European Space Agency

KaLQ Ka- to L-band downconverter / L-band to Ka- upconverter


The main object for the program was to develop and qualify two EQM frequency converter units between Ka-band and L-band. One up-converter and one down converter.

KaLQ is a logical continuation of the ARTES 5.2 contract KaHyb with the development of the Ka/L and L/Ka converter hybrids.

The two EQMs will specifically target the Ka-band ISL market. 


The frequency converters between Ka-band and L-band isare tailored to meet the requirements of generic Inter Satellite Link terminals, typical for LEO-to-GEO communication. Normally these converters will have a fairly narrow receive section and a broadband transmit section.


The converter designs are based on already developed building blocks, except for the Ka/L and L/Ka converter hybrids. These are key elements in the design and many of the unit challenges have been connected to the development of these hybrids. Thise development of these hybrids was performed in an Artes 5.12 program, but the development was highly incorporated in this development and the performance was optimized to meet the requirement of this program. For the already developed building blocks, different tradeoffs performed in each case 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.


Both the converter units are challenging. A common challenge is the relatively high input or output frequency. Ka-band designs will always give challenges in implementation. For the Up Converter it is difficult to maintain a flat in-band response and the required group delay flatness over the defined 400MHz bandwidth. For the Down Converter the Ka-band input frequency and a relatively high gain result in challenging test methodology to assure accuracy and repeatability in the tests.


The development will target two EQM units. They are designed to fit onto a customer specific architecture for converting from Ka- to L-band and vice versa. However, the design will give the basis for a generic design fitting in future Ka-band Inter Satellite Link terminals.


For the Down Converter, the Ka-band input frequency is defined at 23.2GHz. This will be converted in a single converter stage down to an L-band frequency at 2.0GHz. This includes filtering and amplification of the received signal.

The Up Converter Unit provides the frequency translation from 1.5GHz input to 27.2GHz. This is also performed in a single conversion stage. The unit also provides the required filtering and amplification. The BW for the upconverted signal is 400MHz.

Both the Down Converter and Up Converter units includes internal frequency sources for the frequency translation as well as internal DCDC converters.

System Architecture

Down Converter Chain Description:

The incoming RF signal at Ka-band is routed through a waveguide isolator followed by a Ka- to L-band converter hybrid. The converter hybrid contains a single mixer stage for frequency conversion together with filtering and amplification of the RF signal. A microstrip low pass filter at the input of the hybrid, together with a band pass filter provides the required rejection before the mixer. A L-band PCB is located after the converter hybrid and provides additional filtering and amplification of the IF signal, as well as Temperature Gain Control (TGC) to ensure a stable performance over temperature.


Up Converter Chain Description

The incoming RF signal at L-band is routed through the L-band PCB, which utilize filtering amplification and Temperature Gain Control of the signal. An equalizer element gives the opportunity to compensate for frequency variation over the useful bandwidth (amplitude tilt). A converter hybrid is located after the L-band PCB and contain a single mixer stage for frequency conversion from L-band to Ka-band. From the converter hybrid, the signal is routed though a waveguide filter to suppress unwanted mixing products and the LO leakage, and in to a driver hybrid to provide the required output level. A RF power detector is located at the output of the driver amplifier, to provide an analogue output power TM.


LO Generation (similar for both units)

The reference signal for the LO frequency synthesizer is generated by an OCXO module at around 15 MHz. A sampling phase base synthesizer is generating a LO signal at L-band, which is multiplied by a factor of 18 in three separate multiplication stages to reach the desired Ka-band frequency. Various microstrip filter between each multiplication stage ensures a clean LO signal at the input of the mixer, and minimize unwanted mixing products due to harmonics of the LO.


EPC (similar for both units)

The EPC is realized by a fly-back converter topology and transforms the main bus voltage of +28V nominal to the required secondary voltages. 


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.

Current status

The program is now completed. 

Status date

Wednesday, June 28, 2017 - 08:32