KR100375315B1 - Mixer for reducing of distortion - Google Patents

Abstract

Provided is an improved mixer for good linearity in frequency conversion. The improved mixer intermodulates a high frequency signal to be frequency converted to generate a distortion signal corresponding thereto, and a high frequency signal including a predistortion signal capable of phase shifting and attenuating the generated distortion signal to remove the distortion signal. It consists of a predistorter to generate and feed it to the mixer. As described above, the mixer having the predistorter reduces the distortion by eliminating the intermodulation component in the mixer due to the interaction of the intermodulated signal component in the mixer and the predistorted signal component during frequency conversion.

Description

MIXER FOR REDUCING OF DISTORTION

The present invention relates to a mixer for use in a communication system, and more particularly to a mixer that is improved to reduce distortion signal generated when mixing an input signal or a carrier wave with a local oscillation frequency.

Typically, a communication system uses a mixer to frequency convert a signal to be transmitted or a received signal. Such a mixer should have good linearity in nature, but is known to have nonlinear characteristics. In particular, in the case of wireless transceivers that use multiple carriers or frequency-efficient digital modulation schemes such as quadrature phase shift keying or quadrature amplitude modulation, the nonlinear characteristics of the mixer Due to the inter-conversion signal distortion component caused by the problem, the performance of the entire wireless transceiver is seriously degraded. Therefore, in the case of the radio transceiver having the digital modulator, the linearity of the mixer has to be improved.

A general method of improving the linearity of a mixer used in a wireless transmission / reception system using a digital modulation and demodulation method has been to control the power of a local oscillator supplying a local oscillation frequency to the mixer. Such control utilizes the characteristic that the inter-modulation occurring in the mixer decreases as the power of the local oscillator driving the mixer increases. However, the method of controlling the power of the local oscillator connected to the mixer has a low degree of attenuation of intermodulation, and causes a problem that the cost is excessively increased when using a mixer capable of withstanding high local oscillation frequency power.

Accordingly, an object of the present invention is to provide an apparatus for improving the linearity of a mixer using an input predistorter.

Another object of the present invention is to provide an apparatus for reducing intermodulation in a mixer by generating a predistortion signal capable of canceling a distortion signal generated in a mixer in response to a signal input as a predistorter.

The present invention for achieving the above object is a mixer for generating a frequency-converted signal by mixing a high frequency signal and a local oscillation frequency of a predetermined frequency; The mixer generates a distortion signal corresponding to the high frequency signal to be input to the mixer and generates a distortion signal. The mixer generates a high frequency signal including a predistortion signal capable of phase shifting and attenuating the generated distortion signal to remove the distortion signal. A predistorter provided to improve the linearity of the mixer by the interaction of the signal of the intermodulation component and the predistortion signal in the mixer; Characterized in that it comprises a frequency filter for filtering the output of the mixer to a predetermined band and outputs.

The predistorter according to the present invention generates at least one distortion path having a distortion signal generator for generating a phase shift by generating a distortion signal generated by intermodulation in response to an input high frequency signal, and generating the distortion signal from the input high frequency signal. At least one delay path for delaying for a period, a plurality of dividers for dividing the high frequency signal into at least one or more distortion paths and delay paths, and the input of the distortion path and the signal on the delay path in combination; And a synthesizer for generating a predistortion signal corresponding to the intermodulation of the high frequency signal to be provided to the mixer.

As described above, the present invention generates a predistortion signal corresponding to the high frequency signal input to the mixer and generates a predistortion signal corresponding to the predistorted signal and generates the predistorted signal and the mixer by mixing the local oscillation frequency. The linearity of the mixer is increased due to the cancellation of the distortion signal by the interaction of the mutual defense components.

1 shows the configuration of a mixer for reducing distortion in accordance with a preferred embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

10, 12: distributor 14: intermodulation signal generator

16, 24: ideal phase 18, 26: attenuator

20, 28: delay 22, 30: synthesizer

32: mixer

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, in the following description of the present invention, it should be noted that a detailed description of a function or configuration for a known technical configuration may be omitted if it is determined that the present invention may unnecessarily obscure the subject matter of the present invention.

1 is a diagram illustrating a configuration of a mixer for reducing distortion according to a preferred embodiment of the present invention.

Now, when a high frequency signal is input to the input terminal INPUT, the high frequency signal is distributed by the divider 10 to the input of the delay path PC and another divider 12. At this time, the divider 12 divides the input high frequency signal into a distortion path PA and a delay path PB and outputs the same. These dividers 10 and 12 can use 3 dB couplers.

The high frequency signal input on the distortion path PA is amplified to a predetermined level by the intermodulation signal generator 14 and supplied to the input terminal of the phase shifter 16 connected to the output terminal thereof. In this case, the signal input to the phase shifter 16 includes an intermodulation component due to the amplification of the intermodulation signal generator 14. As the intermodulation signal generator as described above, an amplifier or the like may be used.

The phase shifter 16 shifts the phase of the amplified input signal at an angle corresponding to the set value, and the attenuator 18 connected to the output is output by adjusting the magnitude of the phase shifted signal. Accordingly, it can be seen that the final output of the distortion path PA is a signal that is intermodulated by the intermodulation signal generator 14 and is distorted. The final output of the distortion path PA is fed to one side of synthesizer 22 consisting of a 3dB combiner.

