SINGLE-ANTENNA IMPLEMENTATIONS of orthogonal frequency division multiple access (OFDMA) signal formats, such as Mobile WiMAX and 3GPP Long Term Evolution (LTE), can enable increased data rates. By doubling or even quadrupling the number of antennas in the implementation, as is done with four-channel multiple input multiple output (MIMO), the data rates can be increased further. As engineers migrate to four-channel MIMO, however, they will face increased complexity. A number of design and testing challenges must be overcome before peak data rates can be achieved. In an application note titled, "MIMO RF Test and Debug," Agilent Technologies provides an overview of the measurements that must be performed to ensure optimal performance in a four-channel MIMO implementation.
The concise four-page document emphasizes that engineers must look at all four channels individually as well as the inter-relationships between the channels. In addition, they must debug both the design and the hardware. These tasks can be accomplished by using a time-coherent, multichannel wideband oscilloscope and vector-signal-analysis software. The oscilloscope performs the four-channel, phase-coherent MIMO measurements. It also can be used to diagnose potential timing errors between the transmit antenna channels. When the software is used with the oscilloscope, it enables the measurement and analysis of LTE MIMO signals from the time, frequency, and modulation domains. Such capabilities aid an engineer in diagnosing and isolating hardware performance issues.
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