The main object for the program was to develop and qualify two EQM frequency converter units between Ku-band and baseband. One up-converter and one down converter. The focus is on the interfaces to the digital signal processors on Ku-band satellites (High Throughput Satellites).
The converter units shall convert blocks of 250 MHz (down and up) between Ku-Band and baseband.
The development will target the requirements for a specific satellite. However, the development will be performed so that the equipment can be delivered to similar architectures and requirements to other primes. The aim is to be able to reuse concept and main building blocks with limited changes.
Frequency converters between Ku-band and ADC/DSP/DACs are expected to be seen on multiple programs. Various primes requests similar solutions and the same core functionality on different programs.
However, there will be different tradeoffs performed in each case that will lead to project specific requirements and require project implementations. The challenge is then to provide a cost efficient and well performing product based on a product building block approach.
The technical challenge in the program is mainly connected to the challenging requirements of the various building blocks in the design.
They can be summarized as following:
The Ku to BB Down Converter Unit will use a dual conversion plan via an IF at around 1.1GHz. This requires use of SAW filters for spectral cleaning. The wide bandwidth (250MHz) makes this design particularly challenging. In the signal chain the linear and efficient amplifiers must be traded against dynamic performance and power consumption. In this case the baseband output dynamics versus filter will be challenging. Also the in-band amplitude and group delay variation requirements are challenging due to the wide bandwidth.
The BB to Ku Up Converter Unit will also use a dual conversion with an IF at around 1.1 GHz. Also here SAW filter with wide bandwidth (250MHz) will be needed for spectral cleaning. Also for this unit the dynamic performance and power consumption must be traded against linear and efficient amplifiers.
The development will target two EQM units. They are designed to fit onto a customer specific architecture for converting from Ku to Baseband and vice versa. Baseband in this case is from 50-300 MHz, where the ADC/DSP/DAC performs all fine channelization and routing.
Ku bands are 14.0-14.75 GHz in uplink and 10.95 to 12.75 GHz for the downlink. Key in the Kongsberg Norspace design is the wide bandwidth (250 MHz) SAW filter centered at 1125 MHz (from 1000-1250 MHz), for spectral cleaning in both down and up-converter. For the upconverter a notch filter (at 950 MHz) is applied to take out the first LO break-through. Second LO and mirror band will then be sufficiently far from passband (at Ku) to allow for a simple Ku-Band filter. The units further contain a DC/DC converter, TM/TC for gain setting and have interface ports for the LOs
Down Converter Description:
The Ku/L converter chain consists of an input isolator, a Norspace Ku/L
converter hybrid and a discrete L-band section including the L-band Norspace standard hybrid amplifiers, SAW filter module, voltage variable attenuator (VVA) Norspace hybrid and digital attenuator. The second down conversion from L-band to baseband is performed with a discrete mixer hybrid. The baseband section contains discrete L-C low-pass filters and Norspace standard hybrid amplifiers.
Up Converter Description
The baseband to L-band conversion is performed with a discrete
mixer hybrid. A Norspace standard hybrid amplifier is used to amplify the baseband signal before the mixer to ensure sufficiently low noise figure. A discrete L-C low-pass filter is used to reject out-of-band (aliasing) signals from the digital processor in the baseband section. A SAW module as well as a SAW Notch hybrid is used to remove the LO and lower sideband from the first upconversion. The L-band chain consists of Norspace standard thin film hybrid amplifiers, a VVA hybrid, digital attenuator .
The second upconversion to Ku-band is performed in a Norspace designed L/Ku converter hybrid. The converter hybrid contains a GaAs MMIC amplifier and a GaAs MMIC driver amplifier as well as a GaAs mixer. Three microstrip filters on Alumina substrates are used in the RF section to remove the LO leakage and lower sideband from the upconversion. The filters are all designed in-house. An isolator is located at the RF output.
The following development plan has been followed during the program:
PDR – Preliminary Design Review
This milestone concluded the initial work with the unit optimization and critical design
CDR– Critical Design Review
This milestone concluded the detailed design and development as well as the supporting performance and reliability analysis.
EQM TRB – Test Review Board / Final Review
After the completion of the EQM test campaign, the TRB was successfully held.
The program is now completed.