JPH09261131A - Spread spectrum communication method and equipment using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the method and equipment to improve the availability of frequency in spread spectrum communication. SOLUTION: The communication method includes a coding circuit 2 providing an output of primary modulation information of data, a spread control circuit 4 conducting spread control to provide an output of secondary modulation information, a frequency synthesizer 6 controlling a frequency/phase through the synthesis of modulation information to provide an output of a transmission base band signal, a carrier oscillator 8 outputting a carrier, and a mixer 10 mixing the carrier and the transmission base band signal to output a spread spectrum signal. The carrier is subjected to n/m frequency division and the result is given to a frequency synthesizer 6 as an operation reference clock. The hopping period is set to be an integer multiple of the period of the carrier and a carrier component among phases in the spread spectrum signal at a start timing of each hopping period is made known.

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 method and device. The present invention particularly relates to improvement of a spread spectrum communication method and apparatus applicable to a frequency hopping system.

[0002]

2. Description of the Related Art Spread spectrum communication is a communication method in which a signal is spread over a band wider than the frequency bandwidth of data to be transmitted and transmitted, and is resistant to interference, has signal confidentiality, and has high resolution measurement. It has the advantage that it can be distanced. Spread spectrum communication has been applied to fields such as satellite communication and land communication, and in recent years, it has been applied to mobile communication and local communication.

[0003] Typical methods for realizing spread spectrum communication include a direct sequence (DS) method and a frequency hopping (FH) method. The DS method spreads the occupied frequency band by performing balanced modulation on the modulated data using spread code pulses. On the other hand, the FH method uses a wide occupied frequency band by switching (that is, hopping) the carrier frequency of the modulated data according to the spread code pulse.

In the normal FH system, FSK is used for data modulation.
(Frequency Shift Keying)
Is used. That is, the data to be transmitted is converted into a code word every several bits, and the frequency is shifted according to the code word chips forming the code word. FIG. 6 is a diagram showing a relationship between a bit string of data and a code word to be converted. As shown in the figure, here, every three bits of input data are converted into any one of eight codewords. For example, when the input data is “000”, this is the code word “7-6-5-2-4-1-
Converted to 3 ". “0” to “7” forming the codeword are called codeword chips, and “000” to “11” are set on the receiving side.
The arrangement of the code word chips is devised within each code word so that the "1" data can be sorted.

Different frequencies are assigned to each codeword chip. For example, frequencies f0 to f7 are associated with codeword chips "0" to "7". When sending "000", the code word "7-6-5-2-4-1-3" must be converted to "f
The frequency is switched in the order of "7, f6, f5, f2, f4, f1, f3". Since eight frequencies are used, the modulation in this case can be called 8-level MFSK (Multilevel FSK) modulation. Hereinafter, data modulation (modulation not related to frequency hopping) is referred to as primary modulation.

[0006] On the other hand, frequency hopping of a carrier wave is performed in accordance with a spread code sequence for frequency hopping modulation (pulse train of a pseudo-noise code, hereinafter also referred to simply as "code sequence"). If the number of codeword chips included in this code sequence is 31, 31 different frequencies are selected as hopping frequencies within a frequency band that is allowed to be used for communication (the frequency hopping itself also has a broad meaning. However, in this specification, the term FSK refers to only primary modulation. The cycle in which the code sequence makes one round is called the code cycle, and the cycle at which the hopping frequency switches (1/31 of the code cycle in this example) is called the hopping cycle. The switching of the hopping frequency and the frequency switching by the primary modulation are performed in synchronization.

The FH-MFSK system has been introduced in various documents as a combination having a higher affinity than before. As a typical example, DJ Goodman et al. "Frequency-Hopped Multi"
level FSK for Mobile Radio '' The Bell System Techn
ical Journal, Vol.59 No.7p1257 ~ 1275, 1980. Furthermore, M-ary FSK (M is an improvement of MFSK.
The combination method of FSK and FH is described in Eimatsu Moriyama et al. "Outline and basic characteristics of communication experimental equipment for land mobile frequency hopping method" Radio Research Institute Quarterly Report Vol.32, No.164 p165-177, 198
It is described in 6.

