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Ceramic 2.4GHz antenna

P

PeteS

Jan 1, 1970
0
I'm in the market for a 2.4GHz ceramic antenna (I've decided on that for
a number of reasons).

A number of companies do these: do you guys have any experience or
preference with these parts / companies?

Obviously, availability is an issue, but so are specs - any help /
pointers to reliable companies appreciated.

FWIW, I am in the UK. Estimated usage of this part is >50k / year.

Cheers

PeteS
 
P

PeteS

Jan 1, 1970
0
PeteS said:
I'm in the market for a 2.4GHz ceramic antenna (I've decided on that for
a number of reasons).

A number of companies do these: do you guys have any experience or
preference with these parts / companies?

Obviously, availability is an issue, but so are specs - any help /
pointers to reliable companies appreciated.

FWIW, I am in the UK. Estimated usage of this part is >50k / year.

Cheers

PeteS

If you are a vendor and you spam my email address you will definitely
_not_ be getting my business. You are free to state your parts here, but
I'll expect you to back it up with samples and information.

Cheers

PeteS
 
R

Rene Tschaggelar

Jan 1, 1970
0
PeteS said:
I'm in the market for a 2.4GHz ceramic antenna (I've decided on that for
a number of reasons).

A number of companies do these: do you guys have any experience or
preference with these parts / companies?

Obviously, availability is an issue, but so are specs - any help /
pointers to reliable companies appreciated.

FWIW, I am in the UK. Estimated usage of this part is >50k / year.


I'm in the business of calculating such stuff.
What kind of characteristic in terms of
directionality, gain and bandwidth do you need ?
Then a bit closer to pricing : if you have a cable
in between, the cable is 50 ohms, but if you
have it close to the electronics, you might
have a different impedance in mind.

Rene
 
P

PeteS

Jan 1, 1970
0
Rene said:
I'm in the business of calculating such stuff.
What kind of characteristic in terms of
directionality, gain and bandwidth do you need ?
Then a bit closer to pricing : if you have a cable
in between, the cable is 50 ohms, but if you
have it close to the electronics, you might
have a different impedance in mind.

Rene

In this application, I will be feeding the antenna on an impedance
controlled track of no more than 2 inches length, 50 ohm. If you are
interested, this is for a 802.11b/g unit I am integrating into the
latest and greatest.

I can deal with the usual issues. One thing is there will be a huge
ground plane (LCD display) about 12 mm away. I have the time to do
experiments with tuning components.

Bandwidth: I would prefer the antenna not to splatter beyond the ISM
band (let's say 15dB attenuation out of band minimum)

Gain: I can live with 0-3dBi

Directionality: I would prefer a dual polarised device. This is a
handheld unit and it can be (obviously) held at a number of angles.

Cheers

PeteS
 
P

PeteS

Jan 1, 1970
0
Rene said:
I'm in the business of calculating such stuff.
What kind of characteristic in terms of
directionality, gain and bandwidth do you need ?
Then a bit closer to pricing : if you have a cable
in between, the cable is 50 ohms, but if you
have it close to the electronics, you might
have a different impedance in mind.

Rene

Hi Rene

I might have an interest in that cable tester you host on your site. Can
you send me (or have them send me) information on pricing / availability
for just a couple of units?

Cheers

PeteS
 
My experience with 2.45GHz ceramic antennas is that once they are in
a real environment the performance bears little resemblance to
anything found in the datasheet. Very good results can be obtained
with pcb antennas, but they do need a little more space.
(They don't need to be PIFAs - 1/4 wave monopoles adjacent to a
ground plane can work very nicely.)

In a small device you won't get much directionality,
whether you want it or not.

John
 
R

Robert Baer

Jan 1, 1970
0
Rene said:
I'm in the business of calculating such stuff.
What kind of characteristic in terms of
directionality, gain and bandwidth do you need ?
Then a bit closer to pricing : if you have a cable
in between, the cable is 50 ohms, but if you
have it close to the electronics, you might
have a different impedance in mind.

Rene
Dumb question: why 50 ohms and not 75 ohms?
 
R

Rene Tschaggelar

Jan 1, 1970
0
Robert said:
Dumb question: why 50 ohms and not 75 ohms?

75 Ohms is a speciality of the TV world. Having a higher
impedance means less ohmic losses on kilometers of cheap
cable.

Rene
 
P

PeteS

Jan 1, 1970
0
Robert said:
Dumb question: why 50 ohms and not 75 ohms?

The impedance of the chipset I am using is 50 ohms (bog standard RF),
and the simplest method is a direct connection (well, through a small
cap anyway). I will no doubt end up with a couple of tuning components,
but that's simple compared to a full impedance transform.

:)

Cheers

PeteS
 
B

Baron

Jan 1, 1970
0
PeteS said:
In this application, I will be feeding the antenna on an impedance
controlled track of no more than 2 inches length, 50 ohm. If you are
interested, this is for a 802.11b/g unit I am integrating into the
latest and greatest.

