AR 3000TP12G18 Service manual

Operating and
Service Manual
3000TP12G18
Model
10031733
Part Number
Serial Number
160 School House Road, Souderton, PA 18964 • 215-723-8181 • Fax [phone] • www.arworld.us

EC Declaration of Conformity
We; Amplifier Research
160 School House Road
Souderton, PA. 18964
declare that our product(s);
the Models 3000TP12G18 series RF amplifiers
to which this declaration relates is in compliance with the requirements of the:
EEC EMC Directive (89/336/EEC) in accordance with Article 10 (2) of the directive, with the provision
that the user must install the equipment as directed by the “Instructions for European EMC Conformity” in
the Operating and Service Manual.
This product(s) is in compliance with the requirements of the Low Voltage Directive (72/23/EEC) in
accordance with safety standard IEC EN60950 (1995).
The CE marking is affixed on the device according to the EC Directives.
James M, Maginn
President

Instructions for European EMC Conformity
WARNING
It is the responsibility of the user of this equipment to provide electromagnetic shielding, filtering and isolation
which is necessary for EMC compliance to Directive 2014/30/EU. The equipment must therefore be operated in
a shielded area which provides a sufficient level of attenuation to meet the radiated emissions and immunity
specifications. The following minimum levels are suggested for use in accordance with the rated power of the
equipment.
Rated Power
Minimum shielding attenuation
100 watts
50 dB
101 - 1000 watts
60 dB
1001 - 10,000 watts
70 dB
Since this equipment is designed to generate high levels of Radio Frequency energy, it is also essential that the
user read and follow the “Instructions for Safe Operation” in this manual. If other equipment is operated in the
shielded room it may be disturbed by the amplifier.
ACHTUNG
Der Benutzer dieses Gerätes ist dafür verantwortlich, daß die elektromagnetische Abschirmung und Filterung
gewährleistet ist, welche gemäß Richtlinie 2014/30/EU notwendig ist. Das Gerät muß deshalb in einem
geschirmten Raum betrieben werden, welcher eine ausreichenden Schirmung bietet, um die Emissions- und
Störfestigkeitsspezifkation einzuhalten. Es werden folgenden Minimalwerte der Schirmdämpfung und Filterung
in den unterschiedlichen Leistungsklassen empfohlen.
Hochfrequenzleistung
min. Schirmdämpfung
100 Watt
50 dB
101-1000 Watt
60 dB
1001-10.000 Watt
70 dB
Falls andere elektrische oder elektronische Geräte gleichzeitig mit dem Gerät betrieben werden, kann es zu
Beeinflussungen kommen. Da das Gerät zur Erzeugung von Hochfrequenzenergie dient ist es daher auch
unbedingt notwendig, daß der Benutzer die Sicherheitsvorschriften in der Bedienungsanleitung liest und einhält.
AVERTISSEMENT
Il est de la responsabilité de l'utilisateur de cet équipement d'assurer la protection électromagnétique, le filtrage et
l'isolation nécessaires, afin de se conformer à la directive 2014/30/EU concernant la C.E.M. Par conséquent, cet
équipement doit être mis en fonctionnement dans une enceinte d'atténuation suffisante pour satisfaire aux
spécifications d'émissivité et de susceptibilité. Pour une utilisation conforme, les niveaux d'atténuation minimums
suivants sont suggérés en fonction de la puissance de sortie de l'équipement:
Puissance de sortie
Atténuation minimum de l'enceinte
100 Watts
50 dB
101 à 1.000 Watts
60 dB
1.001 à 10.000 Watts
70 dB
Puisque cet équipement est destiné à générer de forts niveaux R.F., il est essentiel que l'utilisateur se conforme
aux instructions de sécurité indiquées dans ce manuel. Tout autre équipement en fonctionnement dans la cage de
Faraday peut-être perturbé par 1'amplificateur.

