python - Bandpass filter not respecting cutoff -


i'm using filter in python:

def bandpass_firwin(ntaps, lowcut, highcut, fs, window='hamming'):     nyq = 0.5 * fs     taps = firwin(ntaps, [lowcut, highcut], nyq=nyq, pass_zero=false,                   window=window, scale=false)

where ntaps=128; lowcut = 0.7 ; highcut = 4 ; fs = 61

i filter signal has 610 samples sampled @ 61 hz (so 10 sec long).

when @ spectrum of signal has been filtered bandpass filter, see this:

enter image description here

the peek in spectrum @ 0.61 hz. not in range of 0.7 4 hz.

how possible ? & how can prevent ?

your filter isn't magic - there intrinsic limitations on bandwidth. try using more taps if need tight cutoff.

the more taps use though, more need think edge effects , how handle them (as edge assumptions encroach further , further data block). perhaps want smooth roll off @ edge? or mirror , repeat of data? perhaps can ignore entirely...

another technique convolution filter directly in frequency domain multiplying desired spectrum. imposes edge assumption signal repeated, though can change extending signal see fit. if want know support of equivalent fir filter, take ifft of window , can see how beginning of time block smear beginning.


Comments

Post a Comment

Popular posts from this blog

php - Why I am getting the Error "Commands out of sync; you can't run this command now" -

the documentation of error mentioned in title says if commands out of sync; can't run command now in client code, calling client functions in wrong order. this can happen, example, if using mysql_use_result() , try execute new query before have called mysql_free_result(). can happen if try execute 2 queries return data without calling mysql_use_result() or mysql_store_result() in between. from here: http://dev.mysql.com/doc/refman/5.0/en/commands-out-of-sync.html but in first query not fetching data mysql database, inserting. , in second query getting data database. here code $connection = mysqli_connect("localhost","username","password","tbl_msgs"); if(mysqli_connect_errno($connection)) { die("failed connect mysql: " . mysqli_connect_error()); } $query = "insert users (total_comments, total_views) values ({$total_comments}, {$total_views});"; $query .= "insert msgs (no...
Read more

linux - Does gcc have any options to add version info in ELF binary file? -

i mean whether gcc can insert source code version infor elf binary section or similar. not want change source file, add info gcc option in makefile. you can emit version info text file, turn text file object file statically link executable. the first step simple have write code: script or write version info in format plain text file. write makefile rule produce version.o version.txt, using objcopy . you'll have object file 2 useful symbols defined in it: beginning , end of textual version info. add generated object executable, , you'll able access version 2 ways: running strings on binary, or writing code in application print version string (you'll need declare start , end symbols variables in header file).
Read more

java - Are there any classes that implement javax.persistence.Parameter<T>? -

i'm using named queries fetch entities database using jpa , hibernate , came across puzzling me: how come there no default implementations of javax.persistence.parameter interface? i rather impressed how @staticmetamodel used criteriabuilder in jpa2 meaning type safety , don't have mess around setting string names. wanted apply similar of jpa1 ejb's i'm working on: dealergroup_.class: public dealergroup_ { public parameter<integer> id = new parameterimpl<integer>("id"); /// etc... } dealergroupfacade.class: // ... public dealergroup fetch(integer id) { typedquery<dealergroup> query = em.createnamedquery("dealergroup.fetchbyid", dealergroup.class); query.setparameter(dealergroup_.id, query); return query.getsingleresult(); } // ... i surprised find there no implementations of parameter interface - of course, implement myself absence makes me suspicious may mistake using in way? should implementing parameter...
Read more