In wireless communications, multipath signals are received in both terrestrial and indoor environments where different forms of propagation are present and the signals arrive at the receiver from transmitter via a variety of paths. The results are called multipath interference, causing multi-path fading. It is advantageous to create repeatable multi-path fading in a controlled lab environment so that various radio designs can be compared in terms of performance such as throughput and receive sensitivity. IEEE has standardized channel fading into models A to F for varying degrees of severity. Based on these models, products in the past have used elaborate DSP to simulate these models. However, many of these products proved to be too expensive and too cumbersome to operate.
Adaura Technologies' OptiMeasure Series Switchable Delay Line Simulator (DLMS) uses shorted cables in a unique patent pending configuration to create a multi-path model that is extremely repeatable. The device utilizes shorted cables of precise lengths to create delayed signal reflection where RF power dividers and switches are used in an arrangement such that all of the geometrical combinations of the additive delays are created. The delayed path is switchable via computer or manual control so that a direct comparison of the performance can be made between multi-path and non-multi-path. The simulator is housed in a versatile 2U chassis. There are 5 additive 10ns delays creating a first order total of 50ns. Second order reflection creates a combined delay of 100ns. Subsequent reflections from the shorted transmission line cables create all geometrical combinations of the delays. This is analogous to the IEEE B model.