JPH11196023A - Two-way transmitter-receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmitter-receiver of a spectrum diffusion system which does not use channels under communication of a narrow-band system to perform its communication. SOLUTION: The output signal level of a receiving mixer circuit 5 is detected in a narrow band by a narrow-band detection circuit 22, and it is decided whether the detected level is higher than a prescribed level. When the channel to be used is already being used in the narrow-band system communication, a first transmitter-receiver 1 and a second transmitter-receiver 23 are controlled in accordance with the output signal of the circuit 22. For instance, both transmitters-receivers 1 and 23 move to a next channel at the sometime and in a prescribed order.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-way transmission / reception apparatus for performing a two-way communication between a first and second transmission / reception apparatus in a time division manner on a signal modulated by a spread spectrum system.

[0002]

2. Description of the Related Art As shown in FIG. 6, a two-way transmission / reception system for performing two-way communication in a time-division manner is generally known. In the bidirectional transmission / reception system of FIG. 6, transmission / reception is performed using one of a plurality of communication channels. The selected channel is transmitted from the first transmitting / receiving device to the second transmitting / receiving device for a predetermined period using a predetermined RF frequency, and then from the second transmitting / receiving device to the first transmitting / receiving device for a predetermined period using the same RF frequency. Just send. This is TDD
(Time Division Dupulexer) It is called a communication system. By alternately repeating transmission and reception in a time division manner, communication between the first and second transmission / reception devices is achieved. Among such communication systems, there is a system using a spread spectrum system as a modulation and demodulation system. On the transmission side, for example, voice data or the like is subjected to spread spectrum modulation using a spread code, frequency-converted to an RF frequency and transmitted, and on the reception side, the spread spectrum modulated signal is subjected to spread spectrum demodulation using a spread code to obtain voice data and the like. .

[0003]

By the way, in the ISM band in the United States, there is no restriction on the modulation / demodulation method used. Therefore, the spread spectrum method, for example, SSB
There is a possibility that narrow band systems such as modulation and demodulation systems are mixed. In such a band, if the channel selected by the system of FIG. 5 is already used by the narrow band method, the transmission / reception signal by the narrow band method is spread over a wide band by the spread spectrum. There is a problem that interference occurs in the transmission / reception system.

[0004]

SUMMARY OF THE INVENTION The present invention provides first and second embodiments.
Using a plurality of communication channels between the transmitting and receiving devices,
In a two-way communication device for performing two-way communication of a signal modulated by a spread spectrum method, at least one of the first and second transmission / reception devices detects whether or not a reception level of transmission data is higher than a predetermined value. A control circuit for determining whether or not the currently used channel is an empty channel based on an output signal of the level detection circuit;
It is characterized by having.

[0005] In particular, when the reception level is lower than a predetermined value, the first and second transmission / reception devices perform normal reception as idle channels. Further, when the reception level is higher than a predetermined value, the first and second transmission / reception devices shift to another channel. Further, the control circuit on the transmitting side of the first and second transmitting / receiving devices includes means for sweeping a communication channel, means for detecting an empty channel for each channel, and transmitting transmission data including at least identification data and empty channel information. It is characterized by comprising transmitting means for performing the above.

[0006] Further, the control circuit of the transmitting / receiving apparatus on the receiving side includes a judging means for judging whether or not the identification data coincides with each other. It is characterized by comprising means for moving. Still further, the transmission and reception of the transmission data is performed by providing a control channel among the plurality of communication channels.

Further, the first and second transmission / reception devices include
The mobile terminal may simultaneously move to an empty channel based on the empty channel information. According to the present invention, transmission and reception by the spread spectrum method are performed in a weak electric field,
When there is communication using a narrow band method in a channel to be used, the reception level of transmission data is detected, and narrow band communication with a high reception level is detected. In the case of spread spectrum demodulation, a narrow band signal is spread so that level detection cannot be performed, so a signal before spread spectrum demodulation is used.

