Test set for the measurement of IMDS at 900 MHz

The rapid growth in the number of subscribers and the highly time variable patterns of use in cellular mobile radio systems are creating severe channel congestion on radio cell-sites in urban areas. It is for this reason that a further increase in the number of co-sited base stations per cell is contemplated, which may lead in turn to excessive generation of unwanted intermodulation products (IMDs). These could become one of the major obstacles for an improved utilization of the limited available RF spectrum. An experimental test bench for the measurement of IMD products, generated by various components of a base station multicoupler system at 900 MHz is described. It is anticipated that such a set-up needs to provide for the measurement of IMD levels as low as -100 dBc for various frequency spacings, between co-sited transmitters