JP2000353980A - Spread spectrum communication apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spread spectrum communication apparatus for preventing the failure of voice communication at the time of controlling the transmission output of a slave device without increasing the number of parts or costs. SOLUTION: A master device 1 and a slave device 41 of the spread spectrum communication apparatus are provided with spreaders 3 and 43 which output spreads spectrum modulation signals according to spreading codes, high frequency transmitting parts 4 and 44 which convert the spread spectrum modulation signals, and output high frequency signals, inverse spreading code generators 18 and 58, inverse spreaders 13 and 53 which output modulation signals according to the inverse spreading codes, demodulators 15 and 55 which demodulate the modulation signals, receiving sensitivity detectors 14 and 54 which detect RSSI, synchronization abnormality detectors 26 and 66, and central processing parts 27 and 67, respectively. A transmitting part 4 outputs a transmission signal in a constant level, and a central processing part 67 of the slave device controls the output level of the transmission signal of the slave device based on the RSSI from the receiving sensitivity detector 54.

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 master unit and a slave unit that are cordlessly connected to each other by using a spread spectrum communication system.

[0002]

2. Description of the Related Art In recent years, Federal Comuni has been developed.
sessions Commissi-on (FCC, US Federal Communications Commission) Ind for spread spectrum communications
us-trial, Scientific and M
Since the release of the electronic (ISM) band (band for industrial science and medical care), products using the spread spectrum communication method have appeared in various communication devices 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 digital communication systems, and are more complicated and expensive than products using conventional analog communication systems. For this reason, an inexpensive spread spectrum communication apparatus has been devised in which a simple circuit for performing spreading and despreading is added to a conventional analog communication apparatus. Hereinafter, a spread spectrum communication device based on an analog communication device will be described with reference to the drawings.

FIG. 5 is a block diagram showing a conventional spread spectrum communication apparatus.

In FIG. 5, reference numeral 1A denotes a master unit, and 41A denotes a slave unit which can communicate with the master unit 1A by radio. The base unit 1A performs, as a constituent element, an FM that performs primary modulation for putting an information signal on a high frequency and outputs it as a narrow-band FM modulation signal 7
Modulator 2, a PN code generator 6 as a spread code generator for generating a spread code (PN code) 8, a narrow band FM modulated signal 7 from the FM modulator 2, and a spread code from the PN code generator 6. 8, a spreader 3 for generating a spread spectrum modulated signal 9, and an RF transmitter (high frequency transmitter) 4 for converting the spread spectrum modulated signal 9 from the spreader 3 to a high frequency, amplifying the signal, and outputting a high frequency transmission signal. A transmitting antenna 5 for transmitting a high-frequency signal (high-frequency transmitting signal) 10 from the RF transmitting unit 4, a receiving antenna 11 for receiving a high-frequency signal from the slave unit 41A, and amplifying the received high-frequency signal for spread spectrum modulation. An RF receiving section (high-frequency receiving section) 12 for converting into a signal 19 and a PN code generator 18 as a despreading code generator for generating a despreading code (PN code) 25
And the spread spectrum modulated signal 1 from the RF receiver 12
9, a despreader 13 for generating an original FM modulated signal 20 from the despread code 25 from the PN code generator 18, a high-frequency signal from the slave 41A and the PN code generator 1 of the master 1A.
Synchronizing circuit 17 for synchronizing with PN code 25 from 8
A / D for converting an input analog signal (RSSI voltage) 22 into a digital signal (RSSI digital data) 23
It has a converter (ADC) 16 and an RSSI circuit, converts the FM modulated signal 20 from the despreader 13 into an intermediate frequency signal (narrow band FM modulated signal) 21 and
(Intermediate frequency section) 14 for detecting RSSI (reception sensitivity) based on the FM modulation signal 20 from the
FM demodulator 1 for demodulating M-modulated signal 21 into an original information signal
5, an out-of-synchronization detector (synchronous abnormality detector) 26 for monitoring out-of-synchronization (synchronous abnormality) during communication, and a CPU (central processing unit) 27 for managing the operation of the entire system.

[0005] The slave unit 41A has exactly the same configuration as the master unit 1A.

