The received low frequency signals in the long range shallow water will suffer severe attenuation and modal dispersion effect, which will distort the signal and deteriorate the communication performance. In this letter, a modal dispersion compensation receiver is proposed, which exploits the de-dispersion transform to compensate intra-mode dispersion and the rake combination to combine the multi-mode components. With the proposed receiver, the waveform expansion of high order modes is compensated, and thus more modes can be distinguished from the noise and the rake combination gain is improved, which leads to high communication accuracy. Simulation results show that the proposed receiver can achieve about 3 dB gain for the 40 km range and signal with a center frequency 400 Hz.
The conductive inks were prepared with different silver powder morphologies and different silver powder mass fractions.The relation between the ink viscosity and the shear rate was determined with the cone-and-plate viscometer,and the varying curves of square resistance of conductive ink with time were obtained when it was cured at 120℃.The results show that the morphology of silver powder has a great influence on the viscosity of the ink,and the bigger the size of the silver powder,the higher the viscosity of the ink.Meanwhile,the big size of the silver powder will be of great benefit to the thixotropy of the ink.The conductive ink has higher viscosity and better thixotropy when the mass fraction of silver powder increases.Under the same condition,the square resistance of the silver conductive ink prepared with flake silver powder is lower than that with spherical silver powder.Meanwhile,the bigger the specific surface area of the flake silver powder,the lower the square resistance.However,the solvent can volatilize faster if the silver conductive ink is filled with spherical silver powder instead of flake silver powder.
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