Highly sensitive simple homodyne phase detector for ultrasonic pulse-echo measurements

Abstract

We have designed and built a modern versatile research-grade instrument for ultrasound pulse-echo probing of the elastic properties of a wide range of materials under laboratory conditions. The heart of the instrument lies in an AD8302 microchip: a gain and phase detector from Analog Devices, Inc. To construct the device, we have implemented a schematic that utilizes the homodyne principle for signal processing instead of the traditional superheterodyne approach. This design allows one to measure phase shifts with high precision and linearity over the entire range of 0−360• . The system is simple in construction and usage; it makes ultrasound measurements easily accessible to a broad range of researchers. It was tested by measuring the temperature dependence of the ultrasound speed and attenuation in a KTa 0.92 Nb 0.08 O 3 (KTN) single crystal at a frequency of ∼ 40 MHz. The tests were performed in the vicinity of the ferroelectric transitions where the large variations of the speed and attenuation demand a detector with outstanding characteristics. The described detector has a wide dynamic range and allows for measuring in a single run over the whole temperature range of the ferroelectric transitions, rather than just in limited intervals available previously. Moreover, due to the wide dynamic range of the gain measurements and high sensitivity this instrument was able to reveal previously unresolvable features associated with the development of the ferroelectric transitions of KTN crystals.

A High Spatiotemporal Resolution Ultrasonic Ranging Technique With Multiplexing Capability

“…In this way, the correlation ToF ranging technique can be performed on the recovered baseband signal sampled at the carrier frequency to accurately and precisely obtain a distance of multiple wavelengths. Meanwhile, the carrier phase can be recovered from the in-phase and quadrature channels of the downconverter to obtain a sub-wavelength range refinement [37]. In this paper, the proposed combination of correlation ToF and carrier shift detection with low 𝐹 𝑠 /𝐹 𝑐 value is realized by introducing an analog quadrature I/Q (in phase/quadrature) down-conversion scheme.…”

“…In this scheme, the spatial resolution is directly dependent on the ADC digitization resolution. Due to the nonlinearity of the inverse tangent function, the spatial resolution from phase shift of a monofrequency signal is only evaluated as an average value that is written in (1) where 𝜆 is the wavelength of ultrasound, and 𝑁 𝐴𝐷𝐶 is the ADC resolution in bit [36], [37].…”