PAGE CONTENTS
Objectives
- enhanced performance of the equipment where the frequency generation will be used
- extension of the product portfolio
- build-up of expertise in the MMIC VCO design at RUAG Space AB.
Challenges
The key issue is a synthesized LO generator with excellent phase noise close to the carrier and much improved phase noise at offset frequencies between 1-10 MHz, compared to the LO generator based on an X-tal oscillator and multiplier chain. The key component in this programme is the developed VCO MMICs.
One important issue is also to build up expertise in the MMIC VCO design at RUAG Space AB by the design work in close cooperation with Chalmers University.
System Architecture
The baseline LO frequency generator block diagram is shown in the figure below. The VCO frequency range for the PLL EM Unit is approximately 10 to 11 GHz.
The LO frequency shall be settable, within a given frequency range, by command (during manufacturing).
Plan
The Project was planned within two consecutive Tasks. Task 1 included all the system definition work, different LO solutions were investigated and the requirement specifications updated (VCO and PLL EM unit). Also technology trade off for the VCO topologies, VCO semiconductor process and foundry were performed in task 1. The task ended with a technology trade off review in October 2014. Task 2 included detailed design, manufacturing, integration and test for the VCO MMIC and PLL EM Unit, and ended in January 2017.
Most significant achievements of the project
- Three different VCO versions in the chosen GaN technology process has been designed, evaluated and tested.
- One PLL EM Unit designed, manufactured and tested to show function and performance of the VCO.
The measured main parameters including
- Phase noise
- LO Harmonics
- Spurious at LO output (f/2, 3f/2, 5f/2, 100 MHz ref.)
- VCO tuning range (up to +60 V)
- Loop Band Width
- Output power (+12.5 – 13.5 dBm)
were within specified limits as set up for the PLL EM Unit. Measured Phase Noise is as expected and in line with calculations. The VCO tuning range was sucessfully extended (up to +60 V) by design of a new loop filter.
However the current status for the GaN technology is that it suffers from high 1/f noise which significantly degrades the phase noise performance.
The most significant achievements of the project also involve higher understanding of VCO design and modelling in general, and special in design and manufacturing a MMIC VCO using GaN technology.
A GaN varactor model based on measurements and suitable for phase noise simulations was also developed within the project and possible through the close cooperation with Chalmers University.
Current Status
All activities are completed:
- Baseline Technology Selection Review has been performed.
- Three different VCO versions in the chosen GaN technology process has been designed, evaluated and tested.
- VCO specifications have been detailed.
- One PLL EM Unit designed, manufactured and tested to show function and performance of the VCO.
