For the modulator a modular concept was chosen which can be easily adapted to specific customer and system requirements with regard to output power and system configuration.
The whole modulator consists of four sections, the INTERFACE SECTION contains the TMTC interface, the nominal and redundant data / clock input interface and is responsible for Reed-Solomon encoding, interleaving and scrambling.
The second section, called DIGITAL SECTION includes the 4D-TCM encoding and the 8-PSK constellation symbol mapper. After filtering the digital baseband signal is converted to a differential analog signal for I and Q path.
These signals are forwarded to the MODULATOR SECTION. The analog I and Q signals control the analog X-band modulator. After amplifying the modulated carrier is available at the RF output.
The fourth section is the DC/DC CONVERTER SECTION which supplies all sections with power.
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The Modulator hardware concept is rather modular and flexible. If for example, the input data interface has to be changed only the INTERFACE SECTION would be affected. A further advantage of the concept is the isolation of RF and digital functions which leads to best RF performance and lowest EMC sensitivity.
The four sections of the modulator are mounted in three cases. The DIGITAL UNIT contains the board of the INTERFACE SECTION and the board of the DIGITAL SECTION. The MODULATOR SECTION and the DC SECTION have their own housings. All three cases are bolt together and build up the modulator assembly. Under a cap on top of the housing the supply lines are placed. For interconnection between the INTERFACE and the DIGITAL board a flexible PCB with 30 lines is used. A further flexible PCB with 20 lines is applied to connect the DIGITAL SECTION with the MODULATOR board.