INSTRUCTIONS FOR SAFE OPERATION
Revised 0517
Observe the following safety guidelines to help ensure your
own personal safety and to help protect your equipment and
working environment from potential damage.
INTENDED USE
This equipment is intended for general laboratory use in
generating, controlling, and measuring levels of
electromagnetic Radio Frequency (RF) energy. Ensure that the
device is operated in a location which will control the radiated
energy and will not cause injury or violate regulatory levels of
electromagnetic interference.
SAFETY SYMBOLS
These symbols may appear in your user manual or on
equipment.
This symbol is marked on the equipment when it
is necessary for the user to refer to the manual for
important safety information.
The caution symbol denotes a potential hazard.
Attention must be given to the statement to
prevent damage, destruction, or harm.
Dangerous voltages are present. Use extreme
care.
Indicates a terminal intended for connection to an
external conductor for protection against
electrical shock in case of a fault, or the terminal
of a protective earth (ground) electrode.
Indicates invisible laser radiation–do not view
directly with optical instruments.
Indicates frame or chassis ground connection
terminal.
Indicates alternating current.
Indicates this product must not be disposed of
with your other household waste.
Indicates that the marked surface and adjacent
surfaces can attain temperatures that may be hot
to the touch.
EQUIPMENT SETUP PRECAUTIONS
Review the user manual and become familiar with
all safety markings and instructions. Protection
provided by the equipment may be impaired if used
in a manner not specified by AR RF/Microwave
Instrumentation (AR).
•Follow all lifting instructions specified in this document.
•Place the equipment on a hard, level surface.
•Do not use the equipment in a wet environment, for
example, near a sink, or in a wet basement.
•Position your equipment so that the power switch is easily
accessible.
•Leave 10.2 cm (4 in) minimum of clearance on all vented
sides of the equipment to permit the airflow required for
proper ventilation. Do not restrict airflow into the
equipment by blocking any vents or air intakes. Restricting
airflow can result in damage to the equipment, intermittent
shut-downs or safety hazards.
•Keep equipment away from extremely hot or cold
temperatures to ensure that it is used within the specified
operating range.
•While installing accessories such as antennas, directional
couplers and field probes, take care to avoid any exposure
to hazardous RF levels.
•Ensure that nothing rests on your equipment’s cables and
that the cables are not located where they can be stepped
on or tripped over.
•Move equipment with care; ensure that all casters and/or
cables are firmly connected to the system. Avoid sudden
stops and uneven surfaces.
BEFORE APPLYING POWER
Your AR equipment may have more than one power supply
cable. Use only approved power cable(s). If you have not been
provided with a power cable for the equipment or for any AC-
powered option intended for the equipment, purchase a power
cable that is approved for use in your country. The power cable
must be rated for the equipment and for the voltage and current
marked on the equipment’s electrical ratings label.
Incorrectly installing or using an incompatible line
voltage may increase the risk of fire or other
hazards. To help prevent electric shock, plug the
equipment and peripheral power cables into properly grounded
electrical outlets. These cables are equipped with three-prong
plugsto help ensureproper grounding. Do not use adapter plugs
or remove the grounding prong from a cable.
Do not modify power cables or plugs. Consult a licensed
electrician or AR trained service technician for equipment
modifications. Always follow your local/national wiring rules.
Do not operate the equipment if there is physical
damage, missing hardware, or missing panels.
SAFETY GROUND
This equipment is provided with a protective earth
terminal. The mains power source to the equipment
must supply an uninterrupted safety ground of
sufficient size to attach wiring terminals, power
cord, or supplied power cord set. DO NOT USE this equipment
if this protection is impaired.

