Indoor localization based on ultrasound signals has been carried out by several research groups. Most of the techniques rely on a single ultrasound pulse ranging, where the Time of Flight between the ultrasound emitters and a receiver is computed. Ultrasound orthogonal modulation techniques have also been investigated and allow to compute the range between the receiver and multiple simultaneous emitters with increased accuracy. However, no comparative investigation on the possibilities of each of the modulation techniques, comprising Direct Sequence Spread Spectrum, Frequency Hopping Spread Spectrum, and Chirp Spread Spectrum, could be found. Also, common optimized demodulation and correlation techniques for FPGA ready implementations are not widely available. Moreover, the hardware requirements for capturing modulated ultrasound signals could not be found for all the techniques. In this work, the different modulation techniques are optimized and implemented on an FPGA. A dedicated custom ultrasound MEMS-based receiver hardware for broadband ultrasound signal capturing is developed. Several modulation parameters are developed and applied for optimized signal processing. The FPGA resource consumptions are evaluated for the implemented methods. All methods are compared against the regular pulse ranging method, in both single-access and multiple-access ranging mode. Results show that, on average, up to 8 ultrasound-modulated emitters with an orthogonal sequence of length 63 can be demodulated on a Zynq7020 FPGA. In most cases, ranging up to 8 m is demonstrated in both single- and multiple-access mode, with accuracies generally remaining at a centimeter level. The requirements and capabilities for each of the modulation schemes are highlighted in the conclusions.

中文翻译：

---

基于FPGA的超声多址扩频测距的优化

几个研究小组已经进行了基于超声信号的室内定位。大多数技术都依赖于单个超声波脉冲测距，在该测距中可以计算出超声波发射器和接收器之间的飞行时间。超声正交调制技术也已经研究过，可以提高接收器和多个同时发射器之间的距离。然而，没有找到对包括直接序列扩频，跳频扩频和线性调频扩频在内的每种调制技术的可能性的比较研究。同样，用于FPGA就绪实现的通用优化解调和相关技术也不是很广泛。此外，并非所有技术都无法找到捕获调制超声信号的硬件要求。在这项工作中，对不同的调制技术进行了优化并在FPGA上实现。开发了专用的基于定制超声MEMS的接收器硬件，用于宽带超声信号捕获。开发了几种调制参数并将其应用于优化的信号处理。针对实现的方法评估FPGA资源消耗。在单次访问和多次访问测距模式下，所有方法均与常规脉冲测距方法进行了比较。结果表明，平均而言，在Zynq7020 FPGA上，最多可以解调8个正交调制的发射器，正交序列的长度为63。在大多数情况下，单访问模式和多访问模式都证明了8 m的范围，精度通常保持在厘米级。结论中重点介绍了每种调制方案的要求和功能。