JP3366141B2 - Synchronous tracking device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synchronization tracking device for holding synchronization between a spreading code for demodulation and a spreading code included in a received signal in a receiver for receiving a spread spectrum signal.

[0002]

2. Description of the Related Art Generally, in mobile satellite communication, a spread spectrum communication system is adopted as a communication system. This spread spectrum communication system is, for example, a system in which an information signal is digitally modulated, then spread modulated by a spread code and transmitted.

In order to demodulate the original information signal from the spread spectrum received signal, a spread code (hereinafter referred to as "receive spread code") having the same phase as the spread code included in the received signal (hereinafter referred to as "receive spread code"). "It is called" spread code for demodulation ").

In order to obtain this demodulation spreading code, a synchronization acquisition device for pulling the phase of the demodulation spreading code to the phase of the reception spreading code and the phase of the demodulation spreading code pulled by this synchronization acquisition device are held. A sync tracking device is required.

As the latter synchronization tracking device, a delay locked loop circuit (hereinafter referred to as "DLL circuit") is conventionally known as described in the following document. Reference: Digital Mobile Communication Technology, Vol. 2, Chapter 4, "Spread Spectrum Communication", Masashi Sato, Japan Industrial Technology Center Co., Ltd., 1
February 25, 988.

This DLL circuit prepares a late code whose phase is behind that of the demodulating spread code and an early code whose phase is ahead of it, and calculates the autocorrelation between these and the receive spread code to determine the difference between the two autocorrelations. The phase of the spreading code for demodulation is controlled so that becomes 0.

In such a configuration, if the phase of the demodulating spread code matches the phase of the receive spread code, the difference between the two autocorrelations becomes zero. Therefore, if the phase of the spreading code for demodulation is controlled so that the difference in autocorrelation becomes zero, the phase of the spreading code for demodulation can be converged to the phase of the spreading code for reception.

[0008]

However, the DLL
The conventional synchronization tracking device using a circuit has the following problems.

That is, in the conventional synchronization tracking device using the DLL circuit, the calculation range of the autocorrelation calculation (the integration range of the autocorrelation function) (hereinafter referred to as "correlation length") is set in advance, and this correlation length is set. Based on this, the autocorrelation between the late code and the early code and the reception spread code is obtained.

However, the radio wave propagation environment of the spread spectrum signal changes every time the mobile body moves. Therefore, in the configuration in which the correlation length is fixed as in the conventional case, when the correlation length is long and the fading speed is high, the synchronization tracking accuracy deteriorates, and in the worst case, the synchronization is lost and the communication is interrupted. There was a problem.

[0011]

In order to solve the above problems, the present invention detects the phase difference between a demodulation spreading code and a reception spreading code using autocorrelation calculation, and based on this detection output, A means for controlling the phase of the spreading code for demodulation and a means for detecting the fading speed of the received signal and controlling the correlation length of the autocorrelation calculation based on the detected output are provided.

[0012]

In the above structure, the fading speed of the received signal is sequentially detected during communication. Then, the correlation length of the autocorrelation calculation is controlled based on this detection output. As a result, the correlation length of the autocorrelation calculation is adaptively changed according to the change of the fading speed. as a result,
Even if the fading speed becomes faster, it is possible to prevent the synchronization tracking accuracy from deteriorating.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. In the following description, a case where a pseudo noise code (hereinafter, referred to as “PN code”) is used as a spread code will be described as a representative.

In the figure, 11 is an input terminal to which a spread spectrum received signal is supplied.

Numeral 12 is a demodulation P using autocorrelation calculation.
The phase difference between the N code C1 and the reception PN code is detected, and the phase of the demodulation PN code C1 is controlled based on the detected output, so that the synchronization between the demodulation PN code C1 and the reception PN code is maintained. It is a synchronization tracking unit. This synchronization tracking unit 12
Is composed of, for example, a DLL circuit.

Reference numeral 13 is an output terminal to which the synchronization tracking section 12 is supplied with the demodulation PN code C1 in which synchronization is maintained. The output terminal 13 is connected to a correlation detector (not shown) for demodulating a primary-modulated information signal from the received signal.

Reference numeral 14 is a maximum Doppler frequency detector for detecting the maximum Doppler frequency of the received signal. The maximum Doppler frequency detection unit 14 detects the maximum Doppler frequency in a cycle longer than the calculation cycle of the autocorrelation calculation of the synchronization tracking unit 12 (for example, a cycle that is an integer multiple of 2 or more).
In this case, if the calculation period of the autocorrelation calculation is on the order of 1 ms, the maximum Doppler frequency detection period is, for example,
It is set to the 1s order.