[0008]

According to the FH-MFSK system, the data transmission rate can be increased by increasing the types of frequencies to be prepared for MFSK (that is, the number of levels in multilevel). Can be raised. However, increasing the number of levels means increasing the frequency bandwidth used in MFSK. Today, various communication devices use various frequency bands, and the frequency bands permitted to be used by each communication method and each communication device are regulated by the Radio Law, Radio Equipment Regulations and the like. FH-
In the case of the spread spectrum communication of the MFSK system, as the specific low power data communication, 26 of 2471 to 2497 MHz is used.
Use of the MHz band is permitted. If the frequency utilization efficiency can be improved by a method other than increasing the number of levels in MFSK, its significance will be great. An object of the present invention is to provide a method and an apparatus for improving frequency utilization efficiency in spread spectrum communication.

[0009]

[Means for Solving the Problems]

(1) The spread spectrum communication method of the present invention is a method of coding data to generate primary modulation information, generating secondary modulation information by spread control, and generating a spread spectrum signal based on these modulation information. A modulation method including at least a phase shift is used as the primary modulation, and the spread spectrum signal is generated in a state where the phase of the spread spectrum signal can be independently determined for each demodulation unit period.

Here, the "demodulation unit period" is a unit period for demodulating an information unit such as a codeword chip, and is also a modulation unit period. The hopping period is an example. “Independently” means that it is not necessary to refer to the phase at the end of the immediately preceding demodulation unit period, and is meant to be distinguished from the method such as differential PSK.

According to this aspect, the input data is first encoded to generate the primary modulation information. This information includes phase shift information. Other than this, information such as frequency deviation information may be added. On the other hand, the secondary modulation information is generated by the spread control. This corresponds to frequency hopping information. Then, a spread spectrum signal is generated based on these modulation information. However, the phase of the signal is characterized in that it is generated in a state where it can be determined independently for each demodulation unit period.

(2) In one aspect of the present invention, the phase of the spread spectrum signal is controlled so as to be determined at a predetermined timing of each demodulation unit period, so that the phase of the signal is adjusted to each demodulation unit. It is possible to judge independently by the period. "Determining" means knowing (calculating)
This means that the phase is always controlled to be 0 ° or 180 ° at the predetermined timing.

(3) At this time, the predetermined timing may be the start timing of each demodulation unit period.

In cases (4) and (3), an aspect of the present invention is a method for generating the spread spectrum signal by mixing the fixed-frequency carrier after performing the primary modulation and the secondary modulation. , The phase control is performed so that the demodulation unit period is set to an integral multiple of the period of the carrier wave and the phase of the spread spectrum signal at the start timing of each demodulation unit period can be determined due to the primary modulation and the secondary modulation. To do.

That is, in this aspect, rather than hopping the final carrier frequency, the process for realizing frequency hopping is performed by secondary modulation, and the frequency of the carrier itself is fixed. However, since the carriers are mixed to form a spread spectrum signal, the influence of the secondary modulation is naturally added to the spread spectrum signal. Therefore, this aspect may be considered to be included in the FH scheme, or spread spectrum communication performed under a name other than the FH scheme may be applied to this aspect.

In this aspect, the demodulation unit period is an integral multiple of the carrier cycle. Therefore, when the carriers are mixed, the components due to the carriers themselves are constant and known among the phases that the spread spectrum signal has at the start timing of each demodulation unit period. On the other hand, the phases of the components resulting from the primary modulation and the secondary modulation are controlled so that they can be determined at the same timing. As a result, it is possible to add a meaningful phase shift at the start timing of each demodulation unit period and demodulate this. For this reason, phase determination like differential PSK is unnecessary.

(5) Another aspect of the present invention is to encode data to be transmitted, and to generate primary modulation information based on the encoded data by a modulation method including at least a phase deviation. A step, a step of generating secondary modulation information by spreading control according to a spreading code sequence for frequency hopping, a step of determining the frequency and phase by combining the primary modulation information and the secondary modulation information, and the determined frequency and phase In order to realize the above, a step of performing primary modulation and secondary modulation integrally to generate a transmission baseband signal, and a carrier whose phase is independently recognizable in each hopping cycle are mixed with the transmission baseband signal. And generating a spread spectrum signal.

Examples of modulation methods including phase shift include PSK and a mixed method of FSK and PSK. In this aspect, the data to be transmitted is first encoded, and the primary modulation information by the modulation method including at least the phase deviation is generated according to the result. At this stage, only information about the primary modulation (for example, frequency and phase) is generated, and the primary modulation is not actually performed.

Subsequently, the secondary modulation information is similarly generated by the spread control. These two pieces of modulation information are combined to determine the frequency and phase. As an example of synthesis,
It is conceivable to simply sum the specified values of the frequencies that come from the two pieces of modulation information. Next, the primary modulation and the secondary modulation are integrally performed so as to realize the frequency and the phase thus determined, and the transmission baseband signal is generated. "Integrally" means that it is no longer necessary to distinguish between primary and secondary modulation by referring to the above-mentioned comprehensive result.

