KR20110068474A - Method and apparatus for delay mismatch compensation of polar transmetter - Google Patents

Abstract

PURPOSE: A delay time compensating apparatus of polar transmitter is provided to compensate the delay time of a phase modulation signal and an amplitude modulation signal and to increase system performance. CONSTITUTION: An AM(Amplitude Modulation) route delay estimation unit(310) estimates the delay time of an AM signal. An AM delay compensation unit(320) compensates the delay time of the amplitude modulation signal. A PM(Phase Modulation) route delay estimation unit(330) estimates the delay time of an PM signal. An address generator generates a memory address for compensating delay time. A memory(343) outputs a value corresponding to the final input memory address to a phase modulator.

Description

METHOD AND APPARATUS FOR DELAY MISMATCH COMPENSATION OF POLAR TRANSMETTER}

The present invention relates to a technique capable of compensating for the relative difference between the delay time of an amplitude modulation signal and a phase modulation signal inevitably occurring in a polar transmitter.

The present invention is derived as part of the IT source technology development project of the Ministry of Knowledge Economy [National Management No .: 2008-F-001-02, Title: Research on the environment adaptive autonomous control technology of the mobile communication wireless access method].

Next generation wireless communication systems require RF transceivers that support multimode, multibandwidth and multifrequency bands. In such an RF transceiver, in particular, a polar transmitter is recognized as an RF transmitter structure that is most suitable for multimode and multiband transmission. These polar transmitters offer high efficiency by using switching mode RF power amplifiers, such as E-Class power amplifiers, for the synthesis of Amplitude Modulation (AM) and Phase Modulation (PM) signals. To provide. For this reason, current polar transmitters are being applied to systems such as Enhanced Data Rates for GSM Evolution (EDGE) or Wideband Code Division Multiple Access (WCDMA), and development / research to be applied to more broadband systems is underway. Next, a general polar transmitter will be described.

1 is a block diagram of a general polar transmitter.

Referring to FIG. 1, a typical polar transmitter includes a Cartesian-to-Polar converter 110, an amplitude modulator 120, a phase modulator 130, a power amplifier 140, and the like. It consists of a transmitting antenna.

)를 크기 정보 신호(

)와 위상 정보 신호(

)로 변환하여 출력한다. 좀 더 구체적으로, 상기 카테시안-폴라 변환기(110)는 아래의 <수학식 1>과 <수학식 2>을 이용하여, 복소 기저대역 신호(

)를 크기 정보 신호(

)와 위상 정보 신호(

)로 변환한다. 이러한 카테시안-폴라 변환기(110)는 CORDIC 알고리즘을 이용해서 용이하게 구현할 수 있다.The Cartesian-polar converter 110 inputs a complex baseband signal (

) The size of the information signal (

) And phase information signal (

And convert it to). More specifically, the Cartesian-polar converter 110 uses a complex baseband signal (Equation 1) and Equation 2 below.

) The size of the information signal (

) And phase information signal (

To. This Cartesian-polar converter 110 can be easily implemented using the CORDIC algorithm.

과

은 각각 복소 기저대역 신호의 동위상(in-phase) 및 직교위상(quadric-phase) 성분을 의미한다.here,

and

Denotes the in-phase and quadric-phase components of the complex baseband signal, respectively.

)를 위상 변조하고, 위상 변조된 위상 변조 신호를 전력증폭기(140)의 입력단으로 출력한다.The phase information signal θ (n) output from the Cartesian-polar converter 110 is input to the phase modulator 130. The phase modulator 130 uses a voltage controlled oscillator (VCO) and a phase locked loop (PLL) to input an input phase information signal (PLL).

) Is phase-modulated and the phase-modulated phase-modulated signal is output to the input terminal of the power amplifier 140.

)는 진폭 변조기(120)으로 입력된다. 진폭 변조기(120)는 입력된 크기 정보 신호(

)를 진폭 변조하고, 진폭 변조된 크기 변조 신호를 전력증폭기(140)의 바이어스 단자로 출력한다.Meanwhile, the magnitude information signal output from the Cartesian-polar converter 110 (

) Is input to the amplitude modulator 120. The amplitude modulator 120 receives an input magnitude information signal (

) Is amplitude modulated and the amplitude modulated magnitude modulated signal is output to a bias terminal of the power amplifier 140.

