need help about microstrip line antenna

[riyadhe]

hello all i'm newbie in this forum....
I'm working on final project on microstrip antennas. I ask for help to design microstrip line antenna with a frequency of 144 MHz. I simulate this task using HFSS 11. is there anything that can help me design this antenna?
and my little experience difficulties regarding electrical length, how to calculate and apply it to the HFSS 11. and I'm sorry about my english a bit messy... :-D
substrate = fr_04

 

[ferdows]

hi
i think u antenna became to bulky and hard to print

 

[riyadhe]

why become hard to print?
how about design this antenna on patch like rectangular patch and add slot like U or H slot?

 

[embeddedlover]

I shall explain you with an example,.....

Consider a microstrip antenna patch around ISM band your lengthxwidth will be ~30x30mm...
As frequency decreases, your patch dimensions increases and imagine your dimensions for 144MHz....

A simple whip antenna will be enough in your frequency range...

 

[riyadhe]

yes it is...
i can imagine how large this antenna,..
but if i add two substrate, substrate from FR-04 it self and extra substrate like mica or foam,does it can be designed?
sorry if i ask to much coz i newbie in antenna design...

 

[ferdows]

hi
its possible to bond two or more substrate but bonding is hard
and when i say print i mean printed circuit antenna
why u want microstrip when u can design more easier antenna with more bandwidth ?

 

[riyadhe]

in affect my final project is about design dualband microstrip antenna at 144Mhz/430 MHz , for ground station nano satellite. but firstly i want design one by one this antenna.
i decide use microstrip coz from my lecture want it,.
do have any advise else for my design?

 

[Thunyawat]

in affect my final project is about design dualband microstrip antenna at 144Mhz/430 MHz , for ground station nano satellite. but firstly i want design one by one this antenna.
i decide use microstrip coz from my lecture want it,.
do have any advise else for my design?

How about trying first mode rectangular squre patch, \lambda /2\times \lambda /2

 

[ferdows]

hi
do u have limitation about the substrate material?

 

[ferdows]

hi
see this paper it may be useful but i suggest u ,dont use microstrip

 

[riyadhe]

How about trying first mode rectangular squre patch, \lambda /2\times \lambda /2

i have tried this one,but for freq 144Mhz has large size and my design must be less than 50 x 40 cm. but my UHF (430Mhz) has small size and has size less than 50x40 cm.and I am having trouble how to make dual band microstrip antenna with dimensions specification.

hi
do u have limitation about the substrate material?

i don't have, but the material of the substrate is not too expensive

hi
see this paper it may be useful but i suggest u ,dont use microstrip

yes i has read this paper,but why pict of design doesn't appear? but this paper use full for my reference

 

[ferdows]

hi
i design an antenna with size 220*450mm and attach its S11 for u

 

[riyadhe]

hi
i design an antenna with size 220*450mm and attach its S11 for u

could u send me your design? @riyadh.elits@gmail.com

coz i'm still confuse about my dualband design, i still learns how to unite my design. thax.....

 

[ferdows]

hi
i will send it for i simulated with hfss 11 i hope it useful for u

 

[WimRFP]

Hello,

in affect my final project is about design dualband microstrip antenna at 144Mhz/430 MHz , for ground station nano satellite. but firstly i want design one by one this antenna.
i decide use microstrip coz from my lecture want it,.
do have any advise else for my design?

Do you need linear or circular polarisation? What radiation pattern do you want?

If linear, you can use "meandering" or "meander line" to reduce the physical length. Don't try to make this antenna on FR4 (with ground under it). The distance between the patch element and ground will be too small to get reasonable antenna efficiency. Meandering can be used for circular polarisation also, but you require more space and seperate feeds to create good circularity

You can make the antenna on FR4 PCB, but the PCB (single layer) should be elevated, so there will be lots of air between the PCB and the ground plane. Of course you can use rigid foam between the bottom side of the PCB and the metal ground plane for rigidity.

Other thing is you can make a structure that has good S11 at both 144 and 430 MHz, but this does not mean you have the correct radiation pattern for the 430 MHz part.

Some people use PIFA to reduce the size w.r.t. a regular patch (half wave resonating structure). However, the vertical part of the PIFA does change the radiation pattern significantly.

 

[riyadhe]

hi
i will send it for i simulated with hfss 11 i hope it useful for u

yes thax u,i've got yours... it's very use full for my final project.... but may i ask again?? if i change the "feed" method to coax-probe, any suggestion where i should put this probe?

Hello,



Do you need linear or circular polarisation? What radiation pattern do you want?

If linear, you can use "meandering" or "meander line" to reduce the physical length. Don't try to make this antenna on FR4 (with ground under it). The distance between the patch element and ground will be too small to get reasonable antenna efficiency. Meandering can be used for circular polarisation also, but you require more space and seperate feeds to create good circularity

You can make the antenna on FR4 PCB, but the PCB (single layer) should be elevated, so there will be lots of air between the PCB and the ground plane. Of course you can use rigid foam between the bottom side of the PCB and the metal ground plane for rigidity.