INSTRUCTIONS FOR SAFE OPERATION
HAZARDOUS RF VOLTAGES
The RF voltages on the center pin of an RF output
connector can be hazardous. The RF output
connector should be connected to a load before AC
power is applied to the equipment. Do not come into
contact with the center pin of the RF output connector or
accessories connected to it. Place the equipment in a non-
operating condition before disconnecting or connecting the load
to the RF output connector.
ACOUSTIC LIMITATIONS
If equipment noise exceeds 80dB, ear protection is required.
MAINTENANCE CAUTION
Adjustment, maintenance, or repair of the equipment must be
performed only by qualified personnel. Hazardous energy may
be present while protective covers are removed from the
equipment even if disconnected from the power source. Contact
may result in personal injury. Replacement fuses are required
to be of specific type and current rating.
ENVIRONMENTAL CONDITIONS
Unless otherwise stated on the product specification sheet, this
equipment is designed to be safe under the following
environmental conditions:
•Indoor use
•Altitude up to 2000m
•Temperature of 5°C to 40°C
•Maximum relative humidity 80% for temperatures up to
31°C. Decreasing linearly to 50% at 40°C.
•Main supply voltage fluctuations not to exceed ± 10% of
the nominal voltage or minimum and maximum
autoranging values.
•Pollution degree 2: Normally non-conductive with
occasional condensation. While the equipment will not
cause hazardous condition over this environmental range,
its performance may vary.
EQUIPMENT CONTAINING LASERS
AR Field Probes (FL/PL Series) and Field Analyzers
(FA Series) are Class 1 laser products containing
embedded Class 4 lasers. Under normal use, the
laser radiation is completely contained within the
fiber optic cables and poses no threat of exposure. Safety
interlocks ensure that the laser is not activated unless the cables
are properly connected. Always exercise caution when using
or maintaining laser products. Do not view directly with optical
instruments.
RF ANTENNAS
•This equipment (antenna or antenna assembly) may be
heavy, requiring two persons to lift. Use caution when
installing or removing unit. Follow all equipment setup and
lifting instructions specified in this document.
•Ensure connectors are appropriate for intended operation.
Connectors are specified in the user manual and product
specification sheet.
•Do not exceed the maximum RF input level stated in the
specifications. Refer to the user manual and product
specification sheet to determine the applicable RF levels.
•Excessive RF input could damage the equipment or
connectors, causing safety hazards.
•When in operation, the RF voltages on the antenna
elements can be hazardous. Do not come into contact with
the antenna or elements when the RF input connector is
connected to a live RF source.
•To avoid injury to personnel and accidental damage to
power amplifier or antenna, disable the RF output of power
amplifier before connecting or disconnecting the input
connection to the antenna.
•Perform periodic inspections of antenna and field probe
systems to verify calibration due date, proper operation,
and overall condition of equipment.
RACK MOUNTED TWT MODELS
Some TWT models are supplied without the removable
enclosure offered for benchtop use. These rack-mountable
models may be supplied with either carry handles or slides and
front handles installed. Follow all lifting instructions specified
in this document and installation instructions supplied in the
TWT user manual.
LIFTING INSTRUCTIONS FOR AR EQUIPMENT
Because most products must be
handled during distribution, assembly
and use, the risk of serious injury due
to unsafe product handling should be
a fundamental consideration of every
user. An authoritative guideline for
eliminating unwarranted risk of injury caused by lifting is
provided by the NIOSH Work Practices (Publication #94-110)
available at:
https://www.cdc.gov/niosh/docs/94-110/pdfs/94-110.pdf.
In general, observe the following guidelines for lifting a weight
of 50 lb or more:
•Use lifting eye (for floor standing) or side handles (table
top) to lift unit only.
•Use equipment of adequate capacity to lift and support unit.
•If using forklift to move unit, be sure forks are long enough
to extend beyond the side of the unit.
•For additional information, follow the link specified above.

ADDITIONAL WARNINGS & NOTES
WARNING:
This equipment operates at potentially lethal voltages. Only trained,
qualified personnel should operate, maintain, or service it.
CAUTION:
The information in this document was obtained from reliable sources and
was believed to be accurate at the time of publication. Since subsequent
modifications to the machine may have been made, use this information
only as a guide. Carefully compare the unit's actual configuration and
operation to the descriptions in this manual before you undertake to
operate, service, or modify this machine. Any variance or modification
should be noted, dated, and initialed in the discrepant part of all manuals
on hand for future reference. If you have technical or editorial comments
you wish to make to the manufacturer, please write them on photocopies
of the relevant sheets.
NOTE: The contents of this document are the property of the manufacturer and this document is delivered
on the express condition that it not be disclosed, reproduced in whole or in part, or used for manufacture
for anyone other than the manufacturer without its written consent, and that no right is granted to disclose
or so use any information in this document.

