KR20090107052A - Phase correction device - Google Patents

Abstract

The present invention relates to a phase correction device (12) for a signal which has a plurality of signal components which are each modulated onto a carrier signal, said signal having been sampled before transmission in a transmitting apparatus at a transmission sampling clock rate which has a transmission sampling clock duration, and having been sampled after reception in a receiving apparatus with a reception sampling clock rate which has a reception sampling clock duration, with each carrier signal having an associated carrier frequency. In order to carry out phase correction particularly efficiently, the phase correction device (12) is designed to in each case vary, by an associated phase angle, the phases of the signal components as a function of the ratio of the transmission sampling clock duration to the reception sampling clock duration.

Description

Phase correction device {PHASE CORRECTION DEVICE}

The invention comprises a phase correction device according to the preamble of claim 1, in particular a phase correction device for an OFDM transmission system, a phase correction method according to the preamble of claim 6, and a phase correction device according to the preamble of claim 10. To a receiver.

Such a phase correction device is known from DE 103 24 418 and has a plurality of signal components modulated into one carrier signal each with a corresponding carrier frequency and from the transmitter to the transmit sampling clock having a transmit sampling clock duration prior to transmission. It is designed for a signal that is sampled and sampled with a receive sampling clock with a receive sampling clock duration at the receiver after reception. The phase correction device is assembled in the receiver. The signal has signal sections that repeat periodically. The phase error detection device incorporated in the receiver detects the phase error for each signal component based on periodically repeating signal sections resulting from the difference between the transmit sampling clock duration and the receive sampling clock duration. The phase error is corrected for the individual signal components by using an interpolation formula by the phase correction device.

A disadvantage of this method is that it requires a large computational cost for the implementation of interpolation.

It is an object of the present invention to provide a phase correction device, a receiver including the phase correction device, and a phase compensation method capable of performing phase correction particularly efficiently.

The object of the invention is achieved by a phase correction device having the features of the features of claim 1, a phase correction method having the features of the features of claim 6, and a receiver having the features of the features of claim 10.

The present invention relates to a phase correction apparatus designed to change the phase of signal components by one corresponding phase value, respectively, in accordance with the ratio of the transmission sampling clock duration to the reception sampling clock duration.

Preferably such a phase correction device does not have high memory requirements and computational costs.

In a preferred embodiment, the phase correction device is designed to change the phase value of the signal components in accordance with the corresponding carrier frequency.

In this way, very accurate correction is preferably achieved.

와의 승산에 의해 복소수 표기 방식으로 주어지고, 상기 식에서, δ는 송신 샘플링 클록 지속 시간 대 수신 샘플링 클록 지속 시간의 비이고, k는 자연수이고, nω_s는 송신기의 기본 주파수ω_s의 정수배인 캐리어 주파수이고, T_U는 송신기 샘플링 클록 지속 시간이다.In another preferred embodiment, the change in one of the phases is a correction factor

Multiplied by and given in complex notation, where δ is the ratio of the transmission sampling clock duration to the reception sampling clock duration, k is a natural number, and nω _s is an integer multiple of the transmitter's fundamental frequency ω _s And T _U is the transmitter sampling clock duration.

In a preferred embodiment the phase correction device is designed to convert the signal components into difference phases ΔΦ respectively and change the difference phases ΔΦ respectively by the addition of one phase value.

Preferably such a phase correction device can be implemented in an OFDM system using 4-DQPSK, especially at low cost.

In another preferred embodiment, the phase correction device is designed to change the phases of adjacent signal components by one and the same phase value.

This advantageously further reduces memory demand and computational costs.

The present invention relates to a phase correction method for a signal, wherein the phases of the signal components are each changed by one corresponding phase value in accordance with the ratio of the transmission sampling clock duration to the reception sampling clock duration.

In a preferred embodiment, the change of the phase values of the signal components is carried out according to the corresponding carrier frequency.

In a preferred embodiment, the signal components are converted into differential phases and the differential phases are each altered by the addition of one phase value.

In another embodiment of the present invention, the phases of adjacent signal components are changed by one equal magnitude phase value.

The invention also relates to a receiver having a phase correction device designed to change the phase of the signal components by one corresponding phase value, respectively, in accordance with the ratio of the transmission sampling clock duration to the reception sampling duration.

The invention is explained in more detail below in connection with the drawings.

1 is a schematic diagram of a transmitter,

2 is a schematic diagram of a receiver,

3 is a phase diagram showing a quadrature component Q and an inphse component I of the difference phases,

4 is a phase diagram showing the quadrature component Q and the inphse component I of the difference phases.