The power amplifier 140 synthesizes and amplifies the phase modulated signal input to the input terminal with the magnitude modulated signal. Since the phase modulated signal is an output of the VCO, and is a signal having a constant magnitude and only phase information, the power amplifier 140 uses a Class-D / E / F, which is a switching mode power amplifier, in which linearity is not considered. Efficiency can be greatly improved.

As described above, although the polar transmitter shown in FIG. 1 has advantages in terms of linearity and efficiency, signal-to-noise ratio (SNR) performance is greatly degraded due to time delay mismatch, and out-band (out) is increased as the time delay mismatch increases. A spectral re-growth phenomenon occurs, increasing the amount of interference to the out-band. In particular, inconsistencies in latency cause more severe performance degradation as the bandwidth of the signal increases.

That is, referring to FIG. 1, since the magnitude modulated signal and the phase modulated signal arrive at the power amplifier 140 through independent paths, they have different delay times. The time delay of the magnitude modulated signal is caused by analog elements such as D / A converters and analog filters, and the time delay of the phase modulated signal is generated while passing through D / A converters, analog filters and mixers.

If the power amplifier 140 is a power amplifier having a linear characteristic, the final transmission signal including the discrepancy of the time delay may be represented by Equation 3 below.

는 크기 변조 신호의 시간 지연,

는 위상 변조 신호의 시간 지연,

는 반송파 주파수를 의미한다. In Equation 3,

Is the time delay of the magnitude modulated signal,

Is the time delay of the phase modulated signal,

Denotes a carrier frequency.

The conventional technique for compensating for the delay time mismatch between the time delay of the magnitude modulated signal and the time delay of the phase modulated signal is a technique of estimating the delay time mismatch using the magnitude modulated signal and the phase modulated signal at the power amplifier input. have. This technique performs signal processing such as demodulation and digital conversion of magnitude-modulated and phase-modulated signals through independent paths for delay time estimation. However, this technique adds additional analog delay time mismatch as the magnitude modulated signal and the phase modulated signal pass through independent analog circuits in the process of demodulating and digitally converting the valuable signal from the power amplifier input. Therefore, there is a disadvantage that the accuracy of the delay estimation is not good. The technique also uses cross-correlation to estimate the delay time of the magnitude modulated signal. However, since the magnitude modulation signal has poor correlation characteristics, the delay time estimation result of the magnitude modulation signal using cross-correlation is not accurate.

As described above, in the general polar transmitter illustrated in FIG. 1, since the magnitude modulated signal and the phase modulated signal are transmitted to the power amplifier through different paths, a delay time mismatch between the magnitude modulated signal and the phase modulated signal occurs inevitably. do. This time delay mismatch causes more and more severe system performance degradation as the bandwidth of the signal increases. Accordingly, the present invention provides a system performance improvement by providing a method and apparatus that can compensate for such time delay mismatch.

In addition, since the present invention demodulates and digitally converts the precious signal from the power amplifier output for estimation of the delay time, additional delay time inconsistency in analog signal processing such as precious signal demodulation and digital conversion does not occur. A method and apparatus are provided that can provide more accurate delay time estimation results.

In addition, the present invention can provide a better performance improvement than the prior art by using a higher performance algorithm without using a cross-correlation method to estimate the delay time of the magnitude modulated signal. And an apparatus.

In addition, when estimating the delay time of the magnitude modulated signal and the phase modulated signal simultaneously using a recursive algorithm, there is a possibility that the estimation result may diverge due to the convergence characteristic of the recursive algorithm. Therefore, when the delay time of the phase modulated signal is estimated by using a recursive algorithm, the present invention estimates the delay time of the initial phase modulated signal by using a cross-correlation method, and estimates the delay. It provides a method and apparatus that can reduce the possibility of divergence by allowing time to be used as an initial value of a recursive algorithm.

