Envelope tracking can be employed to reduce power consumption of a power amplifier, but envelope tracking can introduce nonlinearities to a power amplifier. These nonlinearities can manifest themselves as noise at the output of the power amplifier. Embodiments described herein provide techniques for characterizing a parameter indicative of power amplifier noise when envelope tracking is employed. Measurement of this parameter can permit power amplifier designers to decide whether to forgo envelope tracking if a power amplifier is too susceptible to such noise, redesign the power amplifier to improve compatibility with envelope tracking, or to employ distortion compensation circuitry to reduce the noise output by the power amplifier. Counterintuitively, this distortion compensation circuitry may involve increasing the power, such as the envelope tracking power supply. However, increasing the power may be a desirable trade-off for increased linearity.

An error-feedback transmitter includes an input that receives an input signal, and an output that produces an output signal. It also includes an amplifier, located on a main path that carries a main signal between the input and the output. The transmitter includes a feedback path that carries a feedback signal from the output to the input, and a feedback-signal combiner, located on the main path between the input and the amplifier. The feedback-signal combiner negatively combines the feedback signal with the input signal to improve linearity in the output signal. The transmitter includes a feedforward path that carries a feedforward signal from the input toward the output, and a feedforward-signal combiner, located on the feedback path between the output and the feedback-signal combiner. The feedforward-signal combiner negatively combines the feedforward signal with the feedback signal to suppress components of the main signal in the feedback signal.

A receiver (e.g., for a 10G fiber communications link) includes an interleaved ADC coupled to a multi-channel equalizer that can provide different equalization for different ADC channels within the interleaved ADC. That is, the multi-channel equalizer can compensate for channel-dependent impairments. In one approach, the multi-channel equalizer is a feedforward equalizer (FFE) coupled to a Viterbi decorder, for example, a sliding block Viterbi decoder (SBVD); and the FFE and/or the channel estimator for the Viterbi decoder are adapted using the LMS algorithm.

An error-feedback transmitter includes an input that receives an input signal, and an output that produces an output signal. It also includes an amplifier, located on a main path that carries a main signal between the input and the output. The transmitter includes a feedback path that carries a feedback signal from the output to the input, and a feedback-signal combiner, located on the main path between the input and the amplifier. The feedback-signal combiner negatively combines the feedback signal with the input signal to improve linearity in the output signal. The transmitter includes a feedforward path that carries a feedforward signal from the input toward the output, and a feedforward-signal combiner, located on the feedback path between the output and the feedback-signal combiner. The feedforward-signal combiner negatively combines the feedforward signal with the feedback signal to suppress components of the main signal in the feedback signal.

RF coupling circuitry includes a first coupled signal output node, a second coupled signal output node, an RF coupler, RF filtering circuitry, and attenuator circuitry. The RF coupler is configured to couple RF signals from an RF transmission line to provide coupled RF signals. The RF filtering circuitry is coupled to the RF coupler and configured to separate RF signals within a first RF frequency band in the coupled RF signals from RF signals within a second RF frequency band in the coupled RF signals. The attenuator circuitry is coupled between the RF filtering circuitry, the first coupled signal output node, and the second coupled signal output node. The attenuator circuitry is configured to attenuate the RF signals within the first RF frequency band and the RF signals within the second RF frequency band.

Envelope tracking can be employed to reduce power consumption of a power amplifier, but envelope tracking can introduce nonlinearities to a power amplifier. These nonlinearities can manifest themselves as noise at the output of the power amplifier. Embodiments described herein provide techniques for characterizing a parameter indicative of power amplifier noise when envelope tracking is employed. Measurement of this parameter can permit power amplifier designers to decide whether to forgo envelope tracking if a power amplifier is too susceptible to such noise, redesign the power amplifier to improve compatibility with envelope tracking, or to employ distortion compensation circuitry to reduce the noise output by the power amplifier. Counterintuitively, this distortion compensation circuitry may involve increasing the power, such as the envelope tracking power supply. However, increasing the power may be a desirable trade-off for increased linearity.

A receiver (e.g., for a 10 G fiber communications link) includes an interleaved ADC coupled to a multi-channel equalizer that can provide different equalization for different ADC channels within the interleaved ADC. That is, the multi-channel equalizer can compensate for channel-dependent impairments. In one approach, the multi-channel equalizer is a feedforward equalizer (FFE) coupled to a Viterbi decorder, for example, a sliding block Viterbi decoder (SBVD); and the FFE and/or the channel estimator for the Viterbi decoder are adapted using the LMS algorithm.

Power amplifier circuits can behave in a non-linear manner particularly when operated to produce output signal swings approaching an amplifier saturation region. A pre-distortion signal can be applied to a signal to be transmitted to compensate for such power amplifier non-linearity. In applications where two or more transmitter power amplifiers are used, a beam-former can be configured to modify a digitally pre-distorted transmission signal by applying respective beam-forming weighting factors to the digitally pre-distorted transmission signal to provide input transmission signals for respective ones of the power amplifier circuits. The pre-distortion signal can be established at least in part using one or more of a sensed or estimated representation of a transmitted beam formed by spatially aggregating transmitted outputs from the two or more power amplifier circuits. In this manner, power amplifier efficiency can be enhanced without entirely separate pre-distortion compensation for each of the power amplifier circuits.

A radio frequency transmitter for wireless communication includes a plurality of input ports to receive a plurality of sequences of baseband symbols to be transmitted on a plurality of disjoint frequency bands, a power encoder to modulate and encode the plurality of sequences of baseband symbols to produce an encoded multi-band signal including the plurality of disjoint frequency bands carrying the plurality of sequences of baseband symbols, a first power amplifier for amplifying the encoded multi-band signal to produce an amplified encoded multi-band signal, a first noise canceller to generate a first noise mitigation signal from the encoded multi-band signal and the plurality of sequences of baseband symbols, a first power combiner to combine the amplified encoded multi-band signal and the first noise mitigation signal to produce an RF multi-band signal, and an antenna for transmitting the RF multi-band signal.

A receiver (e.g., for a 10 G fiber communications link) includes an interleaved ADC coupled to a multi-channel equalizer that can provide different equalization for different ADC channels within the interleaved ADC. That is, the multi-channel equalizer can compensate for channel-dependent impairments. In one approach, the multi-channel equalizer is a feedforward equalizer (FFE) coupled to a Viterbi decorder, for example, a sliding block Viterbi decoder (SBVD); and the FFE and/or the channel estimator for the Viterbi decoder are adapted using the LMS algorithm.