The Losses Due to the Error in Estimating the Velocity in Clutter-Locking MTI Systems

The losses due to the statistical error inherent in estimating the mean clutter velocity by averaging over a limited number of range cells are derived. These results show that an accepted intuitive approach leads to a significant underestimation of the number of range cells required. Suggestions are made for reducing these losses.     

Thermal Noise in Amplitude Comparison Monopulse Systems

In this paper we consider the problem of estimation of angle of arrival in an Amplitude Comparison Monopulse antenna arrangement with the explicit inclusion of internally generated thermal, i.e., receiver, noise as an interference to the desired measurement. A pulsed type radar is assumed, and an ideal (i.e., point) radar target is postulated. This latter restriction is made so that consideration of the effects of target scintillation, glint, or other external random phenomena can be excluded from our treatment of the problem. In this context, a maximum likelihood analysis is made to determine the form of the estimate of angle of arrival, and the probability density function (pdf) of this quantity is computed. The form of the estimate is found to be a ratio of Gaussian variables quite like that used in conventional monopulse signal processing. The pdf obtained for the estimate is believed to be new, and it serves to emphasize the bias and indeterminate variance effects associated with this type of nonlinear signal processing. Some useful approximations to the pdf are discussed, and a unit of precision for the estimate is defined.     

Correlation Effects of MTI Filters

A frequency domain approach for determining the effective number of independent pulses at the output of a square law detector in a moving target indicator (MTI) system leads to a definition which gives the same asymptotic results as given by a previous definition.     

Quantization Noise in Digital Moving Target Indication Systems

This paper deals precisely with the effect of quantum or step size in an analog-to-digital converter on the quantization noise in the output of MTI (moving target indication) radar processors. The correlation between quantization errors on successive pulses is considered in the analysis and is shown to have a small quieting effect on the output quantization noise.     

Digital Communication Systems in Impulsive Atmospheric Radio Noise

Analyses are presented of the performance of binary and M-ary coherent and noncoherent communication systems operating in the impulsive atmospheric radio noise environment. The receiver is usually a maximum likelihood detector for white Gaussian interference and therefore has the form of a parallel bank of matched filters followed by decision circuitry. By employing a Poisson or generalized Shot noise model for the impulsive noise with a suitable probability density function (pdf), closed-form expressions and bounds of error probabilities for M-ary noncoherent and coherent amplitude-shift keying (ASK), phase-shift keying (PSK), and frequency-shift keying (FSK) systems are obtained and the results discussed.     

Noise and Transmission Delays in Mutual Synchronization Systems

This paper considers the effects of noise and transmission delays in a phase-averaging mutual synchronization system. The basic analytical ideas are developed with respect to a two-station system which contains first-or second-order analog phase-lock loops. From the equation describing the phase error dynamics of each system, a generalized Fokker-Planck equation is derived. It is used to obtain a good approximate analytic expression for the phase error probability density function (PDF), which is confirmed by simulation. An important quantity for such mutual synchronization systems, under random disturbances, is the variance of the frequency deviation. This may be obtained directly from a knowledge of the phase error PDF. The above development is then extended to a mutual synchronization system of arbitrary size.     

FM Laser Noise Effects on Optical Doppler Radar Systems

A detailed analytical study is made of the effect of FM noise on a laser carrier frequency which is used in a Doppler radar. Both long-term drift and short-term FM noise are considered. The case of high modulation index of the noise is permitted by the theory. Forward as well as slanted beams are examined. Curves have been calculated for each case to allow rapid estimates of the bandwidth requirements to accomodate the laser noise. This, in turn, will give the resolution limit of the radar caused by that noise. A summary of the results is given.     

Improvement Factor of the Phase-Sensitive Noncoherent MTI

The phase-sensitive noncoherent MTI detects targets by relative motion between the target and an extended clutter background. In this type of MTI, the phase of the target is compared with the phase of the clutter in an adjacent range bin. Theoretical analysis of the system's performance is presented. The improvement factors for single- and double-delay periodic filters are derived and computational results are included.     

The Uncertainty of Pulse Position Due to Noise

The time at which a received signal crosses a certain level fluctuates in the presence of noise. In this paper, a theoretical formula for the standard deviation of this thresholding time is obtained. The formula is applied to the detection of a pulse perturbed by Gaussian noise. Two practical detection schemes, the peak amplitude estimator and the double differentiator, are theoretically analyzed and compared. Also, a formula is derived which may be used to determine the efficacy of a false-alarm detection system.     

