etched pcb biquad

All the biquad designs I've seen use bent wire. Has anyone tried an
etched biquad antenna built on PCB?

Is the issue that a PCB trace is too thin to use an an antenna?

miso@sushi.com wrote:
> All the biquad designs I've seen use bent wire. Has anyone tried an
> etched biquad antenna built on PCB?
>
> Is the issue that a PCB trace is too thin to use an an antenna?

Commercial patch antennas use PCB materials often. Perhaps it easier
for DIYSers to bend and solder wire and etching a circuit board.

On Tue, 21 Nov 2006 22:04:15 GMT, decaturtxcowboy
<nope_none_@nowayspam.com> wrote:

>miso@sushi.com wrote:
>> All the biquad designs I've seen use bent wire. Has anyone tried an
>> etched biquad antenna built on PCB?
>>
>> Is the issue that a PCB trace is too thin to use an an antenna?
>
>Commercial patch antennas use PCB materials often. Perhaps it easier
>for DIYSers to bend and solder wire and etching a circuit board.

Yep. Etched PCB antennas work. However:

The dielectric constant of the PCB material will shrink the antenna by
the square root of the dielectric constant. For example, G10/FR4 has
a dielectric constant of about 5. One wavelength at 2.4GHz is about
12.5cm in free space and about:
12.5 / sqrt(5) = 5.6 cm
The gain of the antenna is reduced very roughly by the same ratio. A
common biquad with an air dielectric has a gain of about 10dBi. The
PCB version on G10 will be about 2.5dB less.

Lots of other complications when you get away from wire antennas and
go to a PCB dielectric version. Tolerance issues, reduced bandwidth
on the smaller antennas, non-symmetrical cross sections make calcs a
bit complex, problems with PCB feeds, coax to PCB interface issues,
surface conductivity (oxidized copper sucks), ad nausium.

In my never humble opinion, if you're going to be building your own
without adequate test equipment (i.e. network analyzer, antenna range,
reference antennas, vswr bridge, etc), then do the wire antennas.
They're much easier. However, if you have some control over
tolerances, a good computer modeling program (4NEC2, EZNEC, etc), and
a pile of test equipment, methinks you could try PCB antennas.

As for the original question: Has anyone tried a PCB biquad? I
dunno. I haven't. PCB material is commonly used as the reflector,
but not the driven elements as in:
http://martybugs.net/wireless/biquad/

Well, I lied. Here's a commercial antenna that's close.
http://802.11junk.com/jeffl/antennas...dBi/index.html
It's a 9dBi Maxrad 2.4GHz antenna. It's NOT a biquad but rather a
mono-quad or just one loop. There's a 12dBi version that has two
loops and I guess would be considered a biquad. The PCB material is
polysulfone with a dielectric constant of 3.1 and quite low loss at
2.4Ghz. Note the weird looking lumps on the trace connecting the loop
with the coax connection. All that is impedance matching which will
need to be done on your do it thyself PCB antenna. This can't be done
without a VSWR bridge or network analyzer.




--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558 jeffl@comix.santa-cruz.ca.us
# http://802.11junk.com jeffl@cruzio.com
# http://www.LearnByDestroying.com AE6KS

On Wed, 22 Nov 2006 00:10:48 GMT, Jeff Liebermann
<jeffl@comix.santa-cruz.ca.us> wrote:

>As for the original question: Has anyone tried a PCB biquad? I
>dunno. I haven't. PCB material is commonly used as the reflector,
>but not the driven elements as in:
> http://martybugs.net/wireless/biquad/

I lied (again). See:
| http://host219.ipowerweb.com/~freene...products_id=91
Click on the green rectangle at the top center of the page. It's a
PCB biquad for $10.



--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558 jeffl@comix.santa-cruz.ca.us
# http://802.11junk.com jeffl@cruzio.com
# http://www.LearnByDestroying.com AE6KS

