Tunable Bandpass Filter
in [Design]
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From: qrk on 17 Nov 2009 14:43 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 :-) But he had a customer in Santa Barbara.
From: ChrisQ on 17 Nov 2009 17:21 Tim Wescott wrote: > > Yup. Not to mention that the dynamic range of most ADC's is a huge > restriction. The more you can control the bandwidth before conversion > the better off you'll be. > A average analogue hf comms radio probably has a dynamic range of 0.5uV to 1v or better at the antenna terminals and it would take a pretty special fast adc to get near that. So what is the current state of the art in sdr, using commodity hardware ?... Regards, Chris
From: Joel Koltner on 17 Nov 2009 17:23 "ChrisQ" <meru(a)devnull.com> wrote in message news:zlFMm.28177$Pi5.25630(a)newsfe08.ams2... > So what is the current state of the art in sdr, using commodity hardware > ?... > > Regards, > > Chris > > > >
From: Joel Koltner on 17 Nov 2009 17:27 "ChrisQ" <meru(a)devnull.com> wrote in message news:zlFMm.28177$Pi5.25630(a)newsfe08.ams2... > So what is the current state of the art in sdr, using commodity hardware > ?... For HF work, these guys are popular: http://www.flex-radio.com/ . They use 192kHz, 24-bit ADCs for sampling, and thereby purportedly have very good performance relative to traditional analog receivers. They are many others out there... another popular one is the TAPR "HPSDR" (high performance SDR) kits. ---Joel
From: Joerg on 17 Nov 2009 17:45
qrk wrote: > 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 :-) > > But he had a customer in Santa Barbara. Ok, that counts. I've tried to get away from ultrasound because it's mostly been medical and there is no more liability coverage available in the US. But it always snags me back, like a couple weeks ago and now it seems I'll be right back in there. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |