FPGA Central

Back several years ago I implemented a DSP based, PLL FM demod for
satellite downlink application. It achieved about 3 to 4 dB of threshol
extension over a conventional demod. My question is, can greater extensio
be achieved using PLL or FMFB techniques in special cases?

Specifically, can greater extension be achieved if it is only necessary t
recover a narrow portion of the baseband? Say for example the baseban
contains both a wideband and narrowband signal. If the goal is to recover
only the narrowband signal instead of the entire composite baseband, ca
greater extension be achieved than otherwise?

My limited understanding of PLL and FMFB systems suggests to me that th
feedback loop may be optimized for a specific segment of the baseband.

Thanks.

PalapaGuy wrote:
> Back several years ago I implemented a DSP based, PLL FM demod for a
> satellite downlink application. It achieved about 3 to 4 dB of threshold
> extension over a conventional demod. My question is, can greater extension
> be achieved using PLL or FMFB techniques in special cases?

You can achieve better performance if you can predict the waveform of
the modulation signal.

> Specifically, can greater extension be achieved if it is only necessary to
> recover a narrow portion of the baseband?

Not unless your modulation signal is concentrated in this narrow portion
of the baseband.

> Say for example the baseband
> contains both a wideband and narrowband signal. If the goal is to recover
> only the narrowband signal instead of the entire composite baseband, can
> greater extension be achieved than otherwise?

Generally not. It depends on how well you can predict the composite
signal, and what is the FM index.

> My limited understanding of PLL and FMFB systems suggests to me that the
> feedback loop may be optimized for a specific segment of the baseband.

You can, but it works only in the certan cases.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

On Nov 11, 2:02*pm, "PalapaGuy" <gmwemail-...@yahoo.com> wrote:
> Back several years ago I implemented a DSP based, PLL FM demod for a
> satellite downlink application. *It achieved about 3 to 4 dB of threshold
> extension over a conventional demod. *My question is, can greater extension
> be achieved using PLL or FMFB techniques in special cases?
>
> Specifically, can greater extension be achieved if it is only necessary to
> recover a narrow portion of the baseband? *Say for example the baseband
> contains both a wideband and narrowband signal. *If the goal is to recover
> only the narrowband signal instead of the entire composite baseband, can
> greater extension be achieved than otherwise?
>
> My limited understanding of PLL and FMFB systems suggests to me that the
> feedback loop may be optimized for a specific segment of the baseband.
>
> Thanks.

This old paper may be of interest:

http://ntrs.nasa.gov/archive/nasa/ca...972014482..pdf

>On Nov 11, 2:02=A0pm, "PalapaGuy" <gmwemail-...@yahoo.com> wrote:
>> Back several years ago I implemented a DSP based, PLL FM demod for a
>> satellite downlink application. =A0It achieved about 3 to 4 dB o
thresho=
>ld
>> extension over a conventional demod. =A0My question is, can greate
exten=
>sion
>> be achieved using PLL or FMFB techniques in special cases?
>>
>> Specifically, can greater extension be achieved if it is only necessar
t=
>o
>> recover a narrow portion of the baseband? =A0Say for example th
baseband
>> contains both a wideband and narrowband signal. =A0If the goal is t
reco=
>ver
>> only the narrowband signal instead of the entire composite baseband
can
>> greater extension be achieved than otherwise?
>>
>> My limited understanding of PLL and FMFB systems suggests to me tha
the
>> feedback loop may be optimized for a specific segment of the baseband.
>>
>> Thanks.
>
>This old paper may be of interest:
>
>http://ntrs.nasa.gov/archive/nasa/ca...82_1972014482=
>.pdf
>
That link doesn't work for me. It produces a 404 error. Can you pleas
recheck it?

PalapaGuy wrote:
>> On Nov 11, 2:02=A0pm, "PalapaGuy" <gmwemail-...@yahoo.com> wrote:
>>> Back several years ago I implemented a DSP based, PLL FM demod for a
>>> satellite downlink application. =A0It achieved about 3 to 4 dB of
> thresho=
>> ld
>>> extension over a conventional demod. =A0My question is, can greater
> exten=
>> sion
>>> be achieved using PLL or FMFB techniques in special cases?
>>>
>>> Specifically, can greater extension be achieved if it is only necessary
> t=
>> o
>>> recover a narrow portion of the baseband? =A0Say for example the
> baseband
>>> contains both a wideband and narrowband signal. =A0If the goal is to
> reco=
>> ver
>>> only the narrowband signal instead of the entire composite baseband,
> can
>>> greater extension be achieved than otherwise?
>>>
>>> My limited understanding of PLL and FMFB systems suggests to me that
> the
>>> feedback loop may be optimized for a specific segment of the baseband.
>>>
>>> Thanks.
>> This old paper may be of interest:
>>
>> http://ntrs.nasa.gov/archive/nasa/ca...82_1972014482=
>> .pdf
>>
> That link doesn't work for me. It produces a 404 error. Can you please
> recheck it?

It worked for me when it was first posted, but not a few hours later.

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

On Nov 11, 11:08*pm, "PalapaGuy" <gmwemail-...@yahoo.com> wrote:
> >On Nov 11, 2:02=A0pm, "PalapaGuy" <gmwemail-...@yahoo.com> wrote:
> >> Back several years ago I implemented a DSP based, PLL FM demod for a
> >> satellite downlink application. =A0It achieved about 3 to 4 dB of
> thresho=
> >ld
> >> extension over a conventional demod. =A0My question is, can greater
> exten=
> >sion
> >> be achieved using PLL or FMFB techniques in special cases?
>
> >> Specifically, can greater extension be achieved if it is only necessary
> t=
> >o
> >> recover a narrow portion of the baseband? =A0Say for example the
> baseband
> >> contains both a wideband and narrowband signal. =A0If the goal is to
> reco=
> >ver
> >> only the narrowband signal instead of the entire composite baseband,
> can
> >> greater extension be achieved than otherwise?
>
> >> My limited understanding of PLL and FMFB systems suggests to me that
> the
> >> feedback loop may be optimized for a specific segment of the baseband.
>
> >> Thanks.
>
> >This old paper may be of interest:
>
> >http://ntrs.nasa.gov/archive/nasa/ca...720014482_1972...
> >.pdf
>
> That link doesn't work for me. *It produces a 404 error. *Can you please
> recheck it?

Working for me at 1201 GMT Thur Nov 12