JP2598634Y2 - Spread spectrum communication equipment - Google Patents

Description

[Detailed description of the invention]

[0001]

The present invention transmits a signal in which a PN code is switched at a constant time period as a preamble signal,
The present invention relates to a spread spectrum communication device that receives this preamble signal and performs initial synchronization of a PN code.

[0002]

2. Description of the Related Art A spread spectrum (SS) communication device generates a plurality of PN (pseudo-noise) codes having different phases and generates each PN code.
A transmitting unit that transmits a signal (spread-modulated signal) whose code is switched at a fixed time period as a preamble signal for initial synchronization, and a receiving unit that receives this preamble signal and performs initial synchronization of each PN code. Have. In order to perform the initial synchronization in this receiving unit, after the correlation demodulation of the preamble signal is performed, the generation timing of the correlation pulse is detected.
The generation cycle changes for each cycle in which the phase of the N code changes.
Therefore, by detecting such a correlation pulse whose generation period changes, the initial synchronization of the PN code is performed, and an advantage peculiar to the SS communication apparatus that the influence of the interference signal is eliminated can be obtained.

FIGS. 5 and 6 are block diagrams showing the constructions of a transmission section and a reception section of a conventional SS communication apparatus, respectively.
Code generating circuit, 34 is a mixing circuit, 35 is an RF carrier generating circuit, 36 is a mixing circuit, 37 is a band-pass filter,
38 is an amplification circuit, 39 is a transmission antenna, 41 is a reception antenna, 42 is a band-pass filter, 43 is an amplification circuit,
4 is a local carrier generation circuit, 45 is a mixing circuit, 46
Is a band pass filter, 47 is an amplifying circuit, 48 is a correlation circuit, 49 is an intermediate frequency carrier generation circuit, 50 is a mixing circuit, 55 is a PN code generation circuit, and 56 is a data demodulation circuit. In such a conventional SS communication device, a PN
The code is generated in the same phase and transmitted as a preamble signal.
Initial synchronization of code is performed. In this case, in the correlation demodulation output, the discrimination between the desired SS signal and the interference signal is performed using the difference between the periodicity of the correlation pulse and the correlation output level.

FIG. 7 illustrates this situation.
Is a correlation output of a desired SS signal in which a large level appears at a fixed period, (b) is a correlation output of an interference signal in which a small level appears irregularly (no periodicity), and (c) is a combination of (a) and (b). By using the difference between the periodicity of the correlation pulse and the correlation output level as described above in the actual correlation output obtained by the above, the pulse position of the desired SS signal can be specified, so that both signals can be easily identified. it can. Note that FIG.
Shows an example of a data format.

[0005]

In the conventional spread spectrum communication apparatus, when discriminating a desired SS signal from an interference signal, a peak level is large and a peak periodically occurs in a correlation output depending on the interference signal. Since the desired SS signal and the interference signal cannot be clearly distinguished from each other, there is a problem that initial synchronization failure of the PN code occurs. FIG. 8 illustrates this situation.
(A) is a correlation output of a desired SS signal in which a large level appears at a constant cycle, (b) is a correlation output of an interference signal having a large peak level and a peak is periodically generated, and (c) is a correlation output of (a). In the actual correlation output obtained by combining (b), the peak level of the interference signal in (b) is large and the peak occurs periodically, so that the pulse position of the desired SS signal cannot be specified. Can not be identified.

The present invention has been made in view of the above-described problems. Even when the peak level of the interference signal is large and the peaks are generated periodically, the P signal caused by the interference signal is reduced.
It is an object of the present invention to provide a spread spectrum communication device capable of reducing initial synchronization failure of N signals.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a transmitter having a generator for generating a plurality of PN codes having different phases and a code selector for switching each PN code at a fixed time period. A plurality of correlation output detection circuits provided corresponding to the plurality of PN codes, and a receiving unit having an initial synchronization determination circuit for performing initial synchronization of the PN codes based on the outputs of the respective correlation output detection circuits. It is characterized by the following.

