KR19980069488A - Linear amplifier and method - Google Patents

Abstract

A linear amplification device having a power amplifier generates harmonics corresponding to an input RF signal, generates a predistortion signal by combining the harmonics and the RF signal, and suppresses intermodulation signals generated when amplifying the RF signal in the power amplifier. The intermodulation signal component is canceled by canceling the input RF signal and the output of the power amplifier, error amplified, and the amplified intermodulation signal is combined with the output of the power amplifier to second suppress the intermodulation signal.

Description

Linear amplifier and method

The present invention relates to a linear amplification apparatus and method, and more particularly, to a linear amplification apparatus and method that can remove intermodulation components using a predistortion method and a feed forward method.

In general, a high power amplifier (HPA) operates near a saturation region having nonlinear characteristics to generate maximum output. However, when multi-carriers are input to the high output amplifiers, these multi-carriers generate inter-modulation distortion (IMD), so that the performance of the amplifiers is greatly degraded. Therefore, a problem arises in that the level of the input signal has to be back-off several dB to operate, or to be changed to a larger power transistor (Power TR).

In this case, a linear power amplifier (LPA) is not a large-capacity transistor, but uses a transistor of an appropriate capacity, and the generated intermodulation component can be removed by linearization. Therefore, the linear amplifier is an essential component in order to improve the quality of the RF signal transmitted from the communication device.

1 illustrates the configuration of a linear power amplifier (LPA) disclosed in US Pat. No. 5,130,663, which was invented in Tattersall et al. The linear amplifier having the configuration as shown in FIG. 1 generates a pilot signal, couples it to an input signal, and detects the pilot signal at the final output terminal to suppress the distortion component by controlling the phase and the gain of the error amplifier. That is, the linear amplifier uses a pilot signal to continuously suppress the phase and gain of the error amplifier regardless of various factors in order to suppress the intermodulation component, and determines the magnitude of the suppressed pilot signal to determine the distortion component. Will be suppressed.

However, as shown in FIG. 1, a linear amplifier using a pilot tone cannot consider various environmental factors, and thus it is difficult to set a condition for automatically adjusting linear amplification. In addition, circuits such as pilot generators and pilot detectors have been added to complicate the configuration and control of the linear amplifier.

As described above, the linearization method capable of removing intermodulation components produces a predistortion component in the input signal to improve the intermodulation suppression characteristics of the main amplifier, and feeds the distortion components back to the amplifier output. There are a negative feedback method for suppressing the included distortion component, and a feedforward method for suppressing the distortion component by creating an inverse phase by extracting only the distortion component.

It is therefore an object of the present invention to provide a linear amplification apparatus and method capable of dispersing and removing intermodulation components by using a predistortion method and a feedforward method.

Another object of the present invention is to provide an apparatus and method for suppressing intermodulation components generated in a main amplifier using a predistortion method and suppressing intermodulation components included in an amplified signal finally output using a feedforward method. Is in.

Another object of the present invention is to install a predistorter in front of the main amplifier of the linear amplifier and predict the intermodulation components to be generated in the main amplifier in advance to generate a predistortion signal to enter the main amplifier to be generated in the main amplifier The present invention provides a linear amplification apparatus and method capable of first suppressing intermodulation components.

Another object of the present invention is to extract the remaining intermodulation component included in the output of the main amplifier of the first suppressed intermodulation component in the linear amplification device and combine the final modulation signal to the final output amplification signal The present invention provides a device and a method capable of secondary suppression.

The linear amplification apparatus of the present invention for achieving the above object, generates a harmonic corresponding to the input RF signal and generates a predistortion signal by combining the harmonic and the RF signal to generate a horn when amplifying the RF signal in the power amplifier Suppressing the modulated signal first, canceling the modulated signal component by canceling the input RF signal and the output of the power amplifier, error amplifying, and combining the amplified intermodulated signal and the output of the power amplifier to combine the modulated signal It characterized in that the secondary suppression.

In the present invention for achieving the above object, in the method of removing the intermodulation signal of the linear amplifier, generating a harmonic corresponding to the input RF signal and combining the harmonic and the RF signal to generate a predistortion signal in the power amplifier Firstly suppresses the intermodulation signal generated during RF signal amplification, cancels the intermodulation signal component by canceling the input RF signal and the output of the power amplifier, and then amplifies the error, and outputs the amplified intermodulation signal and the power amplifier. By combining the second modulated signal to the intermodulation signal.

1 is a diagram showing the configuration of a conventional linear amplifier.

2 is a diagram showing the configuration of a linear amplifier according to a first embodiment of the present invention.

3 is a diagram illustrating a configuration of a predistorter in FIG. 2.

4 is a diagram illustrating a configuration of an automatic level controller in FIG. 3.

FIG. 5 is a diagram illustrating a configuration of a power detector in FIG. 4. FIG.

6A and 6B show characteristics of a signal spectrum for explaining the operation of the linear amplifier according to the embodiment of the present invention in FIG.

