JP2001069034A - Spread spectrum communication system and synchronization latch method for it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spread spectrum communication system that can keep synchronization without increasing the number of components and the cost even when a reception electric field strength value is continuously increased. SOLUTION: Synchronization circuits 17, 57 is provided with a discrimination section which compares a preceding reception electric field strength value with this reception electric field strength value, decides a direction of phase correction of inverse spread codes 25, 65 on the basis of the comparison result and adjusts a phase of the inverse spread code, and a count section that discriminates how many number of times this reception electric field strength value exceeds the preceding reception electric field strength value continuously and decides a direction of phase correction on the basis of the discrimination result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread spectrum communication apparatus comprising a transmission section and a reception section using a spread spectrum communication system, and a method for maintaining synchronization in the apparatus.

[0002]

2. Description of the Related Art In recent years, FCC (Federal Communication)
Commission, the US Federal Communications Commission (ISC) for ISM (Industrial, Scientific and Med) for spread spectrum communications.
ical) Since the band was released, products using this method have appeared in various communication equipment fields such as cordless telephones. The spread spectrum communication system is characterized by excellent anti-interference and confidentiality. Also, by using this method, transmission with a larger output than in the case of the conventional analog communication method is approved by the FCC, which is advantageous in terms of communication distance. On the other hand, products using this system are generally based on a digital communication system, and an inexpensive spread spectrum communication device in which a simple circuit for performing spreading and despreading is added to a conventional analog communication device has been devised.

A spread spectrum communication device based on the above analog communication device will be described.

FIG. 1 is a block diagram showing a general spread spectrum communication apparatus.

In FIG. 1, reference numeral 1 denotes a master unit and reference numeral 41 denotes a slave unit. The master unit 1 and the slave unit 41 constitute a spread spectrum communication apparatus.

[0006] The base unit 1 includes, as constituent elements, an FM modulator 2 for performing primary modulation for putting an information signal on a high frequency, and a PN code generator 6 for generating a spread spectrum signal.
, A spreader 3, an RF transmitter for converting and modulating a modulated signal, that is, a spread spectrum signal, to a high frequency, a transmitting antenna 5 for transmitting a high frequency signal, and a receiving antenna 11 for receiving a high frequency signal from the slave 41. , Which amplifies the received high-frequency signal and converts it to IF (spread spectrum signal)
F receiver 12, PN code generator 18 and despreader 13 for returning the received spread spectrum signal to the original narrowband signal, and synchronizing the signal from handset 41 with the PN code of the receiver. And a synchronous circuit 17 for taking
DC) 16, an IF unit 14 having an RSSI circuit, an FM demodulator 15 for demodulating a narrow-band FM signal, an out-of-synchronization detector 26 for monitoring out-of-synchronization during communication, and managing the operation of the entire system. And a CPU (control unit) 27 for performing the operations.

[0007] The slave unit 41 has exactly the same configuration as the master unit 1. That is, the slave unit 41 includes the FM modulator 42, the spreader 43, the RF transmission unit 44, the transmission antenna 45, and the PN
Code generator 46, receiving antenna 51, RF receiving unit 5
2, the despreader 53, the IF unit 54, and the FM demodulator 55
, An AD converter (ADC) 56 and a synchronization circuit 57
A PN code generator 58, an out-of-synchronization detector 66,
And a CPU (control unit) 67.

The FM modulators 2, 42 and the spreaders 3, 4
3, RF transmitting units 4, 44, transmitting antennas 5, 45, PN
The code generators 6 and 46 constitute a transmission unit. In addition, receiving antennas 11 and 51, RF receiving units 12 and 52, despreader 1
3, 53, IF sections (intermediate frequency sections) 14, 54, FM demodulators 15, 55, AD converters (ADC) 16, 56,
Synchronization circuits 17 and 57, PN code generators 18 and 58, out-of-synchronization detectors 26 and 66, CPUs (control units) 27 and 67
Constitutes a receiving unit.

The operation of the spread spectrum communication apparatus configured as described above will be described below.

