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31 views

Why is the frequency response different based on the amplitude of the impulse I feed into the filter?

I am working on a 2-pole IIR high-pass filter. The filter is fixed point and it is causing me some issues. I believe I'm just misunderstanding something. I am implementing everything in Octave for ...
47 views

Testing filter code w/ Octave

I want to test some code generated by this site. I selected Bessel LP 1st sample rate $600\textrm{ Hz}$ corner $8\textrm{ Hz}$ long $10\textrm{ bit}$. If I adjust the code for octave to be: ...
96 views

Minimum bit-width for fixed point FFT outputs

I was wondering if there is a formula to determine what the best case (minimum) bit-width should be for the imaginary and real outputs of an fixed-point FFT, assuming an input bit width of $M$ ($M$ ...
527 views

How do I calculate the range of a fixed-point number with $a$ integer bits and $b$ fractional bits?

What does fixed-point number range represents? Why we use formula $2^a - 2^{-b}$, why minus $2^{-b}$? Where $a$ is number of integer bits, and $b$ is number of fractional bits. If we have for example ...
112 views

Simple (Arduino) digital butterworth filter : why do I see oscillations?

I want to filter deviations from an ADC over time (low pass), not very critical. So I first tried exponential averaging, something like y= (7*y+x)/8. That gave useful results, but there is an obvious ...
110 views

Which algorithms one can use for matrix inversion (for beamforming application MVDR/LCMV) in Fixed Point?

I have implemented beamformer(MVDR/LCMV) for speech enhancement in matlab, now I am trying to convert it to fixed point implementation. during the weight calculation step correlation matrix inversion ...
37 views

scanning an image for projected points

I'm projecting a series of points onto a surface and then recording their locations in the corresponding image. However, if one goes pixel by pixel a single point may, at times, take up multiple ...
53 views

fixed point implementation of 1/x

I am trying to use fixed point to implement the function 1/x for the integer from 1 to 2048. My plan is that I use fixed point representation for some picked integers as entries in one lookup table ...
128 views

Fixing drift in a recursive fixed point filter

I'm implementing a 80-72-64-48 multi pass moving average filter for a embedded system in C and in fixed point. The implementation is a circular buffer where i'm keeping a running sum and calculating ...
44 views

Orthogonality test on fixed point FFT

I have tried the following methods to test the orthogonality on Fixed point FFT implementation. FFT: Y = A*x, where A = FFT basis and x = input, Y= FFT output If the input (x) is set to A-1(A ...
185 views

Are SOS structures better for linear phase FIR filters?

I've seen many discussions suggesting that SOS's are often/usually the preferred structure for fixed point hardware filter implementations, since they preserve conjugate pairs, etc., but I've never ...
1k views

best implementation of a real-time, fixed-point iir filter with constant coefficients

I have implemented IIR filter in direct form, parallel form, and cascade form. The input in all the cases is a kronecker delta function. How to judge which implementation is better is in real time and ...
110 views

Fixed point conversions

Have following questions about Fixed point conversion format. Suppose I want to change Fixed Point format as X1(m1,n1) (→) X2(m2,n2),m1+n1=m2+n2[Word length same], n2>n1[ Higher Fractionlength] ...
54 views

Fixed Point queries-1

I would really appreciate if I can get answers to following Fixed point queries(part-1): Converting a real number x to fixed point fraction X(m,n) [1] says: m = ceil(log2(max[abs(xmin,xmax)+1])) {...
411 views

Books/resources for implementing various mathematical functions in fixed point arithmetic for DSP purposes

I'm looking for books/resources out there that deal with, in detail, implementing mathematical functions - log/exponential/sine/cosine/inverse in fixed point arithmetic for DSP purposes. Looking for ...
510 views

inverse Fixed point number (number^-1) [closed]

Could someone please provide a method for inverting random fixed point numbers. I have as an input both positive and negative floating point numbers that should be converted into fixed point and then ...
200 views

How to Prevent overflow/saturation in fixed point implementation of Fast Data Projection Algorithm

I am trying to implement an algorithm in real-time on a Fixed point DSP (The Blackfin from Analog Devices). The algorithm does a lot of stuff, but in the middle it performs an algorithm called "Fast ...
62 views

DSP implementation recommended bibliography (good books-material related to fixed/floating point-optimization) [closed]

I am doing my first steps in embedded systems and there is a big deal of fixed point code and of course DSP optimized code.I would like please if possible to recommend any book/material related to ...
5k views

Understanding Q formats

I have some misunderstandings with Q format. Please help me in understanding this. If I say Q8 [unsigned] then there will be 8 fractional bits. Is it ? How can I represent a 1 and 1.5 in this case. ...
684 views

Fixed-point and ARM CMSIS-DSP FIR filters

I am using Q1.15 fixed-point values to represent a 12-bit signed integer value. I was wondering if it matters if I use the 11 MSB or LSB of the fractional part to represent my 11 magnitude bits? Only ...
511 views

Converting ADC output to fixed-point format

I want to convert the two's complement, 16-bit output from an ADC into a generic fixed-point format, $\rm Qm.n$, where $\rm m$ is the number of integer bits and $\rm n$ is the number of fraction bits. ...
1k views

Converting floating point number to Q-notation fixed point number in C/Java?

I am trying to convert from a floating point number to a Q-notation signed 16-bit fixed point number (e.g. Q15). How can this be done in C or Java? I searched online but could not find any available ...
339 views

Derivation of fixed-point $\tt atan2$ with self-normalization

I'm trying to understand the maths behind this Fast fixed-point $\tt atan2$ calculation with self-normalization. In particular, equation $(2)$ for theta1 appears to ...
2k views

Fixed point multiplication with negative numbers

I am stumped on a simple problem. Let's say I have two 4 bit numbers in Q0.3 format. One sign bit and three fractional bits. So I can represent $-1$ through to $0.875$. Let's now say I wish to do ...
89 views

Word-length optimization of a fixed point chain of multipliers

Let's suppose a chain of 6 multipliers: $b = a_1*a_2*a_3*a_4*a_5*a_6*a_7$, where $b$ is the output, and $a_i$ the inputs with 16 bits. How can I optimize the word lengths of the output of each ...