FIG. 7 is a diagram illustrating a configuration of a signal detector in FIG. 2. FIG.

FIG. 8 is a diagram illustrating a configuration of a controller in FIG. 2. FIG.

9 is a view for explaining a procedure of the control unit performs a signal attenuation and phase control function according to an embodiment of the present invention;

10 is a diagram showing the configuration of a linear amplifying apparatus according to a second embodiment of the present invention.

11 is a diagram showing the configuration of a linear amplifying apparatus according to a third embodiment of the present invention.

2 shows a configuration of a linear amplifier according to a first embodiment of the present invention. In FIG. 2, the first variable attenator 211 controls the attenuation of the RF signal gain incident by the attenuation control signal ATT1. A first variable phase shifter 212 inputs the output of the first variable attenuator 211 and controls the phase of the RF signal incident by the phase control signal PIC1.

A predistortor 213 inputs the RF signal, and generates a distortion signal in advance by predicting harmonics, which are intermodulation components to be generated in the power amplifier 214 of the rear stage. The main power amplifier 214 power amplifies and outputs the RF signal output from the predistorter 213. The second delay unit 215 inputs an RF signal output from the power amplifier 214 and outputs the delayed signal for a time when the intermodulation signal is applied. Such a configuration becomes a main path of the linear amplifier according to the embodiment of the present invention.

A power divider 216 divides and outputs an RF signal incident on the main path. The distributor 216 may use a directional coupler. A first delay line 217 compensates for the delay time of the RF signal in the predistortion and amplification process of the main path. The divider 218 is located at the output terminal of the power amplifier 214 and distributes the output of the power amplifier 214 to output. The distributor 218 may use a directional coupler. The signal canceler 219 inputs an RF signal output from the first delay unit 217 and an amplified RF signal output from the power amplifier 214. The canceller 219 detects the intermodulation signal by canceling the RF signal component output by the first delayer 217 at the output of the power amplifier 214. The embodiment of the present invention shows an example in which the canceller 219 is implemented as a subtractor.

The second variable attenuator 220 inputs the intermodulation signal output from the canceller 219 and controls the gain of the intermodulation signal input by the attenuation control signal ATT2 output from the controller 237. The second variable displacement controller 221 inputs a mixed modulation signal output from the second variable attenuator 220 and controls a phase of the mixed modulation signal input by the phase control signal PIC2 output from the controller 237. An error amplifier 222 amplifies and outputs the intermodulation signal output from the second variable phase shifter 221. A combiner 223 couples the output of the error amplifier 222 to the output of the second delay 215. The coupler 223 may use a directional coupler.

Such a configuration corresponds to a sub-path for suppressing intermodulation signals of the main path in an embodiment of the present invention.

The divider 231 distributes the RF signal input at the input terminal and outputs the first signal SF1. The divider 232 is located at an output terminal of the power amplifier 214 to distribute the amplified RF signal to output a second signal SF2. The divider 233 is located at the output of the canceller 219 and distributes the intermodulation signal from which the RF signal is canceled to output the third signal SF3. The divider 234 is disposed at the output terminal and distributes the final RF signal to output the fourth signal SF4. The distributors 231-234 may use directional couplers. A selector 235 inputs the signals SF1-SF4 output from the distributors 231-234, and selects and outputs a corresponding signal SF controlled by a switch control signal SWC (switching control data) output from the controller 237. .

The signal detector 236 detects the strength of the signal SF output from the selector 235 by the control data PCD (PLL Control Data) output from the control unit 237 and outputs a RSSI (Received Signal Strength Indicator) converted into a DC voltage. do. The control unit 237 generates a switch control signal SWC for selecting the corresponding signal SF in the selector 235, and generates a control data PCD for determining a frequency for detecting the strength of the signal SF selected in the signal detector 236.

In addition, the controller 237 analyzes the value of the RSSI signal output from the signal detector 236, and attenuation control for controlling the corresponding variable attenuator and phase shifter to adjust the gain and phase of the corresponding signal SF according to the analyzed result. Generates signals ATT1-ATT3 and phase control signals PIC1-PIC3. First, when selecting the input signal output from the divider 231, the control unit 237 controls the detector 236 to detect the RSSIs of the input RF signal to determine the size thereof, and then determine the frequency component of the input RF signal. Accordingly, when the controller 237 selects the output of the power amplifier 214 output from the splitter 232, the control unit 235 controls the signal detector 236 to detect the RSSIs of the harmonic signals of the amplified RF signal, and then determines the magnitude. Generating an attenuation control signal ATT3 and a phase control signal PIC3 for adjusting the attenuation and phase of the intermodulation signal. Secondly, when the output of the canceller 219 is selected, the controller 237 controls the signal detector 236 to detect RSSIs of the RF signals included in the canceled intermodulation signal to determine the size, and then to the input terminal of the linear amplifier. Attenuation control signal ATT1 and phase control signal PIC1 for adjusting the attenuation and phase of the incident RF signal are generated. Third, when the amplified signal is finally output, the controller 237 controls the signal detector 236 to detect RSSIs of intermodulated signals included in the final output signal to determine a magnitude thereof, and then outputs the intermodulator. Attenuation control signal ATT2 and phase control signal PIC2 for attenuation and phase adjustment of the signal are generated.

