Mixed Domain Oscilloscopes for Detecting Noise in Wireless Embedded Systems

Test probe P100-M3

Photocoupler

Summary:

A common task that designers must face when integrating a radio chip or module into a typical embedded system is to track and eliminate noise and spurious signals. Potential sources of noise include switching power supplies, digital noise from other parts of the system, and sources of external noise. When considering noise, you should also consider any possible interference from the radio, which is an important consideration to avoid interference with other radios and to meet regulatory requirements.

Finding sources of noise has not always been an easy task. However, the added wireless technology has further increased the complexity of embedded systems, and designers face greater obstacles in tracking the source of noise. We must face the reality that wireless technology is everywhere. It is estimated that there are more than 1 billion wireless devices in use today, and 30% of embedded designs now include wireless capabilities, and this number continues to grow every day.

When adding wireless functionality to an embedded system, there are typically many problems encountered in integration. For battery-powered systems, switching regulators are typically used to achieve the highest practical efficiency at the lowest cost. Power output power is also often a problem. This requires the use of high switching frequencies to minimize output filter specifications and requirements. These supplies typically have ripple on the output voltage, which may be displayed on the RF transmitter output, especially under load or when the battery is low. To avoid this, additional power filtering may be required to avoid unwanted damage to the radio signal, although this can result in undesirable cost or power.

The hardware circuitry and software configuration of the radio chip or module may affect the quality of the transmitted signal. If set and filtered improperly, the radio may cause interference to other radio systems or may not meet the corresponding regulatory standards. Some radio systems require channel filters, RF surface acoustic waves, and other relatively costly filters to meet regulatory requirements for out-of-channel and out-of-band emissions.

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