Apparatus and method for suppresion of TDMA noise in a...

Details Apparatus and method for suppresion of TDMA noise in a... Apparatus and method for suppresion of TDMA noise in a...

2007-10-25

2010-10-26

Jackson, Blane J (Department: 2618)

Telecommunications

Receiver or analog modulated signal frequency converter

Noise or interference elimination

C381S074000, C381S309000, C381S071100

Reexamination Certificate

active

07822400

ABSTRACT:
A circuit for TDMA noise reduction is provided, which may be used in a mobile phone. The circuit includes a first audio amplifier, a second audio amplifier, and a switch. The circuit is attachable to a stereo headphone with two speakers, each speaker having two inputs. The first speaker has one input that is coupled to one input of the second speaker. The other input of each speaker is coupled to a corresponding audio amplifier. During a talk mode for the mobile phone, the common input of the two speakers is left floating. In this mode, the TDMA noise is substantially cancelled, and the sound is differential monophonic. When the mobile phone is not in a talk mode, the common input of the speakers is driven to Vdd/2 or ground, so that the sound is stereophonic.

REFERENCES:
patent: 6278786 (2001-08-01), McIntosh
patent: 7065219 (2006-06-01), Abe et al.
patent: 2001/0046304 (2001-11-01), Rast
patent: 2006/0013410 (2006-01-01), Wurtz
patent: 2009/0225999 (2009-09-01), Lee
LM4949 Steroe Class D Audio Subsystem with OCL Headphone Amplifier, National Semiconductor Corporation, Jan. 2007, 42 pgs.
LM4946, Output Capacitor-Less Audio Subsystem with programmable National 3D, National Semiconductor Corporation, Jun. 2007, 34 pgs.
LM4937 Audio Subsystem with OCL Stereo Headphone Output and RF Suppression, National Semiconductor Corporation, Aug. 2007, 42 pgs.
LM4947 Mono Class D and Stereo Audio Subsystem with OCL Headphone Amplifier and National 3D, National Semiconductor Corporation, Nov. 9, 2007, 34 pgs.

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