That is, the slave unit 41A is a constituent element.
Performs first-order modulation to put an information signal on a high frequency and performs FM
An FM modulator 42 for outputting a modulation signal 47, a PN code generator 46 as a spreading code generator for generating a spreading code (PN code) 48, an FM modulation signal 47 from the FM modulator 42 and a PN code generator A spreader 4 for generating a spread spectrum modulated signal 49 from a spread code 48 from
3 and the spread spectrum modulated signal 49 from the spreader 43
Transmitting section (high-frequency transmitting section) 44 for converting the signal to a high-frequency and amplifying and outputting a high-frequency transmitting signal; transmitting antenna 45 for transmitting high-frequency signal (high-frequency transmitting signal) 50 from RF transmitting section 4; A receiving antenna 51 for receiving a high-frequency signal from the transmitter 1A, an RF receiving section (high-frequency receiving section) 52 for amplifying the received high-frequency signal and converting it to a spread spectrum modulation signal 59, and a despreading code (PN code) 65. A PN code generator 58 as a despreading code generator,
A despreader 53 for generating an original FM modulation signal 60 from a spread spectrum modulation signal 59 from an RF receiver 52 and a despread code 65 from a PN code generator 58;
A synchronization circuit 57 for synchronizing the high-frequency signal from the PN code 65 from the PN code generator 58 of the slave unit 41A,
It has an A / D converter (ADC) 56 for converting an input analog signal (RSSI voltage) 62 into a digital signal (RSSI digital data) 63 and an RSSI circuit, and converts an FM modulated signal 60 from a despreader 53 into an intermediate frequency signal. An IF unit (intermediate frequency unit) 54 that converts the signal into a (narrow band FM modulated signal) 61 and detects RSSI (reception sensitivity) based on the FM modulated signal 60 from the despreader 53 and a narrow band FM modulated signal 61 An FM demodulator 55 for demodulating the original information signal,
An out-of-synchronization detector (synchronization abnormality detector) 66 for monitoring an out-of-synchronization (synchronization abnormality) during communication, and a CPU (central processing unit) 67 for managing the operation of the entire system.

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

[0008] The information signal input to the master unit 1A is converted by the FM modulator 2 into the same narrow band F as that of a conventional analog communication apparatus.
The result is an M-modulated signal 7. The narrow-band FM modulation signal 7 is further modulated by the spreader 3 by the spreading code 8 generated by the PN code generator 6 to become a spread spectrum modulation signal 9. Further, the signal (high-frequency 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 high-frequency signal transmitted from master unit 1A is received by reception antenna 51 of slave unit 41A,
The signal is amplified by the RF receiver 52 and converted into a spread spectrum modulated signal 59. The despreader 53 multiplies the spread spectrum modulation signal 59 from the RF receiver 52 by the despread code 65 generated by the PN code generator 58. At this time, the timing of the PN code generator 58 is controlled by the synchronization circuit 57 and is synchronized with the spread spectrum modulation signal 59, so that the FM modulation signal 6 is output from the despreader 53.
0 is obtained. This FM modulated signal 60 is converted into an intermediate frequency signal (narrow band FM modulated signal) 61 by the IF unit 54, and the intermediate frequency signal 61 is demodulated by the FM demodulator 55 into the original information signal.

The synchronizing circuit 57 is a kind of a sliding correlator using the RSSI voltage of the IF section 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 1A have exactly the same code and speed. When the signal level after being converted to the intermediate frequency signal 61 by the IF unit 54 is monitored by the RSSI voltage 62, the phase of the despread code 65 and the phase of the spread spectrum modulation signal 59 are synchronized, and when the correlation value is maximum, The maximum RSSI voltage 62 is obtained. By sliding the phase of the despreading code 65, this maximum RS
By capturing and tracking the phase at which the SI voltage 62 is obtained,
Perform reverse diffusion. Actually, RSSI voltage 62 is A / D
It is converted into RSSI digital data 63 by the converter 56,
Capture the peak position of this RSSI digital data 63
The synchronization circuit 57 adjusts the phase of the PN code generator 58 in accordance with the phase adjustment signal 64 so as to hold the signal.

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

First, in the synchronous acquisition mode, 1
A rough synchronization position is determined in units of / 2 chips.