Reference numeral 15 is a maximum Doppler frequency detector 14
Based on the maximum Doppler frequency detected by
It is a correlation length control unit that controls the correlation length of the autocorrelation calculation of the synchronization tracking unit 12. The correlation length control unit 15 shortens the correlation length when the detected maximum Doppler frequency becomes high,
The correlation length is controlled so that it becomes longer when it becomes lower.

In the synchronization tracking unit 12, 121 is a PN code for generating a demodulating PN code C1, a late code C2 whose phase is delayed by Δ from this demodulating PN code, and an early code C3 whose phase is advanced by Δ. It is a generator. here,
Δ is set to be, for example, half or less of the phase difference of one symbol of the PN code. In addition, this PN
The code generator 121 includes, for example, a shift register and an exclusive OR circuit.

Reference numeral 122 is a correlator that calculates the autocorrelation between the late code C2 output from the PN code generator 121 and the received PN code. Similarly, 123 is a correlator that calculates the autocorrelation between the early code C3 output from the PN code generator 121 and the received PN code. The correlation length of these two correlators 123 is variable, and the correlation length control unit 15
It is controlled by.

Reference numeral 124 is a difference calculator which detects the phase difference between the demodulating PN code C1 and the received PN code by obtaining the difference between the two autocorrelations calculated by the correlators 122 and 123.

Reference numeral 125 is a loop filter for filtering the subtraction result of the difference calculator 124. 126 is
A voltage controlled oscillator (VCO) whose oscillation frequency is controlled by the output of the loop filter 125. The oscillation output of the voltage controlled oscillation circuit 126 is the PN code generator 121.
Used as a clock signal for driving the shift register of the.

The synchronization tracking unit 1 having the above-mentioned configuration
2, the correlators 122 and 123 and the difference calculator 1
24 constitutes a phase difference detecting means for detecting the phase difference between the demodulating PN code C1 and the received PN code. Further, by the loop filter 125 and the voltage controlled oscillator 126,
Phase control means for controlling the phase of the demodulation PN code C1 is configured based on the detection output of the phase difference detection means.

In the maximum Doppler frequency detector 14, 141 is a correlator that calculates the autocorrelation between the demodulating PN code C1 output from the PN code generator 121 and the received PN code. The correlation length of the correlator 141 is fixed. The correlation length is calculated by the correlators 122 and 123.
Is set to be longer than the correlation length of. As a result, the maximum Doppler frequency detection period is
It is set to be longer than the calculation cycle of the autocorrelation calculation in the synchronization tracking unit 12.

Reference numeral 142 is a maximum Doppler frequency detecting circuit for detecting the maximum Doppler frequency based on the signal indicating the autocorrelation calculated by the correlator 141. The maximum Doppler frequency detection circuit 142 frequency-analyzes the correlation signal by, for example, fast Fourier transform, and detects the frequency with the highest power as the maximum Doppler frequency.

In the correlation length control unit 15, reference numeral 151 is a memory for holding the first relational table,
Reference numeral 152 is a memory that holds the second relational table. Here, the relational table is a table in which a plurality of maximum Doppler frequencies and an optimum correlation length for each maximum Doppler frequency are registered in a corresponding state.

In the first relational table, a rough maximum Doppler frequency (for example, a maximum Doppler frequency every 10 Hz) and an optimum correlation length corresponding to each maximum Doppler frequency are registered in advance at the time of factory shipment. ing. Therefore, the memory 151 holding the first relational table is composed of, for example, a non-volatile memory.

On the other hand, in the second relational table, prior to this communication, the maximum Doppler frequency actually detected and the optimum correlation length are registered for each communication in correspondence with each other. . Therefore, the memory 152 that holds the second relational table is configured by, for example, a random access memory.

Reference numeral 153 is a relational table creating circuit for creating a second relational table. This relational table creation circuit 152 is, for example,
Based on the preamble signal, which is a test signal sent prior to actual communication, the maximum Doppler frequency is detected for a predetermined period and at a predetermined cycle, and the detected maximum Doppler frequency and the optimum correlation length are calculated. Register in relational table 1.

