ECN - February 2016

The biggest challenge by far has been the age old trade-off between (power amplifier) efficiency and linearity. To date, despite all of the advances made in area of linearization, we are simply in a situation where we cannot end up with the efficiency of a compressed amplifier when amplifying modulated waveforms with appreciable peak to average ratios at frequencies and bandwidths typically employed for satellite communications.

David Goins, CTO, Windfreak Technologies

The biggest challenge facing a designer of wireless applications is not necessarily the RF part of the design. That’s what some people call the “Black Magic” portion of wireless devices.

In my experience, the RF portion of the circuit complexity
has been getting easier and easier. Over the years, there has
been massive integration of features into fewer and fewer
chips. My last project was a dual channel, USB-controlled,
RF signal generator that operates from 55 MHz to 13. 6 GHz.

The RF circuits were all 50 ohms in / 50 ohms out. I actually got good results on an FR4 printed circuit board all the way up to 13. 6 GHz. Other than some isolation issues, the first prototype worked well and required little time.

The most challenging part of designing a wireless device is definitely programming. The RF circuits in the SynthHD USB-based RF signal generator are serially programmed by an onboard microprocessor that needs to do 64-bit math.

There are 15- 32-bit registers that need to be calculated for the RF circuit, plus some D/As for controlling circuit gain. The processor also needs to communicate via USB to a personal computer. Therefore, I selected a 32-bit ARM microcontroller from Freescale.

For the first shippable units, the firmware that went into the processor was greater than 3,000 lines of code including comments. Since the first shipments, more lines have been written for expanded features and bug fixes.

Firmware and software development have been 95percent
of the work involved in the development of the RF signal
generator—it also promises to be 95percent
of the sustaining work for that product in the
future. Clearly this is the biggest challenge to
designing wireless applications.

Peder Rand, Applications Manager, Wireless Connectivity Solutions, Texas Instruments

The first and sometimes the biggest challenge you face
is choosing the right wireless
technology. There are lots of good options
available, but they all have limitations and
it’s important to uncover them before you
are too far down the path of implementation.

A common pitfall is choosing a wireless technology that is unnecessarily complex for the application. Implementation using a complex protocol may still be relatively quick, but the testing phase can be very demanding with many modalities and corner cases.

The second challenge is getting the range that you want without spending too much power or violating any regulatory requirements. There are some very real physics that dictate how well a signal on a certain frequency propagates through a body, house or building. A well-defined worst-case