High-energy-physics - AM10/S-Band-1200W

Utilising the latest GaN power transistor technology, the AM10 series amplifier is designed for high efficiency pulsed power. With fast rise times & low pulse distortion the amplifier is ideally suited to applications in high-energy physics, typically as drivers for Klystron tubes. A control line is provided for remote operation, whilst RF samples of forward and reflected power are available for monitoring. Protection circuits are incorporated to ensure safety and long-term reliability.

Available in modular form for OEM system integration, with integral air-cooling, or as a fully stand-alone 19″ rack mountable instrument.

The amplifier is operated in a Gated mode, with the RF transistor bias controlled by a TTL command synchronised with the RF pulse. The transistors are in a biassed state only during the RF pulse, and otherwise in standby. This design provides the superior performance possible from a class AB design but without the disadvantages of high power consumption and heat generation, whilst the amplitude variation and phase excursions caused by transistor junction heating are reduced by the application of pre-pulse bias

Specifications for 19" Rack-Mount

• Centre Frequency : 2.85Ghz & 2.998GHz
• Peak Output Power : 1200W @ 5% duty
• Full Power Bandwidth: 40MHz min
• 3dB Power Bandwidth : 200Mhz typ
• Input Power for Rated Output : 0dBm nom
• Absolute max input Power : +15dBm (CW)
• Duty Cycle : 5% max
• Input Signal Characteristic : Pulsed
• Input Pulse Width : 200uS max
• Pulse Repetition Frequency : 5KHz max
• RF Output Stability in Pulse :0.2dB/10uS max, 0.8dB/200uS max @ peak O/P
• RF Output Phase Stability in Pulse : 1 degree max
• Harmonics: -40dBc max
• Non Harmonic Spurious Output : >80dBc
• Input Return Loss : 14dB min
• Output Return Loss : 18dB min
• Noise Figure : 6dB typ
• System Power Supply : Mains AC230V 1-phase
• Pulse control rise time (0-100% RF) : 5uS max
• Pulse control fall time (100-0% RF) : 5uS max
• RF Rise/Fall time : 100nS max
• TTL Pulse Control Signal : TTL HIGH = amplifier biassed to class AB
• TTL Enable Signal (remote control) : TTL HIGH = amplifier ACTIVE
• Dimensions (LWH) : 19" x 3U x 450mm. Rack or bench top style chassis
• Weight : 15Kg nominal
• Operating Temperature : 0 to 50C ambient
• Storage Temperature : -20 to 85C

Notes

1. Duty Cycle  The amplifier duty cycle is limited to 5% at which the amplifier may be continuously operated. The pulse width and repetition frequency of the RF signal may be varied as required within the stated limits, but must not exceed the maximum rated duty. Full performance is specified at the nominal duty conditions. Built-in protection against excessive duty cycle in incorporated, which will automatically limit the RF output if this level is exceeded.

2. RF output Variation in Pulse The above specifications apply when the amplifier is operated in saturation. Reduced RF output levels will result in correspondingly increased amplitude variation. It may be necessary to increase the TTL control to RF pulse delay to achieve optimum performance.

3. Power Consumption

The primary power input demand will be a function of the duty cycle. 110V and 230V versions are available – please specify when ordering.

4. Pulse Control Rise & Fall Time

This is the period of transition between standby & active states. During the standby state the amplifier is disabled drawing minimal power, and can not amplify an RF signal. In response to a TTL (high) command, the amplifier switches to an active state with full DC bias, and is able to amplify a pulse. The duration of this transition is the Pulse Control Rise Time. At the end of the pulse the amplifier may be reverted to the standby state. The duration of this transition is the Pulse Control Fall Time. Note that the application of RF signals during these transitions will result in a distorted output.

5. RF Rise & Fall Time

The RF rise/fall times are for a pulsed RF signal, with the amplifier stabilised in class A in response to TTL pulse-control signal.

6. TTL Pulse Control Signal

The TTL pulse control line is AC coupled to prevent accidental application of CW RF input signals.

7. Test Data Test data for operation under specific duty conditions (pulse width & frequency) can be provided on request. Otherwise, test data under maximum duty conditions is provided.

Signal Interfaces

• RF Input & Output:  N type female panel jack
• TTL Enable: BNC female panel jack
• TTL Pulse control: BNC female panel jack
• Signals: 15 way D-type

Mechanical

• Dimensions (LWH): 19” x 3U x 550mm. Rack or bench top style chassis
• Weight: 20Kg nominal

The front panel mountings should not be used to support the entire weight of the amplifier when mounted in a 19" rack. The side extrusions accept M5 captive nuts, which should be located at the rear of the unit to provide additional support. Alternatively, the amplifier should be rested on a tray within the rack.

