Communication semiconductor integrated circuit, a wireless communication apparatus, and a loop gain calibration method

Abstract

A polar-loop wireless communication apparatus includes, on a forward path between an amplitude detector and a power amplifier which constitute an amplitude control loop, a variable gain amplifier and a switch to change characteristics of a loop filter to output a frequency bandwidth of the amplitude control loop to an order less than an order for normal operation. The system is operated with the characteristics set to the lower order to measure outputs from the power amplifier to calibrate the output power of the power transmitter, and the register is operated with the characteristics set to the higher order to measure the open loop gain of the amplitude control. According to results of the calculation, data to correct gain characteristics of the variable gain amplifier with respect to an output control signal is stored in a nonvolatile memory of a baseband circuit.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] The present application relates to subject matters described in the U.S. patent applications being file based on the United Kingdom Patent Applications No. 0212737.1 filed on May 31, 2002, No. 0212729.8 filed on May 31, 2002, No. 0212723.1 filed on May 31, 2002, No. 0212735.5 filed on May 31, 2002, and No. 0212732.2 filed on May 31, 2002. All of those U.S. applications are assigned to the same assignees of the present application. BACKGROUND OF THE INVENTION [0002] The present invention relates to a technique for improving controllability of output power using a power control signal in a high-frequency power amplifier circuit and for calibrating variation or dispersion in a characteristic thereof due to deviation of a gain of an amplifier control loop, and in particular, to a technique effectively applicable to a communication semiconductor integrated circuit including a phase detecting or detector circuit and an amplifier detecting circ...

AI Technical Summary

Benefits of technology

This approach enhances modulating precision, reduces spectral re-growth, and effectively suppresses noise, while maintaining loop stability by adjusting the loop filter characteristic and correcting the gain variations caused by component dispersion.

Problems solved by technology

As a result, there has been detected a problem that when the 8-PSK modulation is carried out in the polar loop method, it is difficult to satisfy requirements of specifications of, for example, precision of modulation for a transmission waveform (error vector magnitude (EVM)) and a degree of noise suppression.

Specifically, there is a problem in which while the modulating precision is higher and a characteristic called “spectral re-growth” indicating a degree of waveform distortion becomes better when the frequency bandwidth of the amplitude control loop (a frequency range from a central frequency of the transmission carrier wave to a frequency thereof for which an open loop gain is 0 decibel (dB)) is wider, attenuation of the amplitude control loop becomes smaller for a receiving or reception frequency apart from 20 megaherz (MHz) from the central frequency of the transmission carrier wave and a sufficient degree of noise suppression cannot be obtained when the bandwidth is wide.

In addition, in two feedback loops, the loop gain particularly of the amplifier control loop varies due to dispersion or variation in characteristics of constituent components in production and hence stability of the loop decreases, and hence it is difficult to obtain a desired output level in a specified or predetermined period of time.

It has been also detected that the system of the polar loop has a problem that when an output control operation is conducted for the amplitude modulation in the amplitude control loop, the gain of the amplitude control loop changes to reduce a phase margin and hence stability of the loop is lowered.

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