Image-rejection I/Q demodulators
US6560449B1 · kind B1 · utility
Assignee
Inventor
Key dates
| Filing date | Jun 12, 2000 |
| Grant date | May 6, 2003 |
| Priority date | — |
| Expiry date | Feb 5, 2021 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L2027/0024
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
In a communications receiver for quadrature demodulation, a feedback technique for reducing the image response of the receiver. The communications receiver includes an I demodulator and a Q demodulator. A local oscillator (LO) signal is provided by a PLL to a quadrature LO generator that provides an LO_I signal to an I demodulator and an LO_Q signal to a Q demodulator. The LO_I and LO_Q signals are amplitude and phase-controlled versions of the LO signal. An image/signal ratio (I/S) detector detects the relative phase difference and the relative amplitude difference between the respective output terminals of the I demodulator and the Q demodulator and applies an amplitude control signal and a phase control signal to corresponding amplitude control and phase control inputs of the quadrature LO generator. The I/S detector calibrates the quadrature LO generator during the interstitial interval between the reception of data packets. The control signals from the I/S detector adjust the relative amplitude and phase of the LO_I and LO_Q signals in a manner that reduces the image response of the communications receiver.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.