Inputs/Outputs Tab

The In / Out tab provides access to the settings of the Instrument’s main Signal Inputs and Signal Outputs. It is available on all SHFQA Instruments.

Features

  • Signal input configuration

  • Signal output configuration

Description

The In / Out tab gives access to the physical configuration of the signal inputs and outputs of the Instrument. The settings are listed in Table 2.

Table 1. App icon and short description
Control/Tool Option/Range Description

In/Out

btn mnu inout um

Gives access to all controls relevant for the Signal Inputs and Signal Outputs of each channel.

The In / Out tab contains 1 sub-tab for configurations of all channels, and 2 (SHFQA2) or 4 (SHFQA4) sub-tabs for configuration of each channel, as well as the block diagram (see in Figure 1 and Figure 2).

It is highly recommended to enable all required inputs and outputs and wait for 2 hours after powering on the instrument.

Please do not change the center frequency or input range while acquiring data. Mishandling of this could lead to an invalid scaling of the result vector.

in out tab overview
Figure 1. The overview In/Out tab.
in out tab detail
Figure 2. The overview of Channel 1 on In/Out tab.

Double Superheterodyne Frequency Up/Down-Conversion

The SHFQA uses double superheterodyne frequency conversion to convert its digital 1-GHz-wide analysis band in an analog stage from baseband frequencies to microwave frequencies up to 8.5 GHz. Each readout channel has its own frequency up/down-conversion chain and its own synthesizer to generate microwave frequencies.

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 3. 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 4. 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.

Frequency Representation

The frequency \(f_{\mathrm{out}}\) of the output signal on each channel can be calculated as

\[\begin{equation}\tag{1} f_{\mathrm{out}} = f_0 + f_{\mathrm{offset}}, \end{equation}\]

where \(f_0\) is the center frequency (Center Freq (Hz)), \(f_{\mathrm{offset}}\) is the offset frequency (Offset Freq (Hz)) set by either a Digital Oscillator, or an uploaded waveform (see in Quantum Analyzer Setup Tab). The range of \(f_0\) is listed in Table 2. The range of \(f_{\mathrm{offset}}\) is from -1 GHz to 1 GHz. Please note that signals with an absolute offset frequency greater than 500 MHz will be attenuated significantly.

The frequency \(f_{\mathrm{in}}\) of the input signal on each channel can be calculated as

\[\begin{equation}\tag{2} f_{\mathrm{in}} = f_0 + f_{\mathrm{IF}}, \end{equation}\]

where \(f_{\mathrm{IF}}\) is the intermediate frequency (IF) after frequency down-conversion. The down-converted signal can be monitored by the SHFQA Scope. In resonator spectroscopy experiments, the signal with \(f_{\mathrm{IF}}\) is integrated by the same Digital Oscillator. In qubit readout experiments, it is integrated by an uploaded waveform.

Power Representation

The power \(P_{\mathrm{out}}\) of the output signal on each channel is calculated as

\[\begin{equation}\tag{3} P_{\mathrm{out}} = \begin{cases} P_{\mathrm{range,\ out}} + 20\log_{10}(g_{\mathrm{osc}}), & \text{Spectroscopy mode, Continuous}\\ P_{\mathrm{range,\ out}} + 20\log_{10}(g_{\mathrm{osc}}A), & \text{Spectroscopy mode, Pulse}\\ P_{\mathrm{range,\ out}} + 20\log_{10}(A), & \text{Readout mode} \end{cases} \end{equation}\]

where \(P_{\mathrm{range,\ out}}\) is the output power range in units of dBm, \(g_{\mathrm{osc}}\) (\(g_{\mathrm{osc}} \le 1\)) is the amplitude gain of the Digital Oscillator, \(A\) (\(k\le1\)) is the amplitude of an uploaded waveform. Please note that the 14-bit vertical resolution of the output signal counts both waveform amplitude and oscillator amplitude gain in Spectroscopy mode. To have full 14-bit vertical resolution on the uploaded waveform, the amplitude gain of the oscillator has to be 1.

The input signal can be monitored by the SHFQA Scope. The power \(P_{\mathrm{in}}\) of the input signal on each channel can be calculated as

\[\begin{equation}\tag{4} P_{\mathrm{in}} = 10\log_{10}\frac{A^2_{\mathrm{IF,\ I}} + A^2_{\mathrm{IF,\ Q}}}{50}+30, \end{equation}\]

where \(A_{\mathrm{IF,\ I}}\) (\(A_{\mathrm{IF,\ Q}}\)) is the amplitude of IF I (Q) components displayed on the SHFQA Scope in units of RMS voltage (Vrms). The \(P_{\mathrm{in}}\) is calculated in units of dBm.

Functional Elements

The following Table 2 summarizes all settings. The modes are all accessible through the SHFQA nodes in Device Node Tree.

Table 2. Input and Output Settings
Control/Tool Option/Range Description

Center Frequency

1-8 GHz

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

-50 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 dB from +10 dBm down to -50 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 dB from 10 dBm down to -30 dBm.

Input Overload status

grey/yellow/red

Red: present overload condition on the signal input also shown by the red front panel LED. Yellow: indicates an overload occurred in the past.

Output Overload status

grey/yellow/red

Red: present overload condition on the signal output before DAC. Yellow: indicates an overload occurred in the past.