Reference numeral 154 is a correlation length setting circuit for setting the correlation length of the correlators 122 and 123 based on the maximum Doppler frequency detected by the maximum Doppler frequency detection circuit 142. The correlation length setting circuit 154 searches the maximum Doppler frequency detected by the maximum Doppler frequency detection circuit 142 on the first and second relational tables, and finds the correlation length corresponding to the searched maximum Doppler frequency in the correlator 122. , 123.

FIG. 2 shows the correlators 122,
It is a block diagram which shows an example of a concrete structure of 123.

The illustrated correlators 122 and 123 are multipliers 1
a and a variable length correlation circuit 2a. Where the multiplier 1
a is the spread code (late code C2 or early code C3) output from the PN code generator 121 and the received P
It has a function of multiplying the N code by one symbol period of the spread code output from the PN code generator 121.

The variable length correlation circuit 2a has a function of averaging the multiplication results of the multiplier 1a by a predetermined number of symbols.
The averaged output of the variable length correlation circuit 2a becomes a correlation signal. Also, the number of symbols for averaging is the correlation length.
The number of symbols is variable and controlled by the correlation length controller 15.

The correlator 141 of the maximum Doppler frequency detector 14 is also the correlator 122, 12 of the synchronization tracking unit 12.
3 has almost the same configuration. However, in this correlator 141, the number of symbols of the correlation circuit corresponding to the variable length correlation circuit 2a is fixed and is set to be larger than the number of symbols of the variable length correlation circuit 2a.

FIG. 3 is a block diagram showing an example of a concrete configuration of the relational table creation circuit 153. The illustrated relational table creation circuit 152 has a correlator 1b, a maximum Doppler frequency detection circuit 2b, and a data writing circuit 3b.

The correlator 1b, for each communication, outputs the PN contained in the preamble signal sent prior to this communication.
Code and PN for demodulation output from PN code generator 121
It has a function of calculating an autocorrelation with the code C1. The correlation length of the correlator 1b is fixed and is the same as the correlation length of the correlator 141 of the maximum Doppler frequency detection unit 14.

The maximum Doppler frequency detection circuit 2b has a function of frequency-analyzing the correlation signal output from the correlator 1b by, for example, fast Fourier transform, and detecting the frequency with the highest power as the maximum Doppler frequency.

The data writing section 3c has a function of writing the maximum Doppler frequency detected by the maximum Doppler frequency detecting circuit 2b and the optimum correlation length for the maximum Doppler frequency in the second relational table.

The correlator 1b and the maximum Doppler frequency detection circuit 2b are used prior to communication. On the other hand, the correlator 141 of the maximum Doppler frequency detection unit 14 and the maximum Doppler frequency detection circuit 142 are used during communication. Therefore, one correlator and one maximum Doppler frequency detection circuit are used as the correlator 1b and maximum Doppler frequency detection circuit 2b before communication, and during communication,
It may be used as the correlator 141 and the maximum Doppler frequency detection circuit 142.

The above is the configuration of one embodiment. Next, the operation of the above configuration will be described. First, the overall operation of FIG. 1 will be described.

The received signal input from the input terminal 11 is
It is supplied to the synchronization tracking unit 12. This enables demodulation PN
The phase difference between the code C1 and the received PN code is detected. Then, the phase of the demodulating PN code C1 is controlled based on the detected output. As a result, the phase of the demodulating PN code C1 is converged to the phase of the receiving PN code.

At the same time, the maximum Doppler frequency detecting section 14 detects the maximum Doppler frequency of the received signal. As a result, the fading speed of the received signal is detected. This detection is performed in a cycle longer than the calculation cycle of the autocorrelation calculation of the synchronization tracking unit 12.

The maximum Doppler frequency detected by the maximum Doppler frequency detector 14 is supplied to the correlation length controller 15. Thereby, the correlation length of the autocorrelation calculation in the synchronization tracking unit 12 is controlled based on the maximum Doppler frequency detected by the maximum Doppler frequency detection unit 14.

This control is performed such that the correlation length is shortened when the detected maximum Doppler frequency becomes high, and lengthened when the detected maximum Doppler frequency becomes low. This is because the fading speed increases as the maximum Doppler frequency of the received signal increases,
This is because when it becomes lower, it becomes slower. The reason why the correlation length is shortened as the fading speed becomes faster is that in such a case, if the correlation length is lengthened, the calculation error of the autocorrelation calculation becomes large.

