Cancellation of Unwanted Spectral Components in an FM Multivibrator System

The performance of FM multivibrator systems for high quality communications applications is limited by the presence of unwanted spectral components. A theory is presented for an improved system in which unwanted spectral components are cancelled, achieved by generating a cancelling component in a square-law device. The cancelling component tracks the unwanted component in both frequency and amplitude over a wide bandwidth of signal frequencies. Reductions in magnitude of the unwanted components by at least 16 dB are predicted; reductions of better than 14 dB have been achieved in practice.     

Large-signal stability analysis of solar array power system

A large-signal stability analysis of the solar array regulator system is performed to facilitate the design and analysis of a low-earth-orbit (LEO) satellite power system. The effective load characteristics of various control methods in the solar array regulator system, such as the constant power load, variable power load, constant voltage load, constant current load, and constant resistive load, are classified to analyze the large-signal stability. Then, using the state plane analysis technique, the large-signal behavior of the solar array system is portrayed and the stability of various equilibrium points is analyzed. Thus, this approach can be contributed to organize the optimal controller structure of the system by representing the relationship between the control method of the solar array regulator and the large-signal stability. For the verification of the proposed large-signal analysis, a solar array regulator system that consists of two 100 W parallel module buck converters has been built and tested using a real 200 W solar array.     

A two-phase mixture drift flow in the vertical cylindrical channel

The mathematical models of the solid-liquid flow regimes in the vertical cylindrical channel are described. A two-speed flow based on the solid-liquid phase interaction is considered. The problem was numerically solved and the calculation results were compared with experimental data.     

Stochastic Acceleration of Energetic Particles in the Heliosphere

In this paper we assess possible roles of stochastic acceleration by random electric field and plasma motion in the production and transport of energetic particles in the heliosphere. Stochastic acceleration can occur in the presence of multiple small-scale magnetohydrodynamic waves propagating in different directions. Usually, this type of stochastic acceleration is closely related to particle pitch angle scattering or parallel diffusion. Given the values of the parallel diffusion coefficient inferred from the observations of cosmic ray modulation or other energetic particle phenomena in the heliosphere, stochastic acceleration by small-scale waves is much slower than acceleration by shock waves and it is also much slower than adiabatic cooling by the expansion of the solar wind; thus it is considered as inefficient for producing heliospheric energetic particles or for the modulation of cosmic rays. Another type of stochastic acceleration occurs when particles go through random compressions or expansions due to large-scale plasma motion. This acceleration mechanism could be very fast when the correlation time of the fluctuations in plasma compression is short compared to the diffusion time. Particle acceleration by an ensemble of small shock waves or intermittent long wavelength compressible turbulence belongs to this category. It tends to establish an asymptotic p ^?3 universal distribution function quickly if there is no or little large-scale adiabatic cooling. Such a particle distribution will contain an infinite amount of pressure. Back reaction from the pressure is expected to modify the amplitude of plasma waves to an equilibrium state. At that point, the pressure of accelerated particles must remain finite and the accelerated particles could approach a p ^?5 distribution function.     

The Effects of Notch Filters on the Correlation Properties of a PN Signal

With wideband pseudo-noise (PN) communications systems, it is sometimes desirable to supplement the inherent interference rejection capabilities by adding notch filters to attenuate relatively narrowband interference. This correspondence presents an investigation of the effects of notch filters on the performance of PN correlation receivers. A theoretical analysis of the correlation drop due to filter distortion has been conducted and confirmed by experimentation. Additional measurements and analysis have established the trade-off between correlation drop and interference suppression as a function of interference bandwidth. A typical result is that by incurring a penalty of a 1-dB drop in correlation peak, interfering signals having bandwidths of 2 to 3 percent of the PN chip rate can be attenuated by 25 dB.     

Automatic Light Control Electro-Optical CCDTV Systems

For electro-optical TV systems, a simplified method of analysis has been developed for an automatic light control (ALC) loop preliminary ary design and performance trade-offs. With iris and shutter control mechanization incorporated, not only does the input light range increase, but the video response overshoot and settling time are reduced as well. This study shows that the appealing notion of heavily damped response is not often true, particularly in the realtime ime airto-ground surveillance of targets with varying backgrounds. In addition, with exponential and geometric feedback functions introduced, the resultant ALC dynamics are independent of the input light level. To verify the assumptions made and to demonstrate the feasibility of a working model, a complete system simulation is performed.     

Loss from Approximations to Square-Law Detectors in Quadrature Systems with Postdetection Integration

The trend toward digital processing of radar and sonar signals has ledto the use of ?baseband? or bipolar video signals. The processingof both the in-phase (I) and quadrature (Q) channels generally allows an exact representation of the signals, and no loss of sensitivity need occur. However, for reasons of economy or weight only one channel is often implemented. This correspondence shows that the sensitivity loss for this case often deviates considerably from the 3-dB rule of thumb.     

A Microwave Hologram Radar System

An airborne microwave hologram radar system has been developed which is a two-dimensional analog to optical holography. The field of view of the radar is directly below and to either side of the aircraft. Resolution is realized in the along-track direction by utilizing the synthetic aperture technique, and in the cross-track direction by means of a phased receiving array. The theory of operation is summarized, the demonstration system is described, and results for both the normal and contouring modes of operation are presented.