Receiving Antenna Pattern Research Articles

Estimation of elevation-dependent satellite antenna phase center variations of GPS satellites

A method for the estimation of the phase center variations of GPS satellite antennas using global GPS data is presented. First estimations have shown an encouraging repeatability from day to day and between satellites of the same block. Thus, two different satellite antenna patterns for Block II/IIA and for Block IIR with a range of about 4 cm and an accuracy of less than 1 mm could be found. The present approach allows the creation of a consistent set of receiver and satellite antenna patterns and phase center offsets. Thereby, it is possible to switch from relative to absolute phase center variations without a scale problem in global networks. This changeover has an influence on troposphere parameters, reduces systematic effects due to uncorrect antenna modeling and should diminish the elevation dependence of GPS results.

Sidelobe Contamination in Bistatic Radars

Abstract The problem of sidelobe contamination in a bistatic network is explored. The McGill bistatic network consists of one S-band Doppler radar and two low-gain passive receivers at remote sites. Operational experience with the bistatic network indicated many cases in which sidelobe contamination seemed nonnegligible. To confirm these findings a sidelobe simulation model was constructed. Comparison between simulations and actual data showed a good reproduction of the observed effect, with differences explained by uncertainties in both transmitter and receiver antenna patterns. It is also shown that this effect may have damaging consequences in Doppler fields in both convective and stratiform precipitation events. An index of contamination is introduced to detect areas of low-quality data.

Investigations on radio propagation channel measurements at 2.2 GHz and 3.5 GHz for the fixed wireless access in an urban area

Within a competitive context the wireless local loop is emerging as an alternative to the traditional wireline network. This solution is attractive because of its low capital cost and its flexible deployment. Nevertheless a propagation channel study has to be performed so as to develop specific engineering tools and propagation models. This paper presents wideband propagation measurement results carried out in Mulhouse in a small cell environment at 2.2 GHz and 3.5 GHz. Under different propagation scenarios, the propagation channel is characterised in terms of path loss and wideband selectivity parameters. Because of the experimental setting, the influence of the receiving height, the frequency and the receiving antenna pattern on the deviations of the path loss and the selectivity parameters have been investigated.

A generalized Doppler power spectrum for wireless environments

We provide a direct derivation of a generalized Doppler power spectrum of the signal received by a mobile station traveling at a constant velocity. The derivation uses the three-dimensional (3-D) incident radiation intensity and the receiving antenna pattern to obtain an expression for the generalized power spectrum which is useful in environments where the 3-D propagation characteristics of wireless signals must be taken into consideration. A special case of radiation confined to a plane is considered to obtain the power spectrum given in the book written by Jakes (1974).

G/T predictions of communication satellites based on a new earth brightness model

AbstractThe G/T predictions of communications satellites in the past usually stipulated that an antenna noise temperature of 290 K be used in the calculations. This, when compared to in‐orbit derived data, has resulted in large discrepancies (up to 3 dB). These discrepancies result directly from the use of a pessimistic value of the antenna noise temperature. The actual antenna noise temperature is lower because a portion of the spacecraft receive antenna pattern falls in deep space and because the brightness temperatures of large parts of the Earth are lower than 290 K. This discrepancy has become more apparent as technology of low noise amplifiers advances, thus making the antenna temperature the predominant factor when budgeting the system noise temperature of the spacecraft.This paper focuses on a model to determine the antenna noise temperature and especially how this model was directly verified in orbit during the acceptance campaign of EUTELSAT II‐F6 (Hot Bird 1). The methodology used for the determination of the integrated antenna temperature is also fully discussed. Full results are also presented.

