Perturbation-based dynamic measurement of antenna impedance in real-time
View Patent ↗Devices and methods are disclosed for real-time calibration of a tunable matching network that matches the dynamic impedance of an antenna in a receiver. Processing logic is operable to solve multiple non-linear equations to determine the reflection coefficient of the antenna. The tunable matching network is repeatedly perturbed and the power received by the antenna is measured after each perturbation at the same node in the matching network. The measured power values are used by an optimizer in converging to a solution that provides the reflection coefficient of the antenna. The reflection coefficient of the antenna may be used to determine the input impedance of the antenna. The elements of the matching circuit may then be adjusted to match the input impedance of the antenna.
1. A wireless communications system, comprising:
an antenna;
a matching circuit coupled to said antenna, said matching circuit having an operating frequency;
a control system operable to calculate, in real-time, a value for an input impedance of the antenna, wherein said input impedance is calculated based on a first received power measurement corresponding to said matching circuit tuned at said operating frequency, a second received power measurement corresponding to said matching circuit tuned at a first perturbed frequency equal to the operating frequency minus a frequency perturbation step interval, and a third received power measurement corresponding to said matching circuit tuned at a second perturbed frequency equal to the operating frequency plus the frequency perturbation step interval.
2. The wireless communications system of claim 1 , wherein said first, second, and third received power measurements, respectively, each comprise the total received power.
3. The wireless communications system of claim 1 , wherein said first, second, and third received power measurements, respectively, each correspond to a desired user power.
4. The wireless communications system of claim 1 , wherein one of said first, second, and third received power measurements are obtained by averaging a collective set of power measurements.
5. The wireless communications system of claim 1 , wherein said matching network is tunable by the control system to match the calculated values of the input impedance of the antenna to a load on a receiver in said communication system.
6. The wireless communications system of claim 1 , wherein said matching network comprises reactive components having fixed values.
7. The wireless communications system of claim 1 , wherein said first, second, and third received power measurements are normalized to compensate for received power variations corresponding to spectral power densities for the measurement frequencies for each of the three respective power measurements.
8. The wireless communications system of claim 1 , wherein said frequency perturbation step interval is implemented by controlling the frequency generated by a local oscillator in a detector of a receiver, prior to the baseband stage, in said communication system.
9. The wireless communications system of claim 8 , wherein the power sensing of said first, second, and third received power measurements, respectively, is performed at the baseband frequency of the receiver in said communication system.
10. A method for processing signals received on a wireless communications system, the method comprising:
receiving a signal on an antenna coupled to said wireless communication system;
providing said received signal to a matching circuit coupled to said antenna, said matching circuit having an operating frequency; and
using a control system operable to calculate, in real-time, a value for an input impedance of the antenna to match a load in a receiver system, wherein said input impedance is calculated based on a first received power measurement corresponding to said matching circuit tuned at said operating frequency, and a second received power measurement corresponding to said matching circuit tuned at a first perturbed frequency equal to the operating frequency minus a frequency perturbation step interval, and a third received power measurement corresponding to said matching circuit tuned at a second perturbed frequency equal to the operating frequency plus the frequency perturbation step interval.
11. The method of claim 10 , wherein said matching network is tunable by the control system to match the calculated values of the input impedance of the antenna to a load on a receiver in said communication system.
12. The method of claim 10 , wherein said matching network comprises reactive components having fixed values.
13. The method of claim 12 , wherein said first, second, and third received power measurements are normalized to compensate for received power variations corresponding to spectral power densities for the measurement frequencies for each of the three respective power measurements.
14. The method of claim 10 , wherein said frequency perturbation step interval is implemented by controlling the frequency generated by a local oscillator in a detector of a receiver, prior to the baseband stage, in said communication system.
15. The method of claim 14 , wherein the power sensing of said first, second, and third received power measurements, respectively, is performed at the baseband frequency of the receiver in said communication system.
16. A wireless communications system, comprising:
an antenna;
a matching circuit coupled to said antenna, said matching circuit having an operating frequency;
a control system operable to calculate, in real-time, a value for an input impedance of the antenna using first, second and third power parameters corresponding to first, second and third received power measurements, wherein:
said first power parameter corresponds to a received power measurement obtained with said matching circuit being tuned at said operating frequency and a reactive component in said matching circuit having a first reactive component value;
said second power parameter corresponds to a received power measurement obtained with said matching circuit operating at perturbed frequencies corresponding to one of the operating frequency minus a frequency perturbation step interval or the operating frequency plus the frequency perturbation step interval; and
said third power parameter corresponds to a received power measurement obtained with said matching circuit operating with said reactive component having a value equal to said first reactive component value plus an incremental reactive component value.
17. The wireless communications system of claim 16 , wherein said matching network is tunable by the control system to match the calculated values of the input impedance of the antenna to a load on a receiver in said communication system.
18. The wireless communications system of claim 16 , wherein said first, second, and third power parameters are normalized to compensate for received power variations corresponding to spectral power densities for the measurement frequencies for each of the three respective power measurements.
19. The wireless communications system of claim 16 , wherein said frequency perturbation step interval is implemented by controlling the frequency generated by a local oscillator in a detector of a receiver, prior to the baseband stage, in said communication system.
20. The wireless communications system of claim 19 , wherein the power sensing of said first, second, and third power parameters, respectively, is performed at the baseband frequency of the receiver in said communication system.