October 28, 2002 International Loran Association Development of a Next Generation Transmitter Control System Presented by: Terry YetskoBCO, Inc. George MukaiBCO, Inc. Erik JohannessenMegapulse, Inc.

Need for Modernized Transmitter Control Significant upgrade required both in functional capability and technology. Required as part of Loran recap effort. –Present SSX control console over 20 years old. Not supportable long term. Maintainability/reliability do not lend themselves to unattended operation. –Present SSX control console does not support required Loran enhancements. Present architecture robust but inflexible. System demands on the system are greater in the future. –Better timing. –Better envelope control.

TCS Design Philosophy Retained Existing Partitioning at System Level –GFE Loran Timer, Remote Control, Control Console and Power Distribution –XMTR Components - PGAs, Output & Coupling Networks, RF Switch Retained Existing Functionality –Replaced TOPCO, PATCO, SDA and Display Units with modernized/updated sub-assemblies Incorporated New Functionality –Support for Additional Drive Half Cycles –Dynamic Re-Assignment of HCGs –Real-Time Loran Signal Quality Analysis (SQA) Allowed for Future Capabilities –Intrapulse Frequency Modulation (IFM) –Enhanced Data Analysis

TCS Design Philosophy Rate A & B MPT, Set/Reset & 5 MHz MTS Antenna Switch Output Network (Unit 4) Coupling Network (Unit 5) Output Network (Unit 4) Coupling Network (Unit 5) RF Switch Pulse Generator (Unit 3) Antenna DHC Feedback Antenna Current Feedback FromTimer (Unit 1) Switch Control MTS Timing Signals PATCO TOPCO SDA DHC Current Pulse Switch Network (Unit 6) RF Output

TCS Block Diagram

Transmitter Control Subsystem (TCS) Alarm/Status Panel Thinview-15-SS9-RM-SP410 15” Touchscreen Display Retractable Keyboard Tray Kontron(ICS) RMX-EKB104 TCA (Transmitter Control Assembly) APC SU042-2 Redundant Switch APC Smart-UPS 3000 RM 5U Rear Mount Fan Assemblies Control Connector Assembly(s) TCC (Transmitter Control Console) #1 TCC (Transmitter Control Console) #2 Redundant Transmitter Control Consoles Fire Detect Assys

TCA – Block Diagram

TCA – VME Chassis 20 Slot Chassis Five COTS (Commercial-Off- The-Shelf) 6U VME Cards Three COTS PMC (PCI Mezzanine Card) Modules Two Custom VME Cards: One Custom PCI Daughter Card for HCG Control One Custom VME Card for Signal Conditioning, Qty 4 A B C DE Five Functional Groups

HCG/Serial Data Stream Control Group (HCG/SDSC) Majority of PATCO, TOPCO and Signal Distribution Assembly (SDA) functionality combined into one (1) custom VME Card married to: Motorola MVME MHz PPC Processor ICS MHz Dual Channel Data Acquisition Module. PATCO functions: timing and triggering, failsafe blanking, DHC feedback analysis, MTS data stream generation, polarity control, antenna feedback analysis and antenna tuning TOPCO functions: fault monitoring and analysis SDA functions: MTS data stream multiplexing PATCO TOPCO SDA

HCG/SDSC Block Diagram

TCS – Main Station Control Screen

TCS – Station Configuration Screen

TCS – Loop Maintenance Screen

TCS – Engineering Screens

Control Loop Algorithm - Amplitude Current system uses ratios to a reference voltage to control all 4 DHC amplitudes –Both ratios and reference voltages are thumbwheel selectable. –Adjustments to the reference voltage controls output power. Ratios still utilized for DHC 2, 3 & 4. –Ratios are contained in ECD table. Measurements made on 6 th pulse in group (like current system). –Potential expansion to analyze all pulses (droop compensation). DHC 1 adjusted based on power indication from antenna feedback. –Control loop is now closed based on system output as opposed to interim feedback (DHC feedback). –Control loops now compensate for variability in network cabinets.

Control Loop Algorithm - Timing Original timing loops utilized hardware implementation based on 60 % points. –Software algorithm currently maintains that approach but could be enhanced to be less sensitive to pulse shape. Configurable items provide flexibility. –Averaging period and adjustment step size –DHC Timing Position Currently set to offset DHC 2,3,4 150nsec, 100 nsec and 100 nsec respectively to improve phase modulation. –Potential expansion to base offsets either on ECD selection or analysis of antenna feedback. Fixed offsets added to DHC timing for individual pulses in each group. –Potential enhancement to base offset on feedback analysis of individual pulses.

Control Loop Algorithm - Tuning Original antenna tuning based on 5 th to 12 th 0-crossing. Analysis showed more accurate measurement achieved starting at 6 th 0-crossing. Algorithm modified to tune based on 6 th to 12th crossing. –Crossings are configurable to provide flexibility. –Similar slope crossings chosen to minimize error caused by feedback offset. Averaging period and adjustment time also configurable.

SQA Functionality Hardware implementation using 65 MHz Data Acquisition Module provided capability for detailed analysis of antenna feedback. –Amplitude control loops are partially based on antenna feedback. –Lordac functionality is embedded in the control system software. –Analysis of signal quality is used in redundancy and failure analysis decisions. Potential enhancements involve analysis of antenna feedback being applied to: –Pulse to pulse timing and amplitude control. –ECD control.

MVME 2400 Data Processing – Dual Rate

MVME 2400 Data Processing – Single GRI

Summary High utilization of COTS components. –Open system architecture. Partitioning and functional capability provides: –Performance required for the new system. –Allows easy integration into legacy systems. Remote/unattended operation. Graphical user interface provides: –Ease of use. –High visibility into system operation. –Flexible control. Enhanced data analysis and control. –Horsepower for expansion/enhancement.