The linear amplifier according to the embodiment of the present invention having the configuration as described above uses a predistortion method and a feedforward method to remove intermodulation signals that may be generated during the amplification process. In an embodiment of the present invention, the predistorter 213 primarily removes the intermodulation signal output from the power amplifier 214. To this end, the preamplifier 213 anticipates and generates harmonics that may be generated during amplification in the power amplifier 214, and may be generated in the power amplifier 214 at the time when the power amplifier 214 is applied to the power transistor of the power amplifier 214. Adjust the phase so that it is out of phase with the harmonics present.

In the case of using the predistortion method as described above, the intermodulation signal generated in the linear amplifier cannot be completely removed. Therefore, the linear amplifier according to the embodiment of the present invention applies a feedforward method to suppress the intermodulation signal after the first suppression of the intermodulation signal in the predistorter 213. The linear amplifier using the feed forward method cancels the pure RF signal component from the output of the power amplifier 214 to extract the intermodulation signal, and combines the extracted intermodulation signal to the combiner 223 to cancel the intermodulation component. Therefore, when the feedforward method is used, the intermodulated signal component included in the amplified signal at the final output terminal of the linear amplifier is suppressed to output only the amplified pure RF signal component.

As described above, according to the exemplary embodiment of the present invention, first, the intermodulation signal generated in the amplification process of the power amplifier 214 is first suppressed using the predistortion method, and the intermodulation signal included in the output of the first suppressed power amplifier 214 is used. Second suppression using a feedforward method. For convenience of explanation, the operation of suppressing the intermodulation signal by the predistortion method will be described first, and the operation of suppressing the intermodulation signal by the feed forward method will be described.

6A and 6B of FIG. 6A and 6B are diagrams illustrating the characteristics of signals generated according to the respective sub-operations in FIG. 2, and assuming two tones. 6a is an input RF signal. 6b is a harmonic signal of the RF signal generated by the harmonic generator 314 in the predistorter 213. The 6c is a signal whose phase is adjusted so that the magnitude of the harmonics is adjusted by the variable attenuator 315 in the predistorter 213 and is incident to the power amplifier 214 in the reverse phase by the variable phase 316. The 6d is an amplified RF signal including an intermodulation signal by amplifying the predistorted signal incident as shown in 6c in the power amplifier 214. 6e is a mixed modulated signal extracted by canceling the signal component of 6a from the amplified RF signal of 6d in canceller 219. The 6f is a signal adjusted by adjusting the magnitude of the intermodulation signal such as the 6e and out of phase with the output of the power amplifier 214 on the main path. The 6g is a final output signal that suppresses the intermodulation signal by combining an amplified RF signal such as 6d and an extracted intermodulation signal such as 6f out of phase.

FIG. 3 is a diagram illustrating an internal configuration of the predistorter 213 in FIG. 2. Referring to FIG. 3, the divider 312 is located at the input terminal to distribute and output an RF signal. The Automatic Level Control (ALC) 313 maintains a constant level of the RF signal incident on the harmonic generator 314 to generate a constant harmonic regardless of the level change of the incident RF signal. The harmonics generator 314 inputs an RF signal adjusted in the automatic level controller 313 to generate third, fifth, seventh, and higher harmonics of the RF signal. The variable attenuator 315 inputs a harmonic signal output from the harmonic generator 314 and controls the gain of the harmonic component by the attenuation control signal ATT3 output from the controller 237. The variable phase 316 inputs a harmonic signal output from the harmonic generator 314 and adjusts the phase of the harmonic component by the phase control signal PIC3 output from the controller 237. The delay unit 311 delays the RF signal incident to the main path during the time period during which the predistortion signal is generated. A combiner 317 is located between the output of the delayer 311 and the input of the power amplifier 214 and couples the predistortion signal to the delayed RF signal.

Referring to FIG. 3, the harmonic generator 314 may include a coupler and a shottkey diode. Then, when the RF signal is incident on the Schottky diode, the Schottky diode generates higher harmonics according to the level of the incident RF signal. Therefore, the level of the RF signal incident on the Schottky diode should be set to a level capable of best suppressing the intermodulation signal included in the output of the power amplifier 214. To this end, an automatic level controller 313 is positioned at the front of the harmonic generator 314 so that an RF signal of a constant level is always incident.

The automatic level controller 313 controls and outputs an RF signal having a predetermined level regardless of the level change of the RF signal incident on the linear amplifier. 4 is a diagram showing the configuration of the automatic level controller 313. A divider 414 is positioned at an input of the harmonic generator 314 to distribute and output a level-adjusted RF signal applied to the harmonic generator 314. The power detector 415 then converts the RF signal into a DC voltage and outputs it to a level controller 416. Then, the level controller 416 controls the variable attenuator 412 according to the DC voltage output to the power detector 415 so that an RF signal of a constant level is always input to the harmonic generator 314.

