NFG | ESA CSC

Status

Completed
Status date

2017-02-21
Activity Code

5C.216

Objectives

The primary objectives with the developments are

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.

Benefits

To have a wide product portfolio based on different LO generation topologies, and to have a deep knowledge in how they can be used to meet demanding, future requirements on signal sources.

Features

One part of the programme is the development of different VCO MMIC designs and the other part is development of a PLL EM unit, including the PLL hybrid. The VCO development includes investigation of novel MMIC technologies to meet the demanding, future requirements of LO generation within 1-20 GHz. Technologies of interest and used in the technology trade off are GaN, InGaP and SiGe. The following is important for the performance of the VCO device.

Technology, noise characteristics and breakdown voltage of the active device.
Q factor of the resonator, also affected by the material in use.
The circuit topology.
For wideband designs, reduction of the varactor modulation noise.

The main challenge in this program is to extend the tuning range so that it can be covered with as few VCOs as possible. To mitigate the risk, several different VCOs are developed.

a) One narrow-band oscillator targeting minimum phase noise

b) Three medium bandwidth oscillators together covering the full PLL band

c) A wideband oscillator covering as much as possible of the PLL band

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.

Figure 1: Step 1 LO block diagram

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.