1.166 Delay-Line

The Delay-Line logical device watches an arbitrary input parameter (may be a read-write or a read-only parameter) and passes this value through a delay line of configurable length. The output value of the device represents the value the input parameter had at 'delay' seconds before.

The delay line is build as a shift register with n stages, where n is the number of seconds set as the delay time. Every second the actual input value is put into the shift register, the oldest value from the register is dropped out to the output value of the device.

The one second clock for the shift register is derived from the cycle time of the device thread, hence the device must be configured in its own 'interface' (device thread) with 1000 milliseconds idle time.

The Delay-Line works with arbitrary parameter types, the 'input' and 'output' variables of the device change their type and range definition to that of the watched input parameter. When using numeric values, an offset may be added to the output value.

Using the Delay-Line with a N:1 protection switch

A N:1 protection switch usually mirrors the output power of the faulty chain to the spare one during switchover. With power amplifiers which regulate the output power by themselves, the (too low) output power itself may be the reason for the switchover. In such a case it makes no sense to mirror the power to the spare amplifier because this will also fail due to the wrong value.

Using the Delay-Line device can overcome this problem: For each operational transmit chain a Delay-Line device is configured which watches the output power of the HPA in this chain. The offset value of each Delay-Line may be set to compensate for the signal path attenuation difference between operational and spare HPA. The output of each Delay-Line device contains the output power of the chain which was present e.g. 10 seconds ago. Together with the offset value this is exactly the power which must be set at the spare HPA in case of a switchover.

For the redundant chain, a Delay-Line-Mirror device gets configured to set the mirrored output power at the spare HPA. The Protection-Switch-N-To-1 device is set to mirror the Delay-Line / Delay-Line-Mirror devices as an Level device of the transmit chains.

Device window pages

The following table shows which device window pages are available with this individual device type. Tool-bar functions not mentioned here are described at the general description of device windows .

• --- Shows the actual input output values of the device, permits to set the 'delay' and 'offset' values.
• --- The device info page.
• --- The maintenance page. The configuration parameters from this page are described below.

Configuration parameters

At the maintenance page of the device window there are a couple of configuration parameters which must be set to interconnect the Delay-Line device with the device that delivers the input signal.

Remarks

• Changing the delay time resets the shift register. The output will read the input value which was valid at the time when the delay time was changed for the next 'delay' seconds. Then it reflects the changes recorded for the input value after this moment.
• Changing the 'inputId' configuration parameter resets the shift register as well and also changes the data type definition of the 'input' and 'output' parameters. The 'offset' parameter is only enabled, if the data type of the watched parameter is INTEGER or FLOAT. After changing the 'inputId' configuration parameter, the device window of the Delay-Line should be closed and opened again to make the window adopt all changes.

Variables defined by this device driver