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HIGH POWER SYSTEMS FOR WIND PROFILER K. P. Ray Society for Applied Microwave Electronics Engineering & Research IIT campus, Powai, Mumbai-400 076. 1.HIGH POWER TRANSMITTER 2.DUPLEXER Transmitter Specifications: Frequency Bandwidth Output power Duty cycle Pulse Width Pulse Repetition Time Harmonics Spurious Cooling : : : : : : : : : 404.37 MHz 500 kHz 16 kW peak 10 % maximum 2 -16 s 100 - 160s -30 dBc or better -40 dBc Forced air Main Subsystems: 1.HIGH POWER RF AMPLIFIERS 2.HIGH AND LOW VOLTAGE POWER SUPPLIES 3. RF CONTROL CIRCUITS AND DUAL DIRCTIONAL COUPLER 4. CONTROL AND INTERLOCK CIRCUITS BLOCK DIAGRAM FOR 16 kW PULSED TRANSMITTER HIGH POWER RF AMPLIFIERS FIRST OPTION OF 16 kW PULSED TRANSMITTER 43dB ~9.5 dB ~10.5 dB 1mW 20W SSA PDR 225W DR ~9 dB 2kW 16kW HPA SECOND OPTION …. 50 dB ~11 dB 1mW 100W SSA DR ~12 dB 1kW 16kW HPA BLOCK DIAGRAM FOR SOLID STATE AMPLIFIER MSA 1101 MSA 0520 MHW 720A1 MRF 393 SOLID STATE AMPLIFIER Frequency Response of SSA Measured values of Parameters for Solid State Amplifier • Output power : 100W Pulsed • Gain : 50 db • 3 db Bandwidth : >+/- 3 MHz • Efficiency : approx 40% • Harmonics/spurious : -40db • Dynamic range : > 5 db Design Philosophy of Distributed Matching Network for Triode Amplifiers Reactance provided by the tube capacitance Xc = j Zo tan (2/) L The length 'L' of the tuned co-axial line is given by: L = /2 tan-1 Xc / Zo Where = wavelength in cm Xc = reactance due to the inter-electrode capacitance Zo = characteristic impedance of the line (ohm) The 50 ohm matching point to tap-out the output power is given by: L2 = /2 Ri/Rg . [Xc/(Xc2 + Zo2)1/2] cm Where L2 = distance from the short circuited end to the matching point. Ri = Output resistance (50 ohm in this case) Rg = grid resistance in ohms. Co-axial structure with centre conductor having circular crosssection and outer conductor of rectangular cross section are commonly used. FREQUENCY TUNING BY VARYING LENGTH FREQUENCY TUNING BY VARYING IMPEDANCE BIASING OF 2 kW TRIODE DRIVER AMPLIFIER Grounded Grid Configuration SCHEMATIC OF TRIODE AMPLIFIERS DRIVER AMPLIFIER CAVITY 3CPX800A7 Frequency Response of a Driver Amplifier Pulse Response of a Driver Amplifier Harmonic Content of a Driver Amplifier HIGH POWER AMPLIFIER CAVITY 3CPX3500U7 Frequency Response of High Power Amplifier Pulse Response of High Power Amplifier Harmonic Content of High Power Amplifier HIGH VOLTAGE AND LOW VOLTAGE POWER SUPPLIES Power Supply Requirement for Various Amplifier Stages Solid State Amplifier: 28 Volts DC Regulated 12 Volts DC Regulated Driver Amplifier: Plate Voltage: 3.5 kV DC Cathode Voltage: 10.0 Volts DC Filament Voltage: 13.5 Volts AC, 3.5 Amps High Power Amplifier: Plate Voltage: 6.4 kV DC Cathode Voltage: 63.0 Volts DC Filament Voltage: 15.0 Volts AC, 13 Amps LOW POWER RF CONTROL CIRCUITS AND DUAL DIRCTIONAL COUPLER AUTOMATIC LEVEL CONTROL Output power of an amplifier may change due to: o 1)Change in ambient temperature, 2)Change in supply voltages. Requirement : Level Stability : < 0.1 dB for 1 dB change in amplifier gain BLOCK DIAGRAM FOR AUTOMATIC LEVEL CONTROL CIRCUIT FINAL OUTPUT RESPONSE OF THE TRANSMITTER DUAL DIRECTIONAL COUPLER CONTROL AND INTERLOCK CIRCUITS SAFETY INTERLOCKS FOR TRANSMITTER AIR FLOW CATHODE SUPPLY PLATE VOLTAGE EXCESS PLATE CURRENT SSA OVERLOAD DOOR EXCESS REFLECTION Interlock Scheme for the Transmitter S.NO. Failure RF drive HT supply Filament supply 1. Tube cooling blower • • • 2. Rack exhaust fan • • • 3. Cathode supply • • • 4. Excess anode current • • 5. Reflected power (VSWR) • 6. Duplexer • 7. Door/Panel • • Display Indicators :Sr. No. Parameters Indications Location 1. Anode voltage (HPA) Analog meter Display Panel 2. Anode current (HPA) Analog meter Display Panel 3. Grid current (HPA) Analog meter Display Panel 4. Anode voltage (Driver) Analog meter Display Panel 5. Anode current (Driver) Analog meter Display Panel 6. Grid current (Driver) Analog meter Display Panel 7. Forward Power Analog meter Display Panel 8. Reflected Power Analog meter Display Panel 9. Mains Supply (R, Y, B) Lamps Mains Panel 10. EHT Timer Lamps Mains Panel 11. Filament Timer Lamps Mains Panel 12. Elapsed Time Time Totalized meter Back Panel 13. DC Voltages (LVPS) Analog meter LVPS Plug in 14. DC Currents (LVPS) Analog meter LVPS Plug in TEST RESULTS OF TRANSMITTER Parameters Specified values Measured values Output power: 16 kW peak >16 kW peak Bandwidth: 0.5 MHz > 1 MHz Harmonics: -30 dBc > -38 dBc Spurious Level: -40 dBc -55dBc 16 kW PULSED TRANSMITTER DUPLEXER Specifications of Duplexer Total input power : 16 kW peak Average power : 1.6 kW Pulse width : 2 µs & 16 µs (coded) Transmit port Return loss : > 18.0 dB Transmit mode insertion loss : < 0.5 dB Receive mode insertion loss : <1.0 dB leakage (isolation) : 50.0 dB Min. Recovery time : 3 µs, however effort will Transmit mode be put to achieve 1 µs HIGH POWER BALANCED DUPLEXER HIGH POWER BALANCED DUPLEXER WITH INCREASED ISOLATION CIRCULATOR AND DUPLEXER Antenna Rx NC Tx +72dBm BS +72dBm 16kW DUPLXER LOAD LNA CIRCULATOR, DUPLEXER AND LIMITER Antenna LOAD Rx Tx NC +55dBm LIMITER +72dBm 16kW ~ 300W DUPLXER BS LNA THANK YOU