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Booster is an eight channel RF power amplifier, providing up to 5W of RF between 40MHz and 500MHz. Mounted in a compact 2U high 19'' chassis, it is optimised for low cost and low power consumption, while providing good RF performance. It provides full interlocking and logging via a flexible ethernet-based remote interface.

Booster is currently available commercially from two suppliers: TechnoSystem and Creotech.

Overview

The specification below is somewhat pessimistic, detailed characterisation data can be found spread among various issues. To do: sort data and post here!

• Bandwidth: 40MHz to 500MHz
• P1db: 36dBm min
• Max CW output power: 38dBm min
• Gain @1dB compression: 40dB ±1dB typ (±1.5dB max)
• IP3: 48dBm min
• Crosstalk: -80dB max
• Input/output VSWR: 1.5:1 max
• Power supply: 100VAC-240VAC, 50Hz-60Hz
• Total power efficiency: >35% at 1dB saturation from mains to RF

Features

• Text-based (SCPI-like) Ethernet interface for monitoring and configuration
• Protection circuit shuts down individual channels in case of: input power overload; output power overload; reverse power overload; channel failure. Protection tripped indicator LED for each channel on the front panel, also readable via Ethernet. Protection circuit may be reset either using push-button on front panel or via Ethernet. The output power overload threshold is user-adjustable on a per-channel basis using the Ethernet interface. This allows users to ensure that the maximum power rating of sensitive loads, such as AOMs cannot be exceeded accidentally.
• Per-channel remote monitoring of: forward and reverse power; temperature; current and voltage.
• Remote shut down of individual channels via Ethernet, for example to avoid power dissipation from unused channels.
• Each channel is an independent unit for easy field replacement

Interlocks

Signals involved in interlocks are as follows.

• input: RF power applied to input SMA (fixed calibration at 3 dBm)
• output: RF power sourced by output SMA (user adjustable up to 39 dBm)
• reflected: RF power applied to output SMA (fixed value at 26 dBm of reflected power)
• current: power amplifier currents for 30V and 6V supplies (hardware foldback circuit)
• temperature (thermal switch to disable at 80 degrees, software protection at 60 degrees)

Note that RF power detectors are sensitive >+10dBm.

Overview

Booster uses a series of interlocks to protect both itself and the loads it drives from fault conditions.

There are two classes of interlock, both acting on a per-channel basis: overloads, caused by excessive input or output forwards/reflected power; and device errors, caused by internal faults, such as excessive temperature. In addition to these per-channel interlocks, Booster has a thermal switch that cuts off power to the device if the chassis temperature exceeds 80C.

In case of either an overload or error condition, the input RF is disconnected from the amplifier using an internal RF switch and the amplifier power stage is shut down. Once an interlock has tripped, it must be manually cleared to resume normal operation, either by pressing the "interlock reset" button or via the remote programming interface.

The interlock status is displayed on the front panel LEDs as follows:

• All LEDs off - the channel has been disabled either via software or by pressing the standby button
• OK - the channel is enabled and operating normally
• OVERLOAD - one of the power interlocks has tripped
• ERROR - an error condition has been detected
• NB disabling a channel (via the remote interface or by pressing the standby button) does not clear the interlock status, despite the fact that the OVERLOAD and ERROR LEDs turn off as long as the channel remains in standby. Once the channel is re-enabled, the interlock LEDs switch on again.

When Booster is first powered on, all channels are enabled and all interlocks cleared.

Overloads

The input and output RF powers are interlocked using fast (ns) hardware interlocks. The output reverse power is interlocked in software on the microprocessor. The threshold for the output power interlock is user-adjustable via the remote programming interface to allow protection of sensitive loads, which cannot tolerate Booster's full output power. The input and reverse output power interlocks have fixed thresholds chosen to protect Booster from damage.

Front panel switches

Booster's front panel houses two push switches:

• INTERLOCK CLEAR: equivalent to the INTERLOCK:CLEAR ALL instruction
• STANDBY: toggles between enabling and disabling all channels, equivalent to the CHANNEL:ENABLE ALL and CHANNEL:DISABLE ALL instructions.