieved. These features will also be of interest in applications such as sediment characterisation, object detection and classification. In the MAST-III project ISACS, the TOPAS parametric source is used as the low frequency source for sediment characterisation. A model based classification scheme for normal incidence where surface and volume contributions are separated, has been developed. Results of using this model with the TOPAS source are presented. The parametric source also gives promising results when used for object detection and classification. Examples of results will be presented.

Conventional coherent diffractive imaging (CDI) techniques rely on inversion of the two-dimensional phase problem in the fully coherent limit. Current work using synchrotrons has shown that by introducing a flexible parameter in a technique known as polyCDI, some reduced temporal coherence with relative bandwidth ~3% can be tolerated for simple non-dispersive objects. We demonstrate that using a high harmonic source with modulated spectral characteristics, although the excellent temporal coherence properties are lost in detection, it is possible to increase the tolerable relative bandwidth to ~20% by using the shrinkwrap technique and treating the data as if they were fully coherent but noisy. This reduces the integration time by a factor of ~5. This result is critical for the future use of lab-based sources of extreme ultraviolet and soft x-rays for CDI of non-dispersive objects, and we anticipate that it will improve results at synchrotron sources also.

We report on the theoretical analysis of the enlargement of locally resonant acoustic band gap in two-dimensional sonic crystals based on a double-side stubbed plate. A significant enlargement of the relative bandwidth by a factor of 2 compared to the classical one-side stubbed plates is obtained and discussed. Based on an efficient finite element method, we show that this band gap enlargement is due to the coupling between the same nature of the resonant eigenmodes (in-plane or out-of-plane) of the stubs located in each plate side, producing a strong interaction with the plate’s Lamb modes. Acoustic displacement fields are computed to illustrate such mechanism and to discuss the physics behind it.

A full-wave method, which combines the efficiency of mode matching method with the versatility of finite difference method, is applied to the analysis of H-plane mitered bends in rectangular waveguide. The bend is segmented into various regions characterized by means of a generalized admittance matrix representation. The latter is calculated by modal analysis for "regular" regions and by finite difference for "irregular" regions. Design charts are presented giving the optimal mitering as well as the relative bandwidth of the mitered bend.

Discrimination thresholds for spatial frequency and contrast were measured as a function of (1) the spatial-frequency bandwidth of the stimuli, (2) the reference contrast of the stimuli, and (3) whether the observer knew on which dimension, spatial frequency or contrast, the stimuli would differ. Relative bandwidth was manipulated by a one-dimensional Gaussian window and varied from 0.25 to 2.0 octaves. The results of two different tasks were compared. In a single-judgment task the observer knew on which dimension the stimuli would differ, and discrimination thresholds were measured in a standard two-interval forced-choice staircase procedure. In a dual-judgment task the dimension on which the stimuli differed varied from trial to trial. In this task the observer made two judgments on each trial in a modified two-interval forced-choice procedure: (1) on which dimension the stimuli differed and (2) in which interval the stimulus with the higher spatial frequency or contrast appeared. Thresholds were measured by five interleaved staircases for five reference contrast levels that varied from 0.02 to 0.32. Thresholds for both spatial frequency and contrast increased with increasing stimulus bandwidth and decreased with increasing stimulus contrast. Thresholds were, on average, 1.8 times higher in the dual-judgment task than in the single-judgment task, independent of the stimulus contrast and the bandwidth. A stimulus-uncertainty model is described that accounts for the difference between thresholds in the single- and the dual-judgment tasks.

Spinel ferrite flakes Ni0.97−xZnxCo0.03Fe2O4 with x=0.5 and 0.65 are prepared for use as fillers in electromagnetic composites. The composites with the flaky fillers exhibit greatly enhanced high-frequency and attenuation properties. The complex permeability, μ0′ and μmax″, is enhanced by about 500%–700%, and the relative attenuation bandwidth WR is increased by 300%–440%, as compared to those for composites with conventional spherical fillers. WR achieves 90% of the theoretically maximum relative bandwidth. The composites with the spinel ferrite flaky fillers are powerful and potential candidates as electromagnetic attenuation materials with ultrabroad bandwidth at microwave L, S, and C bands.

