发明名称 |
Audio circuit and method for wideband to narrowband transition in a communication device |
摘要 |
A subscriber unit moving from a cell where a wideband speech channel (e.g. 8kHz) is utilised to a cell where a narrowband speech channel (e.g. 4kHz) is utilised usually experiences an immediately perceivable deterioration in audio signal quality output. This is overcome by generating a pseudo wideband signal from the received narrowband signal by analysing (68) formant components of the received signal, or by duplicating the narrowband spectral profile and reflecting (74) the profile about the narrowband Nyquist point. In the former respect, low frequency components are matched (70) against low frequency signal profiles stored in a database, and associated high frequency components are added to complete the speech signal in a manner equivalent to an 8kHz channel. During a transition period, the pseudo wideband signal is progressively band-limited (80) to the narrowband signal of the currently occupied cell. |
申请公布号 |
GB2357682(B) |
申请公布日期 |
2004.09.08 |
申请号 |
GB19990030572 |
申请日期 |
1999.12.23 |
申请人 |
* MOTOROLA LIMITED;* MOTOROLA LIMITED |
发明人 |
JONATHAN * GIBBS;DOMINIC SAI FAN * CHAN |
分类号 |
G10L21/02;(IPC1-7):G10L21/02 |
主分类号 |
G10L21/02 |
代理机构 |
|
代理人 |
|
主权项 |
|
地址 |
|