Antenna Design The dimensions of the rectangular patch with T-slot antenna is 108 X 52 mm2. The height (h) of air substrate between patch and ground plane is 7 mm. The dimension of the T-slot is as shown in the Figs. The probe is fed at (X = 0, Y = -10 mm) from the patch centre. Antennas are fed with SMA coaxial probe of 50Ω characteristic. In recent years, the U-slot patch antenna established itself as a versatile, low profile and cost effective antenna that can be fine-tuned for ultra-wideband operations. The main objective of this thesis is to propose an effective practical design procedure to design U-Slot antenna and provide physical insight into the. ANTENNA DESIGN Figure 1 shows the proposed CPW-fed slot antenna. The antenna is designed on FR-4 substrate of dielectric constant 4.4 and thickness 1.6 mm. The antenna is printed on one side of the substrate. Initially, a rectangular slot is printed having dimension W 4 × (L 3 + L 4 + L 5). A double-stepped feed line having width W f1 and W. The proposed system is designed with Multiple L-slot micro-strip patch antenna and the antenna is fed with co-axial feed. Insertion of multiple-slots in a patch helps to overcome the problem of bandwidth limitation. The proposed antenna can be used for WLAN and WiMAX applications. High Frequency Design PATCH ANTENNAS electrical length of this line is λ/2, the impedance at the fed edge is repeated at the other, which effectively feeds the two slots in-phase with nearly equal antenna currents. Thus, the patch operates as an array of two slots with a free-space separation somewhat less than λ/2.
- FEKO Website Content Migration to Altair Locations - March 25, 2018
- Designing EMC Compliant Products for a Connected World - February 26, 2018
- Why Join the Electromagnetic Support Forums? - September 20, 2017
A microstrip-fed slot antenna was designed using Antenna Magus for the following specifications:
- 5 GHz centre frequency
- 50 Ω input impedance
- FR4 substrate, ε = 4.35, height = 1.5mm
Dimensions of the slot and feed-line are:
- Ws = 743.3 μm
- Ls = 18.58 mm
- Wf = 2.892 mm
- Wm = 625.7 μm
- S = 8.053 mm
Slot Antenna Design Formulas
FEKO’s implementation of the planar Greens function features the ability to model the slot in the ground plane as magnetic triangles, which means that only the slot is meshed and not the ground plane itself, saving significantly on simulation resources.
Reflection coefficient of microstrip-fed slot antenna
Related content
Visit the website
A slot antenna consists of a metal surface, usually a flat plate, with one or more holes or slots cut out. When the plate is driven as an antenna by an applied radio frequency current, the slot radiates electromagnetic waves in a way similar to a dipole antenna. The shape and size of the slot, as well as the driving frequency, determine the radiation pattern. Slot antennas are usually used at UHF and microwave frequencies at which wavelengths are small enough that the plate and slot are conveniently small. At these frequencies, the radio waves are often conducted by a waveguide, and the antenna consists of slots in the waveguide; this is called a slotted waveguide antenna. Multiple slots act as a directivearray antenna and can emit a narrow fan-shaped beam of microwaves. They are used in standard laboratory microwave sources used for research, UHF television transmitting antennas, antennas on missiles and aircraft, sector antennas for cellular base stations, and particularly marine radar antennas. A slot antenna's main advantages are its size, design simplicity, and convenient adaptation to mass production using either waveguide or PC board technology.
Structure[edit]
As shown by H. G. Booker in 1946, from Babinet's principle in optics a slot in a metal plate or waveguide has the same radiation pattern as a driven rod antenna whose rod is the same shape as the slot, with the exception that the electric field and magnetic field directions are interchanged; the antenna is a magnetic dipole instead of an electric dipole; the magnetic field is parallel to the long axis of the slot and the electric field is perpendicular. Thus the radiation pattern of a slot can be calculated by the same well-known equations used for rod element antennas like the dipole. The waves are linearly polarized perpendicular to the slot axis. Slots up to a wavelength long have a single main lobe with maximum radiation perpendicular to the surface.
Antennas consisting of multiple parallel slots in a waveguide are widely used array antennas. They have a radiation pattern similar to a corresponding linear array of dipole antennas, with the exception that the slot can only radiate into the space on one side of the waveguide surface, 180° of the surrounding space. There are two widely used types:
- Longitudinal slotted waveguide antenna - The slots' axis is parallel to the axis of the waveguide. This has a radiation pattern similar to a collinear dipole antenna, and is usually mounted vertically. The radiation pattern is almost omnidirectional in the horizontal plane perpendicular to the antenna over the 180° azimuth in front of the slot, but narrow in the vertical plane, with the vertical gain increasing approximately 3 dB with each doubling of the number of slots. The radiation is horizontally polarized. It is used for vertical omnidirectional transmitting antennas for UHF television stations. For broadcasting, a cylindrical or semicircular waveguide is sometimes used with several columns of slots cut in different sides to give an omnidirectional 360° radiation pattern.
- Transverse slotted waveguide antenna - The slots are almost perpendicular to the axis of the waveguide but skewed at a small angle, with alternate slots skewed at opposite angles. This radiates a dipole pattern in the plane perpendicular to the antenna, and a very sharp beam in the plane of the antenna. Its largest use is for microwave marine radar antennas. The antenna is mounted horizontally on a mechanical drive that rotates the antenna about a vertical axis, scanning the antenna's vertical fan-shaped beam 360° around the water surface surrounding the ship out to the horizon with each revolution. The wide vertical spread of the beam ensures that even in bad weather when the ship and the antenna axis is being rocked over a wide angle by waves the radar beam will not miss the surface.
History[edit]
The slot antenna was invented in 1938 by Alan Blumlein, while working for EMI. He invented it in order to produce a practical type of antenna for VHF television broadcasting that would have horizontal polarization, an omnidirectional horizontal radiation pattern and a narrow vertical radiation pattern.[1][2]
Prior to its use in surface search radar, such systems used a parabolic segment reflector, or 'cheese antenna'. The slotted waveguide antenna was the result of collaborative radar research carried on by McGill University and the National Research Council of Canada during World War II.[3] The co-inventors, W.H. Watson and E.W. Guptill of McGill, were granted a United States patent for the device, described as a 'directive antenna for microwaves', in 1951.[4]
Other uses[edit]
In a related application, so-called leaky waveguides are also used in the determination of railcar positions in certain rapid transit applications. They are used primarily to determine the precise position of the train when it is being brought to a halt at a station, so that the doorway positions will align correctly with queuing points on the platform or with a second set of safety doors should such be provided.
See also[edit]
- Microwave Radiometer (Juno) (has a slot array antenna)
- RIMFAX (radar for Mars rover has slot antenna design)
Slot Fed Patch Antenna Designs
References[edit]
- ^Blumlein, Alan (1938-03-07), 'Improvements in or relating to high frequency electrical conductors or radiators', British patent no. 515684
- ^Burns, Russell (2000). The life and times of A.D. Blumlein. Institution of Engineering and Technology. ISBN0-85296-773-X.
- ^Covington, Arthur E. (1991). 'Some recollections of the radio and electrical engineering division of the National Research Council of Canada, 1946-1977'. Scientia Canadensis: Canadian Journal of the HIstory of Science, Technology and Medicine. 15 (2): 155–175. doi:10.7202/800334ar.
- ^Watson, William Heriot; Guptill, Ernest Wilmot (6 November 1951), Directive Antenna for Microwaves, retrieved 20 December 2016
External links[edit]
Patch Antenna Design Formula
- 'Slot Antennas'. Antenna Theory.
- Slotted Waveguide Antennas Antenna-Theory.com