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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.

Overview

• 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
• Cost: €6000

Features

• Text-based (SCPI-like) Ethernet interface for monitoring and configuration
• Protection circuit shuts down individual channels in case of: input 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 input 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

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 or current consumption. 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.

Remote programming interface

Overview

Booster provides a SCPI-like remote programming interface over Ethernet using a TCP server on port 5000.

• All commands must be terminated with a new line (\n) character
• Booster responds to all commands. Commands containing a ? query Booster for information, other commands are acknowledged with the response OK. An error string is returned in case of a programming error, such as a malformed command
• Capital letters denote a part of the command that must be specified, lower case letters are optional. Commands are case insensitive. For example INTERLOCK:POWER 0 -5, int:pow 0 -5 and INT:POW 0 -5 are all equivalent
• Triangular brackets denote a named parameter, which should be substituted for a value when forming the command
• | denotes a choice between two different parameters

Commands

• *IDN? returns a device ID string containing hardware and firmware revision information
• DEVice:RESET reset all settings (including those stored in non-volatile memory) to factory defaults
• INTerlock:POWer <channel> <power> output forwards power interlock threshold in dBm e.g. 'INT:POW 0 33` sets the output forwards power interlock threshold for channel 0 to 33dBm. The threshold must lie between 0dBm and 38dBm otherwise an error is returned and the threshold is not adjusted. All updates to the interlock threshold are saved to non-volatile memory and retained across reboots of the device.
• INTerlock:POWer? <channel> returns the output forward power interlock threshold for a channel
• INTerlock:STATus? blank <all>|<channel> returns the interlock status for either a single channel or for all channels (and-ed together). Response is 1 if any interlock has tripped, otherwise 0.
• INTerlock:OVERload? blank <all>|<channel> returns the overload interlock status for either a single channel or for all channels (and-ed together). Response is 1 if there has been an overload, otherwise 0.
• INTerlock:ERRor? blank <all>|<channel> returns the device error interlock status for either a single channel or for all channels (and-ed together). Response is 1 if there has been an error, otherwise 0.
• INTerlock:CLEar blank <all>|<channel> resets the interlock for either a given channel or for all channels. Any channels that are enabled resume normal operation once the interlock has been cleared.
• MEASure:TEMperature? <channel> returns the temperature of a given channel in centigrade
• MEASure:FAN?returns the fan speed in percent
• MEASure:CURrent? <channel> returns the bias current for a given channel in amps
• MEASure:INPut? <channel> returns the input power for a given channel
• MEASure:OUTput? <channel> returns the output (forward) power for a given channel
• MEASure:REVerse? <channel> returns the output reverse power for a given channel
• CHANnel:ENAble blank <all>|<channel> enables either a single channel or all channels. e.g. CHAN:ENA 0 enables channel 1, CHAN:ENA enables all channels.
• CHANnel:DISABle blank <all>|<channel> disables either a single channel or all channels. e.g. CHAN:DISAB 0 disables channel 1, CHAN:DISAB disables all channels. Disabling a channel consists of first disconnecting the input RF power, before turning off the bias voltage and current for the power FET. Note that disabling a channel does not clear the interlock status for that channel; interlocks remain in force once the channel is re-enabled.
• CHAnnel:ENAble? ALL|<channel> returns the status (1 or 0) for of either a given channel or all channels (and-ed together)

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 1 and CHANNEL:ENABLE ALL 0 instructions.

USB Interface

Booster provides a USB-serial interface accessible on the from panel for diagnostics and firmware updates. The serial port operates at 115200k Baud (8n1).

Commands:

• start/stop - resume/suspend display of status messages along with interlock thread (use with caution)
• ifconfig - display network information (ip address, mac address)
• ifconfig dhcp - enables DHCP
• ifconfig [ip addr] [gw addr] [netmask] - configure static ip address
• Output power interlock calibration
  • 2-point calibration of the power detector used to detect excessive output power
  • Calibration is performed at 200MHz
  • Apply RF so that the output power is 20dBm and enter the command intcal <channel number> 1 20
  • Apply RF so that the output power is 36dBm and enter the command intcal <channel number> 2 36
  • Each calibration step will produce an output like Got 1-point cal val 40 pwr 20
• Bias current calibration
  • finds the power FET gate bias voltage required to give a specified bias current
  • the bias voltage is saved to/restored from EEPROM
  • calbias <ch number> <desired current> e.g. calbias 2 160 to set the bias current for channel 2 to 160mA
• reboot - reboots the device

Firmware update - Linux

• install dfu-util
• download the latest update.dfu from github
• connect the device to a PC via USB
• power the device and (e.g. using a paperclip) while pressing the small recessed button on Booster's front panel near the USB socket
• find the "alt" number of the device's internal flash by running dfu-util -l. An example output is shown below, with the internal flash at alt 0.

> dfu-util 0.9
> 
> Copyright 2005-2009 Weston Schmidt, Harald Welte and OpenMoko Inc.
> Copyright 2010-2016 Tormod Volden and Stefan Schmidt
> This program is Free Software and has ABSOLUTELY NO WARRANTY
> Please report bugs to http://sourceforge.net/p/dfu-util/tickets/
> 
> Found DFU: [0483:df11] ver=2200, devnum=29, cfg=1, intf=0, path="3-5", alt=3, name="@Device 
Feature/0xFFFF0000/01*004 e", serial="377533563436"  
> Found DFU: [0483:df11] ver=2200, devnum=29, cfg=1, intf=0, path="3-5", alt=2, name="@OTP Memory /0x1FFF7800/01*512 e,01*016 e", serial="377533563436"  
> Found DFU: [0483:df11] ver=2200, devnum=29, cfg=1, intf=0, path="3-5", alt=1, name="@Option Bytes  /0x1FFFC000/01*016 e", serial="377533563436"  
> Found DFU: [0483:df11] ver=2200, devnum=29, cfg=1, intf=0, path="3-5", alt=0, name="@Internal Flash /0x08000000/04*016Kg,01*064Kg,07*128Kg", serial="377533563436"

• update the firmware by running dfu-util -D update.dfu -a <alt>, <alt> replaced by the number above (e.g. dfu-util -D update.dfu -a 0)
• once the operation has completed, power cycle the device

Firmware Update - Windows

• download DfuSe Demo
• download the latest update.dfu from github
• connect the device to a PC via USB
• power the device and (e.g. using a paperclip) while pressing the small recessed button on Booster's front panel near the USB socket
• launch DfuSeDemo
• Select Internal Flash from the Select target(s) menu
• in Upgrade or Verify Action click Choose and select firmware update file
• click Yes in dialog box
• wait for operation to complete, then power cycle the device