KR100263540B1 - Circuit for tracking synchronization in code division multiple access - Google Patents

Abstract

PURPOSE: A fine synchronous tracing circuit is provided to be capable of performing fine synchronous tracing according to a finger and realizing a simple hardware. CONSTITUTION: An analog-to-digital converting part(1) restores a chip signal spreaded by a PN code by converting a received analog signal into a digital signal. A sampling part(2) samples a digital value of the analog-to-digital converting part, and at least two multiplexers(MUX1-MUX3) output a sample value of the sampling part corresponding to a selection signal. Finger fine synchronous tracing parts(F1-F3) are connected so as to correspond to the multiplexers. The finger fine synchronous tracing parts detects whether the sample value of the multiplexers are synchronized wit an internal reference clock and selectively output a phase difference signal. A control part(3) applies the selection signal to the finger fine synchronous tracing parts in response to the phase difference signal and outputs an oscillation control signal making the reference clocks of the finger fine synchronous tracing parts be oscillated at different points of time. A timing control part(4) makes the finger fine synchronous tracing parts oscillate the reference clocks in response to the oscillation control signal.

Description

Fine Sync Tracking Circuit in Code Division Multiple Access System

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a code division multiple access system (hereinafter referred to as CDMA), and more particularly, to a fine synchronization tracking circuit for matching a phase of an oscillation clock of a receiving device to a phase of a received signal. will be.

CDMA is one of modulation and multiple access schemes, and is based on the widely used Spread Spectrum Communication scheme. Recently, CDMA has been applied to digital mobile communication and advanced wireless communication.

In such a CDMA scheme, information to be transmitted is divided into I and Q channels, and the information of the I and Q channels is spread and transmitted as a pseudorandom code division technique.

The CDMA receiver is configured to demodulate the signal received over the I and Q channels as a plurality of fingers, and the reason for forming the plurality of fingers in this way is to increase the power of the received signal. That is, the received signals are received with a slight time difference by fading, so that the fingers can receive signals delayed by the fading by operating the fingers with a slight time difference, and add the signals received to the fingers. This improves the total received power over using one finger.

On the other hand, in order for these fingers to demodulate the received signal, the synchronization with the received signal must be continuously synchronized even after the initial synchronization is obtained, and a circuit for allowing the fingers to continuously synchronize with the received signal is called a fine synchronization tracking circuit. do.

Conventionally, as a method of implementing such a fine synchronization tracking circuit, a digitizer is implemented for each finger, or a digitizer is configured only on a finger that is responsible for a path having the strongest signal strength. As a method, a method of tracking motivation was used.

Here, the digitizer is composed of a sampling circuit and a multiplexer. The sampling circuit extracts the received chip signal into a predetermined number (for example, eight samples) and applies the multiplexer to the multiplexer. One sample of these is applied to the finger. That is, the finger determines whether or not the sample from the multiplexer is synchronized with the internal oscillation clock. If the synchronization is not matched, the finger outputs a phase difference signal and causes the multiplexer to select another sample to match the synchronization between the received signal and the oscillation clock. It is to let.

However, such a conventional method has a problem that the digitizer has to be configured for each finger, thus complicating the configuration of hardware and counteracting the technology trend of small size and light weight.

In addition, the method of tracking synchronization by synchronization matching on the finger that has the strongest signal strength can be implemented as a single digitizer, but in this method, only a finger connected to the main finger or the digitizer can receive the received signal. There is a problem that the synchronization with the other fingers, there is a lot of fear that the other fingers lose their motivation.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to provide a fine sync tracking circuit capable of fine sync tracking by finger, and to simply implement a hardware configuration.

1 is a block diagram of a fine synchronization tracking circuit in a code division multiple access system according to the present invention;

<Description of the code | symbol about the principal part of drawing>

1: Analog / digital converter 2: Sampling unit

3: control unit 4: timing control unit

MUX1-MUX3: Multiplexer F1-F3: 1-3 Finger Fine Sync Tracker

The present invention provides a synchronization tracking circuit of a code division multiple access system receiver, comprising: an A / D conversion unit for restoring a chip signal spread by a PN code by converting a received analog signal into a digital; A sampling unit for sampling the digital values of the A / D conversion unit by a predetermined number per chip; At least two or more multiplexers for outputting sample values of the sampling unit corresponding to the selection signal; A number of finger fine sync trackers connected to the multiplexer, the same number of finger fine sync trackers as the multiplexer for detecting whether the sample value from the multiplexer is synchronized with the internal reference clock and selectively outputting a phase difference signal; A control unit which applies a selection signal to the multiplexers in response to the phase difference signal, and outputs an oscillation control signal for causing the reference clocks of the finger fine sync trackers to start oscillation at different times; And a timing controller for controlling the finger fine sync trackers to oscillate the reference clock according to the oscillation control signal.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of an apparatus according to the present invention, wherein received analog signals are converted into digital signals through an analog / digital converter (hereinafter referred to as an A / D converter) 1. Therefore, the digitally converted signal through the A / D converter 1 will be in the form of a chip spread with the PN code at the transmitting side.

The digital signal from the A / D converter 1 is applied to the sampling unit 2, and the sampling unit 2 samples the digital signal with the system clock, for example, to sample and output 8 samples per chip. It is composed.

Eight sample values per chip in the sampling unit 2 are applied to the multiplexers MUX1-MUX3, respectively, as shown, and the multiplexers MUX1-MUX3 correspond to eight sample values corresponding to the selection signal of the controller 3. One of them is applied to the first to third finger fine sync trackers F1 to F3, respectively. Here, the sample values applied to the first to third finger fine sync trackers F1 to F3 by the multiplexers MUX1 to MUX3 will be different from each other.

