A method for compensating signal distortion in an emitting payload

Description of the offer:

The European Space Agency proposes an innovation related to a method for compensating signal distortion in an emitting payload by introducing a suitable pre-distortion or compensation transfer function within the aggregate response of the payload. Pre-distorting signals of a payload in order to compensate for payload-induced linear and/or nonlinear distortion is known in the art of telecommunications. These compensation functions are often contained inside one of the onboard equipments, i.e. a linearizer in an RF high power amplifier, typically providing nonlinear reduction, or an equalizer comprising a tunable filter stage, providing linear response flattening in the frequency domain. Determining a suitable compensation transfer function requires the simultaneous knowledge of an input signal of the payload and of the corresponding output signal. Measuring an input signal, however, is not always expedient, particularly in the case of a generative payload. In fact, generative payloads internally generate their own input signal; accessing this input signal requires the mounting of couplers inside the payload, which adds weight, calibration errors and complexity, and which also generates access constraints in general (e.g. physical intervention by a test engineer, opening/re-closing manipulation of access panels or umbilicals in order to reach the measurement points, mating/de-mating of connectors). An aim of this new innovation is to provide a method of compensating signal distortion in an emitting payload, without the need of acquiring an input signal of the payload. Furthermore a distortion compensation method is provided which is simple to implement and robust against individual payload element (equipment) parameter drifts and tolerances of individual payload elements. Finally also a flexible distortion compensation method is provided, working with almost any signal modulation constellation and making minimal assumptions on the signal and payload characteristics, such distortion compensation method can be carried out during operation of the payload, without the need of interrupting service.

Innovations and advantages:

This method is able to compensate signal distortion in an emitting payload, and it comprises determining a compensation transfer function, introducing it within the aggregate response of the payload. The method is characterized by the following advantages with respect to other solutions:

1. It chooses an initial tentative compensation transfer function and introduces it within the aggregate response of the payload;
2. Acquires an output signal of the emitting payload;
3. It is based on such acquired output signal and on a reference signal;
4. It is based on an estimation of the residual distortion transfer function, computing an updated tentative compensation transfer function and introducing it within the aggregate response of the payload.

Domain of Application:

This invention is particularly well suited for generative payloads, and more particularly for navigation payloads, but it is not limited to this particular field. It can also be applied, for example, to telecommunication payloads for optimizing Inter-Symbol Interference, and to synthetic aperture radar payloads for reducing ranging estimation biases. It may also be applied more generally to telecom systems.