The CBS transponder Testing by the EGSE

Jin-Ho Jo, Dong-Han Shin, Jong-HeungPark, Seong-Pal Lee

Electronics and Telecommunications Research Institute(ETRI)

Yusong P.O box 106, Daejon, KOREA

Abstract: Electrical Ground Support Equipment(EGSE) is used to check out satellite payload during the development prior to launch.The main task of EGSE is to check out satellite systems, at system or subsystem level, during integration and validation phases of their life-cycle.This paper represents the EGSE design configurations we implemented for the Communication and Broadcasting Satellite(CBS) transponder performance testing and test results of CBS transponders by the EGSE.

Key Words: CBS transponder, EGSE, CTS, PCTS, EQM, FM

1. Introduction

According to the space development plan of Korean government, CBSpayload development project is under cooperating between Electronics TelecommunicationsResearch Institute(ETRI) and industry in Korea.

CBS payload is consists of Ku/Ka band transponders and antennas. In CBS payload development project, ETRI plan to develop EQM(Engineering Qualification Model) and FM(Flight Model) payload from May 2000 to December 2005.

This paper represents EGSE design configurations which was used for the CBS transponder testing and test results of CBS transponder testing by the EGSE.

2. CBS PayloadOverview

The CBS is a GEO satellite for the communication and broadcasting service over the Korea peninsula area. The Table 1 shows the available services requirements by the CBS.

Table 1 Available service by the CBS

Transponder / Services
Ku-Band / Communication Services
SCPS-QPSK-FDMA(64kbps)
HDR(up to 25Mbps)
Trunk service(up to 60Mbps)
VSAT
Broadcasting Services
Analog FM-NTSC color TV
MPEG-2 SDTV
MPEG-2 HDTV
Ka-Band / Communication Services
Multimedia service
Trunk service
VOD service
Broadcasting Services
DTH service

Table 2 shows the payload specifications of the CBS. TheFig. 1 shows the CBS transponder configurations.

Table 2 CBS payload specifications

Ku-Band / Ka-Band
EIRP / 52dBW / 55.5dBW
G/T / 9.4dB/K / 9.4dB/K
Channel BW / 36MHz / 100MHz
Service life / Over 15 years
No. of Channel / 3 channels for EQM
Redundancy / 3 active, 1 backup
Antenna type / Offset Gregorian

The CBS transponder input coupler and output coupler are used for the system verification. All the stimulus signals are connected to the input test coupler port and all the output response signals are monitored at output test coupler port in the system testing phase.

All equipments are redundancy configurations. The LNA are 2:1 and channel amplifiers and TWTA are 4:1 redundancy configuration. The channel amplifier have two operation mode, one is Fixed Gain Mode(FGM) and the otheris Automatic Level Control(ALC) mode. All the equipments of the CBS transponders are monitored and controlled by the ground TT&C interface.


Fig.1 CBS Ka band payload block diagram

2. EGSE Overview

The main task of EGSE is to check out satellite systems, at system or subsystem level, during integration and validation phases of their life-cycle. Through a combination of hardware and software elements, EGSE supports manual, semi-automatic and fullyautomated testing. Automation is achieved by offering users simple, yet powerful means to write their own test application programs (test sequences) in high-level, test-oriented language and to run them in a strict real-time environment. The core of this environment is a user-configurable real-time database, containing all the information needed to calibrate acquired data, check them against predefined thresholds, automatically react to out-of-range conditions, display data using animated graphics or synoptic windows, and so on.

Fig.2 shows the configuration of EGSE being developed for CBS EQM transponder testing. EGSE comprises two parts, namely CTS and PCTS. CTS perform the function for accurate automatic testing of transponder RF performance.

RF stimulus & monitor instrumentation module of CTS consists of signal generator and signal measurement device, which generates various signals required for transponder performance measurement, and analyzes the transponder output signals.

RF switch matrix routes and transfers the signal to the transponder generated from RF stimulus & monitor instrumentation suitable to each measurement item for automatic performance measurement, and simultaneously performs the function for routing the output signal to the measurement instrumentation. Transponder performance measurement can be executed accurately as well as fast by using this RF switch matrix. CTS controller has built-in program required for measurement, and appropriately sets the parameters for various instruments according to each measurement, and provides the function for automatic measurement by controlling the various switch operations of switch matrix. CTS controller stores the measurement results in the DB, and compares the results with the specification, and also printout the results.

Fig.2 EGSE configuration

PCTS controls the parameters of various transponder equipments as well as performs the function for monitoring each equipment operation status. PIU receives transponder control command generated from the PCTS controller, and transfers it to the transponder after transforming to the suitable command format. PIU also receives the operation status as telemetry, and transfers this message to the PCTS controller by transforming to MIL-1553B format. PCTS controller also provides operator GUI environment, and interfaces with PIU for command generation and monitoring of transponder. PCTS also supplies DC power required for the operation of transponder equipments.

