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A framework is presented to investigate the leading causes that determine deviations between simulation and measurement results in circularly polarized (CP) antennas operating in the millimeter-wave (mm-wave) range. For mm-wave antennas in general and CP antennas in particular, the whole validation procedure is considered to be especially challenging. The mechanical differences between the application design of the antenna and its measurable counterpart also have a significant impact on the antenna characteristics.

An optimized double-reflector antenna concept for a wideband focal plane array (FPA) configuration is presented for Ka-band applications with a limited scan range, e.g., ground terminals for satellite communication. The proposed reflector configuration allows maximizing the number of active array elements and minimizing the actual array size during scanning. In addition, the FPA configuration has been optimized for wideband optical true-time-delay beamforming, resulting in wideband operation from 20 to 40 GHz. Based on a minimum required 80% aperture efficiency at 30 GHz, the double-reflector concept allows expanding the illuminated region of the array by a factor of 60 compared to traditional prime-focus configurations. The proposed configuration also decreases the magnification factor M by a factor of 2.5 compared to the double-parabolic configuration for a ±1.5° scan range.

A three-dimensional (3-D) passive electromagnetic (EM) deflector configuration, based on the concept of spatial feeding, is proposed that modifies the incident EM energy from the steerable planar antenna array (source) to achieve wide angular coverage. A generalized analytical formulation of the parametric deflector configuration is carried out. The analytical modeling has been validated by 3-D simulations and measurements. The analytical results for the deflector configuration indicate that a wide angular coverage is possible at the cost of reduced gain. An improved 60-GHz circularly polarized (CP) deflector element has been designed that provides phase shift with element rotation upon transmission of circular polarization. The simulation results show that the proposed CP element operates successfully, in terms of realization of phase-shift range from 0° to 360° and good transmission properties (transmission loss

Commonly used connection methods for measuring antennas in the mm-wave range, like connectors or probes, influence the intrinsic behavior of the antenna under test (AUT). It is shown that nearby structures supporting the antenna and probe or connector cause strong interference on the measured antenna pattern. A new connection setup is proposed eliminating the interfering signal. This is confirmed by a detailed simulation model and verified with experimental results. Furthermore, the probe radiates significantly due to the discontinuity from the transitions of the probe tip to the microstrip line. This radiation influences the signal-to-noise ratio, i.e., the dynamic range. Measures are proposed to reduce this interference, resulting in an improved signal-to-noise ratio by approximately 15 dB.

This article describes the possible factors that can introduce discrepancies between measurements and three-dimensional EM simulations of millimeter-wave (mm-wave) antennas. The effects of the choice of the simulation solver, the relative permittivity and the homogeneity of the substrate material, the manufacturing tolerance, and the measurement errors are discussed. It is concluded that a fair comparison between measurements and simulations of mm-wave antennas can only be made if all these possible causes of discrepancies are taken into account.

A mathematical analysis of reflector shaping for wide-angle scanning is presented. Parabolic, hyperbolic and spherical reflectors are defined based on geometrical optics method in order to have the smallest deviation of the focused beam (Fig. 1) during wide-angle scanning. It is shown that it is possible to expand the illuminated region of the array by a factor 3 for parabolic reflectors with axial displacement based on an estimated 80 % aperture efficiency at 30 GHz, D/λ=80. Moreover, it is demonstrated that spherical reflector have the smallest deviation from the axis of revolution during wide-angle scanning.

Focal and axial fields of the parabolic and spherical quasi-optical antenna systems are analyzed. The effects of axially displaced focal plane array (FPA) in both systems were investigated. The axially displaced FPA-fed parabolic reflector can broaden the field patterns across the FPA. FPA-fed spherical reflector if carefully tuned along its paraxial line can broaden the field patterns across the FPA as well. The broadening in both systems can results in a larger reuse of the antenna elements in the FPA during beam scanning, hence a smaller FPA size can be utilized. The advantage of the FPA size reduction is that it can reduce the complexity of the FPA feeding-lines and chip-sets integration.