In this case, the power detector 415 of FIG. 4 should be able to detect a multi-carrier. That is, the power detector 415 should be able to input the RF signal of the multi-carrier and convert it to a DC voltage. FIG. 5 is a diagram illustrating the configuration of the power detector 415. An RF transformer 451 inputs an RF signal to generate two signals having a 180 ° phase difference. The two signals output from the transformer 451 are transmission lines. It is converted to DC level through Schottky diodes 454 and 455 through 452 and 453, and then composite rectified through capacitor 456 and resistor 457 and output as DC voltage.

Referring to FIGS. 3 and 4, the operation of controlling the level of the incident RF signal is performed. The 180 ° transformer 451 of the power detector 415 generates two signals that are separated and output in half-cycle units of the incident RF signal. Schottky diodes 454 and 455 convert two signals incident through transmission lines 452 and 453 to DC levels, respectively. Therefore, the average power of the multi-carrier can be sensed without error, thereby accurately converting the level of the RF signal incident on the harmonic generator 314 to a DC voltage.

Then, the level controller 416 generates a control signal according to the DC voltage level of the RF signal output from the power detector 415 and applies it to the variable attenuator 412. The level controller 313 may be implemented using an operational amplifier or the like. At this time, the control signal output from the level controller 313 generates a control signal to increase the attenuation control when the voltage value is large according to the DC voltage of the detected RF signal, and to reduce the attenuation control when the voltage value is small. Then, the variable attenuator 412 variably attenuates the RF signal to have a constant level irrespective of the level of the incident RF signal and enters the harmonic generator 314.

At this time, if the variation level of the incident RF signal is 10dB, the operating area of the automatic level controller 313 should be designed to control the level to at least 10dB or more. In addition, the RF output level of the automatic level controller 313 must be set such that the harmonic generator 314 can be generated as a predistortion signal capable of maximally suppressing the intermodulation signal generated by the power amplifier 214. Therefore, the harmonic generator 314 inputting the output of the automatic level controller 313 always enters an RF signal of a constant level, thereby stably generating harmonics. Since the harmonics output from the harmonic generator 314 are combined with the RF signal and incident on the power amplifier 214, the power amplifier 214 can suppress the generation of the intermodulation signal in the process of amplifying the RF signal.

In addition, the harmonics generated as described above should be adjusted to the magnitude and antiphase of harmonics that may be generated in the amplification operation when incident on the power amplifier 214. The variable attenuator 315 and the variable phase 316 shown in FIG. 3 adjust the magnitude of the harmonics generated by the magnitude of the intermodulation signal that the power amplifier 214 may generate in the amplification operation, and enter the adjusted harmonics in reverse phase. Adjust the phase so that it can be.

The control unit 237 controls the selector 235 to select the output of the power amplifier 214 output from the divider 232, and controls the detector 236 to determine the signal strength RSSI of the intermodulation signal at the output of the power amplifier 214 such as 6d. To be detected. Attenuation control signal ATT3 and phase control for controlling the power amplifier 214 to smoothly suppress the intermodulation signal by comparing and analyzing the RSSI value of the intermodulation signal output from the detector 236 and the RSSI value in the previous state. Generate signal PIC3.

Then, the variable attenuator 315 adjusts the magnitude of the predistortion signal generated by the harmonic generator 314 by the attenuation control signal ATT3, and the variable phase 316 is a power amplifier 214 by the phase control signal PIC3. Adjust the phase so that it can be incident in antiphase. As described above, the harmonic signal generated by the harmonic generator 314 is adjusted in magnitude and phase, and the combiner 317 couples the intermodulation signal to the input terminal of the power amplifier 314. In this case, as shown in FIG. 6A, the delayer 311 delaying the incident RF signal delays the RF signal until the predistortion signal is coupled to the input terminal of the power amplifier 214. Then, it can be seen that the predistortion signal is combined with the RF signal at the input of the power amplifier 214. In this case, as shown in 6c of FIG. 6, the position where the intermodulation signal coupled to the RF signal is adjusted in reverse phase is preferably the input terminal of the power transistor of the power amplifier 214.

As described above, the predistorter 213 generates a predistortion signal in advance by predicting the intermodulation signal to be generated by the power amplifier 214, and attenuation and phase of harmonics so that the intermodulation signal can be suppressed to the maximum in the power amplifier 214. Control to enter the power amplifier 214. At this time, the predistorter 213 mainly removes the third harmonic generated at the highest level among the harmonics that may be generated by the power amplifier 214. The pre-distortion intermodulation signal elimination effect can significantly reduce the burden of suppressing the intermodulation signal by applying a feed forward method. This has the advantage that the feedforward scheme can be improved by a few dB with predistortion because the adjustment is very precise and difficult.

