INTERNET OF THINGS HANDBOOK
Software-Defined Radio powers the IoT ADCs with SDR allow designers to reduce design efforts and focus on implementing more
RYAN LIU | MICROCHIP TECHNOLOGY INC.
fashionable features.
Software-defined
radio (SDR) technology finds its way into everything from multi-carrier multi-standby smartphones to innovative multi-mode mobile internet electronics. When enabled by SDR, a configurable transceiver works flexibly with software-defined carrier frequencies, easing the task of RF design. For many years, the evolution of wireless communication standards depended on large-scale hardware upgrades. Today, however, the adoption of SDR technologies makes it easier to find alternatives to expensive hardware. The primary motivation of the SDR concept is to overcome added costs. The three essential methods used in SDR are to move the broadband analog-digital conversion (ADC) and digital-to-analog converter (DAC) as close as possible to RF devices, use hardware as the basis of wireless communication, and maximize software options to enable functions that are traditionally only available in the RF and intermediate frequency (IF) analog domain.
To make the system more flexible at a lower cost, items such as the operating frequency band and modulation method are configured by software in the digital domain. SDR lets the same hardware handle multiple frequency bands by loading the relevant software as required. This scheme works for products ranging from smartphones to sensor networks. Meanwhile, market forces are driving the steady development of high-speed, high-precision ADC technology to enable fast and accurate processing of wireless broadband signals. ADC limitations previously constituted one of the main bottlenecks to SDR. Receiver design is a critical priority for SDR. So it is useful to review the special requirements for SDR receiver implementation. The key is the front-end. Implementation of the entire SDR system dictates how to partition specifications for the ADC and other key components. High speed, dynamic range, and richness in software configurations are essential in the ADC.
Ty p i c a l i d e a l S D R a r c h i t e c t u r e
An Ideal software-defined radio (SDR) receiver architecture is one in which there is no need for down conversion of incoming frequencies. Practicalities of ADC technology make this architecture difficult to realize.
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DESIGN WORLD — EE NETWORK
Microchip article — IoT HB 04-18 V3 FINAL.indd 10
4 • 2018
eeworldonline.com | designworldonline.com
4/17/18 3:34 PM