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The feasibility of pulse compression by nonlinear effective bandwidth extension
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10.1121/1.3625236
/content/asa/journal/jasa/130/4/10.1121/1.3625236
http://aip.metastore.ingenta.com/content/asa/journal/jasa/130/4/10.1121/1.3625236

Figures

Image of FIG. 1.
FIG. 1.

Time-domain amplitudes of a two-band signal with a 24% (upper) and 67% (lower) bandwidth of center frequency fc . The second band is 1/2 the amplitude and approximately 1.8 times wider and twice the center frequency of the fundamental. The dotted line shows the fundamental’s time-domain amplitude for comparison.

Image of FIG. 2.
FIG. 2.

Overlapping chirp signals due to scattering from three objects. The second and third objects are 0.5 and 5 mm, respectively, from the first.

Image of FIG. 3.
FIG. 3.

(Top) Amplitude of the Fourier transformed signal consisting of odd harmonics acquired by summation of a signal and its inversion (left) and even harmonics produced from the signal differences (right). (Middle) Derivative of phase with respect to frequency for the odd harmonic (left) and even harmonic (right). (Bottom) Derivative of phase with respect to frequency after application of a weighting factor to remove quadratic terms.

Image of FIG. 4.
FIG. 4.

(Color online) The experimental setup configured for (upper) normal scattering and (lower) backscattering.

Image of FIG. 5.
FIG. 5.

(Color online) Simulation results for (left) minimization of the secondary peaks, shown for the case when the second harmonic bandwidth is twice the first. (right) Minimization of the FWHM for the same case.

Image of FIG. 6.
FIG. 6.

(a) Impulse response of the transducer used for backscatter measurements. A linear chirp (b) is compared with a modified shaded chirp (c) created in the frequency domain and (d) a shaded chirp further modified to compensate for the transducer response. Waveforms here are for the 100% bandwidth case.

Image of FIG. 7.
FIG. 7.

Compressed signals scattered from three wires, when the second and wires are situated 1 and 5 mm from the first, respectively. Standard first (a) and second (b) harmonic compression are compared with the extended and amplified signals using two harmonics (c) and three harmonics (d).

Image of FIG. 8.
FIG. 8.

Compressed signals scattered from three wires, when the second and third wires are situated 1 and 5 mm from the first respectively. Standard first (a) and second (b) harmonic compression are compared with the extended and amplified signals using two harmonics (c) and three harmonics (d).

Image of FIG. 9.
FIG. 9.

The extension method’s SNR (squares) closely follows that of the second harmonic signal (circles), and is significantly lower than when the amplification step is omitted (triangles). SNR of the first harmonic compression (diamonds) is appreciable even when the pre-compression SNR approaches 0 dB.

Image of FIG. 10.
FIG. 10.

Compressed echoes from three 0.1 mm wires placed 0.5 and 5 mm from the first. Chirp input signals (top) modified in the frequency domain (middle) increased compression, particularly when the transducer’s response was accounted for (bottom).

Tables

Generic image for table
TABLE I.

Summary of FWHM measurements using first harmonic compression, second harmonic compression, extended bandwidth compression with two harmonics, extended bandwidth compression with two harmonics plus uplifting (amplification) of the second harmonic, and extended bandwidth compression with three harmonics plus uplifting of the second and third harmonics.

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/content/asa/journal/jasa/130/4/10.1121/1.3625236
2011-10-03
2014-04-18
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: The feasibility of pulse compression by nonlinear effective bandwidth extension
http://aip.metastore.ingenta.com/content/asa/journal/jasa/130/4/10.1121/1.3625236
10.1121/1.3625236
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