Model 3000TP12G18

Suggested Periodic Maintenance for TWT Amplifiers
1. Keep monthly log of the voltages, currents and temperatures as shown on Menus. Also record
Date, “Console” and “Operate” hours. Take readings in Operate mode with the gain at zero
(0%) percent. Leave unit in Operate mode for 20 minutes (Max Duty if Pulsed Unit), and then
record data. Review the log to identify trends and contact factory if required.
2. Keep monthly log of performance with active RF. At mid-band frequency, with Gain set to
100%, apply RF drive that will provide rated power. This will help indicate if the gain or power
is changing and if the traveling wave tube or pre-amp needs service. Record the following:
a. RF Drive Level
b. Forward Power
c. Reverse Power
d. Body Current (Iw)
e. Sample Port Power reading (if possible).
3. Remove air intake filter and clean using compressed air and/or vacuum cleaner.
4. Ensure air inlet and outlet are unobstructed.
5. Check that AC Input connections are secure. Make sure the AC cable is not damaged or
deteriorated.
6. Check that both input and output RF connections (waveguide or coax) are connected tightly and
un-damaged.
Rev A

i
TABLE OF CONTENTS
TABLE OF CONTENTS ..................................................................................................i
1. DESCRIPTION AND SPECIFICATIONS.......................................................1
1.1 TWTA Description................................................................................................1
1.2 Suggested Applications..........................................................................................1
1.3 Specifications.........................................................................................................1
1.5 Test Data Sheet......................................................................................................1
2. THEORY OF OPERATION ..............................................................................5
2.1 Design of the Amplifier.........................................................................................5
2.2 Description of the RF Subsystem ..........................................................................5
2.3 Description of the Power Supply Subsystem.........................................................5
2.3.1 Low Voltage Power Supply Module: ....................................................................5
2.3.2 Logic and Control Module:....................................................................................6
2.3.3 Power Factor Corrector Module............................................................................ 6
2.3.4 Power Board Assembly: ........................................................................................6
2.3.5 Diode/Cap Assembly.............................................................................................6
2.3.6 High Voltage Filter................................................................................................6
2.3.7 Heater Power Supply Module................................................................................6
2.3.8 Grid Modulator Module.........................................................................................6
3. OPERATION.......................................................................................................7
3.1 Warnings and Cautions..........................................................................................7
3.2 Installation .............................................................................................................8
3.2.1 Unpacking..............................................................................................................8
3.2.2 Mounting................................................................................................................8
3.2.3 Cooling Requirements ........................................................................................... 9
3.2.4 AC Line Power Connections .................................................................................9
3.2.5 RF Connections....................................................................................................10
3.3 Front Panel Features ............................................................................................11
3.4 Rear Panel Features .............................................................................................12
3.5 Front Panel Display and Soft Keys......................................................................16
3.5.1 Overview..............................................................................................................16
3.5.2 Menu Screens.......................................................................................................18
3.5.3 Setup Screens.......................................................................................................18
3.5.4 Sleep Mode..........................................................................................................19
3.5.5 Warning Screens..................................................................................................19
3.5.6 Miscellaneous Screens.........................................................................................20
3.6 Initial Turn On and Warm-up Procedure.............................................................21
3.7 Remote IEEE-488 Operation............................................................................... 22
3.8 RF Operation ....................................................................................................... 27
3.9 TWTA General Considerations ...........................................................................28
4. MAINTENANCE...............................................................................................31
4.1 Safety Warning....................................................................................................31
4.2 Unauthorized Repairs ..........................................................................................31
4.3 Preventive Maintenance.......................................................................................31

Model 4000TP8G12
ii
4.4 Troubleshooting...................................................................................................33
4.5 Non-Repairable Modules..................................................................................... 33
4.6 Recommended Spare Parts ..................................................................................34
5. TECHNICAL DOCUMENTATION ...............................................................35
5.1 Schematics...........................................................................................................35
5.2 Parts Lists.............................................................................................................35
5.3 Top Level Build Tree...........................................................................................35
5.4 Sample Program for IEEE-488 Communication .................................................35
FIGURES
3-1 Front Panel Features ............................................................................................11
3-2 Rear Panel Features .............................................................................................12
3-3 Soft Key Locations ..............................................................................................16
3-4 Menu Tree............................................................................................................17
TABLES
3-1 Front Panel Features ............................................................................................11
3-2 Rear Panel Features .............................................................................................12
3-3 Catalog of IEEE-488 Commands.........................................................................22
3-4 Catalog of Status Codes.......................................................................................24
3-5 Catalog of Fault Codes ........................................................................................25
3-6 Catalog of System State Codes............................................................................26
3-7 Catalog of *STA?; Response Codes.................................................................... 26
3-8 Catalog of *STB?; Response Codes.................................................................... 27
3-9 Catalog of Heater Auto Off Time Delay Codes...................................................27