[0008]

According to the structure of the present invention, a transmitting section generates a plurality of PN codes having different phases and transmits a signal obtained by switching each PN code at a fixed time period as a preamble signal. Correlation outputs are detected by a plurality of correlation output detection circuits provided corresponding to the PN codes, and initial synchronization of each PN code is performed based on the output of each correlation output detection circuit. As a result, even when the peak level of the interference signal is large and the peak occurs periodically, it is possible to reduce the initial synchronization failure of the PN code due to the interference signal.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 and 2 are block diagrams showing an embodiment of a spread spectrum communication apparatus according to the present invention, showing a transmitting unit and a receiving unit, respectively. In this embodiment, as an example, two PNs are used.
Codes PN1 and PN2 are generated with different phases.
A case will be described in which codes are switched at regular time intervals and transmitted as a preamble signal for initial synchronization. In FIG. 1, reference numeral 1 denotes a circuit for generating a first PN code PN1;
Is a circuit for generating a second PN code PN2 having a phase different from PN1 (for example, a phase shift of 周期 cycle), and 3 is a code (code) for switching the first PN code PN1 and the second PN code PN2 at a constant time period. A selection circuit 4 is a mixing circuit for mixing digital data and PN1 or PN2, and 5 is an RF
A carrier generation circuit, 6 is a mixing circuit, 7 is a bandpass filter, 8 is an amplification circuit, and 9 is a transmission antenna.

On the other hand, in FIG. 2, 11 is a receiving antenna, 12 is a bandpass filter, 13 is an amplifying circuit, 14
Is a local carrier generation circuit, 15 is a mixing circuit, 16 is a band pass filter, and 17 is an amplification circuit. Also, 1
Reference numeral 8 denotes a correlator composed of a SAW (surface acoustic wave) convolver, 19 denotes an intermediate frequency carrier generation circuit, 20 denotes a mixing circuit, 21 denotes a detection circuit, 22 denotes a correlation output detection circuit for the first PN code PN1, 23 Is the second PN code PN2
, A correlation output detection circuit 24 for each of the detection circuits 22, 2
Reference numeral 25 denotes an initial synchronization determination circuit for performing initial synchronization of a PN code based on the output of 3, a reference numeral 25 denotes a PN code generation circuit, and a reference numeral 26 denotes a data demodulation circuit.

Next, the operation of the spread spectrum communication apparatus according to this embodiment will be described. The first PN code PN1 generated by the first PN code PN1 generation circuit 1 of the transmission unit, and the second PN code PN2 generation circuit so that the phase differs from this PN1 by, for example, a half cycle phase shift. 2nd generated in 2
The PN code PN2 is switched at a fixed time period by the code selection circuit 3 and mixed with digital data by the mixing circuit 4, and then transmitted through the mixing circuit 6, the band-pass filter 7, and the amplification circuit 8 to the transmission antenna 9 Is transmitted as a preamble signal. Here, the code switching by the code selection circuit 3 is performed, for example, as shown in (a) or (b) of FIG. This preamble signal is received by the receiving antenna 11 of the receiving unit, and the bandpass filter 12
Amplifying circuit 13, mixing circuit 15, bandpass filter 1
6. The signal is input to the correlator 18 via the amplifying circuit 17, is correlated by the correlator 18, and is detected by the detection circuit 21.

Subsequently, the output of the detection circuit 21 is input to each of the correlation output detection circuits 22 and 23, and the correlation output is detected. First, for the first PN code PN1, the correlation output of the desired SS signal as shown in FIG. 4A is detected by the correlation output detection circuit 22 for PN1. Similarly, for the second PN code PN2, the correlation output of the desired SS signal as shown in FIG. 4B is detected by the correlation output detection circuit 23 for PN2. 4A output from the correlation output detection circuits 22 and 23,
The correlation output of (b) is input to the initial synchronization determination circuit 24 to perform initial synchronization. Next, based on the output of the initial synchronization determination circuit 24, the data demodulation circuit 26
Digital data will be demodulated.

