Tunable Bandpass Filter
in [Design]
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From: Joerg on 16 Nov 2009 20:19 Tim Wescott wrote: > On Mon, 16 Nov 2009 22:53:17 +0000, ChrisQ wrote: > [...] >> A crystal filter is still hard to beat on cost and performance, even now >> :-)... > > Or a ceramic one, depending on your app. > It almost has to be. I don't think you can buy 600kHz wide crystal filters. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Jim Thompson on 16 Nov 2009 20:28 On Mon, 16 Nov 2009 16:47:34 -0800, Joerg <invalid(a)invalid.invalid> wrote: >Jim Thompson wrote: >> On Mon, 16 Nov 2009 16:38:34 -0800, Joerg <invalid(a)invalid.invalid> >> wrote: >> >>> Joel Koltner wrote: >>>> "christofire" <christofire(a)btinternet.com> wrote in message >>>> news:nvGdnUeJQYfUXZzWnZ2dnUVZ8k-dnZ2d(a)bt.com... >>>>> How about visiting a library and reading some relevant books? >>>> I'd love to hear it if you could point to any book that has a large amount of >>>> text specifically devoted to *tunable* filters. I have plenty of filter books >>>> (including many of the "classics"), and most give little more than passing >>>> mention to them. (I suppose because -- other than the "mix it up to a fixed >>>> frequency with a good filter" method than Jan and I mentioned -- most >>>> implementations I'm aware of are some variety of the "brute force" method >>>> anyone would think of, so perhaps there's not a whole lot to say...) >>>> >>> For ultrasound engineers and Radar guys it's routine, except that we >>> call them tracking filters. They consist of a fixed lowpass and a >>> highpass that's tuned downwards while echoes are received. The challenge >>> is to make them reproducible in production without any alignments. Many >>> tricks there, such as servo or pilot tones, but that's as far as I am >>> allowed to speak in public. >>> >>> >> [snicker] >> >> Probably the same way I do sonar ;-) >> > >Sonar? In Arizona? You guys don't even have an ocean :-) Oh, yeah! We have farm-raised shrimp ;-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | If you wanted a President with balls why didn't you elect Hillary?
From: George Herold on 16 Nov 2009 21:34 On Nov 16, 4:32 pm, Guy Eschemann <guy.eschem...(a)gmail.com> wrote: > > It would help to know how sharp you need the filtering. > > Ideally: -60dB within the 80kHz guardband. Ouch! You mean six active elements? That makes the fast opamp solution a lot harder. George H.
From: amdx on 17 Nov 2009 07:07 "Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote in message news:h1v3g51o5g1kdsddscurau4haphfj2f8h7(a)4ax.com... > On Mon, 16 Nov 2009 16:47:34 -0800, Joerg <invalid(a)invalid.invalid> > wrote: > >>Jim Thompson wrote: >>> On Mon, 16 Nov 2009 16:38:34 -0800, Joerg <invalid(a)invalid.invalid> >>> wrote: >>> >>>> Joel Koltner wrote: >>>>> "christofire" <christofire(a)btinternet.com> wrote in message >>>>> news:nvGdnUeJQYfUXZzWnZ2dnUVZ8k-dnZ2d(a)bt.com... >>>>>> How about visiting a library and reading some relevant books? >>>>> I'd love to hear it if you could point to any book that has a large >>>>> amount of >>>>> text specifically devoted to *tunable* filters. I have plenty of >>>>> filter books >>>>> (including many of the "classics"), and most give little more than >>>>> passing >>>>> mention to them. (I suppose because -- other than the "mix it up to a >>>>> fixed >>>>> frequency with a good filter" method than Jan and I mentioned -- most >>>>> implementations I'm aware of are some variety of the "brute force" >>>>> method >>>>> anyone would think of, so perhaps there's not a whole lot to say...) >>>>> >>>> For ultrasound engineers and Radar guys it's routine, except that we >>>> call them tracking filters. They consist of a fixed lowpass and a >>>> highpass that's tuned downwards while echoes are received. The >>>> challenge >>>> is to make them reproducible in production without any alignments. Many >>>> tricks there, such as servo or pilot tones, but that's as far as I am >>>> allowed to speak in public. >>>> >>>> >>> [snicker] >>> >>> Probably the same way I do sonar ;-) >>> >> >>Sonar? In Arizona? You guys don't even have an ocean :-) > > Oh, yeah! We have farm-raised shrimp ;-) > > ...Jim Thompson Farm raised shrimp, aren't they rubbery and bland. Buy only wild caught Florida shrimp. http://www.wildamericanshrimp.com/main.html Click on ad in lower right corner http://www.underwatertimes.com/news.php?article_id=81003524697 http://www.fl-aquaculture.com/videos/flash/Florida_Wild_Caught_Shrimp_TV.htm Mike
From: Jim Thompson on 17 Nov 2009 09:15
On Tue, 17 Nov 2009 06:07:12 -0600, "amdx" <amdx(a)knology.net> wrote: > >"Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote in >message news:h1v3g51o5g1kdsddscurau4haphfj2f8h7(a)4ax.com... >> On Mon, 16 Nov 2009 16:47:34 -0800, Joerg <invalid(a)invalid.invalid> >> wrote: >>[snip] >>> >>>Sonar? In Arizona? You guys don't even have an ocean :-) >> >> Oh, yeah! We have farm-raised shrimp ;-) >> >> ...Jim Thompson > > Farm raised shrimp, aren't they rubbery and bland. Buy only wild caught >Florida shrimp. Farm grown shrimp are excellent.... and _disease_free_. (Artificial salt water lakes... a giant version of my aquarium ;-) They're working on a similar concept for oysters. > >http://www.wildamericanshrimp.com/main.html Click on ad in lower right >corner > >http://www.underwatertimes.com/news.php?article_id=81003524697 > >http://www.fl-aquaculture.com/videos/flash/Florida_Wild_Caught_Shrimp_TV.htm > > Mike > ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | If you wanted a President with balls why didn't you elect Hillary? |