Characterization of an underwater electroacoustic transmit system and the use of real electrical equivalents circuits for approximating loaded projectors

Many underwater applications using acoustic communication rely upon an effective and efficient system of transmit hardware for adequate signal strength, bandwidth, and long-term sustainability. The focus of this work is to outline a procedure for investigating and optimizing the performance of transmit hardware intended for broadband underwater communication. The transmit hardware considered in this discussion consists of a power supply, power amplifier, matching (step-up) transformer, tuning inductor, and loaded piezoelectric projector. The use of an electrical equivalent circuit of a piezoelectric projector is adopted for performing complex power measurements throughout the transmit hardware for system characterization. Parameters for constructing an electrical projector circuit can be obtained analytically or experimentally. The complex power measurements are automated with a digital function generator and digitizing oscilloscope under software control. This method allows developers to evaluate the performance of the transmit hardware under realistic operating conditions in an engineering laboratory with standard equipment. One particular transmit hardware configuration, the WHOI Micro-modem, will be used to demonstrate the testing method.