147 Threads found on edaboard.com: Near Far
Hello. I'm a new on this forum. I would like to show my last project. This is a device 3 in 1: bikecomputer + flashlight + powerbank
1. Supply from two Li-Ion Cells 18650 Robiton 3400 mAh each
2. Embedded battery charger
3. Two bulbs. One has 10deg lens for far distance light. Other has 30deg lens for near distance light. Each bulb
Show your DIY :: 06-20-2016 07:28 :: mars2860 :: Replies: 0 :: Views: 713
as far as the 90 degree ends of the slots in the Comsol example. I would guess the total length of the slot, including the two tabs at the end, is approximately half wavelength, so that it resonates. Then the two 90 degree tabs are coupling energy from the waveguide (near those top edges of the waveguide are maximum current flow points).
RF, Microwave, Antennas and Optics :: 01-12-2016 10:19 :: biff44 :: Replies: 5 :: Views: 856
The quoted equation is only valid in far field, 2 m is clearly near field. That's at least one possible explanation for deviation.
For a more exact caluculation of transmission in near field, refer to antenna theory text books, e.g. Balanis.
RF, Microwave, Antennas and Optics :: 10-14-2015 17:22 :: FvM :: Replies: 4 :: Views: 565
What is your wavelength? In my experience a good absorber functions equally well in far or near field.
Electromagnetic Design and Simulation :: 10-01-2015 08:18 :: jiripolivka :: Replies: 1 :: Views: 281
As far as the pole lies near a zero it will cancel out the effect of that pole.. it is correct.
So i think it will cancel out one pole which is nearer to the Zero.
Analog Circuit Design :: 08-28-2015 07:03 :: kenambo :: Replies: 2 :: Views: 504
To achieve 0.3 mm trace width for 50 ohms on FR4, the substrate height must be about 180 ?m. Is it so?
More usually, the feasible line width is far below that required for 50 ohms. So it's unavoidable to reduce tracks near a QFN pin. Consider that the bond wire inside the IC package neither continuous 50 ohms impedance.
Traces shorter than
PCB Routing Schematic Layout software and Simulation :: 04-17-2015 07:11 :: FvM :: Replies: 8 :: Views: 787
It depends on your specifications !
Is it white smoke or black smoke or invisible smoke ?
Is this for alarm purposes or process control?
is it far from camera?
What is between and behind cam?
IR is best source for detecting smoke optically, but does cam have IR blocking filter?
Do you want to measure smoke near ground? or high up?
Is this for i
Microcontrollers :: 04-10-2015 14:09 :: SunnySkyguy :: Replies: 7 :: Views: 531
I had simulated micro patch antenna for 2.4 ghz and I can find s11 but please explain procedures to find other results like far feild radiation, near feild,efficiency,gain,directivity and all parameters
RF, Microwave, Antennas and Optics :: 03-25-2015 14:58 :: nesan :: Replies: 0 :: Views: 267
I fear your latest posts are further confusing your intentions.
In terms of RF engineering, an antenna is a device with non-zero coupling to far-field. Inductive couplers are designed to receive or generate a magnetic near-field. They are used in a kHz to multiple 10 MHz range to transmit data or power wirelessly. They can be described as AC mag
RF, Microwave, Antennas and Optics :: 02-15-2015 14:42 :: FvM :: Replies: 10 :: Views: 668
I would like to do a sanity check on a near-field to far-field transform problem that I am struggling with. I have some planar recorded near-field data and would like to transform these data to far-field data and subsequently depict the field in spherical coordinates as E(r, theta, phi) where r is the radius, (...)
Electromagnetic Design and Simulation :: 12-19-2014 20:11 :: kviksand81 :: Replies: 0 :: Views: 611
The LCRC model represents the transducer near it's resonance frequency, but not far from fundamental resonance frequency or e.g. overtone resonances. The "R" parameter respresents the sum of internal losses and external energy transfer, so it's supposed to change with the load conditions like interfacing the transducer with di
Analog Circuit Design :: 12-11-2014 21:09 :: FvM :: Replies: 2 :: Views: 582
For simple static charges, there is no propagation, and the above definitions don't really apply (lambda -> infinity). Therefore, we typically say that there is no far-field region, and everything behaves like the near field.
Electromagnetic Design and Simulation :: 11-12-2014 17:39 :: PlanarMetamaterials :: Replies: 3 :: Views: 730
there ARE ways to do a reasonable far field measurement in a near field chamber. There are plenty of published papers on the method.
