Download Citation on ResearchGate | On Nov 30, , Juan Carlos Gómez and others published Diseño de Antenas Yagi Uda Usando. Abstract— This paper presents a simple broad band printed Yagi Uda antenna IndexTerms—Printed YagiUda antenna, Reflectors, Directors, Driven element. Yagi-Udaantenna From Wikipedia, the free encyclopedia Drawing of Yagi-Uda VHF television antenna from , used for analog channels.

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Views Read Edit View history. This iterative analysis method is not a straightforward. The waves from the multiple elements superpose and interfere to enhance radiation in a single direction, achieving a very ywgi-uda increase in the antenna’s gain compared to a simple dipole.

In the next section on Yagis, I’ll go further into the design of Yagi-Uda antennas. It is simple to construct and has a high gaintypically greater than 10 dB.

Online Calculator Yagi Uda Antenna

You are probably familiar with this antenna, as they sit on top of roofs everywhere. Given the associated costs of erecting an antenna and rotor system above a tower, the combination of antennas for three amateur bands in one unit is a very practical solution. The radio waves from each element are emitted with a phase delay, so that the individual waves emitted in the forward direction up are in phase, while the waves in the reverse direction are out of phase.

This so-called trap has the effect of truncating the element at the higher frequency band, making it approximately a half wavelength in length.

Consequently, these antennas are often empirical designs using an element of trial and erroroften starting with an existing design modified according to one’s hunch. Using the above relationships, then, we can solve for I 2 in terms of I The gain increases with the number of parasitic elements used.

Yagi—Uda antennas used for amateur radio are sometimes designed to operate on multiple bands. A picture of Professor Yagi with a Yagi-Uda antenna is shown below.

The reflector element is slightly longer than the driven dipole, whereas the directors are a little shorter. Typically, the first director will add approximately 3 dB of overall gain if designed wellthe second will add about 2 dB, the third about 1. Due to the differences in the elements’ lengths Z 11 and Z 22 have a substantially different reactive component.

All the other elements are considered parasitic. Gain versus separation for 2-element Yagi antenna.

While the above qualitative explanation is useful for understanding how parasitic elements can enhance the driven elements’ radiation in one direction at the expense of the other, the assumptions used are quite inaccurate.


The antenna was invented in by Shintaro Uda of Yagi-ida Imperial UniversityJapan[5] with a lesser role played by his colleague Hidetsugu Yagi. The yagi-jda of voltage to current at this point is the driving point impedance Z dp of the 2-element Yagi:.

Therefore, the forward waves add together, constructive interference enhancing the power in that direction, while the backward waves partially cancel each other destructive interferencethereby reducing the power emitted in that direction.

One must take into account ahtenas additional phase delay due to the finite distance between the elements which further delays the phase of the currents in both the directors and reflector s. The Yagi—Uda antenna consists of a number of parallel thin rod elements in ahtenas line, usually half-wave long, typically supported on a perpendicular crossbar or “boom” along their centers.

Retrieved 4 July As alluded to in the yaggi-uda paragraph, the lengths of the directors are typically less than the resonant length, which encourages wave propagation in the direction of the directors.

The rest of the elements are parasitic – they reflect or help to transmit the energy in a particular direction.

The Yagi-Uda Antenna – Yagi Antennas

And now knowing the phase and amplitude of I 2 in relation to I 1 as computed above allows us to determine the radiation pattern gain as a function of direction due to the currents flowing in these two elements.

The work was presented for the first time in English by Yagi who was either Uda’s professor or colleague, my sources are conflictingwho went to America and gave the first English talks on the antenna, which led to its widespread use.

However the “Yagi” name has become more familiar with the name of Uda often omitted. There are no simple formulas for designing Yagi—Uda antennas due to the complex relationships between physical parameters such as.

Freq. [MHz]

Now the difficult computation is in determining that mutual antenss Z 21 which requires a numerical solution. This will cause a phase distribution yagj-uda occur across the elements, simulating the phase progression of a plane wave across the array of elements. The Japanese military authorities first became aware of this technology after the Battle of Singapore when they captured the notes of a British radar technician that mentioned “yagi antenna”.

Yagi antenna design is done most often via measurements, and sometimes computer simulations. Vertically polarized arrays can be seen antenqs the cheeks of the P and on the nose cones of many WWII aircraft, notably the Lichtenstein radar -equipped examples of the German Junkers Ju 88 R-1 fighter-bomberand the British Bristol Beaufighter night-fighter and Short Sunderland flying-boat. However these elements are not driven as such but receive their energy from the field created by the driven element, so we will find almost the opposite to antenad true.


How the antenna works. With only the driven element present the driving point impedance would have simply been Z 11but has now been modified by the presence of the parasitic element. Such a complete exact analysis considering all of the interactions mentioned is rather overwhelming, and approximations are inevitable on the path to finding a usable antenna.

This appears to have been due to Yagi filing a patent on the idea in Japan without Uda’s name in it, and later transferring the patent to the Marconi Company anntenas the UK. An example of a Yagi-Uda antenna is shown below.

A full analysis of such a system requires computing the mutual impedances between the dipole elements [11] which implicitly takes into account the propagation delay due to the finite spacing between elements.

There is typically only one reflector; adding more reflectors improves performance very slightly. One way of thinking about the operation of such an antenna is to consider a parasitic element to be a normal dipole element of finite diameter fed at its centre, with a short circuit across its feed point.

Retrieved from ” https: These waves combine to produce the net forward wave bottom, right with an amplitude slightly larger than the individual waves. These elaborate designs create electrical breaks along each element both sides at which point a parallel LC inductor and capacitor circuit is inserted.

A major drawback was the Yagi’s inherently narrow bandwidth.

Yagi–Uda antenna

The combination of the director’s position and shorter length has thus obtained a unidirectional rather than the bidirectional response of the driven half-wave dipole element alone.

Yagi demonstrated a proof of conceptbut the engineering problems proved to be more onerous than conventional systems. Let the driven element be designated 1 so that V 1 and I 1 are the voltage and current supplied by the transmitter.

When questioned, the technician said it was an antenna named after a Japanese professor. We model element number j as having a feedpoint at the centre with a voltage V j and a current I j flowing into it.

As is well known in transmission line theory, a short circuit reflects all of the yagiuda power degrees out of phase.