Filter designer equiripple matlab code#

In order to get the 16-bit filter coefficients, the following line is used: The design of the TFIR is saved in the system object Hmd. Hd = design (d, 'equiripple', 'B1Weights',W1, 'B2Weights',W2, 'SystemObject',true ) In the following piece, B=2, which means there are two bands in the design.ĭ = fdesign. Given the tap number N, the required response on passband and stopband ( A1 and A2), as well as the corresponding weights ( W1 and W2), we can now use fdesign.arbmag 5)įunction to design the TFIR filter. N = min ( 16* floor ( (Fdac*DAC_mult )/ ( 2*Fin ) ),Nmax ) % Determine the number of taps for TFIR switch tfirint

Filter designer equiripple matlab code#

Therefore, the following piece of code calculates the tap number N: In the AD9361 Filter Guide, it says “the number of taps is configurable between a minimum of 16 taps and a maximum of 128 taps in groups of 16”. One other constraint about TFIR is the number of filter taps. Wg2 = ( sqrt (FIR_interp )*wg1 )/ (dBinv (- dBstop ) ) Wg1 = abs (freqz (Filter1,omega (Gpass+ 2: end ),Fdac ).*analogresp ( 'Tx',omega (Gpass+ 2: end ),Fdac,b1,a1,b2,a2 ) ) On stopband, the required response rg = 0 and the weight w is: While on the Rx side, the ADC is represented by a sinc^3 function. On the Tx side, the DAC is represented by a sinc function.

Please note the phase equalization process may take a few minutes, depending on the performance of your PC, since it tries to find a best target delay which yields the minimum group delay variance.įor the analog filters, unlike digital filter, there is no “cascade” function to combine them and quickly calculate the composite response, so we made a helper function analogresp to calculate the overall response of the two analog filters and the converter.

Also note that when the design process completes, there is an updated target delay number (this number is 0 before phase equalization) shown in the “Filter Options” portion. Comparing the group delay variance in the Results portion, it is decreased from 16.6 ns to 1.52 ns with phase equalization. The main purpose of the phase equalization is to reduce the pass band group delay *variance* brought by analog filters, digital filters and FIR filter, so that for signals at different frequencies, they will be delayed by an almost identical amount when going through the filter chain.Īfter you click “Design Filter”, the phase equalization part of the FIR design file is executed, and you will get an updated FIR filter design. Phase Equalization: If you would like to have the FIR filter do phase equalization, you can turn on the “Phase Equalization” option, as shown in the figure below. If you are mainly interested in pass band, click the top button, it will open the following three figures: One is from 0 Hz to half of the data rate, the other is from 0 Hz up to half of the converter rate. For your convenience, we provide this tool on two different frequency scales. If you are interested in more details of the design performance, you can click the “FVTool” buttons left to “Filter Results” to launch the Filter Visualization Tool (fvtool) provided by The MathWorks. From these numbers, you will get an idea whether the design meets the requirements quantitatively. Below it, on the right, you will see a “Filter Results” portion, where the actual Apass, Astop, the number of FIR taps and the pass band group delay variance are shown. The x-axis is from 0 to half of the data rate. If you are satisfied with all the parameters, you can go ahead and click “Design Filter” to start the design.Īs soon as the design process completes, you will see a magnitude plot displayed on the top half of the GUI, where the specified Fpass, Fstop, Apass and Astop are highlighted in the plot. There are three categories of input parameters: magnitude specifications, frequency specifications, and AD936x clock settings. In addition, you can also save your favorite parameter settings in this list, such as “foobar (Rx & Tx)” shown in the figure.Īssume that you choose the “LTE10 (Rx & Tx)” profile, after you click it, all the parameters are filled in automatically for you, as shown in the figure below. Occupied RF Bandwidth from between 1.08MHz to 19.8MHz with 180kHz steps complies with the spec, and while these filters can be designed (manually) they are not included as defaults. The LTE Release-8 physical layer specification actually supports 105 different bandwidth options (not just the 6 shown above).