The information input to the master unit 1 is transmitted to the FM modulator 2
Thus, the narrow-band FM modulated signal 7 is the same as that of the conventional analog system. This narrow-band FM modulation signal 7 further includes P
The spreading code 3 generated by the N code generator 6
, And becomes a spread modulation signal (spread spectrum signal). Further, the transmission signal 10 converted and amplified to a high frequency by the RF transmission unit 4 is radiated from the transmission antenna 5. on the other hand,
The radio signal transmitted from base unit 1 is received by reception antenna 51 of handset 41 and output as a high-frequency signal,
This high frequency signal is amplified by the RF receiver 52. This R
The RF spread modulation signal (spread spectrum signal) 59 output from the F receiving section 52 is multiplied by a despreader 53 and a despread code 65 generated by a PN code generator 58. At this time, the timing of the PN code generator 58 is adjusted by the synchronization circuit 57.
By synchronizing with the RF spread modulation signal 59, the original narrow band FM modulation signal 60 is obtained as the output of the despreader 53. This narrow band FM modulated signal 60
The signal is converted and filtered into an intermediate frequency signal 61 by a unit 54 and demodulated into an original information signal by an FM demodulator 55.

The synchronizing circuit 57 is a kind of a sliding correlator using the RSSI voltage (reception electric field intensity value) of the IF unit 54, and its correlation operation will be described. The despreading code 65 used for despreading and the spreading code 8 at the time of spreading in the base unit 1 have exactly the same code and speed.
When the signal level after being converted and filtered to the intermediate frequency 61 by the IF unit 54 is monitored by the RSSI voltage 62, the phases of the despread code 65 and the RF spread modulation signal 59 are synchronized, and the maximum is obtained when the correlation value is the maximum. Is obtained. The phase of the despreading code 65 is slid, and the maximum R
Despreading is performed by capturing and tracking the phase at which the SSI voltage is obtained. In practice, the synchronizing circuit 57 adjusts the phase of the PN code generator 58 with the phase adjustment signal 64 so that the RSSI voltage 62 is converted into digital data by the A / D converter 56 and the peak position of this data is captured and held. I do.

The synchronization circuit 57 has two functions of synchronization acquisition and synchronization retention.
It has different operation modes. Hereinafter, examples of these two operation modes will be described.

First, in the synchronization acquisition mode, the following (1):
In steps (2) and (3), a rough synchronization position is determined in units of 1/2 chip.

(1) First, the PN code generator 58 outputs the despread code 65 at an appropriate phase for a certain period of time, and records the RSSI data 63 and the phase at that time.

(2) Next, the phase is shifted by チ ッ プ chip, and the despreading code 65 is output for a certain period of time. If the RSSI data 63 at that time is higher than the recorded value, RSS
The recorded value of the I data and the phase at that time are recorded. By repeating this, the maximum value of the RSSI data and the phase at that time are recorded.

(3) This content is repeated for all the phases in units of 1/2 chip, and the position at which the RSSI data becomes maximum is set as a synchronization point, and jumping to that phase completes synchronization acquisition.

After the completion of the synchronization acquisition, the mode is shifted to the synchronization holding mode for further fine phase adjustment and its holding. The procedure of the synchronization holding mode is as follows (1), (2) and (3).

(1) The despreading code 65 is output for a fixed time at the phase at the time of completion of synchronization acquisition, and the RSSI data 63 at that time is recorded.

(2) The phase is shifted by 1/8 chip in an arbitrary direction, and the despreading code 65 is output for a fixed time.
The SSI data 63 is compared with the previously recorded data, and the result is used to determine the next phase change direction. This is shown below.

RSSI rise → Next time shift 1/8 chip in the same direction RSSI fall → Next time shift 1/8 chip in the reverse direction No RSSI change → Next time no phase change (3) By repeating this, from the synchronization point Holds phase within ± 1/8 chip.

Further, during communication, the communication state is monitored by the out-of-synchronization detector 66 from the state of the output of the FM demodulator 55. When the state indicating “out of synchronization” has continued for a certain period of time, the CPU 67 issues a reception system reset 69 to the synchronization circuit 57. In this case, the synchronization circuit 57 returns from the synchronization holding mode to the synchronization acquisition mode and attempts to reacquire synchronization.

