JP2941649B2 - Pseudo random code synchronizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pseudo random code synchronizer in a direct spread type spread spectrum communication, and more particularly to a pseudo random code synchronizer capable of acquiring a pseudo random code at high speed.

[0002]

2. Description of the Related Art In direct spread spectrum spread communication, a transmitting side spreads and modulates a transmission information signal using a pseudo random code, and spreads and transmits the signal in a frequency band much wider than the transmission information signal. . On the other hand, the receiving side performs despreading modulation for obtaining a correlation between the received signal and the pseudo random code, and demodulates the transmission information.

On the receiving side, in order to catch a target signal, the phase difference between the pseudo random code used for spreading modulation and the pseudo random code generated by the receiving side is a sufficiently small value (1).
/ 2 chips or less), and captures the synchronization of the pseudo-random code, and then performs synchronization tracking so as not to lose the captured synchronization.

A pseudo-random code synchronizer for securing the synchronization of such pseudo-random codes is disclosed in, for example, IEICE Vol. 65, no. 10, pp. 1053 ~
1058. As shown in FIG. 4, this device uses a voltage-controlled oscillator 44 that outputs a clock signal having a frequency proportional to the input voltage as a synchronization tracker 47, and a pseudo-random code 2 using a clock signal output from the voltage-controlled oscillator 44. , A pseudo-random code generator 43 for generating
And a correlator 46 for correlating the pseudo-random code 2 generated from the pseudo-random code 2 and a correlator 41 for correlating the input pseudo-random code 1 with the pseudo-random code 2 output from the synchronization tracker 47. A comparator 42 for comparing the output of the correlator 41 with the reference voltage 1; and a switch 45 for switching the voltage input to the voltage controlled oscillator 44 according to the output of the comparator 42.

[0005] In this device, the switch 45 first falls to the reference voltage 2 side, and the voltage controlled oscillator 44 outputs a clock signal at a frequency proportional to the reference voltage 2. The reference voltage 2 is set so that the clock frequency output from the voltage controlled oscillator 44 is slightly shifted from the frequency of the clock signal generating the pseudo-random code 1 to be input. The pseudo random code generator 43 is a voltage controlled oscillator
Pseudo random code 2 using clock signal output from 44
Occurs.

[0006] Pseudo random code 1 and pseudo random code 2
Means that on the time axis, the other slides with respect to one another due to a shift in the frequency of the generated clock signals, and when the phases match during the sliding process, the correlation value between the two codes increases, The output signal of the correlator 41 increases. When the output signal of the correlator 41 is higher than the optimally set reference voltage 1, the comparator 42 tilts the switch 45 toward the correlator 46, and ends the initial synchronization process (synchronization acquisition).

Thereafter, the process proceeds to the synchronization tracking process, and the voltage controlled oscillator 44 to which the output voltage of the correlator 46 has been input outputs a clock signal having the same frequency as the clock signal generating the pseudo random code 1, and The random code generator 43 uses the clock signal to generate a pseudo-random code 2 having the same phase as the input pseudo-random code and outputs it to the correlator 41. The correlator 41 uses the pseudo-random code 2 To perform despreading and demodulate the transmission information.

[0008]

However, in the conventional pseudo-random code synchronizing apparatus, in order to synchronously capture the pseudo-random code, the frequency of the clock generated by the pseudo-random code 1 and the frequency of the clock generated by the pseudo-random code 2 are changed. When the two codes are slid on the time axis with a shift, the phases of the two codes may hardly match each other. Such prolongation of the time required for synchronization acquisition becomes more remarkable as the code length of the pseudo-random code becomes longer, and the necessary data cannot be obtained in a short time, or the effective transmission efficiency of the data decreases. And other problems occur.

An object of the present invention is to solve such a conventional problem, and an object of the present invention is to provide a pseudo-random code synchronizer capable of acquiring a pseudo-random code in a short time.

[0010]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a pseudo-random code synchronizing apparatus for capturing the synchronization of a pseudo-random code that spreads and modulates transmission information on the receiving side of spread spectrum communication and tracking the synchronization. A band-pass filter that extracts a frequency component given by the reciprocal of the period of the pseudo-random code from the frequency components of the input pseudo-random code, a zero-cross comparator that detects a zero cross of the extracted frequency component signal, A signal edge detecting means for detecting the edge of the signal output from the zero-cross comparator, a delay means for delaying the signal output from the signal edge detecting means for a predetermined time, and an output signal of the delay means as an operation start signal. Synchronize pseudo-random code by outputting pseudo-random code of the same sequence as pseudo-random code It is provided and synchronization tracking means for starting a trace.

[0011]

When the frequency component given by the reciprocal of the period of the pseudo-random code is extracted from the frequency spectrum of the input pseudo-random code, the zero-crossing time of the signal of this frequency component is calculated from the start time of each period of the pseudo-random code. The time is shifted by a time uniquely determined by the target pseudo-random code. Therefore, by generating a pseudo-random code with a delay determined by the target pseudo-random code from the zero-crossing time, it is possible to generate a pseudo-random code having the same phase as the input pseudo-random code.