Secondly, after the first suppression of the intermodulation signal that may be generated by the power amplifier 214 by the predistortion method as described above, the second operation to suppress the intermodulation signal that was not suppressed by the feedforward method will be described. . The process of removing the intermodulation signal of the power amplifier 214 in the feedforward method can be largely divided into two steps. One is to extract the pure intermodulation signal component by canceling the RF signal component incident to the output of the power amplifier 214, and the other is intermodulation included in the signal finally output from the power amplifier 214 After correcting the magnitude and phase to completely remove the signal, cancel the intermodulation signal components at the output of the power amplifier 214.

First, the first step operation of the feedforward method will be described. The splitter 216 on the auxiliary path distributes the RF signal incident as shown in 6a of FIG. 6A, and the first delayer 217 delays the RF signal distributed by the splitter 216 for the predistortion and RF amplification time, and then Applied to offset 219. Then, the RF signal components as shown in 6a of FIG. 6a and the amplified signals as shown in 6d of FIG. 6b distributed by the divider 218 to be canceled from the first delayer 217 cancel each other and thus pure horn as shown in 6e of FIG. 6b. The modulated signal component is extracted and output.

As described above, the canceller 219 is a core configuration of the feedforward method, and its function is to detect only the intermodulated signal component at the output of the power amplifier 214. The canceller 219 may be configured in the form of a subtractor or an adder. When the canceller 219 is configured as a subtractor, the two RF signals to be input should be adjusted to have a phase so that they are in phase. When the adder is configured as an adder, the two RF signals to be input should be adjusted so as to have an inverse phase. The embodiment of the present invention shows an example in which the canceller 219 is configured as a subtractor. In this case, the subtractor has a coupler therein, and an input signal of two input signals is incident to the combiner in phase and the other signal is converted to an antiphase to enter the combiner. When the RF signal as shown in 6a of FIG. 6A and the amplified RF signal as shown in 6d of FIG. 6B are incident on the subtractor 219 of the subtractor type, two RF signal components of the in-phase are converted into an antiphase inside the canceller 219. After passing through a post-combiner (you can use a Wilkinson combiner here), the RF signal cancels out, leaving only intermodulation signal components.

At this time, the level and phase of two RF signals incident on the canceller 219 must be exactly matched. To this end, the group delay of the amplified RF signal output from the power amplifier 214 of the main path and the RF signal input through the auxiliary path must be exactly matched in the band, and the characteristics of the flatness of the delay are improved. Should be good. That is, the phase distortion of the RF signal to be canceled should be suppressed as much as possible.

As described above, if the level and the phase of the output of the power amplifier 214 and the RF signal component output from the first delay unit 217 do not exactly match, the RF signal component is not canceled out correctly in the canceller 219. To solve this problem, the first variable attenuator 211 of FIG. 2 adjusts the level of the RF signal incident by the attenuation control signal ATT1 output from the controller 237, and the second variable displacement unit 212 outputs the controller 237. The phase of the RF signal incident by the phase control signal PIC1 is adjusted. Therefore, the first variable attenuator 211 and the first variable displacement unit 212 perform a function of adjusting the RF signal of the main path and the RF signal of the auxiliary path to the same level and phase. The canceller 219 cancels the two RF signal components that are input at the same level and in phase.

In order to control the level and phase of the two RF signals as described above, the controller 237 outputs a switch control signal SWC for selecting the third signal SF3 to the selector 235, and the detector 236 outputs an RF signal to the third signal SF3. The control data PCD for detecting the RSSI of the signal component is output. The selector 235 selects and inputs a third signal SF3 which is an output of the canceller 219 distributed by the divider 233, and the detector 236 generates an RSSI obtained by converting an RF signal component of the third signal SF3 into a DC voltage. . Then, the controller 237 compares the RSSI of the RF signal component with the previous RF signal RSSI, and then generates an attenuation control signal ATT1 and a phase control signal PIC1 for canceling the RF signal component in the canceller 233.

Then, the first variable attenuator 211 attenuates the RF signal incident by the decay rate determined by the attenuation control signal ATT1, and the first phase variable 212 adjusts the phase of the RF signal incident by the phase control signal PIC1. . At this time, the attenuation control signal ATT1 and the phase control signal PIC1 are generated by comparing and analyzing the RSSI of the RF signal outputting the canceller 219 and the RSSI of the previous RF signal, and thus, the first variable attenuator 211 and the first variable shifter 212. FIG. 6B controls two RF signals such as 6d of FIG. 6B and two RF signals of 6A of FIG. 6A to have the same level and the same phase.

The reason for canceling the RF signal component in the canceller 219 is to suppress the RF signal greatly and extract only the intermodulated signal component, so as not to affect the error amplifier 222 at the rear stage. That is, if the output of the canceller 219 fluctuates and the RF signal is not effectively removed, the RF amplifier of a relatively large level is incident on the error amplifier 222, thereby causing the error amplifier 222 to be damaged.