(A) 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 digital data 63 at that time and the phase.

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

(C) This content is repeated for all phases in units of 1/2 chip, and the position at which the RSSI digital data 63 is maximized 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 in order to further finely adjust and hold the phase. The procedure of the synchronization holding mode is as follows.

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

(B) The phase is shifted by 1/8 chip in an arbitrary direction, and the despreading code 65 is output for a certain period of time.
The SI digital data 63 is compared with the previously recorded data, and based on the result, the next phase change direction is determined.

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

Further, the communication state is monitored by the out-of-synchronization detector 66 from the state of the output of the FM demodulator 55 during communication. When the state indicating “out of synchronization” has continued for a certain period of time, the CPU 67 resets the synchronization circuit 57 by a reset signal 69. 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.

As described above, the input information signal to the base unit 1A is
In the description of the process of reproduction on the 1A side, communication is performed in exactly the same manner from the input of the information signal of the slave 41A to the output of the information signal of the master 1A in the opposite direction.

The spread spectrum communication apparatus based on the analog communication apparatus as described above has the following advantages as compared with the digital system.

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

(B) 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.

(C) Especially in a system for transmitting speech, there is no need to encode speech, so that there is no delay in speech caused by the encoding circuit.

[0026]

However, in the above-mentioned conventional spread spectrum communication apparatus, when controlling the transmission output which is generally performed on the slave unit 41A side in order to save current, there is an obstacle to voice communication. Had the problem of causing This problem will be described below.

In an ordinary digital spread spectrum communication apparatus, the master unit monitors the reception state, and a request to increase or decrease the transmission output is given to the data to be transmitted according to the reception state. On the slave side, the transmission output is increased or decreased according to this request, thereby reducing unnecessary current of the transmission unit. Generally, the slave unit is often driven by a battery, and current reduction is very important.

However, in the case of a spread spectrum communication device based on an analog communication device, it is relatively difficult to put data other than the input information signal on the communication during the communication.
For example, in the case of a device for transmitting voice such as a cordless telephone, when data in a voice band is used, an unpleasant data sound is heard every time the data is transmitted. In this case, there is no choice but to mute each time the data of the above-mentioned audio band is transmitted or leave it as it is, both of which hinder communication. Therefore, a method of using data outside the voice band is often used, but the cost and the number of parts are inevitable, including a filter for separating the data signal from the information signal.

In this spread spectrum communication apparatus, it is required to prevent a voice communication failure at the time of transmission output control of the slave unit without increasing the number of parts and the cost.

An object of the present invention is to provide a spread spectrum communication apparatus capable of preventing a voice communication failure during transmission output control of a slave unit without increasing the number of parts and costs.

[0031]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a spread spectrum communication apparatus according to the present invention comprises a base station and a base station which are cordlessly connected to each other using a spread spectrum communication system. And
The master unit and the slave unit each modulate an information signal and output a modulation signal, a spreading code generator that generates a spreading code, a modulation signal from the modulator and a spreading code from the spreading code generator. A spreader that outputs a spread spectrum modulated signal from a multiplexor, a high frequency transmitter that converts the spread spectrum modulated signal from the spreader to a high frequency and outputs it as a high frequency transmit signal, and a spread spectrum modulated signal that receives the high frequency transmit signal , A despreading code generator for generating a despreading code, and a despreading device for outputting a modulation signal from a spread spectrum modulation signal from the high frequency receiving portion and a despreading code from the despreading code generator A demodulator for demodulating a modulated signal from the despreader and outputting an information signal; a reception sensitivity detector for detecting RSSI based on the modulated signal from the despreader; And a central processing unit for controlling the whole, the high-frequency transmission unit of the master unit outputs a transmission signal of a certain level, and the central processing unit of the slave unit detects the reception sensitivity of the slave unit. A configuration is provided to control the output level of the transmission signal in the high-frequency transmission unit of the slave unit based on the RSSI from the device.

As a result, it is possible to obtain a spread spectrum communication apparatus capable of preventing a voice communication failure in controlling the transmission output of the slave unit without increasing the number of parts and the cost.

