Apparatus and method for compensating for limiter induced non-linear distortion in a wireless data communication system
US5533048A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Feb 17, 1994 |
| Grant date | Jul 2, 1996 |
| Priority date | — |
| Expiry date | Feb 17, 2014 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L1/0026
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
A system and method for reducing amplitude distortion in data signals transmitted via cellular analog communication systems are embodied in several forms. In one embodiment, pre-emphasis and de-emphasis functions of the cellular system are offset by complementary de-emphasis and post-emphasis circuits to preclude clipping of high frequency components of the data signal by the limiter. Alternatively, the limiter circuit is selectively bypassed when a data signal is transmitted. Alternatively, a pilot tone is combined with the incoming data signal. The amplitude of the pilot tone is constant and always sets the gain of the limiter, thereby keeping the gain of the limiter circuit constant. Alternatively, a pair of signals at different frequencies are transmitted on a telephone line, and the relative amplitudes of the return echoes are measured to determine the frequency roll-off of the line and adjust the spectral shaping accordingly. Alternatively, a pair of modems vary their respective spectral characteristics until the eye quality values of the two modems are satisfactory. Alternatively, a receiving modem performs an auto-equalization routine which varies to ignore outer points on …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.