The Spacelink^NGT; Integrated Modem and Baseband Unit (IMBU) is one of the latest additions to the innovative SpacelinkNGT product line of TTC & TM/TC products from Satellite Services B.V. A specific variant of the IMBU was implemented for the latest generation of Portable Satellite Simulators (PSS) of the European Space Agency (ESA).

The PSS-IMBU supports the real-time interfacing, (de)coding and low-level processing of a wide range of different spacecraft/ground station TM/TC interfaces and data processing based on the latest CCSDS recommendations and ECSS standards.

The PSS-IMBU combines TM and TC functions at 70/230 MHz IF, Video as well as Baseband and LAN level using the latest technology. This has resulted in single-board implementations of a TM (transmitter) and TC (receiver) that operate fully independently. The overall PSS-IMBU is implemented as a compact 3U/19” rack-mountable unit.

The PSS-IMBU modem elements support the modulation and demodulation of TM and TC data at 70/230 MHz IF and subcarrier / video level and can either be used stand-alone or (in parallel) with the built-in baseband TM/TC processing functions.

The TM and TC baseband functions of the PSS-IMBU are specifically developed for Portable Satellite Simulation (PSS) applications. In this context, TM and TC data at packet/frame level are exchanged with the IMBU through a standard Ethernet TCP/IP LAN interface. All subsequent coding/ decoding and (de)modulation functions, as required at lower layers, are implemented within the IMBU hardware.

The modem and TM/TC baseband functions of the PSS-IMBU are implemented using (in-circuit programmable) FPGA technology and support real-time data processing at bit rates varying from 7 bps to 24 Mbps. (coding/modulation dependant)

The LAN interface for remote control/status and TM/TC data exchange is implemented as a standard 10/100BaseT Ethernet interface. Reconfiguration of the modem and baseband firmware can be performed in-the field without the need for the removal/exchange of hardware modules.

Besides using the IMBU as an Integrated Modem and Baseband Unit, all main functions of the unit can also be used independently of one another. This allows backward compatibility with existing ground station interfaces and traditional front-end chains.

In addition to the main TM/TC functions, the PSS-IMBU also implements specific test functions, such as a user programmable repetitive frame generator and a BER tester that can operate using normal spacecraft TM data (even when coded). The PSS-IMBU utilises a low-noise internal oscillator, but it also supports the use of either a 5 or 10MHz external clock to which signals are synchronised.

Currently supported FEC encoding schemes include: Reed-Solomon, (punctured) Convolutional or concatenated coding as well as turbo encoding. All encoding schemes are CCSDS compliant. Supported data coding formats include pseudo Randomisation, NRZ-L, NRZ-M, SPL encoding and QPSK/OQPSK differential encoding.

Modular Implementation

The IMBU is implemented in a fully modular way. Each of the main functions of the unit, including the power supplies, are implemented as single plug-in modules. This allows for a modular configuration of the unit in accordance with the customer or system requirements.

The IMBU consists of two separate modules being the TM (modulator) and TC (demodulator) module, each having baseband and IF capabilities. Both modules provide coding and physical layer functions, which at the physical level consist of IF, sub-carrier and baseband electrical interfaces.

Since all modules can be removed from the back of the unit, in-the-field maintenance is highly simplified and module replacements can be performed quickly.

Different types

Besides the PSS-IMBU other types of IMBU’s are implemented by Satellite Services B.V. to support ground station and earth terminal applications. (See also GS-IMBU datasheet)

Due to the flexible and small-scale implementation, the IMBU is also particularly suitable for hybrid and multi-satellite link applications.

Software support

Since the IMBU enables direct software to physical link implementations, software applications can be developed on any platform supporting Ethernet-TCP/IP network connectivity.

The standard LAN interface protocol of the IMBU is based on binary message exchange that also readily supports multi-link/unit implementations where applicable. A full ICD and an interface library is available to aid in system integration. Alternatively specific user protocols can be implemented as well. Support for the CCSDS Spacelink Extension Protocol (SLE) is being developed as an in-field upgradeable option.

For turn-key systems; the proven SSBV TM/TC baseband processing software and Control & Monitor Software (CMS) as deployed with TM/TC systems since 1996 is available under Windows™ 2000/XP-Pro/2003 Server™ to create an AIT/Test or operational ground station simulation Front-End including frame/CLTU and packet layer support; integrated archiving, logging and standard remote interface/gateway protocols.

For turn-key systems; the proven SSBV TM/TC baseband processing software and Control & Monitor Software (CMS) as deployed with TM/TC systems since 1996 is available under Windows™ 2000/XP-Pro/2003 Server™
to create an AIT/Test or operational ground station simulation Front-End including frame/CLTU and packet layer support; integrated archiving, logging and standard remote interface/gateway protocols

A separate software simulation framework (PSSmk3) that supports the IMBU has been developed by the European Space Agency (ESA). More details are available on request.

Overall Environmental and Physical Specifications

Characteristics

Dimensions HxWxD (mm)	133x448x443 mm
Weight	< 6 kg
Power	100-240 V AC 50/60 Hz
Operating Temperature Range (ºC)	5 – 35 ºC
Storage Temperature	-20 ºC to +60ºC
Storage Relative Humidity	Up to 85 %

PSS-IMBU