Nautel Vector-LP VR125 Technical Instruction Manual

Contents

Page 6-18 Vector-LP Radio Beacon Transmitter Technical Instruction ManualIssue 1.1 Section 6 Theory of Operation6.5.1.3.2 Forward PowerThe Fwd Pwr Sample input (J1-3) is a dcvoltage which represents the forward power atthe transmitter’s RF output. The input is filteredthrough operational amplifier U2D andassociated components. A fwd_pwr_samplesignal is applied to ADC U9 for application tothe front panel’s diagnostic display. Thefwd_pwr_sample input is also applied to theremote interface PWB via the external serialinterface (microcontroller U22). The Fwd PwrSample input is also low-pass filtered throughoperational amplifier U2C and associatedcomponents. A speaker_ref_level signal isapplied through DAC U32. The analog output(pin 12) is filtered through operational amplifierU28D and associated components and appliedto the Audio (Speaker) output (J11-1), thenapplied to speaker LS1 for audio monitoring.6.5.1.3.3 Battery VoltageThe Battery Voltage input (J1-27) is a dcvoltage which represents the voltage appliedfrom the transmitter’s optional battery supply.The input is filtered through operationalamplifier U3B and associated components.The bat_volt_sample signal is applied to ADCU12 for application to the front panel’sdiagnostic display.6.5.1.3.4 Battery CurrentThe Battery Current input (J1-25) is a dcvoltage which represents the current drawnby the transmitter’s optional battery supply.The input is filtered through operationalamplifier U3A and associated components.The bat_cur_sample signal is applied to ADCU12 for application to the front panel’sdiagnostic display.6.5.1.3.5 Low Voltage Power SuppliesAttenuated, buffered samples of all lowvoltage dc power supplies (+24 V, 15 V and+ 5 V) are applied to ADCs U9 and U12 forapplication to the front panel’s diagnosticdisplay.6.5.1.3.6 Cabinet TemperatureLow voltage temperature sensor U5 providesa dc voltage (between 0 and 5 V) whichrepresents the ambient cabinet temperature.This voltage is buffered by operationalamplifier U8A and associated componentsand applied to ADC U12 for application to thefront panel’s diagnostic display.6.5.1.4 MICROCONTROLLERMicrocontroller IC U22 interfaces between thediagnostic display and its associated soft-keys. It controls the level of the Carrier Refsignals (see paragraph 6.5.1.1), whichultimately determines the forward power levelof the transmitter. It also acts as an internaland external serial interface for transmitteralarm and status signals.6.5.1.5 CPLDComplex programmable logic device (CPLD)U18 continuously reads digital inputs for alltransmitter alarm events. It is programmed toperform root cause detection of a fault as wellas high-speed fault protection. Depending onthe nature of the fault, the CPLD generatestransmitter Shutback outputs (J7-1 and J7-2)or various digital control/inhibit signals via aparallel data bus.