9.643 Spectrum-QAccess

This page describes the device driver and the device window for the Spectrum-QAccess logical device. This device monitors a number of parameters at a receiving device (e.g. IRD, Modem or IRD-Chain) and on demand sets the parameters on a spectrum analyzer to view the received signal.

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 .

• --- This page only presents the "TAKE" button which sets the spectrum analyzer to the appropriate settings
• --- The device info page.
• --- The maintenance page. The configuration parameters described below are set at this page.

Configuration parameters

At the maintenance page of the device window there are a couple of configuration parameters which must be set to integrate the device into the VLC/M&C.

Spectrum analyzer input switch settings

The Spectrum-QAccess device controls an N:1 switch in front of the spectrum analyzer. There are two configurations which the device can handle:

1. The receiver uses an input signal selector or is connected to the **antenna(s) through a switch matrix.**In this case enter the parameter ID of the receiver's input selector position at the "inputSelectionId" configuration parameter. If the receiver's input selections do not match the spectrum analyzer's input switch positions, list all possible receiver input selections in the "translateIn" configuration parameter, the corresponding spectrum analyzer input switch settings in the "translateOut" configuration parameter.When the device receives a "take" command, it reads the actual receiver input selection, translates it through the translateIn/translateOut lists and finally sets the spectrum analyzer input switch to the evaluated position.If receiver and spectrum analyzer are connected to the same switch matrix, the input selections for both devices are identical. In this case you can leave the translateIn/translateOut lists empty, the device will pass through the switch position without change.
2. The receiver is connected directly to the antenna port / signal **distributor without a switch.**There is no receiver input selection to monitor, hence leave the "inputSelectionId", "translateIn" and "translateOut" parameters empty. Instead, enter the spectrum analyzer input switch position to set for this receiver in the "inputDefault" field.Please note, that if the device was configured to listen to a receiver input switch before, you need to restart the M&C software in order make the change effective.

Frequency span calculation

The device monitors the symbol rate setting of the receiver to evaluate the frequency span which is set at the spectrum analyzer. The span is calculated following the equation:

frequency-span = symbol-rate / dataRateRatio

When setting the dataRateRatio, you should take notice of the unit multipliers of the parameters involved:

The spectrum analyzer accepts the frequency span setting in MHz. DVB receivers usually show the symbol rate setting in Msym/sec, hence a dataRateRatio value of 0.5 will give reasonable results.

Data modems however provide the symbol rate setting in symbols / second. In this case the dataRateRatio value should be set to e.g. 500000 in order to scale the result to MHz.

Center frequency setting

The Spectrum-QAccess device copies the monitored receive frequency without change to the spectrum analyzer's center frequency setting. This generally works fine as the sat-nms software always displays these frequency values as MHz.

Care should be taken to apply the correct LO frequency to the spectrum analyzer input. The CSM-Spectrum-Analyzer provides a flexible method to derive the LO frequency from the input switch position.

Variables defined by this device driver