Monopulse System Research Articles

SUM AND DIFFERENCE MULTIPLE BEAM MODULATION TRANSMITTED BY MULTIMODE HORN ANTENNA FOR INVERSE MONOPULSE DIRECTION-FINDING

The sum and difference multiple channels were usually applied to the monopulse system only in a receiver. But this paper presents a technique of multiple beam modulation transmitted by the sum and difference multiple channels. The modulated field is designed as three chip signal vectors whose sum and whose differences are controlled by the gains of antennas,and the angle between the sum vector and the differential vector depends on the phase error between the channels so that the different microwave signals can be transmitted in the different directions. A receiver with single-antenna can extract azimuth and elevation with respect to the transmitter. Simulation results show that the proposed modulation system has been successfully designed to integrate digital communication with direction-finding in the way of the reverse monopulse.

주파수 가변 비동기 모노펄스 시스템의 모노펄스 기울기 교정

본 논문에서는 주파수 가변 비동기 모노펄스 시스템에서 추정각 변화량을 최소화하기 위한 모노펄스 기울기 교정 방법을 제시하였다. 이를 위해 우선 안테나 및 RF 수신기의 수신 채널간 이득 및 위상 불균형에 의한 모노펄스 기울기 특성을 분석하였고, 안테나를 포함한 RF 수신기의 채널간 이득 및 위상 불균형을 최소화하기 위한 교정 방법을 제시하였다. 또한, IF 수신기의 채널간 상대 이득 불균형에 의한 영향을 최소화하기 위해 채널 절체를 통한 교정 방법을 제시하였다. 제시된 방법들에 의한 교정 결과, 주어진 주파수 대역폭 내에서의 측정된 평균모노펄스 기울기는 -0.96이 되었으며, 추정각 변화량은 이론값과 유사한 방위각 <TEX>${\pm}2^{\circ}$</TEX>에서 최대 <TEX>$0.15^{\circ}$</TEX>, 방위각 <TEX>$0^{\circ}$</TEX>에서 최대 <TEX>$0.03^{\circ}$</TEX>가 되었다. In this paper, we propose the calibration method of monopulse slope to minimize the variation of angle estimate in frequency agile noncoherent monopulse system. We analyze the monopulse slope characteristics of antenna and RF receiver including the phase and gain imbalances of each receiving channel and present the calibration method to minimize the phase and gain imbalances of RF receiver channels including antenna. In addition, we present the calibration method using channel switching to minimize the gain imbalance of IF receiver channels. The measured average monopulse slope within the frequency bandwidth is -0.96, the maximum variation of angle estimate is similar to theoretical value, <TEX>$0.15^{\circ}$</TEX> at <TEX>${\pm}2^{\circ}$</TEX> azimuth and <TEX>$0.03^{\circ}$</TEX> at <TEX>$0^{\circ}$</TEX> azimuth.

Interleaved thinned linear arrays

This paper presents three approaches to improving the efficiency of an array aperture by interleaving two arrays in the same aperture area. The interleaved arrays have aperiodic spacings that are integer multiples of a set minimum spacing and are optimized to reduce the maximum sidelobe level. Fully and partially interleaved sum arrays operating at the same frequencies are demonstrated as well as interleaved sum and difference arrays for a monopulse system. A genetic algorithm is used to optimize arrays of isotropic point sources as well as arrays of dipoles modeled using the method of moments. Narrow beamwidths are possible while avoiding high sidelobes. The available aperture area is efficiently used.

Design considerations for a real-time random-noise tracking radar

Random-noise radar has been applied successfully to range measurement, velocity estimation and terrain/target imaging. For applications involving stationary targets, long integration times and process averaging are easily tolerated. In situations where the target or radar platform moves at high speed, the impact of this relative motion on system design should be considered. This work addresses the statistical performance of a generic random-noise radar receiver and examines the inter-relationships between design parameters and performance tradeoffs. Complementing this examination, a random-noise monopulse system is also investigated as a possible architecture for real-time angle estimation. Simulations and numerical illustrations provide the basis of processor design and performance prediction.

