Ultra-Linear 50W Amplifiers 20-512MHz

AN-60-004
APPLICATION NOTE
LZY-1
ULTRA-LINEAR RF AMPLIFIER
20 MHz - 512 MHz
25 WATTS MIN., 1 dB COMPRESSION
(50 WATTS TYP., MAX. OUTPUT)
Reviewed by:
Jack Semizian
Radha Setty
INTERNET http://www.minicircuits.com
P.O. Box 350166, Brooklyn, New York 11235-0003 (718) 934-4500 Fax (718) 332-4661
Distribution Centers/NORTH AMERICA 800-654-7949 417-335-5935 Fax 417-335-5945 EUROPE 44-1252-835094 Fax 44-1252-837010
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TABLE OF CONTENTS
1.0
General Description ........................................................................................................................4
2.0
Electrical Performance Specifications .............................................................................................4
3.0
Mechanical Specifications ...............................................................................................................8
4.0
Electrical Features............................................................................................................................8
4.1
4.2
4.3
4.4
4.5
5.0
Mechanical Features ......................................................................................................................11
5.1
5.2
5.3
5.4
6.0
Overdrive Protection............................................................................................................8
Thermal Overload Protection.............................................................................................10
Reverse Polarity Protection................................................................................................10
Transient Protection ...........................................................................................................10
Shut-off Terminal...............................................................................................................10
Mechanical Outline............................................................................................................11
Heat Sink............................................................................................................................11
Cooling Fan........................................................................................................................11
Weight................................................................................................................................11
Suggested Applications..................................................................................................................11
6.1
6.2
6.3
6.4
6.5
6.6
6.7
AM Amplification..............................................................................................................11
FM Amplification ..............................................................................................................12
Linear Pulse Amplification ...............................................................................................12
Multi-Carrier Amplification .............................................................................................12
Television Carrier Amplification .....................................................................................12
Broadband 20 MHz - 512 MHz Swept Signal ...................................................................12
Feedforward Amplification................................................................................................12
7.0
Alternative Heat Sinking/Cooling..................................................................................................12
8.0
Quality Assurance Provisions ........................................................................................................13
8.1
8.2
9.0
Acceptance Test Procedure...............................................................................................13
8.1.1 Acceptance Test Procedure Test Setup................................................................. 13
8.1.2 Test Equipment List...............................................................................................13
Warranty ...........................................................................................................................14
References......................................................................................................................................14
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LIST OF ILLUSTRATIONS
Figure 1:
Small Signal Response @ -22 dBm Pin ...............................................................................6
Figure 2:
Large Signal Response @ 0 dBm Pin .................................................................................6
Figure 3:
Acceptance Test Procedure Test Setup................................................................................7
Figure 4:
Mechanical Outline Drawing ..............................................................................................9
LIST OF TABLES
Table 1:
Electrical Performance Specifications .................................................................................5
Table 2:
List of Test Equipment.......................................................................................................14
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LZY-1
1.0
GENERAL DESCRIPTION
The LZY-1 is a low cost, rugged, versatile, 43 dB Typ. gain, broadband, Class A Linear RF
Power Amplifier Module designed to operate linearly over the 20 MHz to 512 MHz frequency
band. The LZY-1 features low compression and low harmonic distortion at 25 watts, which
make it ideally suited to a wide variety of applications.
The conservative electrical and thermal design and careful attention to semiconductor ratings
insures continued years of service in both the laboratory and many commercial and semi-hostile
military environments.
The workmanship, quality, and attention to protective features along with selection of
components to COTS (commercial off-the-shelf) guidelines, further enhance applicability and
long MTTF.
The unit electrical performance is specified at +26 VDC but will operate without damage over
the +22 VDC to +30 VDC range.
The LZY-1 is supplied with its own high thermal efficiency heat sink and ball bearing cooling
fan for immediate use and reliable operation.
For applications where the heat sink / fan assembly presents a difficult physical fit, the RF linear
amplifier module may be removed and operated safely with alternative heat sink / cooling
methods if the guidelines in paragraph 7.0 are followed. Operation of the amplifier module
without proper heat sinking is not recommended and violates the warranty.
Protective features such as Input Overdrive, Reverse Polarity, Transient Protection and Thermal
Overload with automatic reset are included. A separate shut-off terminal is provided for remote
amplifier on/off control.
The LZY-1 was designed to satisfy a range of broad, and narrow-band multitone or single
frequency applications for original equipment, production test and laboratory equipment uses.
2.0
ELECTRICAL PERFORMANCE SPECIFICATIONS
The Electrical Performance Specifications and limits are listed in Table 1.
Typical broadband small and large signal gain and return loss responses are shown in Figures 1
and 2.
Comparison of the curves and gain data at the measurement points illustrates the dynamic
linearity of the LZY-1 across the frequency range.
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Figure a: Small Signal Response @ -22 dBm PIN
Figure 2: Large Signal Response @ 0 dBm PIN
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Figure 3: Acceptance Test Procedure Test Setup
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3.0
MECHANICAL SPECIFICATIONS
The mechanical outline drawing, mechanical specifications and heat sink mounting
details are shown in Figure 4.