The information of the A / D converter 56 is CP
It is also input to U67, and is used for vacant channel determination at the start of communication, weak electric field warning, and the like.

The above is a description of the process in which the information input signal of the master unit 1 is reproduced on the slave unit 41 side.
Communication is performed in exactly the same manner from the information input on one side to the information output on the master unit 1 side.

The spread spectrum communication device based on the analog communication device as described above has the following advantages (1) to (3) as compared with the digital system.

(1) The circuit configuration and operation are very simple, and the cost is low.

(2) An FM demodulator is more advantageous than a demodulator in a digital system in terms of reception sensitivity, and can extend a communication limit distance.

(3) Especially in a system for transmitting voice, there is no need to code voice, so that there is no delay in voice caused by the coding circuit.

FIG. 5 is a block diagram showing the synchronizing circuits 17 and 57, and FIG. 6 is a flowchart showing the operation of the synchronizing circuits 17 and 57. FIG. 6 shows a conventional RSSI sampling operation and reception PN phase in the synchronization holding mode. Indicates a change operation.

In FIG. 5, reference numeral 70 denotes a judgment unit, and 71 denotes a memory.

In the flowchart of FIG.
Ance (advance phase by 1/8 chip) and RETARD
The instruction of (delaying the phase by 1/8 chip) is determined by comparing the previous sampling variable VALUE0 and the current sampling variable VALUE1 of the RSSI.

In FIG. 6, first, the determination unit 70 substitutes the current RSSI value into the current sampling variable VALUE1 in the memory 71 (S1). Next, the determination unit 7
0 compares the current sampling variable VALUE1 with the previous sampling variable VALUE0 (S2, S2
3). If it is determined in the comparison result that the current sampling value is high, it is next determined whether DIRECTION is 1 or 0 (S4). If DIRECTION = 1, the phase of the reception PN is advanced by 1/8 chip (S5). ), DIRE
If CTION = 0, the phase of the reception PN is delayed by 1/8 chip (S6). If it is determined in step 2 that the current sampling value is low, the DIRECTION stored in the memory 71 is inverted and the process proceeds to step 4 (S7). After the processing of step 5 or 6 is completed, the determination unit 70 replaces the previous sampling variable VALUE0 with the current sampling variable VALUE1 (S8). If it is determined in step 3 that the previous sampling variable VALUE0 and the current sampling variable VALUE1 are the same, the previous sampling variable VALUE0 is similarly replaced with the current sampling variable VALUE1 (S8).

FIG. 7 is a graph for explaining the operation when the electric field intensity monotonously increases at a certain speed in the synchronization holding mode. As shown in FIG. 7, when the RSSI sampling value increases each time (VALUE1> VALUE0), the reception PN is in the same direction (for example, ADVANCE).
Direction), and eventually loses synchronization. This situation occurs when the RSS
This is the case where the I change is greater than the change obtained by correlation and the monotonic increase continues for some time.

FIG. 8 shows a case of a monotonous descent (every time VALUE
1 is a graph showing the case of 1 <VALUE0). As shown in FIG. 8, in the case of a monotonous fall, ADVANCE and R
Since the movement proceeds alternately in the ETARD direction, the problem as in the case of FIG. 8 does not occur.

In an actual use state, in a system having transmission power switching, it is likely to occur when the transmission output is increased. In addition to the electric field strength, the information modulation is over-
It also occurs when is shaken.

[0035]

As described above, in the above conventional spread spectrum communication apparatus and the method for maintaining synchronization in the same, the value of the received electric field strength (RSSI voltage)
However, there has been a problem that when monotonically increasing at a certain speed, synchronization is lost.

In the spread spectrum communication apparatus and the method of maintaining synchronization in the spread spectrum communication apparatus, it is required that the synchronization be maintained without increasing the number of parts and cost even when the received electric field strength value continuously increases. .

The present invention provides a spread spectrum communication apparatus capable of maintaining synchronization without increasing the number of parts and cost even when the received field strength value continuously increases, and the received field strength value is continuously increased. It is an object of the present invention to provide a spread spectrum communication apparatus for maintaining synchronization without increasing the number of parts and the cost even when it rises, and a method of maintaining synchronization in the apparatus.

