KR20000031841A - Predistortor with automatic phase controller - Google Patents

Abstract

PURPOSE: A predistortor with an automatic phase controller is provided to reduce a characteristic of an IMD(Inter-Modulation Distortion) signal by circulating a loop for controlling a phase control circuit. CONSTITUTION: A predistortor with an automatic phase controller comprises an automatic phase control loop circuit. The automatic phase control loop circuit detects an IMD(Inter-Modulation Distortion) signal, controls a phase control circuit, and reduces the IMD signal to provide a characteristic of linear amplification. The automatic phase control loop circuit comprises an IMD extraction portion and a first IMD level detection portion(111). The IMD extraction portion extracts the IMD signal. The first IMD level detection portion detects a level of the IMD signal.

Description

Predistorter with Automatic Phase Adjuster

The present invention relates to a predistorter using intermodulation distortion. In particular, the present invention relates to a predistorter that is used in front of an amplifier by automatically adjusting a phase so that it is suitable for a front end of a PA (amplifier) for a mobile communication system capable of linearizing the output characteristics of the amplifier. A predistorter is provided with a phase adjuster.

In general, a predistortor is positioned in front of an amplifier to attenuate third-order intermodulation distortion signals (hereinafter referred to as intermodulation distortion signals or IMDs) generated by an amplifier to generate artificial third-order intermodulation distortion signals. do. The third order intermodulation distortion signal (hereinafter referred to as IMD) is collectively referred to as intermodulation distortion signal.

1 shows a conventional predistorter. As shown, a first small linear amplifier (Q1) (1) for linearly amplifying the input signal, a first divider (DIV1) (2) for distributing the signal in phase, and also for distributing the signal in phase Third-order intermodulation of the second divider (DIV2) 3, the first delay line 8 for phase-adjusting one output signal of the second divider 3, and the output signal of the first divider 2; An error amplifier 4 for generating a signal, and a first combiner COM1 for combining the signals of the error amplifier 4 with the output signal of the first delay line 8 in phase; 5), a second delay line 9 for phase-adjusting the output signal of the second divider 3, an output signal of the first synthesizer 5 and an output signal of the second delay line 9; A second combiner (COM2) 6 summing in phase and a final (FINAL) small linear amplifier (Q2) 7 for linearly amplifying the output signal of the second coupler (6).

Looking at the conventional operation configured as described above are as follows.

As shown in FIG. 1, when the first small linear amplifier Q1 (1) linearly amplifies the signal coming into 2Tone, the third order distortion is not generated and only the signal is greatly amplified so that the first divider DVI1 (2). Is applied. The two signals are split into two in-phase signals, one into a second divider (DIV2) 3 which divides them into two in-phase signals, and another signal is introduced into the error amplifier 4 which deliberately produces a third-order modulated signal. The two-tone signal introduced into the error amplifier 4 generates a third order intermodulation signal by the internal amplifier. This signal is applied to the first combiner (COM1) 5 for synthesizing the signal and the output of the second divider 3 is applied to the first delay line 8 for adjusting the phase. The phase-adjusted signal and the third-order intermodulation signal are applied to the second combiner COM2 6 together with the signals of the first combiner COM1 5 so that the original 2Tone signal is revived. The output characteristics of the second coupler COM2 6 are adjusted by delaying the phase with a delay line 9. This signal is finally amplified linearly by the final amplifier 7 and output.

However, in the related art, the delay line for adjusting the phase has to be adjusted with a microstrip line or a semi-rigid cable. This is because the characteristics of the predistorter are not always the same, and the characteristics of the predistorter are not always changed due to the influence of time or surroundings, and it is difficult to produce the correct characteristics. There was a problem.

Accordingly, the present invention has been made to solve the above-mentioned problems, and the phase adjustment for canceling or synthesizing the original signal in the predistorter is automatically adjusted based on the output thereof, and the preposition based on the output of the intermodulation distortion signal. It is an object of the present invention to provide a predistorter with an automatic phase adjuster which automatically adjusts the phase adjustment in the distortion so that the output of the final amplifier is linearized and amplified to make the final output characteristic more stable.

A predistorter equipped with an automatic phase adjuster according to the present invention for achieving the above object, in the predistorter, detects the intermodulation distortion signal (IMD) from the output signal of the final amplifier via the predistorter and detects the intermodulation And an automatic phase control loop circuit for controlling the phase control circuit in the predistorter based on the distortion signal to reduce the intermodulation distortion signal in the output signal of the amplifier to provide linear amplification characteristics.

1 is a configuration and waveform diagram of a predistorter and a final amplifier having a conventional fixed phase regulator,

2 is a configuration and waveform diagram of the predistorter and the final amplifier with an automatic phase adjuster according to the present invention.

Explanation of symbols on the main parts of the drawings

101: linear amplifier (Q1) 102: first divider

103: second divider 104: error amplifier (Eroor Amp)

105: first synthesizer 106: second synthesizer

107: final amplifier (Q2) 108: first phase regulator

109: second phase adjuster 110: original signal detector

111: first IMD level detector 112: second IMD level detector

113: first divider 114: third phase adjuster

115: third synthesizer

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Figure 2 shows the configuration and waveforms of the predistorter and the final amplifier having an automatic phase adjuster according to an embodiment of the present invention. As shown, a linear amplifier (Q1) 101 for linearly amplifying a signal, a first divider 102 for separating the linear amplified signal in phase, and one output signal of the first divider 102 are identical. A second divider 103 for phase separation, an error amplifier 104 for receiving a third output signal of the first divider 102 to produce a third order intermodulation signal, and one of the second divider 102 A first phase adjuster 108 for phase adjusting the output, a third divider 113 for separating the other output signal of the second divider 102 in phase, and an output signal of the error amplifier 104; A first synthesizer (COM1) 105 for synthesizing the output signal of the first phase adjuster 108 and an original signal from the output signal of the first synthesizer (COM1) 105 to detect the first phase adjuster ( An original signal detection unit 110 for outputting a control signal to the second signal; and a phase adjustment unit for outputting one output signal of the third distributor; A second synthesizer (COM2) 106 for synthesizing a second phase adjuster 109, an output signal of the first synthesizer 105 and an output signal of the second phase adjuster 109, and the second synthesizer COM2. A final linear amplifier Q2 107 for linearly amplifying the output signal of < RTI ID = 0.0 >), < / RTI > a third phase adjuster 114 for phase-adjusting the other output signal of the third divider, and the final linear amplifier Q2 107. And a third synthesizer 115 for synthesizing the output signal of the third phase adjuster 114 and the level of the intermodulation signal from the third synthesizer output signal. A second IMD level detector for comparing the level of the intermodulation signal from the output signal of the third synthesizer 115 and the first IMD level detector 111 to output the control signal to the third phase adjuster 114 as a control signal; It consists of 112.

That is, the intermodulation distortion signal IMD is detected from the output signal of the final amplifier 7 via the predistorter to the conventional predistorter shown in FIG. 1 and based on the detected intermodulation distortion signal in the predistorter. It further comprises an automatic phase adjustment loop circuit 110-115 that controls the phase adjustment circuit 8 to reduce the intermodulation distortion signal in the output signal of the amplifier 7 to provide a linear amplification characteristic.

In the automatic phase control loop circuits 110-115, the third phase adjuster 114 and the third synthesizer 115 serve as intermodulation distortion signal (IMD) extracting means, and the original signal before predistortion to the output signal of the final amplifier. Phase-modulated and synthesized to extract the intermodulation distortion signal IMD, and the first IMD level detector 111 is a level of the intermodulation distortion signal IMD as the intermodulation distortion signal IMD level detecting means. Is detected and output as a phase control signal in the predistorter. The second IMD level detector 12 detects the level of the intermodulation distortion signal IMD extracted through the intermodulation distortion signal IMD extraction means, and thus, the third phase in the intermodulation distortion signal IMD extraction means. The controller 114 outputs the original signal phase adjustment control signal.

In addition, the original signal detection unit 10 is an automatic phase adjustment loop circuit that detects the original signal excluding the intermodulation component from the predistortion signal, and controls the phase adjustment circuit for canceling the original signal based on the detected original signal to predistort the signal. The original signal is canceled among the signals in use to extract only the intermodulation distortion signal.

The first, second, and third phase adjusters 108, 109, and 114 receive a general analog DC voltage and continuously change the phase of the RF signal.

Looking at the operation of the present invention configured as described above are as follows.

First, when the test two-tone signal passes through the linear amplifier Q1 101 which linearly amplifies the signal, the signal becomes larger than the original signal (firstly, a linear amplifier). This signal is applied via a first divider (DIVI) 102 which distributes one signal in two in phase and one to a second divider (DIV2) 103 which also distributes into two in-phase signals and the other signal Is applied to the error amplifier 104 which produces a third order intermodulation signal.

The signal applied to the second divider (DIV2) 103 is divided into two in-phase and is sent to the third divider (DIV3) 113, which divides the first phase regulator 108 and two in-phase signals, respectively. . The signal passing through the first phase adjuster 108 is applied to the first combiner COM1 105 together with the output of the error amplifier 104, where the output is canceled by the original two-tone signals being out of phase with each other. At this time, the signal passed through the first phase shifter (108) 108 is applied to the first combiner (COM1) 105 together with the output of the error amplifier 104, and the output is the original 2Tone signal The phases are reversed and canceled with each other. At this time, the phase is directly controlled by the first phase shifter (Phase shifter 1) 108 so that the output signal of the first synthesizer (COM1) 105 as shown in the two-tone signal is reversed phase and cancel each other. At this time, the phase is directly controlled by the first phase shifter (Phase shifter1) 108, so that the output waveform of the first synthesizer (COM1) 105 is responsible for the phase adjustment inverse to cancel the 2Tone signal.