[0008]

FIG. 1 is a diagram showing an embodiment of the present invention. Reference numeral 1 denotes a first transmission / reception device using a spread spectrum system, reference numeral 2 denotes a first antenna connected to the first transmission / reception device 1, and reference numeral 3 denotes an RF reception amplifier, and a reception RF signal received via the first antenna. To amplify. Reference numeral 4 denotes a frequency synthesizer circuit, which is a well-known PLL.
And generates local oscillation signals fvr and fvt for reception and transmission corresponding to a specific channel. Reference numeral 5 denotes a reception mixing circuit, which converts the frequency of the output signal of the RF reception amplifier 3 into an IF signal using the reception local oscillation signal fvr. Reference numeral 6 denotes a spread spectrum demodulation circuit, which includes a sliding correlator for reproducing a spread code and synchronizing the reproduced spread code with a received spread code, and performing spread spectrum demodulation using the synchronized spread code.
The circuit using the method of L holds synchronization of the spread code. A digital demodulation circuit 7 digitally demodulates output data of the spread spectrum demodulation circuit 6 by, for example, FSK demodulation, PSK demodulation, or the like. Reference numeral 8 denotes a TDD control circuit which controls the first transmission / reception device to alternately perform data reception and data transmission, receives demodulated data at the time of data reception, and transmits data at the time of data transmission as described later. Reference numeral 9 denotes a data encoding / decoding circuit which decodes demodulated data output from the TDD control circuit 8 to output audio data, and encodes digitized input audio data as will be described later and encodes the TDD control circuit. 8 is output.
Reference numeral 10 denotes a D / A conversion circuit, which converts the decoded audio data into an analog signal to generate an output audio signal. An output audio amplifier 11 amplifies an output audio signal of the D / A conversion circuit 10 and drives a speaker 12.

An input audio amplifier 14 amplifies an input audio signal generated from the microphone 13. 15 is A
/ D conversion circuit, which converts the amplified input audio signal into a digital signal and outputs input audio data. Reference numeral 16 denotes a digital modulation circuit, which encodes digitized input voice data in a data encoding / decoding circuit 9 and further encodes the encoded data derived via the TDD control circuit 8 into, for example, FSK modulation, PSK modulation, or the like. Is digitally modulated by Reference numeral 17 denotes a spread spectrum modulation circuit, which spreads the modulated data of the digital modulation circuit 16 using a transmission spread code. Reference numeral 18 denotes a transmission mixing circuit, which frequency-converts the spread spectrum transmission signal into a transmission RF signal using the transmission local oscillation signal fvt. Reference numeral 19 denotes a transmission RF amplifier that amplifies a transmission RF signal. Reference numeral 20 denotes a reception RF signal that receives a reception RF signal received by the antenna 2 during a data reception state.
A switch that supplies the signal to the amplifier 3 and guides the transmission RF signal to the antenna 2 during the data transmission period. In addition, 21
Transmits data to and from the TDD control circuit 8 and
A microcomputer 22 for controlling the control circuit 8 and the frequency synthesizer circuit 4 is a narrow band level detection circuit for detecting the signal level of the output signal of the reception mixing circuit 5 in a narrow band around a predetermined frequency.

The first transmission / reception device 1 alternately switches between a data reception state and a data transmission state at predetermined intervals by the TDD method. Switching between the reception state and the transmission state is performed under the control of the TDD control circuit 8, and the frequency synthesizer circuit 4,
Spread spectrum demodulation circuit 6, Spread spectrum modulation circuit 8
And the operation state of the switch 20 is switched.

