  In recent years, the minimum variance (MV) beamforming has been widely
studied due to its high resolution and contrast in B-mode Ultrasound imaging
(USI). However, the performance of the MV beamformer is degraded at the
presence of noise, as a result of the inaccurate covariance matrix estimation
which leads to a low quality image. Second harmonic imaging (SHI) provides many
advantages over the conventional pulse-echo USI, such as enhanced axial and
lateral resolutions. However, the low signal-to-noise ratio (SNR) is a major
problem in SHI. In this paper, Eigenspace-based minimum variance (EIBMV)
beamformer has been employed for second harmonic USI. The Tissue Harmonic
Imaging (THI) is achieved by Pulse Inversion (PI) technique. Using the EIBMV
weights, instead of the MV ones, would lead to reduced sidelobes and improved
contrast, without compromising the high resolution of the MV beamformer (even
at the presence of a strong noise). In addition, we have investigated the
effects of variations of the important parameters in computing EIBMV weights,
i.e., K, L, and {\delta}, on the resolution and contrast obtained in SHI. The
results are evaluated using numerical data (using point target and cyst
phantoms), and the proper parameters of EIBMV are indicated for THI.