By this control, the correlation length is adaptively changed according to the change in the maximum Doppler frequency detected by the maximum Doppler frequency detecting section 14. As a result, when the fading speed of the received signal becomes faster,
It is possible to prevent the synchronization tracking accuracy from decreasing.

The above is the overall operation of FIG. Next, the operation of each part of FIG. 1 will be described. First, the synchronization tracking operation by the synchronization tracking unit 12 will be described.

The received signal input from the input terminal 11 is
It is supplied to the correlators 122 and 123 of the synchronization tracking unit 12.
As a result, the autocorrelation between the PN code included in this received signal and the late code C2 and early code C3 output from the PN code generator 121 is calculated.

The correlation signal output from the correlator 122 is
The correlation signal supplied to the subtraction circuit 124 and output from the correlator 122 is subtracted. As a result, an error voltage signal indicating the phase difference between the reception PN code and the demodulation PN code C1 is obtained.

This will be described with reference to FIG. Figure 4
(A), (b)), (c) are correlators 122,
123 shows the output characteristics of the difference calculator 124. That is, in these figures, the horizontal axis represents the phase difference between the demodulating PN code and the received PN code, and the vertical axis represents the output signal level. Further, on the horizontal axis, Tc represents the phase difference for one symbol, and Δ represents the absolute value of the phase difference between the demodulating PN code C1 and the late code C2 or the early code C3.

Assuming that the PN code is a pure random code with infinite period, the output characteristic of the correlator 122 is as shown in FIG.
As shown in (b), the characteristic of the triangle is such that the maximum is −Δ. On the other hand, the output characteristic of the correlator 123 is shown in FIG.
As shown in (a), the characteristic of the triangle is such that Δ is maximum. As a result, the output characteristic of the difference calculator 124 becomes an S-shaped characteristic as shown in FIG.

Therefore, the demodulation PN code C is set so that the error voltage signal output from the difference calculator 124 becomes zero.
If the phase of 1 is controlled, this phase can be matched with the phase of the received PN code. This control is performed as follows.

That is, the error voltage signal output from the difference calculator 124 is filtered by the loop filter 125 and then supplied to the voltage controlled oscillator 126 as a control voltage signal. As a result, the oscillation frequency of the voltage controlled oscillator 126 is controlled according to the phase difference between the demodulation PN code and the reception PN code. In this case, the oscillation frequency is controlled to be high when the phase difference has a positive value, and to be low when the phase difference has a negative value.

The oscillation output of the voltage controlled oscillator 126 is PN
It is supplied to the code generator 121 as a clock signal of the shift register. As a result, the phase of the demodulation PN code C1 output from the PN code generator 121 is
It is controlled according to the phase difference between the code C1 and the received PN code. As a result, the phase of the demodulating PN code C1 is converged to the phase of the receiving PN code.

The demodulating PN code C1 output from the PN code generator 121 is supplied from the output terminal 13 to a correlation detector (not shown) and used as a spreading code for demodulating the received signal into a primary-modulated information signal. To be done.

The above is the synchronization tracking operation by the synchronization tracking unit 12. Next, the maximum Doppler frequency detection operation by the maximum Doppler frequency detection circuit will be described.

The received signal input from the input terminal 11 is supplied to the correlator 141. As a result, the autocorrelation between the PN code included in the received signal and the demodulating PN code C1 output from the PN code generator 121 is calculated. This calculation cycle is set longer than the calculation cycle of the correlators 122 and 123 as described above.

The signal indicating the calculated autocorrelation is supplied to the maximum Doppler frequency calculation circuit 142. Thereby, the correlation signal is frequency-analyzed by the fast Fourier transform. Then, the highest power among the analyzed frequencies is detected as the maximum Doppler frequency.

The above is the maximum Doppler frequency detection operation by the maximum Doppler frequency detection unit 14. Next, the correlation length control operation by the correlation length control unit 15 will be described.

The received signal input from the input terminal 11 is
It is supplied to the relational table creation circuit 153.
As a result, prior to communication, the maximum Doppler frequency of the received signal is detected at a predetermined period for a predetermined period based on the preamble signal. The detected maximum Doppler frequency is written in the second relational table set in the memory 152 together with the optimum correlation length.

After this, when communication is started, the maximum Doppler frequency detected by the maximum Doppler frequency detection circuit 142 is searched by the correlation length setting circuit 154 on the first and second relational tables. When the target maximum Doppler frequency is searched by this search, the correlation length corresponding to this is read. The read correlation length is set in the correlators 122 and 123.