Jeff Liebermann wrote:
> On Tue, 21 Nov 2006 22:04:15 GMT, decaturtxcowboy
> <nope_none_@nowayspam.com> wrote:
>
> >miso@sushi.com wrote:
> >> All the biquad designs I've seen use bent wire. Has anyone tried an
> >> etched biquad antenna built on PCB?
> >>
> >> Is the issue that a PCB trace is too thin to use an an antenna?
> >
> >Commercial patch antennas use PCB materials often. Perhaps it easier
> >for DIYSers to bend and solder wire and etching a circuit board.
>
> Yep. Etched PCB antennas work. However:
>
> The dielectric constant of the PCB material will shrink the antenna by
> the square root of the dielectric constant. For example, G10/FR4 has
> a dielectric constant of about 5. One wavelength at 2.4GHz is about
> 12.5cm in free space and about:
> 12.5 / sqrt(5) = 5.6 cm
> The gain of the antenna is reduced very roughly by the same ratio. A
> common biquad with an air dielectric has a gain of about 10dBi. The
> PCB version on G10 will be about 2.5dB less.
>
> Lots of other complications when you get away from wire antennas and
> go to a PCB dielectric version. Tolerance issues, reduced bandwidth
> on the smaller antennas, non-symmetrical cross sections make calcs a
> bit complex, problems with PCB feeds, coax to PCB interface issues,
> surface conductivity (oxidized copper sucks), ad nausium.
>
> In my never humble opinion, if you're going to be building your own
> without adequate test equipment (i.e. network analyzer, antenna range,
> reference antennas, vswr bridge, etc), then do the wire antennas.
> They're much easier. However, if you have some control over
> tolerances, a good computer modeling program (4NEC2, EZNEC, etc), and
> a pile of test equipment, methinks you could try PCB antennas.
>
> As for the original question: Has anyone tried a PCB biquad? I
> dunno. I haven't. PCB material is commonly used as the reflector,
> but not the driven elements as in:
> http://martybugs.net/wireless/biquad/
>
> Well, I lied. Here's a commercial antenna that's close.
> http://802.11junk.com/jeffl/antennas...dBi/index.html
> It's a 9dBi Maxrad 2.4GHz antenna. It's NOT a biquad but rather a
> mono-quad or just one loop. There's a 12dBi version that has two
> loops and I guess would be considered a biquad. The PCB material is
> polysulfone with a dielectric constant of 3.1 and quite low loss at
> 2.4Ghz. Note the weird looking lumps on the trace connecting the loop
> with the coax connection. All that is impedance matching which will
> need to be done on your do it thyself PCB antenna. This can't be done
> without a VSWR bridge or network analyzer.
>
>
>
>
> --
> # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
> # 831-336-2558 jeffl@comix.santa-cruz.ca.us
> # http://802.11junk.com jeffl@cruzio.com
> # http://www.LearnByDestroying.com AE6KS

I'm trying to visualize how the pcb material interacts with the copper
track. It's not like you are doing stripline, i.e. metal traces with
the fr4 between the traces. The signal hits the copper from free air.
But a reflector would have the dielectric of the pcb in the path.

miso@sushi.com hath wroth:

>I'm trying to visualize how the pcb material interacts with the copper
>track. It's not like you are doing stripline, i.e. metal traces with
>the fr4 between the traces. The signal hits the copper from free air.
>But a reflector would have the dielectric of the pcb in the path.

Oh, that's easy. A non-radiating transmission line has at least one
ground plane below the trace and is terminated at both ends.
Sometimes, it's sandwitched between two ground planes but must always
be terminated. A radiating trace antenna has no ground planes and is
matched only at only one end by the output impedance of the
transmitter or the input impedance of the receiver. The other end is
matched to the impedance of free space or 377 ohms. Think of an
antenna as an impedance transformer between 50 ohms (or whatever) and
377 ohms.

The easiest way to visualize this by having the dielectric between
between the antenna elements and the reflector be composed of two
different materials, air with e=1.0 and G10 with e=5.0 (approx) with
corresponding variations in thickness. I don't know exactly how to
model such an antenna. I'm also lazy and think it's time you dig out
4NEC2 or other modeling program and try it thyself first.
http://home.ict.nl/~arivoors/
Send me you model and I'll try to untangle it. Use this model:
http://802.11junk.com/jeffl/antennas/Biquad/biquad.nec
as a starting point. You might also find it interesting to look at
the web site where I stole the model:
http://www.pow.za.net
http://www.pow.za.net/panel_2x2commercial.jpg

If you're going to dive into surface radiating patch or panel
antennas, most of the NEC2 surface models are marginal approximations.
Instead, use MSTRIP40:
http://www.e-technik.fh-kiel.de/~splitt/html/mstrip.htm
for something more accurate. Incidentally, there's quite a bit on
strip line and surface radiating calcs in the "lab manual" at:
http://www.e-technik.fh-kiel.de/~spl...0LabManual.pdf
which might explain how to visualize the antenna.


