The objective of this project is to develop two 'Ku-band waveguide lens antennae' for satellite communication. The particular application here is satellite TV reception. There is an eventual possible application for reception of a large signal span in one antenna while the other receiving array (antenna) can be used in a variety of other applications.
The patented waveguide lens techniques allow multi-satellite reception in an angular coverage of 30°, and a satellite angular separation down to 2°. One antenna type is designed for the frequency band 10.75-12.75 GHz, which is the frequency range used for satellite TV in Europe. In North America, however, the corresponding frequency band 11.7-12.75 GHz is used. The second antenna type is designed for that band. The antenna can, however, be designed for mass production for any frequency band from 4-40 GHz.
One of the goals of this project has been to develop cost effective mass production methods in order to commercially exploit the waveguide lens technology to a mass market. The different mass market segments have been identified by a market study. In this study the demands of e.g. antenna shape and size as well as signal processing characteristics were analysed.
A production plant has been implemented and there is continuous manufacturing of the product.
Freedom of choice. Every TV set with a set-top box can select from the complete range of channels. Switching between satellite positions and channels is done without delay.
Innovative and future applications. A pioneer invention that forms a new platform for development.
Combination of Internet and TV. Some LNB´s can be directed to Internet traffic and others to TV channels.
The position of the LNB´s avoids heat damage and receives reduced amounts of thermal noise as compared with a reflector antenna for example.
The design is lightweight, has low wind load resistance and is unaffected by ice and snow.
In this project, an alternative method for multi-satellite reception based on a new patented technique has been implemented. Other applications suitable for the waveguide lens technique can be summarized as:
- Combined satellite TV and wireless Internet
- Active or passive signal scanning of a wide area, e.g. for: guarding a wider area, microwave scanning of passengers and goods, microwave detail scanning and analysis of wood, as a car radar (seeing) antenna in the 70 GHz band
- In wireless LAN applications, multiple point-to-point communication links can be arranged in the same antenna, thus eliminating the slow-down of data speed when many nodes are transmitting omni-directional and thus disturbing each other.
- Burglar-secure antenna system with receivers protected in a casing behind the antenna. Such casing is also excellent in repeater systems, where received and transmitted signals do not disturb each other.
Furthermore, VSWR measurements have revealed that the antenna is also well-suited as a transmitter. With the waveguide lens technique no motor or moving part is needed for multi-satellite reception. Furthermore, the design is appealing and colours can freely be chosen, as the antenna does not generate a sun-burn-focus.
The lens antenna is an array consisting of 680 rectangular waveguides arranged rotationally symmetrically around the antenna axis. The antenna operates as a concave lens, with an index of refraction n<1, which focuses the satellite signals and a reverse image of the Clark belt is projected at a focal plane behind the antenna. The concave properties of the lens ensures that the received plane waves are focused at one point.
The phase of the waves is shifted forward in the waveguide, and the properties of the waveguides determine the shift. There are two Fresnel zones in the antenna and, for each zone, the signal path to the focus is one wavelength longer than the previous one. The result is that all signals transmitted through the antenna reaches the focal point in phase. The circular symmetry of the antenna eases the control of the electromagnetic behaviour and reduces cross polarization.
The media inside the waveguides is dielectric technical EPS with the effective permittivity S=1,1. The dielectric makes the extremely thin copper waveguide walls possible with good mechanical robustness and it also allows a more compact construction as compared to air-filled waveguides.
Satellite signals in a span of 36° can be received, which theoretically allows reception from 18 satellites because the required spacing between consecutive satellites is 2°. The receivers (LNBs) are placed on a focal line behind the antenna. Offset angle reception is of course very important in multi-satellite communication and a graph of the amplitude for different offset angles, at 12.25 GHz for the North American model, is shown in the figure below. The very low side-lobe levels help reduce disturbance from neighbouring satellite reception.
A summary of the total undertaking is as follows:
- Design computer. A EM-simulation software study is done and EM-simulation software implemented.
- Market study. The study is focused on the European and North American markets and it reveals the needs and requirements of multi-satellite reception.
- EPS tool 1. The design of a waveguide lens antenna for the European market operating at 10,75-12,75 GHz.
- EPS tool 2. The design of a waveguide lens antenna for the North American market operating at 11,7-12,75 GHz.
- Breadboard Testing Facility. The implementation of a smaller production plant for the manufacturing of antennas, which can be tested.
- Near- and far-field measurements. The produced antennas are analysed and tested.
In this project, two new waveguide lens antennas have been developed. A market report, that covers the European and American markets, has been done and it reveals the need for multi satellite reception. It further outlines the requirements and differences of the two different markets which have led to conclusions about antenna size, frequency band and number of received satellite positions.
A breadboard testing facility has been implemented and the production process is running continuous, fulfilling the quality regulations, and with the two new designed antenna types as output. Quality checking procedures of produced units are developed and a projected mass-market production plant design is approved.
The antenna is called 'Cybertenna'. It is now in the marketing phase, and has received much attention and awards for innovation, design and technique.
An EM-software study has been done in order to find a tool that can support the development of the two antennae. Two types of EM simulation software: CST Microwave Studio and Quick Wave 3D, have been used in the design phase. The fact that the waveguide lens antenna structure is very complex and large compared to wavelength, has lead to a new approach in the simulations and the formation of a research group dealing with large array simulations has been implemented.