I am currently designing a 1GHz fixed frequency output phase locked loop. I
am mid way through the design and was just speaking with a colleague on the
feasibility of such an application. He seemed to think that this would an
extreme undertaking and would be almost impossible to implement with
discrete surface mount components on a PWB. I'm new to the field and this
has me worried. Can anyone reassure me or does the collective brilliance of
the PIClist side with the daunting opinion of my friend. Thanks in advance.
PWB? You mean a PCB? Yes, its very doable on a PCB. Needs some careful
design and good artwork on the PCB. Achieving very high spectral purity
and high accuracy over a wide temperature range (temperature mostly
effects your reference input only though) can be difficult but for most
applications (e.g. Bluetooth) very simple designs can be made to work on
FR4 with good results. Though long gone are the days when you had to
design every part of the PLL discretely. There are many PLL ICs now
available that will do pretty much everything for you.
There is a lot of information available on the web on PLLs and
application notes on manufacturer websites. National semiconductors has
Webench online design environment that may be helpful as well
(http://www.national.com/appinfo/wireless). National has some PLL+VCO in
one chip like the LMX2512 (http://www.national.com/pf/LM/LMX2512.html)
but that kinda takes the fun out of designing a PLL yourself. Plus I
don't know if you'll find one for the exact frequency you are looking
for. Maybe you can make that exact frequency by designing a compensated
oscillator as the reference and shift the reference input to the PLL
just a tad bit to get the output frequency you need.
Also if you are completely new to PLL design and RF work, an eval board
for one of these PLL chips may give you a jump start.
PWB means "Printed Wiring Board" (wire wrapped). I think you are going to have some serious problems doing a 1GHz system on a PWB. The amount of spurs and misc noise generated on the PWB will destroy the spectral purity of your system. You need impedance matching circuits and filtering, a PWB will make this extremely difficult.
Best regards,
Steve
Shahid Sheikh <.....Shahid.SheikhKILLspam@spam@ZEESHANELECTRONICS.COM> wrote:
PWB? You mean a PCB? Yes, its very doable on a PCB. Needs some careful
design and good artwork on the PCB. Achieving very high spectral purity
and high accuracy over a wide temperature range (temperature mostly
effects your reference input only though) can be difficult but for most
applications (e.g. Bluetooth) very simple designs can be made to work on
FR4 with good results. Though long gone are the days when you had to
design every part of the PLL discretely. There are many PLL ICs now
available that will do pretty much everything for you.
There is a lot of information available on the web on PLLs and
application notes on manufacturer websites. National semiconductors has
Webench online design environment that may be helpful as well
(http://www.national.com/appinfo/wireless). National has some PLL+VCO in
one chip like the LMX2512 (http://www.national.com/pf/LM/LMX2512.html)
but that kinda takes the fun out of designing a PLL yourself. Plus I
don't know if you'll find one for the exact frequency you are looking
for. Maybe you can make that exact frequency by designing a compensated
oscillator as the reference and shift the reference input to the PLL
just a tad bit to get the output frequency you need.
Also if you are completely new to PLL design and RF work, an eval board
for one of these PLL chips may give you a jump start.
> PWB means "Printed Wiring Board" (wire wrapped). I think you are going to
have some serious problems doing a 1GHz system on a PWB. The amount of spurs
and misc noise generated on the PWB will destroy the spectral purity of your
system. You need impedance matching circuits and filtering, a PWB will make
this extremely difficult.
>
> Best regards,
> Steve
> PWB means "Printed Wiring Board" (wire wrapped).
Hi Steve,
I grew up with the term PCB, and PWB always seemed a bit foreign to me.
I could be off the mark so someone please correct me if I'm wrong, but my
understanding is that PWB and PCB are synonymous in what they represent, and
neither of the terms refer to wire-wrapping which is a different process.
Perhaps PWB is an older term before PCB became widely used?
But, maybe not, see below.
Does someone know the history behind this?
If the below reason is true for using the term PWB is true, this acronym
name game is pretty interesting:
"In Japan, the printed wiring board used to be called a "Printed Circuit
Board." Nowadays in Japan the name "Printed Circuit Board" is not used
because the initials of "Printed Circuit Board" are "PCB." PCB also stands
for "Polychlorinated Biphenyls (PCBs)," which is a poison. So in Japan, we
refer to the boards as "Printed Wiring Boards." In other countries, they are
still referred to as "Printed Circuit Boards," or PCBs."
If you can find a copy of PUFF, you should be able to
design the PCB using lumped elements - this would help
your design. You should use only Duroid or similar
board material for the PCB - plain phenolic won't cut
it!!!
> If you can find a copy of PUFF, you should be able to
> design the PCB using lumped elements - this would help
> your design. You should use only Duroid or similar
> board material for the PCB - plain phenolic won't cut
> it!!!
>
> Lee
>
I guess I was wrong. I have always been exposed to the term PCB or PCA (Printed Circuit Assembly). I worked with an old engineer a few years back that used PWB to refer to wire wrapped boards, see you do learn something new everyday!!
Steve
Bob Ammerman <KILLspamrammermanKILLspamVERIZON.NET> wrote:
> PWB means "Printed Wiring Board" (wire wrapped). I think you are going to
have some serious problems doing a 1GHz system on a PWB. The amount of spurs
and misc noise generated on the PWB will destroy the spectral purity of your
system. You need impedance matching circuits and filtering, a PWB will make
this extremely difficult.
>
> Best regards,
> Steve
> I guess I was wrong. I have always been exposed to the term PCB or PCA
(Printed Circuit Assembly). I worked with an old > engineer a few years
back that used PWB to refer to wire wrapped boards, see you do learn
something new everyday!!
>
> Steve
> Bob Ammerman <RemoveMErammermanTakeThisOuTVERIZON.NET> wrote:
>> PWB means "Printed Wiring Board" (wire wrapped). I think you are going
to
>have some serious problems doing a 1GHz system on a PWB. The amount of
spurs
>and misc noise generated on the PWB will destroy the spectral purity of
your
>system. You need impedance matching circuits and filtering, a PWB will
make
>this extremely difficult.
>
> Best regards,
> Steve
I have also seen EWB for Etched Wiring Boards. Strictly speaking, printed
boards
are constructed by silk screening conductive paint onto an insulating
substrate.
This is how the first "printed" boards were made during WWII for the
proximity
fuse. Resolution is poor, but they are cheap and don't involve toxic waste
disposal. Especially good if a cheap board is needed for one time use.
On the topic of building 1GHz circuits on a PCB/PWB/EWB/PCA, look at
the article in Circuit Cellar #149, Dec 2002, on page 24: "Vector-SoC". It
describes a winning entry in on of the magazines design contests.
The device is a 1GHz Vector Network Analyzer, built around the
Analog Devices AD8302.
mitvma.mit.edu
