Fieldbus transmitter interface, fieldbus receiver interface and system with both interfaces and coding method for a fieldbus transmitter interface

A fieldbus receiver interface for processing a primary signal, comprising:

• a receiver interface input;
• a first analog pre-filter;
• a second analog pre-filter;
• and
• a computing unit including an analog digital converter, a direct current deduction filter, and a quadrature demodulator.

A fieldbus interface, comprising:

• a fieldbus transmitter interface, including:
• a computing unit;
• a digital gate;
• an analog transmission filter;
• and a transmitter interface output,
• wherein the digital gate is connected to the analog transmission filter and the analog transmission filter is connected to the transmitter interface output,
• wherein the computing unit includes a pulse width modulator and a pulse width modulator clock that is suitable for generating a secondary signal that is coded by means of a duty cycle that is varied over time by the pulse width modulator clock, and wherein the pulse width modulator is suitable for superimposing the secondary signal with a carrier signal so that a digital transmission signal with a frequency of less than 150 kHz is generated,
• wherein the digital gate and the analog transmission filter are suitable for converting the digital transmission signal into an analog loop signal, and
• wherein the transmitter interface output is suitable for being connected to a remote station for transmitting the analog loop signal to the remote station;
• and
• a fieldbus receiver interface, including:
• a receiver interface input;
• a first analog pre-filter;
• a second analog pre-filter;
• and
• a computing unit including an analog digital converter, a direct current deduction filter, and a quadrature demodulator.

A system, comprising:

• a fieldbus transmitter interface, including:
• a computing unit;
• a digital gate;
• an analog transmission filter;
• and a transmitter interface output,
• wherein the digital gate is connected to the analog transmission filter and the analog transmission filter is connected to the transmitter interface output,
• wherein the computing unit includes a pulse width modulator and a pulse width modulator clock that is suitable for generating a secondary signal that is coded by means of a duty cycle that is varied over time by the pulse width modulator clock, and wherein the pulse width modulator is suitable for superimposing the secondary signal with a carrier signal so that a digital transmission signal with a frequency of less than 150 kHz is generated,
• wherein the digital gate and the analog transmission filter are suitable for converting the digital transmission signal into an analog loop signal, and
• wherein the transmitter interface output is suitable for being connected to a remote station for transmitting the analog loop signal to the remote station;
• and
• a fieldbus receiver interface, including:
• a receiver interface input;
• a first analog pre-filter;
• a second analog pre-filter;
• and
• a computing unit including an analog digital converter, a direct current deduction filter, and a quadrature demodulator,
• wherein the fieldbus transmitter interface and the fieldbus receiver interface are interconnected via a current loop.

A coding method for a fieldbus transmitter interface of a field device or of a control center, comprising:

• providing a fieldbus transmitter interface, including:
• a computing unit;
• a digital gate;
• an analog transmission filter;
• and a transmitter interface output,
• wherein the digital gate is connected to the analog transmission filter and the analog transmission filter is connected to the transmitter interface output,
• wherein the computing unit includes a pulse width modulator and a pulse width modulator clock that is suitable for generating a secondary signal that is coded by means of a duty cycle that is varied over time by the pulse width modulator clock, and wherein the pulse width modulator is suitable for superimposing the secondary signal with a carrier signal so that a digital transmission signal with a frequency of less than 150 kHz is generated,
• wherein the digital gate and the analog transmission filter are suitable for converting the digital transmission signal into an analog loop signal, and
• wherein the transmitter interface output is suitable for being connected to a remote station for transmitting the analog loop signal to the remote station;
• generating a digital representation of the secondary signal as a duty cycle sequence by the computing unit;
• transmitting the digital representation of the secondary signal to the pulse-width modulator;
• converting the digital representation of the secondary signal by the pulse width modulator into a digital transmitter signal having a duty cycle that varies over time and having a frequency of less than 150 kHz;
• generating an analog loop signal by a digital gate based on the digital signal;
• and
• providing the analog loop signal at the transmitter interface output.