Prior art

Prior Art Analysis for U.S. Patent 10,651,866

An analysis of the prior art cited during the prosecution of U.S. Patent 10,651,866 reveals several key patents and applications that describe related technologies. The core of the '866 patent is the application of a fractional time delay to a digitally oversampled signal from a sensor before the signal is decimated to its baseband rate. This technique allows for very fine time-delay resolution, which is particularly advantageous for beamforming applications. The following prior art was considered by the USPTO examiner and is most relevant to the claims of the '866 patent.

Key Prior Art References

1. U.S. Patent No. 9,661,400 (Chabanne et al.)

• Full Citation: US 9,661,400 B2, "Method and a device for processing an audio signal captured by a microphone array," filed January 29, 2014; published May 23, 2017.
• Brief Description: This patent discloses a method for processing audio signals from a microphone array to create a directional capture. It involves applying a delay to the signals from different microphones before summing them. The delay is calculated to compensate for the time-of-arrival differences of a sound wave at each microphone, thereby "steering" the array's sensitivity in a specific direction. The patent discusses applying delays to achieve beamforming.
• Potential Anticipation of Claims: This reference is relevant to the general concept of using time delays for beamforming, as recited in claims 9-11 and 15-18 of the '866 patent, which are directed to beamforming applications. However, Chabanne et al. describes applying delays to the baseband signal after analog-to-digital conversion and decimation, not to the oversampled signal as taught in the '866 patent. This difference is a key distinguishing feature of the invention.

2. U.S. Patent No. 8,958,582 (Choi et al.)

• Full Citation: US 8,958,582 B2, "Method and apparatus for controlling beamforming," filed May 2, 2012; published February 17, 2015.
• Brief Description: Choi et al. describes an apparatus and method for beamforming that includes a delay unit for delaying an input signal. The system is designed to improve sound quality in devices like mobile phones by focusing on a sound source. This patent details the use of delay elements in a multi-microphone system to achieve directional sound pickup.
• Potential Anticipation of Claims: Similar to the '400 patent, this reference teaches the use of time delays for beamforming (relevant to claims 9-11 and 15-18). However, it does not explicitly disclose the application of these delays in the oversampled domain before decimation. The novelty of the '866 patent lies in performing this delay at a much higher sampling rate, which provides finer resolution than applying delays at the baseband rate.

3. U.S. Patent Application Publication No. 2011/0211718 A1 (Gieske et al.)

• Full Citation: US 2011/0211718 A1, "Fractional Delay for Beamforming with PDM Microphones," filed February 26, 2010; published September 1, 2011.
• Brief Description: This application is highly relevant as it explicitly discusses implementing fractional delays for beamforming with Pulse Density Modulated (PDM) microphones. PDM is a type of oversampling analog-to-digital conversion. Gieske et al. describe a method where a PDM signal is delayed and then filtered.
• Potential Anticipation of Claims: This publication appears to be the most pertinent prior art. It teaches the core concept of applying a delay to an oversampled (PDM) signal for beamforming purposes, which is central to independent claims 1 and 12 of the '866 patent. The key distinction, and likely the reason the '866 patent was granted over this reference, may lie in the specific implementation details of where the delay element is placed within the processing chain (e.g., before or between decimation/filtering stages) and the programmability of this delay, as detailed in the dependent claims of the '866 patent. For instance, the '866 patent describes in detail the placement of the delay element at various stages within a multi-stage PDM receiver module (FIGS. 5-7).

4. U.S. Patent No. 7,242,773 (Feng et al.)

• Full Citation: US 7,242,773 B2, "System and method for digital microphone interface and decimation filter," filed June 24, 2004; published July 10, 2007.
• Brief Description: This patent focuses on the interface and decimation filter for a digital microphone that outputs a one-bit, oversampled data stream (such as PDM). It describes the architecture of a PDM receiver module, including cascaded-integrator-comb (CIC) filters and other filter stages used to convert the oversampled signal to a baseband PCM signal.
• Potential Anticipation of Claims: This reference is relevant to the context of the PDM receiver module described in the '866 patent (e.g., element 280 in FIG. 2C and 314 in FIG. 3). It provides background on the standard components of such a system. However, Feng et al. does not teach or suggest the insertion of a programmable time delay element into the oversampled signal path for the purpose of beamforming. Therefore, it does not anticipate the core inventive concept of the '866 patent but rather describes the environment in which the invention operates.

Summary of Patentability

The patentability of US 10,651,866 appears to rest on the specific architectural choice of where to introduce a time delay in a digitally oversampled system. While the concept of using time delays for beamforming was well-established, and the use of oversampling digital microphones was also known, the '866 patent carves out a specific and efficient method for achieving highly precise, fractional time delays. By operating on the high-frequency, oversampled signal before it is decimated, the system can achieve a much finer delay resolution (a fraction of a baseband sample period) with simpler hardware (e.g., a small buffer) than would be required to implement a complex fractional delay filter on the baseband signal. The Gieske et al. application comes close to this concept, but the '866 patent's claims and specification provide a more detailed and flexible architecture, which was evidently sufficient to establish novelty and non-obviousness during examination.