KR100851565B1 - Dual-dll module for galileo system - Google Patents

Abstract

A dual-DLL(Delay Locked Loop) module for Galileo system is provided to suppress noise by selecting a present synchronous time point of the basis of a signal to noise ratio of a present correlation value. A demodulator(101) demodulates a received signal by multiplying the received signal by a carrier. A diffusion signal generator(102) outputs a diffusion code EE for indicating a time point which is earlier than a time point for indicating diffusion codes E, P, and L and a minimum value of an LSR(Left Side-lobe Region). The diffusion signal generator outputs a diffusion code EL for indicating a time point which is later than the time point for indicating the minimum value. A first correlator(103) diffuses inversely the demodulated signal on the basis of the diffusion code L and outputs a correlation value through a correlation calculation process. A second correlator(104) diffuses inversely the demodulated signal on the basis of the diffusion code P and outputs a correlation value through a correlation calculation process. A third correlator(105) diffuses inversely the demodulated signal on the basis of the diffusion code E and outputs a correlation value through a correlation calculation process. A fourth correlator(106) diffuses inversely the demodulated signal on the basis of the diffusion code EL and outputs a correlation value through a correlation calculation process. A fifth correlator(107) diffuses inversely the demodulated signal on the basis of the diffusion code EE and outputs a correlation value through a correlation calculation process. A decider(108) outputs a present synchronous time point on the basis of a difference between the correlation values. A weighted discriminator(109) outputs a weighted difference between the correlation values by using a slope of the correlation values to the minimum value, as a weighted value. An adder(110) adds the minimum value to the weighted difference. A power calculator(111) produces a power value from an output of the second correlator. A selector(112) selects an output of the adder when the power value is higher than a threshold value or selects an output of the decider when the power value is lower than the threshold value. A loop filter(113) feeds back an output of the selector to the diffusion code generator.

Description

Synchronous tracking module of Galileo system {DUAL-DLL MODULE FOR GALILEO SYSTEM}

1 is an exemplary view showing an autocorrelation function of a direct sequence spread band in which a binary stream is modulated with a carrier wave;

2 is a block diagram of a conventional synchronization tracking module,

3 is an exemplary diagram for describing a function of the discriminator of FIG. 2;

4 is an exemplary diagram illustrating a tracking shift in a channel environment in which a visible signal and a multipath signal are mixed;

5 is an exemplary diagram showing a plurality of correlation functions for a case where a multipath signal is mixed;

6 is a block diagram of a synchronization tracking module according to the present invention;

7 is an exemplary diagram for explaining a threshold value used in the selector according to the present invention.

** Description of symbols for the main parts of the drawing **

100: synchronization tracking module of the present invention

101: demodulator 102: diffusion code generator

103: first correlator 104: second correlator

105: third correlator 106: fourth correlator

107: fifth correlator 108: discriminator

109: weight discriminator 110: summer

111: power calculator 112: selector

113: loop filter

The present invention relates to a code synchronization tracking module and a tracking method of a Galileo system, in particular, in a Galileo system using a Direct Sequence Spread Spectrum (DS / SS) modulated by a binary offset carrier (BOC). The present invention relates to a technique for tracking code synchronization more precisely.

The Galileo System is a satellite navigation system under development by the European Union. Currently widely used satellite navigation system is the US Global Navigation System (GPS). GPS transmits civil positioning signals free of charge all over the world, but there are a number of restrictions in the field of civil service because it is a system that is developed and operated for military purposes. In response, the European Union has begun building a Galileo system, and the Korean government has been involved in the construction project since September 2006.

Frequency bands used in the Galileo system are the E2-L1-E1, E5a / L5, E5b, and E6 bands. Of these, the E2-L1-E1 band overlaps the L1 band of GPS, and the E5a / L5 band overlaps the L5 band of GPS. Both of these overlapping bands are used to transmit civilian positioning signals. In particular, the L1 band of GPS transmits a Coarse / Acquisition (C / A) code used in most satellite navigation systems. Band. In February 2004, the European Union and the United States agreed on the basic signal structure of the Galileo system to reduce interference in these two bands. As a result, the Galileo system can reduce the band interference through additional modulation after the bandpass modulation. Lee Jin-cheon has adopted the carrier modulation technique.

