The Effect of Bandlimiting Filters on Probability of Error of MSK

Minimum Shift Keying (MSK) is a method of modulation which can be viewed as a special case of Frequency Shift Keying or a special form of Offset Quadrature Phase Shift Keying; therefore, it can be detected either by a discriminator or with a pair of matched filters. In the latter case, the system is optimal, provided there are no bandlimiting filters in the transmitter and receiver. These filters introduce intersymbol interference and hence degrade the performance of the system. In this paper we investigate analytically the effect of a bandlimiting filter in the receiver on the error probability of the system, presenting numerical results when that filter is of the Butterworth type. It is shown that a very simple suboptimal detector outperforms the matched filter detector so long as2W/R_{b} < 1.3, where Rbis the bit rate andWis the single sided 3 dB bandwidth of the bandlimiting filter.     

Intersymbol Interference in Binary Communication Systems with Single-Pole Band-Limiting Filters

The exact value of the probability of error is computed for binary communication systems with sampling detector or integrating-and-dumping detector, with nonreturn-to-zero or split-phase signals and single-pole filters in the receiver and transmitter. The effect of nonoptimal sampling time on the probability of error is presented.     

Error floors in the satellite and land mobile channels

In a satellite mobile channel (SMC) and land mobile channel (LMC) because of fading and nonlinear power amplifiers, constant envelope modulation and noncoherent detection methods may outperform other schemes. It is shown how to compute the error floor for four noncoherent digital communication systems in satellite and land mobile channels. Differential phase shift keying (DPSK) with differential phase detection (DPD) or frequency shift keying (FSK) with DPD, limiter discriminator integrator detection. (LDID), or limiter discriminator detection (LDD) are studied. The error floor is the residual error probability when SNR is infinity, i.e. the error probability in the system is limited by the error floor. The error floor is computed as a function of Doppler frequency, modulation index, and ratio of powers in the specular and diffuse signal components for DPSK-DPD, FSK-DPD, FSK-LDID and FSD-LDD systems     

A Propsed Method for Simpliofied Microcomputer Programming*

A key obstacle to wider application of the new microprocessors is the need to program in assembly language with fairly cumbersome instruction sets. We propose a new technique which will make it easy for applications-oriented non-programmers to generate efficient microcomputer programs without any need to learn assembly language. The user merely specifies an analog-computer-like block diagram whose intuitively meaningful block-operators specify standard mathematical operations (addition, multiplication, integration, etc.) and input/output operations (e.g., analog/digital conversion, switching, sensing). These standard operations are implemented as subroutines in the microcomputer read-only memory (ROM). An interactive editor/translator program running on a small minicomputer translates block-diagram specifications into a simple address table and loads it into the microcomputer memory (RAM, PROM, or ROM). This address table represents the block-diagram operation sequence and specifies successive jumps to the correct standard subroutines in ROM and data fetching/storing operations in the random-access memory.     

Compressive Properties of Metal Matrix Syntactic Foams in Free and Constrained Compression

Metal matrix syntactic foam (MMSF) blocks were produced by an inert gas-assisted pressure infiltration technique. MMSFs are advanced hollow sphere reinforced-composite materials having promising application in the fields of aviation, transport, and automotive engineering, as well as in civil engineering. The produced blocks were investigated in free and constrained compression modes, and besides the characteristic mechanical properties, their deformation mechanisms and failure modes were studied. In the tests, the chemical composition of the matrix material, the size of the reinforcing ceramic hollow spheres, the applied heat treatment, and the compression mode were considered as investigation parameters. The monitored mechanical properties were the compressive strength, the fracture strain, the structural stiffness, the fracture energy, and the overall absorbed energy. These characteristics were strongly influenced by the test parameters. By the proper selection of the matrix and the reinforcement and by proper design, the mechanical properties of the MMSFs can be effectively tailored for specific and given applications.