Distortion detection apparatus for controlling predistortion, carrier cancellation and feed-forward cancellation in linear RF power amplifiers
First Claim
1. An RF power amplifier arrangement comprising:
- an RF input port to which an RF input signal is applied;
an RF output port from which an amplified RF output signal is derived;
a main RF signal path containing an RF power amplifier between said RF input and output ports;
a carrier cancellation combiner coupled to said RF input port and an output path from said RF power amplifier;
a feedforward error correction and reinjection path containing an auxiliary RF error amplifier coupled between said carrier cancellation combiner and said output path from said RF power amplifier;
a frequency swept input receiver coupled to monitor energy contained in said RF input signal;
a frequency swept output receiver selectively coupled to monitor energy in one of said output path from said RF power amplifier and an output of said carrier cancellation combiner; and
a control unit which is operative to selectively couple said frequency swept output receiver to one of said output path from said RF power amplifier and said output of said carrier cancellation combiner, so as to monitor energy received by said frequency swept output receiver, and control characteristics at least one of said main RF signal and feedforward error correction and reinjection paths.
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Accused Products
Abstract
RF power amplifier distortion can be accurately measured in the presence of multi-carrier input signals, by using a common swept local oscillator to tune RF input and output receivers, whose outputs are monitored for distortion correction purposes. In carrier cancellation and feedforward cancellation mode, when the power detected by the input receiver exceeds a power threshold, the processor accumulates a digital representation of uncancelled carrier energy detected by the output receiver when sampling the signal at the output of the carrier cancellation combiner. It otherwise accumulates uncancelled IMD sampled at the output of the amplifier downstream of the feedforward cancellation coupler. In predistortion mode, the output receiver monitors only the output of the carrier cancellation combiner. When the power detected by the input receiver does not exceed the carrier power threshold, any energy measured by the output receiver corresponds to residual distortion energy from the predistorted main amplifier. This allows predistortion to be adaptively controlled by minimizing accumulated energy detected by the output receiver when it monitors the output of the carrier cancellation combiner during the entire sweep.
151 Citations
20 Claims
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1. An RF power amplifier arrangement comprising:
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an RF input port to which an RF input signal is applied;
an RF output port from which an amplified RF output signal is derived;
a main RF signal path containing an RF power amplifier between said RF input and output ports;
a carrier cancellation combiner coupled to said RF input port and an output path from said RF power amplifier;
a feedforward error correction and reinjection path containing an auxiliary RF error amplifier coupled between said carrier cancellation combiner and said output path from said RF power amplifier;
a frequency swept input receiver coupled to monitor energy contained in said RF input signal;
a frequency swept output receiver selectively coupled to monitor energy in one of said output path from said RF power amplifier and an output of said carrier cancellation combiner; and
a control unit which is operative to selectively couple said frequency swept output receiver to one of said output path from said RF power amplifier and said output of said carrier cancellation combiner, so as to monitor energy received by said frequency swept output receiver, and control characteristics at least one of said main RF signal and feedforward error correction and reinjection paths. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of measuring and compensating for distortion in an RF power amplifier coupled over a main RF signal path to an RF input port, to which an RF input signal is coupled, and having an output path coupled to an RF output port, from which an amplified RF output signal is derived, said method comprising the steps of:
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(a) coupling a carrier cancellation combiner to said RF input port and said output path from said RF power amplifier;
(b) coupling a feedforward error correction and reinjection path containing an auxiliary RF error amplifier between said carrier cancellation combiner and said output path from said RF power amplifier;
(c) coupling a frequency swept input receiver to said RF input port;
(d) selectively coupling a frequency swept output receiver to one of said output path from said RF power amplifier and an output of said carrier cancellation combiner; and
(e) controlling characteristics at least one of said main RF signal and feedforward error correction and reinjection paths in accordance with energy received by said frequency swept output receiver. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification