KR20010111551A - Idm detect circuit of 2nd loop for hpa - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit for detecting and canceling intermodulation distortion signals generated by the nonlinear characteristics of high power amplifiers used in mobile communication base station systems. In particular, the circuit configuration is simple and does not use pilot signals. The present invention relates to a second loop intermodulation distortion signal detecting circuit for easily removing intermodulation distortion signals, and comprising a feedword linear circuit and a second loop intermodulation distortion signal detecting circuit. In the circuit for removing the intermodulation distortion signal, the second loop intermodulation distortion signal detection circuit receives a carrier output signal and a carrier input signal including the intermodulation distortion signal applied from the feedword linear cycle, and the carrier signal. A carrier removing unit for removing the low frequency signal, and down-converting the high frequency signal applied from the carrier removing unit A digital signal processing and a F down converter for outputting an analog signal of frequency, an analog / digital converter for converting and outputting an analog signal applied from the down converter to a digital signal, and a digital signal input from the analog / digital converter. It is characterized by a control part which performs the FFT processing, recognizes the frequency, and outputs a control signal for controlling the attenuator and phase controller of the feedword linear circuit.

Description

Secondary loop intermodulation distortion signal detection circuit of high power amplifier {IDM DETECT CIRCUIT OF 2ND LOOP FOR HPA}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit for detecting and removing intermodulation distortion (IMD) signals generated by non-linearity characteristics of high power amplifiers (HPAs) used in mobile communication base station systems. This simple, no pilot signal, and digital control, relates to a secondary loop intermodulation distortion signal detection circuit that easily removes the intermodulation distortion signal.

In the base station system of mobile communication, a high power amplifier (HPA) is used to amplify a high frequency signal to a high level and then output it through an antenna, and such a high power amplifier requires a linear amplification characteristic. However, in general, intermodulation distortion (IMD) occurs due to nonlinear amplification characteristics, and an error signal due to the intermodulation distortion is detected and removed by the first and second loop detection circuits. The circuit to use is used.

Hereinafter, an intermodulation distortion signal detection circuit of a high power amplifier according to the prior art will be described with reference to the accompanying drawings.

Attached to explain the prior art, FIG. 1 is a feedword linearization circuit diagram of a general high power amplifier, and FIG. 2 is a second loop intermodulation distortion signal detection circuit diagram according to the prior art.

Referring to the accompanying drawings, a general feed-forward linearization circuit of a high power amplifier (HPA) is a radio frequency (RF) signal for applying a mobile communication signal to an antenna, and a carrier input signal. A seventh directional coupler (DC) 10 for coupling a pilot IMD signal applied from a secondary loop detector 225 to be described later;

A first directional coupler 20 for dividing the signal output from the seventh directional coupler 10 into a predetermined level and outputting the signal in two paths;

A first attenuator 30 that attenuates the signal output from the first directional coupler 20 to an appropriate level by a control signal,

A first phase controller 40 for adjusting a phase of the signal output from the first attenuator 30 by a control signal;

A high power amplifier (HPA) 50 for amplifying and outputting the signal output from the first phase controller 40 to a high power;

A second directional coupler 60 for dividing a signal output from the high power amplifier 50 into a predetermined level and outputting the signal to another path;

A first delay line 70 for delaying a signal output from the second directional coupler 60 to a predetermined time;

A fifth directional coupler 80 for coupling a signal applied to a signal output from the first delay line 70;

A sixth directional coupler 90 for outputting a signal output from the fifth directional coupler 80 as an amplified carrier signal and simultaneously dividing the signal into a predetermined level and outputting each signal in a different path;

A second delay line 100 which is divided from the first directional coupler 20 and delays and outputs a signal applied at a predetermined level for a predetermined time;

A third directional coupler 110 for coupling the divided signal output from the second directional coupler 60 to the signal output from the second delay line 100;

A fourth directional coupler 120 which extracts a part of the signal output from the third directional coupler 110 and applies it to the controller 160 to be described later;

A second attenuator 130 which attenuates the signal output from the fourth directional coupler 120 to an appropriate level according to a control signal;

A second phase controller 140 for adjusting a phase of a signal output from the second attenuator 130 by a control signal;

An error amplifier 150 for amplifying the signal output from the second phase controller 140 to an appropriate level and outputting the signal to the fifth directional coupler 80;

The controller 160 analyzes the signal applied from the fourth directional coupler 120 and outputs signals for controlling the first and second attenuators 30 and 130 and the first and second phase controllers 40 and 140, respectively. Wow,

Downconverts the signal applied from the sixth directional coupler 90 and generates a pilot IMD signal using a synthesizer and an intermediate frequency generator, and outputs the pilot IMD signal to the seventh directional coupler 10. The loop detector 225 is configured.

