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THE DESIGN AND EVOLUTION OF ANTENNAS FOR WI-FI NETWORKS

FEBRUARY 2015

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AGENDA• Introduction •Antenna fundamentals

Antenna terminology

Antenna basics

•Antenna solutions Antenna module for 11n applications

Antenna solution for 11ac applications

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ANTENNA FUNDAMENTALS

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ANTENNA TERMINOLOGY• dB • Gain/ directivity • Backlobe/ Front to Back ratio • Side Lobe Level (SLL) • Propagation/ propagation loss • Multipath • Polarization/ cross polarization • Dynamic range/ signal to noise (S/N)

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DB• Definition: The term dB is a convention used in microwave and RF.

It simplifies the link calculations. Each component in the link is replaced by a black box with input and output terminals

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GAIN/ DIRECTIVITY• Definition: Compared with a point source that has constant energy

in any direction, an antenna with gain has its energy focused in a certain direction in space.

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BACKLOBE/FRONT TO BACK RATIO• Definition: Byproduct of any antenna in free space or when

mounted on a metallic backplate.

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SIDE LOBE LEVEL (SLL)• Definition: SLL is a byproduct of arraying several antenna

elements in order to achieve higher gain/ directivity.

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PROPAGATION/ PROPAGATION LOSS• Definition:EM energy propagating in any given medium will suffer

from energy loss. The propagation loss factor defines the rate at which energy is lost.

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MULTIPATH• Definition: An EM energy propagating in an indoor or outdoor

environment, with obstacles, will reflect, scatter or diffract (depending on size of obstacles relative to the wavelenght).

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MULTIPATH (CONT.)

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POLARIZATION/ CROSS POLARIZATION• Defintion: EM energy can be polarized similar to light. The three

main types are • Vertical (V) • Horizontal (H) • Circularly polarization (CP)

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DYNAMIC RANGE/ SIGNAL TO NOISE RATIO• Definition: The radio is able to operate in the presence of

interference. The ratio between signal and interference or noise determines the dynamic range (signal to noise). The modulation and data rate depends on the signal to noise ratio.

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ANTENNA BASICS• Transmit- Receive/ Reflection- Transmission • Antenna efficiently/ sensitivity, range and coverage • Point source • Monopole antenna • Dipole antenna • Microstrip/ printed antenna • Microstrip antenna arrays • Reflector antenna • Sectorization

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TRANSMIT-RECEIVE/REFLECTION-TRANSMISSION• Definition: Receiving or transmitting is receiprocal. In either case

a voltage is created across the antenna terminals. No RF component, passive or active is perfectly matched. As a result, some of the EM energy is reflected depending on the mismatch involved.

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ANTENNA EFFICIENCY/ SENSITIVITY, RANGE & COVERAGE• Definition: What differentiates one wireless link from another is

further coverage and better range. As the RF front-end is more efficient (lower loss) and proper antenna selection, sensitivity will improve and hence coverage and range.

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POINT SOURCE• Definition: Point source is an ideal antenna where coverage

is constant at any direction. The antenna gain is assumed to be 1 or 0 dB.

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MONOPOLE ANTENNA• Definition: The Monopole antenna is quarter wavlength long (half

a dipole). The Monopole antenna is fed against a ground reference. The radiation pattern depends on the size of the ground plane. Many variations of the Monopole exist such as Bent Monopole, IFA and PIFA antennas.

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DIPOLE ANTENNA• Definition: The Dipole antenna structure is a balanced one.

No need for ground a plane. The radiation performance is less affected by external effects (such as metal objects). It is large compared with wavelength.

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DIPOLE- MONOPOLE EXAMPLE

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MICROSTRIP/ PRINTED ANTENNA • Definition: The Microstrip antenna or printed antenna is a narrow

band and typically medium gain. The antenna is etched on a dielectric substrate and it has the radiator and ground plane/ reflector in its back. The radiator can take many shapes that will determine its bandwidth and beam shape.

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MICROSTRIP ANTENNA ARRAYS• Definition: By arraying the Microstrip antenna element in a certain

arrangement (X- axis elements and Y- axis elements), the main beam, side lobe level and back lobe could be shaped as needed. Some of the microstrip antenna arrays could have typical gains in the 12-24 dB range.

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DUAL POLARIZED STACKED ARRAY

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DUAL POLARIZED STACKED ARRAY (CONT)

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REFLECTOR ANTENNAS• Definition: A reflector antenna is made from a feed and a reflector.

The reflector is intended to the reflect the EM energy emanating from the feed in a plane wave front. The antenna gain and beamwidth is controlled by the aperture size of the reflector, mainly.

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GRID REFLECTOR WITH CUP DIPOLE

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SECTORIZATION• Definition: In applications where there are multiple users/ clients

that need to operate simultaneously, the concept of sectorization is an effective solution (cellular networks, Wi-Fi networks, etc.). When discussing sectorization, several terms are used:

Directivity: Gain of individual sector Beam overlap: Gain coverage overlap from sector to sector. Isolation: In order to have each sector independent of neighboring sectors, there must be sufficient physical isolation between the sectors in order to minimize interference. Frequency reuse: In order to efficiently use all the channels available and increase the overall capacity of the users and data managed, high isolation conditions between the sectors are needed to exist.

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SECTORIZATION (CONT.)

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WI-FI ANTENNA SOLUTIONS

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ANTENNA SOLUTIONS

• Solution overview • Antenna module for sectored 11abgn application • Antenna module for sectored 11ac application • Antenna element for omni 11ac application

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802.11ABGN SOLUTION OVERVIEW • Modular solution • High isolation • 2x2 or 3x3 antenna versions • Dual band antenna elements – 2.4GHz and 5GHz

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STANDARD ANTENNA ELEMENT

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802.11ABGN ANTENNA MODULE - 2X2 TOP VIEW

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802.11ABGN ANTENNA MODULE- 3X3 TOP VIEW

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802.11AC SOLUTION OVERVIEW• Higher gain in the 2.4 Ghz band • Yagi effect, frequency dependent • Minimal gain drop relative to standard antenna module

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CENTER ANTENNA ELEMENT WITH DIRECTOR

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802.11AC ANTENNA MODULE- 3X3 TOP VIEW

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EXAMPLE: EIGHT PORT 11AC AP

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EXAMPLE: EIGHT PORT 11AC AP COVER

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EXAMPLE: FOUR PORT 11ABGN AP

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EXAMPLE: FOUR PORT 11ABGN AP COVER

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802.11AC OMNI SOLUTION OVERVIEW• Antenna element is a broadband bent monopole • Antenna elements are mounted on a ground plane • Interleaving architecture • High interelement isolation

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ANTENNA MODULE- TOP VIEW

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SYSTEM VIEW

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