This work describes high-resolution propagation measurements performed as a diagnostic survey in an operational UMTS network. The results were obtained using the measurement system previously presented in. Measurements were performed in a dense urban environment in Amsterdam, the Netherlands. Results showed that the measurement approach can be used to create a setup that is similar to the actual network scenario, and that is capable of accurately identifying the dominant propagation effects while moving through the environment. The results are especially important for mobile-system operators, because they revealed some of the causes of inadequate propagation prediction. This underlined the limitations of propagation-prediction models currently used by most mobile-system operators, and the importance of accurate propagation information to obtain the optimal network configuration.

This letter presents an antenna configuration to achieve a coupling reduction between colocated antennas. Application of an adaptive spatial notch enables this functionality. Analytical results are obtained, which show good resemblance to simulated and measured results, performed on a prototype manufactured to operate around 2.5 GHz. Coupling reduction of 50 dB has been measured. The antenna impedance is also influenced because of this configuration and shows an S11 better than - 15 dB at the frequency of interest. In addition, the radiation pattern of both antennas is influenced. This can be seen as an advantage or a disadvantage, depending on the application.

A balanced antenna design is presented that is tailored to broadband communication in the 60-GHz frequency band. The antenna can be realized in printed circuit-board technology, has a high radiation efficiency and can be used in array configurations. It is modeled with a method-of-moments implementation. The radiation efficiency is analyzed in detail, and design guidelines are given. Moreover, an optimization method is outlined that optimizes both antenna bandwidth and radiation efficiency. The antenna element and a circular antenna array have been realized. Measurements of these antennas are in good agreement with simulated results.

The impact of directional antennas and multiantenna beamformers on radio transmission is formulated in terms of the gain of the Rician -factor, the reduction of the root-mean-squared delay spread, and the gain of the signal-to-noise ratio at the receiver for Rician fading channels in multipath environments. The analysis is based on a double-directional channel model. For the analytical formulation, the joint channel spectrum is assumed to be decomposable into separate spectra in time and angular domains. By way of illustration, closed-form expressions for the impact of hypothetical cosine-shaped antenna patternsand conventional beamformers are derived for channels with uniform angular spectra and an exponential decaying delay spectrum. The impact factors are explicitly related to the antenna beamwidth and the number of antenna elements. In addition, the effect of misalignment between the antenna main beam and the direct path is included in the analysis. The quantitative analysis given in this paper is important for radio system design, particularly for the design of antennas and multiantenna beamformer configurations.

A millimeter-wave antenna is presented that has an adjustable polarization. The polarization can be controlled by the input signal of the antenna and therefore no separate RF switch is needed. A completely planar feed network has been designed that employs branch-line couplers that allow to vary polarization depending on the input signal. The antenna has been realized and the concept of polarization diversity is demonstrated. Measurement results are in agreement with simulated results and validate the performance of the antenna.

This paper presents the results of angle and delay measurements in physically nonstationary radio channels obtained in an outdoor urban environment. The multidimensional estimation data are obtained using a recently developed 3-D high-resolution channel sounder. The estimation results are compared with results obtained from a 3-D deterministic propagation prediction tool. For a better analysis, a hierarchical clustering method is presented that can separate and group the multidimensional estimation data into clusters. Measurements performed at a fixed position as well as along a trajectory are used to characterize the angular dispersion in both azimuth and elevation. The angular dispersion in terms of the rms cluster angular spread in both elevation and azimuth of the different clusters is analyzed over space and time and related to its physical scattering sources. Compared to the measurements, a large number of multipath clusters are missing in the predictions. Furthermore, it is observed from the measurements that different objects cause different angular spread values in azimuth and elevation. The results can be very helpful for the identification, improvement and calibration of deterministic propagation prediction models.

In this letter, it is demonstrated that the dominant multipath radio waves predicted with simple ray tracing show a good match in the time domain with those obtained from complex impulse response measurements along outdoor trajectories. By combining the measured intensities and delays of these dominant multipath components with their angles-of-arrival and angles-of-departure obtained from the ray tracer, good wideband directional channel realizations can be derived.

Wideband channel measurements at the 60-GHz frequency band in a reflective environment with different antenna heights are presented. The log-distance model of the normalized received power (NRP) is used to fit the measured data for both line-of-sight (LOS) and nonline-of-sight (NLOS) cases. Also, the impact of the biconical antennas and the reflective environment on the channel properties is analyzed and explained. Results show that the most favorable NRP values are found in the case that the Tx and Rx antennas are at the same height. Also, in most cases, the scatter paths have more contributions on the total received power than the direct path. In addition, in the LOS case, the NRPs become less dependent on the Tx-Rx separation owing to the combined effect of the antenna and the reflective environment. In the NLOS region, the contribution level of the strongest path becomes less dominant with increasing virtual Tx-Rx separation. The analysis of these results can be instructive for the deployment of a 60-GHz system in a reflective environment.

