Triple LNB

Triple Feed and Polarizer
The design uses a feed horn devloped under previous ESA contracts. The waevguide part however containing the polarizer required a complete new design in order to meet the cross polar isolation specification. During the project it became clear that the design would need to be based on a Septum Design as this offers the highest isolation capability. This Septum was researched from the available literature and subsequently design and optimised using HFSS. These simulations included all draft angles to allow for the casting manufacture process. Subesquent to this a prototype was machined and tested to verify performance. This prototype verified the HFSS simulations and was directly usable for the casting design.

IF Band Stacking and Matrix Switch with multiple DRO’s
The new design require a total of four DRO’s and ten mixers as well as a complex signal switching and channel selection matrix. These signals were routed to each new LNB via high impedance tracks on the rear of the main PCB, these were screened to maintain isolation using cutouts in the main base casting.

The second issue was the routing of the six IF signals to the switching and channel selection matrix while maintaining a specified 40dB isolation. This required the use of multiple layer RF boards in order to reduce radiated coupling of IF signals. In addition to this we needed to solve the issue of connecting the multiple control and power supply signals between the LNB’s and switch matrix without degrading the overall isolation performance. Other issues that added complexity to the design was be the power consumption of the overall system and the management of this power supply and the complex Diseqc control software that will be required to control the switch and channel selection matrix along with the LNB status functions.

Diseqc software controlled by customer receiver
The other complexity in the design was be the power consumption of the overall system and the management of this power supply and the complex Diseqc control software that will be required to control the switch and channel selection matrix along with the LNB status functions. This was addressed using a microcontroller and a unique suite of software written for this LNB. All of this software required extensive testing in order to verify compliance with each aspect of the customer specification and backward compatibility with all other products deployed by the customer.