#ANALOG FILTER DESIGNER GENERATOR#

A Rohde & Schwarz SMW200A vector signal generator was used to generate 5G-NR test vectors as well as single and multitone vectors, and a Rohde & Schwarz FSW was used to measure the output spectrum from the DAC. The user guide for this configuration can be found here. The AD9082 MxFE was set up for testing by interfacing with ADI’s ADS9 development platform for controlling the analog-to-digital converters (ADCs) and digital-to-analog converters (DACs), and to process the output data. The data and results from the filter implementations are verified using the platform’s loopback mode connected to a spectrum analyzer. The platform used to demonstrate a real digital filter is Analog Devices’ AD9082 mixed-signal front end (MxFE ®). The scope of this article will not extend to applications of infinite impulse response (IIR) filters and will stay constrained to 192-tap filters with a sample rate of 1500 MSPS. We’ll see what a real and practical digital filter produces for results when filtering both single tones and their harmonics, as well as multitone test vectors that demonstrate the filter profile over a larger band of frequencies. I will introduce the lab setup and how the results were verified, as well as go over the specifications of the system used. Let’s take a look at what implementing a digital filter would look like on a high speed data acquisition platform. FIR filters can also have a linear phase response, which makes them especially useful in RF applications where timing and group delay are important. FIR filters are inherently stable because there is no feedback used, and therefore no risk of driving an input that causes an output to compound and grow unbounded. Each tap represents time delay and computational resources, so when N grows large, so does the time delay and power consumption. The main drawback of increased tap count is resources. More taps, N, in an FIR filter means sharper responses, flatter pass bands, and steeper transition bands. The discrete implementation is shown in Equation 1 and is referred to as a finite impulse response (FIR) filter. Digital filters accomplish this by summing and weighting discrete signal samples and performing this operation over the length of the input array.

Digital Filter Basicsīoth digital filters and analog filters serve the same purpose-to ideally allow certain frequency components to pass through undistorted while completely attenuating all other frequencies. Fear not the complexities of digital design this article demonstrates a quick and easy method for implementing simple yet powerful digital filters for RF systems. Of course, digital filters are not without flaw, but their elegance and ease of use in increasingly common mixed-signal environments make them a great choice for your systems’ filtering needs. They can filter harmonics or isolate frequency bands to prevent intersymbol interference while saving you from the hassle of part procurement, PCB layout, and variations that come with their analog counterpart.

Easy Digital Filter Applications for Not-So-Easy RF System Designsĭigital filters provide a meaningful way of controlling the input spectra of communication systems over a wide range of applications.

Analog filter designer