In the data receiving state period, the frequency synthesizer circuit 4 causes the receiving local oscillation signal f
vr is generated, the demodulation operation of the spread spectrum demodulation circuit 6 is set to the operation state, the modulation operation of the spread spectrum modulation circuit 17 is set to the non-operation state, and the switch 20 is turned off in FIG.
The state shown in FIG. In this state, the antenna 2
The received RF signal is converted to a spread spectrum reception signal by frequency conversion, the received signal is subjected to spread spectrum demodulation and digital demodulation to obtain demodulated data, and further subjected to data decoding and analog conversion to obtain a voice signal. At the same time, the control data contained in the demodulated data is output from the TDD control circuit 8 to the microcomputer 21.

On the other hand, during the data transmission state period, the control signal TD
In response to D, the frequency synthesizer circuit 4 generates a local oscillation signal fvt for transmission, deactivates the spread spectrum demodulation circuit 6, activates the modulation operation of the spread spectrum modulation circuit 17, and activates the switch 20 in FIG. In a state opposite to that shown in FIG. Therefore, the input voice data is digitally converted and then data encoded, the encoded data and the control data from the microcomputer 21 are subjected to digital modulation and spread spectrum modulation, and then the frequency is converted to a transmission RF signal. Send.

Transmission and reception between the transmission and reception devices are performed alternately at predetermined intervals, but the operation from the D / A converter 10 to the speaker 12 and the operation from the microphone 13 to the A / D converter 15 are the above-mentioned alternate transmission and reception operations. Regardless, it always operates. In FIG. 1, reference numeral 23 denotes a second transmitting / receiving apparatus having the same configuration as that of the first transmitting / receiving apparatus 1;
The transmission / reception devices 1 and 23 constitute one set and the antennas 2 and 24
Is used to transmit and receive data. When the first transmitting / receiving device 1 is transmitting data, the second transmitting / receiving device 23
Is in a data receiving state, and conversely, the first transmitting / receiving apparatus 1 is in a data receiving state when the second transmitting / receiving apparatus 23 is transmitting data. Data transmission and reception are performed by switching these states alternately.

Hereinafter, using the timing chart of FIG. 2, the communication between the first and second transmitting / receiving apparatuses 1 and 23 of FIG.
The intermittent reception state, the initial synchronization state (the first state in which synchronization of the spread code on the receiving side is acquired), and the normal transmission / reception state will be described. Note that the first transmitting / receiving apparatus 1 will be described as, for example, a cordless telephone slave unit, and the second transmitting / receiving apparatus 23 as a master unit.
2A and 2C show the operation of the second transceiver 23, and FIGS. 2A and 2D show the operation of the first transceiver 1. FIG.

First, the intermittent reception state will be described.
In the intermittent reception state, as shown in FIG.
Is always in a data waiting state, and as shown in FIG.
The transmission / reception device 1 enters a data waiting state every few seconds. The microcomputer 21 of the first transmission / reception device 1 counts the time Ti1 (several seconds) by a built-in timer, and controls the TDD control circuit 8 so that the first transmission / reception device 1 enters the data receiving state after the time T1 has elapsed. That is, T
The DD control circuit 8 generates a time division control signal TDD, and in response to the control signal TDD, the frequency synthesizer circuit 4 generates a local oscillation signal fvr for reception, and a spread spectrum demodulation circuit 6
The demodulation operation of FIG.
The state shown in FIG. Therefore, the first transmission / reception device 1 enters the data reception state R0. Further, the TDD control circuit 8 counts the time Ti2 by the built-in timer, and sets the first transmitting / receiving device 1 to the data waiting state only during the period Ti2. In this period Ti2, the first transmitting / receiving device 1 can receive the transmission data from the second transmitting / receiving device 23 at any time. When the data waiting state ends, the first transmitting / receiving apparatus 1 operates only the microcomputer 21 to count the time Ti1.

Thereafter, the microcomputer 21 controls the circuits other than the microcomputer 21 to turn off after counting the time Ti1. And the time Ti
After 1 elapses, the first transmission / reception device 1 enters the data reception state again. By performing intermittent reception in this way,
Power saving can be achieved. Further, as will be described later, the data standby time Ti2 is set longer than the transmission / reception period of the initial synchronization, so that transmission data can be reliably received.