A method according to the present invention is a method for compensating a delay time difference of a polar transmitter, the method comprising: converting a complex baseband signal into a magnitude information signal and a phase information signal, amplitude modulating the magnitude information signal to generate a magnitude modulation signal, and performing phase information. Phase modulating the signal to generate a phase modulated signal, synthesizing and amplifying the phase modulated signal and the magnitude modulated signal, and demodulating and digitally converting a feedback signal from the power amplifier output using a local oscillation signal to perform a complex basis. A process of generating a band signal, estimating and compensating a delay time of a phase modulated signal using cross-correlation, and a delay time of a magnitude modulated signal using a recursive LMS algorithm. Estimating and compensating.

Using the method and apparatus according to the present invention has the advantage of improving system performance by compensating for the delay time mismatch between the magnitude modulated signal and the phase modulated signal.

In addition, by using demodulation and digital conversion of the precious signal from the output of the power amplifier for estimation of the delay time, it is possible to prevent additional delay time mismatch in analog signal processing such as precious signal demodulation and digital conversion. There is an advantage of estimating and compensating for discrepancies.

In addition, there is an advantage that can provide a better performance than the prior art by using a higher performance algorithm, without using a cross-correlation method to estimate the delay time of the magnitude modulated signal.

In addition, there is an advantage that it is possible to reduce the possibility that the estimation result due to the convergence characteristics of the recursive algorithm can diverge.

Hereinafter, the present invention will be described with reference to the accompanying drawings. In the following description of the present invention, a part obvious to those skilled in the art will be omitted so as not to disturb the gist of the present invention. In addition, it is to be noted that each of the terms described below are only used to help the understanding of the present invention, and may be used in different terms despite the same purpose in each manufacturing company or research group.

The present invention provides a method and apparatus for estimating the time delay of a magnitude modulated signal and a phase modulated signal using a digital signal, and compensating for the time delay of the magnitude modulated signal and the phase modulated signal based on the estimated result.

2 is a block diagram of a polar transmitter according to an embodiment of the present invention.

2, the polar transmitter according to an exemplary embodiment of the present invention further includes a delay time compensator 220 in the general polar transmitter illustrated in FIG. 1.

The delay time compensator 220 may include a delay compensator 221, a delay estimator 223, an A / D converter 225, and a demodulator 227.

The transmission signal s (t) output from the power amplifier 250 and represented by Equation 3 above may be expressed in another form as shown in Equation 4 below.

The transmission signal (RF modulated signal) output from the power amplifier 250 is fed back to the demodulator 227.

)를 RF 변조 시에 사용된 국부 발진기(Local oscillator)를 이용하여 복조한다. 복조기(227) 출력 신호는 디지털 변환기를 통해 디지털 복소 기대대역 신호로 변환되며, 디지털 복조 기저대역 신호들(

)은 아래의 <수학식 5>, <수학식 6>과 같이 표현된다.The demodulator 227 inputs an input transmission signal (

) Is demodulated using a local oscillator used in RF modulation. The demodulator 227 output signal is converted into a digital complex expected band signal through a digital converter, and the digital demodulated baseband signals (

) Is expressed as in Equation 5 and Equation 6 below.

은 이산 신호의 시간 인덱스이고,

와

는 각각 크기 정보 신호와 위상 정보 신호의 샘플 단위 지연 시간을 의미한다.In <Equation 5> and <Equation 6> above

Is the time index of the discrete signal,

Wow

Denotes a sample unit delay time of the magnitude information signal and the phase information signal, respectively.

각각은 아래의 <수학식 7> 내지 <수학식 9>로 표현될 수 있다.In Equation 5 and Equation 6,

Each may be represented by Equations 7 to 9 below.

When Equation 7 to Equation 9 is substituted for Equation 5 and Equation 6, demodulated baseband signals are returned to Equation 10 and Equation 11 below. Can be expressed.

)을 이용하여, 복조 기저대역 신호의 '크기 신호(

)'를 아래의 <수학식 12>와 같이 계산할 수 있다.Also, demodulated baseband signals (

), The 'magnitude signal of the demodulated baseband signal (

) 'Can be calculated as in Equation 12 below.

)과 복조 기저대역 신호들(

)간의 복소 교차-상관(cross-correlation)을 이용하여 추정할 수 있다.Referring to Equations 10 and 11, the demodulated baseband signal is phased only by the delay time of the phase modulated signal. Therefore, the delay time of the phase modulated signal is determined by the baseband signals (the input signals of the Cartesian-polar converter 210).

