Signal generator with coherent phase output
A signal generator and a method which provides a source signal with a coherent phase at arbitrary times is presented. There is provided a signal generator for generating a source signal based on a reference signal. The signal generator has a phase setting circuit with a memory circuit operable between a plurality of states. The memory circuit has a phase setting input adapted to receive a phase setting value to set the memory circuit to a known state. The signal generator is adapted to load the phase setting value at a specific time to control a phase of the source signal.
1. A signal generator for generating a source signal based on a reference signal, the signal generator comprising,
a phase setting circuit comprising a memory circuit operable between a plurality of states;
wherein the memory circuit comprises a phase setting input adapted to receive a pre-determined phase setting value to set the memory circuit to a known state;
wherein the source signal has a phase difference with respect to the reference signal;
wherein upon reset, the signal generator is adapted to load a selected pre-determined phase setting value at a specific time to set the phase difference to a chosen value, so that the phase of the source signal follows a chosen phase trajectory;
wherein the signal generator is operable between arbitrary periods in time, the arbitrary periods comprising a first period during which the signal generator provides a first source signal, and a second period during which the signal generator provides a second source signal;
wherein the signal generator further comprises a calculator configured to calculate the pre-determined phase setting value as a function of a time difference between a start of the first period and a start of the second period, a frequency of operation of the signal generator and a frequency of the reference signal.
2. The signal generator as claimed in claim 1 , wherein the signal generator comprises a signal circuit coupled to the phase setting circuit; the signal circuit being adapted to generate the source signal based on the reference signal.
3. The signal generator as claimed in claim 1 , wherein the pre-determined phase setting value is associated with a known phase difference between the reference signal and the source signal.
4. The signal generator as claimed in claim 1 , wherein between the first period and the second period the signal generator is deactivated and provides no source signal.
5. The signal generator as claimed in claim 1 , wherein the selected pre-determined phase setting value is based on a phase trajectory of the first source signal.
6. The signal generator as claimed in claim 1 , wherein upon loading the selected pre-determined phase setting value, the second source signal is set to the chosen phase trajectory.
7. The signal generator as claimed in claim 1 , wherein the memory circuit further comprises a data input for receiving a data signal, and a load input for receiving a load signal to load the selected pre-determined phase setting value from the phase setting input.
8. The signal generator as claimed in claim 1 , wherein the memory circuit further comprises a clock input for receiving a clock signal.
9. The signal generator as claimed in claim 7 , wherein the phase setting circuit further comprises an adder adapted to provide the data signal to the memory circuit.
10. A method of generating a source signal based on a reference signal, wherein the source signal has a phase difference with respect to the reference signal, the method comprising,
providing a signal generator with a phase setting circuit comprising a memory circuit operable between a plurality of states;
providing a pre-determined phase setting value associated with a known state of the memory circuit; and
upon reset of the signal generator, selecting and loading the pre-determined phase setting value into the memory circuit at a specific time to set the phase difference to a chosen value, so that the phase of the source signal follows a chosen phase trajectory;
wherein the signal generator is operable between arbitrary periods in time, the arbitrary periods comprising a first period during which the signal generator provides a first source signal, and a second period during which the signal generator provides a second source signal;
wherein the signal generator further comprises a calculator configured to calculate the pre-determined phase setting value as a function of a time difference between a start of the first period and a start of the second period, a frequency of operation of the signal generator and a frequency of the reference signal.
11. The method as claimed in claim 10 , wherein the pre-determined phase setting value is associated with a known phase difference between the reference signal and the source signal.
12. The method as claimed in claim 10 , wherein between the first period and the second period the signal generator is deactivated and provides no source signal.
13. The method as claimed in claim 10 , comprising identifying a phase trajectory of the first source signal and calculating the pre-determined phase setting value based on the first phase trajectory.
14. The method as claimed in claim 10 , wherein upon loading the selected pre-determined phase setting value, the second source signal is set to the chosen phase trajectory.
15. The method as claimed in claim 10 , wherein the memory circuit comprises a data input for receiving a data signal, and a load input for receiving a load signal to load the selected pre-determined phase setting value from the phase setting input.