A DBS service provider has approached us to design, develop, and manufacture their own variant of the Dual Linear and Circular Polarised LNB, which is completing its development under ESTEC Contract 18289/04/NL/AD.
This new variant will be used to double the bandwidth currently available for transmitting domestic television signals.
Currently, this can only be done by using the linearly polarised 11.7 GHz to 12.2 GHz FSS band in conjunction with the existing circularly polarised 12.2 GHz to 12.7 GHz DBS band.
The unit will be designed to receive circularly polarised signals of either polarity in the frequency band 12.2-12.7 GHz Ku band from current orbital locations and also receive linear polarised signals of either polarity in the frequency band 11.7-12.2GHz in the Ku band from the collocated satellites.
- Feed Horn: The current install base of antennas is very elliptic, and therefore an elliptic radiation pattern is required from the feed horn with equivalent performance in both CP and LP modes.
- Customer Approvals: A rigorous approvals process with a high degree of extended life testing over a wide temperature range is operated by the customer.
- Designing a Frequency Diplexing and switching system that can meet the high performance demands of the customer.
- High cross polar performance over a wide RF bandwidth.
- Complex power supply design is required to meet a low current budget from the STB.
The major benefit for the operator will be the ability to introduce an LNB to market at an earlier stage when the regulatory process has not been clarified.
The use of an up grade capable LNB that can be switched from LP/CP to all CP without changing any installed hardware at the customer premises is considered a major advantage.
The unit will be designed to receive circularly polarised signals of either polarity in the frequency band 12.2-12.7 GHz Ku band from current orbital locations and also receive linear polarised signals of either polarity in the frequency band 11.7-12.2GHz in the Ku band from co-located satellites.
The proposed method of carrying this out is to detect the power present within the waveguide in all polarisations with a pair of linear waveguide probes. The probes will be aligned to the horizontal and vertically polarised transmissions from the satellite. The analogue signal-processing will take the horizontal and vertically polarised components and split them into two channels. The first channel represents the linearly polarised signals, H and V, and these are then output directly to the next stage of the LNB where mixing to the IF occurs.
However, the other two channels, one each from the horizontal and vertical probes, are combined in a hybrid coupler to produce Right Hand circular polarisation and Left Hand circular polarisation.
These two channels are now amplified and then output to the next stage of the LNB where mixing to the IF occurs. After each of the four mixers, IF amplification occurs and the four outputs are presented to a signal switching diplexing network. This system has to be able to present the signals in a standard format and frequency plan. This operation has to be maintained when the LNB is operating in both CP/LP mode and pure CP mode following the sending of a once in a life time polarization switch over command from the STB.
The complete LNB will be manufactured with an integrated feed horn and waveguide.
The project is divided into 8 Work Packages. These are:
- Electrical Design (WP1)
- Mechanical Design (WP2)
- PVT Build (WP3)
- Design Jigs and Manufacture (WP4)
- FCC Aprovals (WP5)
- Feed Horn and Cap Design (WP6)
- Project Admin (WP7)
- Customer System Tests (WP8)
- Electrical Design (WP1): Design activities completed.
- Mechanical Design (WP2): Design activities completed.
- PVT Build (WP3): Completed.
- Design Jigs and Manufacture (WP4): Completed.
- FCC Aprovals (WP5): Completed.
- Feed Horn and Cap Design (WP6): Completed
- Project Admin (WP7): Completed
- Customer System Tests (WP8): Completed