Design of Ultrasonic Voice Communication Modulator

Ye Zhiqiang

Abstract: In modern information warfare, with the continuous development of electronic countermeasure technology and equipment, the electromagnetic environment in the battlefield is worse and the communication electronic warfare is becoming increasingly fierce. This limits the application of radio communication in some special tactical backgrounds. In order to ensure the safety and smoothness of communication links, it is necessary to study various anti-jamming, anti-interception and anti-direction finding technologies suitable for military communication and seek new communication methods suitable for these specific environments. Ultrasonic voice communication is put forward under this background. Firstly, this paper briefly introduces AM modulation, sampling theorem, direct digital frequency synthesis and other related basic theories. Then, according to the specific requirements of the subject, an AM digital amplitude modulation scheme based on the basic principle of DDS and the hardware platform combining FPGA and single chip microcomputer is proposed. The idea of software radio is permeated in the design, and the circuit originally built by ADI is realized by software programming, which increases the flexibility of the system. Secondly, the hardware and software design of the whole system are introduced in detail. The hardware circuit of the system consists of amplitude modulation circuit and power amplifier circuit, in which the amplitude modulation circuit includes analog part, digital part and power supply part, which mainly completes the digital amplitude modulation function of voice signal and carrier signal. The power amplifier circuit is an independent circuit board, which mainly amplifies the amplitude modulation signal to drive the transducer, so as to send information in the form of ultrasonic waves. The design and working process of each part of the hardware circuit are analyzed in detail, and the corresponding circuit diagram is given. The software design of the system includes two aspects: on the one hand, the software design of single chip microcomputer, mainly using IAREmbeded Workbench development environment to complete the interface display of the system and the setting of various amplitude modulation parameters; On the other hand, it is the design of FPGA software. Quartus II is mainly used for software development, and various module units are written by using the schematic graphic input method of chart editor embedded in VHDL and Quartus II mixed programming method to realize amplitude modulation function in FPGA. Finally, the modulation system is tested, and the test results show that the system works stably and basically meets the expected design requirements.