[0033]

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 comprising a base unit and a slave unit which are cordlessly connected to each other by using a spread spectrum communication system. , The master unit and the slave unit each modulate an information signal and output a modulation signal, a spreading code generator that generates a spreading code, a modulation signal from the modulator and a spreading code from the spreading code generator. A spreader that outputs a spread spectrum modulation signal from the transmitter, a high frequency transmission unit that converts the spread spectrum modulation signal from the spreader to a high frequency and outputs it as a high frequency transmission signal, and a spread spectrum modulation that receives the high frequency transmission signal and A high-frequency receiving unit that outputs a signal, a despreading code generator that generates a despreading code, a spread spectrum modulated signal from the high frequency receiving unit and a despreading code generator. A despreader that outputs a modulation signal from the despreading code, a demodulator that demodulates the modulation signal from the despreader and outputs an information signal, and detects RSSI based on the modulation signal from the despreader It has a reception sensitivity detector, a synchronization abnormality detector that detects a synchronization abnormality, and a central processing unit that controls the whole.The high-frequency transmission unit of the master unit outputs a transmission signal at a certain level, and the central processing unit of the slave unit. The unit controls the output level of the transmission signal in the high-frequency transmission unit of the slave unit based on the RSSI from the reception sensitivity detector of the slave unit.

According to this configuration, the output level of the transmission signal based on the RSSI is controlled in the slave unit, so that there is no increase in the number of parts, and therefore, the cost does not increase. It has the effect that prevention becomes possible.

According to the spread spectrum communication apparatus of the present invention, in the spread spectrum communication apparatus of the first aspect, the central processing unit of the master unit detects the synchronization error by the synchronization abnormality detector of the master unit, When the reception sensitivity detector of the device detects high sensitivity, the spread code generator of the master device is reset.

With this configuration, it is possible to notify the slave unit of the interference, and it is possible to prevent the interference state from being deteriorated by the transmission output control.

In the spread spectrum communication apparatus according to the third aspect, in the spread spectrum communication apparatus according to the first or second aspect, the central processing unit of the slave unit detects the synchronization error by the synchronization error detector of the slave unit. When the reception sensitivity detector of the slave unit detects high sensitivity, the output level of the transmission signal of the high-frequency transmission unit of the slave unit is fixed to the maximum.

This configuration has the effect of preventing repetitive deterioration of the interference state due to transmission output control.

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

(Embodiment 1) FIG. 1 is a block diagram showing a spread spectrum communication apparatus according to Embodiment 1 of the present invention.

In FIG. 1, the FM modulator 2, the spreader 3,
RF transmitting section 4, transmitting antenna 5, PN code generator (spreading code generator) 6, receiving antenna 11, RF receiving section 12,
Despreader 13, IF unit 14, FM demodulator 15, A / D converter 16, synchronization circuit 17, PN code generator (despread code generator) 18, out-of-synchronization detector (synchronous abnormality detector) 26, center Processing unit (CPU) 27, FM modulator 4
2, diffuser 43, RF transmitting section 44, transmitting antenna 45,
PN code generator (spreading code generator) 46, receiving antenna 51, RF receiving section 52, despreader 53, IF section 54, F
M demodulator 55, A / D converter 56, synchronization circuit 57,
PN code generator (despread code generator) 58, out-of-synchronization detector (synchronous abnormality detector) 66, central processing unit (CPU)
Since 67 is the same as that in FIG. 5, the same reference numerals are given and the description is omitted. Reference numeral 1 denotes a master unit, and 41 denotes a slave unit. The difference between the spread spectrum communication apparatus of FIG. 1 and FIG.
The transmission output control signal 70 is given from the CPU 67 on the first side to the RF transmission unit 44, and P
The point is that the reset signal 30 is given to the N code generator 6.

The feature of the operation in the first embodiment is that the transmission output of the base unit 1 is fixed, and the mobile unit 41 determines the increase or decrease of the transmission output in the RF transmission unit 44 according to the RSSI level of its own receiving system. The operation and the operation of notifying the slave unit 41 of the interference by resetting the spreading code generator 6 of the transmission system of the base unit 1 when the synchronization loss due to the interference occurs in the reception system of the base unit 1 When resynchronization occurs, the slave unit 41 fixes the transmission output to the maximum while communication on the channel is continued.

