Shigeru Iizuka

Title: Shigeru Iizuka: Innovator in Echo Cancellation Technology

Introduction

Shigeru Iizuka is a prominent inventor based in Saitama, Japan. He has made significant contributions to the field of telecommunications, particularly in echo cancellation technology. With a total of 3 patents to his name, Iizuka's work has had a lasting impact on the industry.

Latest Patents

One of Iizuka's latest patents is an echo canceller using two residual echoes. This innovative design incorporates a PCM interface used in PCM telephone circuits. The echo estimator is coupled with a receive path through a linear code converter to obtain a linear receive input signal. A first subtractor is inserted in the transmit path to cancel the echo component in the linear transmit input signal, transmitting a first residual echo to the far-end talker. A non-linear quantization processor is also included, which produces a new echo estimate containing quantization noise. This new estimate can effectively cancel both the echo and quantization noise without affecting the performance of the echo estimator. The design achieves high echo return loss enhancement, even for multi-linked PCM channels.

Another notable patent is a speech signal coding/decoding system based on the type of speech signal. In this system, an input speech signal is encoded by an adaptive quantizer that quantizes the predicted residual signal. The system includes an inverse quantizer for noise shaping and local decoding. A noise shaping filter is employed to make the spectrum of the quantization noise similar to that of the original digital input speech signal. The shaping factors are adjusted based on the prediction gain, ensuring optimal performance during both encoding and decoding.

Career Highlights

Shigeru Iizuka works at Kokusai Denshin Denwa Co., Ltd., where he continues to innovate in the field of telecommunications. His expertise in echo cancellation and speech signal processing has positioned him as a key figure in his company and the industry at large.

Collaborations

Iizuka has collaborated with notable coworkers such as Takahiro Nomura and Yohtato Yatsuzuka. Their combined efforts have contributed to advancements in telecommunications technology.

Conclusion

Shigeru Iizuka's contributions to echo cancellation technology and speech signal processing have made him a significant figure in the telecommunications industry. His innovative patents reflect his dedication to improving communication systems, and his