Injection circuit with external predistortion

Abstract

The disclosed circuit includes DC isolated capacitor, high frequency choking winding, decoupling capacitor and radio frequency power amplifier. Being passed through DC isolated capacitor, the input signal in radio frequency is output to the input end of the radio frequency power amplifier. The circuit also includes an operational amplifier with high input impedance. A DC bias signal is input to the positive input end of the operational amplifier. Being cascaded to the DC isolated capacitor, envelope signal is connected to negative input end of the operational amplifier. Being cascaded to high frequency choking winding, output end of the operational amplifier is connected to input end of the radio frequency power amplifier, output signal of which is the output of the disclosed circuit. The invention isolates envelope signal in low frequency from DC signal, expands applicable area of frequency suitable to linearization method of envelope injection, and lowers cost of system greatly.

Description

technical field [0001] The invention relates to the linearization technology of the high-frequency amplifier in the communication system, in particular to the injection technology of the out-of-band predistortion signal. Background technique [0002] In recent years, with the rapid development of wireless communication around the world, wireless spectrum resources are becoming increasingly scarce. In order to utilize limited spectrum resources more effectively, many wireless communication systems adopt linear modulation with higher spectrum utilization efficiency. Since both phase and amplitude of a linearly modulated signal carry useful information, any nonlinear amplification of such a signal will result in an increase in the bit error rate and interference to adjacent wireless channels. Both of these adverse effects should be avoided when designing a wireless communication system, so linear modulation signals must require high linearity amplification. [0003] The nonli...

AI Technical Summary

Problems solved by technology

However, the frequency range that the usual envelope injection method can be limited to compensation has a great limitation: at the low end of the frequency, since the influence of the DC bias signal of the amplifier tube on the envelope injection circuit must be isolated by a DC blocking capacitor, so Very low envelope injected signals will be blocked by this DC blocking capacitor; at the high end of frequency, a large capacitor (usually nF level) at the input of the amplifier tube to filter DC ripple will severely attenuate high frequencies (up to Several megahertz) envelope injection signal, weakening its compensation effect

but figure 2 The problem with the injection circuit shown is that the high-frequency choke coil 206 between the envelope signal and the DC signal cannot effectively prevent the attenuation of the high-frequency components of the envelope signal by the decoupling capacitor 208, and the broadband signal combiner Expensive and inconvenient to use

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