CTS controller and PCTS controller have connected by TCP/IP, and share various information required for test, control and monitor of transponder.

3. EGSE H/W Design

3.1 CTS H/W Design

CTS H/W comprises three parts: RF stimulus & monitor instrumentation, CTS controller, and RF switch matrix. RF stimulus & monitor instrumentation consists of CW generator, Sweep generator, Spectrum analyzer, Vector network analyzer, Power meter, Attenuator & switch driver and Data acquisition unit. These equipments GPIB interfaced with CTS controller, and operation parameters of the equipments are controlled as well as monitored by the CTS controller.

CTS controller configured with PC of windows98 environment. CTS controller has a built-in test sequence program for transponder performance testing, and provides functions for collecting and storing transponder measurement results, and printing out the results of comparisons with specifications. CTS controller interfaces with PCTS controller through the hub, and shares the data each other.

The RF switch matrix module located in the EGSE, will serve as a central interface between the measurement and stimulus equipment and the Unit Under Testing(UUT). All signal connections to the UUT will be made through this switch matrix at all the test modes. The RF switch matrix will contain the necessary circuitry for switching and routing the UUT stimulus and response signal to and from the appropriate measurement instrumentations. It will also provide external auxiliary ports, where appropriate, for injection or monitoring of special signals. Fig.3 shows the CTS configuration.

Fig.3 CTS Configuration


3.2PCTS H/W Design

The PCTS is used to provide the +70 V Main power supply function, and command & telemetry function for the equipments of Ka/Ku-band transponders. The overall PCTS configuration is shown in Fig.4.

The PCTS has a DC power supply for providing +70 V system power to Ka/Ku transponders during the ground test. The +70 V will be used for providing primary power to D/C, TWTA, and also for generating the secondary voltages in DC/DC converter of the transponder.

The PIU of PCTS will provide command(CMD) and telemetry(TLM) function for configuring the components of transponder during the ground test. In general, these CMD & TLM I/O interfaces are used to distribute commands to the payload and to gather telemetry from the payload. For this function, PCTS has the PCTS controller and the PIU which are connected with MIL-STD-1553B data bus. The PCTS controller generates command data which will be sent to the PIU and monitors the telemetry data which will be sent from the PIU, and the PIU is used to distribute commands to the payload and to gather telemetry from the payload. All data between the PCTS controller and PIU is transferred via the MIL-STD-1553B data bus, with the PCTS controller acting as the bus controllerand the PIU acting as remote terminal.


Fig.4 PCTS Configuration

4. EGSE S/W Design

The EGSE software was designed in a hierarchical structure. This wasimplemented by building standard functions that perform discrete tasks. These functions are then called at many points in the software,the reuse of these functions minimizes the size and complexity of the total system. Code that is modified is automatically updated in all modules that use the specified routines, additionally this allows for easier maintenance of the system software.The EGSE software is divided into 3 primary systems as CTS system, PCTS system and PODS. The overall EGSE S/W configuration is shown in Fig.5.

CTS systemperforms all RF data collection. It has the responsibility of controlling all RF data collection, EGSE RF switch matrix, and calibration. It makes all of the required RF test measurements.

PCTS system is responsible for DC stimulus, command and telemetry functions for the EGSE test system.

PODS(Paper On Demand System) is responsible for supplying all hardcopy data as well as a means of data archival and storage. Data is able to be viewed, analyzed immediately after the data collection has been performed without interfering with the RF data collection process.

Fig.5 EGSE Software Configuration

4.1 CTS System

The CTS system software is running on the Microsoft Window 98 operating system. It was written in the graphical programming language and developed with National Instrument LabView.

Test executive is a small low overhead routine that launches at system that is responsible for enabling user access to automated EGSE functions. When testing is selected to run, the test executive will prompt the operator for the required information to begin testing. Based on the operator’s input, only the test modules that have been selected will be loaded into system memory. At the conclusion of testing, utilities, or calibration, the system will return to the test executive main screen, and remain there until another function has been selected.

The Utility software bundle provide the operator with the ability to access EGSE functions that are normally accessible from program control, which includes, but is not limited to manual configuration and storage of the RF switch setup, graphical representation of the active RF path, access to the system calibration files for graphical viewing and printing, and the ability to upload correction factors to the RF instruments.

The test scheduler is responsible for launching the specific battery of tests required for the selected operational mode. It will provide the core ABORT control for the individual test routine, or the entire battery of tests to be terminated. The test scheduler also allows the operator to programmatically retile, and bring the current test windows to the foreground at any time during the testing process.


