Software defined radio front end

• US 9,564,932 B1
• Filed: 12/29/2015
• Issued: 02/07/2017
• Est. Priority Date: 07/16/2015
• Status: Active Grant

• Current Assignee: LGS Innovations LLC (CACI International Incorporated)
• Original Assignee: LGS Innovations LLC (CACI International Incorporated)
• Inventors: Pack, Riley Nelson, Brannon, Alan Scott, Baker, Benjamin Joseph
• Primary Examiner(s): GONZALES, APRIL GUZMAN
• Application Number:
  US14/982,401
• Publication Number:
  US 20170019128A1
• Time in Patent Office: 406 Days
• Field of Search: 455/78
• US Class Current: 1/1
• CPC Class Codes: H03F 3/24 of transmitter output stages
• CPC Class Codes: H04B 1/0003 Software-defined radio [SDR] systems, i.e. systems wherein components typically implemented in hardware, e.g. filters or modulators/demodulators, are implented using software, e.g. by involving an AD or DA conversion stage such that at least part of the signal processing is performed in the digital domain digital baseband systems H04L25/00; digital modulation/demodulation H04L27/00; CDMA H04B1/707; TDMA H04B7/2643; image transmission H04N5/00
• CPC Class Codes: H04B 1/0042 Digital filtering H04B1/0035 takes precedence; digital filters per se H03H17/00
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04B 1/10 Means associated with receiver for limiting or suppressing noise or interference
• CPC Class Codes: H04B 1/1036 with automatic suppression of narrow band noise or interference, e.g. by using tuneable notch filters H04B1/123 takes precedence; filter circuits H03H
• CPC Class Codes: H04B 1/401 for selecting or indicating operating mode
• CPC Class Codes: H04B 1/525 with means for reducing leakage of transmitter signal into the receiver
• CPC Class Codes: H04B 1/713 using frequency hopping
• CPC Class Codes: H04B 1/715 Interference-related aspects
• CPC Class Codes: H04B 15/00 Suppression or limitation of noise or interference by means associated with receiver H04B1/10
• CPC Class Codes: H04B 15/02 Reducing interference from electric apparatus by means located at or near the interfering apparatus
• CPC Class Codes: H04B 2001/0408 with power amplifiers
• CPC Class Codes: H04L 25/0212 of impulse response
• CPC Class Codes: H04L 25/025 using least-mean-square [LMS] method
• CPC Class Codes: H04L 5/14 Two-way operation using the same type of signal, i.e. duplex
• CPC Class Codes: H04L 5/1461 Suppression of signals in the return path, i.e. bidirectional control circuits

Abstract

The present application describes a computer-implemented method for configuring a front end including sweeping a first tone through the frequency band of the receive channel; receiving a first signal and a second signal containing interference; characterizing the receive channel using the first tone; processing the compensated first signal using an infinite impulse response filter based on the characterized receive channel to generate an interference cancelling signal; and coupling the interference cancelling signal to the second signal to generate an interference cancelled receive signal.

Claims

1. A computer-implemented method for configuring a front end comprising:

sweeping a first tone through the frequency band of the receive channel;

receiving a first signal and a second signal containing interference;

characterizing the receive channel using the first tone;

processing the first signal using an infinite impulse response filter based on the characterized receive channel to generate an interference cancelling signal; and

coupling the interference cancelling signal to the second signal to generate an interference cancelled receive signal.

2. The method of claim 1, further comprising:

injecting a second tone generated by a tone generator at an edge of a frequency band of a receive channel; and

compensating the first signal for gain and phase imbalances within an IQ constellation of the first signal using the second tone.

3. The method of claim 2, further comprising:

injecting a third tone at the edge of the frequency band of the receive channel;

processing the third tone; and

modifying, in response to the processing the third tone step, the interference cancelling signal so that a phase and a magnitude of the interference cancelling signal matches an interference and a phase of the receive signal.

4. The method of claim 2, further comprising:

upconverting the second tone to overlay the frequency band of the receive channel for a given application of a radio access technology within a given band.

