collection powers
thx!
Hi, Wusen: I think a related question is, given a fixed volume, how big the gain can be for an antenna fitting into the volume. Basically, for your planewave excitation, how much energy the antenna can receive is related to its RCS which is related to the maximum gain of the antenna.
From what I see, an antenna in a fixed volume should have an upper limit on the gain. However, I am not quite sure how big it is. Regards.
Hi,Jian. thank you very much for your reply.
Now, if the plane wave excitation is modified as below: S plane waves which incidence angle uniformly distributed in the solid angle of 4pi. Each plane waves have the same variance, while the polarization and phase are random. For each plane wave the orhogonal polarizations are uncorrelated and the plane waves separated in angle are also uncorrelted.
do you think it should have a upper limit and it is a subject desired to analysis?
btw, if two antennas are connected by a coupled loading network, such as the conjugate matching network (Lee,"mutual coupling effect on maximum-radio diversity combiners and application to mobile radio", trans on comm. 1970), while it is excitated by a plane wave, how to calculte the absobteded power of this loading network in IE3D? It is equivalent to solve matrix equation V=(Z+ZL)I, while the ZL is no longer a diagonal matrix.
I think you are mixing two concepts here:
1)If the antennas are separated enough so the signals can be
uncorrelated then you can use combiners or so to increase the
probabilidad of good reception. Eventhough they are connected
the set is not considered an "array", even if they can be analyzed
as an array. They are considered two differents antennas.
2) But, if the antennas are close enough as in an array the amount
of energy that can be coupled depends on the "effective area" which
depends on the gain of the array. The phase supposed to varies but
is correlated.
Granted, if the size of the array is big enough so in the perifery of it
the signals are uncorrelated then you have a mixed situation and that I
would say that is a good matter for analysis.
I don't know about IE3D, but if you can model the antenna iluminated
by two or more sources so they can be considered uncorrelated then
the model is valid.
Hi,jallem:
my question is abstracted from the multiple antenna wireless communications (MIMO). each antenna requires another radio-frequency (RF) front-end chain and DSP module. So, it isnot the concept of arry, although they may be close each other.
i had once used ideal dipole as antenna element, building the matrix equation to find the current distribution among each dipoles, but there are no idea to calculate the self impedance of the ideal dipole. if using real antenna, there are too many independent variables to be considered.
Hi, Wusen: I am not sure exactly what you want. However, on IE3D, you have the options to do the following: You can model one antenna (may be multiple coupled antennas) and assume planewave excitaiton simultanouesly. Then, you can define it is planewave excitation while you can define lumped elements at the each individual port. IE3D will be able to calculate the absorbed power at each individial port for you. It seems to me this might be what you want. Regards.
The obvious answer (IMHO :D) has nothing to do with the volume of the receiving antenna, but simply the effective aperture of the antenna in the direction of the plane wave, which would be G = 4ΠA/λ2, where A is the aperture area projected in the direction of the plane wave.
(In other words, the amount of rain a bucket will catch has nothing to do with its depth...but everything to do with the diameter of its opening.)
The maximum received power is then determined by the product of the aperture area and the power flux density (W/m2). To get PFD from V/m...use V2/Zo, where Zo is the free space impedance of 377 Ω.
Cheers,
eckypting
I think eckypting's answer should be true. The maximum power can be received should be the power density times the effective area.
I looked in the Antenna book from Stuzman/Thiele(section 3.6.1, pp.122 - 125),
there are two examples for mutual coupling between dipoles. I still dont know
if that is what you want and if I3Ed can give you the impedance. I use HFSS once
for the design of a yagi antenna and HFSS can calculate self impedance and mutual
impedance(a little tricky)
Hi, Jallem: I think Wusen is more interested in the receiving power of an antenna from another far antenna. He is no talking about close coupling of two antennas. For multiple close antennas, IE3D can find the mutual coupling easily. The mutual coupling between close antennas will affect the input impedance. For Wusen's case, I think he considers the Tx antenna is significantly away. It is creating some wave and this wave is received by the Tx antenna. For this case, the induced current on the Rx antenna will not affect the Tx antenna. When the Rx antenna is in the far field zone of the Tx antenna, should the maximum power can be received be the intercepting area times the far field power density of the Tx antenna? It looks like correct. However, I still have some doubt on it. For example, it is supposed the effective area of a thick dipole will be much bigger than that of a thin dipole. However, will the thick dipole receive much lower power than the thin dipole when both of them are at resonance? I think you can use IE3D to check it.
Added after 36 minutes:
Hi, Wusen:
I just tried to simulate 2 cases on IE3D.
(A) A strip dipole with L = 144 mm W = 1 mm resonanting at 1 GHz with Zin = 72.6 ohms. The area of the dipole is AREA=1.44e-4 m*m.
(B) A strip dipole with L = 136 mm W = 10 mm resonating at 1 GHz with Zin = 70 ohms. The area of the dipole is AREA = 1.36e-3 m*m
I tried to illuminate the antenna using a planewave of E= 1 V/m on the two antennas. The power density is about 1.326 mW/(m*m). I put the matching Z for the loads. Interestingly, I can ge teh following result for the received power:
(A) PowerDensity*AREA = 1.910e-7 W while the P_received = 1.554e-5 W.
(B) PowerDensity*AREA = 1.804e-6 W while the P_received = 1.547e-5 W.
Apparently, the received power can be much bigger than the PowerDensity*AREA. I think we should replase the AREA as the EFFECTIVE_AREA or a quantity related to RCS for it. In some sense, the EFFECTIVE_AREA can be much bigger than the physical area of the antenna. However, I do strongly believe there is a limit for the EFFECTIVE_AREA when the size of the antenna is given. Hope this help. Thanks!
Hi,jian: You are right, the effective-area is a function of (theta, phi) (collin 1985), so it would larger than the physical area in some special incident angle.
The coupled loading network means the terminal current in antenna A will affect the load values in antenna B. Can it model this case in IE3D?
Hi jallem: thank you for advice. There are usually two methods to calculate the self impedance: EMF and MoM. However, it seems that when the size of the antenna becomes infinite small, the imaginary part of self impedance become unsolvable.
Hi, Wusen: I think IE3D can solve it. Regards.