TCI Mobile Spectrum Monitoring System

TCI Mobile Spectrum Monitoring System

The mobile SMS has the capability of "homing" DF while the vehicle is moving and the antenna is in the stowed position.  Homing DF is used to track down sources of interference and illegal transmissions. 

The Mobile SMS has the same monitoring, DF and homing capabilities while it is on the move as it does when stationary. When the VHF/UHF antenna is in its stowed position it does lose some sensitivity and distance in its ability to DF and Monitor as the antenna is no longer extended at its full height.

"Drive Down" or homing DF is one of the TCI mobile’s outstanding features. The vehicle has the ability to take DF cuts while on the move. This allows a single vehicle to perform what is essentially triangulation on a signal of interest. The operator can narrow down the area where a signal-of-interest is and "Drive Down" on it.

TCI Model 5093 Processor includes multi-channel VHF/UHF receiver, A/D and DSP resources needed to perform signal monitoring and direction finding. It should be noted that the processor is capable of performing both Angle-of-Arrival (AOA) and, as an option, Time-Difference-of-Arrival (TDOA) measurements that can be used for Geo-location of signal sources.

The VHF/UHF and HF receivers are capable of processing and demodulating AM (SSB and ISB), FSK and FM (NB and WB) analog signals, and can monitor and DF on all modern digital signals.  The receiver’s sensitivity meets or exceeds Spectrum Monitoring System (SMS) requirements and specifications, including the field strength sensitivity measurements.  The system provides sufficient SNR at the receiver output to support DF and signal strength measurement operations.

The system utilizes multi-channel correlative interferometry to provide Angle Of Arrival (AOA) bearings even in difficult RF conditions, such as multi-path. Multi-channel DF provides better and faster DF than a single-channel system and enables the system to locate many different types of signals, including those that are frequency agile and/or have complex digital modulations.

The processor’s Built-In-Self-Test functionality ensures operators and maintenance personnel the system is operating properly and reports any anomalies for further action.

The TCI Model 735 Mobile Monitoring Systems include a high degree of Built-in Test/Self calibration capabilities which generate test signals and perform end-to-end testing of the entire system to detect component failures and degradation of system performance without the use of external test equipment or operator intervention. TCI systems include a patented self-calibration feature that runs automatically or on manual command that ensures correct performance of the system.

The TCI spectrum processor test and calibration sequence uses synthesized signal generators (built-in test equipment) to make over 3000 measurements consisting of over 200,000 data points to calibrate the receivers and digitizer. This insures the measurement accuracy of the units without need for external test equipment or “return to factory” calibration procedures. In addition, this test data is used by built-in test analysis software to simplify diagnostic trouble shooting and maintenance.

The TCI VHF/UHF antennas also include extensive Built-In-Test-Equipment (BITE) and Built-in Calibration (CAL) circuits. These circuits, controlled by the TCI Spectrum Processor, allow the Spectrum Processor to test and calibrate proper operation of the antenna and the internal RF switches and preamps for both DF and monitoring functions.

It is essential for any DF system that the amplitude and phase of measured antenna voltages to be representative of the characteristics of the target signal and not be corrupted by mismatch in system components. Traditional DF systems use components that are matched at the factory and require difficult alignment procedures to maintain system performance within specifications. TCI has developed a digital calibration technique that is performed automatically each time the system power is turned on. During calibration, the system measures the amplitude and phase characteristics of each channel across the operating passband and saves these correction coefficients in memory. In normal DF operation, the raw measurements from each receiver are automatically corrected by these coefficients, resulting in a near perfect match between channels. This digital calibration technique results in overall instrument accuracy of 0.1° RMS for the TCI DF system.

The Direction Finding (DF) technique used in the TCI Model 735 VHF/UHF SMS is an implementation of correlative interferometry. DF data is obtained from the VHF/UHF antenna array as sampled by the dual-channel receiver. DF instrument accuracy is 0.1º over the full frequency range. System DF accuracy is dependent on the antenna selected but is typically 1º RMS in a scatter free environment (2º RMS typical) over the full frequency range and is independent of the modulation of the signal. Please see the antenna data shfeets for specific performance data.

DF bearing results include a "Confidence Factor" (0-100) - an indication of the reliability of the measurement, related to several factors including the signal strength (received SNR) at the time of measurement.

The TCI equipment performs DF functions in accordance with the ITU recommendations, SM.854-1, 1053, 1269 and the ITU Spectrum Monitoring Handbook (2011) Chapter 4.7. The TCI Model 735 series of systems have been extensively tested in the laboratory and in the field on more than 100 sites worldwide, and no limit to performance was found.

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