Page 1
DATA SHEET
HIGH POWER TRAVELING WAVE TUBE
FOR COMMUNICATIONS
LD7261
20 GHz, 250 W CW, PPM FOCUSING, HIGH POWER GAIN
GENERAL DESCRIPTION
The NEC LD7261 is a PPM-focused traveling wave tube designed for use as final amplifier in the earth-to-
satellite communications transmitter.
This is capable of delivering an output power of 250 W over the range of 18.0 to 21.7 GHz and provides a
power gain of more than 40 dB at 250 W.
Furthermore, it is rugged and reliable design offers long-life service.
FEATURES
™ High Power Gain
The power gain is typically 40 dB at 250 W level.
™ Simple Cooling System
All the tubes are forced-air-cooled, so that the cooling systems are greatly simplified.
™ PPM Focusing
The tube is PPM (Periodic Permanent Magnet) -focused, eliminating entirely the focusing power supplies
and interlock circuits.
™ Rugged Construction
The tube is designed to be rugged, therefore it is suitable for transportable systems.
™ Long Life and High Stability
The tube employs an advanced impregnated cathode with a low operating temperature for long life.
™ Microdischarge Free
The tube is carefully designed to be free from microdischarge in the electron gun for long term operation,
therefore it is suitable for digital communication service.
For safe use of microwave tubes, refer to NEC document “Safety instructions to all personnel
handling electron tubes” (ET0048EJ∗V∗UM00)
The information in this document is subject to change without notice.
Document No. ET0397EJ1V0DS00
Date Published August 1998 M
Printed in Japan
©
1998
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GENERAL CHARACTERISTICS
ELECTRICAL
Frequency ……………………………………………… 18.0 to 21.7 GHz
Output Power ………………………………………… 250 W
Heater Voltage ………………………………………… 6.3 V
Heater Current ………………………………………… 1.42 A
Type of Cathode ……………………………………… Indirectly heated, Impregnated
Cathode Warm-up Time …………………………… 300 s
MECHANICAL
Dimensions …………………………………………… See Outline
Weight ………………………………………………… 6.0 kg approx.
Focusing ………………………………………………Periodic Permanent Magnet
Mounting Position …………………………………… Any
Electrical Connections ……………………………… Flying Leads
RF Connections
Input ………………………………………………… SMA Female
Output ……………………………………………… Mates with WR-51 waveguide (see outline)
Cooling ………………………………………………… Forced Air
LD7261
ABSOLUTE RATINGS (Note 1, 2 and 3 )
ELECTRICAL
Heater Voltage ……………………………………… 6.0 6.6 V
Heater Surge Current …………………………… – 2.5 A
Heater Current ……………………………………… – 1.8 A
Heater Warm-up Time …………………………… 300 – s
Helix Voltage ……………………………………… 9.5 10.8 kV
Helix Current ……………………………………… – 15.0 mA
Anode Voltage ……………………………………… 8.0 10.25 kV
Anode Current ……………………………………… – 0.5 mA
Collector Voltage …………………………………… 4.0 5.8 kV
Collector Current…………………………………… – 350 mA
Cathode Current …………………………………… – 350 mA
RF Drive Power …………………………………… – 25 mW
RF Output Power ………………………………… – 400 W
Load VSWR ………………………………………… – 1.2 : 1 –
ENVIRONMENTAL
Temperature at output Flange…………………… –40 +110 ˚C
Air Flow ……………………………………………… 195 – kg/hour
Ambient Temperature
Storage …………………………………………… –40 +80 ˚C
Operation ………………………………………… –10 +50 ˚C
Min. Max. Unit
Min. Max. Unit
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TYPICAL OPERATION (Note 2, 3, 4 and 5)
Frequency …………………………………………… 20.0 GHz
Output Power ……………………………………… 250 W
Heater Voltage (Note 4)…………………………… 6.3 V
Heater Current ……………………………………… 1.42 A
Helix Voltage ……………………………………… 10.6 kV
Helix Current ……………………………………… 0.7 mA
Anode Voltage ……………………………………… 8.6 kV
Anode Current ……………………………………… 0.01 mA
Collector Voltage …………………………………… 5.0 kV
Collector Current…………………………………… 264 mA
Cathode Current …………………………………… 265 mA
Power Gain at 25 W ……………………… 49 dB
at 250 W ……………………… 46 dB
Gain Variation at 25 W ……………………… 5 dB
Gain Slope at 25 W ……………………… 0.012 dB/MHz
AM-PM Conversion
at 25 W ……………………… 1.5 deg./dB
at 250 W ……………………… 6.0 deg./dB
3rd Order Intermodulation ……………………… –30 dBc
(two equal carries, 25 W total)
LD7261
Unit
Note 1 : Absolute rating should not be exceeded under continuous or transient conditions. A single absolute
rating may be the limitation and simultaneous operation at more than one absolute rating may not
be possible.