Z-type barium ferrite flakes were prepared for use as fillers in electromagnetic attenuation composites. The composites with the flaky fillers exhibit greatly enhanced complex permeability, thus achieving an ultrabroad attenuation bandwidth. μ0′ and μmax″ are enhanced by above 150%, and the relative bandwidth WR of 6–7 can be achieved. The bandwidth achieves 75% of the theoretically maximum relative bandwidth. The composites with the flaky fillers are powerful and potential candidates as electromagnetic attenuation materials with ultrabroad bandwidth in L, C, and S bands.

Novel reconfigurable Wilkinson power dividers with a minimum number of switches are introduced. In the first design, re-routing of output power between one and two ports is achieved with only three switches. A second design employs a switched coupled line transformer, and requires four switches. Both operating modes of the power dividers are matched and achieve a relative bandwidth of approximately 10%. The construction of the dividers and experimental results are presented at 2.14 GHz.

It has been suggested for the first time that the Z--polarized shear mode in Te02 is a kind of the mode which is appropriate to operate in a high frequency region and possesses a large time bandwidth product. By solving the Christoffet equation, the characteristic mode of the Z--polarized shear wave has been obtained. Some practidal examples show that the mode is of a wide bandwidth, and a proper center frequency makes the relative bandwidth approach 1.

The microstructure, static, and dynamic magnetic properties have been investigated for BaCoZnFe16O27 doped with small amounts of V2O5 from 0 to 1.5wt%. The results show that the doping of V2O5 can significantly improve the dynamic properties of W-type barium ferrites at microwave frequency. As compared to the undoped sample, the permeabilities μ0′ and μmax″ increase by about 42% and 67%, respectively, for the sample doped with 1.0wt% of V2O5. Due to the V2O5 doping, perfect hexagonal-plate grains are formed, leading to the decrease in the natural resonance frequency, due to the large demagnetizing effect. The predicted reflection loss shows that the maximum relative bandwidth Wmax=fup∕flow reaches 3.9 for attenuation of more than 10dB in the sample doped with 1.0wt% of V2O5. This is a good candidate for electromagnetic materials with low reflectivity and broadband at microwave frequency.

The bandwidth of reflection coefficients are evaluated for the conducting strips on a grounded dielectric and magnetic slab for the use as artificially soft and hard surfaces. The closed-form reflection coefficients developed are utilised in parameter study. The hard surface realised by magnetic material slab has significantly wider bandwidth than that realised by dielectric material slab. For a perfectly hard surface, a simple proportionality between the relative bandwidth and the design frequency is found for the first time.

A mathematical model of the dynamic frequency characteristics of the heterodyne spectrum analyzer with a rectangular bandpass filter of small relative bandwidth is constructed. The model is investigated numerically and proved experimentally.

When ferrites are used for electromagnetic wave absorbers in the VHF and UHF bands we note their excellent properties such as their wider dynamic frequency bandwidth and their thinner thickness than that of lossy dielectric absorbers, which are due to their magnetic losses. However, there exists an upper frequency limit beyond which the frequency bandwidth of ferrite absorbers becomes narrower than that of lossy dielectric absorbers. In this paper we added ferrites to carbon-rubbers and examined their characteristics as electromagnetic wave absorbers. We found through experiments that the relative bandwidth is widened more than twice by adding ferrites of only relative weight ratio 0.2 to rubber when the relative weight ratio of carbon to rubber is 1.1. Although we made measurements in the frequency range of 5 to 6 GHz, we expect the same effectiveness at higher frequencies.

We have derived the relationship between the leakage inductance and the winding structure for an electronic transformer with a flat cable wound around a circular cross-sectional core. It is found that: (1) the leakage inductance of a flat cable transformer with a circular cross-sectional core is approximately identical to one with a square core cross-sectional core. Next, the winding configuration of a multilayer winding flat cable transformer is classified into lap winding, turn-up lap winding and twisted lap winding; (2) the leakage inductance is higher for the lap winding and the turn-up lap winding than for the one layer winding, but the increase of the equivalent capacitance is minimal for the lap winding; (3) the leakage inductance is even smaller in the twisted lap winding than in the one layer winding; and (4) the leakage inductance per winding length does not increase in the flat cable transformer even if insulators are inserted between layers. Further, based on the leakage coefficient, the unit leakage constant is defined. It is found that: (5) the circular cross-section core is superior to the square cross-sectional core for a wider relative bandwidth and a restricted range of unit leakage constant; and (6) a wider relative bandwidth is more difficult to obtain as the core becomes smaller. These results agree well with experimental findings.