) And demodulated baseband signals (

Can be estimated using complex cross-correlation between

On the other hand, since the magnitude modulation signal does not have good correlation characteristics, when the delay time of the magnitude modulation signal is estimated using cross-correlation, the error of the estimation result is very large.

)'를 측정 신호로 사용하여 리커시브(recursive) LMS 알고리즘을 이용하여 추정한다.Therefore, in the present invention, the delay time of the magnitude modulated signal is a reference signal based on the magnitude information signal A (n) at the output of the Cartesian-polar converter 210.

) Is used as the measurement signal and estimated using the recursive LMS algorithm.

3 is a block diagram illustrating a specific embodiment of the delay estimator 223 and the delay compensator 221 shown in FIG. 2.

The apparatus shown in FIG. 3 estimates and compensates the delay time of the phase modulated signal using complex cross-correlation, and estimates the delay time of the magnitude modulated signal using a recursive LMS algorithm. And compensate.

2 and 3, the delay estimator 223 includes an AM path delay estimator 310 and a PM path delay estimator 330, and a delay compensator 221. ) Is composed of an AM delay compensator 320 and a PM delay compensator 340.

The AM path delay estimator 310 includes an amplitude calculator 311 and a recursive LMS delay estimator 313 to estimate the delay time of the magnitude modulated signal.

)를 출력한다. 출력된 크기 신호(

)는 리커시브 LMS 지연 추정기(313)로 입력된다.In the AM path delay estimator 310, the amplitude calculator 311 receives the demodulated complex baseband signals and performs the magnitude signal of the demodulated baseband signal through the calculation process of Equation 12 above.

) Output magnitude signal (

) Is input to the recursive LMS delay estimator 313.

)와 카테시안-폴라 변환기(210)에서 출력된 크기 정보 신호(

)를 입력받아 아래의 <수학식 13>의 리커시브 LMS계산과정을 거쳐 크기 변조 신호의 지연 시간을 추정한다.The recursive LMS delay estimator 313 is a magnitude signal output from the amplitude calculator 311.

) And the magnitude information signal outputted from the Cartesian-polar converter 210

) To estimate the delay time of the magnitude modulated signal through the recursive LMS calculation of Equation (13) below.

은 0보다 큰 임의의 정수이고,

는 리커시브 스텝 사이즈(recursive step size)를 의미하는데, 상기

는 0과 1사이의 값이다. 그리고

는

-번째 리커시브 순번에서의 크기 변조 신호의 지연 시간 추정값을 의미한다.In Equation 13 above,

Is any integer greater than zero,

Means a recursive step size,

Is a value between 0 and 1. And

Is

The delay time estimate of the magnitude modulated signal in the -th recursive order.

)은 AM 지연 보상부(320)로 입력된다.The delay time of the magnitude modulated signal estimated by the recursive LMS delay estimator 313 (

) Is input to the AM delay compensation unit 320.

The AM delay compensation unit 320 includes an address generator 321 and a memory 323 to compensate for the delay time of the magnitude modulated signal.

)을 차감하여 생성한다. 이렇게 생성된 메모리 주소(Address)는 메모리(323)로 입력된다.The address generator 321 receives a delay time of the magnitude modulated signal estimated by the recursive LMS delay estimator 313 and generates a 'memory address' for delay compensation. Here, 'memory address' is the delay time of the magnitude modulated signal estimated from the current memory address value.

Create by subtracting). The generated memory address is input to the memory 323.

The memory 323 compensates the delay time of the magnitude modulated signal by outputting a value corresponding to the input memory address to the amplitude modulator 230.

The PM path delay estimator 330 and the PM delay compensator 340 estimate and compensate the delay time of the phase modulated signal.

The PM path delay estimator 330 is composed of a complex sliding cross-correlator 331 and a phase signal delay estimator 333 to estimate the delay time of the phase modulated signal. The complex sliding cross-correlator 331 receives the complex baseband signal, which is the Cartesian-polar converter input signal of the modulator, and the demodulated complex baseband signal, and cross-correlates through the calculation process of Equation 14 below. -correlation) value (R [m]) is calculated.