The operation of the spread spectrum communication apparatus configured as described above will be described with reference to FIGS. FIG. 2 is a flowchart showing a subroutine of transmission output control of the CPU 67 of the child device 41, FIG. 3 is a flowchart showing a subroutine of synchronization monitoring of the CPU 27 of the parent device 1, and FIG. It is a flowchart which shows the subroutine of monitoring.

In FIG. 2, when communication is normally performed (when an INTERFERENCE flag described later is "0") (S1), the slave 41 is a receiver of the slave 41 itself, and The electric field strength of the signal from 1 is monitored by the RSSI digital data 63 (S2). Based on the electric field intensity on the slave unit 41 side, the electric field intensity on the master unit 1 side is estimated, and if the RSSI value is high, the transmission output is switched to Low (S3), and if the RSSI value is low, the transmission output is High.
h (S4).

At this time, if the transmission output of the base unit 1 is also increased / decreased, the information of the transmission output control of the base unit 1 is not transmitted to the slave unit.
It becomes difficult to estimate the electric field strength on the base unit 1 side. Therefore, the transmission output control is performed only on the side of the slave 41 that needs to reduce the current for battery driving. As a result, the electric field strength at the base unit 1 can be estimated to some extent accurately based on the electric field strength at the sub unit 41 side.

However, the normal operation of the above control is limited to the transmission output control for the reception state based on the electric field strength. For example, it is assumed that the distance between master device 1 and slave device 41 is relatively short, and the RSSI value is sufficiently high, but interference occurs in the reception system of master device 1. In this case, since there is no failure in the reception system of the slave 41 and the RSSI value is high, the slave performs control to reduce the transmission output. However, interference has occurred on the master unit 1 side, and the reception situation is further degraded when the slave unit lowers the transmission output. In this state, it is necessary to notify the slave unit 41 of the fact that the master unit 1 is receiving interference by some method. Especially in the case of spread spectrum communication, besides interference on the same communication channel,
Since interference due to side lobes of adjacent channels also occurs, there are many opportunities for this problem to occur. Thus, it is necessary to notify the slave 41 of the interference of the master 1.

Next, an operation of notifying the slave unit 41 that the master unit 1 is receiving interference will be described with reference to FIG.

In FIG. 3, when a synchronization error (loss of synchronization) is detected on the master unit 1 side during communication (S11), the master unit 1 first checks with RSSI (S12). If the RSSI is low, it is considered that the PN code of the PN code generator 18 is reset by the receiving system reset signal 29 because it is considered that the communication range is out of the range and the synchronization cannot be maintained due to the weak electric field.
The resynchronization trial of the receiving system is repeated (S14). If the electric field strength is restored during this time, communication can be recovered.
Conversely, if the RSSI is high, it is considered that synchronization has been lost due to interference. This is because the RSSI is the sum of the energy that has passed through the IF unit 14, and therefore has a high value even if the synchronization is lost, if there is a certain electric field strength. In this case, when re-synchronizing the receiving system, the PN code generator 6 of the transmitting system is also reset by the transmitting system reset signal 30 to initialize the phase (S13). As a result, synchronization is lost even in the reception system of the slave unit 41. That is, the out-of-synchronization detector 66 of the slave unit 41 detects the out-of-synchronization.

Next, detection of a synchronization error in the slave unit 41 will be described with reference to FIG.

As shown in FIG. 4, even when the slave unit 41 detects a synchronization abnormality during communication (S21), similarly to the base unit 1, if the RSSI is low, it is determined that the electric field is weak and the receiving system reset signal 69 is determined. Resets the PN code of the PN code generator 58 and repeats the re-synchronization trial of the receiving system (S22, S2).
4). If the RSSI is high, the electric field strength is high but the synchronization has been lost, and it is determined that one of the following.

(A) There is interference in the reception system of the slave unit 41,
Synchronization can no longer be maintained.

(B) The reception system of the master unit 1 cannot maintain synchronization due to interference, and the master unit 1 resets the PN code generator 6 of the transmission system.

