In current mobile communications networks, or cellular networks, many users typically need to share the spectrum to achieve high-rate multimedia communication. From the perspective of a communication between a single user and a base transceiver station, the other users and their respective communications with the base transceiver station or with other base transceiver stations cause an interference for the wireless communication at hand. In other words, noise and unwanted signal sources may cause an interference. For example, a radio transceiver may receive strong unwanted signals out of the desired signal range. These so called blocker signals should be filtered out from the received signal early in the receiver path of the transceiver. In the uplink case, a base transceiver station typically needs to simultaneously detect many asynchronous users. In the downlink case, the users (i.e., the communications between the base transceiver station and the different mobile stations) will be scheduled and largely orthogonalized, but the mobile station will still need to cope with a few dominant interfering base transceiver stations.
Blocker signals that are still present in the received signal subject to an analog-to-digital conversion may cause intermodulation distortion and aliasing. Continuous-time delta-sigma modulators may be used as the analog-to-digital converter of a receiver. The use of delta-sigma modulators relaxes the anti-alias filtering requirement but even with these modulators strong out-of-band signals may render the modulator unstable or at least create distortion.
USPTO Backgrounds
USPTO Backgrounds