Specialized Integrated Circuits

As digitization in radio receivers moves closer to the receive antenna, more of the traditionally 

analog receiver functions will be replaced with digital signal-processing algorithms. In addition, 

the area of digital communications requires extensive digital signal processing. While the speed 

of general digital signal processors continues to increase, specialized integrated circuits (ICs) 

can, in general, digitally implement radio receiver functions faster. Use of these specialized ICs 

should be quite prevalent in radio receiver applications of the future.  

A current example of this type of specialized IC is the single chip digital downconverter. Digital 

downconversion offers a clear advantage over conventional analog downconversion by providing 

more precise frequency control of the LO and by providing a more ideal mixing operation. 

Current digital downconverters can control LO frequencies to within less than .01 Hz out of 

several MHz and can provide mixing with over 100 dB of SFDR. In addition, on-chip filters can 

be programmed to produce almost any desired bandwidth while preserving linear phase. In 

contrast to analog equivalents, these chips provide reproducible component accuracies that do 

not degrade over time or temperature.  

The Harris HSP50016 is a programmable monolithic digital downconverter capable of extracting 

a narrow baseband signal from a wideband input bandpass signal (RF or IF) [39], [40]. The 

digital downconverter multiplies a digitized wideband input signal by samples representing both 

an in-phase LO and a quadrature-phase LO to produce in-phase and quadrature-phase baseband 

signals. Next, the digital downconverter filters the in-phase and quadrature-phase signals to 

extract the channel of interest. It then decimates the output to a sampling rate of twice the 

maximum frequency of the signal of interest. The digital downconverter can also be configured 

to provide a downconverted version of the input bandpass signal at a new IF. The HSP50016 can 

operate on 16-bit data at a rate of up to 52 Msamples/s [41].  

 

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