This paper investigates diversity for dual-antenna systems operating in indoor environments. First, an approximated equation of the diversity gain is derived for different combining techniques. These theoretical results show that the two-term approximation, as generally used in the literature , is too rough an estimate. Consequently, a new six-term approximation is derived. Next, it is demonstrated by a comparison of theoretical and experimental diversity gain values that, due to mutual coupling between the two antennas in practice, the diversity gain will not approach 0 dB if the distance between the two antennas approaches zero. Finally, it is concluded from measurements at 900 MHz that antenna-pattern diversity is a better choice than space diversity for use at handhelds.

This paper presents a model for the scattering of radiowaves from the canopy of a single tree. The canopy is modeled as a cylindrical volume containing randomly distributed and oriented cylinders, representing the branches, and thin disks, representing the leaves. A simple expression for the incoherent scattered field outside the canopy is obtained using Twersky's multiple scattering theory. This expression is shown to agree well with results of scattering measurements on a live tree typical of those found in urban environments. The scattering model can be readily incorporated in ray-based propagation prediction tools that assist the planning of microcellular radio networks. This involves the use of so-called tree-scattered rays, which interact at the tree centers. Path loss predictions generated with the aid of the new model are shown and compared with measured data to illustrate the considerable improvement in prediction accuracy that can be achieved in realistic urban microcellular scenarios by taking into account the scatter from trees.

The modal transmission-line (MTL) method is used to analyze the shielding effectiveness of buildings, which is an important parameter for the accurate planning of microcellular communication networks. For that, the buildings are modeled as multilayer lossy periodic structures. After a description of the extended MTL-theory, the newly developed MTL model is applied to brick walls, reinforced-concrete walls and concrete block walls. From a comparison of the MTL-results with previously published theoretical or experimental results it is concluded that the MTL method is very well suited, because it is accurate as well as computational time efficient.

This paper presents the effect of internal reflections on the beam pattern and input impedance of integrated lens antennas. A silicon lens was designed and manufactured, and measurements were conducted at a frequency of 100 (impedance) and 500 GHz (beam pattern). A frequency-dependence characterization of the beam pattern clearly showed the existence and impact of internal reflections. The measurements confirmed that most of the frequency variations of the beam pattern could be attributed to internal reflections, as predicted by the model. An on-wafer measurement strategy for determining the antenna impedance at millimeter-wave frequencies is presented. The validity of the model was also proven by an excellent match of the input impedance measurements and predictions. Not only the level, but also the oscillation on the impedance curve was predicted accurately. Initial space qualification was performed in the form of thermal cycling.

This paper begins with the modeling of the reflected waves within integrated lens antennas, which consist of a dielectric lens on which a planar antenna is mounted. It is demonstrated that if the relative dielectric constant of the lens is small (/spl epsi//sub r//spl les/4), the single- and double-reflected waves are sufficient to analyze the effect of the internal reflections. For small angles around boresight, these unwanted reflected fields mainly affect the cross-polar far-field pattern, while for large observation angles, both the co-polar and cross-polar patterns are significantly disturbed. It appears that by neglecting the internally reflected field contributions, the beam efficiency may be overestimated more than 10%. In this paper, two types of matching layers are analyzed in order to reduce these unwanted reflections. It is demonstrated that the radiation performances of the integrated lens antennas with optimum-thickness and quarter-wavelength matching layer are almost equal. Even for low dielectric-constant lenses, the beam efficiency can be increased by over 10%. Finally, it is demonstrated that the internal reflections may also have a strong effect on the antenna admittance, which can only be reduced partly by the use of a matching layer.

