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This paper describes a laboratory facility capable of simulating time-varying radio multipath channel responses in real time under computer control. Four independent fading channels are available that can be used for single-polarization nondiversity, combined in pairs for single-polarization dual diversity, or cross-coupled to simulate the two outputs of a dual-polarization nondiversity channel. Each channel contains a controllable variable network capable of producing a narrowband intermediate frequency response that resembles the “three-path” function of Rummler. A wide range of models can be accommodated by altering the computer-stored sequences used to control each variable channel network. The only assumption implicit in the choice of model is that the channel response can be fitted to the generic function over bandwidths up to 40 MHz. The channel responses are controlled by either entering fixed parameters from a keyboard, or by reading time-varying parameters stored in disk memory. This description includes the architecture, hardware design, software implementation, and performance of the simulation facility. |
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