[0038]

SUMMARY OF THE INVENTION In order to solve this problem, a spread spectrum communication apparatus according to the present invention is a spread spectrum communication apparatus including a transmission unit and a reception unit using a spread spectrum communication system, wherein the transmission unit is An analog modulator that modulates an information signal to output a primary modulation signal, a spreader that generates a spread spectrum signal from the primary modulation signal output from the analog modulator, and a high frequency signal that generates a spread spectrum signal from the spreader. A high-frequency transmitting unit that transmits as a high-frequency signal, a high-frequency receiving unit that receives a high-frequency signal, and a despreader that generates a primary modulation signal using a despread code from a spread spectrum signal as a high-frequency signal from the high-frequency receiving unit And generating the intermediate frequency signal from the primary modulation signal from the despreader and detecting the received electric field strength value from the intermediate frequency signal. A synchronizing circuit for synchronizing the received high-frequency signal and the despreading code, an analog demodulator for demodulating the intermediate frequency signal and outputting an information signal, and a control unit for controlling the whole, A circuit that compares the previous received field strength value with the current received field strength value, determines a direction of phase correction of the despreading code based on the comparison result, and adjusts the phase of the despreading code; A determination unit that determines whether or not the current reception field strength value has continuously exceeded the previous reception field strength value by a predetermined number of times, and a counting unit that determines a phase correction direction based on the determination result. I have.

As a result, a spread spectrum communication apparatus capable of maintaining synchronization without increasing the number of parts and costs even when the received electric field strength value continuously increases is obtained.

To solve the above problem, a method for maintaining synchronization in a spread spectrum communication apparatus according to the present invention comprises a transmitting section and a receiving section, wherein the transmitting section modulates an information signal and outputs a primary modulation signal. A spreader that generates a spread spectrum signal from the primary modulation signal output from the analog modulator, a high frequency transmitting unit that transmits the spread spectrum signal from the spreader as a high frequency signal, and a receiving unit that transmits the high frequency signal. A high-frequency receiving unit for receiving, a despreader that generates a primary modulation signal using a despreading code from a spread spectrum signal as a high-frequency signal from the high-frequency receiving unit, and an intermediate frequency signal from the primary modulation signal from the despreader An intermediate frequency unit that generates and detects the received electric field strength value from the intermediate frequency signal, and a synchronization that synchronizes the received high frequency signal with the despread code Channel, an analog demodulator that demodulates an intermediate frequency signal and outputs an information signal, and a synchronization maintaining method in a spread spectrum communication apparatus having a control unit that controls the entire system. A step of comparing the received field strength value with the received field strength value, determining a phase correction direction of the despreading code based on the comparison result, and adjusting the phase of the despreading code; A counting step of determining whether or not the intensity value has continuously exceeded the predetermined number of times and determining the direction of the phase correction based on the determination result.

As a result, a method of maintaining synchronization in a spread spectrum communication apparatus for maintaining synchronization without increasing the number of parts and cost even when the received electric field strength value continuously increases is obtained.

[0042]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A spread spectrum communication apparatus according to a first aspect of the present invention is a spread spectrum communication apparatus including a transmission section and a reception section using a spread spectrum communication system, wherein the transmission section includes an information signal. An analog modulator that modulates the signal to output a primary modulation signal, a spreader that generates a spread spectrum signal from the primary modulation signal output from the analog modulator, and a high frequency that transmits the spread spectrum signal from the spreader as a high frequency signal A transmitting unit, a receiving unit, a high-frequency receiving unit that receives a high-frequency signal, a despreader that generates a primary modulation signal using a despread code from a spread spectrum signal as a high-frequency signal from the high-frequency receiving unit, An intermediate frequency section for generating an intermediate frequency signal from the primary modulation signal from the detector and detecting a received electric field strength value from the intermediate frequency signal; A synchronizing circuit for synchronizing the frequency signal with the despreading code, an analog demodulator for demodulating the intermediate frequency signal and outputting an information signal, and a control unit for controlling the whole; A determining unit that compares the received field strength value with the current received field strength value, determines a direction of the phase correction of the despreading code based on the comparison result, and adjusts the phase of the despreading code; A counting unit that determines whether or not the strength value has continuously exceeded the previous reception electric field strength value by a predetermined number of times, and determines the direction of the phase correction based on the determination result.

