A Lamb wave device for a communication system with ternary logic

Abstract

297 4.t m C Fig. 1. Device to extract maximum.i I ' 1 I 1 l l I I . l . n m bit OUTPUT Fig. 2. Sorting device.However, in such cases the digit in the maximum must be 1, for otherwise it would be deleted. In short, in all cases the bit produced by the OR gate during any cycle equals the corresponding digit of the maximum. In consequence, we need only to save this output in an m-bit shift register, which will contain the maximum at the end of m cycles (MSB on the right). Now let us consider the extension of the method to sorting. If the N integers are placed in m-bit circulating registers, they can be used repeatedly as inputs for the device. Every time a maximum is extracted, it is deleted. Therefore, the next time the second largest number would be extracted. Continuing this N times would extract the N integers in sorted order. We show in Fig. 2 such a hardware sorting device. A second set of flip-flops are provided. The completion of the extraction of each maximum value would cause the DONE fIag to be raised, which causes the second flip-flop for the maximum to be cleared, excluding the value from future extraction processes. At the same time, the DONE signal clears the output shift register and sets the first flip-flop for each element of the vector, to ready the device for the next cycle of maximum extraction.Note that Fig. 2 works only if all the values in the vector are different. Otherwise it would exclude all the values equal to each other from future extractions at the same time, and not all N values would be recovered. This problem may be solved by inserting between the two sets of flip-flops a device which will mask out all but one 1. Such a device is used in priority interrupt systems, which must mask out all interrupt requests except that one that is highest in the "daisy chain." (See, for example [ 1, p. 4431 .) In most applications of the method, N would be much greater than m, and the cost of the device would be dominated by the 2 N flip-flops and 4N gates plus the N-input OR network. The extraction of each maximum takes m + 1 clock cycles, and the sorting of an N element vector takes approximately N(m + 1) cycles. Note that there has to be a slight delay between the extraction of one maximum and the start of the next extraction because of the need for extra time to clear the second flipflop and the output shift register.Finally, we remark that it is a simple matter to modify the device in order to extract minima instead of maxima: Just move the inverters from behind one set ofmDgates to behind the other set. It is also quite easy to modify the sorting device such that the maximum and the minimum are both extracted and deleted, so that the total sorting time may be halved. Finally, the device can also handle 2's complement integers: Just complement all sign bits before sending the numbers t o the device and complement again after each number is extracted. However, signand-magnitude values must undergo more complex treatment to change the range of values to all positive.It is the author's underst...

Data Communications Using Guided Elastic Waves by Time Reversal Pulse Position Modulation: Experimental Study

“…, a carbon steel pipe and a stainless steel pipe) and a National Instrument PXI acoustical measurement system that includes an arbitrary waveform generator and a digitizer. We note that data communication schemes using elastic waves have been reported for, for example, flood detection in oil rigs (see, e.g., [23,24]), drill string telemetry [25] in the measurement while drilling (MWD) and logging while drilling (LWD) services in the oil and gas industry [26,27] or Lamb wave communication (see e.g., [28]); systematic studies of high data rate communication schemes using elastic waves are lacking. We note that a pulse position modulation scheme using guided acoustic waves for flood detection was proposed in [23,24].…”