Calibration sub-system for telecommunication systems
A calibration sub-system for calibrating a unit of a distributed antenna system is provided. The calibration sub-system includes a signal generator, a receiver, and a processor. The signal generator provides test signals to a communication path that are generated based on modification schemes for an in-phase signal component (“I component”) or a quadrature signal component (“Q component”). The receiver receives output signals generated from test signals. The processor determines output power values for an undesirable signal component of the output signals. Each output power value is a Taylor series function or a polynomial function of a respective modification scheme for the I or Q component of the respective test signal. The processor determines an optimal modification scheme for the I or Q component that minimizes an output power of the undesirable signal component. An output value of the function is minimized by having the optimal modification scheme as an input.
1. A calibration sub-system for calibrating a unit of a distributed antenna system comprising:
a signal generator configured to provide a plurality of test signals to a communication path of the unit, wherein each of the plurality of test signals is generated based on a respective one of a plurality of modification schemes for at least one of an in-phase signal component and a quadrature signal component;
a receiver disposed in the communication path of the unit, the receiver configured to receive a plurality of output signals generated using the plurality of test signals; and
a processor communicatively coupled to the signal generator and the receiver, wherein the processor is configured to:
for each modification scheme of the plurality of modification schemes, determine a respective output power value for at least one undesirable signal component of a respective output signal received by the receiver, wherein the respective output power value is a function of the modification scheme for the in-phase signal component or the quadrature signal component of a respective test signal, the function being at least one of a Taylor series function or a polynomial function, and
determine an optimal modification scheme for at least one of the in-phase signal component and the quadrature signal component such that an output power of the at least one undesirable signal component is minimized, wherein applying the function having the optimal modification scheme as an input minimizes an output value of the function.
2. The calibration sub-system of claim 1 , wherein the plurality of modification schemes comprises a plurality of first values for an offset of the in-phase signal component and a plurality of second values for an offset of the quadrature signal component.
3. The calibration sub-system of claim 2 , wherein the processor is configured to determine the optimal modification scheme for the in-phase signal component or the quadrature signal component by minimizing the output value of the function such that a local oscillator leakage power is minimized.
4. The calibration sub-system of claim 1 , wherein the plurality of modification schemes comprises a plurality of first values for a gain of the in-phase signal component and a plurality of second values for a gain of the quadrature signal component.
5. The calibration sub-system of claim 4 , wherein the plurality of modification schemes further comprises a quadrature-mixing phase difference between the in-phase signal component and the quadrature signal component.
6. The calibration sub-system of claim 5 , wherein the processor is configured to determine the optimal modification scheme for the in-phase signal component or the quadrature signal component by minimizing the output value of the function such that a sideband image power is minimized.
7. The calibration sub-system of claim 1 , wherein the processor is further configured to determine the optimal modification scheme by:
selecting a first testing modification scheme;
determining a first optimal modification scheme for at least one of the in-phase signal component and the quadrature signal component based on the first testing modification scheme, wherein applying the function using the first optimal modification scheme provides a first minimum output value of the function;
selecting a second testing modification scheme based on the first optimal modification scheme;
determining a second optimal modification scheme from the second testing modification scheme.
8. The calibration sub-system of claim 1 , wherein the unit further comprises a digital-to-analog conversion device communicatively coupled to the processor, wherein the processor is further configured to:
generate control signals directing the digital-to-analog conversion device to implement the optimal modification scheme; and
provide the control signals to the digital-to-analog conversion device.
9. The calibration sub-system of claim 1 ,
wherein the signal generator is further configured to modulate the plurality of test signals with identifier data,
wherein the processor is configured to distinguish the plurality of output signals from interfering signals based on the identifier data.
10. The calibration sub-system of claim 1 ,
wherein the signal generator is further configured to generate each of the plurality of test signals with a frequency wobble, wherein the frequency wobble comprises a temporary change in a respective frequency of each of the plurality of test signals;
wherein the receiver is synchronized with the frequency wobble;
wherein the processor is configured to distinguish the plurality of output signals from interfering signals based on the frequency wobble.
11. A method for calibrating a unit of a distributed antenna system comprising:
selecting at least one of an in-phase signal component and a quadrature signal component affecting an output power of an undesirable output signal component;
selecting a plurality of modification schemes for the in-phase signal component or the quadrature signal component;
providing a plurality of test signals respectively generated based on the plurality of modification schemes to a communication path of the unit;
for each of a plurality of output signals generated using the plurality of test signals, determining a respective output power, wherein the respective output power value is a function of the respective modification scheme for the in-phase signal component or the quadrature signal component of the respective test signal used to generate the output signal, the function being at least one of a Taylor series function or a polynomial function; and
determining an optimal modification scheme for the in-phase signal component or the quadrature signal component such that the output power of at least one undesirable signal component is minimized, wherein applying the function having the optimal modification scheme as an input minimizes an output value of the function.
12. The method of claim 11 , wherein the plurality of modification schemes comprises a plurality of first values for an offset of the in-phase signal component and a plurality of second values for an offset of the quadrature signal component.
13. The method of claim 12 , wherein determining the optimal modification scheme for the in-phase signal component or the quadrature signal component comprises minimizing the output value of the function such that a local oscillator leakage power is minimized.
14. The method of claim 11 , wherein the plurality of modification schemes comprises a plurality of first values for a gain of the in-phase signal component and a plurality of second values for a gain of the quadrature signal component.
15. The method of claim 14 , wherein the plurality of modification schemes further comprises a quadrature-mixing phase difference between the in-phase signal component and the quadrature signal component.
16. The method of claim 15 , wherein determining the optimal modification scheme for the in-phase signal component or the quadrature signal component comprises minimizing the output value of the function such that a sideband image power is minimized.
17. The method of claim 11 , wherein determining the optimal modification scheme comprises:
selecting a first testing modification scheme;
determining a first optimal modification scheme for at least one of the in-phase signal component and the quadrature signal component based on the first testing modification scheme, wherein applying the function using the first optimal modification scheme provides a first minimum output value of the function;
selecting a second testing modification scheme based on the first optimal modification scheme;
determining a second optimal modification scheme from the second testing modification scheme.
18. The method of claim 11 , further comprising configuring a digital-to-analog conversion device of the unit to implement the optimal modification scheme.
19. The method of claim 11 , further comprising:
modulating the plurality of test signals with identifier data,
distinguishing the plurality of output signals from interfering signals based on the identifier data.
20. The method of claim 11 , further comprising:
generating each of the plurality of test signals with a frequency wobble, wherein the frequency wobble comprises a temporary change in a respective frequency of each of the plurality of test signals;
distinguishing the plurality of output signals from interfering signals based on the frequency wobble.