KR101274555B1 - Method of rake finger adjustment and rake finger adjusting device - Google Patents

Abstract

PURPOSE: A rake finger control method and a rake finger control device thereof are provided to detect a target in which performance is smaller than an existing distance error. CONSTITUTION: An interface unit(40) receives the input information of a system operator. A Doppler filter bank unit(50) calculates a time delay based on a relationship between a first signal provided through a descrambling unit or a de-spreading unit according to a set value and a second signal provided through the interface unit. A channel estimation module calculates a channel parameter for controlling a rake finger module based on information provided through the Doppler filer bank unit. The channel estimation module provides the calculated channel parameter to a path searching unit. [Reference numerals] (100) Finger control module; (20) Path searching unit; (30) Descrambling/despreading unit; (40) Interface unit; (50) Doppler filter bank unit; (AA) Reference signal and echo signal; (BB) Rake finger; (CC) Critical level test unit; (DD) Channel correction module; (EE) Maximum ratio combiner; (FF) Channel compensation unit; (GG,HH) Demapper; (II) Target detection determination; (JJ) Rake output

Description

Rake finger adjustment method and rake finger adjustment device {METHOD OF RAKE FINGER ADJUSTMENT AND RAKE FINGER ADJUSTING DEVICE}

The present invention relates to a rake finger adjustment method and a rake finger adjustment apparatus, and more particularly, in the CDMA rake-based cellular network radar receiver by introducing an extra finger in addition to the default finger to assign a time corresponding to the detected target distance resolution performance And a rake finger adjustment method and a rake finger adjustment device capable of simultaneously implementing a signal processing load reduction load.

 In a conventional code division multiple access (CDMA) communication scheme, a multipath signal and a target signal are received by a plurality of rake fingers set as defaults in a rake-based multiple split radar receiver. According to the CDMA principle, the rake finger must have a time difference of at least 1/2 depending on the chip duration so that there is no correlation between channels. However, this is a cause of distance error in cell phone radar applications. When the target reflection signal in the continuous time domain is received at discrete time intervals, the target position can be accurately estimated only when the time allocated to the finger and the time difference according to the target position coincide. In other cases, a distance error occurs because it is necessary to assume that the position of the target must remain on the previous finger.

An object of the present invention is to provide a rake finger adjustment method and a rake finger adjustment device that can reduce the distance error due to the movement of the target.

Another object of the present invention is to provide a rake finger adjustment method and a rake finger adjustment device capable of performing target detection with a performance smaller than a conventional distance error even with fewer fingers than the default number of fingers.

The rake finger adjustment method and the rake finger adjustment device according to the present invention for achieving the above object is to activate the extra finger not activated to allocate to the detected target and to reduce the distance error by varying the finger time according to the target movement. It features.

Detailed features of the Rake finger adjustment method according to the present invention comprises the steps of (a) setting the maximum number of fingers (finger) for synchronization, the maximum number of fingers assignable to a single target, the maximum number of targets to be detected; (b) assigning time only to the primary finger and initializing the remaining fingers; (c) determining if the target is detected by the last finger when the target appears; (d) upon detecting a target on the last finger, activating any finger #m and assigning a time value of the last finger; (e) determining if it is a time shift for k fingers; (f) calculating the time delay of the correlator having the largest time relationship from the time information calculated by the correlation process of the Doppler Finger Bank (DFB); (g) moving the finger by applying the calculated time delay to assigning a time value corresponding to the position of the target to the value of the finger #m; (h) determining whether the finger #m reaches the last finger.

Another detailed feature of the rake finger adjustment method according to the present invention is that steps (e) to (h) are repeated until the finger #m reaches the last finger.

In the case where target 1 is present in the presence of target 1, the method of the present invention allocates the # n-th Rake finger, spatially separates the distance by more than a distance between targets, and tracks target 2. .

Another detailed feature of the rake finger adjustment method according to the present invention is that the total number of fingers is calculated by the following equation.