Next, a case where the first transmission data is transmitted from the second transmission / reception device 23 to the first transmission / reception device 1 (initial synchronization state) will be described. During the intermittent reception state of the first transmission / reception device 1, the second transmission / reception device 23 transmits the first transmission data at time t1 in FIG. At time t1, the operation of the first transmission / reception device 1 is off, so that a part of the transmission data is not received by the first transmission / reception device 1. Thereafter, at time t2 in FIG. 2A, the first transmitting / receiving device 1 enters a data waiting state, and the first transmitting / receiving device 1 cannot synchronize because the remaining part of the transmission data is received but only a part of the transmission data is received. And data cannot be reproduced. Therefore, the data waiting state of the first transmitting / receiving device 1 is continued.

Subsequently, at time t3 in FIG. 2A, when the next transmission data is transmitted from the second transmission / reception device 23, the transmission data is received by the first transmission / reception device 1 via the antenna 2,
The frequency is converted to a spread spectrum received signal, and the received signal is spread spectrum demodulated. The transmission data in the initial state is, as described later, a pilot carrier for synchronizing spread codes on the receiving and transmitting sides, followed by ID (identification) data, and control data for controlling calling, receiving and making a call. And Therefore, the first transmission / reception device 1 captures the synchronization of the spread code of the transmission data Tx in the pilot carrier period, and when the synchronization is maintained, obtains demodulated data by digital demodulation, and transmits the control data included in the decoded data. The microcomputer 21 outputs the signal from the TDD control circuit 8 to the microcomputer 21.

When transmitting the transmission data, the second transmission / reception device 23 transmits the transmission data Tx and simultaneously transmits the transmission data Tx.
The TDD control circuit of the transmitting / receiving device 23 resets the built-in timer and starts counting. On the other hand, when the first transmission / reception device 1 also receives the transmission data Rx, the TDD control circuit 8 resets the built-in timer and starts counting. The microcomputer 21 detects, for example, ID (identification) data in the control data and checks whether the detected ID data matches its own ID data. If the detected ID data matches its own ID data, the microcomputer 21 outputs control data to the TDD control circuit 8. TD
After the internal timer of the D control circuit 8 has counted the time Ti3 (time t4 in FIGS. 2A and 2B), if the ID data match, the first transmitting / receiving apparatus 1 enters the data transmission state, and the control data is transmitted to the spectrum. After spread modulation, transmission data T including a pilot carrier and a communication carrier as shown in FIG.
y is transmitted via the antenna 2. TDD at the same time as transmission
The built-in timer of the control circuit 8 is reset. On the other hand, when the internal timer counts the period T3 from time T3, the second transmission / reception device 23 enters the data reception state, and receives the transmission data Ty of the first transmission / reception device. Simultaneously with the reception, the built-in timer is reset. The second transmission / reception device 23 performs spread spectrum demodulation of the transmission data Ty, detects identification data from among them, and checks whether or not the identification data matches its own identification data. When the second transmitting / receiving device 23 confirms the coincidence of the identification data, the second transmitting / receiving device 23 maintains the data transmission state as it is.

In the initial synchronization state, the first and second transmission / reception devices 1 and 23 are locked to each other's transmission data, so that the spread spectrum reception unit of one transmission / reception device is switched to the spread spectrum transmission frequency of the other transmission / reception device. Since they match, the spread spectrum transmission / reception frequency between the transmission / reception devices can be matched with high accuracy. Also, the first
In addition, time management between the second transmitting / receiving apparatuses 1 and 23 can be performed with high accuracy.

