BESPOKE

Steatite provides a custom design horn antenna capability, providing a flexible and responsive microwave engineering approach to satisfy customer specific horn antenna requirements.

The Company designs bespoke and standard wideband low-loss radomes up to 40 GHz using Ray Optics and CST electromagnetic solvers, whilst FEA Solidworks simulation is used to determine wind load stress and deflection.

The radomes are manufactured using solid laminate with open moulding methods and low loss materials laid up as a “C” sandwich. Sandwich core radomes consist of either 2 or 3 layers of a core material between two or more thin sheets of composite. By varying the thickness in both solid laminate and sandwich construction, optimal performance is achieved for the particular frequency range required.

Large multilayer radomes typically up to 6m in diameter can be supplied; and a standard range of radomes are available from 1.1m to 4.8m in diameter.

Steatite has in-house software tools for the design of FSS and experience in the making of FSS radomes and sub-reflectors (singly and doubly curved); also in the design of circuit analogue materials and frequency selective radar absorbers and Salisbury screens. The Company carries out theoretical studies into the microwave properties of single and multi-layer dielectric structures for such purposes as microwave windows, radomes and structural components. The dielectric properties of materials can also be measured.

The ideal radome would appear totally transparent to any electromagnetic signal. Radomes must be designed to minimise the impact of the radome on the enclosed antenna performance. Application requirements often determine the importance of signal distortions such as insertion loss, and scattering into the antenna side lobes.

Solid laminate and sandwich core radomes can be assembled from multiple panels or 1 single piece (the number of panels depending on the size of the radome). Through the process of design it is possible to minimise the effect that the internal flanges has on scattering the signal.

A pre-preg manufacturing process is used and offers a high strength to weight ratio and improved capabilities of operating at high temperatures as well as an increased control over the resin to glass ratio.

Selecting a radome to match your requirements
The primary factors in selecting the type of radome for applications are performance and cost. Additional considerations include installation, wind/gust rating, ease of transportation and weight/snow -loading. All project factors must be considered in order to ensure an optimum match.

Initial cost approximation
The initial cost of a radome is primarily dependant on the size of the structure and increases with the radome surface area (radome diameter) .The material and labour costs in a radome increase geometrically with the diameter (note: doubling the diameter of a sphere increases the surface area by a factor of four).

Mechanical considerations
Radomes are designed to operate and withstand considerable wind speeds and snow or ice loading. Typically wind speeds of up to 60 m/s (134 mph), and snow or ice loading of up to 235 Kg/m2 9 (50Lb/ft2) however MICRIS can design a radome to match your particular loading requirements.

Steatite provides a custom design horn antenna capability, providing a flexible and responsive microwave engineering approach to satisfy customer specific horn antenna requirements.

Lensed Horns produce an improved gain figure, ideal for materials testing where a high field strength is achievable over the desired spot size, and may be an alternative to a reflector antenna solution. A lens may be retrofitted to existing horns are useful for EMC / HiRF measurement systems. Lensed horns provide lower back-scatter and improved sidelobe performance. Applications include: Radar Systems, EMC testing, Point-to-Point communication links, Traffic control systems and many others.

Hog Horns can be a useful compact and rigid alternative for sectoral horns and standard pyramidal horns. One of the better known applications of a Hog (or Hogg) horn is by Bell Telephone Laboratories where they ‘accidentally’ discovered microwave background radiation existing when they were pointing to the sky, this provided support for the Big Bang theory and in 1978 Penzias and Wilson received the Nobel Peace Prize for their momentous discovery. The distinctive shape of the hog horn can be an advantage for many applications, especially where space-saving is important.

Dielectric Filled Horns have the advantage of providing operation as a horn antenna but at a lower frequency than the physical size of the antenna would suggest. Filling with dielectric material may also be beneficial for matching an antenna that is designed to launch microwaves into a medium other than free-space. The trade-off for size reduction using dielectric filling, is greater losses in the dielectric material reducing gain and limiting to lower power usage. Steatite has designed many dielectric filled antennas, mostly in the standard waveguide sizes, however many variants may be considered.

Sectoral Horns give a larger beamwidth in one plane in comparison to the other plane where it is very narrow. This is desirable in many applications such as in broadcasting where a few sectoral horns may be arranged, back to back, to cover 360 degrees in azimuth. A fan beam enables the concentration of microwave energy in a fan pattern, as the name suggests, without wasting energy in the orthogonal plane where coverage is not needed. Sectoral horns may be designed for all standard waveguide sizes and also encompasses ridged wideband designs. The ‘flare’ may be designed to be an E-plane or H-plane flare.

