European Space Agency

13GHz Transceiver

Objectives

The contract originally specified design and development of an LNB/OMT/transmitter for operation at 13GHz receive and 12.75-13.25GHz transmit. A subsequent contract change note 001 re-specified the development of a revised version of the existing Invacom transmitter operating in the 14.0-14.5GHz band. The original TUL204 product was developed to meet the requirements of DVB-RCS systems.


The market requirement is increasingly for units to operate in custom VSAT return channel systems with different operating parameters and higher performance requirements in particular with regards to VCO Phase Noise, Gain Flatness and Output Noise. The new product is designated as TUL204E.

Challenges

10MHZ PLL

In the TUL204, the main 13.05GHz VCO is phase locked directly to this external 10MHz frequency reference supplied by the terminal IDU. As a consequence of this the transmitter LO phase noise is determined by the reference phase noise within the PLL bandwidth. In the TUL204E, an internal crystal oscillator is phase locked to the incoming reference using a loop with a relatively low bandwidth (40Hz compared with 30kHz for the main loop). The overall transmitter phase noise therefore becomes dependent on the characteristics of the internal crystal oscillator at frequency offsets greater than 100Hz or so and allows the new design to be operated with IDUs which do not provide a costly very low phase noise reference.

13.05GHz PLL

The existing 13.05GHz PLL has been re-developed for a considerable improvement in phase noise without major changes to the function of the circuits. Analysis of the main phase noise limitations in the loop showed that it would be possible to retain the existing L-band oscillator/5 x frequency multiplier scheme with modifications to the oscillator loading. This has meant no new methods for oscillator alignment have been required.

The PLL has however been completely re-designed. The current PLL IC has been replaced with a similar part from the same family which offers a lower phase detector noise floor but is otherwise functionally compatible with the original part. Circuit changes have arisen from the part's lower operating supply voltage range.

The loop parameters have also been optimised for minimum phase noise rather than transient response by increasing the phase margin.

The changes result in a typical phase noise improvement by >10dB over much of the spectrum - particularly the key 1kHz-100kHz region.

On Line Tuning

Achievement of the design goals of flatter gain against frequency response was made possi

Benefits

This new product the TUL204E has a number of performance benefits over the original TUL204 Transmitter. Most of these performance benefits have become necessary to take into account the technology differences of the TUL204 unit being designed specifically for DVB-RCS systems, and most systems now being deployed which tend to be proprietary. In general these proprietary systems typically have tighter requirements for Phase Noise, Output Noise and Gain Flatness.

Features

The following improvements have been made on the revised transmitter.



  1. Additional 10MHz PLL to lock an internal crystal reference oscillator to a terminal IDU reference multiplexed on the unit F-type connector,



  2. Improved 13.05GHz main PLL for lower phase noise,



  3. Revised and simplified IF strip for lower in band output noise,



  4. On line tuning for reduced gain ripple,



  5. Increased mixer dynamic range for improved manufacturability.


    Plan

    The project is divided into 5 Work Packages. These are :

    Electrical Design (WP1)

    Mechanical Design (WP2)

    Automatic Test System (WP3)

    Industrialisation (WP4)

    Project Admin and Control (WP5)

    Current status

    Electrical Design (WP1) - Activities Completed

    Mechanical Design (WP2) - Activities Completed

    Automatic Test System (WP3) - Activities Completed

    Industrialisation (WP4) - Activities Completed

    Project Admin and Control (WP5) - Activities Completed

    Status date

    Monday, July 13, 2009 - 13:38