The sample values from the multiplexer MUX1-3 are applied to the first to third finger fine sync trackers F1 to F3, and the first to third finger fine sync trackers F1 to F3 are connected to the timing controller 4. By controlling, the internal reference clock is oscillated, and it is detected whether the synchronization between the reference clock and the sample values from the multiplexer MUX1-3 match. If the synchronization between the sample value and the reference clock does not match, the first to third finger fine sync tracking units F1 to F3 apply a phase difference signal corresponding thereto to the controller 3.

Meanwhile, the above-described timing controller 4 oscillates the reference clocks of the first to third finger fine sync trackers F1 to F3 according to the oscillation control signal of the controller 3, and generates oscillation reference clocks according to the phase change signal. Selectively delay or advance, i.e., control the phase.

Here, as described above, the fingers operate with a slight time difference, and therefore, the oscillation timing of the internal reference clock in the first to third finger fine sync tracking units F1 to F3 should coincide with the operation timing of the fingers. For example, the fingers corresponding to the first finger fine sync tracker F1 are referred to as the first finger, the fingers corresponding to the second and third finger fine sync trackers F2 and F3, and the first and second fingers. When the -3 fingers are driven sequentially, the timing controller 4 oscillates the internal finger clocks of the finger fine sync tracker F1 and then oscillates the finger fine sync trackers F2 and F3 sequentially. Since the reference clock oscillation time points of the finger fine sync trackers F2 and F3 are different from each other, the samples of the sampling unit 2 in synchronization with the oscillation clocks of the first to third finger fine sync trackers F1 to F3 are synchronized. The values will be different from each other.

Accordingly, the controller 3 applies the selection signal for selecting the different sample values to the multiplexer MUX1-3 so that the multiplexer MUX1-3 receives the different sample values from the first to third finger fine sync trackers. F1-F3).

The first to third finger fine sync tracking units F1 to F3 receive different sample values from the multiplexer MUX1-3, and track the sync between the input sample values and the internal reference clock, and if the syncs are out of sync. By outputting the corresponding phase difference signal, the controller 3 is informed that the synchronization with the sample value inputted is out of sync.

According to whether the phase difference signal is input, the controller 3 may detect the first to third finger fine sync trackers F1 to F3 that are out of sync among the first to third finger fine sync trackers F1 to F3. The select signal for changing the sample value is applied to the multiplexer MUX1-3 corresponding to the out-of-sync first to third finger sync trackers F1 to F3. That is, the controller 3 outputs a selection signal for selecting a sample value of the sampling unit 2 in synchronization with the reference clocks of the first to third finger fine synchronization tracking units F1 to F3. The finger fine sync tracking units F1 to F3 may input a sample value coinciding with the internal clock.

However, the aforementioned method of tracking the input sample value and the internal clock by the first to third finger fine sync trackers F1 to F3 advances the input sample value by half a chip with respect to the internal clock, and provides a correlation value. Since the phase difference is detected by comparison, when the input sample value and the internal clock have a phase difference of more than half of each other, the phase difference cannot be accurately detected. Therefore, in this case, it is necessary to change the phase of the reference clock of the first to third finger sync tracking units F1 to F3.

That is, the controller 3 is configured to display the eight sample values per chip and the interior of the first to third finger fine sync tracking units F1 to F3 based on the phase difference signals of the first to third finger fine sync trackers F1 to F3. If it is determined that the clock does not coincide by more than half a chip, the timing controller 4 causes the timing controller 4 to apply the phase change signal to the phase of the oscillation reference clock of the corresponding first to third finger fine sync trackers F1 to F3. To change. That is, the controller 3 controls the timing controller 4 to change the phase of the oscillation reference clocks of the first to third finger fine sync trackers F1 to F3. The oscillation reference clock of F1-F3) is synchronized to one of eight sample values.

From the foregoing description, it can be seen that in the present invention, the samples sampled through one sampling unit can synchronize the synchronization of the internal reference clocks of the fingers.

That is, in the related art, the same number of digitizers as the fingers are used to match the reference clocks of the plurality of fingers with the sampled samples, and the digitizers include one sampling unit and a multiplexer as described above. In this case, the same number of sampling units as the fingers shall be used. However, in the present invention, since only one sampling unit is configured, and the sample value of the sampling unit can be selectively applied to multiple fingers, only one sampling unit can obtain the same effect as the conventional art.

As described above, the present invention can easily configure a fine synchronization tracking circuit for each finger, thereby making it possible to reduce the size and weight of the CDMA receiver.

Claims (2)

A synchronization tracking circuit of a receiver of a code division multiple access system, An A / D converting unit for restoring the chip signal spread by the PN code by converting the received analog signal into digital; A sampling unit sampling the digital values of the A / D conversion unit by a predetermined number per chip; At least two or more multiplexers for outputting sample values of the sampling unit in response to a selection signal; A number of finger fine sync trackers connected to the multiplexer, respectively, and detecting the synchronization between a sample value from the multiplexer and an internal reference clock and selectively outputting a phase difference signal; A control unit configured to apply a selection signal to the multiplexers in response to the phase difference signal, and output an oscillation control signal for causing the reference clocks of the finger fine sync trackers to start oscillation at different times; And a timing controller for controlling the finger fine sync trackers to oscillate the reference clock according to the oscillation control signal. The method of claim 1, The controller is configured to output a phase change signal for changing a phase of the reference clock when the reference clock and the sample values of the finger fine sync tracker determine that a phase difference of at least a half chip is generated by the phase difference signal; And the timing controller is configured to change a phase of a reference clock of the finger fine sync tracker in response to the phase change signal.

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