--
Jeff Liebermann jeffl@comix.santa-cruz.ca.us
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

miso@sushi.com hath wroth:

>I'm trying to visualize how the pcb material interacts with the copper
>track. It's not like you are doing stripline, i.e. metal traces with
>the fr4 between the traces. The signal hits the copper from free air.
>But a reflector would have the dielectric of the pcb in the path.

I just had a thought[1]. Many years ago, I designed (actually I threw
together) an antenna using a PCB substrate. I didn't have the fancy
modeling software available, so I did it by cut-n-try, with a pile of
test equipment. I started with just 0.032 G10 PCB material and use
copper tape (from the local stained glass supplier) to create the
antenna elements. Exacto knife adjustments were quite easy. You
could probably prototype something similar. I also made some using
window glass as a substrate. That worked fairly well but was limited
to designs were the coax was fed at the edge of the glass plate as it
couldn't be easily drilled.

[1] It happens, but not very often.

--
Jeff Liebermann jeffl@comix.santa-cruz.ca.us
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann wrote:
> miso@sushi.com hath wroth:
>
> >I'm trying to visualize how the pcb material interacts with the copper
> >track. It's not like you are doing stripline, i.e. metal traces with
> >the fr4 between the traces. The signal hits the copper from free air.
> >But a reflector would have the dielectric of the pcb in the path.
>
> Oh, that's easy. A non-radiating transmission line has at least one
> ground plane below the trace and is terminated at both ends.
> Sometimes, it's sandwitched between two ground planes but must always
> be terminated. A radiating trace antenna has no ground planes and is
> matched only at only one end by the output impedance of the
> transmitter or the input impedance of the receiver. The other end is
> matched to the impedance of free space or 377 ohms. Think of an
> antenna as an impedance transformer between 50 ohms (or whatever) and
> 377 ohms.

I think you are thinking too much, or you didn't get my original
statement. I understand stripline. [I made a high speed controlled
impedance dut board for an ECL DAC I was evaluating.] In the case of
the loop on a PCB, think of the antenna being used as a transmitter.
Then the element radiates in one direction (i.e. forward) without a
dielectric in the path. The reflector does have a dielectric in the
path, but only for a short distance relative to the signal path. So I
just don't see the pcb effecting the dimensions of the antenna.

I have copper tape, though hell if I know where. I think Excess
Solutions in Milpitas sells it. I could make some fiberglass as a
substrate if it is better than using pcb.

Back to the stripline board I designed, I had a HP TDR on loan at the
time. It was a TDR plus oscilloscope. My traces were close to the
target impedance. When I did the math, I came up with really wide
traces based on the spacing between planes. I was glad went truth
matched math. Then I was looking at a test board designed by HP for
their high speed chip tester. The traces were quite small, so I figured
the dielectric thickness was proportionally small. Still, you need the
thickness to be well controlled. As it turns out, the HP traces were
way off. I don't recall which direction (high or low), but I informed
HP of this error. Needless to say, it didn't look good when I showed
their board was no good based on their own instrumentation.

>
> The easiest way to visualize this by having the dielectric between
> between the antenna elements and the reflector be composed of two
> different materials, air with e=1.0 and G10 with e=5.0 (approx) with
> corresponding variations in thickness. I don't know exactly how to
> model such an antenna. I'm also lazy and think it's time you dig out
> 4NEC2 or other modeling program and try it thyself first.
> http://home.ict.nl/~arivoors/
> Send me you model and I'll try to untangle it. Use this model:
> http://802.11junk.com/jeffl/antennas/Biquad/biquad.nec
> as a starting point. You might also find it interesting to look at
> the web site where I stole the model:
> http://www.pow.za.net
> http://www.pow.za.net/panel_2x2commercial.jpg
>
> If you're going to dive into surface radiating patch or panel
> antennas, most of the NEC2 surface models are marginal approximations.
> Instead, use MSTRIP40:
> http://www.e-technik.fh-kiel.de/~splitt/html/mstrip.htm
> for something more accurate. Incidentally, there's quite a bit on
> strip line and surface radiating calcs in the "lab manual" at:
> http://www.e-technik.fh-kiel.de/~spl...0LabManual.pdf
> which might explain how to visualize the antenna.
>
>
> --
> Jeff Liebermann jeffl@comix.santa-cruz.ca.us
> 150 Felker St #D http://www.LearnByDestroying.com
> Santa Cruz CA 95060 http://802.11junk.com
> Skype: JeffLiebermann AE6KS 831-336-2558