5. The method of claim 1, further comprising:

generating coefficients of the infinite impulse response filter using the receive channel characteristics to model the receive channel.

6. The method of claim 5, wherein the coefficients of the infinite impulse response filter are generated in conjunction with a least-squares estimator circuit.

7. The method of claim 5, wherein the generating step further comprises:

computing a least-squares approximation of the infinite impulse response coefficients;

computing a residual error of the least-squares approximation;

verifying that all poles of the infinite impulse response filter are stable; and

selecting coefficients that result in a lowest residual error.

8. A computer-implemented apparatus for a front end comprising:

an antenna configured to transmit and receive radio frequency signals;

a non-transitory storage medium configured to store computer-executable instructions; and

a processor operably coupled to the non-transitory storage medium and configured to execute the computer-executable instructions of;

injecting a first tone generated by a tone generator at an edge of a frequency band of a receive channel;

sweeping a first tone through the frequency band of the receive channel;

injecting the first tone in the frequency band of the receive channel;

receiving a first signal and a second signal containing interference;

compensating the first signal for gain and phase imbalances using the first tone;

characterizing the receive channel using the first tone; and

processing the compensated first signal using an infinite impulse response filter to generate an interference cancelling signal.

9. The apparatus of claim 8, wherein the computer-executable instructions further comprise:

injecting a second tone generated by a tone generator at an edge of a frequency band of a receive channel; and

compensating the first signal for gain and phase imbalances within an IQ constellation of the first signal using the second tone.

10. The system of claim 9, wherein the computer-executable instructions further comprise:

injecting a third tone at the edge of the frequency band of the receive channel;

processing the third tone; and

modifying, in response to the processing the third tone step, the interference cancelling signal so that a phase and a magnitude of the interference cancelling signal matches an interference and a phase of the receive signal.

11. The apparatus of claim 9, further comprising:

upconverting the second tone to overlay the frequency band of the receive channel for a given application of a radio access technology within a given band.

12. The apparatus of claim 8, further comprising:

generating coefficients of the infinite impulse response filter using the receive channel characteristics to model the receive channel.

13. The system of claim 12, wherein the coefficients of the infinite impulse response filter are generated in conjunction with a least-squares estimator circuit.

14. The system of claim 12, wherein the generating step further comprises:

computing a least-squares approximation of the infinite impulse response coefficients;

computing a residual error of the least-squares approximation;

verifying that all poles of the infinite impulse response filter are stable; and

selecting coefficients that result in a lowest residual error.

15. A method for configuring a front end comprising:

receiving a first signal;

sampling the first signal;

amplifying the first signal in a first pathway;

phase-shifting the sampled first signal in a second pathway;

adding the amplified first signal to the phase-shifted, sampled first signal to generate a carrier-cancelled signal; and

coupling the amplified first signal to the carrier-cancelled signal.

16. The method of claim 15, further comprising:

determining an optimal operating point based on a measured output power at the carrier-cancelled signal;

stepping a phase or a magnitude of the sampled transmit signal by one step of a first step size in a first direction; and

further stepping the phase or the magnitude in either the first direction or a second direction, based on the measured output power, wherein

if the measured output power is lower after the one step, stepping one more step in the first direction; and

if the measured output power is higher after the one step, stepping the phase or the magnitude by one step in the second direction.

17. The method of claim 16, wherein if the measured output power is higher after the step of the first step size in the first direction, changing the step of the first step in the first direction to a second step size, wherein the second step size is greater than the first step size.

18. The method of claim 16, wherein the phase of the sampled transmit signal is held constant first while stepping the magnitude of the sampled transmit signal and then stepping the phase of the sampled transmit signal while the magnitude of the sampled transmit signal is held constant.

19. The method of claim 15, further comprising:

coupling a plurality of tones generated by a tone generator to the carrier-cancelled signal.

20. The method of claim 15, further comprising:

amplifying the sampled transmit signal.