Thereafter, the carrier wave is mixed with the transmission baseband signal to generate a spread spectrum signal. At this time, the phase of the carrier wave is in a state where it can be recognized independently in each hopping cycle. Considering that the relationship between the carrier wave and the hopping cycle is naturally maintained on the receiving side as well, 1. 1. The phase of the carrier wave can be recognized. Information regarding the phase modulation can be demodulated on the receiving side by the two points that the carrier wave and the received spread spectrum signal have a certain synchronization relationship.

(6) At this time, in an aspect of the present invention,
The hopping period is an integral multiple of the carrier period. The significance of this is as described in (4).

(7) On the other hand, the spread spectrum communication apparatus of the present invention encodes the data to be transmitted and generates the primary modulation information by the modulation method including at least the phase shift, and the spread code for frequency hopping. A spread control circuit that generates secondary modulation information by sequence-based spreading control, and a frequency synthesizer that collectively performs primary modulation and secondary modulation by combining primary modulation information and secondary modulation information, and generates a transmission baseband signal. And a mixer for generating a spread spectrum signal by mixing a carrier wave with the transmission baseband signal, and giving a signal obtained by dividing the carrier wave as an operation reference clock of the frequency synthesizer. This aspect corresponds to the main part of the transmission block in the spread spectrum communication device.

In this aspect, since the primary modulation information and the secondary modulation information are integrated at the information stage, the primary modulation and the secondary modulation can be collectively performed by the frequency synthesizer. Also, since the signal obtained by dividing the carrier wave serves as the operation reference clock of the frequency synthesizer, the hopping cycle can be determined from this clock.

(8) At this time, in one aspect of the present invention, the frequency synthesizer generates the hopping cycle at an integral multiple of the cycle of the operation reference clock. Therefore, the same effect as (6) is obtained.

(9) Another aspect of the present invention is that the secondary modulation information is obtained by a first mixer for removing a carrier frequency component by mixing a carrier with the received spread spectrum signal and spreading control according to a spreading code sequence for frequency hopping. , A frequency synthesizer that generates a baseband signal based on the secondary modulation information, and a second mixer that removes the secondary modulation component by mixing the output signal of the first mixer and the output signal of the frequency synthesizer. A two-mixer, a demodulation circuit that demodulates the output signal of the second mixer to extract primary modulation information, and a decoding circuit that decodes data from the extracted primary modulation information, and divides the carrier wave. The obtained signal is given as the operation reference clock of the frequency synthesizer. This aspect corresponds to the main part of the reception block in the spread spectrum communication device.

According to this aspect, first, the carrier is mixed with the received spread spectrum signal to remove the carrier frequency component. On the other hand, the spread control circuit generates secondary modulation information, and the frequency synthesizer generates a baseband signal based on this information. Subsequently, the output signal of the first mixer and the output signal of the frequency synthesizer are mixed, and the secondary modulation component is removed. Thereafter, the demodulation circuit demodulates the output signal of the second mixer to extract the primary modulation information, and the data is decoded from this information. Also in this aspect, as in (7), the frequency-divided signal of the carrier wave serves as the operation reference clock of the frequency synthesizer.

In the cases of (10) and (9), in one aspect of the present invention, the frequency synthesizer generates the hopping cycle at an integral multiple of the cycle of the operation reference clock. The function and effect of this are the same as in (4). Further, in this aspect, the demodulation circuit extracts at least phase deviation information as primary modulation information. (4) Since the same effect can be obtained,
This is because meaningful phase deviation information can be obtained.

(11) At this time, in one embodiment of the present invention,
The demodulation circuit handles the phase shift information as independent information for each hopping cycle. That is, it is possible to independently extract meaningful phase deviation information for each hopping cycle by the same effect as (4). This also eliminates the need for a modulation method such as differential PSK.

(12) In one aspect of the present invention, the transmission block or the reception block further includes a voltage-controlled oscillator that outputs an operation reference clock, and 1 / m that divides the carrier wave by m.
Input a frequency divider, a 1 / n frequency divider that divides the operation reference clock by n, and a signal divided by these frequency dividers,
A PLL control circuit that controls the voltage controlled oscillator so that the frequency ratio of the carrier wave to the operation clock becomes m: n.