RF, Microwave, Antennas and Optics :: 09-01-2014 22:02 :: biff44 :: Replies: 10 :: Views: 906
i am currently working on a macro for cst mws and i am in search of sample cst source data. For example i need a.fsm or .rsd file for source fields(near/far). i need these file to do a debug run of my macro.
thanks in advance
Electromagnetic Design and Simulation :: 08-01-2014 11:52 :: rahul_chavan :: Replies: 0 :: Views: 627
Let's see a simple qualitative way to see that a reflector can affect the feeder.
Let's consider feeder and a reflector consisting of an infinite perfect conductive plane. Then, by the method of images, the plane can be substituted by the image of the feed. In far or near-field, this image has an interaction with the original feeder, dependent of t
RF, Microwave, Antennas and Optics :: 04-09-2014 19:02 :: zorro :: Replies: 5 :: Views: 675
In reactive near field the electric and magnetic fields are not orthogonal and any object placed in this region will distort the antenna pattern.
This is one clue that could give information where this field stops when moving far from the antenna. For doing this, have to do a far-field antenna pattern measurements, before and after placing (...)
RF, Microwave, Antennas and Optics :: 04-02-2014 10:42 :: vfone :: Replies: 5 :: Views: 490
I've never heard of P.I.C. before but I can tell you all landline modems use echo cancellation training with test patterns to cancel near and far end echoes.
WiFi on the other hand gets cancellation from any transmitter that echoes off walls with a cancellation effect called Rician Fading or Rice Fading. This can generate a null when an echo is e
Digital communication :: 03-18-2014 03:54 :: SunnySkyguy :: Replies: 1 :: Views: 458
im simulating a spiral receiving antenna in freq. range 2-18Ghz.
the antenna is placed closed to several metal conductors, and i want to simulate the radiation pattern of antenna. i want to know which one of the closed materials(metals) should be considered in simulation. i mean if we want to neglect some conductors near the antenna , how much it
RF, Microwave, Antennas and Optics :: 02-23-2014 09:19 :: J.C.Maxwell :: Replies: 0 :: Views: 428
That's a nice picture. :) And now for something completely different: have you got an architectural diagram of the algorithm of how it will look in an FPGA? if not - drawing this is a good place to start before you even go anywhere near VHDL.
PLD, SPLD, GAL, CPLD, FPGA Design :: 02-05-2014 05:33 :: mrflibble :: Replies: 9 :: Views: 1262
The radiated power of a small magnetical "antenna" at 24 Hz into free space (= far field) will be effectively zero. I guess, you are rather interested in the magnetical near field. It's proportional to Ampere-turns multiply coil area.
RF, Microwave, Antennas and Optics :: 11-21-2013 23:20 :: FvM :: Replies: 6 :: Views: 486
As far as I see, both ends have the same (13 mm) diameter. The IR sensor is apparently placed under a removable cap near the LCD display (as shown with the 400 photo).
The ability to measure the temperature of small devices is specified by the 1:1 spot:distance ratio. A minimal spot size isn't specified, but it will be surely several mm.
Miscellaneous Engineering :: 09-07-2013 12:04 :: FvM :: Replies: 4 :: Views: 1287
I am planning to simulate, and in a single setup, an FSS-Antenna system. I need to study the effect of different field patterns of a source antenna on the performance of an FSS structure. The simulation scenario has the following givens:
1- An antenna, in both the radiative-near-field (Fresnel region) and far-field (Fraunhofer region),
RF, Microwave, Antennas and Optics :: 07-29-2013 09:56 :: eng.amq :: Replies: 0 :: Views: 485
The diode is biased near the break down point. Once the diode avalanches it conducts and will remain in a conducting state or have a long recovery time unless quenched. With the addition of RL there is a voltage drop when current flows which will drop the voltage far enough to terminate the conduction in some diodes. In other diodes, especially InG
Elementary Electronic Questions :: 07-04-2013 00:42 :: HMS1021 :: Replies: 1 :: Views: 602
There's no principle limitation to operate a buck converter with a duty cycle slightly abobe zero. In so far, I don't understand the meaning of the diagram. There's also no limitation for the switch transistor, except for achieving reasonable efficiency. Voltage feedback is presumed, however.
Duty cycles near zero will occur in any standard buck
Power Electronics :: 03-13-2013 11:16 :: FvM :: Replies: 13 :: Views: 753
What about the price?
