Software Defined Radio Application Highlight: Smartphone Extension

The term software defined radio (SDR) can bring to mind large racks of equipment or a bunch of circuits connected in the lab. But the reality is that all of us interact with an SDR every day – our smartphones. A modern smartphone is capable of operating on a wide range of carrier frequencies, with various bandwidths and gain levels supporting multiple waveform standards – the very definition of an SDR. These phones have enough processing capability to be used as a host for a secondary SDR platform, and that architecture opens up some very interesting applications.

However, smartphones still don't provide ubiquitous access to arbitrary RF spectrum. They are limited to the RF bands that are anticipated for use by various modems designed into the phone – with limited future expansion capability. One of our customers approached us about integrating an SDR with a modern smartphone to provide additional RF processing capabilities in a handheld solution –  thus, Epiq's Matchstiq Z3u was born.

Matchstiq Z3u is a unique SDR. It was designed to interface with a phone or tablet as the host, whereas most SDRs assume a laptop or server will be the host. This key design philosophy instructed the Z3u's size, power consumption, and interfaces. An overview of the Z3u is shown below.

That form factor – being 70mm wide and 92 mm tall – is ideal for connecting the Z3u to the back of a phone or tablet. It leverages the USB-C interface found on modern phones/tablets as the primary interface. In fact, the Z3u can be powered and hosted by the phone and requires no additional power cables or batteries to complete an SDR system. A magnetic mount on the back of the Z3u will keep the SDR secure during operation.

Why connect one SDR to another SDR? There are many applications where this is a powerful architecture. First, while the smartphone is an SDR, it does have limits. Typically, smartphones cannot tune to any arbitrary frequency and they may not support things, like frequency hopping, that are needed for non-cellular radio waveforms. However, the Z3u can address these capability gaps in the phone without changing the form factor. Two applications show the power of this combination.

Integrating a modern smartphone or tablet with an SDR opens up a number of interesting application spaces. For example, many customers have an interest in RF spectrum analysis. Searching for unwanted RF emissions, out-of-channel interference, or completing a cellular survey are common SDR use cases. By combining this RF scanning capability in one SDR while maintaining 5G connectivity in the other SDR (the phone), the user could quickly understand the RF environment around them. Then the user can communicate with remote team members via text, call, or email. The Z3u has no effect on the phone's normal capability and doesn't need to have an app installed. All control and data display can be done in the phone's web browser. The image below shows Epiq's ERA (Embedded RF Analyzer) application doing exactly that: combining spectrum analysis with smartphone connectivity.

A second example focuses on extending the communication protocols of modern handheld devices.  While a smartphone is capable of running multiple cellular standards (WiFi, Bluetooth, and other waveforms) there are applications where other communication standards may be required. An example use case is wanting to form a mobile ad-hoc network (MANET) across a group of users. MANET networks will likely operate on non-cellular frequencies or with different modulation schemes. For this use case, the Z3u could be configured to support the MANET waveform while the smartphone continues to operate as the host while providing normal 5G connectivity. Users now have the best of both worlds – the ability to connect to the larger 5G network for external communication and web browsing, but also the ability to internally communicate within their smaller group using the MANET capability of the SDR.

These are just two examples of applications that are possible when two SDRs combine forces to enable new capabilities and use cases that neither SDR on its own could provide. If you're interested in learning more about our Matchstiq Z3u and the mobile wireless processing that it can help enable, get in touch with us.