Bow Tie Antenna : Working, Radiation Pattern & Its Applications

Wideband systems are the best solution in various Electromagnetic applications like multi‐standard high‐resolution radars, signal detectors & communications. For wideband systems, a bow‐tie antenna has been identified as the best solution for systems because of its wideband input impedance & simple planar shape. It is also considered a wideband high-gain antenna system once they are associated with artificial magnetic conductors. At present, these antennas are used in wideband arrays & beam-steerable. But, the bow-tie geometry should be chosen cautiously if a necessary gain has to be maintained in a particular direction over an entire frequency range of interest. Even though, this selection is frequently problematic, because various kinds of bow-ties frequently use different parameters like length of radiators, reference impedance, flare angle, measurement setups & materials. So this article discusses an overview of a Bow Tie antenna – working with applications.

What is a Bow Tie Antenna?

An antenna that is arranged in a bowtie configuration with two triangular stiff wire pieces or two triangular flat metal plates through a feed point at the space among the apexes of the triangles is known as a bow-tie antenna. This is a common type of antenna with a two-dimensional biconical design. These antennas are frequently used for short-range UHF TV reception and also for GPR applications because they have a set of stringent antenna performances like ultra-wideband performance, low frequency of operation, least ringing, planning, lightweight & compact.

There are different types of bow tie antennae like Bowtie slot, wideband printed, slotted bowtie patch, bowtie microstrip fed, CPW fed curved bowtie slot, and double-sided triangular.

How Does A Bow Tie Antenna Work?

The bow tie antenna works by using triangular elements rather than straight rods like the antenna elements. In this antenna, triangular elements are attached outside on two sides to make a bow tie. These two antenna elements touch nearly at the center. Sometimes, this antenna is known as a butterfly antenna because it seems like a butterfly. The bow tie elements contain a metal bar that locks the antenna, then it is known as a cat’s whisker antenna. This type of antenna may look like log periodic antennas, although they are not considered as LP antennas.

The frequency range of bow antenna mainly depends on the triangular or rounded bow tie type. Triangle bow-tie frequency ranges from 2.4 to 6.0 GHz whereas the rounded bow-tie frequency ranges from 2.4 to 6.5 GHz.  Bow tie antenna is used in HFR and UFR ranges. The metal elements in this antenna are resonant elements that create an electric field between them. When an electromagnetic wave passes through an electric field and a current gets generated which can be fed to a radio receiver or transmitted from a radio transmitter.

When a radio receiver receives the current it is amplified and processed to understand the information encoded in the electromagnetic waves. Whereas in a transmitter the reverse happens where a radio transmitter generates an electrical signal that is fed to the bow-tie antenna. The electrical signal excites the electrical field between the metal arms which emits the electromagnetic waves into the air.

Bow Tie Antenna Calculator

The following formulas are utilized to calculate the outputs if we know the frequency like wavelength, bandwidth, width, distance, and height.

We know that ‘λ’ = c/f

Where ‘λ’ is the wavelength.

‘c’ is propagation velocity within the air.

‘f’ is carrier frequency within MHz.

Wavelength

The operating frequency is 2400MHz. It is the frequency of the electromagnetic wave transmitted and received by antenna.

Wavelength is calculated as λ’ = c/f.

We know that ‘c’ = 3×10^8m/sec which is the speed of the light.

Substitute these values in the above wavelength equation.

λ’ = c/f => 3×10^8/2400 = > 125 mm.

Bandwidth

To calculate bandwidth, the formula B = 0.33xf => 0.33 x 2400 = 792 MHz.

Width

To calculate the width, The formula is w = 0.375 x λ x 1000mm

W = 0.375 x 125 x 1000mm => 46.875 mm.

Distance

To calculate distance, we have a formula like D = 0.02066 x λ.

D = 0.02066 x 125 => 2.5825 mm.

Height

To calculate the height, we have a formula like H= 0.25 x λ.

H= 0.25 x 125 => 31.25 mm.

Bow Tie Antenna Radiation Pattern

In antenna design, the radiation pattern is the angular dependence of the radio waves’ strength from the antenna. So, it is the deviation of the radiated power through an antenna as the direction function away from the antenna. Antenna’s Radiation Pattern will show the radiated energy distribution by the antenna within space.

The term Radiation is used to signify the emission or response of wave at the antenna to specify its strength. It can be plotted graphically as an angular position & radial distance function from the antenna. So, these are diagrammatical representations of the radiated energy distribution into space like a direction function. The radiation pattern of this antenna is similar to the dipole antenna. Bow tie antenna polarization is vertical and it will get signals in the direction of a cone or the butterfly wings are pointed.

Characteristics

The characteristics of the bowtie antenna are discussed below.

• This antenna uses triangular elements like the antenna elements.
• This type of antenna has a vertical polarization so it will receive signals in the way of the wings or cone.
• These antennas are shaped through a folded conductive wire.
• This antenna has much better bandwidth as compared to a thin-wire dipole antenna.
• These types of antennas have electrodes in different forms like a Sharp BT, an Asymmetric BT, a Broad BT, a Doubled BT & a Blunted BT.

Advantages

The advantages of bow tie antenna include the following.

• Bow tie antennas are lightweight.
• The design & fabrication is easy.
• Better equilibrium within the radiation.
• It has a planar structure and compact size.
• This antenna’s bandwidth will be enhanced with triangular elements above straight ones.
• These antennas get signals frequently from a 60-degree angle.
• Its design is very stronger.
• These are not expensive.
• The mesh reflector within this antenna is very efficient as compared to yagi antennas.

The disadvantages of bow tie antenna include the following.

• These antennas have poor transmitting efficiencies in the low end of their frequency range.
• These antennas have end-fire reflections, dispersion characteristics, limited bandwidth, poor gain, and efficiency.

Applications

The applications of bow tie antennae include the following.

• At present, these antennas are still used in many applications like 5G, multiband WLAN/ LTE/ WiMAX, IR polarimetry, short-range radars, and ground-penetrating.
• A bow tie antenna is used in all UWB applications such as ground penetrating radar, Wi-Fi, wireless & microwave imaging-based applications.
• These antennas are extensively utilized for GPR applications
• These are frequently used for short-range UHF TV reception.
• Bowtie antenna applications are the same as dipole antennae except with wider bandwidth.
• This antenna is normally utilized in wireless communication applications like satellite antennas, base stations of cell phones, etc.
• This antenna is also a perfect choice where medium-range to long-range transmission & reception is required.

Thus, this is an overview of a Bowtie antenna – working with applications. This antenna is considered a two-dimensional version biconical antenna which has numerous elements sticking out within a 360-degree pattern in two directions. Here is a question for you, what is an antenna array?