Modular design of products may seem to be an obvious strategy
for ease of design. While this is true, it is often not at the
forefront of engineers’ minds when they set out to achieve a
specific design goal given to them by product managers. From
a management perspective, the aim is usually to get a proof of
concept, followed closely by a product that can be released to
the market as quickly as possible. This approach can lead to
some great one-off products but, in the radio communications
market, one-off variations of a product are rare.
Different regions require different frequencies and different
markets require different features, so a single radio may have
dozens of physical configurations. Tait radios have always had
extensive intrinsic modularity and design reuse, but inevitably,
each design variation gradually diverged from the original.
Eventually, after many design iterations, common design
changes due to component obsolescence or feature refinement
required a similar amount of re-design work for each printed
circuit board (PCB) variant. In short, modularity was both aspired
to, and assumed, but few processes and tools that provided any
real engineering effort or time-to-market benefits.
The base element of a PCB is a component such as an IC
or resistor. Connect all the components and you have a
working board. From an engineering perspective, each radio
is a collection of subsystems or circuitry blocks – receiver,
transmitter, power amplifier, digital processor and power
supply and others. Many of these blocks of components are
common to a series of radios; in Tait portable products for
example, the digital section hardware is common to all radios.
But individual RF sections have circuitry that varies according
to the frequency band, and these sections must be developed
and verified independently.
Modular design has never been easy with the PCB design
tools available. However, we have worked closely with our PCB
CAD vendor, Cadence Design Systems, to develop tools and
processes to manage these sections as modules that are
well defined and under formal change control. Now, when an
engineering change is made to a module, this can easily be
rolled out to each of the radios that use it when the next design
Even with state of the art tools and processes, modular PCB
design is not easy. ICs can be shared between different logical
blocks – an eight gate device might share those gates between
multiple modules. Back-to-back modules on a PCB may have
“through vias” (electrical connections between circuitry layers
in a PCB that pass through the plane of one or more adjacent
layers) that interfere with each other. Traces (electrical
connections between components) may be required
to pass through other modules.
Designing modules and designing for modularity takes effort,
but the effort is worth it. Before formal modular design was
introduced, each frequency band roll-out and maintenance
could take weeks or even months. Now, we can bring
together independent sections of a radio very quickly – the
unprecedented speed of band rollouts of the latest portable
products is testament to this.
UNDER THE HOOD: MODULAR CIRCUITRY DESIGN
Once the new, band-specific elements of a new radio has been
designed, the PCB engineer can bring the entire design together
in a few days. This is great for our customers, because once
an opportunity is recognised, the time-to-market is no longer
restricted by CAD capture time.
There are still plenty of opportunities to improve the design
process. With the greatest commitment in the world, modularity
is difficult when it is applied retrospectively, because of the
considerable work required to define demarcation points and
work around the physical limitations of the existing mechanical
enclosures, and the third party design tools.
The next generation products at Tait will be totally designed
with modularity as a key part of the entire design process.
This is a company-wide commitment, not just restricted to a
few areas of engineering development, and that will see even
faster time to market in future.