Rev A 1
1. DESCRIPTION AND SPECIFICATIONS
This manual provides operating, interfacing and selected service information pertinent to Amplifier
Research Model 3000TP12G18 Broadband Microwave Amplifier. The Model 3000TP12G18 is a 3000
watt pulsed Ku-band traveling-wave tube amplifier (TWTA).
1.1 TWTA DESCRIPTION
The amplifier uses a 3,000 watt traveling-wavetube (TWT) to provide 3,000 watts minimum output over the
TWT amplifier's full bandwidth, higher in other parts of the band. The amplifier is well suited for applications
where instantaneous bandwidth and high gain are required. The amplifier is completely self-contained and
packaged for standard 19-inch rack mounting.
Primary power is 190-260 volts 50-60 Hz., single phase. An efficient switching power supply design provides
minimum power consumption. A fast regulation control loop and a high degree of filtering ensure performance
within specifications over a wide range of operating conditions. The amplifier is fully enclosed, and the upper
and lower panels of the rack mountable amplifier are interlocked to reduce the likelihood of accidental contact
with high voltage.
1.2 SUGGESTED APPLICATIONS
•RF Susceptibility testing
•Antenna and component testing
•Equipment calibration
•General laboratory instrumentation
1.3 SPECIFICATIONS
Refer to the AR RF/Microwave Instrumentation Data Sheet at the end of this section for detailed specifications.
1.5 TEST DATA SHEET
A Test Data Sheet for a specific unit is prepared at the time of manufacture and is included with the unit's copy
of this manual.

Model 3000TP12G18
2 Rev A

voltage, heater current, heater voltage,
baseplate temperature and cabinet temperature.
Modular design of the power supply and RF
components allow for easy access and repair.
Use of switching mode power supplies results in
significant weight reduction.
Housed in a stylish contemporary cabinet, the
amplifier provides readily available pulsed RF
power for a variety of applications in Test and
Measurement, (including EMC RF pulse suscepti-
bility testing), Industrial and University Research
and Development, and Service applications. AR
also offers a broad range of amplifiers for CW
(Continuous Wave) applications.
The export classification for this equipment is
3A999.d. These commodities, technology or
software are controlled for export in accordance
with the U.S. Export Administration Regulations.
Diversion contrary to U.S. law is prohibited.
See Model Configurations for alternative prime
power, packaging, and special features.
The Model 3000TP12G18 is a self contained,
forced air cooled, broadband traveling wave
tube (TWT) microwave amplifier designed for
pulse applications at low to moderate duty fac-
tors where instantaneous bandwidth and high
gain are required. A reliable TWT provides a
conservative 3000 watts minimum peak RF pulse
power at the amplifier output connector. Stated
power specifications are at the fundamental fre-
quency.
The amplifier's front panel digital display shows
forward and reflected average power output or
forward and reflected peak power, plus extensive
system status information accessed through a
series of menus via soft keys. Status indicators
include power on, warm-up, standby, operate,
faults, excess average or peak reflected power
warning and remote. Standard features include
a built-in IEEE-488 (GPIB) interface, 0dBm input,
TTL Gating, VSWR protection, gain control, RF
output sample port, auto sleep, plus monitoring
of TWT helix current, cathode voltage, collector
Features
Specifications
3000TP12G18
 Pulse Amplifier
 M1–M8
 3000 Watts
 12GHz–18GHz
AR RF/Microwave
Instrumentation
160 School House Rd
Souderton, PA 18964
215-723-8181
For an applications engi-
neer call:800.933.8181
www.arworld.us

