The Digital Signal Transceiver Driver firmware features digital signal processing (DSP), which allows you to change I/Q signal properties to generate or acquire more consolidated data and make testing easier. You can apply the DSP parameters independently to each channel, to the I or the Q value, or to the generation or acquisition loops.

DSP features include:

  • Digital Gain—Scales the amplitude of the streaming I and Q signals independently. Use this function to control the maximum power of the signal transmitted to the device or to reduce the power to avoid clipping when measuring the signal.

    data out.I = Quantization (data in.I * GI)

    data out.Q = Quantization (data in.Q * GQ)

    Where:

    • GI is 10**(IGaindB/20) applied to the I signal
    • GQ is 10**(QGaindB/20) applied to the Q signal

    The GI and GQ parameters change the gains of the I and Q, respectively.

  • Digital Offset—Shifts the bias signal of the streaming I/Q signal. Use this function to remove bias or offset voltages from I(t) and Q(t) signals.

    data out.I = Quantization (data in.I + CI)

    data out.Q = Quantization (data in.Q + CQ)

    Where CI and CQ are the offset value applied to the I and Q signal at the same time, respectively.

    This value allows you to change the I and Q offsets.

  • Digital Frequency Shift—Moves the center frequency and phase of the streaming signal. It is implemented by applying a numerically controlled oscillator (NCO) that creates a cosine/sine pair, which is then multiplied by the I/Q data using a complex multiplier. The net effect shifts the complex spectrum to the left or right in the frequency domain.

    data out.I = data in.I * cosine (2*pi*DeltaF) - data in.Q * sine (2*pi*DeltaF)

    data out.Q = data in.I * sine (2*pi*DeltaF)+ data in.Q * cosine (2*pi*DeltaF)

    Where DeltaF is the frequency shift applied to the signal and has the ratio of the DeltaF and data rate between -0.5 and 0.5. When using this function from the host API, you must consider the frequency shift in Hertz—within ±50% of the sampling rate in S/s—to apply to the signal.

    You can also use this function to change the phase of the signal by -180° and 180°.

  • Resample—Interpolates or decimates the streaming signal to allow you to increase or decrease its sampling rate, keeping the same I/Q signal features—frequency, phase, and amplitude. The rate between the maximum input or output frequency and the I/Q sample rate defines the interpolation/decimation factor.