4.0
ELECTRICAL FEATURES
4.1 OVERDRIVE PROTECTION
The LZY-1 is designed to operate with input drive levels up to +10 dBm without
damage at any frequency in the 20 MHz to 512 MHz range.
The unit contains a factory set control for automatic power output foldback to
protect internal components from RF input overdrive damage.
Foldback action takes place when the input drive level causes the output power to
exceed a threshold. This threshold can vary from 55 watts to 125 watts depending
on the input signal frequency. No damage will occur to the amplifier under any of
these output power levels.
At threshold, the output power begins to drop. As input drive level is increased,
the output power turns down to a low level, safeguarding the amplifier
components.
At input drive levels below the threshold, the overdrive protection circuit is
inactive and does not affect amplifier performance. The unit will perform within
the limits of the specifications of Table 1.
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Figure 4 – Mechanical Outline Drawing
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4.2
THERMAL OVERLOAD PROTECTION
The LZY-1 has an automatic built-in thermal shutoff feature. When mounted on the heat
sink / fan assembly supplied with the unit, the LZY-1 is a thermally efficient system that
meets the performance parameters in Table 1 in ambient environments from 0°C to
+50°C.
The amplifier is factory mounted on the heat sink using a thin film of thermal grease
between the RF module and the heat sink mounting surface. (See paragraph 7.0 for
operation without the factory supplied heat sink.)
With the fan operational at +26 VDC, the cooling air velocity is approximately 110 CFM.
The combination of heat sink design and cooling air velocity results in a very efficient
thermal resistance (0.08°C/watt) between the mating surfaces. Under these conditions,
the amplifier temperature is held to less than 15°C above ambient temperature at 20 watts
POut.
When the temperature of the LZY-1 exceeds +65°C due to any combination of ambient
temperature and / or overdrive, a thermal switch will actuate and shut off the amplifier by
shutting off bias to all stages. As the amplifier case cools down below 40°C, the thermal
switch will reset and restore the amplifier to normal operation.
4.3
REVERSE POLARITY PROTECTION
The LZY-1 is protected against damage from improper connection of the supply voltage
by incorporating a diode in series with the positive VDC terminal.
4.4
TRANSIENT PROTECTION
The LZY-1 is protected from damage by DC line transients and accidental shorting at the
VDC terminals by a zener protection circuit. This protection circuit is connected to the
transistor bias regulator supply and limits (clamps) those transients that would normally
pass through the regulator and damage the transistors.
4.5
SHUT-OFF TERMINAL
The LZY-1 has a separate EMI-Filtered shutoff terminal and a corresponding ground
terminal for use with an external remote shutoff circuit.
The nominal RF power output of 25 watts is reduced by 50 dB minimum within 20
milliseconds when the shut off terminal is grounded.
When the shutoff terminal is open-circuited, the RF output is restored within 40
milliseconds.
The voltage present at the shutoff terminal (open circuited) is approximately 11 volts.
When grounded, the series current is less than 11 mA.
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5.0
MECHANICAL FEATURES
5.1 OUTLINE
The outline drawing and dimensional detail are shown in Figure 4.
5.2 HEAT SINK
The LZY-1 heat sink is a high thermal efficiency heat sink that, when used with the 4
inch 110 CFM fan, results in a thermal resistance of 0.08°C/Watt. This number is
derived by dividing the case temperature increase of 15°C by the max DC Power of 190
watts (26 volts at 7.3A). (See paragraph 4.2 for other thermal considerations).
5.3 COOLING FAN
The cooling fan is a long life, brushless DC operated 4 inch ball bearing •muffin• fan
which delivers 110 CFM air at +26 VDC. The fan is mounted to an optimally designed
plenum on the heat sink for minimum air turbulence. The fan is protected by a fan guard.
The DC requirement of the fan, as installed, is 300 mA typical, 400 mA max at +26
VDC.
The fan meets EMI standards per FCC Part 15, Subpart J.
5.4 WEIGHT
The LZY-1 amplifier alone weighs less than 1.14 kg. Total weight with heat sink / fan is
under 4.0 kg.
6.0
SUGGESTED APPLICATIONS
The following performance characteristics are those generally expected from the LZY-1
under the conditions stated for each application. The versatility of the LZY-1 ultra-linear
amplifier is denoted in each of these applications for AM, FM, Pulse, Multi-Carrier and other
signal formats and modulation schemes common to the communications bands which form
part of the 20 MHz to 512 MHz frequency spectrum.
The suggested performance is provided to the user as a guideline which makes the LZY-1
ideal for a variety of driver or output amplifiers in many equipments. Specific results may
vary under different conditions.
6.1 AM AMPLIFICATION
The LZY-1 can be used to amplify an AM (Amplitude Modulated) carrier to a level of 5
watts (20 watts PEP) with less than 5% AM distortion when modulated at 90%.
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6.2 FM AMPLIFICATION
The LZY-1 will typically produce a minimum of 32 watts CW or higher and is limited
only by the overdrive threshold limits set by the input signal frequency as described in
paragraph 4.1.