Incidentally, the data waiting period Ti2 of the first transmitting / receiving device 1 is set to be three times as long as the data transmission period or the data reception period Ti3 at the time of the initial synchronization. It is assumed that the second transmitting / receiving device 23 has transmitted data in the initial synchronization state as shown in FIG. As shown in FIG.
If the start time of the data waiting is earlier than the time t1,
The first transmission / reception device 1 is synchronized with the first transmission data Tx. When the start time of the data waiting is later than the time t1 as shown in FIG. 2, the data is in the data waiting state in the middle of the first transmission data Tx, so that synchronization cannot be performed with the first transmission data Tx. The first transmission / reception device includes 2 transmission data Tx.
It is synchronized with the transmission data Tx. As described above, by setting the data waiting period T2 to be three times the data transmission / reception period Ti3, one data transmission period is always included in the data waiting period, so that transmission data can be reliably received in the data waiting state. become. FIG.
In the above description, the data waiting period Ti2 is set to be three times the data transmission period or the data reception period Ti3 at the time of the initial synchronization.
The present invention is not limited to this, and it may be set so that transmission data always enters the data waiting period. Therefore, the data waiting period Ti2 may be set to a period longer than twice the data transmission / reception period at the time of initial synchronization.

When the time T3 is counted in the first and second transmitting and receiving devices 1 and 23 after the second transmitting and receiving device 23 confirms the coincidence of the ID data, the time t shown in FIGS.
At 5, the first transceiver 1 and 23 are in the normal reception state. At time t5, the TDD control circuit 8 puts the first transmission / reception device 1 into the data reception state R1, resets the means for generating a spread code in the spread spectrum demodulation circuit 6, and generates the first spread code of a predetermined sequence. Further, the second transmission / reception device 23 enters the transmission state of the data T1, and resets the spread code at the time of spread spectrum modulation. By resetting the spreading code at the same time, the first and second transmitting / receiving devices 1
, And 23 have substantially the same pattern, so that the time required to acquire the synchronization of the spread spectrum is shortened.

The second transmission / reception device 23 transmits the transmission data T1, and the first transmission / reception device 1 receives it. The transmission data T1 includes a pilot carrier and a communication carrier as shown in FIG. The first transmission / reception device 1 receives dummy data during the pilot carrier period, and the spread spectrum demodulation circuit 6 performs synchronization acquisition based on the dummy data, and enters a synchronization holding operation. In the spread spectrum demodulation circuit 6, synchronization acquisition is performed using a sliding correlator. In the sliding correlator, it takes time from the start to the completion of synchronization acquisition. Therefore, the transmitting side replaces a part of the transmission data with, for example, data obtained by spectrally spreading the dummy data “0, 1, 0, 1,...”, And transmits the dummy data as a pilot carrier period. On the receiving side, the transmission data obtained by spectrum spreading the dummy data is used for synchronization acquisition, and the synchronization acquisition is completed within this pilot carrier period. Since synchronization can be acquired during the pilot carrier period, it becomes possible to spread-spectrum demodulate speech data while maintaining synchronization immediately after entering the communication carrier period. The pilot carrier period is provided so that synchronization acquisition can be completed even with a sliding correlator that takes a long time. Note that the dummy data is not limited to the above pattern, but may be “0, 0, 1, 1,.
0, 0, 1, 1, 1,...

Therefore, in the pilot carrier period of the transmission data T1 in FIG. 3A, the first transmitting / receiving apparatus 1 as shown in FIG.
Is the spread spectrum acquisition period. After the spread spectrum demodulation circuit 6 of the transmission data enters the synchronization holding state, it becomes a communication carrier period. The transmission data received by the first transmission / reception device 1 is spread spectrum demodulated, and then the control data and voice are transmitted by the TDD control circuit 8. Separated into data. The control data is output to the microcomputer 21, and the audio data is subjected to data decoding and then converted to analog to be audio.

At this time, the first and second transmitting / receiving apparatuses 1 and 2
3 from time t5 to time T5.
After counting 4, the transmission / reception state is inverted at time t6.
That is, the first transmission / reception device 1 is in the data transmission state, and the second transmission / reception device 23 is in the data reception state. At time t6
Then, the generation of the spread code in the spread spectrum modulation circuit 17 of the first transceiver 1 and the spread spectrum demodulator of the second transceiver 23 is reset.