Secondly, the operation of the second step in the feedforward method will be described. Here, as described above, the intermodulation signal output from the canceller 219 is adjusted through the second variable attenuator 220, the second variable phase shifter 221, and the error amplifier 222, and is incident on the main path to output the power amplifier 214. The intermodulation signal component included in is removed. In this case, the intermodulation signal coupled by the combiner 223 should be out of phase with the amplified output signal.

Here, in order to correct the intermodulation signal detected by the canceller 219 to be equal to the level of the intermodulation signal included in the signal output on the main path and to be out of phase, the control unit 237 outputs the final output distributed by the distributor 234. A switch control signal SWC is generated for selecting the fourth signal SF4, which is a signal, and a control data PCD for detecting RSSI of harmonics, which are intermodulation signals, is output from the fourth signal SF4. Then, the selector 235 selects and outputs the fourth signal SF4 output from the divider 234 by the switch control signal SWC, and the detector 236 detects the RSSI of the harmonics of the fourth signal SF4 by the control data PCD and controls the controller. Applies to 237. The controller 237 compares the RSSI of the intermodulated signal included in the final output signal with the RSSI of the pre-modulated signal, and then suppresses the mixed modulated signal included in the final output signal according to the analysis result. And a phase control signal PIC2.

Accordingly, the second variable attenuator 220 inputting the output of the canceller 219 adjusts the level of the intermodulation signal incident by the attenuation control signal ATT2, and the second phase adder inputs the signal output from the second variable attenuator 220. The toilet 221 adjusts the phase of the intermodulation signal incident by the phase control signal PIC2. In this case, the second phase variable transformer 221 controls the phase of the mixed modulated signal to be out of phase in the combiner 223 by the phase control signal PIC2. Then, the error amplifier 222 connected between the second variable phase shifter 221 and the combiner 223 amplifies and outputs the mixed modulated signal whose level and phase are adjusted as described above.

As described above, the linear amplification apparatus uses a predistortion method and a feedforward method to suppress intermodulation signals included in an amplified signal. The procedure for suppressing the intermodulation signal first suppresses the intermodulation signal that may be generated in the power amplifier 214 by predistortion, and then detects the intermodulation signal included in the output of the power amplifier 214 by the feedforward method. The intermodulation signal is then combined with the final output signal to remove the intermodulation signal. It is difficult to design and manufacture the power amplifier 214 and the error amplifier 222, and it is difficult to accurately tune the power amplifier 214 and the error amplifier 222 to remove the intermodulation signal by the feedforward method alone. After suppression, the feedforward method removes the remaining intermodulation signals, which facilitates the design and manufacture of the linear amplifier.

Next, the process of suppressing the intermodulation signal using the predistortion method and the feedforward method as described above with reference to the control unit 237 will be described in detail.

7 is a diagram illustrating an internal configuration of the detector 236 according to the embodiment of the present invention. The attenuator 711 attenuates and outputs the signal SF output from the selector 235. Filter 712 is a wideband pass filter that filters signals in a transmission band. The phase lock loop (PLL) 713 and the oscillator 714 generate a corresponding local frequency LF1 by the control data PCD output from the controller 237. The local frequency LF1 determines a frequency for detecting the RSSI of the selected signal SF. A mixer 715 generates an intermediate frequency (IF) by mixing the signal output from the filter 712 and the local frequency LF1. The filter 716 is an intermediate frequency filter and filters the difference signal (# SF-LF1 #) of two frequencies at the output of the mixer 715 and outputs it to IF1. The intermediate frequency amplifier 717 amplifies and outputs the intermediate frequency IF1. Oscillator 719 generates a fixed local frequency LF2. A mixer 718 generates an intermediate frequency IF2 by mixing the IF1 signal output from the intermediate frequency amplifier 717 and the local frequency LF2. The filter 720 filters the difference signal (# IF1-LF2 #) of two frequencies at the output of the mixer 718 and outputs it to IF2. A log amplifier 721 converts the intermediate frequency IF2 output from the filter 720 into a DC voltage and outputs the RSSI signal.

Referring to the operation of FIG. 7, the selector 235 selects and outputs a corresponding signal SF among the first signals SF1 to fourth signal SF4 by the switch control signal SWC of the controller 237. Filter 712 of detector 236 then filters and applies the signal SF to mixer 715. The PLL713 and the oscillator 714 generate a local frequency LF1 for selecting harmonics or RF signals of a signal selected by the control data PCD of the controller 237. The mixer 715 mixes and outputs the two signals SF and LF1, and the filter 716 filters the frequency corresponding to the difference between the two signals and outputs the result to IF1. The above configuration determines the frequency for detecting the RSSI in the selected signal SF and performs the frequency down conversion function of the first step.

The mixer 718 then mixes the local frequency LF2 output from the oscillator 718 and the IF1, and the filter 720 filters the frequencies corresponding to the difference between the two signals IF1 and LF2 in the mixed signal and outputs them to IF2. The above configuration performs the frequency down conversion function of the second step. The log amplifier 721 receives the IF2 and converts the DC voltage into a DC voltage. The signal becomes RSSI.