The accurate planning of microcellular mobile radio networks requires a thorough understanding of the mechanisms that govern radio wave propagation in urban environments. Combined measurements of time delays and angles-of-arrival (AoA's), both in azimuth and elevation, of individual multipath contributions are expected to be very helpful in the validation and improvement of existing ray-tracing propagation models. To this end, we have applied the uniform circular array (UCA)-MUSIC angular superresolution algorithm to complex impulse response measurement data obtained from a synthetic uniform circular array. Beamspace processing and forward/backward averaging were applied to cope with strongly correlated signals. The presented experimental results show that our approach is capable of identifying the dominant multipaths in actual mobile propagation environments

A 3D spherical passive electromagnetic deflector configuration, based on the concept of spatial-feeding, is proposed that modifies the incident electromagnetic energy from the steerable planar antenna array (source) to meet different scenarios and operational requirements. A generalized analytical formulation of the parametric spherical deflector configuration is carried out. The simulation results of the wide angular coverage scenario, using a spherical deflector, for the 60 GHz frequency band are presented.

The effect of amplitude and phase errors on the radiation properties of phased array can be reduced by using a proper calibration scheme. Based on a brief review of microwave phased-arrays we derived the key requirements for a new anechoic millimeter-wave (mm-wave) antenna set-up which was constructed. The residual measurement errors obtained with this new set-up are low enough for the calibration of low-sidelobe mm-wave phased arrays.

High-resolution propagation measurements were carried out to verify the angular and delay dispersion predicted by ray-tracing models. To do the comparison between the measured and simulated results, the corresponding waves should first be identified. This paper introduces a method to find the corresponding relationship of waves automatically. The results show that the algorithm can successfully find the matching simulated and measured waves. It also provides the information to find and further investigate the most dominant propagation mechanisms.

A systematic approach based on ‘package-peeling’ together with time-domain reflectometry (TDR) for package characterization using an EM-tool is presented. The said methodology is applied to investigate and address the possible causes of transmission losses for a measured 60 GHz flip-chipped package, embedding a power amplifier (PA) and a balanced-fed-aperture-coupled-patch (BFACP) antenna with an anisotropic conductive adhesive (ACA) flip-chip interconnection scheme. The proposed technique caters for TDR measurement system limitations and aids in investigation and improving the performance of the millimeter-wave flip-chipped packages.

In this paper, two models to approximately calculate the field distribution in the vicinity of a perfectly conducting finite width screen are discussed. The first model is based on the geometrical theory of diffraction (GTD), and is simplified such that the magnitude of the individual ray contributions can be easily calculated. The second model is based on a graphical approach. Coefficients that are representative for the dimensions of the obstacle and the relative position of the observation point are used together with standardized equations to calculate the field strength in the shadow region behind the screen. Also a modification of the current CCIR procedure for knife-edge diffraction is proposed, such that it can be applied to a finite width screen. Results of all models are compared with more accurate and complex results from a model based on the uniform theory of diffraction (UTD). All models proposed are simple to apply and present an essential extension to currently available engineering models. It is found that the GTD model has the best performance with respect to the UTD approach. The graphical method, however, is more user friendly than the GTD model, because fewer intermediate results need to be calculated. Moreover, the use of this method yields a field-strength distribution for the whole shadow region of the obstacle instead of the field at just a single point. Further, it is found that the modified CCIR approach can also be used with good accuracy. The models discussed answer some questions formulated by the CCIR concerning site shielding, and extend the currently available engineering models for this interference reduction technique.

A design procedure for two types of Fresnel-zone plate antennas is presented: viz. antennas with absorbing/transparent zones and phase-correcting zones. Design objectives are the optimization of the gain of the lens of the antenna and the side-lobe envelope of its radiation pattern. The design rules are derived from numerical simulations.

Using Kirchhoffs diffraction theory, scalar field analyses of two off‐axis focused antenna systems, the Fresnel‐zone plate antenna (FZPA) and parabolic reflector antenna, are presented. Expressions which describe the gain patterns of both antennas are derived and used to examine the scan properties of the two systems and to reveal and discuss similarities and differences between them. The results of the analysis give good insight into future applications of the FZPA as a multibeam antenna. © 1993 John Wiley & Sons, Inc.

A novel approach to solving the temperature stabilization problem of radiometer receivers is discussed, in which the classical temperature stabilization is replaced by a software-based compensation for any local temperature deviations observed. It is shown that a tunnel diode has to be incorporated as a square-law detector in order to validate this new approach. The resulting measurement uncertainty is calculated and an approximation of the effect of aging is given.