The calibration routineis invoked from the Test Executive program. It allows the user to independently calibrate the EGSE RF paths. This routine contain built in self checks to reduce calibration errors by insuring that the selected paths are physically connected. The system stores the calibration files in standard ASCII format. System calibration values can be viewed in the utilities menu. In addition the center frequency calibration values will be printed on the data hardcopy. Thisroutinecan control all of the EGSE switching for the selected paths.

EGSE configuration program supply the user with a means of interactively updating the operation of the EGSE through a GUI. It allow the user to change the active test level, EGSE operational mode, and load the ASCII.INI files to the binary encoded system files for program use. The user also able to define EGSE RF switch paths, calibration files, define payload switch configuration and review configuration control information.

4.2 PCTS System

PCTS System is the PC-based system with MIL-STD-1553B I/F card for the telemetry data transfer, which are all COTS (Commercial off-the-shelf) products. The application software on Windows-NT is coded in C++ language, and consists of two tasks as shown in Fig.6.

For the GPIB interface, GPIB command is formatted in GPIB interface function, and sent to Power Supply for +70V power on, and the GPIB telemetry is collected and displayed on the telemetry window of GUI.

Fig.6 Task Diagram of PCTS System

The 1553B command function is quite simple. Each command to be transferred is selected on the command window of GUI, and frame formatted in 1553B interface function for 1553B command. And then, this formatted command is sent to the transponder through the PIU for the command execution. For the 1553B telemetry monitoring function, PCTS system operation is performed as follows:

At first, the PCTS controller sends a kind of telemetry request to the PIU such that the PIU can send the telemetry raw data in response to it. And then, when the raw telemetry data frame comes, it is parsed into each mnemonic in accordance with the telemetry database.

The parsed telemetry mnemonic is converted with engineering unit data to represent a physical value of the telemetry. For the analog telemetry,this engineering unit data is calculated from a fifth-order polynomial equation of its calibration equation curve with coefficients in telemetry database for every mnemonic. And, for the digital telemetry and heater status, this engineering unit value that is character type is decided in accordance with discrete state of “0” and “1” in telemetry database for each mnemonic.

Finally, these EU values of telemetry are displayed on the telemetry GUI, and stored into hard disk of BC Station simultaneously.For event log function, the system gathers all control and status information including command sent, errors, etc.. And the gathered Event log will be displayed on the GUI, and stored into the hard disk.

4.3 PODS System

The PODS allows the EGSE to be configured to deliver hardcopy results when desired. The system can be configured as that the user can view the data, on the PODS monitor, in its final form prior to printout. In this way the user can decide which data is generated into hardcopy.

Each data file contains a data page revision that is allow archived data to be viewed in it’s original form if the data page format is incompatible with the current version. Batch printing can be accomplished by creating a .LST file in a standard ASCII editor with the filenames of the data to be printed out. This file can then be copied into the print directory of the PODS minimizes the amount of ‘non-essential’ hardcopy test results due to system aborts, incorrect setup, special testing, etc.

The test computer will create all archive data files in standard ASCII delimited format. This feature of the system is allowed viewing on multiple platforms for future retrieval/off line post processing in database programs such as Excel, Dbase, Lotus etc. This process will update a test summary data file that can be used to easily identify completed/remaining tests. This is done when the PODS write the data file to the archive data storage directory.

5. Testing

EGSE have two different kinds of modes for the operation, the component level testing mode and system level testing mode.

In component level testing mode, EGSE operation is manual for the RF performance testing of the transponder components. In this mode operation, special utility software tools are allows EGSE user to configure switches in the test system and also to plot display contents to the system printer.

Most of EGSE testing are performed automatically by RF testing sequence program S/W in system level test mode. Before test, EGSE performs calibration procedure for getting accurate testing results. RF testing sequence program is consist of test sequences for the transponder RF performance testing. It performs RF stimulus generation, switch control and data gathering and analysis through equipment control.

5.1 RF Performance Test

Before satellite transponder testing, EGSE performed transponder simulator testing for the functional verification it self. The satellite transponder simulator has same structure and functions with satellite transponder except it have only one RF channel. After EGSE verification with simulator testing, EGSE performed satellite transponder RF performance testing. The parameters of the satellite transponder RF performance testing by EGSEwere as following,

  • Input, output VSWR
  • Noise figure
  • Saturation output power
  • Phase shift
  • AM/PM conversion coefficient
  • Channel amplifier gain control functions
  • LO frequency stability
  • In band frequency response & group delay
  • Out of band frequency response
  • Inter-modulation characteristics
  • Spurious output
  • Over drive conditions

Except VSWR measurement, all the testing on above are performed automatically by EGSE. The VSWR measurements are manual.

5.2 Test Results