Tripulse: A system for determining orientation and attitude of a satellite borne active phased array

Tripulse is a novel system that is designed to accurately estimate the orientation of a satellite borne phased array relative to one or more Earth stations. It has conceptual similarities to amplitude comparison monopulse systems used in tracking radars. Tripulse differs from monopulse in that it is applicable primarily to transmitting active phased arrays aboard communication satellites. The signaling structure consists of a minimum of three separate time multiplexed coherent pulses. A statistical performance analysis and a description of the methodology for converting multiple ground station orientation data to attitude estimates are presented.

Twin Vivaldi antenna for transponders and monopulse systems

Twin Vivaldi antenna for transponders and monopulse systems

Twin Vivaldi antenna for transponders and monopulse systems

Twin Vivaldi antenna for transponders and monopulse systems

Millimeter-wave atmospheric turbulence measurements: Instrumentation, selected results, and system effects

Increasing interest in and greater usage of the millimeter-wave frequency bands has resulted in a need for better characterization of atmospheric effects at these frequencies. While attenuation is recognized as the most significant effect, recent measurements of fluctuations in intensity and phase caused by atmospheric turbulence have shown that these phenomena will also degrade system performance at both millimeter-wave and microwave frequencies. This paper describes the millimeter-wave and meteorological instrumentation used to make these measurements and gives selected results. It is determined that phase fluctuations as great as 1.5 radians and intensity fluctuations as large as 2.8 dB are observed over a 1370 m path in hot, humid weather. The effects of these fluctuations on the performance of practical, existing microwave phased array and monopulse systems are assessed. It is determined that phase fluctuations in particular will degrade the performance of microwave adaptive nulling arrays and monopulse trackers.

Modeling of a monolithic slot ring quasi-optical mixer

This paper describes the design and modeling of a quasi-optical monolithic mixer system. An integrated slot-ring element with two Schottky-Barrier diodes acts simultaneously as an antenna, and as a mixer. A nonlinear analysis has been performed of the mixer function. The slot-ring element receives RF and LO power through a hyper-hemispherical lens. This lens is also analyzed and radiation patterns are calculated, which are in good agreement with measurements. The results in this paper indicate that quasi-optical monolithic monopulse systems in the millimeter wave range, based on four slot-ring elements and a hyper-hemispherical lens, should have excellent performance.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Measurement distance requirements for both symmetrical and antisymmetrical aperture antennas

Universal curves giving the main-lobe reduction and the first sidelobe level change versus the measurement distance are furnished for various aperture distributions. The widely used Rayleigh 2D/sup 2// lambda distance criterion (where lambda is the radiated wavelength and D is the distance to the antenna) is shown to be unsatisfactory, since the minimum measurement distance depends both on the aperture distribution and on the specific far-field parameter under measurement. It is found that, in order to measure accurately the pattern of antennas with ultralow sidelobes, a measurement distance much greater than the Rayleigh one is needed. Such a distance is more than safe for measurement of the antenna gain and antenna patterns with moderate sidelobe level, but it is greater than necessary to measure the principal parameters of interest in a monopulse system. This latter conclusion is in full agreement with reported experimental results. Some experimental results concerning a monopulse antenna reported.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Monopulse Resolution of Interferometric Ambiguities

Ambiguities in interferometers with high angular accuracy must be resolved to achieve a practical system design. A new technique for ambiguity resolution is described and is based on monopulse circuitry used with the interferometric elements. The overall angular accuracy of the system is achieved by the interferometer; the angular accuracy of the monopulse subsystem is used to resolve interferometric ambiguities. An expression for the probability of correct ambiguity resolution is derived as a function of element size and monopulse accuracy which indicates that high probability of ambiguity resolution results when the size of the interferometric elements are a fraction of the interferometric baseline. Finally, a comparison between conventional monopulse and interferometric system designs is made for the three principal parameters, signal sensitivity, angular accuracy, and field of view, that dictate the appropriate choice for a particular application. Interferometric systems are more appropriate than monopulse systems for those applications in which angular accuracy and field of view are more important than signal sensitivity.