At time t6 in FIGS. 2A and 2B, in the first transmitting / receiving apparatus 1, the TDD control circuit 8 generates data of repetition of "0" and "1",
To generate dummy data. The first transmitting / receiving apparatus 1 transmits the dummy data to the second transmitting / receiving apparatus 23 during the pilot carrier period shown in FIG. After a lapse of a predetermined time, the pilot carrier period ends, the TDD control circuit 8 combines and outputs the control data from the microcomputer 21 and the encoded audio data, and the spread spectrum modulation circuit 17 combines the output data. Is spread spectrum modulated. Therefore, the transmission data T2 is transmitted from the first transmission / reception device 1 during the communication carrier period.

During the data transmission of the first transmission / reception device 1, the second transmission / reception device 23 performs spread spectrum synchronization acquisition during a pilot carrier period, receives transmission data during a communication carrier period, and demodulates and decodes voice data and control data. I do. Then, when the time T4 elapses from the time t6, the transmission / reception state of the first and second transmission / reception devices 1 and 23 is reversed at the time t7. In the normal reception state, transmission and reception of the first and second transmission / reception devices 1 and 23 are repeatedly inverted by TDD.

Incidentally, the pilot carrier period in the normal reception state is set according to the time until the spread spectrum synchronization is acquired. When synchronization acquisition is started in the normal reception state, the means for generating the spreading codes on the transmitting side and the receiving side are reset, so that the sequences of the spreading codes on the transmitting side and the receiving side progress in substantially the same pattern. Therefore, the spreading codes between the first and second transmission / reception devices 1 and 23 are quickly synchronized. On the other hand, the transmission data Tx and Ty in the initial synchronization state are also formed by a combination of a pilot carrier and a communication carrier as shown in FIG. 3, and the data period is set longer than the transmission / reception data period Ti4 in the normal reception state. In the timing chart of FIG. 2, for example, the period Ti3 is the period Ti4
Is set to twice as large as In the initial synchronization state, when the first transmission / reception device 1 first starts the spread spectrum synchronization acquisition at time t3 in FIG. 2A, the spreading code in the transmission data Tx and the spreading code of the first transmission / reception device 1 have no pattern at all. Since they do not match, the time until the first transmission / reception device 1 acquires synchronization is longer than in the normal reception state. Therefore, by making the pilot carrier period of the initial synchronization longer than at the time of normal reception, it is possible to reliably capture the spread spectrum synchronization at the time of the initial synchronization. As a result, the communication carrier after the pilot carrier can be accurately demodulated. Note that only the pilot carrier period at the time of the initial synchronization may be longer than at the time of normal reception, or both the periods of the pilot carrier and the communication carrier may be longer than at the time of normal reception.

FIGS. 2C and 2D are timing charts when the first transmission data is transmitted from the first transmission / reception device 1 to the second transmission / reception device 23 at the time of initial synchronization. FIG.
At time t8 in d, the first transmission / reception device 1 transmits the transmission data, and the second transmission / reception device 23 in which the data waiting state is continued as shown in FIG. 2C receives this transmission data. The spread spectrum received signal is frequency-converted and the received signal is spread spectrum demodulated. After performing synchronous acquisition of spread spectrum, the second transmitting / receiving device 23 detects and confirms, for example, ID data. The ID data matches on the transmitting and receiving sides, and the period Ti
3 (time t9), the first and second transmission / reception devices 1
, 23 are inverted, and the second transmission / reception device 23 transmits the transmission data. Then, the first transmission / reception device 1 detects the identification data from the transmission data and checks whether or not the identification data matches the identification data of the first transmission / reception device 1 itself. Further, when a predetermined period Ti3 has elapsed and time t10 is reached, normal reception starts as shown in FIGS.

