Objective of the project was to design and develop surface mountable filters (one at L-band, one at C-band) that can be integrated into the RF module of frequency converter equipment.
The targeted improvement is a highly integrated Ku- or Ka-band to IF converters with up to 20% mass and footprint saving with respect to the state of the art. The in-house multilayer LTCC technology based on Ferro Tape A6M has been proposed for the manufacturing of the filters, having the capability to integrate all the filter elements in compact size.
Main challenges were first to achieve a flat in-band response having at disposal a technology that offers only moderate unloaded Q-factor. Secondly, the proper setup of the LTCC technology with Ferro Tape and the prediction of the electrical and mechanical parameters affecting the electrical performances of the filters. Finally, the choice of the filter configuration to make the layout as compact as possible.
The evolution of satellite-based telecommunications services is such that the main consulting firms agree that Broadband Access services will overtake TV Broadcast as the primary application of communications satellites. Such services are urging the need for new High Throughput or Very High Throughput Satellites (HTS, VHTS), which are characterized by deep use of Multibeam Coverages at high frequency to multiply the useful bandwidth and on board analogue and digital channel handling to support Mesh and Bilateral Star architectures.
These features call for a multiplication of frequency converter chains, which in turn must be optimized in terms of mass, volume, footprint, power as well as in terms of cost for manufacturing, tuning and testing.
Minimizing the size of IF filters allows for a compact and lightweight design of frequency converters, and SMD format is suitable for RF on PCB design, that allows for automated assembly and test.
The products realized have the following main features:
- The L-band filter centred at 900MHz covers a bandwidth of 500MHz. The amplitude response is flat in band within 1.5dBpp. The transfer function is a 7th order elliptic bandpass filter featuring a quite high selectivity. The filter is low-cost in that it is fully realized on a LTCC multilayer substrate without any lumped component.
- The C-band filter centred at 5350MHz covers a bandwidth of 2.5GHz. The amplitude response is flat in band within 1.3dBpp. The insertion loss is less than 8dB. The transfer function is a 6-2 pseudo-elliptic bandpass filter (two transmission zeros) featuring a quite high selectivity. The filter is low-cost in that is fully realized on a LTCC multilayer substrate without any lumped component.
Both filters are ideal for frequency converters followed by A-to-D converts in communication payloads featuring DSP.
The Engineering Models of the L-band and C-band filters have been successfully designed, manufactured and tested, according to the objective of the Study.