With this configuration, when the current reception field strength value exceeds the previous reception field strength value by a predetermined number of times, the direction of the phase correction of the despreading code is reversed in the opposite direction. Therefore, even when the received electric field strength value continuously increases, it is possible to provide control on the number of times that the phase correction is continuously performed in the same direction, and therefore, it is possible to prevent the loss of synchronization. Have.

According to a second aspect of the present invention, there is provided a method for maintaining synchronization in a spread spectrum communication apparatus, comprising a transmission unit and a reception unit, wherein the transmission unit modulates an information signal to output a primary modulation signal. And a spreader that generates a spread spectrum signal from the primary modulation signal output from the analog modulator, a high frequency transmission unit that transmits the spread spectrum signal from the spreader as a high frequency signal, and a reception unit.
A high-frequency receiving unit that receives a high-frequency signal, a despreader that generates a primary modulation signal using a despreading code from a spread spectrum signal as a high-frequency signal from the high-frequency receiving unit, and an intermediate signal from the primary modulation signal from the despreader. An intermediate frequency unit that generates a frequency signal and detects a received electric field strength value from the intermediate frequency signal, a synchronization circuit that synchronizes the received high frequency signal with the despread code, and demodulates the intermediate frequency signal to convert the information signal into an information signal. An analog demodulator that outputs and a synchronization maintaining method in a spread spectrum communication apparatus having a control unit that controls the whole, comparing a previous received electric field intensity value with a current received electric field intensity value, and comparing the comparison result with the received electric field intensity value. A determination step of determining the direction of phase correction of the despreading code based on the phase and adjusting the phase of the despreading code, It determines whether exceeded continuously constant number is obtained by the fact that with a counting step of determining the direction of the phase correction based on the determination result.

With this configuration, when the current reception field strength value exceeds the previous reception field strength value by a predetermined number of times, the direction of the phase correction of the despreading code is reversed in the opposite direction. Therefore, even when the received electric field strength value continuously increases, it is possible to provide control on the number of times that the phase correction is continuously performed in the same direction, and therefore, it is possible to prevent the loss of synchronization. Have.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG.

(Embodiment 1) The configuration of a spread spectrum communication apparatus according to Embodiment 1 of the present invention is the same as that of FIG. The difference between the spread spectrum communication apparatus according to the present embodiment and the conventional spread spectrum communication apparatus is the configuration and operation of synchronization circuits 17 and 57.

FIG. 2 is a block diagram showing synchronization circuits 17 and 57 constituting the spread spectrum communication apparatus according to the first embodiment of the present invention.

In FIG. 2, reference numeral 70 denotes a judgment unit, 71 denotes a memory, and 72 denotes a counting unit. Note that the determination unit 7 in FIG.
0, the counting section 72 may be constituted by any of hardware and software.

FIG. 3 is a flowchart for explaining the operation of synchronization circuits 17 and 57 constituting the spread spectrum communication apparatus according to the first embodiment of the present invention. Steps S11 to S13 in FIG. 3 correspond to steps S1 to S3 in FIG. 6, and steps S16 to S18 and S21 in FIG. 3 correspond to steps S4 to S6 and S8 in FIG. , S19 and S20 will be described.

In FIG. 3, if it is determined in step S13 that the current sampling value (reception electric field intensity value) is higher than the previous sampling value, then the determination unit 70 stores the count value in the memory 71. Is increased by 1 (S14). Next, the counting unit 72 determines whether the count value stored in the memory 71 is 4 or more (S15). When it is determined that the count value is 4 or more, the DIRECTION stored in the memory 71 is inverted (S19), and the count value is set to 0 (S20).
Move to step 16.

FIG. 4 is a graph showing that no synchronization loss occurs even when the electric field intensity monotonically increases at a certain speed in the synchronization holding mode. In FIG. 4, the sampling value of the RSSI voltage (reception electric field strength value) continues to rise as in the case of FIG. 7, but ADVANC
After E has been repeated 3 times, the fourth TR is forced to RETAR
Turn to D and repeat RETARD this time. RETAR
If D continues three times, it switches back to ADVANCE. Therefore, the phase correction of the received PN code (despreading code) is 3/8.
It is not possible to stay in the phase range within and keep going in the wrong direction and lose synchronization.