The power inversion adaptive array proposed by Compton differs from other adaptive arrays in that it does not require any information on the desired signal. However, there is a sudden reduction in the ratio of signal to interference and noise (SINR) at the output terminal when the relative bandwidth of the interference signal exceeds 5%. In this paper the elements are arranged in a circular arc and a formula is proposed for microprocessor determination of the element weight from the covariance between the element inputs. It is shown that the decrease in SINR is kept below 3 dB even when the relative bandwidth of the interference is as large as 50%. In Method 1 of the circular arc arrangement an element is placed at the center of the circle and in Type 2 no element is placed at the center. Wideband elimination of the interference can be achieved with the arrival angle orthogonal to the line connecting two arbitrary elements. The element arrangements are studied with a low level of redundancy for this ideal angle of arrival. It is shown that a system without redundancy can be realized with a 4-element array of Method 2.

The broadening and splitting of auditory events in dichotic listening conditions with various degrees of interaural coherence are discussed. By using a psychoacoustical mapping method, it has been possible to observe broadening and splitting for a wide range of stimuli, including broadband pink noise as well as bandpass noises with different relative bandwidths and center frequencies. The spatial extents of the auditory events decrease with increasing center frequencies for bandpass stimuli of constant relative bandwidth. The number of partial events for bandpass stimuli decreases with increasing degrees of interaural coherence. These results are, for example, of interest with respect to auditory spaciousness in architectural acoustics.

The temporal resolution and accuracy of frequency-time analysis (FTAN) as applied to surface-wave dispersion analysis are examined for a period range from 10 to 200 sec. The constant relative bandwidth filter (Dziewonski et al., 1969), optimum bandwidth filter (Inston et al., 1971), and display-equalized filter (Nyman and Landisman, 1977) are carefully examined with respect to their adequacy of application over a broad period range. Among these Gaussian filters, the optimum bandwidth filter gives a better performance for relatively short-period (less than 50 sec) dispersion measurement. To measure surface-wave dispersion for a broad period range, a “matched-filter FTAN” technique is introduced by modifying the “residual dispersion measurement” technique (Dziewonski et al., 1972). A detailed numerical analysis is made on this new technique; the result demonstrates a significant improvement on both the resolution and the accuracy of surface-wave dispersion data extraction over a broad period range up to at least 200 sec.

A frequency selective coupler which consists of two thin film waveguides imbedded in a periodic medium is studied using the Brillouin diagram. Detailed results for the relative bandwidth and the coupling factor are plotted as a function of normalized frequency for a representative case.

The transfer impedance of conventional delay lines with plane‐parallel transducers exhibits, as a function of frequency, typical zeros, which limit the useful relative bandwidth. It is shown in this paper that the transfer impedance of a delay line with plane concave transducers does not have these zeros and for that reason can have a much larger relative bandwidth.

Ferrites have been known as good absorbers of electromagnetic waves for some forty years. They are very effective against the conventional radar using signals with small relative bandwidth, but they should have almost no effect on radar signals with large relative disappointment if this fact is overlooked.

A monolithic Chebyshev CCD wave filter with a center frequency of f o = 50kHz and a relative bandwidth of 4.2%, 5dB insertion loss and 60dB stopband attentuation will be described.

The design possibilities and limitations of multilayer structures for soft x‐ray spetroscopy are summarized. Near grazing incidence structures can have a large integrated reflectivity and a large relative bandwidth close to one. The smallest possible bandwidth or highest possible resolution is obtained ner normal incidence, and is determined by the absorption index k of the most transparent material available; the maximum resolution in Nmax≂1/2πk. Depending on the wavelength, values for Nmax can be between 10 and 104 in the soft x‐ray region. The practical realization of a design requires good thickness control and sharp, smooth boundaries between the layers. Sufficient thickness control has been obtained by in situ monitoring of the x‐ray reflectivities. Within the uncertainties of the optical constant the measured performance of the best multilayer systems is in agreement with theory for multilayer periods larger than 30A. For smaller period lengths, the peak reflectivity is smaller than the theoretical values. The lower reflectivity can be explained by an effective roughness of the multilayer system in the order of 3A.