The paper starts with a review of calculation methods for determining the complete far-field radiation patterns of reflector antennas. Subsequently, a direct comparison is made between PO, APO, CAPO, GTD, UTD and EEC methods by applying all of these techniques to one and the same reflector antenna configuration. It is shown that both UTD, including surface-diffracted rays, and CAPO is satisfactory for calculating the scattered field from reflector antennas in wide-angle regions (away from the antenna axis). The correct results in both forward- and rear-axial region can be obtained with PO and EEC, respectively. Finally, special attention is paid to the transition angle between EEC and UTD.

An analysis of the radiation properties of the Fresnel‐zone plate antenna (FZPA) and the parabolic reflector antenna (PRA) is presented using the Kirchhoff diffraction theory. Expressions are derived for the vectorial far‐field radiation patterns of both antennas. Some computed co‐ and cross‐polar patterns are shown. The most important differences between the radiation properties of the FZPA and PRA are revealed and discussed. The results of the analysis give good insight into future applications of the FZPA.

—A high-resolution measurement system for the characterization of the delay and angle-of-arrival properties of all significant multipath components on mobile radio channels is presented. The system uses complex impulse response data obtained from a novel 3-D tilted cross switched antenna array as input to an improved version of 3-D Unitary ESPRIT. Results from simulations and measurements show that the approach is capable of accurately characterizing the delay and angle-of-arrival characteristics of the dominant multipath components at moderate urban speeds along a trajectory in mobile propagation environments with high resolution in both azimuth and elevation. Index Terms—Channel sounder, cross arrays, delay estimation, direction of arrival estimation, land mobile radio, mobile communications, radiowave propagation.

Extensive measurements are conducted in room environments at 60 GHz to analyze the channel characteristics for various channel configurations. Channel parameters retrieved from measurements are presented and analyzed based on generic channel models. Particularly, a simple single-cluster model is applied for the parameter retrieval and performance evaluation. By this model, power delay profiles are simply described by a -factor, a root-mean-squared delay spread, and a shape parameter. The considered channels are configured with the combination of omnidirectional, fan-beam, and pencil-beam antennas at transmitter and receiver sides. Both line-of-sight (LOS) and non-LOS (NLOS) channels are considered. Further, to evaluate the transmission performance, we analyze the link budget in the considered environments, then design and simulate an OFDM system with a data rate of 2 Gbps to compare the bit-error-rate (BER) performance by using the measured and modeled channels. Both coded and uncoded OFDM systems are simulated. It is observed that the BER performance agrees well for the measured and modeled channels. In addition, directive configurations can provide sufficient link margins and BER performance for high data rate communications. To increase the coverage and performance in the NLOS area, it is preferable to apply directive antennas.

A planar beam-forming antenna array is proposed that operates in the 60 GHz frequency band. The array consists of 6 balanced-fed aperture-coupled patch antenna elements [2] that are placed in a circular configuration. The resulting array has a maximum gain of 14 dBi and a 3 dB scan range of ±50 degrees. To demonstrate the performance, test arrays have been implemented with accompanying feed networks that apply the appropriate phase distribution over the array for beam-forming at several specific scan angles. Measurements validate the proposed array configuration. (6 pages)

The results of propagation measurements in an outdoor urban environment using a recently developed 3-D high-resolution channel sounder are analysed. Measurements are performed at a fixed position as well as along a trajectory to characterise the angular dispersion in both azimuth and elevation. A clustering algorithm is used to separate and group the estimated multipath components. The rms cluster angular spread in both elevation and azimuth of the different clusters is analysed over space and time and related to its physical scattering sources. (5 pages)

This paper presents the results of angle-delay measurements in physically nonstationary radio channels. The multidimensional estimation data are obtained using a recently developed 3-D high-resolution channel sounder. For a better analysis, a hierarchical whole clustering method is presented that organizes the multidimensional estimation data into clusters. Furthermore, estimation results are compared with results obtained from a 3-D deterministic propagation prediction tool. The clustering method proposed here was successfully applied to multi-dimensional estimation data. The results show that it is vital to cluster these data in order to be able to correctly interpret the measurement results. Compared to the measurements, a large number of multipath clusters are missing in the predictions. Furthermore, the multipath clusters obtained from the measurement data tend to have larger time and angular spreads than predicted.

