Over-the-air calibration of antenna system
In an embodiment, an apparatus includes a first baseband section to receive a calibration signal; a first radio frequency (RF) section configured to generate a RF calibration signal based on modulating the calibration signal. The calibration signal comprises an orthogonal code based signal. The apparatus includes a second RF section to receive the RF calibration signal and generate a received calibration signal based on demodulating the RF calibration signal; a calibration section; a first antenna electrically coupled to the first RF section and configured to transmit the RF calibration signal; and a second antenna electrically coupled to the second RF section and configured to receive the RF calibration signal. The calibration section is configured to determine one or more of gain, baseband delay, or RF delay to calibrate the first RF section; and the second antenna is switchable between receiving the RF calibration signal and transmitting an encoded data signal.
1. An apparatus included in a communications system, the apparatus comprising:
a first baseband section configured to receive a calibration signal;
a first RF section configured to generate a RF calibration signal based on modulating the calibration signal, wherein the calibration signal comprises an orthogonal code based signal;
a second RF section configured to receive the RF calibration signal over-the-air and configured to generate a received calibration signal based on demodulating the RF calibration signal;
a calibration section;
a first antenna electrically coupled to the first RF section and configured to transmit the RF calibration signal; and
a second antenna electrically coupled to the second RF section and configured to receive the RF calibration signal, wherein:
the received calibration signal and a reference signal associated with the RF calibration signal comprise inputs to the calibration section;
the calibration section is configured to determine one or more of gain, baseband delay, or RF delay compensation values, based on the inputs, to calibrate the first RF section; and
the second antenna is switchable between receiving the RF calibration signal and transmitting an encoded data signal.
2. The apparatus of claim 1 , further comprising a waveform generator electrically coupled to the first baseband section and configured to generate and provide the calibration signal to the first baseband section.
3. The apparatus of claim 1 , wherein the calibration signal comprises a code division multiple access (CDMA) signal.
4. The apparatus of claim 1 , wherein calibration of the first RF section comprises one or more of gain, baseband delay, or RF delay offsets caused by one or both of the first RF section or the first antenna.
5. The apparatus of claim 1 , wherein the first and second antennas are included in a phased array antenna.
6. The apparatus of claim 1 , wherein the reference signal associated with the RF calibration signal comprises a combination of the calibration signal and an encoded data signal, wherein a data signal comprises a regular signal to be transmitted by the first RF section, and wherein the first baseband section is configured to encode the data signal to generate the encoded data signal and combine the encoded data signal with the calibration signal.
7. The apparatus of claim 1 , wherein the calibration section is configured to determine correlations based on the received calibration signal and one of the calibration signal or an output of the first baseband section associated with the RF calibration signal, wherein the calibration section is configured to determine initial gain and delay values based on the correlations, and wherein the calibration section is configured to determine a difference value based on the initial gain and delay values.
8. The apparatus of claim 7 , wherein if the difference value is within a pre-set value, then the initial gain and delay values comprise the one or more gain, baseband delay, or RF delay compensation values.
9. The apparatus of claim 7 , wherein if the difference value is greater than a pre-set value, then the calibration section is configured to iterate to determine new gain and delay values based on the initial gain and delay values, and wherein the calibration section is configured to determine a new difference value based on the new gain and delay values.
10. The apparatus of claim 9 , wherein if the new difference value is within the pre-set value, then the new gain and delay values comprise the one or more gain, baseband delay, or RF delay compensation values.
11. The apparatus of claim 9 , wherein if the new difference value is greater than the pre-set value, then the calibration section is configured to iterate to determine another new gain and delay values based on the new gain and delay values, and wherein the calibration section is configured to determine another new difference value based on the another new gain and delay values.
12. The apparatus of claim 1 , further comprising:
a second baseband section, wherein the second baseband section is configured to receive a second calibration signal; and
a third RF section wherein the third RF section is configured to generate a second RF calibration signal based on the second calibration signal, wherein:
the second calibration signal differs from the calibration signal in at least orthogonality;
the first RF section and the third RF section simultaneously transmit the RF calibration signal and the second RF calibration signal; and
the second RF section is configured to receive the second RF calibration signal over-the-air simultaneously with receiving the RF calibration signal, wherein the second RF section is configured to generate a received second calibration signal based on the second RF calibration signal.
13. The apparatus of claim 12 , wherein the received second calibration signal and a second reference signal associated with the second RF calibration signal comprise second inputs to the calibration section, and wherein the calibration section is configured to determine one or more of second gain, baseband delay, or RF delay compensation values, based on the second inputs, to calibrate the second RF section.
14. The apparatus of claim 1 , wherein the first RF section includes one or more IQ gain and phase compensators and one or more time delay filters, and wherein the one or more IQ gain and phase compensators is configured in accordance with the gain and RF delay compensation values and the one or more time delay filters is configured in accordance with the baseband delay compensation value to pre-compensate for gain and delay offsets associated with one or both of the first RF section or antenna electrically coupled to the first RF section.
15. The apparatus of claim 1 , wherein the reference signal comprises an output of the first baseband section.
16. The apparatus of claim 1 , wherein the reference signal comprises the calibration signal.
17. An apparatus included in a communications system, the apparatus comprising:
a baseband section configured to receive a calibration signal;
an RF section configured to generate a RF calibration signal based on modulating the calibration signal, wherein the calibration signal comprises an orthogonal code based signal, wherein the RF calibration signal is void of encoding by the baseband section;
a receive section configured to receive the RF calibration signal over-the-air, wherein the receive section includes a second RF section, wherein the second RF section is configured to generate a received calibration signal based on the RF calibration signal; and
a calibration section, wherein:
the received calibration signal and a reference signal associated with the RF calibration signal comprise inputs to the calibration section; and
the calibration section is configured to determine one or more of gain, baseband delay, or RF delay compensation values, based on the inputs, to calibrate the RF section.
18. The apparatus of claim 17 , further comprising:
wherein calibration of the receive section comprises one or more of gain, baseband delay, or RF delay offsets caused by one or both of the second RF section or an antenna coupled to the second RF section.
19. The apparatus of claim 18 , wherein the RF calibration signal is void of encoding by the baseband section.
20. The apparatus of claim 17 , wherein the calibration signal comprises a code division multiple access (CDMA) signal.