Bat Signals as Optimally Doppler Tolerant Waveforms

Altes, Richard A.; Titlebaum, E.L.

doi:10.1121/1.1912222

Cited by 149 publications

(55 citation statements)

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“…Decades after the first hypotheses (Altes and Titlebaum, 1970;Cahlander, 1967;Kroszcynski, 1969;Strother, 1961) about the adaptive value of the details in FM call design, we have a new and powerful quantitative means to interpret why bats use a certain FM call design. The acoustic focusing theory sheds new light on our understanding of FM echolocation and may be used in the design of small autonomously moving vehicles using airborne sonar for orientation (Kuc and Viard, 1991).…”

Section: Discussionmentioning

confidence: 99%

“…The curvature of the frequency modulation offers an additional way to influence ranging acuity: FM call designs with hyperbolic frequency modulation have been called Doppler-tolerant because their ranging acuity is not at all impeded by Doppler shifts (Altes and Titlebaum, 1970;Kroszcynski, 1969). But note that even hyperbolically modulated calls suffer from Doppler-related ranging errors.…”

Section: Bandwidth Frequency Modulation and Doppler Tolerancementioning

confidence: 99%

“…Secondly, the width of the CCF envelope is likely to widen with increasing Doppler shift. This second Doppler-related effect results in a reduced ranging acuity (Altes and Titlebaum, 1970;Boonman et al, 2003;Cahlander, 1967;Glaser, 1974;Masters and Raver, 2000;Pye, 1986;Strother, 1961).…”

Section: Bandwidth Frequency Modulation and Doppler Tolerancementioning

confidence: 99%

See 2 more Smart Citations

Flight and echolocation behaviour of whiskered bats commuting along a hedgerow: range-dependent sonar signal design, Doppler tolerance and evidence for `acoustic focussing'

Holderied

Jones

Helversen

2006

Journal of Experimental Biology

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SUMMARY Echolocating bats obtain three-dimensional images of their surroundings in complete darkness by emitting sonar signals and evaluating returning echoes. When flying close to objects, bats risk collision and therefore depend on the accuracy of images – particularly in the perceived distance of obstacles, which is coded by the time delay between call and echo. Yet, during flight, such accuracy is perturbed first because bats call and receive echoes at different positions and second because echoes are modified by Doppler shifts. Certain call designs avoid both sources of ranging error, but only for a limited range of distances [the `distance of focus' (DOF)]. Here, we show that whiskered bats (Myotis mystacinus) using broadband echolocation calls adjust call design in a range-dependent manner so that nearby obstacles are localised accurately. Such behaviour is adaptive because it reduces collision risk. The bats also reduced call duration to some extent as they approached obstacles so that most returning echoes arrived after they finished calling. This reduction in call duration during the approach to obstacles was neither the only nor the main factor that influenced DOF. Indeed, both duration and bandwidth of calls influenced DOF independently, with lower bandwidths and longer durations giving greater DOF. Our findings give a new perspective on the adaptive significance of echolocation call design in nature and have implications for sonar engineering.

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Section: Discussionmentioning

confidence: 99%

Section: Bandwidth Frequency Modulation and Doppler Tolerancementioning

confidence: 99%

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Flight and echolocation behaviour of whiskered bats commuting along a hedgerow: range-dependent sonar signal design, Doppler tolerance and evidence for `acoustic focussing'

Holderied

Jones

Helversen

2006

Journal of Experimental Biology

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“…Interestingly, some Doppler insensitive waveforms such as LFM approximately meet it in the narrowband case [4] [20]. The one with the Doppler invariance feature is the best Doppler insensitive waveform [9], and it 'minimizes the signal losses in the case of large and high range-rate' [4]; however, a Doppler insensitive waveform does not necessarily follow the optimal modulation law. Note that Doppler insensitivity and invariance If the range-rate is nonzero, the extracted range from the zero range-rate axis (i.e., the maximum amplitude for a noise-free matched filter matched to zeroDoppler as in (14)) will be biased by the range-rate.…”

