antenna 100 mhz
I need an pcb-antenna at 100MHz.
I did chose a meander-like structure on substrate FR4 (e=4.7)
without ground plane.
Three versions:
1.) meander leg = 32mm, strip width/spacing= 1.4mm
substrate size 46x52mm
2.) meander leg =20mm, strip width/spacing 1mm
substrate size 33x38mm
3.) meander leg = 10mm, strip width/sp. 0.5mm
substrate size 16x20mm
Simulations show inductive impedance (as it was expected)
then i have applied a capacitor (assume smd) with corresponding value of "few" pF
I got desired characteristics for all three constructions.
Varriation of L and C gave me S11 = from -24 dB (1.4mm) down to -35 dB (0.5mm)
Pattern is of non-directive "circle-like" antenna with Gain of 0 dB, Directive Gain of 6 dB.
Everything is nice in theory. Now i'm thinking on practical output...
What do you think?
Hello,
I don't exactly understand the setup. If there is no ground plane and the antenna is apparently a monopole, how do you calculate an input impedance respectively s11? Cause it's a "short" antenna, it must have a very low radiation impedance, also probably bad matching and relative high losses.
Regards,
Frank
What kind of simulations?..HFSS?.....
could you show the layout?...
it is a loop of series connected meander and capacitor, with two 5Oohm ports
simulation done by Sonnet
such (like BPFilter) structure shows simulated good matching and low losses
Added after 3 minutes:
it is a loop of series connected meander and capacitor, with two 5Oohm ports
simulation done by Sonnet
such (like BPFilter) structure shows simulated good matching and low losses
I agree with FvM, for 100 MHz the wavelength
is 3 meters. An antenna of only 32 mm,
or even 52 mm(max size) is a "electrically
small antenna".
Can be made resonant and that maybe the
reason for a s11= -24 dB but
the efficiency is small(low radiation resistance).
And what, how it is possible to improve it?
I plan to use lna after it...
You got from simulation a gain of 0dB?
I think this is a joke.
This very small antenna (a hundred times smaller than wavelength), in reality probably have a gain lower than -10dB.
tomorrow can show pattern,
it is something like very good BP Filter with S11= -25 -35 dB
Losses in the band are 0db, matching is very good, it does Gain = 0dB
why it is a joke?
Hello,
could it be, that you designed actually a two-port bandpass rather than an antenna?
Regards.
Frank
I concur with the -10 dBi gain, or much lower, estimate. Actually, -10 dBi is probably really generous and you will probably find much less if you were to build and test this loop. s11 as low as you cite may be a consequence of lots of insertion loss. The antenna is electrically small.
is not antenna some special type of bandpass?
or why such bandpass cannot operate as reception antenna?
what is the difference?
it is matched, pattern is circular, gain is 0dB...
plz advice
Added after 9 minutes:
It is not true:
I have got 0dB Gain, and 6dB Directive Gain with typocal indirective pattern,
with Phi = 0o and 90o.
S11 has losses only in desired band: it means S11 =-25dB at 100MHz( -20dB in the band of 80 to 120 MHz), It means that Return losses are very low.
S11 characteristic is similar to good Band Pass Filter
S21 ~ 0 dB at 100MHz in the band of 80 to 120 MHz
NOTE Antenna has not ground plane!
Show pattern and layout.........
specially layout.
Hello,
if it's an antenna, transmission would be measured between a port at the antenna and a distant reference antenna port, or a special simulation means e. g. a Huygens surface. Transmission characteristic probably is some kind of bandpass, but a "wireless bandpass".
Regards,
Frank
pattern and layout and S11/S21
I have sent pattern, layout and S11/S21 as attached pictures
Can you see them?
Added after 53 minutes:
I have sent pattern, layout and S11/S21 as attached pictures
Can you see them?
Added after 18 minutes:
I have sent pattern, layout and S11/S21 as attached pictures
Can you see them?
Added after 46 seconds:
I have sent pattern, layout and S11/S21 as attached pictures
Can you see them?
Hello,
what's connected to the other contact of the ports? An infinite conductive surface?
What was the "receiver" with the radiation pattern. What does 0 dB reference mean here?
Is the transmission measurement between port 1 and 2?
Regards,
Frank
1.) i think it is the transmission measurement between port 1 and 2
2.) there are just two 50 Ohm ports
3) Pattern: is Far Field Pattern (FFP)
In the field of antenna design the term radiation pattern most commonly refers to the directional (angular) dependence of radiation from the antenna or other source (synonyms: antenna pattern, far-field pattern).
The sonnet far field pattern viewer calculates the FFP of the structure from analyzed current density and displays the antenna gain in 2D Cartesian or Polar (actual picture) format. If we chooese display Gain (power gain) the radiated power is normalized to the input power. Metallic and dielectric losses are taken
into account. Gain is smaller than Directive gain (or directivity)
0 dB means here that there are now attenuation or amplificaton of input power
4) simulated Zin = 55 Ohm at 100MHz, and >> 50Ohm out off band
Hello,
a port can't generate any current without connecting both sides, I think. At best, it could intersect a symmetrie boundary, if the full design would include a mirror of the shown structure.
I understand, that you have generated the radiation pattern by a simulation tool that measures far field. I don't know how it's operating in the particular software, but should be generally correct.
I don't understand, how can radiated power and s21 between port1 and 2 be both ≈ 0 dB at center frequency? The input power can either be radiated or transmitted to the other port.
I still guess, most of input power isn't radiated because of the small dimension. Thus the "wired" s21 is realistic, but the "wireless" power gain isn't.
Regards,
Frank
sorry, radiated power is not 0 dB,
Gain is 0 dB
Gain = output power/input power,
("/" - means division here)
i'm not sure yet
Yes, should write power gain. Issue is the same.