The signal applied to the third divider (DIV3) 113 is divided into two so that one of the outputs is passed through the second phase shifter (Phase shifter2) 109 and the third horn by the second synthesizer (COM2) 106. It is combined with the modulated signal and applied to the final amplifier Q2 107. The third-order intermodulation signal of the signal synthesized by the second synthesizer (COM2) 106 is canceled by the linear amplifier of the next stage so that only the original 2TONE signal is left and amplified.

The role of the first phase shifter 1 108 and the second phase shifter 2 109 before being applied to the first synthesizer COM1 105 and the second synthesizer COM2 106 is such a role. Allows you to automatically adjust the phase to cancel 2Tone signals or synthesize 2 Tone signals.

Conventional fixed phase regulators have a contradiction that this role is fixed, that is, by adjusting the microstrip line or semi-rigid cable while checking the output characteristics, and the final output characteristics change due to some factors such as temperature during operation. The autophase regulator can compensate for this contradiction and make the final output even better.

The output of the first synthesizer (COM1) 105 needs to be fine tuned by the first phase shifter (108) and has a great influence on the final output characteristics. It depends on how faithfully the third-order intermodulation signal produced by the error amplifier 104 and the two-tone signal are canceled. The output characteristics of the second synthesizer (COM2) 106 are also faithful to the second phase shifter (Phase shifter2) 109, which allows the original input signal to pass while maintaining the third order intermodulation signal generated by the error amplifier 104. Depends on How faithful these phase shifters are in the mission depends on the Detect circuit.

First, after detecting the original 2Tone signal at the output of the first synthesizer (COM1) 105, this information is controlled through the original signal detector 110 to control the first phase shifter (Phase shifter1) 108. This operation is repeated repeatedly so that the output of the first synthesizer (COM1) 105 remains pure pure third-order intermodulation signal.

Second, the third order intermodulation signal of the final amplifier Q2 107 is detected and synthesized again by the original 2Tone signal and the third synthesizer (COM3) 115. The synthesized signal remains only a third-order intermodulation signal by a third phase shifter 3 114 and a third phase shifter 3 by IMD Level detect 2 112 and IMD Level Detect 1 111, respectively. The control unit 114 and the second phase shifter 2 109 are controlled. By looping for phase control, the output spectrum of the final amplifier Q2 107 is only amplified and linearized.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and it is common knowledge in the art that various substitutions, conversions, and changes can be made without departing from the technical spirit of the present invention. It will be apparent to those who have

According to the present invention, the loop control for controlling the phase modulation circuit for adjusting the intermodulation distortion signal based on the output value of the intermodulation distortion signal serves as a conventional fixed phase controller. This attenuation makes it possible to stably provide linear amplification characteristics.

In addition, in the conventional case, a lot of processes are required to adjust the phase when testing the characteristics of the amplifier, and in the case of the production line, it is complicated, but the automatic phase adjustment function is provided so that the output characteristics are more stable and Provides excellent effects.

Claims (4)

In the predistorter, The intermodulation distortion signal IMD is detected from the output signal of the final amplifier via the predistorter, and the phase adjustment circuit in the predistorter is controlled based on the detected intermodulation distortion signal to interpolate the intermodulation distortion of the output signal of the amplifier. A predistorter with an automatic phase adjuster, characterized in that it further comprises an automatic phase adjusting loop circuit for reducing the signal to provide linear amplification characteristics. The method of claim 1, wherein the automatic phase control loop circuit, Intermodulation distortion signal (IMD) extraction means for extracting intermodulation distortion signal (IMD) by phase-adjusting and synthesizing the original signal before predistortion with an output signal of the final amplifier; And a first intermodulation distortion signal (IMD) level detecting means for detecting the level of the extracted intermodulation distortion signal (IMD) and outputting it as a phase adjustment control signal in a predistorter. Equipped predistorter. The method of claim 2, wherein the automatic phase control loop circuit, A second intermodulation for detecting the level of the intermodulation distortion signal IMD extracted by the intermodulation distortion signal IMD extraction means and outputting the original signal phase adjustment control signal into the intermodulation distortion signal IMD extraction means; A predistorter with an automatic phase adjuster, characterized in that it further comprises a distortion signal (IMD) level detecting means. The method according to any one of claims 1 to 3, Detects the original signal excluding the intermodulation component from the predistorted signal, and controls the phase control circuit for canceling the original signal based on the detected original signal to cancel only the intermodulated distortion signal by canceling the original signal from the predistorted signal. A predistorter having an automatic phase adjuster, further comprising an automatic phase adjusting loop circuit.