Patent Application
20120281737
This invention generally relates to communication. More particularly, this invention relates to wireless communication.
Wireless communications have proven useful and are increasing in popularity. Consumers desire increasing wireless communication capabilities. A challenge to service providers is how to provide enhanced services within a limited radio frequency spectrum. One approach for offering high voice and data traffic flow within a single transmission path is to use multiple carriers power amplifier (MCPA) arrangements and multiple transmission paths.
There are various challenges associated with using MCPA arrangements. There are stringent governmental or regulatory out-of-band emission requirements. Additionally, there are in-band considerations. Ideally an ultra-linear characteristic is required to satisfy both types of requirements. In reality, however, high power semi-conductors used for MCPA communications have non-linear performance characteristics. Pre-distortion may be used to address such characteristics.
Pre-distortion techniques typically require a high signal-to-interference ratio and extended bandwidth to allow for correcting high order harmonic distortions. The typical approach is to introduce additional components or circuitry such as a frame level radio frequency isolator to ensure that external interferences like antenna reflection are below a desired threshold. Adding additional devices or circuitry introduces additional loss, uncorrected intermodulation and thermal disadvantages. Accordingly, known approaches are not ideal.
An exemplary wireless communication device includes a plurality of amplifiers that each provide an output signal. A combiner combines the output signals into a combined signal. A pre-distortion processor is configured to provide signal correction for each of the amplifiers. The pre-distortion processor receives feedback comprising an indication of each of the output signals before the output signals are combined into the combined signal.
An exemplary wireless communication method includes providing a plurality of output signals. Each output signal is from one of a corresponding plurality of amplifiers. The output signals are combined into a combined signal. An indication of each output signal is obtained before they are combined into the combined signal. Pre-distortion correction is provided for each of the amplifiers based on the obtained indications as feedback.
The various features and advantages of the disclosed examples will become apparent from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows.
An RF coupling is associated with each of the amplifiers for obtaining an indication of each of the output signals. An RF coupling 44 is associated with the amplifier 22 for obtaining an indication of the output signal 32. An RF coupling 46 obtains an indication of the output signal 34. An RF coupling 48 obtains an indication of the output signal 36. In the illustrated example, each of the indications of the output signals are obtained before those output signals are combined into the combined signal 42. Utilizing the couplings 44, 46 and 48 offers wider bandwidth for effective distortion correction without any limitation caused by the bandwidth limitations of the combiner 40.
The obtained indications of the output signals are provided as feedback 50 to a digital pre-distortion processor 52. The indications of the output signals provide the feedback 50 that allows the pre-distortion processor to provide signal correction for each of the amplifiers 22, 24 and 26 to address non-linearities, for example, of the amplifiers. The pre-distortion correction allows for a resulting combined signal 42 to have desired characteristics or at least to more closely resemble a combined signal having the desired characteristics. There are known digital pre-distortion techniques. One example embodiment uses such known techniques. The manner in which the feedback 50 is achieved in the example of
A summer 54 in this example sums the individual feedback signal indications of each output signal and provides a single feedback signal 50 to the pre-distortion processor 52. The sum of the individual feedback signal indications is different than the combined signal 42 because the individual feedback signal indications do not include the losses associated with the combiner 40 and any other components downstream of the amplifiers.
The illustrated example avoids a requirement for introducing additional isolator components downstream of the amplifiers. Such additional isolators tend to introduce additional radio frequency loss, for example. The illustrated example does not have any requirement for providing an additional frame level RF isolator to protect against external interferences. If the combined signal 42 were used for obtaining feedback for the pre-distortion processor 52, such an isolator would be required.
The illustrated example is well suited for MCPA arrangements. In some examples, the output signals 32, 34 and 36 are wirelessly transmitted by the amplifiers and received by the combiner 40. In other words, the example of
In the example of
The example of
Those skilled in the art who have the benefit of this description will be able to select appropriate hardware, software, firmware or a combination of these to realize the various components and functionalities of the illustrated examples.
The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this invention. The scope of legal protection given to this invention can only be determined by studying the following claims.