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.     

Design and Evaluation of an Adaptive MTI Filter

The design and evaluation of an adaptive moving target indicator (MTI) filter, the adaptive canceler for extended clutter (ACEC) is dealt with, taking into consideration adaptivity to clutter mean Doppler frequency. This consideration is one of the most important operational requirements in adaptive MTI's and permits a relatively simple hardware implementation as compared to more general optimization and adaptivity criteria (briefly described). The ACEC's algorithm compensates in real time for the clutter mean Doppler frequency. Performances have been obtained by digital computer simulation in various operational conditions.     

On Optimal Control of Linear Systems in the Presence of Multiplicative Noise

This correspondence considers the problem of optimal regulator design for discrete time linear systems subjected to white state-dependent and control-dependent noise in addition to additive white noise in the input and the observations. A pseudo-deterministic problem is first defined in which multiplicative and additive input disturbances are present, but noise-free measurements of the complete state vector are available. This problem is solved via discrete dynamic programing. Next is formulated the problem in which the number of measurements is less than that of the state variables and the measurements are contaminated with state-dependent noise. The inseparability of control and estimation is brought into focus, and an "enforced separation" solution is obtained via heuristic reasoning in which the control gains are shown to be the same as those in the pseudo-deterministic problem. An optimal linear state estimator is given in order to implement the controller.     

Clutter Residues of a Coherent MTI Radar Receiver

In moving target indicator radar receivers a saturation is always present in the IF stages in order to compress the dynamic range of large clutter inputs. This nonlinearity greatly affects the performances of the cancelling circuits, because of the spreading of the spectra. A quantitative analysis of this effect has been conducted, with an analytical expression chosen for the limitation characteristic. A high degradation of both single-and double-canceller improvement factors has been obtained. Losses of 20 dB for the double canceller are not uncommon. Clutter residue levels at the receiver output have also been computed in order to see how the performance compares with ideal constant false alarm rate behavior.     

限带高斯白噪声声压时程模拟的修正三角级数法

针对传统三角级数法模拟高声压级下的高斯白噪声声压有效值与理论值存在误差的问题,提出一种修正三角级数法,预先将各谐波振幅置为1,最后调整声压有效值为理论值,模拟过程简单,消除了传统方法模拟有效值与理论值之间的误差。数值模拟得到的声压时程数据准确可靠,具有良好的随机性,表明方法用于限带高斯白噪声声压时程模拟具有合理性、可行性。     

Effect of timing jitter on performance of MTI filters

The effect of transmitting timing jitter and sampling jitter on a multipulse clutter cancellation system is analyzed, and explicit expressions are obtained for the net increase in the residue clutter power due to timing jitter. The increase in mean-square error is found to be proportional to the jitter variance, with the two jitters contributing almost equally. The system analyzed can have either a recursive or nonrecursive MTI filter, and the latter includes the familiar two- and three-pulse canceller as special cases. The increase in residue clutter power for a three-pulse canceller is about 4.8 dB worse than that for a two-pulse canceller     

Performance Compparison of Optimum and Conventional MTI and Doppler Processors

The performance of an optimum radar signal processor and more conventional techniques (such as MTI, adaptive MTI, and cqherent integration) are compared. A mathematical method is suggested and applied to several cases of practical interest. A number of operative conditions are discovered in which the conventional processing techniques give very poor performance and the optimum radar processor becomes necessary.     

Airborne adaptive MTI scheme with preventing the whitening of thetarget

A new airborne MTI scheme that applies to non-homogeneous clutter environment is presented. Results of simulation have proved that the scheme has a superior ground clutter suppression performance and can effectively prevent the whitening of a target     

The Effect of MTI Filter and Number of Unique Staggers on First-Null Depth and Clutter Attenuation

A recent series of papers have provided a model for a staggered-PRF radar which can be used to estimate both the depth of the first null (which is dependent upon the ratio of some function fM(?) of the set of M sampling deviations {?m} to the average sampling interval) and the clutter attenuation (as a function of the product of fM(?) and clutter standard deviation ?c). Some inconsistencies in the aforementioned papers are discussed and it is shown that realistic filters and typical stagger-ratio sets produce results which differ significantly from the idealized-filter predictions. Furthermore, even after filtering the residual clutter power at dc is shown to be more significant than the power in all the displaced clutter spectra postulated by the aforementioned model.