complex_mixer RCC Worker

Application worker RCC implementation with a numerically-controlled oscillator (NCO) that uses the nco module from liquid-dsp to generate the digital sine wave for the complex multiply operation.

Detail

The RCC worker implements the NCO using the nco module from liquid-dsp, which is a free and open-source signal processing library for software-defined radios written in C that is included in the OpenCPI installation. For details on liquid-dsp and the nco module, see the liquid-dsp website.

The RCC worker converts the samples from fixed-point to floating-point numbers in order to perform the math on a general-purpose processor (GPP). The conversion equations are:

\[iq\_float = \frac{iq\_fixed}{2^{15} -1}\]

\[iq\_fixed = {iq\_float}*(2^{15} -1)\]

This conversion introduces a small amount of error in the output data that should be accounted for when using the RCC worker in an application.

The RCC worker also performs a conversion on the phase increment (phs_inc) property to adhere to the the way it is implemented in HDL. The conversion is done in the RCC implementation for the component because the division operation is very resource-intensive in HDL. The conversion equation from the component property to the input property in the liquid-dsp interface is given below:

\[liquid\_phs\_inc = phs\_inc*\frac{2\pi}{0x7FFF*2}\]

Worker Properties

• ocpi_buffer_size_out

  • Type: ushort

  • Access:

    • Parameter: False

    • Writable: False

    • Initial: True

    • Volatile: False

    • Read back: False

  • Default value: 0

Worker Ports

Inputs:

• in

  • Protocol: iqstream

  • Optional: True

Outputs:

• out

  • Protocol: iqstream

  • Optional: True

Utilization

Utilization reporting is not currently implemented.