Other thing is you can make a structure that has good S11 at both 144 and 430 MHz, but this does not mean you have the correct radiation pattern for the 430 MHz part.

Some people use PIFA to reduce the size w.r.t. a regular patch (half wave resonating structure). However, the vertical part of the PIFA does change the radiation pattern significantly.

i need circular pol, but i have to use FR04 coz PCB like duroid difficult to find in my country.,.
PIFA it's quite possible but i still learns about coax-probe feed... d you have any reference to use PIFA for VHF and UHF antenna at my freq range? thax before....

 

[WimRFP]

Hello,

PIFA gives other radiation pattern, so check whether this is accaptable. A half wave resonating patch with mostly air as dielectric has its main lobe in Z direction (when ground plane is in XY plane).

It is no problem to use FR4, as long as there is sufficient air between the PCB and the groundplane (so there is no ground plane on the PCB)

You can make a circular antenna with only one probe feed, but you may consider two orthogonal feeds that you derive from a (wilkinson) divider with a 90 degrees phase shift in one of the paths. The divider you can make on FR4 that is directly on the ground plane. From that PCB you can go vertically upwards to the radiating resonator (that is elevated).

Regarding dual-band. I would go for two seperate antennas in one case where you use some filtering to seperate (diplex filter function) 430 from 144 MHz. This enables you to design the antennas without significant interaction between the 430 and 144 MHz antenna.

Do you need to cover the full amateur bands (144..146, 430-440 MHz) or just a part. If you just need a single frequency in each band, the antenna can be small, but production tolerance becomes more important.

I would recommend you to discuss the options with you teacher.

 

[riyadhe]

Hello,

PIFA gives other radiation pattern, so check whether this is accaptable. A half wave resonating patch with mostly air as dielectric has its main lobe in Z direction (when ground plane is in XY plane).

It is no problem to use FR4, as long as there is sufficient air between the PCB and the groundplane (so there is no ground plane on the PCB)

You can make a circular antenna with only one probe feed, but you may consider two orthogonal feeds that you derive from a (wilkinson) divider with a 90 degrees phase shift in one of the paths. The divider you can make on FR4 that is directly on the ground plane. From that PCB you can go vertically upwards to the radiating resonator (that is elevated).

Regarding dual-band. I would go for two seperate antennas in one case where you use some filtering to seperate (diplex filter function) 430 from 144 MHz. This enables you to design the antennas without significant interaction between the 430 and 144 MHz antenna.

Do you need to cover the full amateur bands (144..146, 430-440 MHz) or just a part. If you just need a single frequency in each band, the antenna can be small, but production tolerance becomes more important.

I would recommend you to discuss the options with you teacher.

nice advise,.. but i've decided chose rectangular patch for my design. i've being tried simulating this design but i find difficult to resize antenna into smaller size. but from this forum i got a lot of reference for my design... hmmm,. diplex filter? did u mean duplex filter on microstrip? so it's additionally device,isn't it?

i think my design for single freq not wide band, but i'm not sure about that. your last advise i think right, i should discuss with my lecture....
but how can be smaller if i chose single freq? thax n i'm sorry for my English if a bit messy...

 

[ferdows]

hi riyadhe
i could reduce the frequencies of patch which i send u before many technique can be use for miniaturization of microstrip antenna

 

[WimRFP]

hi riyadhe
i could reduce the frequencies of patch which i send u before many technique can be use for miniaturization of microstrip antenna

He decided to go for rectangular and has no access to (large volume) of good dielectric, so with this in mind he has limited or no options to reduce the size of the patch.

To get reasonable antenna efficiency he can only use air (or foam) as dielectric. So he can only reduce the resonant frequency (given certain size) by cutting into the rectangular patch and/or adding vertical sections to increase the capacitance to ground (of the edges of the patch).

Riyadhe: A standard patch antenna you can see as a transmission line with a half wave electrical length. Due to radiation there are losses in that line. If you know the voltage and current distribution of the standing wave pattern (similar to that of a half wave dipole), you may know that if you move the feed to one end, the impedance at resonance increases.

There is some induction in the vertical part of the probe feed, this results in a difference in the free resonant frequency of the patch and "measured" resonant frequency. If you like, you can counteract that inductance with a series capacitor. That capacitor can be a small patch at the bottom side of the FR4, or a small isolated patch in your large patch. both techniques are used in many wide band patch antenna designs with air as dielectric.

The Wilkinson divider (and if required the diplexer), you can make on a separate PCB that is at the ground plane below the radiating patch. What is the maximum thickness of the complete antenna structure?

I assume your antenna will look at the sky (so received noise is low). To get the most out of it (in combination with a good LNA), you should optimize for good radiation efficiency as the losses in the antenna are at ambient temperature and will add thermal noise.

You may try "Compact & Broadband Microstrip Antennas" (Wong) to get design ideas.