Clay wrote:> Randy Yates wrote: >>> The SNR threshold is lower with a PLL. Search for "Threshold Extension" >>> for details. >> That's it, John - that's what I was looking for. Apparently it's >> fairly well-known - I found it in [couch] after my original post It's >> apparently also known as FMFB (FM with feedback), which is referenced >> in both [couch] and [schwartcommtecniques]. >> >> Does anyone know how prevalent the PLL technique is in current >> demods (TVs, FM broadcast, etc.)? Is it pretty much standard >> fare now or are they somewhat unique? >> > > Hello Randy, > > I remember when the PLL technique started to become popular back during > the 1970s. Up until then people were using Ratio detectors and Foster > Seeley Discriminators. But the PLL technique became inexpensive and it > worked quite well. I figure it is the standard thing today in plain > vanilla analog FM receivers.More specifically, Signetics made some very usable early PLL chips. First, all the stereo decoders started using them. All the FM decoders soon followed. After that, every other consumer IC maker had to follow. Steve
FM Demodulation
Started by ●January 17, 2007
Reply by ●January 18, 20072007-01-18
Reply by ●January 18, 20072007-01-18
"Clay" <physics@bellsouth.net> wrote:>I figure it is the standard thing today in plain >vanilla analog FM receivers.No, not at all - still the good old discriminator is used for demodulating FM, even in high quality commercial radios. Only the latest radios, capable of digital and analog communication, sometimes use a DSP for software defined modulation and demodulation.
Reply by ●January 18, 20072007-01-18
Hey Steve, Thanks for the historical view. Steve Underwood <steveu@dis.org> writes:> [...] > More specifically, SigneticsWow - Signetics - that's a name from the past.> made some very usable early PLL chips. First, all the stereo > decoders started using them. All the FM decoders soon followed.I don't understand your delineation between a "stereo decoder" and an "FM decoder." -- % Randy Yates % "My Shangri-la has gone away, fading like %% Fuquay-Varina, NC % the Beatles on 'Hey Jude'" %%% 919-577-9882 % %%%% <yates@ieee.org> % 'Shangri-La', *A New World Record*, ELO http://home.earthlink.net/~yatescr
Reply by ●January 18, 20072007-01-18
"Clay" <physics@bellsouth.net> writes:> Randy Yates wrote: >> > >> > The SNR threshold is lower with a PLL. Search for "Threshold Extension" >> > for details. >> >> That's it, John - that's what I was looking for. Apparently it's >> fairly well-known - I found it in [couch] after my original post It's >> apparently also known as FMFB (FM with feedback), which is referenced >> in both [couch] and [schwartcommtecniques]. >> >> Does anyone know how prevalent the PLL technique is in current >> demods (TVs, FM broadcast, etc.)? Is it pretty much standard >> fare now or are they somewhat unique? >> > > Hello Randy, > > I remember when the PLL technique started to become popular back during > the 1970s. Up until then people were using Ratio detectors and Foster > Seeley Discriminators. But the PLL technique became inexpensive and it > worked quite well. I figure it is the standard thing today in plain > vanilla analog FM receivers.Hi Clay, Wow, the 70's - I am really out-of-date here. Do you (or anyone else) know of other techniques that can push the threshold extension even further down than a PLL? -- % Randy Yates % "With time with what you've learned, %% Fuquay-Varina, NC % they'll kiss the ground you walk %%% 919-577-9882 % upon." %%%% <yates@ieee.org> % '21st Century Man', *Time*, ELO http://home.earthlink.net/~yatescr
Reply by ●January 18, 20072007-01-18
