Questions tagged [dipole]
The dipole tag has no usage guidance.
29
questions
1
vote
0answers
54 views
Dipole array antenna radiation pattern
I have the radiation pattern for a dipole antenna with working frequency of 11 GHz, it looks like figure 1. I wanted to create an array antenna consisting of 2 elements with that same individual ...
0
votes
2answers
47 views
How can adding a reflector to a half-wave dipole (in a Yagi Uda antenna) increase the gain by more than 3dB?
I have been designing a Yagi Uda antenna using CST Microwave Studio.
For a half-wave dipole the directivity (at 1.3GHz) was 2.116dBi.
After I added a Reflector, the directivity improved to 6.074dBi.
...
1
vote
1answer
21 views
Measure antenna S11 next to another source
I have a dipole antenna designed to work on ~800MHz and 2.44GHz frequency, and a miniVNA Tiny USB device that I can use to measure return loss of the antenna. I connect the antenna directly to the DUT ...
0
votes
3answers
43 views
Why is a transmitter dipole's ends the max/min voltage instead of the middle?
If the AC voltage source is connected to the middle of the dipole, I'm confused on why the edges have the max/min voltage instead of the middle.
In my mind, the middle of the dipole is closer to the ...
0
votes
0answers
11 views
Sector antenna dipole orientation
I have a question about the positioning of the dipoles inside sector antenna which are used in mobile communication. Usually, they are oriented perpendicularly to each other, so-called X-pol ...
1
vote
2answers
130 views
Standing waves in Dipole antennas
I'm relatively new to antennas. In most of the textbooks, it is said that we want to minimize standing waves in the transmission lines by matching the characteristic impedance of the line with the ...
0
votes
1answer
63 views
How can I tell if an antenna is a dipole antenna
Background
I'm trying to select an antenna for an FCC/IC-approved cellular module, SIM7000A. Apparently, to meet IC modular certification, you need to select an antenna which has
a) equal or less ...
1
vote
0answers
35 views
Why current distribution of a receiving dipole antenna depends on incident frequency?
When an incident EM wave hits the antenna, the electric field is parallel to the whole wire and start moving all electrons on it simultaneously. I understand that the current at the ends should be ...
1
vote
0answers
95 views
Dipole Antenna impedance and feed point, what is the effect of long distance to coax connector?
I have a folded dipole being made with a pair of twisted wires where each wire is 1/4 λ long and the dipole is constructed by twisting the centers of the wires so that the twisted pair is ...
0
votes
0answers
57 views
Unexplained differences in behaviour between U.FL-terminated antenna and SMA-terminated antenna
I would like your opinions/advice regarding an unexplained observation between a U.FL-terminated antenna and an SMA-terminated antenna. Both antennas are from the same manufacturer and normally tuned ...
1
vote
2answers
126 views
Standing waves feedline length and dipole antenna feedline
so I have a question regarding reflections/characteristic impedance and there relation with a quarter wave transformer and its feed line.
Now I have found this video very useful for visualising what ...
-2
votes
1answer
54 views
Calculating inner resistance of a linear dipole
I've been stuck on a question for a while now, so I'd really appreciate if you could take a look at this: I'm supposed to calculate the dipole's inner resistance. I've got that E= 15V, R1= 1200 Ohm ...
0
votes
0answers
64 views
Linear antenna: with electromagnetic coil, trap circuit
I am trying to understand the concept of the linear antennas.
I have read that the linear antennas are the simplest form of the antenna in the case of asymmetrical (coaxial) feed.
what happens if I ...
0
votes
2answers
81 views
Partially Collapse Telescoping Antenna to Change Effective Length
I recently purchased a cheap RTL-SDR kit to experiment with SDRs and different frequency bands. This kit came with 23cm and 100cm telescoping antennas. I now wish to use the 100cm antenna to pick up ...
1
vote
1answer
2k views
Shortening a long antenna with a capacitance
In many circumstances it is not possible to make a dipole antenna that has the optimum length of \$\lambda/2\$ (or monopole with ground plane of length \$\lambda/4\$). Car antennas are for example ...
1
vote
1answer
358 views
Length of the dipole antenna
I know it is really stupid question, but I canāt understand.
I have a picture with dipole antenna (different length). If I have the current distribution along the length, that it is easy to determine ...
0
votes
0answers
127 views
Dipole antenna director
Say a free metal rod is placed at a distance Ī»/2 from a dipole antenna (fig), both being of same length. I understand it will reflect and dampen the signal going to the left. But how will it impact ...
0
votes
0answers
24 views
Which of the impedance values below represent an pasive dipole that absorbs both active power P and reactive power Q, and why?
I stumbled upon this exercise and I can't find anything in my notes regarding to this notion where it absorbs both kind of powers. You guys might have any ideas?
These are the impedance values:
Z1 = ...
6
votes
2answers
2k views
Why is the bunny-ears TV antenna normally connected to 300 ohm twin lead?
The bunny-ears antenna is similar to a dipole, which has an impedance of ~75 ohm.
Why are the elements of such antennas connected directly to 300 ohm ladder line? Wouldn't that cause mismatch losses (...
1
vote
0answers
105 views
Ground under PCB pads for wire dipole?
I have a wire dipole antenna that I am connecting to a PCB. I know that ground should be cleared under most antennas. However, in my case the wire will be mounted away from the PCB. Do I need to ...
2
votes
1answer
285 views
Why are this monopole and dipole antenna so similar?
I opened two different GSM antenna housings as shown on the images.
The first image shows the RF SOLUTIONS ANT-GHEL2R-SMA antenna, which is an helical 1/4 wave monopole antenna.
The second image is ...
3
votes
1answer
265 views
Dipole Sleeve Antenna design in fresh water - Transmission frequency and emitted power?
Hello dear antenna enthusiast,
I would like to receive and emit EM signals with a dipole antenna in the range of **433.9 to 434.5 MHz in fresh water.
So I chose a half-wavelength dipole sleeve-...
0
votes
1answer
332 views
Dipole antenna electric field generation
An antenna that is of half wavelength of a signal is a dipole antenna. When a signal is fed to this antenna, it should induce an electron flow. However, it is also said that this electron flow ...
1
vote
2answers
1k views
Dipole Antenna Current Distribution
Above is a connection of half-wave dipole antenna. The book states that the current profile is same at any given time instant on both the radiators, each of quarter wavelength length.
Now my ...
0
votes
1answer
171 views
Why for a dipole antenna half wave length is optimum size?
For a dipole antenna, half wave length is optimum size. Why is this so? What I understand is that radiation resistance of antenna is around 50 ohms at this size, which matches with the characteristic ...
0
votes
1answer
1k views
near field power density formula for a dipole antenna
I am looking for a formula for near field power density from a dipole antenna antenna. Is cylindrical model is sufficient? Do I have to consider ground reflection too? Please share your ideas?
0
votes
1answer
60 views
How do you account for receiver sensitivity in tranceiver half wave dipoles?
if you are to design 2 halfwave dipoles, both can transmit to each other using 3 watts and have receiver sensitivity of -80dbm (a picowatt). Suppose they are 800m and have same height from ground. How ...
1
vote
3answers
231 views
Dipoles lengths underwater vs on land
A submarine (for example) uses a VLF communications system to remain in contact with its headquarters while submerged. The submarine drags a resonant dipole wire antenna behind it in the water. The ...
0
votes
1answer
70 views
isoPower Input-to-output dipole emissions
In ADI's Application Note: Recommendations for Control of Radiated Emissions with isopower Devices. Section "Input-to-output dipole emissions", it says:
Input-to-output dipole radiation is ...