The binary transition carrier modulation technique (BOC) employed in the Galileo system utilizes the same center frequency by remodulating a modulated signal into a pass band and rearranging the signal in a band spaced apart from the center frequency by a predetermined period. Avoid interference with the system (GPS).

는 자기 상관함수를,

는 부호 칩의 주기(이하, 칩 주기)를 의미한다. 최고값만을 특징점으로 갖는 BPSK(Binary Phase Shift Key)의 자기 상관함수와는 달리, 갈릴레이 시스템은 최고값과 극소값을 특징점으로 갖는다. 최고값이 나타나는 시점은 이상적인 채널 환경에서 정확한 동기시점이 된다.A Galileo system using a direct sequence spread band (DS / SS) modulated by a binary carrier (BOC) has an auto-correlation function (ACF) as shown in FIG. 1. In the drawing,

Is the autocorrelation function,

Denotes a cycle of the code chip (hereinafter referred to as a chip cycle). Unlike the autocorrelation function of Binary Phase Shift Key (BPSK), which only features the highest value, the Galilean system has the highest and minimum values. The point at which the peak appears is the exact point of synchronization in the ideal channel environment.

또는 그 이하로 맞추는 단계이 며, '추적단계'는 정확한 동기를 결정하고 유지하는 단계를 말한다. In the Galileo system, accurate code synchronization is required to recover the received signal. Code synchronization is largely divided into acquisition phase and tracking phase. 'Acquisition step' is to synchronize the code of the received signal with the code generated by the receiver.

Or less than that, and the 'tracking' step is to determine and maintain the correct motivation.

As a general synchronization tracking module, 'EL-DLL' (delay lock loop with early minus late discriminator), which is based on the difference between the early correlation value slightly earlier than the current code synchronization point and the late correlation value slightly lowered, is considered. Can be.

2 illustrates the configuration of an EL-DLL. The EL-DLL uses a demodulator (1), a spreading code generator (2), a first correlator (3), a second correlator (4), a third correlator (5), a discriminator (6), and a loop filter (7). Configure.

인 반송파를 곱하여 복조하고, 확산부호 발생기(2)는 현재 동기시점

에 대한 확산부호 P(prompt),

보다 이른 시점을 나타내는 확산부호 E(early) 및

보다 늦은 시점을 나타내는 확산부호 L(late)을 발생한다. Specifically, the demodulator 1 is a received signal Center frequency

Multiply by the carrier, and the spreading code generator 2 is currently synchronized

Spread code P (prompt) for,

Diffusion code E (early) and earlier

The spreading code L (late) indicating a later time point is generated.

을 출력한다. 제2 상관기(4)는 복조된 수신신호에 확산부호 P를 곱하여 역확산하고, 상관연산을 수행하여 상관값

를 출력하며, 제3 상관기(5)는 복조된 수신신호에 확산부호 E를 곱하여 역확산하고, 상관연산을 수행하여 상관값

를 출력한다.The first correlator 3 despreads the demodulated received signal by multiplying the spread code L and performs a correlation operation to perform a correlation operation.

Outputs The second correlator 4 despreads the demodulated received signal by multiplying the spread code P and performs a correlation operation to perform a correlation operation.

The third correlator 5 multiplies the demodulated received signal by the spread code E, despreads, and performs a correlation operation to perform a correlation operation.

Outputs

,

의 차이값에 따라 현재 동기시점

를 증감하여 출력하며, 루프필터기(7)는 판별기로부터 출력되는 현재 동기시점

를 확산부호 발생기(2)로 되먹임한다. The discriminator 6 has a correlation value

,

The current synchronization point according to the difference of

Is output by increasing and decreasing the loop filter (7), and the current synchronization point output from the discriminator

Is fed back into the diffusion code generator (2).