Section: Discussionmentioning

confidence: 99%

“…For the narrowband case, LFM, HFM, nonlinear frequency modulation (NLFM), P3, and P4 codes all have some Doppler insensitivity [1, ch.5-6]. Doppler invariance is mathematically explicit in (9), and HFM strictly satisfies it. Interestingly, some Doppler insensitive waveforms such as LFM approximately meet it in the narrowband case [4] [20].…”

Section: Discussionmentioning

confidence: 99%

Range bias modeling for hyperbolic frequency modulated waveforms in target tracking

Song

Willett

Zhou

2012

2012 IEEE 7th Sensor Array and Multichannel Signal Processing Workshop (SAM)

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Abstract-Hyperbolic frequency modulated (HFM) waveforms offer detection performance that is "Doppler insensitive"-relatively unaffected by target range-rate in matched filtering. They have been applied in radar; but more they are particularly useful in sonar where the wideband Doppler insensitivity is especially prized. However, Doppler insensitivity does come hand in hand with a range bias, which would significantly degrade the tracking performance. In this paper, we model the range bias as a function of range-rate and system parameters, and then utilize that to calibrate the measurement equation in very precise target tracking. By doing so, the tracking performance can be improved, particularly for fast maneuvering targets.

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Doppler‐invariant property of hyperbolic frequency modulated waveforms

Yang

Sarkar

2006

Micro & Optical Tech Letters

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The total delay through the two SMA connectors is approximately 73.26 ps, which is very close to the 73-ps difference in time between the measurement data and the analytical model. This further validates the accuracy of the analytical model.As a result of this analysis, it is important to point out that when measurements are performed on temporally unbalanced structures using a VNA, the differential-mode measurements obtained are actually the sum of the odd modes and not the true-differential mode. CONCLUSIONThis paper has presented a model for unbalanced differential-mode operation. The theoretical model was used to mathematically analyze a temporally unbalanced structure. The model results were validated by a comparison with the measurements. Further, the results were found to agree with those obtained using commercially available software, Agilent Eagleware Genesys. It was found that the differential-mode measurements obtained from a VNA are actually the sum of the odd modes and not the true-differential mode.ABSTRACT: When a target has a large velocity, the Doppler effect is not negligible. In that case, pulse compression by means of a linear frequency modulation suffers from significant signal loss in performance due to the mismatch between the reflected signal and the matched filter caused by the Doppler distortion. This problem can be avoided by using a hyperbolic frequency-modulated waveform, which has the inherent Doppler-invariant property. In this paper, we demonstrate that the hyperbolic frequency-modulated waveform is Doppler-invariant under the assumption that the target velocity is constant, while for a linear frequency-modulated waveform it is not. Two numerical examples with rectangular and Gaussian pulse envelopes are presented to compare the performance of these two different modulation schemes under several different levels of Doppler distortions. We also compare the performance of this method with another Doppler-invariant pulse compressor based on the bipolar waveform and multiple integrator pair. ABSTRACT:A new selective remeshing approach to efficiently utilize the finite-difference time-domain (FDTD) method for simulating 3D microwave heating cavities with rotating mode stirrers is presented here. The proposed scheme is implemented in a ϳ300L multimode applicator and the result compares favorably with a validation experiment. The proposed implementation of the selective remeshing scheme is efficient, in that the remeshing is done "on the fly" and the previous FDTD solution is used to continue the simulation as a single run of the FDTD solver.

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Bat Signals as Optimally Doppler Tolerant Waveforms

Cited by 149 publications

References 0 publications

Flight and echolocation behaviour of whiskered bats commuting along a hedgerow: range-dependent sonar signal design, Doppler tolerance and evidence for `acoustic focussing'

Flight and echolocation behaviour of whiskered bats commuting along a hedgerow: range-dependent sonar signal design, Doppler tolerance and evidence for `acoustic focussing'

Range bias modeling for hyperbolic frequency modulated waveforms in target tracking

Doppler‐invariant property of hyperbolic frequency modulated waveforms

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