Radiated Power And Phase Calibration Of A Multichannel Signal Transmitter
Publication Date: 2017-Feb-03
The IP.com Prior Art Database
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Characterizing the signal transmission performance of a communication system (a base station, for example) is an important part of evaluating the overall performance of the communication system. In some systems, such as the one shown below in Fig. 1, the transmitter portion of the communication system is provided with a connector that can be used for connecting an antenna. In place of the antenna, a measurement instrument such as a signal analyzer, can be coupled to the connector and measurements carried to evaluate the signal generated by the transmitter. This arrangement works satisfactorily when such a connector is provided and the transmitted signal is a single channel signal. However, many transmitters are configured to transmit multichannel signals. In such transmitters, each channel among the multiple channels has to be characterized in order to evaluate the overall performance of the multichannel transmitter. This can be performed by using the connector (when a connector is provided) to individually test each channel over a dynamic power range that encompasses an overall dynamic power range of the multichannel transmitter. The individual test results corresponding to the individual channels can then be entered into a lookup table, for example. The lookup table can be subsequently used by a signal processing unit of a transmitter to carry out any adjustments if needed on one or more channels. In some applications, the signal processing system can be used to provide beam forming on the signals generated by the multiple channels. In such applications, the phase characteristics of the various channels should be known in addition to the power characteristics. consequently, where feasible, a multichannel measuring instrument can be coupled to the connector and used for this purpose. However, some systems, such as a multiple input multiple output (MIMO) system, may not include a connector. As a result, a different approach has to be taken to evaluate the multiple channels.
Fig. 1: Traditional test setup
One approach for carrying out testing of multiple channels of a multichannel transmitter that does not have an antenna connector (for example, a printed circuit board with an embedded antenna) or does not provide ready access to the transmitter circuitry (when enclosed inside a housing, for example), is to perform measurements upon the signal radiated by the antenna. Traditionally this is carried out by using what is referred to as a very near-field measurement procedure that involves the use of a probe to measure the signal radiation characteristics at several locations close to the antenna, such as an antenna radiating surface of parabolic dish antenna. However, introducing a probe into such locations very close to the antenna radiating surface can disturb the radiation characteristics of the antenna and lead to misleading or er...