은 0보다 큰 임의의 정수이고,

는 상관 윈도우 사이즈(correlation window size)를 의미하며, 상기

는 추정하고자 하는 최대 샘플 단위 지연에 의해서 결정된다.In Equation 14,

Is any integer greater than zero,

Denotes a correlation window size, and

Is determined by the maximum sample unit delay to be estimated.

)을 의미하며, 인덱스는 PM 지연 보상기(340)의 주소 발생기(Address Generator, 341)로 입력된다. The calculated cross-correlation value is input to the phase signal delay estimator 333, and the phase signal delay estimator 333 determines the index with the largest cross-correlation value. The determined index is an estimated phase signal delay time (

The index is input to the address generator 341 of the PM delay compensator 340.

)를 차감하여 생성한다. Then, the address generator 341 generates a 'memory address' for delay compensation based on the input index and transmits it to the memory 343. Where memory address is the index from the current memory address value (Estimate Phase Signal Delay Time =

Create by subtracting).

The memory 343 compensates the delay time of the phase modulated signal by outputting a value corresponding to the finally input memory address to the phase modulator 240.

4 is a block diagram illustrating another embodiment of the PM path delay estimator 330 and the PM delay compensator 340 shown in FIG. 3.

The apparatus shown in FIG. 4 has an advantage of shortening the delay time estimation time when estimating the delay time of the phase modulated signal.

The apparatus illustrated in FIG. 4 performs cross-correlation of symbol units through the symbol-level sliding correlator 410 and the symbol-level delay estimator 420 to estimate and compensate the delay time. The sample-level sliding correlator 440 and the sample-level delay estimator 450 perform cross-correlation on a sample basis to estimate and compensate the delay time in one symbol.

)를 계산한다. 그리고 계산된 메모리 주소는 메모리(460)로 출력된다.This reduces power consumption with faster latency estimation and improved throughput. In this case, the address generator 430 uses the relational expression given by Equation 15 below using the symbol unit delay time estimation result, and thus the memory address (

Calculate The calculated memory address is output to the memory 460.

,

,

각각은 현재의 메모리 주소, 추정된 심볼 단위 지연시간, 심볼당 샘플수를 의미한다.In Equation 15,

,

,

Each represents the current memory address, estimated symbol unit delay time, and samples per symbol.

)를 계산한다.After estimating and compensating the symbol unit delay time, the address generator 430 uses the sample unit delay time estimation result to calculate a memory address (Equation 16) as shown below.

Calculate

는 샘플 단위 지연 시간 추정 결과를 의미한다.In Equation 16,

Denotes a sample unit delay time estimation result.

FIG. 5 is a block diagram illustrating still another embodiment of the delay estimator 223 and the delay compensator 221 shown in FIG. 2.

Both the delay time of the magnitude modulated signal and the delay time of the phase modulated signal can be estimated using a recursive LMS algorithm. However, when estimating both delays simultaneously using the recursive LMS algorithm, there is a possibility that the estimation result may diverge due to the convergence characteristic of the recursive LMS algorithm.

Therefore, the apparatus shown in FIG. 5 uses a cross-correlation PM path delay estimator when estimating a delay time of a phase modulated signal using a recursive LMS delay estimator 531 to reduce the divergence probability. (PM path delay estimator using correlation, 533) is used to estimate the 'initial PM path delay' of the initial phase modulated signal, and to recursively estimate the initial PM path delay of the initial phase modulated signal. (recursive) Used as the initial value of the LMS delay estimator 531. As a result, the possibility of divergence can be reduced.

The delay time of the magnitude modulated signal is obtained by an AM path delay estimator 510 consisting of an amplitude calculator 511 and a recursive LMS delay estimator 513, and an AM delay compensator 520 consisting of an address generator 521 and a memory 523. Is estimated and compensated through. Since the operations of the AM path delay estimator 510 and the AM delay compensator 520 are the same as those of the AM path delay estimator 310 and the AM delay compensator 320 shown in FIG. 3, description thereof will be omitted. .

FIG. 6 is a flowchart illustrating an operation of estimating and compensating a time delay of a phase modulated signal in the apparatus shown in FIG. 4.

