The tag has no usage guidance.

learn more… | top users | synonyms

2
votes
1answer
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 ...
0
votes
1answer
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: ...
3
votes
2answers
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 $M$ ($M$ ...
3
votes
3answers
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 ...
1
vote
0answers
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 ...
0
votes
0answers
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 ...
0
votes
1answer
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 ...
0
votes
0answers
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 ...
0
votes
0answers
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 ...
0
votes
0answers
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 ...
0
votes
2answers
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 ...
2
votes
2answers
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 ...
0
votes
2answers
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] ...
0
votes
0answers
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])) {...
2
votes
3answers
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 ...
2
votes
1answer
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 ...
0
votes
0answers
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 ...
1
vote
0answers
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 ...
3
votes
1answer
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. ...
4
votes
1answer
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 ...
4
votes
1answer
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. ...
4
votes
1answer
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 ...
5
votes
1answer
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 ...
7
votes
1answer
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 ...
1
vote
0answers
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 ...
8
votes
5answers
3k views

When to consider double (64 bit) floating point for Audio

When synthesizing and processing audio on modern processors, when would one consider using something other than single precision (32 bit) floating point? Obviously, the audio coming in and going out ...
6
votes
5answers
2k views

Relative merits of fixed point vs floating point computation?

I have a digital signal processing system that operates on a fast x86 machine using double precision floating point numbers. It occurred to me that I am not really using the huge dynamic range of the ...