A novel beamformer for circular sonar arrays
A new Beamformer (BF) technique using Linear Deltamodulation (DM) on the spatially sampled circular array sensor signals is presented. In this method, the FIR-type of beam-former implementation for circular arrays results in an extremely simplified hardware which does away with multipliers and retains basically adders. Thus, the immediate problem of large word-size is considerably resolved. The DM-type of BF by virtue of the implementation, provides an additional advantage of beam-space interpolation. Various aspects of array gain, sidelobes and noise performance are dealt with the help of simulation studies. Hardware structures both for fixed and programmable beamformer coefficients are also proposed which bring out the potential of this technique for compact sonar systems.
Waveform encoding of voiceband data signals
This is a tutorial paper on encoding the waveform of voiceband data signals into digital form for digital transmission. The encoding algorithms covered are PCM, DPCM, and DM with and without quantizer adaptation. Coder bit rates from 16 to 64 kb/s are considered. Most digital Codec's on voiceband channels are designed primarily for speech and their performance with speech is well known. However, since many voiceband channels may contain other signals such as voiceband data, adequate performance with such signals is a necessity. Much of the paper is a summary and an interpretation of previous work in encoding data signals. Some new perspectives and material are presented, especially for DPCM. Topics covered include the sampling phase effect, fast and slow acting quantizer adaptation algorithms, comparison between speech and data performance, dual-mode coders, network considerations, and the effect of quantizing noise on the phase integrity of data signals.
Complex thoracic vascular injury repair using deep hypothermia and circulatory arrest.
A 61-year-old man with a penetrating injury to the innominate artery, left common carotid artery, and left subclavian artery at their origins from the aortic arch with associated injuries to both innominate veins and an innominate artery to vein fistula after a single stab wound is described. The patient was managed successfully using cardiopulmonary bypass together with deep hypothermia and circulatory arrest. Presentation and management are discussed.