E6-band SSPA for Galileo Navigation Payload
Darbandi-Tehrani, A; Zoyo, M; Touchais, J. Y.
Thales Alenia Space

Abstract - Incoming generation of positioning systems such as Galileo navigation system are expected to provide a wide range of applications. This implies an innovative system design towards increased accuracy, enhanced resolution and 100% availability. Today, the main constraints on the power amplifiers are: very high output power, high linearity and very high DC to RF efficiency. The optimum solution found is based on three high power highly efficient modules in parallel associated with a linearizer, in order to achieve the required output power and the linearity.
This design offers efficiency greater than 36% with a reliable SSPA for space applications.

INTRODUCTION In the present navigation satellite constellations, Solid State Power Amplifiers (SSPA) have been in use as high power radio frequency (RF) signal amplifiers. The recent famous system is enhanced WAAS navigation payload (Wide Area Augmentation System) in association with the GPS signal to locate the precise position of the aircrafts. Thales Alenia Space have designed and constructed advanced L1 and L5 solid state power amplifiers that provided the output power of 60W and 40W for this application [1]. These L-band SSPAs are used to relay GPS information to in-flight aircraft, providing a high accurate guidance to pilots at thousands of airports and airstrips where there is currently no precision landing capabilities.
In incoming generation of positioning system such as Galileo, the spatial resolution is increased drastically with a complex modulated signal. Therefore there is a need for high output power and linear SSPA.
In this paper, we describe the design and performance of high efficient SSPAs that will be used in the navigation and aero-communication applications.

SSPA DESIGN
The E6-band SSPA is composed of two main trays:
An RF tray, consisting of an RF chain and a control PCB mounted in the lower mechanical structure,
A DC tray, consisting of an Electronic Power Conditioner PCB (EPC) mounted in the upper structure.
The EPC is designed and is manufactured by Galileo Avionica in Italy. The simplified block diagram of E6 SSPA is shown in figure 1.

Fig. 1: Simplified E6 SSPA block diagram

The RF chain consists of two variable gain modules, a driver gain stage, three parallel high power amplifier modules and an output isolator.
The control PCB is dedicated to temperature compensation, overdrive protection circuitry, gain compensation function and TM/TC signals processing.
The RF tray provides more than 60dB of gain, 74W of output power for the Galileo E6 complex signal, with the associated efficiency greater than 36%.
The main function of the EPC is to convert the primary power input into the required secondary output voltage for supplying the SSPA RF-parts. It can achieve the DC to DC efficiency of higher than 89%. The EPC also manages the TTC interfaces with the satellite bus.

SSPA Performance
The measured electrical performance of the E6-band breadboard model SSPA (EBB) at central frequency and at ambient temperature for a CW signal is given in figure 2. It should be underlined that, because the SSPA is tuned to operate with a modulated signal, this results to a limitation of the output power for CW signal (@1dB of gain compression). With this tuning configuration this SSPA can provide output power higher than 49.5dBm with the associated efficiency greater than 40% at 1 dB of gain compression.

Fig. 2: Measured Po & Efficiency of E6-band SSPA (CW signal)

The measured electrical performance of the E6-band SSPA (EBB) under the complex modulated excitation signal at ambient temperature is given in figure 3.The SSPA can deliver output power higher than 48.7dBm with the associated efficiency greater than 38% at nominal operating point.

Fig. 3: Measured Po & Efficiency of E6-band SSPA (complex modulated signal)