"Clay" <physics@bellsouth.net> writes:> Randy Yates wrote: >> > >> > The SNR threshold is lower with a PLL. Search for "Threshold Extension" >> > for details. >> >> That's it, John - that's what I was looking for. Apparently it's >> fairly well-known - I found it in [couch] after my original post It's >> apparently also known as FMFB (FM with feedback), which is referenced >> in both [couch] and [schwartcommtecniques]. >> >> Does anyone know how prevalent the PLL technique is in current >> demods (TVs, FM broadcast, etc.)? Is it pretty much standard >> fare now or are they somewhat unique? >> > > Hello Randy, > > I remember when the PLL technique started to become popular back during > the 1970s. Up until then people were using Ratio detectors and Foster > Seeley Discriminators. But the PLL technique became inexpensive and it > worked quite well. I figure it is the standard thing today in plain > vanilla analog FM receivers.Hi Clay, Wow, the 70's - I am really out-of-date here. Do you (or anyone else) know of other techniques that can push the threshold extension even further down than a PLL? -- % Randy Yates % "With time with what you've learned, %% Fuquay-Varina, NC % they'll kiss the ground you walk %%% 919-577-9882 % upon." %%%% <yates@ieee.org> % '21st Century Man', *Time*, ELO http://home.earthlink.net/~yatescr
Reply by ●January 18, 20072007-01-18
"Clay" <physics@bellsouth.net> writes:> Randy Yates wrote: >> > >> > The SNR threshold is lower with a PLL. Search for "Threshold Extension" >> > for details. >> >> That's it, John - that's what I was looking for. Apparently it's >> fairly well-known - I found it in [couch] after my original post It's >> apparently also known as FMFB (FM with feedback), which is referenced >> in both [couch] and [schwartcommtecniques]. >> >> Does anyone know how prevalent the PLL technique is in current >> demods (TVs, FM broadcast, etc.)? Is it pretty much standard >> fare now or are they somewhat unique? >> > > Hello Randy, > > I remember when the PLL technique started to become popular back during > the 1970s. Up until then people were using Ratio detectors and Foster > Seeley Discriminators. But the PLL technique became inexpensive and it > worked quite well. I figure it is the standard thing today in plain > vanilla analog FM receivers.Hi Clay, Wow, the 70's - I am really out-of-date here. Do you (or anyone else) know of other techniques that can push the threshold extension even further down than a PLL? -- % Randy Yates % "With time with what you've learned, %% Fuquay-Varina, NC % they'll kiss the ground you walk %%% 919-577-9882 % upon." %%%% <yates@ieee.org> % '21st Century Man', *Time*, ELO http://home.earthlink.net/~yatescr
Reply by ●January 18, 20072007-01-18
"Clay" <physics@bellsouth.net> writes:> Randy Yates wrote: >> > >> > The SNR threshold is lower with a PLL. Search for "Threshold Extension" >> > for details. >> >> That's it, John - that's what I was looking for. Apparently it's >> fairly well-known - I found it in [couch] after my original post It's >> apparently also known as FMFB (FM with feedback), which is referenced >> in both [couch] and [schwartcommtecniques]. >> >> Does anyone know how prevalent the PLL technique is in current >> demods (TVs, FM broadcast, etc.)? Is it pretty much standard >> fare now or are they somewhat unique? >> > > Hello Randy, > > I remember when the PLL technique started to become popular back during > the 1970s. Up until then people were using Ratio detectors and Foster > Seeley Discriminators. But the PLL technique became inexpensive and it > worked quite well. I figure it is the standard thing today in plain > vanilla analog FM receivers.Hi Clay, Wow, the 70's - I am really out-of-date here. Do you (or anyone else) know of other techniques that can push the threshold extension even further down than a PLL? -- % Randy Yates % "With time with what you've learned, %% Fuquay-Varina, NC % they'll kiss the ground you walk %%% 919-577-9882 % upon." %%%% <yates@ieee.org> % '21st Century Man', *Time*, ELO http://home.earthlink.net/~yatescr
Reply by ●January 18, 20072007-01-18