This paper analyzes the frequency selectivity, which is caused by multipath effects, of indoor line-of-sight (LOS) and non-LOS (NLOS) channels based on channel measurements in the frequency band of 60 GHz. The coherence bandwidth is determined to characterize frequency selectivity figures of the channels employing the combination of omnidirectional, fan-beam and pencil-beam antennas at transmitter (TX) and receiver (RX) sides. The results quantitatively show how far directional configurations are more effective for combating multipath effect than the omnidirectional ones for LOS channels. The frequency selectivity of the fan-beam-to-fan-beam configuration is less sensitive to misaligned TX-RX beams than the fan-beam-to-pencil-beam one. In addition, when omnidirectional antennas are used at both TX and RX side, the frequency selectivity of a NLOS channel is less sensitive to the TX-RX height difference than that of a LOS channel. Moreover, coherence bandwidth is empirically related to root-mean-squared delay spread. Lastly, the results presented in this paper lead to some useful insights into antenna configurations and beamformer designs for a 60-GHz radio system.

A key problem in high-resolution multidimensional parameter estimation via unitary ESPRIT is to jointly solve a set of invariance equations by means of least-squares minimization. It has been shown previously that existing least-squares techniques fail when applied to the category of cross arrays, which consist of perpendicular uniform linear arrays crossing at the center of the array. Cross array geometries are of special interest because they provide a larger aperture and, hence, better resolution for a given number of array elements than other multidimensional uniform array geometries. This letter proposes an improved structured least-squares method that enables successful application of unitary ESPRIT to cross arrays. Results of simulated direction-of-arrival estimation experiments using a three-dimensional cross array indicate that considerable performance improvements can be achieved if the new method is used.

To study the radio propagation channel fading at 60 GHz, a 3D ray-tracing simulator is used to predict the wave propagation deterministically in a small indoor environment. Starting from the instantaneous received signals, the large-scale and small-scale fading of the line-of-sight and non-line-of-sight channels are analyzed and modeled for linear and circular polarized antenna schemes. It is shown that the large-scale fading can be well modeled by a lognormal distribution and the small-scale fading by a Rician distribution. Additionally, the multipath dispersion in time and space is analyzed by mapping the multipath waves into delay and angular domain. The analysis shows that the beamwidth of the TX-RX beams can be properly adjusted to reduce the multipath effect to a certain extent, which will provide useful information for designing 60-GHz systems with smart antennas.

The fixed channel assignment problem in GSM networks has been commonly modelled as a constraint satisfaction problem with binary channel separation constraints (graph-colouring model). However, it has been observed that heuristics using direct estimations of carrier-to-interference ratio (CIR) have several advantages over those using binary constraints, being the economisation of spectrum the most important one. This is due to the fact that CIR constraints provide the possibility of taking more accurately into account different propagation phenomena that directly impact the channel assignment plans. In this paper, we present further improvement to an existing CIR-constraint heuristic algorithm for fixed channel assignment. We demonstrate that accounting for the change of the propagation coefficient at the break point in line-of sight conditions (commonly seen in urban environments with rectangular grid street plans) might further economise spectrum. Results of practical examples are included.

In this paper the scan properties of integrated lens antennas with a quarter-wavelength matching layer are analyzed. For beam scanning on and within a cone, optimum feed positions are determined. It appears that for beam scanning on a cone the elliptical lens is the best choice if a small scan angle is required while the extended hemispherical lens should be used in case of a large scan angle. For beam scanning within a cone it is recommended to select an elliptical lens if a large average directivity is required while the extended hemispherical lens appears to be the best choice if a small variation in the directivity is important.

This paper describes the wideband measurements conducted at the frequencies 58 GHz and 2.25 GHz in an indoor environment. Normalized received power (NRP) and root-mean-squared (RMS) delay spread are calculated and used to compare the characteristics of radio wave propagation in both line-of-sight and non-line-of-sight areas at the two frequencies. The results show that on top of the difference in free space, the NRP at 58 GHz is several dBs lower than at 2.25 GHz in average. This difference is also reflected in the fitted log-(virtual) distance NRP models. In the deep shadow region, the poor diffraction level at 58 GHz will reduce the power level, but meanwhile the reflected waves from walls have a strong contribution to the received signal. In addition, it is observed that the radio channel at 58 GHz shows much less time dispersion in terms of RMS delay spread. The results can be quite useful for the 60 GHz system design, which might be very different from the design of conventional systems which operate in the lower frequency bands