As described above, by utilizing the phase information of a specific frequency component in the inputted pseudo random code,
The initial synchronization process can be completed faster than in a conventional pseudo random code synchronizer.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a pseudo-random code synchronizer according to an embodiment of the present invention has a narrow-band filter (band-pass filter) 11 whose center frequency is the reciprocal 1 / T of the period T of the pseudo-random code 1. An amplifier 12 that amplifies the output of the band-pass filter 11, a zero-cross comparator 13 that detects a point in time when the output of the amplifier 12 crosses the zero level, and outputs a rectangular wave over a period in which the output of the amplifier 12 is at or above the zero level. And a signal edge detector for detecting the edge of the rectangular wave output from the zero-cross comparator 13
14, a delay unit 15 that delays a pulse output from the signal edge detector 14 for a predetermined time, and a synchronization tracker 16 that starts synchronization tracking of a pseudo random code by the pulse output from the delay unit 15. .

The pseudo random code 1 has a periodic waveform as shown in FIG. 3 (a). When the period is T, the signal sequence of the power density spectrum obtained by the discrete Fourier transform is
As shown in FIG. 2, the spectrum becomes a line spectrum standing at 1 / T intervals from the frequency 0.

The band-pass filter 11 has a center frequency of 1
/ T narrow band filter, which extracts only the component of frequency 1 / T in the pseudo random code 1. FIG. 3B shows an output signal of the band-pass filter 11. The output signal of the bandpass filter 11 becomes a sine wave, and the sine wave and the period of the pseudo random code 1 are naturally equal. As shown in FIG. 3A, when the start position of the pseudo-random code is uniquely determined, a time shift t from this start position to the zero cross of the sine wave component of frequency 1 / T in the pseudo-random code 1 is obtained.
Is uniquely determined by the pseudo-random code. This time lag t is preserved even after passing through the band-pass filter 11.

The output signal of the band-pass filter 11 is amplified by the amplifier 12, and the amplified signal is converted by the zero-cross comparator 13 into a rectangular wave having a period T as shown in FIG.

The rising edge detector 14 outputs a pulse signal synchronized with the rising edge of the output signal of the zero cross comparator 13 as shown in FIG. This pulse is synchronized with the zero cross of the sine wave component of the frequency 1 / T in the pseudo random code 1.

The delay time of the delay unit 15 is previously set to T−t obtained by subtracting the above-mentioned deviation t from the period T of the target pseudo random code, and the output pulse signal of the rising edge detector 14 is When passing through the delay unit 15, FIG.
As shown in (e), a pulse signal delayed by the time Tt and synchronized with the phase of the start position of the pseudo random code 1 is input to the synchronization tracker 16. The synchronization tracker 16 uses the output signal of the delay unit 15 as an operation start signal and generates a pseudo random code 2 having the same sequence as the pseudo random code 1 at the same phase from the start position of the pseudo random code 1. As a result, the output of the pseudo-random code 2 having the same phase as the pseudo-random code 1 from the synchronization tracker 16 is started, and the process of synchronization acquisition ends.

Thereafter, the synchronization tracking unit 16 performs a synchronization tracking process so that the pseudo random code 2 follows the pseudo random code 1 synchronously.

In this embodiment, a signal edge detector is used.
The rising edge of the rectangular wave output from the zero-cross comparator 13 is detected at 14, but the falling edge of this rectangular wave can be detected using a falling edge detector as a signal edge detector. In this case, the delay time of the delay unit 15 may be set to T / 2-t.

As described above, the pseudo random code synchronizer of the present invention utilizes the phase information of the frequency component contained in the pseudo random code to be synchronized and given by the reciprocal of the period of the pseudo random code. Since synchronization acquisition is performed, synchronization acquisition (initial synchronization process) can be completed at high speed.

[0022]

As is clear from the above description of the embodiment, the pseudo random code synchronizer of the present invention can quickly acquire the synchronization of the pseudo random code, and can quickly receive the transmitted data. This makes it possible to increase the effective transmission efficiency of data.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a pseudo random code synchronizer according to an embodiment of the present invention;

FIG. 2 shows a power spectrum of a pseudo-random code 1;

FIG. 3 is a waveform diagram of each signal in the pseudo-random code synchronizer according to the embodiment, where input pseudo-random codes 1 (a),
Waveform diagrams of the output signal (b) of the band-pass filter 11, the output signal (c) of the zero-cross comparator 13, the output signal (d) of the signal edge detector 14, and the operation start signal (e) output from the delay unit 15,

FIG. 4 is a block diagram showing a configuration of a conventional pseudo random code synchronizer.

[Explanation of symbols]

 11 Bandpass filter 12 Amplifier 13 Zero cross comparator 14 Signal edge detector 15, 46 Delay unit 16, 47 Synchronous tracker 41 Correlator 42 Comparator 43 Pseudo random code generator 44 Voltage controlled oscillator 45 Switch

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-276177 (JP, A) JP-A-2-132936 (JP, A) JP-A-1-117528 (JP, A) JP-A-1- 126034 (JP, A) JP-A-3-289831 (JP, A) JP-A-4-172728 (JP, A) JP-A-7-135481 (JP, A) JP-A-62-200923 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) H04B 1/707 H04L 7/00 H04L 7/10

Claims (1)

(57) [Claims] 1. A pseudo-random code synchronizing device for acquiring synchronization of a pseudo-random code which spread-modulates transmission information on a receiving side of spread spectrum communication and tracking the synchronization. A band-pass filter that extracts a frequency component given by the reciprocal of the period of the pseudo-random code, a zero-cross comparator that detects a zero-cross of the extracted signal of the frequency component, and a signal that is output from the zero-cross comparator. A signal edge detecting means for detecting an edge; a delay means for delaying a signal output from the signal edge detecting means by a certain time; and an output signal of the delay means as an operation start signal, and Synchronous tracking that outputs a pseudo-random code and starts synchronous tracking of the pseudo-random code Pseudorandom code synchronization apparatus characterized by comprising a means.