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Article #818Re: Rigol caught with their pants down! (DS1052E Oscilloscope)
From: Ray
Date: Mon, 20 Jul 2009 21:55
Date: Mon, 20 Jul 2009 21:55
46 lines
3190 bytes
3190 bytes
blackhead <larryharson@softhome.net> wrote in news:f68bfd0f-8827-4cb3-8b05-c9e0ddec8ec4@a7g2000yqk.googlegroups.com: > On 20 July, 10:06, Ray <s...@spamalot.com> wrote: >> blackhead <larryhar...@softhome.net> wrote >> innews:0268880f-5658-44fe-8908- 579f2f1031ba@s31g2000yqs.googlegroups.c >> om: >> >> >> > So give it a 1 Ghz signal and see if it it looks right then. >> >> Umm, no. Ever heard of Nyquist? >> >> >> BTW if you had exactly 1GHz going in, and it manged to sneak pass the >> front end, you'd end up with a straight line at some DC level. >> >> Ray > > I have heard of Nyquist, just forgot to apply him in this case :) > There will be an anti aliasing filter in the front end so you wont see > much if you put in anything close to half the sampling rate = 500Mhz. > > > Anti aliasing filters do not have to be purely low pass filters set below the Nyquist frequency. You can also use band pass filters to digitise a frequency above Nyquist or even HIGHER than the sampling frequency. You will not get the original signal, but you will get an undersampled signal that still can be used in certain applications such as digital receivers sampling off IF chains. The important part of the filter design is to have very good rejection of signals outside the designed centre frequency so no signals present at the usual "baseband" are present. Obviously the ADC must be capable of functioning at the desired input frequency. It works, and is quite commmon. Ray
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X-Google-Thread: a5a6238865,22f414e979f56ad3 X-Google-Attributes: gida5a6238865,public,usenet X-Google-NewGroupId: yes X-Google-Language: ENGLISH,ASCII-7-bit Path: arc1-ca.pugleaf.net!g2news2.google.com!news2.google.com!border1.nntp.dca.giganews.com!border2.nntp.dca.giganews.com!nntp.giganews.com!backlog2.nntp.dca.giganews.com!nntp.netspace.net.au!news.netspace.net.au.POSTED!not-for-mail NNTP-Posting-Date: Mon, 20 Jul 2009 16:55:04 -0500 Newsgroups: sci.electronics.design,aus.electronics Subject: Re: Rigol caught with their pants down! (DS1052E Oscilloscope) From: Ray <spam@spamalot.com> References: <9ZD8m.24080$Qg6.2130@newsfe14.iad> <18i665p468as493tdqltq8ms0iqqm9c34n@4ax.com> <NJM8m.24727$FP2.3819@newsfe05.iad> <0268880f-5658-44fe-8908-579f2f1031ba@s31g2000yqs.googlegroups.com> <Xns9C4EC24DB90B6zathranetpacenetau@216.196.97.142> <f68bfd0f-8827-4cb3-8b05-c9e0ddec8ec4@a7g2000yqk.googlegroups.com> Organization: Your Company Message-ID: <Xns9C4F50857CD75zathranetpacenetau@216.196.97.142> User-Agent: Xnews/5.04.25 Date: Mon, 20 Jul 2009 16:55:05 -0500 Lines: 46 X-Usenet-Provider: http://www.giganews.com NNTP-Posting-Host: 220.253.16.34 X-Trace: sv3-kKFC8+LB1RPubGj7yntil/FgO+JCjeb+1AAjhddGIfgZEOzXsr9arVDO92XhK9PSDhj1rTOv0YfsOPM!WC0dKwlRXbW1o5/vczSDOzJcK07PVS81vr0aFBgoKWTdjb4hwdCCxb04ulky9HhVy/MrHg0CMGYk!gAp4HGmX4AO31ODckmoyqle7 X-Complaints-To: abuse-team@netspace.net.au X-DMCA-Complaints-To: www.netspace.net.au under copywrite X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly X-Postfilter: 1.3.39 X-Original-Bytes: 2936