近年來，無線通訊系統有許多關於MIMO的研究，因為MIMO具有高頻譜效益。然而，欲在行動設備上放置多天線會有一些問題，例如空間大小有限。MSAA是一種多天線陣列技術，其在無線通訊設備接收端包含了主要接收天線與MSE天線，其中MSE天線並無RF接收電路，因此可以節省多天線陣列所需的空間。 本論文中，以Alamonti空時碼(Space-Time Code)推廣至四根傳送天線的空時方塊碼(Space-Time Block Code)作為基礎MIMO系統。系統的傳送端包含四根正常的傳送天線，而在接收端使用四根接收天線，其中包含兩根正常的接收天線與兩根輔助天線，這兩根輔助天線如同MSAA中的MSE天線，其並無RF電路。在系統設計中，考慮輔助天線是否改變訊號頻率，並分析是否改變訊號頻率的效能。最後設計分集編碼與分集調變系統，用來提高輔助天線系統的增益。 With the development of multiple-input and multiple-output (MIMO) communication system it still has the problem of implement multi-antenna system on the mobile set it is due to the limited space available on the mobile set. In the Modulated Scattering Antenna Array (MSAA) system at the receiver side it consists of one normal antenna and several modulated scattering elements (MSEs) withonly one RF circuit is fabricated to attain the MIMO advantages. In this study we consider an MIMO communication system based on space-time code (STC). In this system it is implemented with four transmitter antenna which have the normal antenna architecture while at the receiver side it is implemented withtwo regular antenna and two auxiliary antennas thatare designed based on the concept of the MSAA technique without any feasible RF circuits implemented. The characteristics and performance of system are studied extensively when the carrier frequencies at the auxiliary antenna are fixed or ‘scanning’. Various diversities based on coding techniques and/or modulating methods are also considered in the system performance evaluation. It reveals that with this auxiliary antenna design at the receiver side it can attain the advantages of MIMO system while reducing the required antenna space and eliminating the complexities of RF circuits design.