In the above configuration, the second delay line 100, the third directional coupler 110, the fourth directional coupler 120, the second attenuator 130, the second phase controller 140 and the error amplifier 150 It is included to configure the primary loop detector 165.

The feedword linearization circuit having the above-described configuration applies the input carrier signal to the primary loop detector 165 and the first attenuator 30 by the first directional coupler 20.

The first attenuator 30 attenuates the carrier signal to an appropriate level by the control of the controller 160, and the signal is applied to the first phase controller 40, thereby controlling the phase by the control of the controller 160. After this adjustment, it is amplified to high power in the HPA 50.

The HPA 50 generates an intermodulation distortion (IMD) signal in the process of being amplified by the nonlinear amplification characteristic, extracts a partial level by the second directional coupler 60, and the primary loop detector ( 155 is applied to the fifth directional coupler 80 after being properly delayed by the first delay line 70.

The primary loop detector 155 delays the signal applied from the first directional coupler 20 by the second delay line 100 and then removes the carrier frequency by the third directional coupler 110. Only an intermodulation distortion (IMD) signal, which is a noise signal, is detected.

The IMD signal is applied to the controller 160 by the fourth directional coupler 120 and analyzed to appropriately control the first and second attenuators 30 and 130 and the first and second phase controllers 40 and 140.

The primary loop detector 155 amplifies the IMD signal whose level and phase are controlled to an appropriate level by the error amplifier 150, and then applies the carrier signal to the fifth directional coupler so that the carrier signal is transmitted by the HPA 50. This eliminates the IMD signal generated by nonlinear amplification.

However, since the IMD signal is not completely removed from the carrier signal output from the fifth directional coupler 80 as described above, a part of the carrier output signal is extracted from the sixth directional coupler 90 and the second loop detector ( And a pilot signal generated by the secondary loop detector 225 and applied to the seventh directional coupler 10 so as to be input to the primary loop detector 155. By applying the signal to the fifth directional coupler 80, the intermodulation distortion signal IMD is removed and again applied to the secondary loop detector 225 to detect the magnitude of the remaining pilot signal, thereby Expect size.

As described above in detail with reference to FIG. 2, the secondary loop detector for generating the pilot signal or the secondary loop intermodulation distortion signal detector 225 may include the first mixer 172 and the bandpass filter 174. Down converter 170 consisting of;

An analog / digital (A / D) converter 180 for converting an analog signal output from the down converter 170 into a digital signal;

A secondary loop controller 165 that receives the signal from the A / D converter 180 and processes the signal to output a control signal controlled by each functional unit of the secondary loop detector 225,

Synthesizer outputting a highly stable signal capable of generating a pilot IMD signal by controlling a phase locked loop (PLL) under the control of the secondary loop control unit 165,

Under the control of the secondary loop control unit 165, the intermediate frequency generator 200 for generating an intermediate frequency (IF),

A divider 210 for distributing the signal output from the synthesizer 190 to two outputs;

A third delay line 230 receiving the signal output from the distributor 210 and delaying the signal for a predetermined time and outputting the delayed signal to the first mixer 172;

By mixing the frequency signal output from the divider 210 to be up-converted into the signal output from the intermediate frequency generator 200, the up-converter 220 outputting a pilot signal. It is composed.

The second loop intermodulation distortion signal detection unit 225 according to the prior art having the above-described configuration, the carrier output signal applied from the sixth directional coupler, by the first mixer 172 of the down-converter 170. At the same time, the signal is down-converted by the signal applied through the third delay line 230 and then passed through the band pass filter 174 to thereby remove the noise signal.

The A / D converter 180, which has received the above signal, converts the digital signal into the digital signal according to the control signal of the secondary loop controller 165, and applies the secondary signal to the secondary loop controller 165. The controller 165 is the same as the controller 160 described above.

