A method for short or long range time-of-flight measurements using phase-detection with an analog circuit

A measurement technique using ultrasonic interferometry is described for non-contact, quantitative measurement of acoustic vibrations. A pair of low-cost ultrasonic transducers was used in a transmit–receive mode to direct a 40 kHz carrier wave to the surface of a solid target vibrating acoustically, such as a speaker cone. Demodulation of return signals consisted of a phase sensitive detection circuit to assess interference between the carrier wave and return signal. Recovered signals were enhanced using real-time digital signal processing hardware to improve signal-to-noise ratios for audio vibration measurements. Phase resolution of at least 3.4 mrads has been demonstrated in the audio frequency range. This represented an equivalent displacement of 2.3 µm in air.

Section: Experimental Arrangementmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Real-time measurement of acoustic field displacements using ultrasonic interferometry

Kannath¹,

Dewhurst²

2004

“…The statistical method [7,8] is presented for travel time estimation based on covariance models. Alternatively, travel time can be extracted deterministically by methods such as magnitude thresholding [9], matched filter [10], envelop moment [11], Hilbert-Huang transform [12,13], short time Fourier transform [14], wavelet transform [15][16][17][18], etc. All of these techniques suffer from the fact that they have certain tuning parameters, which need to be adjusted manually.…”

Section: Introductionmentioning

confidence: 99%

Order analysis for measurement of Lamb wave propagation distance

Liu¹,

Veidt²,

Lin³

et al. 2013

The order analysis technique is utilized to directly measure the propagation distance of a Lamb wave without knowing its travel time and group velocity. The proposed algorithm relates the propagating wave-packets to the referenced wave-packet, instead of to an absolute propagating distance. The dispersion signal in the frequency domain is firstly resampled and interpolated according to the unwrapped phase derived from the referenced wave-packet. Subsequently, it is transformed into the angle domain stationary signal. The ‘order’ is defined as the propagating distance of dispersion wave-packet normalized by that of referenced wave-packet. Then the order spectrum is obtained by the Fourier transform of the equivalent angle signal. Finally, the wave-packet propagation distance is estimated precisely according to the mono-function relationship between the orders and the propagation distances. Synthetic and experimental results show that the proposed method enables the precise propagation distance estimation and mode identification regardless of the phenomenon of dispersion and multi-mode overlapping.

“…A continuous waveform (CW) with constant frequency manifests itself as a phase shift between the transmitted and received waveform. Such a shift can be measured very accurately [3,4]. However, without precautions, the range of the measurement is limited to one wavelength.…”

Section: Introductionmentioning

confidence: 99%

“…In its simplest form, such an approach leads to cross correlation of the received signal with a template signal, i.e. matched filtering, and the determination of the moment of maximal correlation [3,4,7,8,[10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Time-of-flight estimation based on covariance models

Heijden

Tuquerres

Regtien

2003

We address the problem of estimating the time-of-flight (ToF) of a waveform that is disturbed heavily by additional reflections from nearby objects. These additional reflections cause interference patterns that are difficult to predict. The introduction of a model for the reflection in terms of a non-stationary auto-covariance function leads to a new estimator for the ToF of an acoustic tone burst. This estimator is a generalization of the well known matched filter. In many practical circumstances, for instance beacon-based position estimation in indoor situations, lack of knowledge of the additional reflections can lead to large estimation errors. Experiments show that the application of the new estimator can reduce these errors by a factor of about four. The cost of this improvement is an increase in computational complexity by a factor of about seven.