HIGH POWER SYSTEMS FOR WIND PROFILER K. P. Ray K. P. Ray Society for Applied Microwave Electronics Engineering & Research IIT campus, Powai, Mumbai

1.HIGH POWER TRANSMITTER 2.DUPLEXER

Transmitter Specifications: Frequency: MHz Bandwidth:  500 kHz Output power: 16 kW peak Duty cycle: 10 % maximum Pulse Width:  s Pulse Repetition Time:  s Harmonics: -30 dBc or better Spurious: -40 dBc Cooling: Forced air

Main Subsystems: 1.HIGH POWERRF 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

DRHPA ~10.5 dB ~9.5 dB~9 dB 16kW 1mW 43dB 20W 2kW225W FIRST OPTION OF 16 kW PULSED TRANSMITTER SSA PDR

DRHPA ~11 dB~12 dB 16kW 1mW 50 dB 100W 1kW SSA SECOND OPTION ….

BLOCK DIAGRAM FOR SOLID STATE AMPLIFIER MSA 1101 MSA 0520 MHW 720A1MRF 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

Reactance provided by the tube capacitance X c = j Z o tan (2  / ) L The length 'L' of the tuned co-axial line is given by: L = /2  tan -1 X c / Z o Where = wavelength in cm X c = reactance due to the inter-electrode capacitance Z o = characteristic impedance of the line (ohm) The 50 ohm matching point to tap-out the output power is given by: L 2 = /2   R i /R g. [X c /(X c 2 + Z o 2 ) 1/2 ] cm Where L 2 = distance from the short circuited end to the matching point. R i = Output resistance (50 ohm in this case) R g = grid resistance in ohms. Co-axial structure with centre conductor having circular cross- section and outer conductor of rectangular cross section are commonly used. Design Philosophy of Distributed Matching Network for Triode Amplifiers

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 3CPX800A 7

Frequency Response of a Driver Amplifier

Pulse Response of a Driver Amplifier

Harmonic Content of a Driver Amplifier

HIGH POWER AMPLIFIER CAVITY 3CPX3500U 7

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

o Output power of an amplifier may change due to: 1)Change in ambient temperature, 2)Change in supply voltages. Requirement : Level Stability : < 0.1 dB for 1 dB change in amplifier gain AUTOMATIC LEVEL CONTROL

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.FailureRF driveHT supplyFilament 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

Sr. No.ParametersIndicationsLocation 1.Anode voltage (HPA)Analog meterDisplay Panel 2.Anode current (HPA)Analog meterDisplay Panel 3.Grid current (HPA)Analog meterDisplay Panel 4.Anode voltage (Driver)Analog meterDisplay Panel 5.Anode current (Driver)Analog meterDisplay Panel 6.Grid current (Driver)Analog meterDisplay Panel 7.Forward PowerAnalog meterDisplay Panel 8.Reflected PowerAnalog meterDisplay Panel 9.Mains Supply (R, Y, B)LampsMains Panel 10.EHT TimerLampsMains Panel 11.Filament TimerLampsMains Panel 12.Elapsed TimeTime Totalized meterBack Panel 13.DC Voltages (LVPS)Analog meterLVPS Plug in 14.DC Currents (LVPS)Analog meterLVPS Plug in Display Indicators :-

TEST RESULTS OF TRANSMITTER ParametersSpecified 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

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 Transmit mode leakage (isolation):50.0 dB Min. Recovery time:3 µs, however effort will be put to achieve 1 µs Specifications of Duplexer

HIGH POWER BALANCED DUPLEXER

WITH INCREASED ISOLATION

CIRCULATOR AND DUPLEXER LOAD LNABS DUPLXER Rx Antenna Tx +72dBm 16kW NC

CIRCULATOR, DUPLEXER AND LIMITER BS DUPLXER Rx Antenna Tx +72dBm +55dBm 16kW NC ~ 300W LOAD LIMITER LNA

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