In any case, I indicates that there is interference.
"1" is set to the NTERRENCE flag (S23). If the INTERFERENCE flag is "1" (interference is present), the child device RSS in FIG.
Skip transmission output control by I value and set transmission output to Hi
gh side (S4 in FIG. 2). This is because, in the case of a synchronization abnormality due to interference, in a method of temporarily increasing the transmission power and returning to normal control when the state is improved, the same is repeated when the transmission power is reduced. As a result, it is possible to prevent the transmission output from dropping to Low and further deteriorating the reception situation due to interference.

The INTERFERENCE flag is
It is reset to "0" when the call ends or the communication channel is changed, and returns to the normal transmission output control.

In the case of voice transmission such as a cordless telephone, mute is applied to the voice system of both the base unit 1 and the slave unit 41 during the resynchronization trial of the reception system. As a result, unpleasant sounds are less likely to be generated in the voice system as compared with the data exchange method. In addition, since the mute is performed only during the resynchronization trial, the sound is not interrupted or the data sound is not heard every time the transmission output is controlled.

As described above, according to the present embodiment, high-frequency transmission section (RF transmission section) 4 of base unit 1 outputs a transmission signal of a fixed level, and central processing unit (CPU) 67 of sub-unit 41 By controlling the output level of the transmission signal in the high-frequency transmission unit (RF transmission unit) 44 of the slave unit 41 based on the RSSI from the reception sensitivity detector (IF unit) 54, the conventional device of FIG. As you can see from the comparison, the handset 4
In No. 1, it is only necessary to control the output level of the transmission signal based on the RSSI, and the number of parts does not increase.
Therefore, it is possible to prevent a voice communication failure when controlling the transmission output of the slave unit 41 without increasing the cost.

The central processing unit 27 of the base unit 1
When the synchronization abnormality detector 26 detects a synchronization abnormality and the reception sensitivity detector 14 of the base unit 1 detects high sensitivity, the spreading code generator 6 of the base unit 1 is reset.
Since it is possible to notify the slave unit 41 of the interference, it is possible to prevent the deterioration of the interference state due to the transmission output control.

Further, when the synchronization abnormality detector 66 of the slave unit 41 detects a synchronization abnormality and the reception sensitivity detector 54 of the slave unit 41 detects high sensitivity, the central processing unit 67 of the slave unit 41 By fixing the output level of the transmission signal of the high-frequency transmission section 44 to the maximum, it is possible to prevent the deterioration of the interference state due to the transmission output control from occurring repeatedly.

[0059]

As described above, according to the spread spectrum communication apparatus of the first aspect of the present invention, a spread spectrum communication system comprising a master unit and a slave unit that are cordlessly connected to each other by using a spread spectrum communication system. A communication device, wherein a master unit and a slave unit each modulate an information signal and output a modulation signal, a spreading code generator that generates a spreading code, and a modulation signal and a spreading code generation from the modulator. A spreader that outputs a spread spectrum modulation signal from a spread code from a transmitter, a high frequency transmission unit that converts a spread spectrum modulation signal from the spreader to a high frequency and outputs it as a high frequency transmission signal, and receives a high frequency transmission signal. A high-frequency receiver that outputs a spread-spectrum modulated signal, a despread code generator that generates a despread code, and a spread-spectrum modulated signal from the high-frequency receiver. A despreader that outputs a modulation signal from the despreading code from the spreading code generator, a demodulator that demodulates the modulation signal from the despreader and outputs an information signal, and a demodulator that outputs the information signal based on the modulation signal from the despreader A reception sensitivity detector for detecting the RSSI and a synchronization abnormality detector for detecting the synchronization abnormality,
A high-frequency transmission unit of the master unit outputs a transmission signal of a fixed level, and a central processing unit of the slave unit transmits a high-frequency signal of the slave unit based on the RSSI from the reception sensitivity detector. By controlling the output level of the transmission signal in the sub-unit, the slave only needs to control the output level of the transmission signal based on the RSSI, without increasing the number of parts and therefore the cost. This has the advantageous effect of preventing voice communication failure during transmission output control of the device.

According to the spread spectrum communication apparatus of the second aspect, in the spread spectrum communication apparatus of the first aspect, the central processing unit of the master unit detects the synchronization error by the synchronization error detector of the master unit. When the reception sensitivity detector of the base unit detects high sensitivity, by resetting the spread code generator of the base unit, it becomes possible to notify the slave unit of the interference, and the interference state is deteriorated by the transmission output control. Can be prevented.

