Output Tab

Features Overview

  • Enable/disable output

  • Define the Center Frequency of the modulation band

  • Define the output power range

Description

For the Signal Output, the digital 1-GHz-wide modulation band centered around DC is first interpolated by a factor of 3, then digitally up-converted to 2 GHz (light blue elements) before it is passed to the 14-bit DAC. The resulting 2 GHz analog signal (dark blue elements) is then converted to 12 GHz by means of a local oscillator at 10 GHz. To remove all unwanted spurious signals, the signal is strongly filtered before it is down-converted in a second mixing process with a variable local oscillator. Depending on its software-controllable frequency value, the final output frequency band has a center frequency between 0.6-8 GHz and a width of ±0.5 GHz. Several amplifiers, attenuators, and filters in the up-conversion chain ensure that the different elements are not saturated and that the DAC range is faithfully mapped to the selected Output Range.

shfsg analog output
Figure 1. Analog Signal Output Stage

The advantages of this up-conversion scheme compared to IQ-mixer-based frequency conversion are that it is calibration-free, wide-band, and stable, in addition to having superior spurious tone performance. The optimal selection of the different gains, attenuators, and filters in the frequency conversion chains are taken over by the SHFSG, such that only a few settings need to be set in the Output band parameters of the SHFSG: Center Frequency, Output Range, and Output On.

Functional Elements

The following Table 1 summarizes all settings. The modes are all accessible through the first level of the SGChannels branch: /DEV…​./SGCHANNELS/n/…​

Table 1. Output Settings
Control/Tool Option/Range Description

Center Frequency

0.6-8 GHz, double

Sets the center frequency of the analysis band in Hz. The frequency is rounded to the nearest multiple of 100 MHz. In the 8-channel variant of the SHFSG, this setting is shared between channels 1 and 2, etc.

Output On

On/Off

Enables the Signal Output.

Output Range

RF mode: -30 dBm to +10 dBm

LF mode: -30 dBm to +5 dBm

Sets the maximal output power Range that maps from the full scale of the DAC. The Range decreases in steps of 5 dBm from 10 dBm down to -30 dBm for the RF path, and from 5 dBm down to -30 dBm for the LF path.

Output Tab in the LabOne GUI

The Output settings can also be accessed through the Output tab output icon of the SHFSG’s LabOne general user interface. After clicking on the tab, an overview subtab opens that displays all settings for all available Output Channels.

output tab overview
Figure 2. The Overview Output Tab of the GUI

With the selectors at the left side of the Output tab, the detailed view of the up-conversion chain for the different Output Channels can be displayed. Each detailed view shows the available settings in the first, leftmost panel. In the second panel, a graphical representation of the currently selected parameters of the up-conversion chain is displayed.

output tab detail
Figure 3. A detailed Output Tab of the GUI