,

,

는 각각 점 E, P, L로 표현되어 있다. [A]의 경우, E와 L의 차이는 양수가 되므로 판별기는 현재 동기시점

가 정확한 동기시점으로부터 이른 시점임을 판별하고 현재 동기시점

를 증가시킨다. [B]의 경우, E와 L의 차이는 양수가 되므로 상기 판별기는 현재 동기시점

가 정확한 동기시점으로부터 늦은 시점임을 판별하고 현재 동기시점

를 감소시킨다. 이러한 일련의 추적 단계는 차이값이 0이 될 때까지 반복된다. 차이값이 0이라는 것은 [C]와 같이 현재 동기시점

가 '정확한 동기시점'이라는 것을 의미한다.Referring to FIG. 3, the function of the discriminator 6 will be described in more detail as follows. Correlation Values in Drawings

,

,

Are represented by points E, P, and L, respectively. For [A], the difference between E and L is positive, so the discriminator is currently synchronized

Determines that is earlier than the exact synchronization point, and

To increase. In case of [B], the difference between E and L is positive, so the discriminator is currently synchronized

Is late from the exact time of synchronization, and the current time of synchronization

Decreases. This series of trace steps is repeated until the difference is zero. A difference of zero means that the current sync point, like [C].

Means 'correct synchronization time'.

The above-described sync tracking module EL-DLL exhibits an optimal function only in a channel environment in which only a line of sight signal (LOS) is received. However, in a channel environment in which the visible signal and the multipath signal are mixed, there is a predetermined tracking shift (see FIG. 4). In FIG. 4, since the difference between E and L becomes 0, the current synchronization time is incorrectly locked to the correct synchronization time. This tracking shift reduces the spreading gain and can cause significant distance error in the Galileo system.

는 가시신호(LOS)와 다중경로 신호의 상대적 수신시간 차이를 의미하며,

=0인 시점이 나타나는 주엽(main-lobe)을 기준으로 좌우에 있는 음영영역은 각각 좌측 부엽 영역(LSR: left side-lobe region)과 우측 부엽 영역(RSR: right side-lobe region)으로 지칭된다. 여기서,

에 따라

=0인 시점을 기준으로 주엽의 대 칭성이 왜곡된다는 것을 알 수 있다. 또한,

는 항상 양의 값의 갖는다. 왜냐하면 가시신호가 다중경로 신호에 비해 언제나 이른 시점에 수신되기 때문이다. 따라서, 좌측 부엽 영역(LSR)의 상관함수에 비해 우측 부엽 영역(RSR)의 상관함수가 다중경로 신호에 의해 왜곡되는 정도가 더 크다는 특징을 보인다.5 is an exemplary view showing a correlation function for a case where a multipath signal is mixed.

Is the difference in the relative reception time of the visible signal (LOS) and the multipath signal,

The shaded regions to the left and right of the main-lobe where the point of time at which = 0 appears are referred to as left side-lobe region (LSR) and right side-lobe region (RSR), respectively. . here,

Depending on the

It can be seen that the symmetry of the main lobe is distorted based on the time point of = 0. Also,

Always has a positive value. This is because the visible signal is always received earlier than the multipath signal. Accordingly, the correlation function of the right side lobe region RSR is more distorted by the multipath signal than the correlation function of the left side lobe region LSR.

The present invention focuses on the fact that the time when the minimum value of the correlation function appears in the left side lobe region (LSR) is relatively small compared to the right side lobe region (RSR), thereby providing a synchronization tracking module that can minimize the tracking shift. do.

Specific features and advantages of the present invention will become more apparent from the following detailed description based on the accompanying drawings. In the meantime, when it is determined that the detailed description of the known functions and configurations related to the present invention may unnecessarily obscure the subject matter of the present invention, it should be noted that the detailed description is omitted.

Figure 6 shows the configuration of a synchronization tracking module according to the present invention. Referring to the drawings, the synchronization tracking module 100 includes a demodulator 101, a spreading code generator 102, a first correlator 103, a second correlator 104, a third correlator 105, and a fourth correlator ( 106, a fifth correlator 107, a discriminator 108, a weight discriminator 109, a summer 110, a power calculator 111, a selector 112, and a loop filter 113.

에 중심주파수

인 반송파를 곱하여 복조한다. 확산부호 발생기(102)는 현재 동기시점

에 대한 '확산부호 P', 현재 동기시점보다 이른 시점을 나타내는 '확산부호 E', 현재 동기시점보다 늦은 시점을 나타내는 '확산부호 L', 좌측 부엽 영역(LSR)의 극소값

이 나타나는 시점보다 이른 시점을 나타내는 '확산부호 EE', 그리고 상기 극소값

이 나타나는 시점보다 늦은 시점을 나타내는 '확산부호 EL'을 출력한다. 이와 같은 본 발명의 확산부호 발생기(102)는 극소값의 시점을 기점으로 확산부호 EE(early-early)와 확산부호 EL(early-late)를 더 부가한다는 점에서 앞서 살펴본 도 2의 확산부호 발생기(2)와 대비된다.The demodulator 101, like the conventional EL-DLL, receives the received signal.

