{'fraction_non_alphanumeric': 0.013601036269430052, 'fraction_numerical': 0.0, 'mean_word_length': 5.331967213114754, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
EVALUATION OF THE COMPRESSION PERFORMANCE OF REC ECHOES USING A SPATIALLY VARYING WIENER FILTER

The focus of the chapter is to evaluate techniques that improve the image quality using a coding and pulse compression technique by either reducing the sidelobe levels, improving spatial resolution, or increasing the signal-to-noise ratio beyond what is available when using a Wiener filter. The techniques evaluated in this chapter were applied directly to the REC technique but could also be applied to general techniques involving coded excitation and pulse compression. In previous chapters, compression was based on the simplification that the spatially varying nature of the echo signals was negligible. Under this simplification, the Wiener filter used for compression did not include a spatially varying response. However, it was hypothesized that a Wiener filter containing adaptive variables based on the spatial location of the region being evaluated would lead to improved image quality. Simulations and experiments were conducted to test the hypothesis. This chapter is subdivided into two sections, with each section evaluating a different variable being adjusted in the Wiener filter. The first section will evaluate the effects on the compression when the adjustable parameter in the Wiener filter is the linear chirp that depends on the spatially varying pulse-echo impulse response. The second section will evaluate the effects on the compression when the adjustable parameter is the spatially varying echo-signal-to-noise ratio.