Polarisation and ground effects on HF receiving antenna patterns

On etudie le comportement d’antennes a la reception d’ondes decametriques ayant transite par voie ionospherique. On determine d’abord les caracteristiques de la polarisation des ondes incidentes ; puis on calcule, en tenant compte du phenomene de reflexion sur le sol, l’amplitude du signal disponible a la sortie d’antennes filaires petites devant la longueur d’onde. Les resultats presentes sous forme d’abaques montrent la grande importance de la localisation de la station de reception et de la geometrie de la liaison par rapport a la direction du champ magnetique terrestre. Ces resultats peuvent etre utilises pour mieux adapter les antennes aux modes de propagation ionospherique.

Heterodyne mixing efficiency for detector arrays

Monostatic radar equations are reported for laser-transceiver sensors that employ coherent optical detection over a linear-array photodetector. Explicit results are presented illustrating the impact of transmitter and receiver antenna patterns on the heterodyne mixing efficiency achieved by each detector element.

A Computer Model to Evaluate Airborne Receiver Performance in Interference Environments

A computer model is described to evaluate airborne radio performance in a mixed environment of friendly and hostile emitters. A new performance criterion, the communications operability volume, is introduced. This criterion permits operational, scenario-based comparisons of various radio designs over a range of interference environments. Communications operability volumes can be calculated for different waveforms, receiver antenna patterns (including adaptive arrays), and detection thresholds. An empirical propagation algorithm is used to calculate path losses and/or maximum communications range. The computer model provides several types of graphic outputs that are used to compare antijam or electromagnetic compatibility performance for different radio designs at various locations relative to the sources of interference in a scenario.

The Design and Planning of Feeder Links to Broadcasting Satellites

A feeder link is the portion of a broadcasting-satellite system which provides the connection from the earth to the broadcasting satellite. Quality objectives for feeder links are normally well above the corresponding objectives for downlinks. The parameters which affect signal quality are examined. It is shown that the greatest control over the C/N ratio lies with the selection of suitable values for the diameter of the feeder link transmit antenna and the power of its associated transmitter. Three mechanisms are available to combat interference between feeder links: discrimination resulting from the feeder link transmit antenna pattern, discrimination derived from the satellite receive antenna pattern, and discrimination due to the use of cross-polarized signals. The use of these mechanisms to create a workable feeder link plan is developed in the paper. There are a number of desirable objectives that can be established for a feeder link plan in addition to the obvious need to meet signal quality ( C/N ) and interference ( C/I ) requirements. A realizable set of objectives is presented along with the approaches used at the ITU Region 2 planning conference to create a satisfactory plan. The technical parameters which must be agreed on in order to develop a feeder link plan are summarized, and the values chosen for the Region 2 plan are presented.

Spatial Filtering Radio Astronomical Data: One-Dimensional Case

Radio astronomical measurements of radio brightness are made by pointing an antenna at a regular array of points in the sky and measuring the received noise power at each point. In the absence of receiver noise, the measured brightness is the convolution of the true brightness distribution with the antenna effective area (i.e., receiving power pattern), evaluated at the point of observation. Front-end noise in the radiometer receiver adds fluctuations inversely proportional to the observing time at each measured point. From such data, we calculate optimum mean-square estimates for two quantities: measured brightness between observations, and true brightness at and between observations. The first is interpolation; the second, called restoration, partially deconvolves the antenna pattern from the measured data. We determine the errors associated with each, as functions of: (1) receiving antenna pattern, (2) separation between observations, and (3) radiometer output signal-to-noise ratio. These results permit the construction of maps of measured and true brightness, with known mean-square errors. In this paper we study the one-dimensional version of this problem, assuming a large number of measured points. We find that measured points should be separated by about half the (full) 3-dB beamwidth for conventional antennas. Restoration is more costly than interpolation.