8 is a diagram illustrating an internal configuration of the control unit 237 according to the embodiment of the present invention. The analog-to-digital converter (ADC) 814 converts the RSSI output from the selector 236 into digital data and outputs the digital data. ROM812 stores a program for controlling attenuation and phase in accordance with an embodiment of the present invention. The CPU811 generates a switch control signal SWC for selecting a signal SF and a control data PCD for selecting a frequency for selecting a desired RSSI from the selected signal SF according to the program of the ROM812. The CPU811 outputs the RSSI value output to the ADC814. Comparative analysis generates the attenuation control signal ATT and the phase control signal PIC. The RAM 813 temporarily stores various data generated while the program is being executed. The DAC815 converts the attenuation control and phase control data output from the controller 811 into analog and outputs the analog attenuation control signal ATT and the phase control signal PIC. The communication unit 816 performs a function of notifying the state information of the linear amplifier to the outside under the control of the CPU816.

FIG. 9 is a diagram for describing an operation of controlling, by the controller 237, the variable attenuators and the variable phases to adjust the level and phase of a signal according to an embodiment of the present invention. In FIG. 9, the X axis represents the attenuation value and the Y axis represents the phase change value. Referring to FIG. 9, when the value of the variable attenuator is changed from PA to PB at the time when the RSSI is input, the size of the detected signal is reduced to move from PB to PC. Thereafter, when the value of the variable attenuator is moved from the PC to the PD at the time when the next RSSI is input, when the detected signal is increased again, the variable attenuator moves to the opposite direction PC. This is a temporary point in the attenuation value PC size. In this way, the variable phase shifter also moves to the PF when the size of the RSSI detected when the PE value is changed in the PC becomes small.

10 shows the configuration of a linear amplifier according to a second embodiment of the present invention. The linear amplifier of FIG. 10 has the same configuration as the linear amplifier according to the first embodiment of FIG. 2 except for the configuration in which the first variable attenuator 211 and the first variable displacement unit 212 are located in a subpath. .

Referring to FIG. 10, the predistorter 213 on the main path has the configuration as shown in FIGS. 3 to 5, generates harmonics corresponding to the input RF signal, and the attenuation control signal ATT3 and the phase control signal PIC3 of the controller 237. In accordance with the control, the level and phase of the harmonics are combined. The signal is combined with the input RF signal and converted into a predistorted RF signal and output to the power amplifier 214. The power amplifier 214 inputs an output from the predistorter 213 and outputs an RF signal in which a mixed component is suppressed while amplifying the predistorted RF signal.

The first delay unit 217 on the subpath inputs the RF signal distributed in the main path by the divider 216, and delays the RF signal during the processing time in the predistorter 213 and the power amplifier 214. The first variable attenuator 211 and the first variable displacement unit 212 are connected between the first delay unit 217 and the offset unit 219, and are configured to control the RF signal input by the attenuation control signal ATT1 and the phase control signal PIC1 output from the control unit 237. The level and phase are respectively controlled and output to the canceller 219.

In addition to the above structure, the rest of the linear amplifier device is the same as the linear amplifier device of the first embodiment as shown in FIG. The controller 237 selects and inputs the first signals SF1-SF4, and detects the RSSI of the intermodulation signal or the RF signal from the selected signal SF to generate the attenuation control signals ATT1-ATT3 and the phase control signals PIC1-PIC3. The control unit 237 first sets service channels, sequentially adjusts the level and phase of the predistortion signal for suppressing the intermodulation signal included in the power amplifier 214, and adjusts an RF signal component included in the canceller 219. The level of the modulated signal component output from the canceller 29 is adjusted so that the level and phase of the RF signal input to the auxiliary path are suppressed to suppress the intermodulated signal component included in the final amplified RF signal. And adjust the phase.

11 shows the configuration of a linear amplifier according to a third embodiment of the present invention. The linear amplifier of FIG. 11 includes a linear amplifier according to the first embodiment of FIG. 2 except for a configuration in which the first variable attenuator 211 and the first variable displacement unit 212 are located between a main path and an auxiliary path. Have the same configuration.

Referring to FIG. 11, the predistorter 213 on the main path has the configuration as shown in FIGS. 3 to 5, generates harmonics corresponding to the input RF signal, and the attenuation control signal ATT3 and the phase control signal PIC3 of the controller 237. In accordance with the control, the level and phase of the harmonics are combined. The signal is combined with the input RF signal and converted into a predistorted RF signal and output to the power amplifier 214. The power amplifier 214 inputs an output from the predistorter 213 and outputs an RF signal in which a mixed component is suppressed while amplifying the predistorted RF signal.

