diff --git a/parts/sec3_multiSatSingleUser.tex b/parts/sec3_multiSatSingleUser.tex
index 697f999..5419e7c 100644
--- a/parts/sec3_multiSatSingleUser.tex
+++ b/parts/sec3_multiSatSingleUser.tex
@@ -176,7 +176,7 @@
   \in\mathbb C^{M_\ell T\times 1}.
 \end{equation}
 %
-将第 $\ell$ 颗卫星的观测堆叠并向量化为 $\tilde{\mathbf y}_\ell\triangleq\vect(\mathbf Y_\ell)$，则有
+将第 $\ell$ 颗卫星在该观测块内 $T$ 个采样点的接收向量按列堆叠为观测矩阵 $\mathbf Y_\ell\triangleq[\mathbf y_\ell(0),\ldots,\mathbf y_\ell(T-1)]\in\mathbb C^{M_\ell\times T}$，再按列向量化为 $\tilde{\mathbf y}_\ell\triangleq\vect(\mathbf Y_\ell)\in\mathbb C^{M_\ell T}$，则有
 %
 \begin{equation}
   \tilde{\mathbf y}_\ell