As described above, the apparatus shown in FIG. 4 estimates and compensates for the delay time of the phase modulated signal. Delay time estimation and compensation of the phase modulated signal consists of two stages: symbol level and sample level.

For symbol-level delay time estimation and compensation, a cross-correlation window size of symbol-level and sample-level is first set according to the maximum delay time and sampling period that can be estimated (610). The symbol-level cross-correlation is performed by the set symbol-level window size (620). A correlation position having the largest value among the cross-correlation result values is determined as an estimated value of the delay time (630). The memory address is calculated based on the determined estimated value (640), and the symbol-level delay time is compensated by reading a value corresponding to the calculated memory address from the memory (650).

Next, the sample-level cross-correlation is performed by the sample-level window size set in step 610 (660), and the cross-correlation having the largest value among the cross-correlation result values. The cross-correlation position is determined as an estimated value of the sample-level delay time (670). The memory address is calculated based on the estimated value (680), and the sample-level delay time is compensated (690) by reading a value corresponding to the calculated memory address from the memory.

7 is a flowchart illustrating an operation of estimating and compensating for a time delay of a magnitude modulated signal in the apparatus shown in FIGS. 3 and 5.

Delay time estimation of the magnitude modulated signal uses a recursive LMS algorithm.

Referring to FIG. 7, the LMS algorithm is calculated using the magnitude information signal of the Cartesian-polar converter output as a reference signal and the magnitude signal of the demodulated complex baseband signal as a measurement signal (710). The instantaneous delay time of the magnitude modulated signal is updated 720. Next, the memory address is calculated based on the instantaneous delay time (730), and the memory value corresponding to the calculated memory address is read and output (740).

By performing this series of steps repeatedly, the estimated delay time is updated repeatedly, eventually converging to a value close to the delay time of the actual magnitude modulated signal.

FIG. 8 is a flowchart illustrating an operation of estimating and compensating for a time delay of a phase modulated signal in the apparatus shown in FIG. 5.

In order to estimate and compensate for the delay time of the phase modulated signal, a correlation window size is set (810). The cross-correlation is performed by the set window size (820). The correlation position having the largest value among the correlation result values is determined as an estimated value of the initial delay time, and the estimated value is set as an initial estimated value of a recursive LMS algorithm (830).

Since the delay time estimation and compensation processes 840 to 870 of the phase modulated signal using the recursive LMS algorithm are the same as the processes 710 to 740 of FIG. 7, the description thereof will be omitted.

So far I looked at the center of the preferred embodiment for the present invention. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. The disclosed embodiments should, therefore, be considered in an illustrative rather than a restrictive sense. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

1 is a block diagram of a typical polar transmitter;

2 is a block diagram illustrating a polar transmitter according to an embodiment of the present invention;

3 is a block diagram illustrating a specific embodiment of the delay estimator 223 and the delay compensator 221 shown in FIG. 2.

4 is a block diagram illustrating another embodiment of the PM path delay estimator 330 and the PM delay compensator 340 shown in FIG.

FIG. 5 is a block diagram illustrating still another embodiment of the delay estimator 223 and the delay compensator 221 shown in FIG. 2.

FIG. 6 is a flowchart for explaining an operation of estimating and compensating for a time delay of a phase modulated signal in the apparatus shown in FIG. 4;

7 is a flowchart illustrating an operation of estimating and compensating a time delay of a magnitude modulated signal in the apparatus shown in FIGS. 3 and 5;

8 is a flowchart for explaining an operation of estimating and compensating for a time delay of a phase modulated signal in the apparatus shown in FIG. 5;

Claims (1)

In the delay time compensation method of the polar transmitter, Converting the complex baseband signal into a magnitude information signal and a phase information signal; Amplitude modulating the magnitude information signal to generate a magnitude modulated signal, and phase modulating the phase information signal to generate a phase modulated signal; Synthesizing and amplifying the phase modulated signal and the magnitude modulated signal; Generating a complex baseband signal by demodulating and digitally converting a feedback signal from the power amplifier output using the local oscillation signal, Estimating and compensating for the delay time of the phase modulated signal using cross-correlation, Estimating and compensating for the delay time of the magnitude modulated signal using a recursive LMS algorithm Comprising a delay time difference compensation method of the polar transmitter.

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