This paper presents a model for the propagation of radiowaves through buildings. The model can be used as a seamless extension to ray-based propagation prediction models that only consider external reflection and diffraction, as do most current models. This involves the use of so-called transmitted rays, which are traced through building walls. Outdoor-to-indoor propagation (building penetration) is automatically taken into account as a "by-product". The transmission model requires no information about each building's interior other than a specific attenuation factor that describes the global behavior of the field inside the building. This coefficient can be determined for individual buildings by measuring the excess loss associated with the propagation path through the building. It is shown, however, that no large errors are to be expected if all buildings are characterized by the average of the empirical values obtained in this study, at 1.9 GHz. Path loss predictions generated with the aid of the new model are shown and compared with measured data to illustrate the considerable improvement in accuracy that can be achieved in realistic urban microcell scenarios by taking into account building penetration and transmission.

The benefits of employing antenna array processing for the interference limited UMTS system is the increase in the number of simultaneous users and the reduction in the transmitted uplink power. The joint power control and antenna processing offers maximum achievable capacity with lower transmission powers for the given target SINR (signal-to-interference+noise ratio). The analysis about possible achievements using antenna array processing, varying parameters such as the number of users in a microcell, processing gain and antenna array size for the given target SINR, has been done using a deterministic ray tracing model developed for urban microcells and considering two antenna processing cases, OC (optimum combining) and MRC (maximum ratio combining). The paper shows that the ratio between the target value and the processing gain is the most dominant factor for the antenna array performance in the power controlled environment, and that optimum transmitted powers obtained using OC are the least sensitive to the increase in the number of users, as compared to MRC and simple decorrelation on a single antenna element.

A new variety of the Fresnel zone planar lens with enhanced focusing quality is proposed. Each full-wave zone is divided into four quarter-wave subzones, which are covered by dielectric rings having equal thickness but different permittivities. Based on this planar lens configuration, a transmissive-type Fresnel-zone antenna for DBS-reception with more than 50% aperture efficiency is developed and examined theoretically. >

A comparison is made between wideband angle-of-arrival measurements obtained in two urban microcell environments in Switzerland and predictions generated by a two-dimensional ray-tracing based propagation prediction model. In general, theoretical and experimental results show a reasonable agreement. It is demonstrated however that in some particular situations transmission through buildings and scattering by vegetation can be the dominant propagation mechanism.

The paper presents the results of signal strength measurements at 1800 MHz in four office buildings in The Hague, illuminated by an outdoor base station with an antenna above the rooftop. The objectives of these experiments are to study the behavior of the received signal strength at different floors of a building and to determine the main characteristics concerning cell coverage, namely, signal attenuation and variation within these buildings. It is shown that large fluctuations occur between average signal levels in line-of-sight (LOS) and non-LOS areas of multifloor buildings.

In 3G mobile communication systems, smart antenna processing is seen as a powerful tool to combat directional interference. We derive the statistics of the signal-to-interference-plus-noise ratio (SINR) achieved by the combined RAKE receiver-smart antenna processing for the case where thermal noise is the only source of interference, and for the case of another interfering user. The results are based on the output of two channel models with disjoint approaches: deterministic ray-tracing model /spl mu/Fipre and the stochastic wideband directional channel model (WDCM).

A comparison is made between the measured and theoretically predicted field strength in the shadow region of a lossy dielectric obstacle. The field is measured along a cylindrical arc behind the obstacle at a frequency of 50 GHz. The theoretical model uses the uniform theory of diffraction including corner, edge-to-edge, and edge-to-corner diffraction, heuristically extended to include effects of nonperfect conductivity. The agreement between the measured and theoretically derived results is excellent for both orthogonal polarisations considered. The field behind a lossy block-shaped obstacle proves to be less polarisation dependent than behind a perfectly conducting one.

An approximate formula is derived for the on‐axis cross‐polarization discrimination (XPD) of a symmetrical reflector antenna with random surface errors. This XPD depends on only two parameters, namely, the normalized r.m.s. surface error (ϵ/λ) and the polarization‐loss efficiency (n).