Low Sidelobe Diagonal Horns may be useful to provide a solution when high gain and low sidelobes are required from an antenna. One major application is in radiometry work where the noise temperature of a target has to be measured with minimal contribution from sources outside the main beam, which may often be at a higher intensity than at the main beam. Generally Gaussian or corrugated horns are considered for this task however they may be expensive and of restricted bandwidth, both factors arising from the horn’s complex internal structure. Diagonal horns give a very similar level of performance but are simpler to make and have a wider bandwidth.

Steatite Antennas produces a wide range of Dual Linearly polarised antennas from 0.2 -40 GHz in a number of antenna packages such as Sinuous, Quad ridged and reflector / feed combinations. Dual Linear antennas offer a number of benefits such as polarisation diversity, the ability to operate on two channels simultaneously using one set of equipment. With two uncorrelated signals one channel may be used to transmit whilst the other is used for receive, thus allowing for a duplex communication link.

In antenna test ranges the use of a dual linear source antenna allows the polarisation to be remotely changed without the requirement to physically rotate the antenna. Co-polar and cross-polar measurements can be made without physically accessing the source antenna, allowing the full scattering matrix to be determined.

When a dual linear antenna is used in a monitoring role, where the polarisation is not known, the dual linear antenna may offer the opportunity to simultaneously monitor both vertical and horizontal polarisations.

Steatite Antennas has experience of designing and manufacturing monopulse antennas where monopulse antennas are used to precisely identify the direction of a radio signal.

In the simplest form they consist of two close spaced identical antennas whose outputs feeds a device called a comparator.  This device does two things:  first the two signals are added to produce a pattern having a peak at boresight; secondly they are subtracted producing a pattern that has a narrow deep null at boresight.  It has two corresponding output ports called sum and difference.

The sum pattern will have a smoothly varying shape which can be used to approximately identify the direction.  Having found the approximate direction the very sharp null in the difference pattern can be used to give a much more precise bearing, by instructing the control system to look for minimum signal.   The two port monopulse can only be used for tracking in one plane only, for example ships or land vehicles.

The technique can be extended to direction finding in two planes, for example tracking aircraft in elevation and in azimuth.  For this four identical antennas are needed, placed in a two by two arrangement.  These feed a more complex form of the comparator generating an overall sum, elevation difference and azimuth difference patterns.  It has three corresponding output ports.   The azimuth and elevation difference outputs each feed a separate control system which looks for a minimum in the corresponding patterns. For radar applications the transmitter is connected to the sum port.

The use of four identical antennas is ideal for relatively narrow bandwidth  applications where the fractional bandwidth is not much greater than 50%  (see products below) . However, there is a growing need for ultra wide band applications where four identical antennas cannot easily be used. This is because of a conflict in the requirement for an aperture to be large enough to radiate at the lowest frequencies of the band and the requirement for the distance between two antennas to be small enough at the highest frequencies of the band. To avoid these fundamental issues Steatite is able to develop quad-ridged 4-port feeds. This is a single integrated antenna capable of radiating four independent beam modes.  Bandwidths of 4:1 or greater are readily attainable.

Steatite Antennas has had a long involvement with the design and manufacture of both linear and planar waveguide slot array antennas. Typical examples include a simple six element UHF band linear array, a very high power 48 element L band planar array and a complex 32 by 32 element Ka band planar array. A variety of radiation pattern variants can be synthesised from maximum gain to suppressed sidelobes.

Various manufacturing methods are available ranging from sheet metal fabrication to CNC machining out of a solid billet when the precision demands.   The arrays may be fitted with low loss radomes for full weather protection. The Company’s in-house computer programs and electromagnetic simulation package CST Microwave® coupled with SolidWorks® mechanical design enable Steatite to design slot arrays that work first time without costly re-development. The manufacture is supported by an extensive test facility enabling the antennas to be fully characterised for VSWR, gain and radiation patterns before packing and shipping.

The design and manufacture of ultra wideband antennas is a core competency of the Company. A flexible technical approach in satisfying COTS and custom wideband-octave and multi-octave antenna requirements is a major part of Steatite’s capability.

A wide range of polarisations are offered including, single, dual polar, circular and dual circular. Experience established over forty years, has enabled the Company to develop a large portfolio of COTs wideband antenna products and satisfy several wideband custom antenna subsystem projects for civil and defence customers. As an example of our ultra wideband capability please review the COTS 0.8 to 40 GHz omnidirectional antenna QOM-SL-0.8-40-K-SG-L and the 0.9 to 18 GHz dual polarised horn antenna QWH-DL-0.9-18-S-SG-R.