The secondary loop controller 165 or the controller 160 analyzes the applied digital signal, thereby determining the size of the pilot signal indicative of the degree of intermodulation distortion (IMD) signal generated from the HPA 50. By controlling the second attenuator 130 and the second phase controller 140, and controlling the PLL function of the synthesizer 190, a frequency as a reference for down modulation and a pilot signal is generated.

In addition, the intermediate frequency generator 200 is controlled so that the signal applied from the synthesizer 190 is up-modulated to the same frequency as the intermodulation distortion (IMD) signal generated from the HPA 50. )

The up-converter 220 up-modulates the signal output from the synthesizer 190 by the signal output from the intermediate frequency generator 200 to generate a pilot signal and apply it to the seventh directional coupler 10. The intermodulation distortion (IMD) signal, from which the carrier signal is removed, is extracted by the first loop detector 155 and applied to the fifth directional coupler 80 to remove the intermodulation distortion (IMD) signal. The carrier signal is output.

However, in the second loop intermodulation distortion signal detection circuit according to the prior art having the above-described configuration, the structure of the synthesizer 190 for generating a reference signal of the pilot IMD signal includes a PLL, a loop filter, a VCO, and a directionality. It is composed of a coupler, etc., there is a problem that is very complicated and expensive, and also only the intermediate frequency generator 200, the up-converter 220, a divider, etc. can generate a pilot signal. However, there is a problem that the volume of the seventh directional coupler 10 is required and the like becomes large.

It is an object of the present invention to provide a secondary loop intermodulation distortion signal detection circuit that requires no pilot signal, is very simple in configuration, inexpensive, and requires a small area.

The present invention devised to achieve the above object comprises a feedword linearization circuit and a second loop intermodulation distortion signal detection circuit, and a circuit for removing intermodulation distortion signals by a high output amplifier of a mobile communication base station. The second loop intermodulation distortion signal detecting circuit may include: a carrier removing unit configured to receive a carrier output signal and a carrier input signal including the intermodulation distortion signal applied from a feedword linear circuit, and to remove the carrier signal; A downconversion unit for downconverting the high frequency signal applied from the carrier removing unit to output an analog signal having a low frequency, an analog / digital converter for converting the analog signal applied from the downconversion unit to a digital signal and outputting the digital signal; Digital signal input and analog signal input from analog / digital converter Recognizing at the frequency and at the same time, characterized by a control unit for outputting a control signal for controlling the attenuator and the phase controller of the feed goodness.Whoa word linear circuit.

1 is a feedword linearization circuit diagram of a typical high power amplifier,

2 is a second loop intermodulation distortion signal detection circuit diagram according to the prior art;

3 is a feedword linearization circuit diagram according to the present invention;

4 is a second loop intermodulation distortion signal detection circuit diagram of a high output amplifier according to the present invention.

** Explanation of symbols on the main parts of the drawing **

10,20,60,80,90,110,120: Directional Coupler

30,130: Attenuator 40,140: Phase controller

50; High Power Amplifiers 70,100,230,310: Delay Lines

150: error amplifier 155: primary loop detector

160,165,600 control unit 170,400 downconverter

172,410 Mixer 174,420 Bandpass filter

180,500 A / D Converter 190 Synthesizer

200: intermediate frequency generator 210: divider

225,700: secondary loop detection unit 300: carrier removal unit

320: power combiner 330; Band-pass filter

Hereinafter, a second loop intermodulation distortion signal detection circuit of a high output amplifier according to the present invention will be described with reference to the accompanying drawings.

3 is a feedword linearization circuit diagram according to the present invention, and FIG. 4 is a second loop intermodulation distortion signal detection circuit diagram of a high output amplifier according to the present invention.

