[SI-LIST] Re: :PCB Trace Antenna

I hava a similar issue (sort of).  I have a printed
antenna made by an engg. who doesn't work with as
anymore.  I am trying to measure the inductance of
this antenna (dipole antenna not loop). This antenna
is on a thin laminate. I am using a VNA to get the
S11.  Now the problem is depending on how and on what
material i place the antenna i get very different S11
readings.  I have removed the tuning capacitor.  
Question 1: Is this the right way to measure the
inductance of an antenna? or is there a better way to
do it?
Question 2: Should the dielectric underneath the
antenna affect the inductance readings?

as always, thanks in advance for your suggestions.

regards,

Virendra

--- Istvan Novak <istvan.novak@xxxxxxx> wrote:

> Boopathy,
> 
> if my memory serves me correctly, around 1uH
> inductance
> can be achieved with a single turn of about 0.6
> meters in 
> diameter.  For your application this clearly
> suggests multiple
> turns.  So you probably need to place the turns
> along the
> perimeter of the card, to make the loop as big as
> possible. 
> The number of turns can be determined as soon as you
> know
>  the inductance of a single turn: you can look it up
> in text books.
>  If you dont have one handy, do a Google search on
> inductance
> of circular or rectangular loops.  The specified
> inductance gives
> you the tuning capacitance you need to put in
> parallel, and the
> 50-ohm termination will set your Q, so you have
> those all set
>  for you.  Looking at recommended placements and
> layouts as
> Andrew suggested, would be helpful.
> 
> Regards,
> Istvan
> 
> Boopathy J. wrote:
> 
> >Dear Istvan,
> >   I need to Create an PCB trace antenna of 
> >F=13.5Mhz, Impedence=50 ohms, L=1.2uH.
> >
> >Now I need to determine PCB trace length (end to
> end), width of the trace
> >etc. Is there is any calculator available to
> determine it?.
> >
> >Right Now we have a plan to complete the placement
> & routing of the board
> >which will lie inside the loop antenna. Is it a
> right design to do it?? 
> >
> >Otherwise, I need to Make two separate PCB (one for
> component & another one
> >for loop antenna). 
> >
> >Regards,
> >Boopathy J
> >
> >
> >-----Original Message-----
> >From: Istvan Novak [mailto:istvan.novak@xxxxxxx] 
> >Sent: Thursday, September 22, 2005 5:19 PM
> >To: Boopathy J.
> >Cc: si-list@xxxxxxxxxxxxx
> >Subject: Re: [SI-LIST] PCB Trace Antenna
> >
> >Boopathy,
> >
> >Not knowing the RF system parameters you have 
> >to achieve, just based on the stated frequency, 
> >you probably want to create a tuned loop antenna.  
> >In this case the trace impedance matters less, 
> >in fact you may want to increase it as much 
> >as possible. More will matter the size 
> >(and orientation) of loop and the number of turns.
> >
> >
> >regards,
> >
> >Istvan novak
> >SUN Microsystems
> >
> >Boopathy J. wrote:
> >
> >  
> >
> >>Content-Type: text/plain;
> >>    charset="us-ascii"
> >>Content-Transfer-Encoding: quoted-printable
> >>HI,
> >>
> >>We are designing HF card Reader  at f =13.56MHZ.
> >>
> >>we need to implement the Antenna In PCB  traces.
> As I haven't worked =
> >>much on
> >>
> >>RF PCB design, I would like to know how to
> implement it &
> >>
> >>how to determine the Trace length & impudence for
> 13.56MHz.
> >>
> >>=20
> >>
> >>=20
> >>
> >>Thanks In advance
> >>
> >>=20
> >>
> >>Regards,
> >>
> >>Boopathy J
> >>
> >>=20
> >>
> >>
> >>    
> >>
> 
>
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