Cobham Antenna Systems

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Antenna Primary Specification Frequency, Gain, Bandwidth FREQUENCY Most antennas are designed to operate efficiently within 10% bandwidth. 2.5GHz ±5% means a frequency of 2.375 to 2.625 GHz, a 250MHz bandwidth. For example, at 10GHz an antenna will operate from 9.5 to 10.5GHz. Always specify the frequency band or centre frequency plus bandwidth. L-band or S-band is not sufficient. 6 GAIN Antennas passively increase the radiated power by concentrating it into certain directions. The gain of an antenna is a measure of its directionality. Gain is measured in dB (Isotropic) or dBi and is usually expressed in dBi or dB relatively to an isotropic source (equal in all directions). Antennas are not 100% efficient and have internal losses. The gain of an antenna includes these losses: Gain = Directivity - Internal losses Gain is the additional signal strength that the antenna provides in one direction at the expense of signal strength in other directions. An antenna is normally a passive device providing gain by directing the energy to a required pattern. The result is a higher signal strength in one direction and lower in other directions. Measured pattern of directional antenna BANDWIDTH Omni antenna VOA4- 1400/1130 page 41 The bandwidth of an antenna is the range of frequency where the antenna is operating effectively. Typically our antennas have a nominal 10% bandwidth. This may increase or decrease depending on the antenna and performance required. It is important to specify the exact bandwidth required. Specifying L-band for example is not sufficient. L-band covers 1 - 2 GHz; much larger than at 10% bandwidth. Shows gain relative to isotropic pattern of antenna
Antenna Primary Specification HPBW Half Power Beam Width HPBW Half Power Beam Width Omni Antenna A dipole is the simplest, omni-directional antenna. It has 360° azimuth coverage; the energy is squeezed from top and bottom to provide gain on the horizon. The elevation pattern is measured by taking a vertical cut through the beam. The antenna’s beamwidth is defined by the angle over which the radiated energy falls to half its peak level. This is known as the Half Power Beam Width (HPBW), or the -3dB point. This beamwidth will apply to the elevation pattern whilst the azimuth beamwidth will be 360°. Refer to radiation pattern example. Omni azimuth pattern Directional and Sector Energy is directed from vertical and horizontal sides to produce a directional lobe or sector beam. For directional and sector antennas azimuth and elevation HPBW are specified separately. Sector azimuth pattern Sector elevation pattern Omni elevation pattern Directional flat panel antenna FPA20-47V/1323 page 71 Sector antenna SA15-120- 58V/983, 120° azimuth coverage page 75 7
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Group 3 - 2GHz to 3GHz Omni Model F
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Group 4 - 3GHz to 4GHz Directional
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Group 4 - 3GHz to 4GHz Sector Model
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Group 5 - 4GHz to 6GHz Sector Model
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Group 6 - 6GHz and over Directional
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Group 6 - 6GHz and over Omni Model
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Ultra Wideband and Extended Perform
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Accessories Mounting Kits Model Des
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Cobham Antenna Systems Microwave An
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Cobham Antenna Systems

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