3 results about "Chirp" patented technology

Disclosed is a method and an apparatus for channel estimation regarding electromagnetic wave multi-path characteristics between a sender and a receiver by using a chirp signal. The method includes the steps of (a) multiplying a received composite signal by a narrowband chirp-shift-keying signal or narrowband multiple center-frequency-chirp signal generated by the receiver itself and outputting a sum of individual frequency components resulting from difference in distance of multiple paths for up-chirp and down-chirp signal portions of a chirp-shift-keying signal, respectively, the received composite signal being formed by generating narrowband chirp-shift-keying signals or narrowband multiple center-frequency-chirp signals by the sender, sending the signals by a transmission antenna, receiving the signals by a reception antenna of the receiver via a multi-path channel, superimposing the signals, and adding the signals; (b) multiplying outputs of the up-chirp and down-chirp signal portions of the sum of individual frequency components and calculating a tolerance frequency output; (c) compensating for a frequency tolerance of the sum of individual frequency components by using the tolerance frequency output and generating a frequency compensation output; (d) compensating for discontinuity of chirp-shift-keying signals resulting from use of the narrowband chirp-shift-keying signals or the narrowband multiple center-frequency-chirp signals regarding the frequency compensation output and generating a discontinuity compensation output having no discontinuity; (e) decomposing the discontinuity compensation output into individual multi-path signals by using a frequency analysis method; and (f) extracting an attenuation component and a time delay component caused by the multi-path channel from the individual multi-path signals by using a size of frequency components of each frequency.

The invention discloses an image distortion correction method based on single sweep quadrature space-time coding magnetic resonance imaging. The method comprises steps of enabling protons to spin in the space to obtain a secondary phase related to the space position in the triggering stage by combining 90-degree and 180-degree linear sweep frequency pulse (chirp pulses) with an orthogonally distributed space encoding gradient, in a sampling stage, performing data sampling through positive and negative gradient echo train lengths which switch quickly to quickly obtain T2-weighted spatial domain magnetic resonance imaging data, performing reconstruction and correction on the distorted magnetic resonance images through a reconstruction algorithm of high resolution and an image distortion correction method so as to obtain a quality magnetic resonance image with high resolution. The image distortion correction method based on quadrature space-time coding magnetic resonance imaging provided by the invention can not only perform distortion correction according to own data without extra reference scanning, but also have capabilities of resisting a non-uniform field and operating normally in a strong non-uniform field.