As described above, according to this embodiment, the first PN code PN1 and the second PN code PN1 having different phases in the transmitting unit.
Codes PN2 are generated by generating circuits 1 and 2, respectively, and a signal in which each of the PN codes PN1 and PN2 are switched at a fixed time period by a code selecting circuit 3 is transmitted as a preamble signal, and received by a receiving unit to each of the PN codes PN1 and PN2. Since the correlation output of the desired SS signal is detected by the correlation output detection circuits 22 and 23 provided correspondingly, and the initial synchronization is performed by the initial synchronization determination circuit 24 based on each correlation output, the conventional diagram is used. As shown in FIG. 8B, the presence of an interference signal having a large peak level and periodically generating peaks causes PN1
Even if the correlation output for PN1 deteriorates, the correlation output for PN2 having a different generation period from PN1 is hardly affected by the interference signal, so that the correlation output of the desired SS signal and the correlation output for the interference signal can be distinguished. Become. As a result, even when the peak level of the interference signal is large and the peak occurs periodically, it is possible to reduce the initial synchronization failure of the PN code due to the interference signal.

In this embodiment, a case has been described in which two PN codes having different phases, PN1 and PN2, are used. However, the present invention is not limited to this, and the same applies when three or more PN codes are used. be able to. In this case, the reception unit is provided with a number of correlation output detection circuits corresponding to the PN code.

[0015]

As described above, according to the present invention, a plurality of PN codes having different phases are generated in the transmitting section, and each PN code is generated.
A signal whose code is switched at a fixed time period is transmitted as a preamble signal, and a correlation output detection circuit provided corresponding to each PN code is detected in a receiving unit so that a correlation output of a desired SS signal is detected. Since the initial synchronization is performed based on this, even when the peak level of the interference signal is large and the peak occurs periodically, it is possible to reduce the initial synchronization failure of the PN code due to the interference signal.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a transmission unit of a spread spectrum communication device according to the present invention.

FIG. 2 is a block diagram illustrating a configuration of a receiving unit of the spread spectrum communication device according to the present invention.

FIG. 3 is an explanatory diagram of an example of code switching in a transmission unit of the spread spectrum communication device according to the present invention.

FIG. 4 is a waveform diagram of the correlation output of each PN code obtained in the spread spectrum receiving section of the present invention.

FIG. 5 is a block diagram illustrating a configuration of a transmission unit of a conventional spread spectrum communication device.

FIG. 6 is a block diagram showing a configuration of a receiving section of a conventional spread spectrum communication device.

FIG. 7 is a waveform diagram illustrating a method of identifying a desired SS signal and an interference signal in a spread spectrum communication apparatus.

FIG. 8 shows a desired S in a conventional spread spectrum communication apparatus.
FIG. 4 is a waveform diagram illustrating a method for identifying an S signal and an interference signal.

FIG. 9 is an example of a data format in a conventional spread spectrum communication device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 first PN code generation circuit 2 second PN code generation circuit 3 code selection circuit 18 correlator 21 detection circuit 22 correlation output detection circuit for PN1 23 correlation output detection circuit for PN2 24 initial synchronization determination circuit

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-3-167930 (JP, A) JP-A-56-31246 (JP, A) JP-A-63-84218 (JP, A) JP-A-4- 79438 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) H04B 1/707 H04L 7/10

Claims (1)

(57) [Scope of request for utility model registration] 1. A transmitting section having a generating circuit for generating a plurality of PN codes having different phases and a code selecting circuit for switching each PN code at a fixed time period, and a plurality of correlations provided corresponding to the plurality of PN codes. A spread spectrum communication apparatus comprising: an output detection circuit; and a receiving unit having an initial synchronization determination circuit that performs initial synchronization of the PN code based on the output of each correlation output detection circuit.