1 shows a schematic diagram of a transmitter of an OFDM transmission system based on 4-DQPSK. The bit sequence to be transmitted {b _k } with a number of sequence sections {b _k } (k = 0, 1, 2, 3 ...) of duration T _U is decoded by the demultiplexer 1 into N subchannels. (n = 0, 1, 2 ... N-1), divided into parallel data streams b _{i , n} (n = 0, 1, 2, ... N-1). The parallel data streams are coded in a differential manner by the differential coder 2, resulting in complex transmit symbols d _k (n) that correspond to the difference phases and are called signal components below. Signal components d _k (n) are modulated by carrier signals with carrier signals having different carrier frequencies ω = n · ω _s (n = 0, 1, 2, 3 ... N-1) by modulators 3 do. The modulation corresponds to a multiplication with the factors exp (jnω _n t). The signal components each modulated with the carrier signal are added by the adder 4 to form an adder signal. In the output device 5 the protection duration T _G is added to the addition signal and the addition signal is sampled with the transmitter sampling clock with the duration t _U = 2π / N · ω _s = T _U / N, and the OFDM-transmission signal It is transmitted through the transmit antenna 6 as m (t). The duration T = T _U + T _G of the OFDM-transmitted signal m (t).

2 shows a schematic diagram of a receiver. The receiving antenna 7 receives the same OFDM-received signal u (t) as the OFDM-transmitted signal m (t) except for interference. In the input device 8, the signal u (t) is sampled with the receiver sampling clock of time t _U '= 2π / N · ω _s ' = T _U ' / N, and then the protection duration T _G is separated, Is preferably T _U '= T _U and ω _s ' = ω _s . In the demultiplexer 9 the signal is divided into N subchannels and parallel data streams. Parallel data streams are demodulated at frequency ω _n '= n · ω _s ' in demodulator 10. The demodulation corresponds to a multiplication with the factors exp (−jnω _n 't), and the signals U _k (n) appearing after the demodulation again correspond to the difference phase.

Because the receiver can be considered a correlated receiver (see Christian Hansen, "Synchronisationsverfahren fuer OFDM-basierte Rundfunksysteme", PhD Thesis, University of Hannover, page 12, 2004). The signals are as follows:

Ignoring the interference, the OFDM-received signal u (t) is equal to the OFDM-transmitted signal m (t) and is as follows (see Figure 1):

 Substituting equation (2) into equation (1) gives:

및 유효 성분들

로 구분된다:(3) is the interference components

And active ingredients

Are divided into:

은 m이 n 인 모든 가산 성분들을 포함하며 캐리어간 간섭(ICI)을 야기하고, 샘플링 클록의 부정확도가 낮으면 간섭 성분들이 매우 미미하게 나타나기 때문에 하기에서 무시된다. 적분하면 하기와 같다:Interference components

Is ignored below because it contains all the additive components m is n and causes inter-carrier interference (ICI), and if the sampling clock's inaccuracy is low, the interference components appear very insignificant. Integrating is as follows:

이 하나의 위상 값에 상응하는 보정 팩터 f(n)와의 승산에 의해 보정될 수 있는 위상 변이가 실시되는 동안 댐핑 작용을 한다:In the above formula, si (πn (δ-1)) = sin (πn (δ-1)) / πn (δ-1), and the sampling ratio is δ = t _U '/ t _U = T _U ' / T _U , Preferably it is 1. Factor si (πn (δ-1)) is the term

A damping action is performed during the phase shift, which can be corrected by multiplication with a correction factor f (n) corresponding to this one phase value:

The phase value consists of two correction phase components ε ₁ and ε ₂ :

In the above equation, the first term depends on the parameter k, while the second term does not depend on the parameter k.

δ is calculated at input device 8 from T _U 'and T _U and passed to phase correction device 12, in which case T _U is determined from periodically repeating signal sections, as shown in DE 103 24 418. do.

3 is a phase diagram showing quadrature components Q and in-phase components I of the difference phases between two consecutive U _k (n) in a 4-DQPSK-transmission system that is not phase corrected.

4 is a phase diagram showing quadrature component Q and in-phase components I of the difference phases for a 4-DQPSK-transmission system being phase corrected. The difference phases shown as circles are slightly displaced from the ideal position by the noise, compared to the difference phases of FIG.

Since the correction of the signal components is made very simply right after the differential decoding at the decoder 11, in which the difference phases ΔΦ (n, n + 1) are formed into successive bit sequences, the phase correction is performed by the phase correction device 12. Can be carried out by addition.