Xa = Xb + Xs + Xm X Xt... ... ... ... ... ... (Equation)

Where Xa is the total number of fingers, Xb is the default number of fingers set for the maximum detection distance, Xs is the maximum number of fingers for synchronization, Xm is the maximum number of fingers assignable to a single target, and Xt is the maximum number of targets to be detected. Indicates the number

Another detailed feature of the Rake finger adjustment method according to the present invention is that when one recognizes that the target has emerged from any of the fingers, one of the inactive fingers is selected to allocate the time of the target signal.

Rake finger adjustment apparatus according to the present invention includes a path search unit for searching a path using the information received from the rake finger modules; A descrambling / despreading unit which generates original data from the signal provided from the path searching unit; An interface unit for receiving input information of a system operator; A Doppler filter bank unit for calculating a time delay of a correlator having the largest time correlation with a signal provided through the descrambling / despreading unit according to a setting value provided through the interface unit; And a channel estimating module for calculating a channel parameter for adjusting the Rake finger module based on the information provided through the Doppler filter bank unit and providing the channel parameter to the path search unit.

Detailed features of the Rake finger adjustment device according to the present invention is that the channel parameters calculated by the channel estimation module is a logical time (coherence time), logical frequency (coherent frequency), amplitude attenuation, phase rotation (phase rotation) It includes a point.

Another detailed feature of the Rake finger adjustment apparatus according to the present invention is that the channel estimation module calculates a finger time such that a time difference greater than at least ½ occurs in a chip period of a spreading code for spreading communication message bands.

The rake finger adjustment method and the rake finger adjustment device according to the present invention has the following effects.

First, the distance error of the CDMA Rake receiver-based multiple split radar receiver can be reduced.

Second, when the two targets are separated by a distance greater than the distance resolution, it is possible to detect multiple targets according to the number of extra fingers.

Third, detection performance can be improved through time multiplexing.

Fourth, since the target detection is possible with fewer fingers and the same performance is obtained in the distance resolution, the load due to signal processing can be reduced.

1 is a block diagram schematically showing the configuration of a rake finger adjustment device according to the present invention.
2 is a flow chart showing the progress of the rake finger adjustment method according to the present invention.
3 is an exemplary diagram of a target detection situation.
4 is an exemplary view illustrating the concept of a rake finger.

Hereinafter, with reference to the accompanying drawings will be described in detail the rake finger adjustment method according to the present invention.

1 is a block diagram schematically showing the configuration of a rake finger adjustment device according to the present invention. Looking at the configuration, the path search unit 20 for searching the path by using the information received from the Rake finger module 10, the descrambling / D to generate the original data from the signal provided from the path search unit 20 Spreading unit 30; An interface unit 40 for receiving input information of a system operator; A Doppler filter bank unit for calculating a time delay of a correlator having the largest time correlation to a signal provided through the descrambling / despreading unit 30 according to a setting value provided through the interface unit 40 ( 50); A channel estimation module 60 for calculating a channel parameter for adjusting the Rake finger module 10 based on the information provided through the Doppler filter bank unit 50 and providing the calculated path parameter to the path search unit 20. It is done by

Basically, the time allocation of CDMA Rake fingers is done in software. The channel estimation module 60 calculates channel parameters such as coherence time, logical frequency coherence frequency, amplitude attenuation, phase rotation, etc. The finger time is calculated and assigned to each finger so that a time difference of at least 1/2 or more occurs in the chip period of the spreading code. This process is a simple calculation and can be handled in software. Therefore, it is possible to freely add extra fingers and adjust the time interval between fingers without hardware modification of the rake finger module. Based on this fact, a finger adjustment module 100 for reducing time error is added by assigning an extra finger to the detected target for the radar receiver application and adjusting the time of the assigned finger according to the movement. Basically, the finger adjustment module uses the system operator's input value, channel status information, and target detection information. Therefore, the input value is set through the demapper and received feedback from the channel estimation module 60 and the Doppler filter bank unit 50. Based on the information fed back from the channel estimation module 60 and the Doppler filter bank unit 50, various parameters for finger adjustment are calculated and used as input values of the path search unit 20.