Center frequency

Multiply by the carrier to demodulate. The spreading code generator 102 is currently synchronized

'Spreading code P' for 'spreading code E' indicating earlier than the current synchronization point, 'spreading code L' indicating later than the current synchronization point, and the minimum value of the left side lobe region (LSR)

The spreading code EE, which indicates a time earlier than the time point at which the symbol appears, and the minimum value

Outputs a 'spread code EL' indicating a point in time later than the point in time. As described above, the diffusion code generator 102 of the present invention further adds the diffusion code EE (early-early) and the diffusion code EL (early-late) to the starting point of the minimum value. Contrast with 2).

을 출력한다. 제2 상관기(104)는 복조된 수신신호에 확산부호 P를 곱하여 역확산하고, 상관연산을 통해 상관값

를 출력하며, 제3 상관기(105)는 복조된 수신신호에 확산부호 E를 곱하여 역확산한 후, 상관연산을 수행하여 상관값

를 출력한다. 한편, 제4 상관기(106)는 복조된 수신신호에 확산부호 EL을 곱하여 역확산과 상관연산을 통해 상관값

을 출력하고, 제5 상관기(107)는 복조된 수신신호에 확산부호 EE를 곱하여 역확산 및 상관연산을 하여 상관값

를 출력한다.The first correlator 103 despreads the demodulated received signal by multiplying the spreading code L and then performs a correlation operation to perform a correlation operation.

Outputs The second correlator 104 despreads the demodulated received signal by multiplying the spread code P, and correlates the correlation value through a correlation operation.

The third correlator 105 multiplies the demodulated received signal by the spread code E, despreads, and then performs a correlation operation to perform a correlation operation.

Outputs On the other hand, the fourth correlator 106 multiplies the demodulated received signal by the spreading code EL and correlates the correlation value through despreading and correlation operation.

The fifth correlator 107 multiplies the demodulated received signal by the spreading code EE to despread and correlate the correlation value.

Outputs

와

의 차이값을 기초로 하여 현재 동기시점

를 증감한

를 출력하되, 차이값이 0일 경우 현재 동기시점

를 정확한 동기시점 으로 판단하여 고정(locking)한다.The discriminator 108 has a correlation value

Wow

Current synchronization point based on the difference of

Increased or decreased

If the difference is 0, the current sync point

Lock to determine the correct synchronization time.

와

의 차이값을 출력하되, 좌측 부엽 영역(LSR)의 극소값

에 대한

와

의 기울기를 가중치로 하여 출력한다. 이는 아래의 수학식으로 표현된다.On the other hand, the weight discriminator 109 is a correlation value

Wow

Outputs the difference of, but minimizes the left side lobe region (LSR)

For

Wow

The slope of is output as the weight. This is expressed by the following equation.

....................... [수학식]

....................... [ mathematical formula ]

는 가중 차이값,

는 상관값

와 극소값

에 의한 기울기,

은 상관값

과 극소값

에 의한 기울기를 의미한다. 본 발명에서 기울기를 가중치로 적용하는 이유는, 도 5에서 보인바와 같이 좌측 부엽 영역(LSR)의 상관함수는 극소값을 기점으로 좌우 비대칭이기 때문이다. 따라서 본 발명의 가중판별기(109)는 상기한 판별기(108)와 달리 이러한 좌측 부엽 영역(LSR) 상관함수의 비대칭 특성을 차이값(가중 차이값) 계산에 고려한다. here,

Is the weighted difference,

Is a correlation value

And local minimum

Slope by,

Is a correlation value

And local minimum

Means the slope by. The reason why the slope is applied as the weight in the present invention is that, as shown in FIG. 5, the correlation function of the left side lobe region LSR is left and right asymmetrical starting from the minimum value. Therefore, the weight discriminator 109 of the present invention, unlike the discriminator 108 described above, considers the asymmetry characteristic of the left side lobe region (LSR) correlation function in calculating the difference value (weighted difference value).