Referring to FIG. 4, the second loop intermodulation distortion signal detecting circuit 700 of the high power amplifier according to the present invention is a signal before the high power amplification as a carrier frequency signal to be applied to the antenna of the mobile communication base station system. A carrier delay line 310 which receives the input signal and outputs the delayed signal for a predetermined time;

The phase difference between the phase of the carrier signal delayed by the carrier delay line 310 and the output signal of the carrier signal combined with the power of the signal applied from the carrier delay line 310 and the output of the carrier signal is amplified and output high output A power combiner 320 which removes the carrier signal and outputs only the intermodulation distortion signal generated by the nonlinear characteristic of the high output amplifier while the carrier signal is amplified by the high output amplifier;

Carrier removal unit consisting of a band rejection filter (BRF: 330) that receives the intermodulation distortion signal from which the carrier signal is removed by the power combiner 320, and blocks only the signal of the carrier frequency once again ( 300),

A downmixer 410 for down converting a high frequency intermodulation distortion signal applied from the band cut filter 330 of the carrier remover 300 by an intermediate frequency (IF);

A down converter 400 comprising a band pass filter 420 for removing a noise signal by passing only a signal of a frequency band down-converted by the down mixer 410;

An analog to digital converter (A / D) 500 for converting an analog signal output from the band pass filter 420 of the downconverter 400 into a digital signal and outputting the digital signal;

Receives a digital signal in a time domain, which is output from the analog-to-digital converter 500, receives a digital signal process (DSP) and a fast fourier transform (FFT) to process a frequency domain. By converting the signal into a frequency signal, the specific frequency required for control and the power of the corresponding frequency are also detected, and the first attenuator 30 and the second attenuator 130 of the feed-forward linearization circuit shown in FIG. The controller 600 is configured to output a signal for controlling the first phase controller 40 and the second phase controller 140.

Hereinafter, the secondary loop intermodulation distortion signal detection circuit 700 of the high output amplifier according to the present invention having the above-described configuration will be described in detail with reference to FIGS. 3 and 4.

A high frequency (RF) signal or a carrier signal, which can be output through an antenna of the mobile communication base station system, is input to the first directional coupler 20, and a constant level of power is distributed to the primary loop detector 155. ), And the carrier signal of the remaining power is input to the first attenuator 30.

The first attenuator 30 attenuates the carrier signal into a power signal having an appropriate level by a control signal applied from the second loop intermodulation distortion (IMD) signal detector or the control unit 600 of the second loop detector 700. After (Attenuation), it is applied to the first phase controller 40.

The first phase controller 40, which receives the control signal of the controller 600, adjusts the phase of the input carrier signal and outputs the same to the high output amplifier 50.

The HPA 50 generates an intermodulation distortion signal (IMD) by a non-linear amplification portion of the HPA 50 in the process of amplifying the received carrier signal with high power. As a result, the HPA 50 outputs the carrier signal amplified to a high output and the IMD signal together.

The signal output from the HPA 50 is extracted part of the power from the second directional coupler 60 is applied to the third directional coupler 110, the signal of the remaining power is output to the first delay line 70. .

The carrier signal and the IMD signal applied to the third directional coupler 110 are applied to the second delay line 100 of the primary loop detector 155 by the first directional coupler 20 and for a predetermined time. Combined with the delayed signal.

The combined signal as described above, that is, the carrier signal applied from the second directional coupler 60 and the carrier signal applied by the second delay line 100 are accurately canceled and removed from each other because the phases are reversed, The reason for the complete removal as described above is that the control unit 600 finely adjusts the phase by the first phase controller 40 so that the phase is reversed, and the level is the same by the first attenuator 30. This is because the control unit 600 controls.

Accordingly, the third directional coupler 110 outputs only an intermodulation distortion (IMD) signal, and the IMD signal as described above, under the precise control of the control unit 600, the second attenuator 130 and the second phase. By passing through the controller 140, it is attenuated to an appropriate level and the phase is accurately adjusted.

The IMD signal as described above is applied to the error amplifier 150, amplified to an appropriate level, and applied to the fifth directional coupler 80.

The fifth directional coupler 80 receives a carrier signal and an IMD signal applied from the second directional coupler 60 through a first delay line 70 and is input in a state where the period or synchronization is consistent, and the primary By combining with the IMD signal applied from the error amplifier 150 of the loop detector 155, the IMD signals having opposite phases cancel each other out.

In more detail, the IMD signal applied from the primary loop detection unit 155 is controlled by the second phase controller 140, which is precisely controlled by the controller 600, from the IMD signal generated by the HPA 50. After the phase is adjusted to the reverse, it is applied to the fifth directional coupler 80.

Therefore, the signal output from the fifth directional coupler 80 is output with the intermodulation distortion (IMD) signal removed, and the carrier signal from which the IMD is removed is transmitted by the sixth directional coupler 90. Since the signal is detected as a carrier signal of a predetermined level and applied to the secondary loop detector 700 again, it is used to detect and remove an IMD signal of a carrier signal input in the following order.

