www.cpii.com/bmd

VPC3534

C-Band Klystron Transmitter

Communications & Power Industries Klystron Transmitter

FEATURES:

• 250 kW peak power RF output

• Modular design for ease of customization

• Air cooled

BENEFITS:

• CPI BMD Klystrons and modulators ensure

compatible performance

• Easy to use and user friendly

• Built in diagnostics and BIT for local or remote

troubleshooting.

APPLICATIONS:

• Weather radars

• Instrumentation radars

The CPI BMD 250 kW, C-band, klystron trans-

mitter components for weather radar are avail-

able for constructing a complete microwave

transmitter. This microwave transmitter uses a

CPI klystron ampliﬁer (VKC8387) as the ﬁnal RF

output device. CPI is able to furnish a compact,

user-friendly, cost-effective microwave power

source with excellent pulsed Doppler capabili-

ty.

The typical assemblies that CPI provides to

weather radar integrators are: high voltage

power supply, Solenoid power supply, Solenoid

for the klystron, 250 kW C-band klystron, solid

state switch and the high voltage oil tank

assembly which includes the pulse transformer,

energy storage high voltage capacitor, ﬁlament

power supply. The weather radar integrators

will install these components into their transmit-

ter / receiver cabinet and supply the receiver,

system controller, RF synthesizer and pre-ampli-

ﬁer and cooling.

The CPI BMD subsystem components are a high

voltage power supply that provides 5 kW of

energy at 2 kV DC to the solid state switch assem-

bly. The solid state switch assembly must be

located close to the high voltage oil tank assem-

bly so that there is minimal inductance in the

buss-line that is carrying the current to the

step-up transformer. In addition to the step-up

transformer in the high voltage oil tank assembly

there is the energy storage capacitor and the

ﬁlament supply.

VPC3534

CPI Klystron Transmitter pg. 2

www.cpii.com/bmd

The high voltage power supply converts input

AC into DC then switches it at a 50 kHz rate

utilizing a short-circuit proof series resonant

inverter. Auxiliary power supplies needed to

operate the klystron are contained in this unit,

including a ﬁlament power source, ion pump

source, and low voltage bias supplies. All

external interface and control is done in this

supply. Cooling is accomplished by internal

fans.

The solenoid power supply is contained in a

separate 19 inch rack power supply that is 5.25

inches high by 21.5 inches deep. It has a similar

approach as the high voltage power supply, AC

is converted to DC then a high frequency

inverter converts the power to the direct

current that the solenoid requires. The sole-

noid power supply is current controlled as the

voltage to the coil will change as the tempera-

ture of the solenoid coil changes.

Beam switching is done by a completely

solid-state array of IGBT switch boards that is

driven by the control interface board in the high

voltage power supply. This switch inherently

limits current and pulse by design; no external

circuitry is required for these functions. The

IGBT switch is also a current controlled switch,

set by a bias voltage from the high voltage

power supply control interface board.

The voltage across the switch will change auto-

matically as the voltage across klystron changes

due to frequency and temperature changes.

This switch is also will inherently limit arc current

in the event of a klystron HV arc. The limit is

less than twice the normal operating current in

the event of a complete short circuit. The size

of this switch assembly is 12 inches high by 10

inches deep by 6 inches wide and has integral

fans to cool the switches.

All high voltage is contained in an oil tank which

is 18 inches high by 23 inches wide and 20

deep. The pulse transformer that steps up the

2 kV high voltage power supply output to the

50 kV that the klystron requires, storage capaci-

tor bank to supply the energy during the pulse,

and the klystron ﬁlament DC ﬁlter are all con-

tained in this oil tank. The Solenoid and the

klystron are mounted on the top of the oil tank

with the bushing of the klystron going through

the top of the oil tank and is immersed in the

oil. External fans are required to cool the

klystron and the solenoid. The fans should be

interlocked as the klystron and Solenoid can be

damaged if sufﬁcient cooling is not supplied.

Instrumentation and control

The system controller must provide 4 signals to

the high voltage power supply to operate the

klystron transmitter. They are a +15 V power-on

signal that closes the main power contactor,

+15 V that commands high voltage to be sup-

plied to the IGBT switch, a +15 V gate that

determines the duration that the IGBT switch is

on (which determines the duration of the

klystron beam pulse) and a contact

closure-to-ground for a latched fault reset.

These are all the signals necessary to operate

the klystron transmitter.

The high voltage

power supply is a 19

inch rack mount unit,

8 inches high by 21.5

inches deep. It is

completely self-pro-

tected with over

current and input

under/over voltage

circuits.