As described above, according to the present embodiment, synchronization circuits 17 and 57 compare the previous received electric field intensity value with the current received electric field intensity value, and despread code 25 based on the comparison result. , 65, and a determining unit 70 for adjusting the phase of the despreading codes 25, 65 and adjusting the phase of the despreading codes 25, 65, and that the current reception field strength value (RSSI voltage) is the previous reception field strength value for a predetermined number of consecutive times. It is determined whether or not the received electric field intensity value exceeds the previous received electric field intensity value by repeating the previous received electric field intensity value a predetermined number of times by providing the counting unit 72 for determining whether or not the received electric field intensity exceeds the previous received electric field intensity value. If it exceeds, the direction of the phase correction of the despreading code can be reversed in the opposite direction, so even if the received electric field strength value increases continuously, the phase correction is continued in the same direction. The number of times It may be provided control, thus it is possible to prevent out-of-sync.

[0054]

As described above, according to the spread spectrum communication apparatus according to the first aspect of the present invention, there is provided a spread spectrum communication apparatus including a transmission unit and a reception unit using a spread spectrum communication system. The unit modulates an information signal and outputs a primary modulation signal, a spreader that generates a spread spectrum signal from the primary modulation signal output from the analog modulator, and a spread spectrum signal from the spreader. A high-frequency transmitting unit that transmits as a high-frequency signal and a receiving unit include a high-frequency receiving unit that receives the high-frequency signal and an inverse that generates a primary modulation signal using a despread code from a spread-spectrum signal as a high-frequency signal from the high-frequency receiving unit. An intermediate frequency signal is generated from a primary modulation signal from a spreader and a despreader, and a received electric field strength value is detected from the intermediate frequency signal. An inter-frequency unit, a synchronization circuit that synchronizes the received high-frequency signal and the despread code, an analog demodulator that demodulates the intermediate frequency signal and outputs an information signal, and a control unit that controls the entire unit, The synchronization circuit compares the previous received electric field strength value with the current received electric field strength value, determines a phase correction direction of the despreading code based on the comparison result, and adjusts the phase of the despreading code. And, by having a counting unit that determines whether the current reception field strength value has exceeded the previous reception field strength value by a predetermined number of times continuously, and that determines the direction of phase correction based on the determination result, If the current reception field strength value exceeds the previous reception field strength value by a predetermined number of times in a row, the phase correction direction of the despreading code can be reversed in the opposite direction. Intensity value continually increases Even if you,
Control can be provided for the number of times that the phase correction is continuously performed in the same direction. Therefore, an advantageous effect that loss of synchronization can be prevented only by adding a counting unit is obtained.

According to a second aspect of the present invention, there is provided a method for maintaining synchronization in a spread spectrum communication apparatus, comprising a transmitting unit and a receiving unit, wherein the transmitting unit modulates an information signal to output a primary modulation signal. A spreader that generates a spread spectrum signal from the primary modulation signal output from the analog modulator, a high frequency transmission unit that transmits the spread spectrum signal from the spreader as a high frequency signal, and a reception unit that receives the high frequency signal A high-frequency receiving unit, a despreader that generates a primary modulation signal using a despreading code from a spread spectrum signal as a high-frequency signal from the high-frequency receiving unit, and generates an intermediate frequency signal from the primary modulation signal from the despreader An intermediate frequency unit that detects a received electric field strength value from the intermediate frequency signal, and a synchronization circuit that synchronizes the received high frequency signal with the despread code. A method for maintaining synchronization in a spread spectrum communication apparatus having an analog demodulator for demodulating an intermediate frequency signal and outputting an information signal, and a control unit for controlling the whole, comprising: a previous reception electric field intensity value and a current reception electric field intensity And the determination step of determining the phase correction direction of the despreading code based on the comparison result and adjusting the phase of the despreading code, and that the current received field strength value is the same as the previous received field strength value. A counting step of determining whether or not the number has continuously exceeded the predetermined number of times, and determining the direction of the phase correction based on the determination result. If it continuously exceeds, the direction of the phase correction of the despreading code can be reversed in the opposite direction, so even if the received electric field strength value continuously increases, Continuing in the same direction can be provided a control on the number of times the phase correction is made,
Therefore, an advantageous effect that loss of synchronization can be prevented only by adding a counting step is obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a general spread spectrum communication apparatus.