Is an outdoor measurement setup less expensive than a big chamber with a near field measurement?
And perhaps the outdoor measurement is more accurate, maybe you can find some numbers....
RF, Microwave, Antennas and Optics :: 02-07-2013 10:51 :: flanello :: Replies: 3 :: Views: 462
I was wondering if anyone had any experience in near-field to far-field back transformations. I have a simulated far-field pattern and I'd like to back project the fields onto the aperture of the array. I've gotten NF-FF transformations to work and also NF planar back to the aperture to work but I'm having trouble with back projecting (...)
Electromagnetic Design and Simulation :: 01-18-2013 20:27 :: bradstreet14 :: Replies: 0 :: Views: 351
Without seeing your calculation, I don't want to guess finally about the problem. Although 3λ is near field, the field strength won't be be very different from far field value according to Friis equation, presumed you are using simple antennas (e.g. a dipole) and don't have strong reflections.
RF, Microwave, Antennas and Optics :: 12-09-2012 12:23 :: FvM :: Replies: 4 :: Views: 575
I have a basic question in FDTD.I know formula and concepts of Huygens surface and I know formulas of near field to far field transformation (NFTFF) and also I can write matlab codes for this purpose.but I have a simple question.
for NFTFF calculations,where I should place Huygens surface?before PML or in edge of PML?because as distance from
Electromagnetic Design and Simulation :: 11-04-2012 22:39 :: ghasem_008 :: Replies: 6 :: Views: 1668
Hi every body:-)
i am trying to design a simple current sensing interconnect , composed of a driver with current Iwin , lossy transmission line with impedance Z0, near and far- end voltage vwin, vout and receiver with termination resistance Rt nad received current Irec, i have 3 simple equations
Iwin=IDsat=(w/2l)*mu*cox* (Vgs -vth)^2 ---> eq (1)
Analog Integrated Circuit (IC) Design, Layout and Fabrication :: 10-19-2012 23:55 :: Eman kamel :: Replies: 0 :: Views: 508
A dipole array is boxed in a rectangular box similar to radiation boundary box in HFSS. It radiates at 915MHz. The wavelength at 915MHz is 32cm. The far field is > 16cm. Can the power radiated be measured, say at 10 cm (in the near field) right outside the rectangular box assuming rectangular box is 10cm wide and long?
Would the power radiated m
RF, Microwave, Antennas and Optics :: 07-18-2012 15:32 :: kae_jolie :: Replies: 2 :: Views: 997
However, if I run the simulation with an airbox which is just very slightly larger than the antenna size, the simulated values become very close to the measured ones.
Makes perfect sense.
These low frequency "antenna" tags have negligible far field radiation. They work with inductive coupling in the near field only,
Electromagnetic Design and Simulation :: 07-08-2012 10:02 :: volker_muehlhaus :: Replies: 2 :: Views: 2872
I don't see current waveforms considered in your calculation, in so far I don't expect that it's correct for conventional power supplies with filter capacitor. For reasonable filter capacitor values, a "form factor" Irms/Idc of 1.6 for full wave rectifiers and 2.0 for half wave rectifiers is assumed.
PFC power supplies have near to unity power f
Power Electronics :: 06-19-2012 07:45 :: FvM :: Replies: 5 :: Views: 2607
In HFSS, my understanding is that power radiated from antenna is calculated at radiation box? So, does the radiation box act as a receive antenna?
In real world scenario, what is the method to measure power radiated from an antenna? Isn't it to have a receive antenna in the far field or even the near field?
Electromagnetic Design and Simulation :: 05-20-2012 08:15 :: kae_jolie :: Replies: 1 :: Views: 715
For low frequency RFID, the "antenna" tags are indeed inductors. They work with inductive near field coupling, which is different from normal far field antenna radiation.
Electromagnetic Design and Simulation :: 04-20-2012 10:14 :: volker_muehlhaus :: Replies: 6 :: Views: 1029
How current, near and far fields are related, depends on your geometry, and of course wavelength. Maybe you can give some additional information.
RF, Microwave, Antennas and Optics :: 04-12-2012 12:24 :: WimRFP :: Replies: 6 :: Views: 592
Capacitor vs. Battery
* store energy in an electric field.
* charge stored in a capacitor is proportional to the potential difference between the two plates
* is charged by applying a voltage across the terminals which causes positive and negative charges
* inner resistance is near infinite.