2 is a flow chart showing the progress of the rake finger adjustment method according to the present invention.

(a) setting the maximum number of fingers for synchronization, the maximum number of fingers assignable to a single target, and the maximum number of targets to be detected (S201)

(b) assigning time only to the primary finger and initializing the remaining fingers (S202);

(c) determining whether the target is detected by the last finger when the target appears (S203);

(d) when detecting a target on the last finger, activating an arbitrary finger (#m) and assigning a time value of the last finger (S204);

(e) determining whether it is a time shift for k fingers (S205);

(f) calculating time delays of the correlator having the largest time relationship from the time information calculated by the correlation process of the Doppler Finger Bank (DFB) (S205-S208);

(g) moving the finger by applying the calculated time delay to assign a time value corresponding to the position of the target to the value of the finger #m (S207);

(h) determining whether the finger #m reaches the last finger (S208).

Steps S205 to S208 are repeated until the finger #m reaches the last finger.

Assume a simple radar situation as shown in FIG. 3 for easy understanding of the invention. The maximum detection distance and finger-to-finger distance that a rake-based radar receiver (Rx) with conventional five fingers can achieve under system requirements with a 70% detection probability (P _d ) and a false alarm probability (P _fa ) of 10 ^-3 . Depicts the detection distance. 3 shows the actual placement of the five rake fingers and the detection distance corresponding to the allocated time.

For example, since the target 1 exists outside the maximum detection distance at the time t1, the detection is not detected, but since the reflection signal is received at the finger # 5 at the time t2, the receiver recognizes the target and calculates the target distance. If target 1 moves to time t10, the target will be detected at the # 4 or # 3 finger. In this process, since the fingers are fixedly spaced at regular intervals, the distance of target 1 will be the distance value corresponding to the time of fingers # 5-> # 4-> # 3 while moving from time t2 to time t10. This is a distance error that occurs because the time interval between fingers cannot be changed flexibly. This problem can be solved by assigning an extra finger for target tracking and variably adjusting the finger time.

Referring to FIG. 2, the rake finger adjustment method according to the present invention will be described in more detail. First, in step S201, the system operator may perform the maximum number of fingers (Xs) for synchronization as a system requirement, for a single target. The maximum number of assignable fingers (Xm) and the maximum number of targets (Xt) to be detected are set in the demapper module of FIG. 1. Therefore, if the number of basic fingers set for the maximum detection distance is Xb, the total number of fingers Xa becomes Xb + Xs + Xm * Xt.

Referring to FIG. 4, the concept of finger time allocation according to a target may be understood. In this embodiment, Xb = 5, Xm = 1, and Xt = 2 are set. The basic fingers # 1 to # 5 are allocated at fixed equal intervals in accordance with the original maximum detection distance, and time is variably assigned to the remaining fingers. When the required total number of fingers is calculated, a finger tap is generated according to the value, and accordingly, the redundant functions of the module of FIG. 1 and the module 50 of FIG. 1 are activated. Since no detection decision occurs before the target appears, in step S202, time is assigned only to the basic finger, and the remaining fingers (#l to #n) are initialized to t _{# all} = 0. The system is performing a detection algorithm in real time, and when target 1 emerges, target detection occurs first at finger # 5 (last) (S203). In this case, since the target exists at a distance corresponding to the time of the # 5 finger most, the #m finger is activated for the tracking of the target 1 in which the user wanders and assigns the time value of the # 5 finger (S204). If one detection processing cycle passes and detection is performed at the next time point, target 1 is not exactly at # 5 because target 1 has moved a certain distance. However, from the time information calculated by the correlation process of the Doppler filter bank DFB, the time delay of the correlator having the largest time correlation can be known (S205-S208). We call this time t _ij , which represents the time delay of the j th time correlator on the i th finger. This indicates that the time corresponding to the j th correlator plus the time corresponding to the i th finger is the time corresponding to the position of the final target. Assign this to the value of the #m finger. In this way, the finger moves by tracking the position of the target by continuously assigning the value of the #m finger to a time value corresponding to the position of the target in the same processing cycle as well. When target 1 approaches the receiver, the #m finger moves toward # 1 and again toward # 5 when it moves away. If it reaches farther away and #m reaches # 5, the target assumes that it is outside the maximum detection distance of the receiver and the finger time allocation process ends.

