The full power of digital computing technologies has finally come to the radio world. This development has had a profound impact on the RF world, from the pace of innovation to the increasing availability of more powerful, specialized and inexpensive integrated circuits to perform traditional analog radio functions. In turn, the availability of these advanced digital RF technologies suggests ever more ways to expand wireless communications. The key technical elements driving the “wireless everywhere” trend include:


  • Digital signal processors (DSP), FPGAs, etc. have replaced many traditional analog radio components.

  • Moore’s Law arrives in radio – The same rate of performance advance and economy of scale that applies to digital technology in the computing industry now applies equally for many aspects of the radio world.

  • Inexpensive, intelligent digital RF becomes ubiquitous – In addition to basic cost benefits, digital intelligence is inherently included in digital RF chips cost. Thus, while radios are getting much cheaper, they are also getting “smarter.”

  • Consumers driving technology – Consumers want truly ubiquitous applications and services.

Whether commercial or military, customers want more information, faster, anywhere, anytime. Digital RF technologies make wireless access available in more places, to more people, and for less money. The demand for greater capabilities continues to drive innovation, ranging from power amplifiers to advanced radar systems and home networking. The combination of advanced technical capabilities brought about by digital RF and the increasing customer demand for more functionality and mobility has generated an explosion of innovation in wireless communications.

Big Changes in Spectrum Usage

Radio spectrum is a scarce resource. The spectrum allocations of today are widely recognized as inefficient. Allocated spectrum is underutilized much of the time, and interference problems abound. The advent of digital RF is powering rapid innovation in software defined and cognitive radio technologies. Digital RF powered SDR and CR technologies provide the new path forward and will fundamentally change spectrum allocation methodologies.

This radical change in spectrum allocation and utilization methodology is occurring over a broad range of applications, from commercial and military communications to advanced radar and other remote sensing applications. One can look to the commercial world for examples of this rapid innovation and dramatic change. Technologies such as WiFi, Bluetooth, cordless telephone, Zigbee and many others share a very limited amount of spectrum known as the ISM (industrial, scientific, medical) spectrum bands. The ISM bands are essentially unregulated “free fire zones” and as stated by the International Telecommunications Union: “Radio communication services operating within these bands must accept harmful interference, which may be caused by these [ISM] applications.” Although the potential for interference is high in the ISM band and interoperability must be maintained in these applications, innovation nevertheless is exploding through the use of digital RF technologies.

Testing Digital RF Technologies: The Two Part Problem

The explosion of digital RF has created a highly complex technology environment. With non-assigned channels, adaptive modulation, peer-to-peer communications and countless devices transmitting simultaneously within a limited radio frequency spectrum, frequent collision and interference problems occur. These collisions cause intermittent or jammed communication. In the commercial world, this is frustrating to customers and businesses. In the military and government world, it can literally mean the difference between life and death.

In order to avoid the “digital cliff” where a system or network simply stops working from overload or interference, it then becomes critical to ensure these devices do not transmit RF energy at unwanted times or unwanted frequencies and are able to function correctly in the presence of interference.

  • Find it: The first testing challenge is to discover the interfering or spurious signal, whether internally generated by a device or originating externally.

  • Characterize it: Once the interference is found, it must be thoroughly characterized. The signal of interest may have lower amplitude than other signals in the same frequency band and may happen infrequently, making it very difficult to capture.

Tektronix in the Digital RF World

Time can no longer be ignored in the RF world. Modern digital RF devices generate signals that are present one moment, absent the next and variable over time. Digital RF creates the need for test tools whose capabilities mirror the time-varying nature of today’s signals.

Tektronix Real-Time Spectrum Analyzers (RTSA) are the only analyzers in the world that are designed to specifically solve Digital RF problems. Traditional swept spectrum analyzers and vector signal analyzers (VSA) are generally not up to the task for digital RF technologies and devices. Because they essentially tune a narrow filter across a range of frequencies to generate a single frequency domain display, otherwise known as a “sweep,” traditional swept analyzers can only compile a collection of uncorrelated RF spectral activity. Even the fastest swept analyzer may miss many intermittent or rapidly changing signals.

VSAs rely on post-capture analysis techniques, and do not perform real-time tasks such as frequency domain triggering, that are required in the modern digital RF world of ever-changing, brief and bursted signals. The lack of appropriate tools requires engineers to employ off-line and often home-grown solutions that can be inefficient, time consuming, complicated and likely very expensive.

Many complex problems are illuminated for the first time by time correlating RF signal behavior in the frequency, time and modulation domains. Tools that are able to trigger on and capture transient events and easily provide time-correlated, multi-domain displays of the signal dramatically reduce the time engineers spend troubleshooting problems.