6.3 LINEAR PULSE AMPLIFICATION
The LZY-1 is ideal for linear pulse or pulse train amplification to faithfully reproduce a
pulse signature to the 20 to 30 watt peak power level. The pulse width and duty cycle is
not limited at these power levels because of the Class A amplifier operation.
6.4 MULTI-CARRIER AMPLIFICATION
The LZY-1 when tested with two 5 watt tones (10 watts average) spaced 100 kHz apart at
400 MHz will display an IP3 minimum of +52 dBm. IMD under these conditions are
typically -30 dBc or better.
Other carrier spacing, power levels and number of carriers may change the IMD
performance.
6.5 TELEVISION CARRIER AMPLIFICATION
The LZY-1 can reproduce video, sound and color burst carriers on a composite TV signal
with minimal sync clipping for levels up to 5 watts average.
6.6 BROADBAND 20 MHZ TO 512 MHZ SWEPT SIGNAL
For swept linear applications at 20 watts, the LZY-1 will accept a constant input and
produce an output level within ±1.5 dB.
6.7 FEEDFORWARD AMPLIFICATION
The LZY-1 can be used as a main amplifier or error amplifier in a VHF or UHF
feedforward application due to its low IMD and relatively flat phase, delay, and
amplitude characteristics.
7.0
ALTERNATIVE HEAT SINKING / COOLING
The LZY-1 RF Linear Amplifier electrical specifications in Table 1 are guaranteed when
the RF Linear Amplifier module is operated on the factory supplied heat sink and the
cooling fan is running.
Physical limitation of certain equipment configurations may require the user to provide
alternative methods of heat sinking/cooling.
In these cases, the user can remove the RF Linear Amplifier module from the factory
supplied heat sink by disconnecting the wires between the cooling fan and the module
then removing the four mounting screws holding the module to the heat sink.
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The user must then provide an alternative heat sinking/ heat removal method that
provides an equivalent thermal resistance of 0.08°C/Watt to realize the unit electrical
performance specified in Table 1. (See Paragraph 4.2 for thermal considerations).
Depending on the approach to cooling, alternative methods may increase or decrease the
thermal resistance of that interface resulting in operation of the amplifier at a lower or
higher temperature rise above ambient.
A qualified Engineer or Technician should be responsible to design and evaluate the
alternative Heat Sinking method.
Failure to provide the proper heat sinking will result in module overheating which in turn
will activate the automatic thermal shut down circuit when the module temperature
exceeds +65°C.
8.0
QUALITY ASSURANCE PROVISIONS
8.1 ACCEPTANCE TEST PROCEDURE
All LZY-1 amplifier assemblies are subjected to 100% factory RF testing in accordance
with a written Acceptance Test Procedure in which RF performance parameters and
electrical features are tested and verified. Certificates of compliance are available.
RF performance data is recorded and inspected for conformance within the limits set
forth in Table 1.
Currently, each unit is subjected to a DC burn-in test for 72 hours with the input and
output ports terminated in 50 ohms. This is a worst case condition for the amplifier since,
when terminated, the DC power dissipated in the amplifier circuitry exceeds the amount
dissipated when RF power is being generated.
Performance is compared before and after the DC burn-in.
DC burn-in testing will continue at our discretion until sufficient history is generated to
reduce or eliminate this test.
8.1.1
Acceptance Test Procedure Test Setup
Figure 3 illustrates the test position set up used to perform acceptance testing on
the LZY-1 for the majority of the performance parameters specified in Table 1.
8.1.2
Test Equipment
The test equipment required to perform the acceptance tests is detailed in Table 2.
In the event any item of test equipment is unavailable, substitution of equivalent
equipment is suggested. All test equipment should be turned on 30 minutes prior
to start of test.
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DESCRIPTION
MANUFACTURER
MODEL
HP
428B
Digital Multimeter
Fluke
8050A
Digital Thermometer
Omega
650
20 dB Attenuator
Sierra
662A-20
Spectrum Analyzer
Anritsu
MS2601A
Network Analyzer
HP
8753C
Power Meter
HP
435B
Power Meter Sensor
HP
8482H
Ammeter
Power Supply 28V 10 Amps
Plotter
Various
HP
7470A
Terminations, 50 Ohm, 1/2 Watt
Various
SMA-Male
Switch (A/B)
Various
Lab Amplifier
Mini-Circuits
Attenuator 10 dB/20 dB (2W)
Various
Power Supply (0-30V; 3A)
Various
Switch, Knife, High Current
Various
MAV-11
Table 2: Acceptance Test Setup Equipment
8.2
WARRANTY
All LZY-1 amplifiers are warranted to be free from defects in material and workmanship
for a period of one year from date of shipment. This warranty does not cover the
conditions of physical abuse or operation beyond the specification limits delineated in
Table 1.
Operation of the RF module without the Heat Sink / Fan assembly supplied or without
the cooling fan operative violates the warranty and will result in thermal shutdown when
the module temperature exceeds +65°C.
9.0
REFERENCES
LZY-1 specification sheet, Rev A, ED-4276, 02/01/96
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