If you have 2 inches to spare, you are very close to a quarter wave
anyway !
 
H

Hal Murray

Jan 1, 1970
0
75 Ohms is a speciality of the TV world. Having a higher
impedance means less ohmic losses on kilometers of cheap
cable.

Isn't that backwards?

I thought higher impedance meant smaller dia center conductors
and hence higher losses. (I use the tiny center conductors
in scope probe cables to remember the sign bit.)

I'm pretty sure the old coax Ethernet used 50 ohms rather than 75
because it had lower losses.
 
L

Lostgallifreyan

Jan 1, 1970
0
[email protected] (Hal Murray) wrote in
Isn't that backwards?

I thought higher impedance meant smaller dia center conductors
and hence higher losses. (I use the tiny center conductors
in scope probe cables to remember the sign bit.)

I'm pretty sure the old coax Ethernet used 50 ohms rather than 75
because it had lower losses.

Impedance is defined by the spacing made by the dielectric though, not by
the conductor size. In TV coax the solid core is usually thicker than the
total of the stranded cores in thinner 50 ohm lines. I don't know how much
the 'skin effect' matters at sub-1GHz frequencies though. Anyway, I don't
think that the relation between loss and impedance is fixed, it will depend
on capacitance, and also at really high frequencies, on the surface area of
a given length of conductor, because that's where the signals is, with this
'skin effect' that no doubt I know not nearly enough about.
 
J

jasen

Jan 1, 1970
0
Isn't that backwards?

I thought higher impedance meant smaller dia center conductors
and hence higher losses. (I use the tiny center conductors
in scope probe cables to remember the sign bit.)

I'm pretty sure the old coax Ethernet used 50 ohms rather than 75
because it had lower losses.

characteristic impedane is not solely due to the size of the conductors.

overall dimensions of the cable and the electrical properties of the dielectric
play the largest part.

Bye.
Jasen
 
R

Robert Baer

Jan 1, 1970
0
Rene said:
75 Ohms is a speciality of the TV world. Having a higher
impedance means less ohmic losses on kilometers of cheap
cable.

Rene
...and has nothing to do with free-space impedance of (about) 300 ohms?
 
R

Rene Tschaggelar

Jan 1, 1970
0
Hal said:
Isn't that backwards?

I thought higher impedance meant smaller dia center conductors
and hence higher losses. (I use the tiny center conductors
in scope probe cables to remember the sign bit.)

I'm pretty sure the old coax Ethernet used 50 ohms rather than 75
because it had lower losses.

For a fixed power, the current scales as sqrt(P/R),
meaning with a higher impedance you indeed need
less copper. The dielectric is specified for almost
a kilovolt, perhaps even more.
For the usual RF guy, the cost of a cable is not
an issue, everything else costs far more. Not so
the TV companies. Their investment are the cables.

Rene
 
D

Didi

Jan 1, 1970
0
Pete,
The impedance of the chipset I am using ...

which chipset are you using? I am in the process of NDA-ing (Marvell)
so I can
get some data to do probably the same which you are doing, so I wonder
(if you would/could discolse that, that is, privately or publically
:).

All, I also wonder what the impact of a metal case would be on such an
antenna - one of the options I have is a metal (0.5mm thick brass)
case,
largish handheld size (with an opening for the TFT etc.).

Dimiter
 
A

atec77

Jan 1, 1970
0
Rene said:
For a fixed power, the current scales as sqrt(P/R),
meaning with a higher impedance you indeed need
less copper. The dielectric is specified for almost
a kilovolt, perhaps even more.
For the usual RF guy, the cost of a cable is not
an issue, everything else costs far more. Not so
the TV companies. Their investment are the cables.

Rene
Telly antennas generally use a folded dipole / semi log period array ,
being frequency unrelated a single folded dipole presents an impedance
of 300 OHMS at resonance and the 4:1 balun reduces this to 75 OHMS which
is why RG59 au is normally used ( or RG6)
The reason for 50 OHM cable being used is most transistor circuits are
built with a 50 OHM impedance because of several factor some of which
are convenience and available baluns
Hence the antenna being built for 50 OHM at resonance .
 
M

Michael A. Terrell

Jan 1, 1970
0
Hal said:
Isn't that backwards?

I thought higher impedance meant smaller dia center conductors
and hence higher losses. (I use the tiny center conductors
in scope probe cables to remember the sign bit.)

I'm pretty sure the old coax Ethernet used 50 ohms rather than 75
because it had lower losses.


IBM used RG-62, 93 ohm coax for their terminals for decades.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
 
J

Jan Panteltje

Jan 1, 1970
0
IBM used RG-62, 93 ohm coax for their terminals for decades.

They also invented OS/2, and MCA (microchannel bus) ;-)
 
L

Lostgallifreyan

Jan 1, 1970
0
They also invented OS/2, and MCA (microchannel bus) ;-)

And the so-called Deathstar drives. In which case, the obituaries are
fortunately premature. They never let me down. I never had the known bad
ones though.
 
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