For the difference phase, a difference phase value is given, consisting of Δε ₁ and Δε ₂ :

The difference phase correction components Δε ₁ and Δε ₂ are added to become the difference phase ΔΦ (n, n + 1).

As an example, a modification with an accuracy of 200 ppm is used and the OFDM-system according to the parameters of the DAB-system (ETSI EN 300 401) with T = 1.25 ms, ω _s = 1 kHz and 1536 active channels is the basis. Thus:

이고, 즉, △ε₁=0.00025, 즉, 600번째 채널에 대해 약 8.6도의 위상 에러를 가지고, 위상 에러 △ε₂=0.00063, 즉 0.036도의 위상 에러를 가진다.

That is, Δε ₁ = 0.00025, that is, a phase error of about 8.6 degrees for the 600th channel, and phase error Δε ₂ = 0.00063, that is, a phase error of 0.036 degrees.

As an alternative to accurate correction for all phase errors, correction by the same phase for multiple adjacent channels can be performed, thereby reducing memory demands and computational costs. To this end, for the x-th channel, the correct calibration value is calculated, which is used for both (x-1) / 2 adjacent channels. When x = 5, when k = 600, it is (DELTA) epsilon ₁ = 0.00025 * 600 = 0.15, and when k = 602, it is (DELTA) epsilon ₁ = 0.00025 * 602 = 0.1505. This corresponds to an error of 0.028 degrees and can be ignored.

After phase error correction, the corrected signals B _{k , n} are multiplexed in the multiplexer 13 to become a bit sequence having a plurality of sequence sections b _k .

Claims (10)

A plurality of signal components d _k (n) modulated into one carrier signal each with a corresponding carrier frequency n · ω _s , and having a transmit sampling clock duration t _U at the transmitter prior to transmission. A phase correction apparatus for a signal sampled with a transmission sampling clock and sampled with a reception sampling clock having a reception sampling clock duration (t _U ') at a receiver after reception, The phase correcting apparatus sets the phases of the signal components d _k (n) by one corresponding phase value according to the ratio of the transmission sampling clock duration t _U to the reception sampling clock duration t _U '. Phase correction device characterized in that it is designed to change each. The method of claim 1, And the phase correction device is designed to change phase values of signal components according to the corresponding carrier frequencies (n · ω _s ). The method according to claim 1 or 2, Change in one of the phases is a correction factor

Multiplied by and given in complex notation, where δ is the ratio of the transmission sampling clock duration t _U to the reception sampling clock duration t _U ', k is a natural number, and nω _s is the And a carrier frequency that is an integer multiple of the fundamental frequency ω _s and T _U is a transmitter sampling clock duration. The method of claim 1, And said phase correction device is designed to convert signal components into difference phases, respectively, and said difference phases, respectively, are changed by addition of one phase value. The method according to any one of claims 1 to 4, Said phase correction device being designed to change the phases of adjacent signal components d _k (n) by one equal magnitude value. A plurality of signal components d _k (n) modulated into one carrier signal each with a corresponding carrier frequency n · ω _s , and having a transmit sampling clock duration t _U at the transmitter prior to transmission. A phase correction method for a signal sampled with a transmission sampling clock and sampled with a reception sampling clock having a reception sampling clock duration (t _U ') at a receiver after reception, And the phases of the signal components are each changed by one corresponding phase value in accordance with the ratio of the transmit sampling clock duration to the received sampling clock duration (t _U '). The method of claim 6, Wherein the change of the phase values of the signal components is carried out in accordance with the corresponding carrier frequencies n · ω _s . The method of claim 6, The signal components are respectively converted into difference phases (ΔΦ), and the difference phases (ΔΦ) are respectively changed by addition of one phase value. The method according to any one of claims 6 to 8, And wherein phases of adjacent signal components (d _k (n)) are changed by one equal magnitude phase value. A plurality of signal components d _k (n) modulated into one carrier signal each having a corresponding carrier frequency n · ω _s , and having a transmit sampling clock duration t _U at the transmitter prior to transmission. A receiver comprising a phase correction device for a signal sampled with a transmit sampling clock and sampled with a receive sampling clock having a receive sampling clock duration (t _U ') at the receiver after reception. The phase correcting apparatus sets the phases of the signal components d _k (n) by one corresponding phase value according to the ratio of the transmission sampling clock duration t _U to the reception sampling clock duration t _U '. A receiver comprising a phase correction device, characterized in that it is designed to alter each.

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