Design and implementation of mobile satellite modulator based on MF-CDMA

In this paper a mobile satellite modulator based on MF-CDMA is designed and fabricated. The mobile satellite modulator can support maximally 384 kbit/s. To support maximum transmission rate of 384 kbit/s we need 3 frequency bands. The baseband I/Q quadrature modulation and Mux is implemented in the digital block. The output of the digital part is a low IF signal, 20±4.35 MHz. And then the analog block converts this low IF signal to 950∼1450 MHz by the double conversion method. The mobile satellite modulator includes a 5-bit digital attenuator, RF switch and BPF. We implemented both digital part and analog part in one PCI card. We measured the mobile satellite modulator´s spurious rejection at about >55dBc and the output signal flatness is <5dB at 950∼1450 MHz. And the modulator shows good IMD3, -61 dBc.