A retarder 20 connected between one output terminal of the splitter 12 and another input terminal of the combiner 22 delays the output of the splitter 12 during the time that the high frequency signal passes from the intermodulation signal generator 14 to the attenuator 18. Accordingly, the combiner 22 combines and outputs a high frequency signal that is not distorted by the delay path PB and a signal that is only a predetermined delay and that is distorted by the distortion path PA. That is, since the combiner 22 subtracts and outputs the delayed high frequency signal from the high frequency signal including the distortion signal, only the signal distorted by the distortion path PA is detected at the output node P1. Therefore, it is required to adjust the phase and magnitude of the high frequency signal by appropriately adjusting the phase 16 and the attenuator 18 so that only the distorted signal is detected at the output node P1 of the divider 22. The output of the synthesizer 22 is phased by the phaser 24 and the attenuator 26 and scaled to provide an input of the second synthesizer 30 connected to the output node.

On the other hand, the retarder 28 located on the delay path PC appropriately delays the high frequency signal output from one output terminal of the distributor 10. For example, the high frequency signal input during the delay time on the delay path PB and the total operation time of the distortion path by the attenuator 24 and the attenuator 26 connected to the output thereof is delayed and provided to the synthesizer 30. Therefore, the synthesizer 30 synthesizes the high-frequency signal through the delay path PC and the distorted signal primarily detected through the distortion path and the delay paths, and finally outputs the predistorted signal to the output node P2. By the above operation, the high frequency signal including the predistortion signal is input to one side of the mixer 32. Phase 24 and attenuator 26 shall be adjusted appropriately to minimize distortion at the output of mixer 32.

The mixer 32 outputs a frequency converted signal by mixing a high frequency signal including the predistorted signal and a local oscillation frequency LO input to another terminal. In this case, in the mixer 32, an interaction between the intermodulation component generated during the frequency conversion and the signal distorted by the predistorter occurs, and the linearity of the mixer is greatly improved due to the interaction of the two signal components. The nonlinear components whose phases and magnitudes of the predistorter are adjusted thus remove the nonlinear components of the mixer 32 generated during the frequency conversion process. The process of removing the nonlinear components of the mixer 32 will be described below. First, the transfer function of the predistorter may be expanded into a Taylor series as shown in Equation 1 below. here, Is a high frequency signal including the predistortion signal output from the predistorter, Is an integer value, Is the input signal. Input signal To In this case, the intermodulation signal component is generated due to the nonlinearity of the predistorter, and the predistorter output signal is expressed by Equation 2 below. The output signal of the predistorter as shown in Equation 2 becomes the input signal of the mixer 32 together with the local oscillation frequency LO, and the transfer function of the mixer 32 can be developed as shown in Equation 3 below in the Taylor series. here Is an integer, Is the sum of the local oscillation frequency LO input to mixer 32 and the output signal of the predistorter. That is, after applying the local oscillation frequency LO and the output signal of the predistorter to the input of the mixer 32, and passing the output of the mixer 32 through the low pass filter 34, a frequency-converted signal as shown in Equation 4 is output. here Denotes a state in which the phase is delayed. And from equation (4) ego, If the condition is satisfied, the intermodulation components may cancel each other out. Therefore, nonlinear components of mixer 32 can be removed by properly adjusting the magnitude and phase of the distortion signal generated by the predistorter using ideal phase 16 and attenuator 18. Also, a low pass filter 34 connected to the output node of mixer 32 Removes the unwanted wave by filtering only the signals below the preset band. Therefore, the distortion of the whole of the mixer 32 can be further reduced.

As described above, the present invention provides a distortion signal corresponding to the intermodulation component of the high frequency signal input to the mixer by providing a predistorter at the front of the mixer, and provides the mixer to the mixer, thereby providing distortion to the mixer. By reducing the linearity can be improved.

Claims (3)

In a mixer that reduces distortion, A mixer for mixing a high frequency signal with a local oscillation frequency of a predetermined frequency to generate a frequency converted signal; Generating a distortion signal corresponding to the modulated high frequency signal input to the mixer, and generating a high frequency signal including a predistortion signal capable of phase shifting and attenuating the generated distortion signal to remove the distortion signal. A predistorter, and by supplying a high frequency signal to be frequency-converted by the mixer to the mixer through the predistorter, the nonlinear portion is canceled by the interaction of the intermodulation signal component and the predistortion signal in the mixer, And linearizing the frequency converted signal. The mixer of claim 1, further comprising a low pass filter for filtering and outputting the output of the mixer to a predetermined band. 2. The predistorter of claim 1, wherein the predistorter comprises at least one distortion path having a distortion signal generator for generating a phase shifted output signal by generating a distortion signal generated by mutual modulation in response to an input high frequency signal, and the distortion of the input high frequency signal At least one delay path for delaying a signal generation period, a plurality of dividers for dividing the high frequency signal into at least one distortion path, and delay paths, and a combination of the distortion path and the signal on the delay path to be inputted. And a synthesizer for generating a predistortion signal corresponding to the intermodulation of the high frequency signal and providing the predistortion signal to the mixer.