The Average Response of a Monopulse System to Three Steady Targets

The Average Response of a Monopulse System to Three Steady Targets

Multipath Effects on an Azimuthal Monopulse System

The first topic considered is an analysis of the conditions under which the conventional definition of length of the glistening surface, as given by Beckmann and Spizzichino, is not valid. For some conditions, significant amounts of incoherent scattered power can be received from areas beyond the conventional length. A second topic is the investigation of the effect on azimuthal angular tracking accuracy due to such scattering factors as shadowing, surface height distribution, standard deviation in surface height σ, surface correlation length T, unevenness and inhomogeneity of the terrain, antenna heights, and signal polarization. A number of interesting results have been observed. The amount of additional incoherent power not included under the conventional definition depends on the ratio σ/T, except for the case where both transmitter and receiver are very close to the surface. The trends in the behavior of the glistening surface are similar for vertical or horizontal polarization, for Gaussian or exponential surface height distributions, and for different signal frequencies in the S-band to L-band range.

Comparative analysis of a phase and an amplitude processor for amplitude monopulse systems

The theoretical performance of an amplitude monopulse processor is compared with that of a phase monopulse processor in the presence of thermal noise. Both processors use the sum and difference beam antenna model. Both processors exhibit a bias error at signal-to-noise ratios below 20 dB. The phase processor demonstrates a smaller standard deviation in the angle estimate for target angles in the vicinity of the monopulse boresight.

Theoretical determination of the effects of multiple scattering by hydrometeors in monopulse systems at millimeter wavelengths

The incoherent radiation incident on a receiving antenna after having been scattered by raindrops can cause some problems in the case of a monopulse system whose directive pattern presents a deep null toward the coherent incoming wave. This null is then filled with incoherent radiation, therefore giving rise to a degradation of the performances of the measuring equipment. In this paper this degradation is theoretically assessed assuming a simplified geometry (a rain cell embedded in stratified rain); the drops are assumed to be of spherical shape, and typical system configurations for the earth station are considered.

On Conopulse Radar Theoretical Angle Tracking Accuracy

The Cramer-Rao analysis method is applied to a conopulse radar to determine a lower bound on the variance of angle tracking error. The analysis allows the calculation of the variance independent of the form of the signal processor attached to the antenna. Under reasonable assumptions it is found that angle error variance is larger than that of a similar monopulse system by a factor of 2.

Multipath Fluctuation Effects in Track-While-Scan Radar

A theoretical model of diffuse multipath reflections from rough surfaces is applied to the prediction of multipath power distribu tions in radar coordinates: elevation angle, time delay, and Dop pler frequency. These distributions are used to predict radar tracking errors in elevation angle, for both monopulse and scan ning antenna systems, and typical results are presented. These show a small increase in tracking error for scanning systems, on radially approaching targets, caused by sensitivity of these trackers to amplitude scintillation of the composite direct-plus multipath signal. Effects of knife-edge diffraction and of vegetation ion are briefly considered.

Antenna and other systematic effects on amplitude comparison monopulse systems

The paper discusses, both mathematically and systematically, a typical 4-port equispaced (over 360°) antenna amplitude-comparison direction-finding system which operates over a wide microwave bandwidth. System components are examined in terms of their effect on performance and methods for reducing errors are discussed. A simple example of using a stored-calibration process is presented and it is shown that errors in measuring bearing can be reduced by at least 20% when using stored-calibration methods.

Conopulse Radar

The methods usually adopted for implementing an angle-tracking radar are monopulse and conical scan. A monopulse system is free from target-signal amplitude-fluctuation effects, in principle, but usually requires three channels of receiver equipment. A conical scan system, on the other hand, requires only a one-channel ceiver, but is subject to target-signal amplitude-fluctuation effects. This paper describes and analyzes a hybrid system called conopulse that requires only two receiver channels and is free of target-signal amplitude-fluctuation effects. Part of the signal processing in a conopulse system uses conical scan techniques and part uses monopulse methods. The principal advantages of conopulse are that it has the monopulse freedom from angle errors caused by target fluctuations and that it requires less receiver equipment than monopulse to achieve this freedom. Its main disadvantages are its lower data rate and the practical problems associated with the required antenna feed, which is somewhat similar to but more complicated than conical scan.

Thermal Noise Errors in DF Monopulse Systems Having Log Amplifiers

An analysis of the effects of thermal noise on the accuracy of direction finding (DF) monopulse systems which employ logarithmic amplifiers is presented. Numerical results are presented which indicate that a simple model may be used to compute rms thermal errors for a wide range of signal levels. Analytical results obtained in the limit of large signal-to-noise ratios are compared with standard results used to analyze monopulse systems employing automatic gain control (AGC) circuitry instead of log amplifiers.