FIG. 2 is a block diagram showing a synchronization circuit included in the spread spectrum communication apparatus according to the first embodiment of the present invention.

FIG. 3 is a flowchart showing an operation of a synchronization circuit included in the spread spectrum communication apparatus according to the first embodiment of the present invention.

FIG. 4 is a graph showing that no synchronization loss occurs even when the electric field strength monotonically increases at a certain speed in the synchronization holding mode.

FIG. 5 is a block diagram showing a synchronization circuit.

FIG. 6 is a flowchart showing the operation of the synchronization circuit.

FIG. 7 is a graph for explaining the operation when the electric field intensity monotonously increases at a certain speed in the synchronization holding mode.

FIG. 8 is a graph showing a case of a monotonous descent.

[Explanation of symbols]

 2,42 FM modulator 3,43 Spreader 4,44 RF transmitter 5,45 Transmit antenna 6,46 PN code generator 11,51 Receiving antenna 12,52 RF receiver 13,53 Despreader 14,54 IF Unit (intermediate frequency unit) 15, 55 FM demodulator 16, 56 AD converter (ADC) 17, 57 Synchronous circuit 18, 58 PN code generator 26, 66 Loss-of-sync detector 27, 67 CPU (control unit)

Claims (2)

[Claims] 1. A spread-spectrum communication apparatus comprising a transmission unit and a reception unit using a spread-spectrum communication method, wherein the transmission unit modulates an information signal to output a primary modulation signal; A spreader that generates a spread spectrum signal from the primary modulation signal output from the analog modulator, a high frequency transmission unit that transmits a spread spectrum signal from the spreader as a high frequency signal, and the reception unit transmits the high frequency signal. A high-frequency receiving unit for receiving, a despreader that generates a primary modulation signal using a despreading code from a spread spectrum signal as a high-frequency signal from the high-frequency receiving unit, and an intermediate frequency from the primary modulation signal from the despreader. An intermediate frequency section for generating a signal and detecting a received electric field strength value from the intermediate frequency signal; and A synchronization circuit for synchronizing with the spread code, an analog demodulator for demodulating the intermediate frequency signal and outputting an information signal, and a control unit for controlling the whole; A determination unit that compares the value with the current reception field strength value, determines a phase correction direction of the despreading code based on the comparison result, and adjusts the phase of the despreading code; And a count unit for determining whether the intensity value has continuously exceeded the previous received electric field intensity value by a predetermined number of times, and determining a direction of the phase correction based on the determination result. Communication device. 2. An analog modulator for modulating an information signal and outputting a primary modulation signal, and a spectrum from the primary modulation signal output from the analog modulator. A spreader that generates a spread signal, a high-frequency transmitting unit that transmits a spread spectrum signal from the spreader as a high-frequency signal, and a high-frequency receiving unit that receives the high-frequency signal, and a high-frequency receiving unit that receives the high-frequency signal. A despreader that generates a primary modulation signal using a despread code from a spread spectrum signal as a high-frequency signal; and an intermediate frequency signal generated from the primary modulation signal from the despreader and a received electric field strength from the intermediate frequency signal. An intermediate frequency section for detecting a value, a synchronization circuit for synchronizing the received high frequency signal with the despread code, and demodulating the intermediate frequency signal to obtain information. A method for maintaining synchronization in a spread spectrum communication apparatus having an analog demodulator for outputting a signal and a control unit for controlling the whole, comprising: comparing a previous received electric field strength value with a current received electric field strength value; A determination step of determining the phase correction direction of the despreading code based on the result and adjusting the phase of the despreading code, and the current received electric field strength value continues the previous received electric field strength value by a predetermined number of times. And determining whether the phase correction direction has been reached based on the determination result.