MMSE Equalization of Interference on Fading Diversity Channels

Adaptive equalization is used in digital transmission systems with parallel fading channels. The equalization combines the diversity channels and reduces intersymbol interference due to multipath returns. When interference is present and correlated from channel to channel, the equalizer can also reduce its effect on the quality of information transfer, important applications for interference cancellation occur in diversity troposcatter systems in the presence of jamming, diversity high frequency (HF) systems which must cope with interfering skywaves, and space diversity line-of-sight (LOS) radio systems where adjacent channel interference is a problem. In this paper we develop the general formulation for minimum mean square error (MMSE) equalization of interference in digital transmission diversity systems. The problem formulation includes the use of available receiver decisions to assist in MMSE processing. The effects of intersymhol interference are included in the analysis through a critical approximation which assumes sufficient processor capability to reduce ISI effects to levels small enough for satisfactory communication. The analysis also develops he concept of additional implicit or intrinsic diversity which results from channel multipath dispersion. It shows how the MMSE processor sacrifices diversity to suppress interference even when the interference arrives in the main beams of the receiver antenna patterns. The condition of near synchronous same-path interference is also addressed. Because the spatial angle of arrival of the interference may result in delay differences between interference signals in different antenna channels, interference delay compensation may be required. We show that this effect is compensated for with a small number of appropriately spaced equalizer taps.

Transmit versus receive gains for microwave dish antennas

For the microwave dish antennas, the antenna gain when transmitting can be different, and is usually less, than that of the same antenna when receiving. The theory of the far field transmit and receive antenna gains is developed for the classical dish as well as for the general case. Aperture functions are derived for use in the integral form of the Fraunhofer diffraction equation. Both the aberration effects of the dish and the angular distribution of the feed are taken into account. Calculations of transmit and receive antenna patterns and gains are compared for the f/1 classical dish for various amounts of feed spillover.

Transhorizon Propagation Measurements From a Simultaneous; Frequency and and Angle Scan Experiment

An analysis of data from three sets of experiments in transhorizon microwave propagation is presented. In each set, a 3‐Gc/s signal was transmitted over a 163‐km path, and the wave arriving at the receiver was examined using a rapidly scanning phased‐array antenna. In one mode of operation, transmitter and receiver were synchronously swept over a 20‐Mc/s frequency band. The results show considerable variability in all quantities derived from the data.Received power patterns on occasions were scarcely broader than the receiving antenna pattern and at other times showed considerable power arriving off the great‐circle bearing. A classification of such patterns into "stable” and “ unstable” showed no strong association with time of day. Signal level distributions were often, but by no means always, of the Rayleigh form. The time lag required for the signal autocorrelation to drop to 0.5 — indicative of fading period — varied from a half second to a few seconds. A similar measure of transmissable bandwidth — in terms of frequency correlation — showed a variability from 1 or 2 Mc/s to more than 20. The interrelationship between all these quantities, and their connection with meteorological parameters, showed interesting individual relationships but no clear‐cut overall pattern, except for a general increase in signal level associated with pronounced inversions.In comparison with various atmospheric models, it becomes obvious that no single simple model is sufficient. On some occasions the received signal showed characteristics predicted from the theory of incoherent scatter by turbulent eddies: distorted angular response patterns with an average beam broadening, Rayleigh‐type signal level distribution, a modest fading rate, and limited transmissable bandwidth. On other occasions, the records showed evidence of marked atmospheric stability and stratification: unbroadened and undistorted antenna response patterns, a more restricted and non ‐ Rayleigh signal level distribution, variable fading rates, and extremely wide bandwidths. There are still other cases where these associations are not well defined.

Measurement of the effect of irregular terrain on VHF and UHF directive antenna patterns

Measurements of antenna patterns of directive antennas were made while driving around transmitters at relatively constant distances of 0.4, 10, and 30 miles. The transmitting antennas for pattern measurement were located at Fort Dix, N.J., and operated at frequencies of 49, 141.75, 239, and 460 mc. The receiving antennas used for recording were ground-plane antennas mounted on a retractable mast in the mobile recording unit and could be operated as high as 30 feet, road obstacles permitting. Because of the great number of wires and trees over the road, most measurements were made at 12 and 15 feet. In addition to the measurements made around the transmitters, receiving antenna pattern measurements were made at spot locations around the transmitter with a 460-mc corner reflector antenna.