3.7 WG Switches

This page configures the waveguide switches controlled by the IO-FEP2. The standard version provides I/O circuits for 4 switches, it can be upgraded to up to 16 switches. They can easily be enabled by entering the corresponding feature code. See chapter 2.4.1 Feature code activation .

The following properties may be configured for each waveguide switch:

• Type --- Defines actuation mode for the switch:

  • UNUSED --- The switch is not connected / not used. te .ns FIXED-PULSEThe switch is actuated with a pule of a fixed width. After the actuation pulse the position is checked and a fault is raised if the switch position is not signalled as expected.
  • AUTO-PULSE --- With AUTO-PULSE the IO-FEP2 releases the switch actuation as soon as the switch signals that it reached it's target position. The pulse width given for this switch in this mode acts as a maximum time / timeout: if the switch does not reach it's target position within this time, a fault is raised.
  • READ-ONLY --- The IO-FEP2 does not produce any actuation for a READ-ONLY switch, it simply displays name and position of this switch at the status page.
  • TOGGLE --- Use this configuration to control a waveguide- or coaxial switch with needs a toggle command. An actuation pulse of 'pulse width' milliseconds is applied to both actuation outputs, if a position is commanded which differs from the actual one.
  • SLAVE-TO-SWITCH-n --- Slave switches are automatically actuated when the configured master switch is set. Internally the switch uses it's individual actuation pulse timing, raises faults if the position indication inputs read unexpected states.

• Name --- When you activate switch at the 'Type' setting, the IO-FEP2 names this switch as 'Sxx'. You may name the switch in a more meaningful way by entering a circuit name at this place.

• Pulse Width --- The actuation pulse width (FIXED-PULSE) or the switch actuation timeout (AUTO-PULSE) in milliseconds.

• Inhibit --- Set a check mark at a particular column to activate the software controlled HPA muting for this switch and the selected output. Multiple HPA muting outputs may be selected to be activiated from a single switch. An output must be configured to 'SW-INHIBIT' mode before it can be selected at this place.

FIXED vs. AUTO pulse width

You will find the AUTO-PULSE mode very handy in most cases: The actuation pulse width is as short as possible, making 'queued' switching sequences running much faster. The AUTO-PULSE however requires that the switch signals it's target position not before the switch mechanics has reached a stable position where it does not 'snap back' if the actuation is switched off.

Additionally bouncing of the switch may be another problem in AUTO-PULSE mode. If a connected switch is prone to bouncing (you see this when the waveguide switch reached its position and nevertheless a fault is displayed) we recommend using FIXED-PULSE configuration.

You should therefore test each switch in AUTO-PULSE mode carefully if it operates reliably when controlled by the IO-FEP2 before you apply RF power to it.

READ-ONLY switches

The READ-ONLY mode is meant to be used for switches which have their actuation circuits wired in parallel to another switch, or do not provide any electrical actuation at all. The IO-FEP2 simply reads and displays the position decoded from the position indication inputs. However, the IO-FEP2 does no position fault checking with switches marked as READ-ONLY. This is because it neither knows the nominal position of such a switch nor when it gets switched and therefore may cause an 'indifferent position' state for a short moment.

SLAVE switches

SLAVE switches change their position any time the configured master switch is set. This is done by copying the switch position request from the master switch to all its slaves. Internally the slave switches are treated as individual switches, each switch controls its activation pulse timing and checks its position indicating inputs individually. Each slave uses its individual pulse width setting, it however inherits the AUTO/FIXED pulse mode from it's master.

As slave switches are commanded simultaneously with their master, but processed individually, they are subject to the IO-FEP2's switch action queuing. For details see the correspondent paragraph below.

Software controlled HPA muting

The IO-FEP2 provides software controlled HPA muting during switch actuations for situations where the waveguide switches do not provide inhibit circuits or where such circuits are not usable for some reason. To use this feature, you have to configure the IO-FEP2 as follows:

1. Select a number of PhotoMOS outputs to be used as software controlled HPA muting circuits. Open the IO-FEP2 and set the switches for these outputs to position 'Software controlled'.
2. At the Setup / Output Circuits configure these outputs as 'SW-INIHIBIT'. To make the output open to mute the HPA, set output polarity to 'INVERTED'.
3. At the Setup / WG Switches page configure the waveguide switches to activate the mute outputs in accordance to the RF signal flow.

The IO-FEP2 mutes the HPA(s) before the switch motor is actuated and unmutes it after the switch has reached it's target position. Multiple waveguide switches may activate the same muting output, the IO-FEP2 combines such requests with a logical 'or'. Each waveguide switch may activate multiple muting outputs.

When using the software controlled HPA muting, you should consider the following:

• Although the IO-FEP2 continuously monitors the position indication circuits of the switches and by this means recognizes manual switch actuations, you never should move such a switch manually. It may take up to 20 msecs until the IO-FEP2 mutes the HPA, with high RF power applied this may be enough to damage HPA and / or the switch.
• It is not possible to mix hardware and software controlled HPA muting internally in the IO-FEP2. If your system setup requires such a mix, you have to configure the software controlled inhibits and the hardware controlled ones separately, to different output circuits. You may combine these externally, e.g. by wiring the circuits in series.

Switch actuation queuing

The IO-FEP2 is capable to queue / delay waveguide switch actuations in order to protect weak power supplies from overload. This in particular is valuable if the IO-FEP2 is operated by monitoring & control computer, as a M&C is capable to command actuations for all waveguide switches at a time. The IO-FEP2 takes care that no more switch actuation outputs than configured are active at a time. Commanded switch actuation are delayed for this, switches commanded in parallel are processed in the order of their switch number.

The maximum number of the parallel switch actuation is configured at the General Setup page.