This setting process is executed every time a new maximum Doppler frequency is detected by the maximum Doppler frequency detecting circuit 142. Thereby, the correlators 122, 1
The correlation length of 23 is adaptively changed according to the change of the maximum Doppler frequency of the received signal.

The above is the operation of each unit in FIG. next,
The operation of the correlator shown in FIG. 2 will be described. Now, assume that the illustrated correlator is the correlator 122 of the synchronization tracking unit 12.

In this case, the received signal is supplied to the multiplier 1a and is multiplied by the rate code C2 supplied from the PN code generator 121 for each symbol. This product output is
It is supplied to the averaging circuit 2a, added for several symbols, and then divided by the number of added symbols. As a result, the reception P
An autocorrelation between the N code and the late code is obtained.

Although detailed description is omitted, similar processing is performed also when the illustrated correlator is the correlator 123 of the synchronization tracking unit 12. This also applies to the correlator 141 of the maximum Doppler frequency detection unit 14.

The above is the operation of the correlator shown in FIG.
Next, the relational table creation circuit 15 shown in FIG.
The operation of No. 3 will be described.

The preamble signal sent prior to the communication is supplied to the correlator 1b. As a result, the PN code included in this preamble signal and the PN code generator 12
The autocorrelation with the demodulation PN code output from 1 is calculated.

The signal indicating the calculated autocorrelation is supplied to the maximum Doppler frequency detection circuit 2b and subjected to frequency analysis by the fast Fourier transform. Then, the highest power among the analyzed frequencies is detected as the maximum Doppler frequency.

The detected maximum Doppler frequency is supplied to the data writing circuit 3b. As a result, the detected maximum Doppler frequency and the optimum correlation length are written in the second relational table of the memory 152.

The above is the operation of one embodiment of the present invention. According to this embodiment, the following effects can be obtained.

(1) First, according to this embodiment, the maximum Doppler frequency of the received signal is detected, and the phase difference between the demodulating PN code C1 and the received PN code is detected based on the detected output. Since the correlation length of the autocorrelation calculation is controlled, depending on the change of the maximum Doppler frequency,
The correlation length can be adaptively changed. By this means, the correlation length can be adaptively changed according to the change of the fading speed of the received signal, so that it is possible to prevent the synchronization tracking accuracy from decreasing even if the fading speed becomes high.

(2) Further, according to this embodiment, the fading speed of the received signal is detected by detecting the Doppler frequency of the received signal. Therefore, the fading speed can be detected with a simple configuration. You can

(3) Further, according to this embodiment, in the cycle longer than the calculation cycle of the autocorrelation calculation of the synchronization tracking unit 12,
Since the maximum Doppler frequency is detected, the maximum Doppler frequency can be efficiently detected in a cycle corresponding to the actual moving speed of the moving body, and the maximum Doppler frequency can be detected in a cycle similar to the above calculation cycle. The configuration of the correlation length control unit 15 can be simplified as compared with the case of detection.

(4) According to this embodiment, as the relational tables, the first relational table roughly registering the maximum Doppler frequency and the second relational table minutely registered are set. Since it is created, and the latter is created for each communication, the memory capacity for holding the relational table can be reduced.

That is, as a method of creating the relational table, a method of creating a table in which the maximum Doppler frequency is finely registered can be considered. However, in this case, since this table has to be created over a wide frequency range, a large memory capacity is required.

On the other hand, if a table like this is created each time communication is performed, as in this embodiment,
This table only needs to be created for a narrow frequency range. This is because the moving speed of the mobile in each communication is
This is because each communication falls within a substantially constant range. As a result, according to this embodiment, it is possible to reduce the memory capacity for holding the relational table.

Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment.

(1) For example, in the above embodiment, the case where the present invention is applied to the synchronization tracking device for holding the synchronization between the demodulation spreading code and the reception spreading code by the DLL circuit has been described. However, the present invention detects the maximum Doppler frequency of the received signal and controls the correlation length of the autocorrelation calculation for phase difference detection based on the detected output.
Therefore, the present invention can be applied to any synchronization tracking device configured to detect the phase difference between the demodulation spreading code and the reception spreading code by the autocorrelation operation and control the phase of the demodulation spreading code based on the detected output. It can also be applied to a synchronous tracking device having such a configuration.