Note 2 : The tube body is at ground potential in operation.
Note 3 : All voltages are referred to the cathode potential except the heater voltage.
Note 4 : The optimum operating parameters are shown on a test performance sheet for each tube.
Note 5 : These characteristics and operating values may be changed as a result of additional information or
product improvement. NEC should be consulted before using this information for equipment
design. This data sheet should not be referred to a contractual specification.
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LD7261 OUTLINE (Unit in mm)
r
y
t
23
LD7261
w
q
e
10
900 ± 50
91 ± 0.5(110)
Air Inlet
RF Input
SMA Female
RF Output
WR-51 Waveguide
6-32 UNC-2B Thru
4 Pics.
157 ± 0.5101 ± 0.5
179 ± 2174 ± 1
24.28
12.14
25.24
505 MAX. (500 TYP.)
12.62
33
101 ± 0.5101 ± 0.519
33
6
98.5
87 ± 0.5
50.8 ± 0.2
6-32 UNC-2B Threaded Holes
8 Pics.
165.1 ± 1.5
127 25.4
76.2
4
5.6
19.8 ± 0.5
31.8±0.5
76.2 ± 0.5
11.4
Cover Plate
6.4
99 ± 1
152 ± 0.5
Air Inlet Interface
83 ± 0.5
M3-4 Holes
83 ± 0.5
55 ± 2
(75.5 TYP.)
87.5 MAX.
Air Output
with Slit
108 MAX.
(For screw part)
Red
Blue
Color
Brown
Yellow
8-32 UNC-2B Threaded Holes
10 Pics.
Black
Element
Heater
Heater-Cathode
Anode
Collector
Helix (GROUND)
12345
Lead No.
Lead Connections
White
Thermal Protection (Normal Close)
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LD7261
5
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LD7261
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written consent of NEC Corporation. NEC Corporation assumes no responsibility for any errors which may
appear in this document.
NEC Corporation does not assume any liability for infringement of patents, copyrights or other intellectual
property rights of third parties by or arising from use of a device described herein or any other liability arising
from use of such device. No license, either express, implied or otherwise, is granted under any patents,
copyrights or other intellectual property rights of NEC Corporation or others.
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to persons or property arising from a defect in an NEC electronic component, customers must incorporate
sufficient safety measures in its design, such as redundancy, fire-containment, and anti-failure features.
NEC devices are classified into the following three quality grades:
“Standard”, “Special”, and “Specific”. The Specific quality grade applies only to devices developed based
on a customer designated “quality assurance program” for a specific application. The recommended
applications of a device depend on its quality grade, as indicated below. Customers must check the quality
grade of each device before using it in a particular application.
Standard: Computers, office equipment, communications equipment, test and measurement equipment,
audio and visual equipment, home electronic appliances, machine tools, personal electronic equipment and
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systems, anti-crime systems, safety equipment and medical equipment (not specifically designed for life
support)
Specific: Aircrafts, aerospace equipment, submersible repeaters, nuclear reactor control systems, life support
systems or medical equipment for life support, etc.
The quality grade of NEC devices is "Standard" unless otherwise specified in NEC's Data Sheets or Data
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grade, they should contact an NEC sales representative in advance.
Anti-radioactive design is not implemented in this product.
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