Randy Yates wrote:> "Clay" <physics@bellsouth.net> writes: > > > Randy Yates wrote: > >> > > >> > The SNR threshold is lower with a PLL. Search for "Threshold Extension" > >> > for details. >Randy, FM threshold extensions is one of my interests. I will tell you this.. Most common FM radios TVs etc do not utilize threshold extension even if they do use a PLL for demod. (reason given below) Analog TV satellite receivers did use threshold extension demodulators, but analog satellite systems are nearly extinct today. Threshold extension is most effective for signals with a large BETA. For threshold extension to be effective, the signal must NOT be limited before it hits the PLL phase detector. Once the signal has passed through a limiter, the noise spikes do their damage and a PLL is no more effective than a standard discriminator or ratio detector. Threshold extension does not improve a "good" signal to make it excellent, it can only improve a signal that is near threshold which by definition means it is noisy. Basically it holds off the onset of noise spikes by a few dB. And it can only make a few dB of improvement. My information is qualitative. There were more quantitative papers written. I can try to dig them up if you can't find them. Try Floyd Gardner.... email me directly at mkolber "at" motorola "dot" com the return address associated with this post is a dummy. Mark
Reply by ●January 18, 20072007-01-18
Randy Yates wrote:> Hey Steve, > > Thanks for the historical view. > > Steve Underwood <steveu@dis.org> writes: >> [...] >> More specifically, Signetics > > Wow - Signetics - that's a name from the past. > >> made some very usable early PLL chips. First, all the stereo >> decoders started using them. All the FM decoders soon followed. > > I don't understand your delineation between a "stereo decoder" > and an "FM decoder."The FM detector produces -- before deemphasis -- baseband audio (the sum channel), a difference signal modulated onto a nearly-40-MHz subcarrier, and a half-carrier-frequency pilot tone. Those three components are decoded into left and right audio channels. How the FM was demodulated to get them makes no difference at all. Jerry -- Engineering is the art of making what you want from things you can get. ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
Reply by ●January 18, 20072007-01-18
On Wed, 17 Jan 2007 23:00:39 -0500, Randy Yates <yates@ieee.org> wrote:>sampson164@gmail.com writes: > >> Randy Yates wrote: >>> Gentle and Wise Readers of comp.dsp, >>> >>> Two ways to demodulate FM are: >>> >>> 1. Find the instantaneous phase (e.g., by examining the phase of the >>> analytic signal) and compute the phase differences, i.e, f = dtheta/dt. >>> >>> 2. Lock a PLL to the FM signal and use the VCO control voltage as the >>> demodulated signal. >>> >>> It seems to me that method 1 is much simpler. Why would anyone do FM >>> demodulation via method 2? >>> >>> Let me state up front that I have an idea, but I'd rather get others' >>> ideas first without biasing them. >>> -- >>> % Randy Yates % "She tells me that she likes me very much, >>> %% Fuquay-Varina, NC % but when I try to touch, she makes it >>> %%% 919-577-9882 % all too clear." >>> %%%% <yates@ieee.org> % 'Yours Truly, 2095', *Time*, ELO >>> http://home.earthlink.net/~yatescr >> >> The SNR threshold is lower with a PLL. Search for "Threshold Extension" >> for details. > >That's it, John - that's what I was looking for. Apparently it's >fairly well-known - I found it in [couch] after my original post It's >apparently also known as FMFB (FM with feedback), which is referenced >in both [couch] and [schwartcommtecniques]. > >Does anyone know how prevalent the PLL technique is in current >demods (TVs, FM broadcast, etc.)? Is it pretty much standard >fare now or are they somewhat unique?As has been stated, the vast majority of analog FM receivers for broadcast use PLLs, mostly because it's a tiny circuit with just a few transistors compared to other (especially digital) implementations and it does work quite well. So the cost/performance tradeoff is hard to beat, and the power consumption is tiny. Eric Jacobsen Minister of Algorithms, Intel Corp. My opinions may not be Intel's opinions. http://www.ericjacobsen.org