The second loop intermodulation distortion signal detector 700 receives a signal without high output amplification, that is, a carrier signal without IMD at all, from the delay line 310 of the carrier remover 300. After a delay for a predetermined time, it is input to the power combiner 320.

The power combiner 320 simultaneously receives a carrier signal from which the IMD has been removed from the sixth directional coupler 90.

Since the carrier signal from which the IMD applied from the sixth directional coupler 90 has been removed has already been phase adjusted by the first phase controller 40, the carrier signal is out of phase with the high power amplified carrier signal, By being combined at the combiner 320, only IMD signals that are canceled and removed from each other and remain fine are output.

The IMD signal as described above is applied to the bandpass filter (BRF) 330 to block any carrier signals that may remain, thereby detecting only pure and weak intermodulation distortion (IMD) signals.

The intermodulation distortion signal detected by the carrier removing unit 300 is input to the mixer 410 of the downconverter 400 and mixed with the intermediate frequency IF, thereby down-converting the bandpass filter. The noise signal, which is likely to be generated by the mixer 410, other than the IMD signal downconverted by 420 is removed.

The analog IMD signal output from the down converter 400 is converted into a digital signal in a time domain by the A / D converter 500 and output to the control unit 60.

The control unit 600 converts the input time domain digital signal into a signal in a frequency domain by processing Digital Signal Process (DSP) and FFT, thereby analyzing the received time domain digital signal as an IMD signal having power information in units of frequency do.

The controller 600 analyzes and processes the frequency domain IMD signal in units of required frequencies to output control signals for precisely controlling the first and second attenuators 30 and 130 and the first and second phase controllers 40 and 140, respectively. Therefore, the secondary loop detection unit 700 makes the power level of the IMD signal detected again to be the minimum.

Therefore, the present invention of the above configuration. Without using a pilot IMD signal and using a complex, bulky, and expensive synthesizer 190, a simple, compact, low-cost, secondary loop intermodulation distortion signal detection circuit Can be produced.

In addition, when the pilot signal is used, there is a noise effect due to the pilot signal, but it is not necessary to consider the noise as described above, and the IMD signal is detected at the minimum level by precise control of the controller 600. Therefore, the distortion caused by the down-converted IMD signal can be significantly reduced.

In addition, by converting the time-domain IMD signal sampled by the A / D converter 180 into a frequency-domain signal by FFT processing, for example, the power of the frequency portion required by the spectrum analyzer is detected. As it is possible, it is suitable for digital processing.

As described above, the present invention has the effect that a secondary loop circuit for detecting intermodulation distortion signals of a high output amplifier can be manufactured with a simple circuit configuration, small size, and low cost.

In addition, by processing the signal converted to the digital frequency domain, it is suitable for digital control that can measure the accurate frequency and power of the intermodulation distortion signal, there is an industrial and industrial use effect.

Claims (2)

A circuit comprising a feedword linear circuit and a secondary loop intermodulation distortion signal detection circuit, the circuit for removing intermodulation distortion signals by a high output amplifier of a mobile communication base station, The second loop intermodulation distortion signal detecting circuit may include a carrier removing unit configured to receive a carrier output signal and a carrier input signal including the intermodulation distortion signal received from a feedword linear circuit, and to remove the carrier signal; A downconversion unit for downconverting the high frequency signal applied from the carrier removing unit to output an analog signal having a low frequency; An analog / digital converter for converting an analog signal applied from the down converter into a digital signal and outputting the digital signal; And a control unit for recognizing the digital signal inputted from the analog / digital converter as a frequency by digital signal processing and FFT processing, and outputting a control signal for controlling the attenuator and phase controller of the feedword linear circuit. Secondary loop intermodulation distortion signal detection circuit of the high power amplifier, characterized in that According to claim 1, The carrier removing unit may include a carrier delay line for delaying an input carrier signal; A power combiner for removing the carrier signal by mixing the carrier signal applied from the delay line and the carrier output signal mixed with the intermodulation distortion signal, and outputting the intermodulation distortion signal; Secondary loop intermodulation distortion signal detection circuit of the high output amplifier, characterized in that the band-block filter for blocking the carrier signal again from the signal input from the power combiner,