Direct Conversion RF Front End

Hardware Setup

Front conns — **Figure 1a**: Front connections.

Rear conns — **Figure 1b**: Rear connections.

The direct conversion front end makes use of the HMC833 synthesizer as local oscillators and therefore the power up sequence should be as follows:

Ensure that the RPSA USB control cable is connected first.
Power the RPSA on.
Connect the SPI/GPIO cable to the SPI Input of the direct conversion front end.
Now power the direct conversion front end on.

More information about the HMC833 power up sequence is provided here: HMC833 Applications Information.

The FrontEnd App

usage: frontend [-h] -d DEVICE [-b BAUDRATE] [-A IPADDR] [-P PORT] [-F FRONTEND_CONFIG]

Red Pitaya RF Front End

optional arguments:
  -h, --help            show this help message and exit
  -d DEVICE, --device DEVICE
                        The front end hardware serial device
  -b BAUDRATE, --baudrate BAUDRATE
                        Baud rate (default: 0)
  -A IPADDR, --ipaddr IPADDR
                        IP address for the RPyC server instance
  -P PORT, --port PORT  TCP port for the RPyC server instance
  -F FRONTEND_CONFIG, --frontend_config FRONTEND_CONFIG
                        Frontend hardware configuration.

Configuration and capabilities

Typical Characteristics

Converter phase noise — **Figure 2**: Direct down converter phase noise.

Conv. IIP3 — **Figure 4**: Direct down converter IIP3 for various values of front end attenuation.

Conv. IMD — **Figure 3**: Direct down converter IMD as a function of front end attenuation.

Chan x-talk — **Figure 4**: Direct down converter channel cross talk.

Assembly

Design Notes

**Figure 6a**: Direct down converter IM3 test setup.

IM3 HW setup — **Figure 6b**: Direct down converter IM3 test hardware setup.

Direct down-conv — **Figure 7**: Direct down converter module schematic.

Application Source Code

A detailed description of the direct conversion front end application app code is provided here: Direct Conversion Front End