Microwave Input/Output

Features Overview

  • Define the Center Frequency of the analysis band

  • Configure the frequency up/down-conversion of each Readout Channel

Description

For the Signal Output, the digital 1-GHz-wide analysis 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. Then, the analog signal (dark blue elements) is mixed 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 1-8 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 ADC range is faithfully mapped to the selected Output Range.

shfqa analog output
Figure 1. Analog Signal Output Stage

The Signal Input down-conversion chain (dark blue elements) works analogously, but in the backwards direction. The main differences to the Signal Output are the missing selectable filter and the conversion to 3 GHz instead of 2 GHz before the digitization through the 14-bit ADC. Because of the sampling rate of 2 GSa/s, the 3 GHz signal appears as a 1-GHz signal in the digital domain (light blue elements) before being down-converted to DC.

shfqa analog input
Figure 2. Analog Signal Input Stage

The advantages of this scheme, for example compared to IQ-mixer based frequency conversion, are that it is calibration-free, wide-band and robust. The optimal selection of the different gains, attenuations and filters in the frequency conversion chains are taken over by the SHFQA, such that only a few settings need to be set to control the Input and Output Signal band parameters of the SHFQA: Center Frequency, Input/Output Ranges, and Input/Output Enabled.

Functional Elements

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

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

Center Frequency

1-8 GHz, double

Sets the center frequency of the analysis band in Hz. The frequency is rounded to the nearest multiple of 100 MHz. It is common to both the Input and Output of the same readout channel.

Input On

On/Off

Enables the Signal Input.

Input Range

-45 dBm to +10 dBm

Sets the maximal input power Range that maps to the full scale of the ADC. The Ranges decrease in steps of 5 dBm from 10 dBm down to -45 dBm.

Output On

On/Off

Enables the Signal Output.

Output Range

-30 dBm to +10 dBm

Sets the maximal output power Range that maps from the full scale of the DAC. The Ranges decrease in steps of 5 dBm from 10 dBm down to -30 dBm.

In/Out Tab in the LabOne GUI

The Input and Output settings can also be accessed through the In/Out tab in out tab of the SHFQA’s LabOne general user interface. After clicking on the tab, an overview subtab opens that displays all settings for all available Readout Channels.

in out tab overview
Figure 3. The Overview In/Out Tab of the GUI

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

in out tab detail
Figure 4. A detailed In/Out Tab of the GUI