HIGH POWER SYSTEMS FOR WIND PROFILER

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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.
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1.HIGH POWER TRANSMITTER 2.DUPLEXER
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Transmitter Specifications Frequency
404.37 MHz Bandwidth ? 500 kHz Output
power 16 kW peak Duty cycle 10
maximum Pulse Width 2 -16 ?s Pulse
Repetition Time 100 - 160?s Harmonics
-30 dBc or better Spurious -40
dBc Cooling Forced air
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• Main Subsystems
• HIGH POWER RF AMPLIFIERS
• HIGH AND LOW VOLTAGE POWER SUPPLIES
• RF CONTROL CIRCUITS AND DUAL DIRCTIONAL COUPLER
• CONTROL AND INTERLOCK CIRCUITS

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BLOCK DIAGRAM FOR 16 kW PULSED TRANSMITTER
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HIGH POWER RF AMPLIFIERS
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FIRST OPTION OF 16 kW PULSED TRANSMITTER
43dB
9.5 dB
9 dB
10.5 dB
DR
HPA
16kW
PDR
SSA
1mW
20W
2kW
225W
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SECOND OPTION .
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BLOCK DIAGRAM FOR SOLID STATE AMPLIFIER
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SOLID STATE AMPLIFIER
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Frequency Response of SSA
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• Measured values of Parameters for Solid State
  Amplifier
• Output power 100W Pulsed
• Gain 50 db
• 3 db Bandwidth gt/- 3 MHz
• Efficiency approx 40
• Harmonics/spurious -40db
• Dynamic range gt 5 db

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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
cross-section  and  outer conductor of
rectangular  cross  section  are commonly used.
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FREQUENCY TUNING BY VARYING LENGTH
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FREQUENCY TUNING BY VARYING IMPEDANCE
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BIASING OF 2 kW TRIODE DRIVER AMPLIFIER Grounded
Grid Configuration
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SCHEMATIC OF TRIODE AMPLIFIERS
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DRIVER AMPLIFIER CAVITY 3CPX800A7
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Frequency Response of a Driver Amplifier
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Pulse Response of a Driver Amplifier
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Harmonic Content of a Driver Amplifier
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HIGH POWER AMPLIFIER CAVITY 3CPX3500U7
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Frequency Response of High Power Amplifier
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Pulse Response of High Power Amplifier
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Harmonic Content of High Power Amplifier
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HIGH VOLTAGE AND LOW VOLTAGE POWER SUPPLIES
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• 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

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LOW POWER RF CONTROL CIRCUITS AND DUAL
DIRCTIONAL COUPLER
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AUTOMATIC LEVEL CONTROL

• oOutput power of an amplifier may change due
  to
• Change in ambient temperature,
• Change in supply voltages.
• Requirement
• Level Stability lt 0.1 dB for 1 dB change in
  amplifier gain

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BLOCK DIAGRAM FOR AUTOMATIC LEVEL CONTROL CIRCUIT
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FINAL OUTPUT RESPONSE OF THE TRANSMITTER
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DUAL DIRECTIONAL COUPLER
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CONTROL AND INTERLOCK CIRCUITS
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• SAFETY INTERLOCKS FOR TRANSMITTER
• AIR FLOW
• CATHODE SUPPLY
• PLATE VOLTAGE
• EXCESS PLATE CURRENT
• SSA OVERLOAD
• DOOR
• EXCESS REFLECTION

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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
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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
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TEST RESULTS OF TRANSMITTER
Parameters Specified values Measured
values Output power 16 kW peak gt16
kW peak Bandwidth ? 0.5 MHz gt? 1
MHz Harmonics -30 dBc gt -38 dBc
Spurious Level -40 dBc -55dBc
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16 kW PULSED TRANSMITTER
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DUPLEXER
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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 gt 18.0
dB Transmit mode insertion loss lt 0.5
dB Receive mode insertion loss lt1.0 dB Transmit
mode leakage (isolation) 50.0 dB
Min. Recovery time 3 µs, however effort
will be put to achieve 1 µs
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HIGH POWER BALANCED DUPLEXER
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HIGH POWER BALANCED DUPLEXER WITH INCREASED
ISOLATION
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CIRCULATOR AND DUPLEXER
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CIRCULATOR, DUPLEXER AND LIMITER
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THANK YOU