HIGH POWER SYSTEMS FOR WIND PROFILER HIGH POWER SYSTEMS FOR WIND PROFILER

K. P. RayK. P. Ray

Society for Applied Microwave Electronics Engineering & Research IIT campus, Powai, Mumbai-400 076.

1.HIGH POWER TRANSMITTER

2.DUPLEXER

Transmitter Specifications:

Frequency : 404.37 MHzBandwidth : 500 kHzOutput power : 16 kW peakDuty cycle : 10 % maximumPulse Width : 2 -16 sPulse Repetition Time : 100 - 160sHarmonics : -30 dBc or betterSpurious : -40 dBcCooling : 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

DR HPA

~10.5 dB ~9.5 dB ~9 dB

16kW1mW

43dB

20W 2kW225W

FIRST OPTION OF 16 kW PULSED TRANSMITTER

SSA PDR

DR HPA

~11 dB ~12 dB

16kW1mW

50 dB

100W 1kWSSA

SECOND OPTION ….

BLOCK DIAGRAM FOR SOLID STATE AMPLIFIER

MSA 1101MSA 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

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 + Zo

2)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.

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 AMPLIFIERGrounded 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

oOutput 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 TRANSMITTERFINAL 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 • •

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

Display Indicators :-

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

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

HIGH POWER BALANCED DUPLEXER

WITH INCREASED ISOLATION

CIRCULATOR AND DUPLEXER

LOAD

LNABS

DUPLXER

Rx

Antenna

Tx

+72dBm

+72dBm

16kW

NC

CIRCULATOR, DUPLEXER AND LIMITER

BS

DUPLXER

Rx

Antenna

Tx

+72dBm

+55dBm

16kW

NC

~ 300W

LOAD

LIMITER LNA

THANK YOU