A novel low loss guiding structure (INWATE) is applied to the design of GaAs FET waveguide amplifiers. Experimental results of a single stage amplifier show a gain characteristic of 6.7 ± 0.15 dB within a relative bandwidth of 2.4 % at a midband frequency of 10.15 GHz with an associated minimum noise figure of 3.6 dB (MGF 1302 : MAG = 9.8 dB, FMIN = 2.3 dB).

Broadband TE/TM conversion is obtained by adjusting the direction of wave propagation with respect to the optical axis. z-10 degrees wave propagation offers 3% relative bandwidth at lambda 0=1.3 mu m combined with low temperature dependence and 100% crossover efficiency.

Many authors have dealt with the theoretical and experimental investigation of waveguide junction Y- circulators. Exact field theory treatments were introduced for circulators with more or less complicated material inserts /1,2,4/. For broadband applications, the partial height ferrite circulator is widely used and was investigated by several authors /4,5,6/. Using the mode matching technique, the entire field theoretical problem is solved. High accuracy between theory and experiment is achieved. The relative bandwidth for the calculated and measured circulator are 29% and 31.6%, respectively.

Since 1976, our group carried systematical annual experiments on Myotis mystacinus in very convenient sites: Montellier (Ain) France, 20 km N.E of LYON. During June 1980 (16/05/80) records were made of SONAR signals emitted by Myotis mystacinus during take off and the early part of flight. Bats were taking off from behind a shutter of an old barn (see fig. 1). We only register during this experiment the take off signals and the cruise ones emitted when the bat is flying to the microphone (16).

A CW sub-millimetre wave imaging system is presented. The system operates around 340GHz with a 6.5% relative bandwidth and uses a non-linear imaging algorithm.

A novel Printed-Circuit-Board (PCB) solution to avoid common-mode resonances in connected arrays is proposed in this paper. It consists in a loop-shaped circuit that rejects common-mode current propagation over more than an octave bandwidth. The use of such common-mode rejection loop allows the design of linear and dual polarized array of connected dipoles, with cross-polarization levels lower than -17 dBs for elevation angles in the range ±45° and for all azimuths, over more than 30 % relative bandwidth. Full-wave simulations are presented to validate the design..

A transition from the substrate integrated waveguide (SIW) to the microstrip line with built-in dc-decoupling is presented. The proposed transition has an interdigital configuration on a single layer. It features a 25% relative bandwidth with less than 0.7 dB of insertion loss and more than 15 dB of return loss.

A distinct enhancement of the traditional circulator in both the isolation and operational bandwidths has been found to be realized by means of a trigonally symmetric magnetic system. Experiments utilizing the field probing scheme which the present author published previously have verified that the proposed magnet system significantly contributes to the simultaneous enhancement of both the bandwidth and the isolation, in that field concentration favoring isolation enhancement is realized, and that tapered field matching is established. The proposed new magnet system has enabled a compact C-band circulator to be implemented with isolation as high as 30 dB or more for a relative bandwidth of 27 percent while holding the insertion loss at less than 0.5 dB.

The mode-matching technique is used to solve the entire field theory problem of the widely used partial height ferrite circulator. Calculation and measurement of an X-band circulator gives 29% and 31.6%, respectively, for relative bandwidth at an isolation of 20 dB. >

The unloaded quality factor of a dielectric resonator, in the MIC environment, and magnetically coupled to a terminated microstrip line, is estimated by using a network analyser. It is sufficient to compute the relative bandwidth of the interception between the reflection coefficient locus and the R − 1 = ±jX arcs.

A different acoustooptic configuration using Yano’s paratellurite crystal cut is proposed in this paper. Both configurations are compared in terms of relative bandwidth, efficiency, and potential applications. Experimental results are also reported.

Broadband TE/TM conversion is obtained by adjusting the direction of wave propagation with respect to the optical axis. z − 10° wave propagation offers 3% relative bandwidth at λ0 = 1.3 μm combined with low temperature dependence and 100% crossover efficiency.

As the result of recent progress in polarisation-maintaining optical waveguiding schemes, a basic question now arises: which of stress-induced type or geometrical type approach will finally offer better characteristics? The letter discusses the ultimate performance of a side-tunnel fibre which offers the strongest polarisation-maintaining capability among various geometrical-type ones. The result indicates that, if the structure is optimised, a relative bandwidth of truly single-polarisation characteristics of 0.21 and a normalised birefringence of 0.0045 can be achieved for a relative core-cladding index difference of 0.01. These values are comparable to or higher than the best data reported so far with stress-type ones.