POWER (Fundamental), Peak Pulse, @ Output: Nomi-
nal, 3800 watts; Minimum, 3000 watts
FLATNESS: ±10 dB maximum
FREQUENCY RESPONSE: 12–18 GHz
INPUT FOR RATED OUTPUT: 1.0 milliwatt maximum
GAIN (at maximum setting): 65 dB minimum
GAIN ADJUSTMENT (continuous range): 35 dB mini-
mum
INPUT IMPEDANCE: 50 ohms, VSWR 2.5:1 maximum
OUTPUT IMPEDANCE: 50 ohms, VSWR 2.5:1 typical
MISMATCH TOLERANCE: Output pulse width foldback
protection at peak reflected power exceeding 1000
watts. Will operate without damage with any magni-
tude and phase of source and load impedance. May
oscillate with unshielded open due to coupling to in-
put. Should not be tested with connector off. See S2M
special option, if applicable.
NOISE POWER DENSITY:
(pulse on) Minus 55 dBm/Hz (maximum);
Minus 65 dBm/Hz (typical)
(pulse off) Minus 140 dBm/Hz (typical)
HARMONIC DISTORTION: Minus 8 dBc maximum
PRIMARY POWER: See Model Configurations
PULSE CAPABILITY:
Pulse Width 0.07–50 microseconds.
Pulse Rate (PRF) 100 kHz maximum
Duty Cycle 4% maximum.
RF Rise and Fall 30 ns max (10% to 90%).
Delay 300 ns maximum from pulse
input to RF 90%
Pulse Width Distortion ±30 ns maximum (50% points
of output pulse width compared
to 50% points of input pulse
width)
Pulse Off Isolation 80 dB minimum, 90 dB typical
Pulse Input TTL level, 50 ohm nominal
termination
CONNECTORS:
RF input: Type N female, rear panel
RF output: Type WR62 waveguide flange, rear
panel
RF output forward sample port :
Type N female, rear panel
Pulse input: Type BNC female, rear panel
GPIB: IEEE-488 female, rear panel
Interlock: DB-15 female, rear panel
COOLING: Forced air (self contained fans), air entry
and exit in rear.
SIZE: 50.3 x 26 x 81 cm (19.8 x 10 x 31.9 in)
WEIGHT: 52 kg (115 lbs)
EXPORT CLASSIFICATION: 3A999.d
Page 2
Specifications
3000TP12G18
 Pulse Amplifier
 M1–M8
 3000 Watts
 12GHz–18GHz
EPackage Alternatives. May select an alternative
from the following [E1C or (E1C and E2S) and/
or E3H]:
E1C Cabinet: Without outer enclosure for rack
mounting, size (W x H x D) 49 x 22 (5U) x 68
cm, 19 x 8.75 (5U) x 26.8 in., Subtract approx-
imately 11 kg, 25 lbs, for removal of outer
enclosure.
E2S Slides: slides installed, add approximately 2 kg,
5 lbs.
E3H Handles: Front pull handles installed.
PPrimary Power: Must select one primary power
from the following [P1 or P2]
P1 208 VAC ± 10% 3-phase, 50/60 Hz, 2.0 KVA
maximum
P2 190-260 VAC single phase, 50/60 Hz, 2.0
KVA maximum
SSpecial Features: May select a special feature
(extra cost) from the following [S1R or S2M]:
S1R Reflected power sample port, type N female
connector on rear panel. Forward and reflect-
ed sample port calibration data supplied on
disk in Excel format at 51 points, evenly spaced
over specified frequency response.
S2M Special Mismatch Tolerance Operation: Ampli-
fier will permit up to 1.9kW reflected power at
maximum 8μs pulse width and .8% duty, with-
out VSWR trip or fold-back. Exceeding 1.9kW
reflected power will cause the unit to truncate
pulse within 2μs. For pulses beyond 8μs, ex-
ceeding 1kW will cause the unit to truncate the
pulse. If exceeding .8% duty with reflected
Model Configurations
power exceeding 1kW, the amplifier will trun-
cate the pulse within 2μs. The amplifier will
continue to truncate pulses until reflected power
dissipates from outside source. Operation with
truncated pulses for >250mS will result in
latched “Truncated Pulse Fold Back” displayed
on screen and over the remote interface, in-
cluding an audible alarm. Operation with trun-
cated pulses for 5 to 10 seconds will cause
“Over Reverse” fault and a shutdown of high
voltage and the amplifier.
To order AR Products, call 215.723.8181. For an applications engineer call:800.933.8181. Direct to Service call: 215.723.0275 or
email: [email protected] For Faxing Orders:866.859.0582 (Orders Only Please) [email protected]s
Approved for public release by AR RF/Microwave Instrumentation 080416
Model Number
Features
EPS
3000TP12G18 Base model P2 –
M1 E1C P2 –
M2 E3H P2 –
M3 E1C & E3H P2 –
M4 E1C & E2S P2 –
M5 E1C & E2S
& E3H
P2 –
M6 –P2 S1R
M7 –P1 S2M
M8 –P1 –
Model number example: Model 3000TP12G18M2
would have option E3H front pull handles installed.

