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Synthetic Aperture Sequential Beamforming

Synthetic Aperture Sequential Beamforming. 刘昊霖. SASB 算法. 两个阶段： 阶段 1 ：部分阵元发射固定聚焦脉冲，形成 virtual source ，接收也做固定聚焦，形成 1 条扫描线 . 重复 N 次，形成 N 条扫描线. 阶段 2 ：在阶段 1 的 N 条扫描线基础上，使用合成孔径，数条 Low Resolution Line 合成一条 High Resolution Line. 延迟计算方式. W 是变迹. SASB 算法的优点. 1 ，对比动态接收聚焦（ DRF ），横向分辨率更高。

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Synthetic Aperture Sequential Beamforming

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  1. Synthetic Aperture Sequential Beamforming 刘昊霖

  2. SASB算法 Kortbek, J.; Jensen, J. A. & Gammelmark, K. L. Sequential beamforming for synthetic aperture imaging Ultrasonics, 2013, 53, 1 - 16 两个阶段： 阶段1：部分阵元发射固定聚焦脉冲，形成virtual source，接收也做固定聚焦，形成1条扫描线.重复N次，形成N条扫描线

  3. Kortbek, J.; Jensen, J. A. & Gammelmark, K. L. Sequential beamforming for synthetic aperture imaging Ultrasonics, 2013, 53, 1 - 16 阶段2：在阶段1的N条扫描线基础上，使用合成孔径，数条Low Resolution Line合成一条High Resolution Line.

  4. 延迟计算方式 Kortbek, J.; Jensen, J. A. & Gammelmark, K. L. Sequential beamforming for synthetic aperture imaging Ultrasonics, 2013, 53, 1 - 16 W是变迹

  5. SASB算法的优点 Kortbek, J.; Jensen, J. A. & Gammelmark, K. L. Sequential beamforming for synthetic aperture imaging Ultrasonics, 2013, 53, 1 - 16 1，对比动态接收聚焦（DRF），横向分辨率更高。 2，对比合成孔径聚焦（SAF），能够节省存储Low Resolution Image 的空间。因为第一阶段子阵元固定发射聚焦和固定接收聚焦后形成一条LRL后，就可以把LRL放入一个FIFO的存储器中，而每个阵元接收的RF数据就可以抛弃以节省空间。第二阶段的beamforming只会用到FIFO的中LRL。 多阵元发射比单阵元能量高，性噪比好。

  6. 算法实现 Kortbek, J.; Jensen, J. A. & Gammelmark, K. L. Sequential beamforming for synthetic aperture imaging Ultrasonics, 2013, 53, 1 - 16

  7. 三种beamforming方法的对比 DRF，发射聚焦50mm SASB 第二阶段 SASB 第一阶段,VS 20mm F#1.5 SAF Kortbek, J.; Jensen, J. A. & Gammelmark, K. L. Sequential beamforming for synthetic aperture imaging Ultrasonics, 2013, 53, 1 - 16

  8. 横向分辨率对比

  9. 栅瓣(grating lobe)产生的原因 生成x=0mm,z=15.5mm处HRL的LRL的相位图（没有计算延迟）

  10. 生成x=0mm,z=15.5mm处HRL的LRL的（计算延迟） 叠加最大的情况

  11. 生成x=5mm,z=15.5mm处HRL的LRL 相差半个波长，相互抵消

  12. 生成x=10mm,z=15.5mm处HRL的LRL 相差一个波长

  13. Kortbek, J.; Jensen, J. A. & Gammelmark, K. L. Sequential beamforming for synthetic aperture imaging Ultrasonics, 2013, 53, 1 - 16

  14. 当α最大时，h 也会最大。 h的最大值为 LRL1和LRL2是两个相邻的LRL，黑色矩形和白色矩形分辨代表半个脉冲回波的波长，Δ代表扫描线之间的间隔，h代表相邻LRL之间的相位偏移，α代表角度 在Pitch>λ/2的情况下回避栅瓣： 限制范围，即参与合成的LRL数目

  15. ？ x=0,z=15.5mm处的一个脉冲回波

  16. 算法的不足 Kortbek, J.; Jensen, J. A. & Gammelmark, K. L. Sequential beamforming for synthetic aperture imaging Ultrasonics, 2013, 53, 1 - 16 1．对运动敏感。 2．横向分辨率还有待提高。

  17. 参考文献 Kortbek, J.; Jensen, J. A. & Gammelmark, K. L. Sequential beamforming for synthetic aperture imaging Ultrasonics, 2013, 53, 1 - 16 [1]Kortbek, J.; Jensen, J. A. & Gammelmark, K. L. Sequential beamforming for synthetic aperture imaging Ultrasonics, 2013, 53, 1 - 16 [2] Kortbek, J.; Jensen, J. A. & Gammelmark, K. L.Synthetic Aperture Sequential BeamformingUltrasonics, IEEE Symposium, 2008

  18. Kortbek, J.; Jensen, J. A. & Gammelmark, K. L. Sequential beamforming for synthetic aperture imaging Ultrasonics, 2013, 53, 1 - 16 谢谢

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