RF design in the 21st century: Page 3 of 7

August 04, 2016 //By Paul Dillien
My first job on leaving college was maintaining military radios. I had covered RF theory, but found that the practice was significantly different. The company’s detailed design work was performed at a remote location, and shrouded in mystery. RF design was a “black art” that only a few specialists could understand. I later moved into pure logic design, where the relative simplicity of 1s and 0s held fewer uncertainties. This ultimately led me into two decades of involvement with FPGAs.

A recently introduced transmission scheme is Multiple-Input Multiple-Output (MIMO), which improves spectral efficiency and gives a diversity gain that enhances the link reliability. It is expected that MIMO will become an important addition to meet the growing demand for data throughput.

After evaluation, the detailed design and integration of the final product begins. The board layout complexity will be defined by the number of semiconductors, discrete components, power supplies, and additional ground planes to separate signal paths. The board needs the creation of a production test and calibration strategy able to identify assembly problems.


New design paradigm

Contrast this with using an FPRF (Figure 1). The transmitter takes digital baseband signals and converts these into modulated RF signals, while the receiver decodes incoming RF and outputs baseband digital streams. The frequency range is programmable over a wide range (0.1 MHz to 3800 MHz from the second generation FPRF, or 100 kHz to 12 GHz with the addition of an Up/Down RF frequency shifter) with RF bandwidths up to 120 MHz. The whole RF chain is specified over voltage and temperature at different frequencies (Figure 2).

Figure 1: Comparison of an RF design flow for a conventional and FPRF style.

Figure 2: The typical components integrated into a transceiver.

Design category: