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Sideband Control -

The DST501 consists of two DDS chips to provide the baseband in-phase and quadrature waveforms. DDS A is the left DDS on the board, while DDS B is the right DDS on the board. DDS A is the in-phase input into the modulator and DDS B is the quadrature input into the modulator. Both the DDS A and DDS B outputs go through a low-pass filter before entering into the modulator. The user will need to provide the carrier frequency, which can be provided to the board using the LO SMA connector. The carrier frequency needs to be between 4 and 7 GHz.

IQ Selection

Although the inputs into the modulator are fixed, either DDS chip can be selected as the in-phase or quadrature signal. DDS A (left DDS) is connected to the in-phase input of the modulator, while DDS B (right DDS) is connected to the quadrature input of the modulator. Depending on which DDS chip is selected as the in-phase signal and which is selected as the quadrature signal, the modulated output signal from the modulator can either have the lower sideband suppressed or the upper sideband suppressed.

If DDS A is selected as the in-phase signal and DDS B is selected as quadrature signal then the lower sideband will be suppressed. In other words, the output will only consist of the upper sideband (above the carrier frequency).

Conversely, if DDS A is selected as quadrature signal and DDS B is selected as in-phase signal then the upper sideband will be suppressed. In other words, the output will only consist of the lower sideband (below the carrier frequency).

If DDS A and DDS B have the same setting, both are in-phase signals or both are quadrature signals, then neither sideband will be suppressed and you will have a dual sideband output that is mirrored about the carrier frequency.

Listed below are the different combinations of DDS IQ selects and the resulting modulated output:

DDS A IQ Select	DDS B IQ Select	Output
In-Phase	In-Phase	Dual Sideband
In-Phase	Quadrature	Upper Sideband
Quadrature	In-Phase	Lower Sideband
Quadrature	Quadrature	Dual Sideband