How do you tell if an antenna needs a ground plane?
How do you tell if an antenna needs a ground plane?
To function as a ground plane, the conducting surface must be at least a quarter of the wavelength (λ/4) of the radio waves in radius. In lower frequency antennas, such as the mast radiators used for broadcast antennas, the Earth itself (or a body of water such as a salt marsh or ocean) is used as a ground plane.
What are the effects of ground on the radiation of monopole antenna?
The general effect of electrically small ground planes, as well as imperfectly conducting earth grounds, is to tilt the direction of maximum radiation up to higher elevation angles and reduce the gain. The gain of actual quarter wave antennas with typical ground planes is around 2-3 dBi.
Why do we use monopole antennas while having dipole antennas?
The reason for this is simply because no radiation occurs below the ground plane; hence, the antenna is effectively twice as “directive”. Monopole antennas are half the size of their dipole counterparts, and hence are attractive when a smaller antenna is needed.
How does a ground plane antenna work?
As the name indicates the antenna ground plane acts as a simulated ground. It is found that for a monopole antenna like a quarter wavelength vertical, the ground acts as a plane to reflect the radio waves so that an image of the top half of the antenna is seen in the Earth.
Does a ground plane antenna need to be grounded?
The NEC (National Electrical Code) requires any metal antenna mast to be grounded to its own ground rod. The antenna ground plane or mount is connected to a ground rod only for electrical/lightning protection and not for receiving or transmitting requirements.
How big should a ground plane be?
All Answers (51) As per calculations, ground plane (m * n) should be minimum 6 times the height of the substrate added to the length (m) and width (n) of the patch. But, it can be optimized using slits, EBGs, PBG structures called Defected Ground Structures.
What is the gain of monopole antenna?
The vertical dipole—or its electromagnetic equivalent, the monopole—could be considered one of the best antennas for LMR applications. It is omnidirectional (in azimuth) and, if it is a half-wavelength long, has a gain of 1.64 (or G = 2.15 dBi) in the horizontal plane.
Does a 1/4 wave antenna need a ground plane?
Does a 1/4 wave antenna need a ground plane? Answer: Yes. All 1/4 wave antennas work best if they are installed in the center of a metal ground plane with at least 1/4 wave length radius (1/2 wave length diameter: ~6 inches for 900Mhz and ~3 inches for 2.4Ghz); larger is better.
How does a non ground plane antenna work?
A no ground plane CB Antenna is a CB antenna that doesn’t require a ground plane (large metal surface under it) to operate. A No Ground Plane antenna installed on a vehicle or boat constructed of metal will not operate correctly. A no ground plane antenna is designed to use the ground or water to transmit horizontally.
How do you make a folded unipole antenna?
One usually constructs the folded-unipole by modifying an existing monopole antenna. First one connects the base of the tower directly to the ground system by shorting out the base insulator.
Can a folded over dipole contact the ground plane?
Since the opposite ends of the original dipole were at opposite charge polarity (Fig. 1A), we must leave these ends unconnected upon folding; or, in the ground plane case, the folded-over section must not be allowed to contact the ground plane.
What is the radiation resistance of a folded antenna?
As shown by the calculations in the Appendix, the approximate radiation impedance of the folded eighth-wave monopole of Fig. 4D is 6.2 ohms. A similar analysis of a bottom-loaded eighth-wave monopole, Fig. 4E, shows that its radiation resistance also is 6.2 ohms, which is the same as for the folded case!
How is the power of a monopole antenna calculated?
In the US, the Federal Communications Commission (FCC) required that the transmitter power measurements for a single series-fed tower calculated at this feed point as the current squared multiplied by the resistive part of the feed-point impedance. Electrically short monopole antennas have low resistance and high reactance.