Rev A 5
2. THEORY OF OPERATION
2.1 DESIGN OF THE AMPLIFIER
The Model 3000TP12G18 TWT amplifier consists of two main subsystems. The power supply subsystem and
the RF subsystem, which are discussed in Sections 2.2 and 2.3, respectively.
These two subsystems work in conjunction with the control system. The heart of the microprocessor control
system is the CPU board (A25450-000). The microprocessor control system supervises the power supply and
RF gain controls and processes operator input by enabling communication with a host computer over the IEEE-
488 interface or local control through the front panel display and buttons.
Communication of operational status with the amplifier is via fiberoptic links to the HPA interface assembly
(A25444-001). The HPA interface assembly provides fault monitoring capabilities for discrete fault logic and
analog readbacks. This assembly also contains the digital to analog circuits for controlling the solid-state pre-
amp’s (SSPA) gain adjustment.
2.2 DESCRIPTION OF THE RF SUBSYSTEM
The TWTA consists of two stages of RF amplification: a solid-state pre-amp (SSPA) assembly with adjustable
gain (E02792-100) and a traveling-wave tube amplifier (E02591-001).
The type N RF input connector is located on the rear panel. The RF input is fed to the input connector on the
solid-state pre-amp. The solid-state pre-amp's output drives the RF input of the TWT. The RF output of the
TWT is a WR-62 waveguide. The output is directed through a high-power coupler (E00467-100) which
provides forward and reverse sample ports before directing the RF output through the rear panel.
The reverse port on the directional coupler is connected to a crystal detector, whose output is used for VSWR
protection by the power supply logic board, for VSWR measurement in the leveling loop, and for reverse power
measurement on the HPA interface board.
The forward port output is split by a -10 dB coupler. The output is connected to a crystal detector via a pad.
The output of the crystal detector is used on the HPA interface board to measure forward power. The –10dB
port of the coupler is connected to the RF sample port on the rear panel.
Amplifier gain is determined by the solid-state pre-amp, which has a voltage-controlled attenuator. The CPU
board determines the output of a digital-to-analog converter (DAC) on the HPA interface board. This analog
reference is directed to the SSPA for the purpose of controlling the gain of the amplifier.
2.3 DESCRIPTION OF THE POWER SUPPLY SUBSYSTEM
The TWT power supply is of modular construction. All modules are connected through a motherboard, and are
very easy to replace. This makes maintenance fast and easy.
2.3.1 Low Voltage Power Supply Module:
AC/DC converter which generates the +15VDC/-15VDC/+5VDC needed for housekeeping.

Model 3000TP12G18
6 Rev A
2.3.2 Logic and Control Module:
This module controls the power supply, monitors all the voltages and currents of the unit, and provides
protection for the power supply and the TWT.
2.3.3 Power Factor Corrector Module
This switching module forces the line current waveform to follow the line voltage waveform. This minimizes
the line harmonics and maintains the power factor near unity. The output of this module provides the 375VDC
bus used by the high voltage switching power supply.
2.3.4 Power Board Assembly:
This module contains a 120kHz switching buck regulator, and a 60kHz H-Bridge, which converts the DC
regulated voltage to an AC signal. This regulated AC waveform is applied to the primary of the high voltage
transformer. Control is by the pulse width modulation board. The post regulator, which is a fast linear regulator
for the helix voltage, is also included in this module.
2.3.5 Diode/Cap Assembly
This module contains the high voltage transformer and the high voltage rectifiers.
2.3.6 High Voltage Filter
This module contains the high voltage capacitors for the cathode and the collector voltages. This module filters
ripple from the high voltage rectifiers, monitors the cathode and collector voltages, and sends a feedback signal
to the post regulator.
2.3.7 Heater Power Supply Module
Powers the TWT DC heater. It uses +15VDC input and provides isolated -6.3 VDC at cathode potential
2.3.8 Grid Modulator Module
The Grid module generates two floating voltages at cathode potential, and switches its output between those
voltages, at a rate of up to 100kHz. Bias and pulse top voltage for the TWT grid are provided by the Modulator
Assembly. Interconnects between the power supply modules are through a motherboard. It is installed in a
finned heat sink assembly to which the modules are bolted. The incoming cabinet air cools the heat sink.