DATA S H E E T
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
LD7261
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
ABSOLUTE RATINGS (Note 1, 2 and 3 )
ELECTRICAL
Heater Voltage ………………………………………
Heater Surge Current ……………………………
Heater Current ………………………………………
Heater Warm-up Time ……………………………
Helix Voltage ………………………………………
Helix Current ………………………………………
Anode Voltage ………………………………………
Anode Current ………………………………………
Collector Voltage ……………………………………
Collector Current ……………………………………
Cathode Current ……………………………………
RF Drive Power ……………………………………
RF Output Power …………………………………
Load VSWR …………………………………………
ENVIRONMENTAL
Temperature at output Flange ……………………
Air Flow ………………………………………………
Ambient Temperature
Storage ……………………………………………
Operation …………………………………………
Min.
–40
195
–40
–10
Max.
+110
–
+80
+50
Unit
˚C
kg/hour
˚C
˚C
Min.
6.0
–
–
300
9.5
–
8.0
–
4.0
–
–
–
–
–
Max.
6.6
2.5
1.8
–
10.8
15.0
10.25
0.5
5.8
350
350
25
400
1.2 : 1
Unit
V
A
A
s
kV
mA
kV
mA
kV
mA
mA
mW
W
–
2
LD7261
TYPICAL OPERATION (Note 2, 3, 4 and 5)
Unit
Frequency ……………………………………………
Output Power ………………………………………
Heater Voltage (Note 4) ……………………………
Heater Current ………………………………………
Helix Voltage ………………………………………
Helix Current ………………………………………
Anode Voltage ………………………………………
Anode Current ………………………………………
Collector Voltage ……………………………………
Collector Current ……………………………………
Cathode Current ……………………………………
Power Gain
Gain Variation
Gain Slope
at 25 W ………………………
at 250 W ………………………
at 25 W ………………………
at 25 W ………………………
at 25 W ………………………
at 250 W ………………………
3rd Order Intermodulation ………………………
(two equal carries, 25 W total)
20.0
250
6.3
1.42
10.6
0.7
8.6
0.01
5.0
264
265
49
46
5
0.012
1.5
6.0
–30
GHz
W
V
A
kV
mA
kV
mA
kV
mA
mA
dB
dB
dB
dB/MHz
deg./dB
deg./dB
dBc
AM-PM Conversion
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.
3
4
6-32 UNC-2B Threaded Holes
8 Pics.
23
165.1
±
1.5
127
Air Inlet
25.4
98.5
87
±
0.5
50.8
±
0.2
LD7261 OUTLINE
(Unit in mm)
19.8
±
0.5
11.4
76.2
±
0.5
152
±
0.5
505 MAX. (500 TYP.)
Cover Plate
174
±
1
25.24
24.28
Air Inlet Interface
179
±
2
M3-4 Holes
Air Output
with Slit
6
Lead Connections
Color
Brown
Yellow
Blue
Red
Black
White
76.2
6.4
5.6
31.8±0.5
RF Output
WR-51 Waveguide
6-32 UNC-2B Thru
4 Pics.
RF Input
SMA Female
y
t
r
e
w
q
900
±
50
99
±
1
83
±
0.5
10
12.62
(110)
33
83
±
0.5
87.5 MAX.
19
101
±
0.5
(75.5 TYP.)
55
±
2
12.14
33
108 MAX.
(For screw part)
101
±
0.5
101
±
0.5
157
±
0.5
8-32 UNC-2B Threaded Holes
10 Pics.
91
±
0.5
LD7261
Lead No.
1
2
3
4
5
6
Element
Heater
Heater-Cathode
Anode
Collector
Helix (GROUND)
Thermal Protection (Normal Close)
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