* far lower energy density (compared t
Elementary Electronic Questions :: 12-18-2011 14:10 :: kak111 :: Replies: 7 :: Views: 2157
Yes I know, but since I use far radiation boundary for my antenna, there is no need any more to use a near field one, and this for the same reason I specified above.
I mean that near fields can be plotted anywhere inside the far field radion boundary, so why do I need to use the "near-field sphere".
Electromagnetic Design and Simulation :: 12-14-2011 16:22 :: bya036 :: Replies: 2 :: Views: 1175
As far as I know, the RFID antennas work in the near-field region, so you must obtain a good understanding of the behavior of your antenna in the near-field.
RF, Microwave, Antennas and Optics :: 10-28-2011 13:53 :: amihomo :: Replies: 2 :: Views: 732
I don't understand how the waveform with V near 100 V is related to a buck converter circuit with 20V input supply.
Subharmonic oscillation, if occuring, is a matter of the switch mode controller, so you should primarly show the controller circuit for a discussion of the effect.
As far as I'm aware of, the oscillation occurs in a controller
Power Electronics :: 10-08-2011 08:09 :: FvM :: Replies: 8 :: Views: 2392
I would like to know, how is the correct distance between the antenna under test and the probe using the planar near-field technique.
Someone could help me to understand more about this.
RF, Microwave, Antennas and Optics :: 05-05-2011 18:02 :: markito86 :: Replies: 4 :: Views: 963
both near field and far filed will work
RF, Microwave, Antennas and Optics :: 04-26-2011 06:59 :: kspalla :: Replies: 4 :: Views: 876
I only see the Antenna Parameters (like power radiated, power incident, power accepted, etc...) for far Field. It does not do it in near Field, why? Impractical?
Electromagnetic Design and Simulation :: 04-07-2011 22:51 :: kae_jolie :: Replies: 0 :: Views: 969
there is always a comparison between near and far field measurement system. How much does a spherical or cylindrical near field system cost.
RF, Microwave, Antennas and Optics :: 04-07-2011 07:16 :: snkhan :: Replies: 2 :: Views: 552
Hi, I'm working on a nearField to farfield (planar scanning) code in matlab.
I have just tried to test this code on an easy structure (open-ended waveguide) but the radiation pattern is different from that obtained using literature equation.
Does someone know a working script to implement the NF2FF planar transformation ?
Electromagnetic Design and Simulation :: 03-23-2011 15:22 :: markito86 :: Replies: 0 :: Views: 1133
3) near field is relate to polarized, but it's different method from far field.
RF, Microwave, Antennas and Optics :: 02-11-2011 21:49 :: tony_lth :: Replies: 2 :: Views: 583
I'm using FEKO 5.4 and would like to determine the distance where the near-field converges to the far-field within a certain tolerance. I'm having a bit of difficulty in figuring out how to implement this entirely in FEKO. From what I can tell, I can't even subtract the near-fields from the far-fields in (...)
Electromagnetic Design and Simulation :: 02-03-2011 01:24 :: Zangetsu57 :: Replies: 0 :: Views: 2065
Now depends in what kind of near-field you are. For example in Reactive near field the Electric-E and Magnetic-H fields are not orthogonal, and polarization is not a meaningful parameter.
Myself, I would go in the far field to measure the polarization of the antenna.
RF, Microwave, Antennas and Optics :: 12-09-2010 18:53 :: vfone :: Replies: 2 :: Views: 1126
near means it is within the same segment while far means it is in another segment.
Microcontrollers :: 11-02-2010 12:38 :: amraldo :: Replies: 4 :: Views: 1689
My question is for a far-band simualtion by hfss, hou should i set the soluaiton frequency?
e.g, my filter's Center frequency is 5Ghz (BW 0.5Ghz), so for the in/near-band simulaiton, my soluaiton freqeuncy is set to 5Ghz.
If I want to simulate a far-band response from 20~25Ghz, should I still keep the same soluaiton (...)
Electromagnetic Design and Simulation :: 10-28-2010 20:42 :: zhul3 :: Replies: 2 :: Views: 1082
The whole complication with near field analysis is that you have a radial component to your fields rather than just the typical far field "TEM". So, indeed your near field plots will be a function of the size of your near field sphere.
I would use the near field radius that you plan to measure for (...)
Electromagnetic Design and Simulation :: 07-30-2010 13:37 :: tallface65 :: Replies: 4 :: Views: 2064