As described above, even when the first transmission data is transmitted from the first transmission / reception device 1, mutual identification data can be confirmed and the spread spectrum transmission / reception frequency between the transmission / reception devices can be matched with high accuracy. Can be done. Also in this case, by making the pilot carrier period at the time of the initial synchronization longer than the pilot carrier period at the time of the normal reception, it is possible to achieve synchronization acquisition of spread spectrum during the pilot carrier period of the initial synchronization.

In FIG. 1, first and second transmitting / receiving apparatuses 1
And 23, as shown in FIG.
Data transmission / reception is performed using the number of channels. In the first transmitting / receiving apparatus 1, the transmission and reception RF frequencies ftn of the transmitting / receiving apparatus are changed by changing the local oscillation signal of the frequency synthesizer circuit 4 according to each channel in accordance with an instruction of the microcomputer 21. For example, when using channel CH1, transmit and receive RF
The microcomputer 21 controls the frequency synthesizer circuit 4 so that the frequency is ft1 and the transmission and reception RF frequencies are ft9 when the channel CH9 is used.
Control. In the second transmitting / receiving device 23 as well, the transmission and reception RF frequencies ftn are changed in the same manner as described above. However, the change of the transmission / reception RF frequency ftn is performed in synchronization with the first and second transmission / reception devices.

In the same frequency band where various types of modulation / demodulation schemes can be used, the situation where the spread spectrum system of FIG. 1 and the modulation / demodulation scheme using a narrow band such as the SSB (Single Side Bnad) modulation scheme are shared. May exist. In this situation, when the channel CHn is used, the narrow-band modulation signal level becomes higher than that of the spread spectrum signal as shown in FIG. 4, so that transmission / reception data of the spread spectrum method cannot be transmitted accurately. In order to prevent such a situation, it is desired to detect whether or not the channel is an empty channel before starting normal reception.

In FIG. 1, the output signal of the receiving mixer 5 is level-detected by a narrow-band level detector 22. At this time, since the level detection circuit 22 has a narrow frequency band as shown by the dotted line in FIG. 4, only the narrow band signal indicated by the arrow in FIG. 4 is level detected. The signal obtained by the level detection is compared with a reference voltage Vref in the level detection circuit 22. If a narrow band signal is present in the selected channel, the detection signal level is higher than the reference voltage Vref, so that the detection signal a is applied to the microcomputer 21 from the narrow band level detection signal. If no narrow band signal exists, no detection signal a is generated.

If the channel selected by the detection signal a is not an empty channel, the channel is changed to an empty channel by the following method. As shown in FIG. 4A, a control channel is provided in addition to the channels CH1 to CH10 for transmission and reception, and a plurality of pairs of transmission / reception devices are in a data waiting state via the control channel. If one transmitting / receiving apparatus is going to perform transmission, the transmitting / receiving apparatus searches channels CH1 to CH10 once and searches for an empty channel before starting transmission. First, the transmitting and receiving device is channel C
H1 is selected to enter the data receiving state, and the output level of the narrow band level detection circuit is checked. When the output level is lower than the predetermined level, the channel CH1 is stored as an empty channel and the next channel is selected, and when the output level is higher than the predetermined level, the next channel is selected. An empty channel is searched for by repeating the above operation. When searching for a free channel, the transmitting / receiving device transmits transmission data including channel information of the change destination and identification data among the free channels via the control channel. Then, among a plurality of pairs of transmitting / receiving apparatuses, a pair of transmitting / receiving apparatuses having the same identification data enters the initial synchronization. The transmitting / receiving apparatus that has received the first transmission data checks the channel information of the vacant channel during the initial synchronization, and when the initial synchronization ends, the pair of transmitting / receiving apparatuses changes the channel based on the channel information. When the channel change is completed, the pair of transmission / reception devices enters a normal reception state.