According to the spread spectrum communication apparatus of the third aspect, in the spread spectrum communication apparatus of the first or second aspect, the central processing unit of the slave unit is configured such that the synchronization abnormality detector of the slave unit detects the synchronization abnormality. When the reception sensitivity detector of the slave detects high sensitivity, by fixing the output level of the transmission signal of the high-frequency transmission unit of the slave to the maximum, the deterioration of the interference state due to the transmission output control repeatedly occurs. This has the advantageous effect of preventing such a situation.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a spread spectrum communication apparatus according to a first embodiment of the present invention.

FIG. 2 is a flowchart of a transmission output control subroutine of a slave unit CPU;

FIG. 3 is a flowchart of a synchronization detection subroutine of a master CPU;

FIG. 4 is a flowchart of a subroutine CPU synchronization detection subroutine.

FIG. 5 is a block diagram showing a conventional spread spectrum communication apparatus.

[Explanation of symbols]

 1 Base Unit 2, 42 FM Modulator 3, 43 Spreader 4, 44 RF Transmitter (High Frequency Transmitter) 5, 45 Transmit Antenna 6, 46 PN Code Generator (Spread Code Generator) 7, 21, 61 Narrow Band FM modulated signal 8 PN code (spreading code) 9, 19, 59 Spread spectrum modulated signal 10 High frequency signal 11, 51 Receiving antenna 12, 52 RF receiving section (high frequency receiving section) 13, 53 Despreader 14, 54 IF section ( Intermediate frequency section, reception sensitivity detector) 15, 55 FM demodulator 16, 56 A / D converter (ADC) 17, 57 Synchronization circuit 18, 58 PN code generator (despread code generator) 20, 60 FM modulated signal 22, 62 RSSI voltage 23, 63 RSSI digital data 24, 64 Phase control signal 25, 65 PN code (despread code) 26, 66 Loss-of-synchronization detector Synchronization anomaly detector) 27,67 CPU (central processing unit) 28,68 synchronization monitoring signals 29,69 receiving system reset signal 30 transmission system reset signal 41 slave unit 70 transmits an output control signal

Claims (3)

[Claims] 1. A spread spectrum communication apparatus comprising a master unit and a slave unit which are cordlessly connected to each other using a spread spectrum communication system, wherein the master unit and the slave unit each modulate an information signal. A modulator that outputs a modulated signal, a spread code generator that generates a spread code, and a spreader that outputs a spread spectrum modulated signal from the modulated signal from the modulator and the spread code from the spread code generator, A high-frequency transmitting unit that converts the spread-spectrum modulated signal from the spreader to a high-frequency and outputs it as a high-frequency transmission signal; a high-frequency receiving unit that receives the high-frequency transmission signal and outputs a spread-spectrum modulated signal; A modulation signal is generated from a despreading code generator for generating a signal, a spread spectrum modulation signal from the high frequency receiving section, and a despreading code from the despreading code generator. A demodulator that demodulates the modulated signal from the despreader and outputs an information signal; a reception sensitivity detector that detects RSSI based on the modulated signal from the despreader; A synchronous abnormality detector for detecting an abnormality, and a central processing unit for controlling the whole; a high-frequency transmission unit of the master unit outputs a transmission signal of a certain level; and a central processing unit of the slave unit is the slave unit. A spread-spectrum communication apparatus for controlling an output level of a transmission signal in a high-frequency transmission unit of the slave unit based on RSSI from a reception sensitivity detector. 2. The central processing unit of the master unit, when the synchronization abnormality detector of the master unit detects a synchronization abnormality and the reception sensitivity detector of the master unit detects high sensitivity, the central processing unit of the master unit The spread spectrum communication apparatus according to claim 1, wherein the code generator is reset. 3. The central processing unit of the slave unit, when a synchronization abnormality detector of the slave unit detects a synchronization abnormality and a reception sensitivity detector of the slave unit detects high sensitivity, 3. The spread spectrum communication apparatus according to claim 1, wherein an output level of a transmission signal of the transmission unit is fixed to a maximum.