The MG3670B/C, MG3671A/B and MG3672A are digital modulation signal generators equipped with a high-performance quadrature modulator. They output the signals needed to develop, test, and evaluate digital mobile communications equipment and related devices with expansion units. The MG3670B/C operates from 300 kHz to 2.25 GHz, the MG3671A/B and MG3672A operate from 300 kHz to 2.75 GHz. Both provide a stable and precise output as well as spectrum purity up to +13 dBm, even with modulation. In addition to testing receiver sensitivity and excess input, they can be used for testing IF stage performance and for evaluating device quality. A CMOS-level mode is provided for I/Q signal input. The input frequency band covers the CDMA spread spectrum band, expanding the range of applications. The MG3670C/3671B/3672A can be expanded by rear panel extension connectors to use for auxiliary signal output functions special to communication system. MG3670B/C, MG3671A/B and MG3672A can be used in combination with up to eight modulation units and a burst function unit simultaneously.