Front Panel Controls & Indicators

• Main power keyswitch Initialises unit & activates cooling system.
• Amplifier Enable Switch Illuminated push switch turns RF amplifier module on.
• PSU status indicator Displays status of AC/DC convertors.
• RF status indicator Shows presence of RF at output port
• TTL status indicator Shows presence of TTL-high enable signal
• Reflected power indicator Shows reflected power in excess of 400W
• Over temperature indicator Shows amplifier shut-down due to over temp.
• Output Power Meter Digital LED meter reading peak forward output power in watts
• (Limited accuracy where prf <10Hz or PW <1uS)

Remote Status Interface

TTL RF On/Off, over temperature status, VSWR and PSU status reported to rear panel D-type connector.

• TTL RF On/Off Status: High = ON
• Over Temp Status: High = Alarm
• VSWR Status: High = Alarm
• PSU Status: High = OK

Analog voltage approx proportional to RF output level on rear panel D-type connector:

• Forward Power Detector Output: +5V nom @ Peak RF O/P
• Detector Dynamic Range: 15dB min

Protection Features

Output power limiter: Amplifier output is limited if average RF output power exceeds 5% duty.

Reverse Power Protection: Integral output isolator provides full power mismatch protection.

Over temperature protection: Monitors power module temperature, with automatic over temp shut-down (with front panel indication) and auto reset.

Safety interlock contacts: A two-state output is provided in the form of a pair of normally-closed dry relay contacts. The output is conductive (20 mA maximum current ) when the internal conditions required for normal operation of the amplifier have been satisfied. Failure of any condition, or the activation of a self-protective feature (excess reverse RF power or over-temperature) causes the contacts to be open. The contacts are available at the rear panel D-type connector.

Environmental

• Operating temperature range: 0 to 50C ambient
• Storage temperature range: -20 to 85C

The amplifier should be operated in a clean environment. Operation in sand/grit/dust environment may severely reduce the life of the internal cooling fans. The front (intake) and read (exhaust) of the amplifier should not be obstructed. On no account must the amplifier be subjected to water ingress. Operation An RF signal may be amplified only when a TTL command is applied at the pulse control connector.  Full details of the operating procedure are detailed in the operating manual supplied with the equipment.

Amplifying a Pulsed RF Signal

It is necessary to synchronise the RF pulse with the TTL pulse control signal. This is accomplished using two square wave pulse generators capable of the desired PRF, one as master the other as slave. The slave is configured to trigger a pulse from an RF source, the master to output the TTL pulse control signal to the amplifier and after the required delay (pulse control rise time), trigger the slave.

For SMR20 specifications & function refer to the operating manual or to online information at: http://www2.rohde-schwarz.com/file_3894/smr_20-40%20e03.pdf

Fig 1 - Using external pulse generators with an SMR20 Rohde & Schwarz source

NB. It is not necessary to program a delay between the end of the RF pulse and the TTL pulse control signal.

Fig 2. Typical pulse timing for 10uS RF pulse"

Deliverables Each amplifier is supplied packed in a purpose designed carton containing:

• Pair of keys for front panel keyswitch. These are uncoded and factory replaceable.
• Pair of front panel handles with fixing screws. These are removed for transit.
• Mains power cable 2m.
• Operating manual with test data.

Maintenance  

No maintenance is required in normal operation and there are no user-serviceable parts within the amplifier. Each amplifier is factory tested and supplied with a set of test results. If degradation in performance to below the specified levels occurs, or a failure is suspected, then the complete unit should be returned to the manufacturer together with details of the fault.

Safety  The amplifier is subject of safety tests at the factory is supplied compliant with the LV and EMC Directives and bears the CE marking. The amplifier is heavy and care should be taken when lifting. Carrying handles are provided at the front panel. Hazardous voltages are present within this line-operated unit. Do not remove any panels. The centre conductor of the RF output connector should not be touched whilst the unit is in operation. Up to 1200W RF power can be present which may cause skin burns. Connection to the RF output port must not be made or broken whilst operating at high power levels. This may result in damage to or destruction of the output connector. The amplifier MUST be grounded. Line supply is filtered within the amplifier. A slow-blow fuse is located in the mains inlet. Should this repeatedly fail the amplifier should be returned to the factory for investigation. Small objects and thin cables etc should be kept away from the rear panel cooling fans which are fitted with finger guards.

Warranty  Microwave Amplifiers Ltd warrants for two years from date of shipment that the goods supplied will be in fully compliance with the agreed specifications and will be free from defects in material and workmanship. Any and all other warranties (except of title) express or implied, relating to fitness for particular purpose, merchantable quality or otherwise are expressly disclaimed. Seller will not be responsible for special or consequential loss or damages. Liability shall be limited to the repair or replacement of defective products subject to the return of the product intact, and un-tampered with by the buyer.