DIGITAL REPEATER HAVING BANDPASS FILTERING, ADAPTIVE PRE-EQUALIZATION AND SUPPRESSION OF NATURAL OSCILLATION

• US 20140119411A1
• Filed: 01/06/2014
• Published: 05/01/2014
• Est. Priority Date: 11/12/2001
• Status: Active Grant

• Current Assignee: Strong Force IoT Portfolio 2016, LLC (Strong Force Intellectual Capital, LLC)
• Original Assignee: Andrew Wireless Systems GmbH (CommScope Holding Company, Inc.)
• Inventors: Kummetz, Thomas
• Granted Patent: US 9,203,503 B2
• Time in Patent Office: Days
• US Class Current: 375/211
• CPC Class Codes: H04B 7/15585 by interference cancellation

Abstract

A signal repeating system includes at least one input antenna that receives input signals, at least one output antenna that radiates output signals, and a signal path between the input and output antennas. The signal path includes circuitry for conditioning the input signals with down conversion circuitry that converts input signals to lower frequency signals and analog-to-digital conversion circuitry that converts the input signals to digital signals. A suppression circuit suppresses feedback and interference in the repeated output signals with a digital signal processor configured for receiving samples of the input signals, samples of the output signals, and samples of an interference reference signal and an adaptive filter under the control of the digital signal processor for generating echo cancellation signals and interference cancellation signals.

Claims

1. A signal repeating system, comprising:

at least one input antenna that receives input signals, at least one output antenna that radiates output signals, and a signal path between the input and output antennas;

the signal path including;

down conversion circuitry that converts input signals to lower frequency signals and analog-to-digital conversion circuitry that converts the input signals to digital signals;

a suppression circuit for suppressing feedback and interference in the repeated output signals, the suppression circuit including;

a digital signal processor configured for receiving samples of the input signals, samples of the output signals, and samples of an interference reference signal;

an adaptive filter coupled with the digital signal processor, the adaptive filter configured, under the control of the digital signal processor, for generating cancellation signals;

the digital signal processor configured for computing a correlation between the input signals and output signals and creating control signals for the adaptive filter to generate echo cancellation signals;

the digital signal processor further configured for computing a correlation between the interference reference signal and the output signals and creating control signals for the adaptive filter to generate interference cancellation signals;

combining circuitry for destructively adding the echo cancellation signals and the interference cancellation signals to the input signals for reducing echo and interference in the output signals of the signal repeating system;

digital-to-analog conversion circuitry that converts the output signals to analog signals and up conversion circuitry that converts output signals to higher frequency signals.

2. The signal repeating system of claim 1, wherein the adaptive filter includes an adaptive FIR filter programmed by the digital signal processor.

3. The signal repeating system of claim 1 further comprising switching circuitry communicating with said FIR filter and the DSP processor to switch between an echo cancellation mode and an interference cancellation mode.

4. The signal repeating system of claim 1 wherein the digital signal processor is configured for estimating a transfer function of an echo feedback path in the system and computing an inverse transfer function and associated adaptive filter coefficients for generating the echo cancellation signals.

5. The signal repeating system of claim 1, wherein the digital signal processor is further configured to control the adaptive filter to generate interference cancellation signals that have a similar amplitude and an inverted phase relative to interference experienced by the system.

6. The signal repeating system of claim 1, wherein the digital signal processor is further configured to determine a time delay for the generated cancellation signals that are added to the input signals.

7. The signal repeating system of claim 1 further comprising a feedback path configured to continuously capture samples of the output signals and direct the samples to the digital signal processor.

8. The signal repeating system of claim 1 further comprising switching circuitry for switching the feedback path to capture samples of the output signals in different frequency bands so the signal repeating system can reduce echo and interference in the output signals of the repeater system in various frequencies.

9. A method for conditioning a signal in a signal repeating system, comprising:

receiving input signals, conditioning the signals in a signal path and transmitting the output signals;

the step of conditioning the input signals including;

down converting the signals to lower frequency signals and converting the input signals to digital signals;

suppressing feedback and interference in the repeated output signals, including;

processing, with a digital signal processor, samples of the input signals, samples of the output signals, and samples of an interference reference signal;

generating cancellation signals with an adaptive filter under the control of the digital signal processor using the sampled input and output signals and interference reference signal;

the generation of the cancellation signals including at least one of;

computing a correlation between the input signals and output signals and creating control signals for the adaptive filter to generate echo cancellation signals, or computing a correlation between the interference reference signal and the output signals and creating control signals for the adaptive filter to generate interference cancellation signals;

destructively adding at least one of the echo cancellation signals and the interference cancellation signals to the input signals for reducing at least one of echo or interference in the output signals of the signal repeating system;

converting the output signals to analog signals and up converting the output signals to higher frequency signals to be transmitted.

10. The method of claim 9, wherein the adaptive filter includes an adaptive FIR filter programmed by the digital signal processor.

11. The method of claim 9 further comprising switching between an echo cancellation mode and an interference cancellation mode by switching the signals to the digital signal processor between samples of the input signals, samples of the output signals, and samples of an interference reference signal.

12. The method of claim 9 further comprising estimating a transfer function of an echo feedback path in the system and computing an inverse transfer function and associated adaptive filter coefficients for generating the echo cancellation signals.

13. The method of claim 9, further comprising controlling the adaptive filter to generate interference cancellation signals that have a similar amplitude and an inverted phase relative to interference experienced by the system.

14. The method of claim 9, further comprising, with the digital signal processor, determining a time delay for the generated cancellation signals that are added to the input signals.

15. The method of claim 9 further comprising continuously capturing samples of the output signals and directing the samples to the digital signal processor.

16. The method of claim 9 further comprising switching to capture samples of the output signals in different frequency bands to reduce echo and interference in the output signals of the repeater system in various frequencies.