The first delay unit 217 on the subpath inputs the RF signal distributed in the main path by the divider 216, and delays the RF signal during the processing time in the predistorter 213 and the power amplifier 214 to the canceller 219. Output

The first variable attenuator 211 and the first variable shifter 212 are connected between the divider 218 and the canceller 219, and the level of the RF signal input by the attenuation control signal ATT1 and the phase control signal PIC1 output from the controller 237. Phases are respectively controlled and output to the canceller 219. That is, the first variable attenuator 211 and the first variable displacement unit 212 are located between the main path and the auxiliary path, and control the phase and level of the amplified RF signal output from the power amplifier 214 on the main path. Output to canceler 219 on path.

In addition to the above structure, the rest of the linear amplifier device is the same as the linear amplifier device of the first embodiment as shown in FIG.

The controller 237 selects and inputs the first signals SF1-SF4, and detects the RSSI of the intermodulation signal or the RF signal from the selected signal SF to generate the attenuation control signals ATT1-ATT3 and the phase control signals PIC1-PIC3. The control unit 237 first sets service channels, sequentially adjusts the level and phase of the predistortion signal for suppressing the intermodulation signal included in the power amplifier 214, and adjusts an RF signal component included in the canceller 219. Adjust the level and phase of the RF signal output from the power amplifier 214 to suppress, and to suppress the intermodulation signal component included in the final amplified RF signal output of the intermodulation signal component output from the canceller 29 Adjust the level and phase.

The linear amplifier of the second embodiment having the configuration as shown in FIG. 10 and the linear amplifier of the third embodiment having the configuration as shown in FIG. 11 are first serviced in the same manner as the linear amplifier according to the first embodiment. Select the channel, secondly control the phase and level of the pre-distortion signal, thirdly control the phase and level of the RF signal input, and fourthly, phase and phase of the intermodulation signal component output from the canceller 219. Control the level. However, as described above, the operation of selecting the service channel as another control method may be performed at a predetermined time interval by a timer interrupt. When using this control method, the control unit 237 generates a timer interrupt every time. The service channel discovery operation is performed, and the remaining periods control the variable attenuators and the variable phases as described above. At this time, if a timer interrupt occurs in the state of controlling the random variable attenuator and the variable phase, the control unit 237 stops the current operation, performs the timer interrupt service routine, returns to the main routine, and re-executes the operation. .

Also, as in the linear amplifier according to the first embodiment, the number L, M, and N of controlling the variable attenuators and the variable phases effectively control the level and phase of the signal input from the corresponding variable attenuator and the variable phase. It can be set to a number that can be controlled, and in the embodiment of the present invention, the same number is set, and the number is assumed to be five times.

As described above, the linear amplifier according to the embodiment of the present invention can effectively control the intermodulation signal components by using the predistortion method and the feedforward method. In other words, the pre-distortion method first suppresses the intermodulation signal that may occur in the power amplifier, and the feed-forward method suppresses the intermodulation signal component included in the output of the power amplifier. By using this method, it is easy to design and manufacture the power amplifier 214 or the error amplifier 222. In addition, the variable attenuators and the phase shifters that perform the linearization function have a good bandwidth in terms of frequency characteristics, relatively good flatness, and good variable characteristics, which can be used for other purposes.

Claims (3)

In the intermodulation signal removal device of the linear amplifier having a power amplifier, Generating harmonics corresponding to the input RF signal and generating a predistortion signal by combining the harmonics with the RF signal to first suppress the intermodulation signal generated when the RF signal is amplified by the power amplifier, the input RF signal and the Linear amplification device characterized in that the output of the power amplifier to cancel the intermodulation signal component to extract the error amplification, and the amplified intermodulation signal and the output of the power amplifier to second suppress the intermodulation signal In a linear amplifier, A first variable attenuation and phase shifter positioned on a main path to adjust a level and a phase of an input RF signal; A predistorter for generating harmonics corresponding to the RF signal output to the variable attenuation and phase shifter and then being coupled to the RF signal to generate a predistorted RF signal; A power amplifier for amplifying and outputting the predistorted RF signal; A first delay located on an auxiliary path and delaying the RF signal distributed in the main path; An canceller positioned on the auxiliary path to cancel an intermodulation signal included in an amplified RF signal by canceling an output of the power amplifier and an output of the first delayer distributed on the main path; A second variable attenuation and phaser for adjusting the level and phase of the intermodulation signal output from the canceller; An error amplifier for amplifying the intermodulation signal output from the second variable attenuation and phase shifter; A second delay unit for delaying an output of the power amplifier; And a combiner configured to couple the intermodulated signal output from the error amplifier to an output of the second delay unit to suppress the intermodulated signal included in the final RF signal. In the method of removing the intermodulation signal of a linear amplifier having a power amplifier, Generating harmonics corresponding to the input RF signal and generating a predistortion signal by combining the harmonics with the RF signal to first suppress the intermodulation signal generated when the RF signal is amplified by the power amplifier, the input RF signal and the The horn of the linear amplifier device, characterized in that to cancel the mixed modulated signal component by canceling the output of the power amplifier, error amplification, and second suppress the mixed modulated signal by combining the amplified mixed modulated signal and the output of the power amplifier. How to remove the modulated signal.