Also, other methods can be used for transmission / reception on an empty channel. During a normal transmission / reception operation, a pair of transmission / reception devices having the same identification data transmit / receive data to / from each other, and each transmission / reception device becomes idle according to a detection signal of the narrow band level detection circuit in a data reception state. It detects whether it is a channel or not. If a narrowband signal exists in the selected channel, the narrowband signal is detected by both transmitting and receiving devices. Therefore, the pair of transmitting and receiving devices is configured to transmit and receive RF signals.
The frequency is changed to select the next channel according to a predetermined order. When the change to another channel is completed, the initial synchronization and the detection of an empty channel in that channel are performed again. If the channel is an empty channel, the pair of transmitting / receiving apparatuses directly enter the normal receiving state.

As described above, when a spread spectrum signal and a narrow band signal are mixed, an empty channel can be automatically detected and moved to an empty channel. Although the first and second transmitting / receiving apparatuses 1 and 23 are the slave unit and the base unit of the cordless telephone apparatus, respectively, the invention is not limited thereto, and the invention of FIG. 1 may be applied to the mobile station and the base station of the wireless transmitting / receiving apparatus. Can be.

[0037]

According to the present invention, transmission data composed of a pilot carrier for synchronization acquisition of a spread spectrum system and a communication carrier containing data is transmitted, so that a spectrum that takes a long time to acquire synchronization is transmitted. Even if a spread demodulation circuit is used, there is an effect that bidirectional communication can be favorably performed in a time division manner.

[Brief description of the drawings]

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

FIG. 2 is a timing chart illustrating the operation of the circuit of FIG. 1;

FIG. 3 is a diagram illustrating a data configuration during normal reception.

FIG. 4 is a characteristic diagram showing channels for each frequency in FIG.

FIG. 5 is a block diagram illustrating the concept of two-way communication.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st transmission / reception apparatus 3 RF receiving amplifier 4 Frequency synthesizer circuit 5 Receiving mixing circuit 6 Spread spectrum demodulation circuit 7 Digital demodulation circuit 8 TDD control circuit 9 Data encoding / decoding circuit 10 D / A conversion circuit 11 Output audio amplifier 14 Input Audio amplifier 15 A / D conversion circuit 16 Digital modulation circuit 17 Spread spectrum modulation circuit 18 Mixing circuit for transmission 19 Transmission RF amplifier 21 Microcomputer 22 Narrow band detection circuit 23 Second transceiver

Claims (7)

[Claims] 1. A two-way communication device for performing two-way communication of a signal modulated by a spread spectrum method using a plurality of communication channels between the first and second transmitting and receiving devices. At least one of the transmission / reception devices includes a level detection circuit that detects whether a reception level of transmission data is higher than a predetermined value, and determines whether a currently used channel is an empty channel based on an output signal of the level detection circuit. A bidirectional transmitting / receiving apparatus, comprising: 2. When the reception level is lower than a predetermined value,
2. The bidirectional transmitting / receiving apparatus according to claim 1, wherein the first and second transmitting / receiving apparatuses perform normal reception as idle channels. 3. When the reception level is higher than a predetermined value,
3. The bidirectional transceiver according to claim 2, wherein the first and second transceivers shift to another channel. 4. The control circuit on the transmitting side of the first and second transmitting / receiving devices includes a unit for sweeping a communication channel, a unit for detecting an empty channel for each channel, and a transmission including at least identification data and empty channel information. 2. A transmitting device for transmitting data.
A two-way transmitting / receiving device according to claim 1. 5. A control circuit of a transmission / reception apparatus on the receiving side, comprising: a determination unit configured to determine whether identification data matches; and, if the identification data matches, a channel shift to an empty channel based on the idle channel information. 5. The two-way transmitting / receiving apparatus according to claim 4, further comprising means for performing. 6. The two-way transmission / reception apparatus according to claim 4, wherein transmission / reception of the transmission data is performed by providing a control channel among the plurality of communication channels. 7. The two-way transmission / reception apparatus according to claim 6, wherein the first and second transmission / reception apparatuses simultaneously move to a free channel based on the free channel information.