(2) In the above embodiment, the case where the maximum Doppler frequency of the received signal is detected by performing the Fourier transform on the correlation signal has been described. However, the present invention may be detected by other methods. For example, by wavelet transforming the correlation signal,
You may make it detect. Further, the detection may be performed by a method other than the detection method by such frequency analysis.

(3) Further, in the above embodiment, the case where the fading speed of the received signal is detected by detecting the maximum Doppler frequency of the received signal has been described. However, the present invention may be detected by other methods. For example, it may be detected by detecting the moving speed of the receiver.

(4) In the above embodiment, the case where the first relational table and the second relational table are used as the relational tables has been described. However, the present invention may use only the second relational table. In this case, this second
The relational table may be created for each communication or may be created in advance. However, in the latter case, a large memory capacity is required as described above.

(5) In addition to this, it is needless to say that the present invention can be variously modified without departing from the scope of the invention.

[0082]

As described above in detail, according to the present invention, the fading speed of the reception signal is detected, and the phase difference between the demodulation spreading code and the reception spreading code is detected based on the detected output. Since the correlation length of the autocorrelation calculation is controlled, the correlation length can be adaptively changed according to the change of the fading speed of the received signal. As a result, even if the fading speed of the received signal becomes faster,
It is possible to prevent the synchronization tracking accuracy from decreasing.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing an example of a specific configuration of a correlator according to an embodiment.

FIG. 3 is a block diagram showing an example of a specific configuration of a relay table creating circuit according to an embodiment.

FIG. 4 is a characteristic diagram for explaining the operation of the embodiment.

[Explanation of symbols]

11 ... Input terminal 12 ... Sync tracking unit 13 ... Output terminal 14 ... Maximum Doppler frequency detector 15 ... Correlation length control unit 121 ... PN code generator 122, 123, 141, 1b ... Correlator 124 ... Difference calculator 125 ... Loop filter 126 ... Voltage control transmission circuit 142, 2b ... Maximum Doppler frequency detection circuit 151, 152 ... Memory 153 ... Relational table creation circuit 154 ... Correlation length setting circuit 1a ... Multiplier 2a ... Variable length correlation circuit 3b ... Data writing circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 10-56402 (JP, A) JP 9-321663 (JP, A) JP 2-165749 (JP, A) JP 2 305240 (JP, A) JP-A-6-204969 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04L 7/00 H04B 1/707

Claims (5)

(57) [Claims] 1. A synchronization tracking device for maintaining synchronization between a spread code for demodulating an original information signal from a spread spectrum received signal and a spread code included in the received signal, wherein: Phase difference detection means for detecting a phase difference between the demodulation spread code and the spread code included in the received signal, and based on the detection output of the phase difference detection means, the phase of the demodulated spread code in the received signal Phase control means for controlling the phase of the demodulation spreading code so as to match the phase of the spreading code included therein, fading speed detecting means for detecting the fading speed of the received signal, and the detection output of the fading speed detecting means. On the basis of,
A synchronization tracking device, comprising: a calculation range control means for controlling the calculation range so that the calculation range of the autocorrelation calculation is narrowed when the fading speed is increased. 2. The phase difference detecting means includes a first autocorrelation calculating means for calculating an autocorrelation between a spreading code whose phase is delayed from the demodulating spreading code by a predetermined amount and a spreading code included in the received signal. Second autocorrelation calculating means for calculating an autocorrelation between a spread code whose phase is advanced by a predetermined amount from the demodulation spread code and a spread code included in the received signal; and the first and second autocorrelation calculation. The synchronization tracking device according to claim 1, further comprising: a difference calculating unit that detects the phase difference by calculating a difference in autocorrelation calculated by the unit. 3. The sync tracking device according to claim 1, wherein the fading speed detecting means is configured to detect the fading speed by detecting a maximum Doppler frequency of the received signal. . 4. The synchronization tracking device according to claim 1, wherein the fading speed detecting means is configured to detect the fading speed in a cycle longer than a calculation cycle of the autocorrelation calculation. 5. The calculation range control means, for each communication, prior to the communication, speed detection means for detecting a fading speed of the received signal, fading speed detected by the speed detection means and the fading speed. Information holding means for holding the optimum calculation range for the speed in a corresponding state, and during communication, the calculation range corresponding to the fading speed detected by the fading speed detection means is obtained from the information holding means, and 2. The synchronization tracking device according to claim 1, further comprising a calculation range setting means for setting as a calculation range of the autocorrelation calculation.