This article deals with the parametric hydrophone antenna arrays the elements of which are connected in parallel on one coordinate (in the columns). The mathematical models had been developed which were derived from the formula of the directional characteristic of a right-angled flat radiator embedded into the absolutely hard baffle. A level of overshoots of the directional characteristic (as related to a principal maximum) amounts no more than 0.15; a coefficient of decreasing overshoots of the directional characteristics because of shifting lines is approximately equal to two 2 for the array (8 x 8 or 16 x 16) with a pitch equal to wave length, with shifting lines to half the array pitch, a gap between the elements is 0.1 of the array pitch and a direction of beams is from 5 to 18 degrees on both sides with respect to the normal to an antenna plane. Without the gap between the elements at the abovementioned conditions the overshoots and the coefficient of their decreasing will no more than 0.1 and approximately 2.4 respectively. Thanks to extending the antenna array pitch a number of antenna elements is being reduced, and consequently, a number of the power amplifiers will be reduced as well. The simulation results are presented including computed two-dimensional directional characteristics of the antennae. The overshoot dependences upon beam direction and antenna array element dimension are also shown.
Keywords: hydroacoustis parametric antenna array, narrow sector of scanning, parametric, antenna, nonlinear, element, array, array pitch, directional characteristic, overshoot, overshoot level, increasing of array pitch
This article deals with the hydrophone antenna arrays (the results of studying are applicable to radio-frequency aerials as well) the elements of which are connected in parallel on one coordinate (in the columns). The mathematical models had been developed which were derived from the formula of the directional characteristic of a right-angled flat radiator embedded into the absolutely hard baffle. A level of overshoots of the directional characteristic (as related to a principal maximum) amounts approximately 0.3; a coefficient of decreasing overshoots of the directional characteristics because of shifting lines is approximately equal to 1.4 for the array (8 x 8 or 16 x 16) with a pitch equal to wave length, with shifting lines to half the array pitch, a gap between the elements is 0.1 of the array pitch and a direction of beams is not more than 15 degrees on both sides with respect to the normal to an antenna plane. Without the gap between the elements at the abovementioned conditions the overshoots and the coefficient of their decreasing will be approximately equal to 0.2 and 1.6 respectively. Thanks to extending the antenna array pitch a number of antenna elements is being reduced, and consequently, a number of the receiving channels and power amplifiers will be reduced as well. The simulation results are presented including computed two-dimensional directional characteristics of the antennae. The overshoot dependences upon beam direction and antenna array element dimension are also shown.
Keywords: antenna, element, array, array pitch, element pitch, directional characteristic, side-lobe level, narrow sector of scanning, increasing of array pitch
Digital signal processing is commonly used in system engineering of a new state of the art. The monotonic (maximally-flat) step response of the high pass filter is required, for example, in the case of testing for a negative signal present against the background of the positive rectangular impulse of rather higher amplitude. Or, conversely, to determine whether a positive signal is present against the background of the negative rectangular impulse. As this takes place, a signal pass is allowed, but a false detection is not allowed. The reason of the false detection can be a negative overshoot on the step response of the high-pass filter that is used for suppressing a dc component and decreasing flicker noises. This case we can see in electromyography, for example, when weak nerves signal follows the strong test electrical pulse. Approximations of analog filters via a bilinear transformation had been used to research of digital filters first order filters differing step response monotone and the results of these researches are outlined in this paper. The block diagrams of digital filters featuring a more monotonous step response, but with an overshoot on the frequency response in a passband near to the cutoff frequency are offered. The requirements have been analyzed at which a negative effect of this overshoot is being reduced.
Keywords: filter, digital, high pass, HPF, monotonic, maximally-flat, step response
Digital signal processing is commonly used in system engineering of a new state of the art. The monotonic (maximally-flat) step response of the high pass filter is required, for example, in the case of testing for a negative signal present against the background of the positive rectangular impulse of rather higher amplitude. Or, conversely, to determine whether a positive signal is present against the background of the negative rectangular impulse. As this takes place, a signal pass is allowed, but a false detection is not allowed. The reason of the false detection can be a negative overshoot on the step response of the high-pass filter that is used for suppressing a dc component and decreasing flicker noises. This case we can see in electromyography, for example, when weak nerves signal follows the strong test electrical pulse. Approximations of analog filters via a bilinear transformation had been used to research of digital filters Bessel and Gaussian filters differing in the greatest step response monotone (especially Gaussian filters) and the results of these researches are outlined in this paper. The block diagrams of digital filters featuring a more monotonous step response, but with an overshoot on the frequency response in a passband near to the cutoff frequency are offered. The requirements have been analyzed at which a negative effect of this overshoot is being reduced.
Keywords: filter, digital, high pass, HPF, monotonic, maximally-flat, step response