를 합산한 값

를 출력하며, 전력계산기(111)는 제2 상관기(104)를 통해 출력되는 현재 상관값

을 바탕으로 전력치를 산출한다.Summer 110 is a minimum value to the weighted difference value output from the weight discriminator 109

Sum of

The power calculator 111 outputs a current correlation value output through the second correlator 104.

Based on this, the power value is calculated.

의 오차 증대로 이어지기 때문에, 본 발명의 특징적인 양상에 따라 선택기(112)는 상기 전력치가 임계값보다 높은 경우

를 출력하고, 낮은 경우

를 선택·출력한다. If the signal-to-noise ratio (SNR) is large, the input of the weight discriminator 109 is greatly distorted.

According to a characteristic aspect of the present invention, the selector 112 causes the power value to be higher than a threshold value.

Output, and if low

Select and output

를 출력하고, 그렇지 않은 경우

를 출력하게 되는 것이다.Here, the correlation function of the general Galileo system is represented as a power function as shown in FIG. In the drawing, the 'maximum value' and the 'maximum value' representing peaks coincide with the viewpoints of the 'minimum value' and the 'maximum value'. In this case, the difference between the maximum value and the maximum value is 6 dB when using a spreading code having a processing gain of 30 dB (the processing gain of the spreading code used in the L1 band in the GPS and Galileo systems is 30 dB). Therefore, the square root of the highest and other values, or the signal-to-noise ratio, is calculated and this value exceeds 6 dB (threshold).

If not, then

Will be printed.

The loop filter 113 feeds back the spreading code generator 102 using the value output from the selector 112 as the current synchronization point.

According to the present invention described above, the tracking shift can be reduced compared to the conventional EL-DLL, and more accurate sign synchronization tracking is possible. In addition, since the current synchronization time is selected based on the signal-to-noise ratio of the current correlation value, it is robust to noise.

As described above and described with reference to a preferred embodiment for illustrating the technical idea of the present invention, the present invention is not limited to the configuration and operation as shown and described as described above, it is a deviation from the scope of the technical idea It will be understood by those skilled in the art that many modifications and variations can be made to the invention without departing from the scope of the invention. Accordingly, all such suitable changes and modifications and equivalents should be considered to be within the scope of the present invention.

Claims (3)

A demodulator for demodulating the received signal by multiplying a carrier wave; A spreading code generator for outputting a spreading code EE representing a time point earlier than a time point at which the minimum values of the spreading codes E, P, L and the left side lobe region appear, and a diffusion code EL at a time later than the time point at which the minimum value appears; After despreading the demodulated received signal based on the spreading code L, a correlation value is obtained through correlation calculation.

A first correlator for outputting a; Despreading the demodulated received signal based on the spreading code P, and then correlating the correlation value

A second correlator for outputting a; After despreading the demodulated received signal based on the spreading code E, a correlation value is obtained through a correlation operation.

A third correlator for outputting; Despreading the demodulated received signal based on the spreading code EL, and then correlating the correlation value

A fourth correlator for outputting a; After despreading the demodulated received signal based on the spreading code EE, a correlation value is obtained through a correlation operation.

A fifth correlator for outputting; The correlation value

Wow

A discriminator configured to increase or decrease the current synchronization time point based on the difference value of? Correlation value for the local minimum

Wow

The correlation value by weighting the slope of

Wow

A weighted discriminator for outputting a weighted difference value of; A summer for adding the minimum value to the weighted difference and outputting the sum; A power calculator for calculating a power value from an output of the second correlator; A selector for selecting an output of the summer when the power value is higher than a threshold and selecting an output of the discriminator when the power value is low; And A loop filter feeding the output of the selector back to the spreading code generator; Synchronous tracking module of the Galileo system comprising a. The method according to claim 1, The threshold value is 6dB synchronization tracking module of the Galileo system. The method according to claim 1, The weighted difference value,

Calculated as here,

Is the weighted difference,

Is a correlation value

And the slope by the local minimum,

Is a correlation value

Synchronous tracking module of the Galileo system, characterized in that the slope by the minimum value.

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