The present invention not only solves the above problem but also has three additional advantages. First, target 2 can be tracked by assigning the # n-th Rake finger in the same manner when target 2 is in the presence of target 1. However, it is possible to be separated spatially by a distance equal to or greater than the distance resolution between targets. Using this, the maximum number of target detections depends on the m _t value. Another advantage is improved detection performance due to time multiplexing. The signal reflected by the target is input to have a delay spread at the receiving end. This allows the same target signal to be detected in multiple fingers when the spacing between rake fingers is set narrow. In this case, the amount of reflected signal energy received can be increased to take time multiplexing gain. Therefore, the detection performance can be improved. Finally, the same performance can be achieved with fewer default fingers. For example, assume that two default fingers are assigned to # 0 and # 5, respectively, in FIG. At this time, since there is no finger in the middle, a signal corresponding to the distance cannot be received. According to the rake finger adjusting method and the rake finger adjusting apparatus according to the present invention, when the target signal is detected at # 5, the target signal is recognized and the extra finger is activated by selecting one of the inactive fingers and assigning the time of the target signal. will be. In this way, one finger is assigned to one target to continuously track the time for the target, and thus the target detection is possible without receiving the target signal from the intermediate default finger.

Claims (8)

(a) setting maximum number of fingers for synchronization, maximum number of fingers assignable to a single target, and maximum number of targets to be detected;
(b) assigning time only to the primary finger and initializing the remaining fingers;
(c) determining if the target is detected by the last finger when the target appears;
(d) upon detecting a target on the last finger, activating any finger #m and assigning a time value of the last finger;
(e) determining if it is a time shift for k fingers;
(f) calculating the time delay of the correlator having the largest time relationship from the time information calculated by the correlation process of the Doppler Finger Bank (DFB);
(g) moving the finger by applying the calculated time delay to assigning a time value corresponding to the position of the target to the value of the finger #m;
and (h) determining whether the finger (#m) reaches the last finger. In the case where target 1 is present in the presence of target 1, the method of claim 1 assigns the # n-th Rake finger, spatially separates the distance by more than the distance between targets, and tracks target 2. Rake finger adjustment method. The method of claim 1,
The total number of fingers is a rake finger adjustment method, characterized in that calculated by the following formula.
Xa = Xb + Xs + Xm X Xt... ... ... ... ... ... (Equation)
Here, Xa is the total number of fingers, Xb is the number of basic fingers set for the maximum detection distance, Xs is the maximum number of fingers for synchronization, Xm is the maximum number of fingers assignable to a single target, Xt is the target of the target to be detected The maximum number. The method of claim 1,
And recognizing that the target has emerged from the finger, and selecting one of the inactive fingers to allocate the time of the target signal. The method of claim 1,
And repeating steps (e) to (h) until the finger (#m) reaches the last finger. A path searcher searching for a path using information received from the Rake finger modules;
A descrambling / despreading unit which generates original data from the signal provided from the path searching unit;
An interface unit for receiving input information of a system operator;
A Doppler filter bank unit for calculating a time delay of a correlator having the largest time correlation with a signal provided through the descrambling / despreading unit according to a setting value provided through the interface unit;
And a channel estimating module for calculating a channel parameter for adjusting the rake finger module based on the information provided through the Doppler filter bank unit and providing the channel parameter to the path search unit. The method according to claim 6,
And channel parameters calculated by the channel estimation module include a coherence time, a coherent frequency, an amplitude attenuation, and a phase rotation. The method according to claim 6,
And the channel estimating module calculates a finger time such that a time difference greater than at least ½ occurs in a chip period of a spreading code for spreading communication message bands.

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