In this mode, the frequency division ratio m: n is first determined by the two frequency dividers, and then the voltage controlled oscillator is controlled by the PLL control circuit so as to realize this ratio.
Therefore, finally, the frequency of the carrier wave becomes m / n times the frequency of the operation reference clock.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described with reference to the drawings as appropriate. In the first embodiment, the entire transmission block of the spread spectrum communication device is used in the second embodiment.
The entire reception block will be described below. Through the explanation of these devices, the contents of the spread spectrum communication method of the present invention will be clarified.

These embodiments are based on conventional FH-MFS.
In addition to the K system, the PSK system is added to the primary modulation. In the FH method, the frequency is switched for each hopping cycle, so that it is difficult to combine the FH method with the PSK method that sees the change in phase. This is because it is impossible to predict how the phase will change as the frequency is switched.

The PSK system is widely used in ordinary narrow band communication (that is, communication in which the carrier frequency is stable). A general phase determination method is found in a method called differential PSK, and detects a relative change in the phase at the end timing of the immediately preceding demodulation unit period and the phase at the start timing of the current demodulation unit period. Conversely speaking, the minimum information is transmitted only by the presence or absence of relative change,
Even in various textbooks and the like, it is difficult to obtain an absolute phase for each demodulation unit period in the PSK method, and its significance is weak. Under this circumstance, the present embodiment intends to fundamentally improve the frequency utilization efficiency by incorporating PSK into FH spread spectrum communication and determining the absolute phase thereof.

Embodiment 1. In the present embodiment, when the FH method is realized, the final carrier frequency is not directly hopped, but a process corresponding to frequency hopping is performed by a modulation called secondary modulation. The frequency of the carrier wave itself is fixed.

[Configuration] FIG. 1 is a configuration diagram of a spread spectrum communication apparatus (transmission block) according to the present embodiment. As shown in the figure, the transmission block inputs data to be transmitted, converts it into a code word in units of several bits, and outputs primary modulation information. Spreading control circuit 4 which outputs modulation information, frequency synthesizer 6 which controls the frequency and phase according to the total result of primary modulation information and secondary modulation information, and outputs transmission baseband signal fS1, and which outputs carrier wave at fixed frequency fH Carrier oscillator 8, a mixer 10 that mixes a carrier wave and a transmission baseband signal fS1 and outputs a spread spectrum signal, a transmission circuit 12 that power-amplifies the output signal of the mixer 10, and an antenna that transmits the amplified spread spectrum signal. Including 14.

The frequency synthesizer 6 receives the primary modulation information and the secondary modulation information, controls the frequency and the phase,
DDS (Direct Digit) that outputs discrete digital waveforms
al Synthsizer) 600, DDS600 output D / A
It includes a D / A conversion unit 602 for conversion and an LPF (Low Pass Filter) 604 for shaping a waveform obtained as a result of D / A conversion. The DDS 600 includes a phase calculator (not shown) and a sine wave lookup table. The primary modulation includes two types of information, frequency modulation information and phase modulation information. As a DDS that outputs a desired waveform according to these two types of information, for example, a dual direct digital synthesizer Q2334 manufactured by Qualcomm, Inc. 16-bit numerical control oscillator HSP451 manufactured by Harris Corp.
06 and the like can be used.

The operation reference clock (frequency fL) of the frequency synthesizer is a VCO (Voltage controlled Oscilla).
tor: voltage controlled oscillator) 16. VCO1
The output frequency of 6 is 1 / m frequency divider 18 and 1 / n frequency divider 2
0 and a PLL (Phase Lock Loop) control circuit 22 are controlled in cooperation. The 1 / m frequency divider 18 inputs a carrier wave (frequency fH) and divides it by m. The 1 / n frequency divider 20 inputs the operation reference clock and divides it by n.
The PLL control circuit 22 refers to the outputs of the two frequency dividers and operates the control voltage of the VCO 16 so that the relationship of fL: fH = n: m (Equation 1) is maintained. Here, suppose fH is 2471 MHz and fL is 33 M.
Assume less than Hz. The latter reason is based on the general maximum operating frequency of the frequency synthesizer 6 and its peripheral circuits. In this case, since 2471/33 = 74.88, Formula 1 is determined as fL: fH = 1: 75 (Formula 2) in this embodiment. As shown in Expression 2, when n = 1, the 1 / n frequency divider 20 is not necessary, but the frequency division ratio of the high frequency frequency divider often has a fixed value. A frequency divider that satisfies Equation 2 is selected from the allowable values.

In this embodiment, not only MFSK but P
Primary modulation is also performed using SK. The frequency modulation range by MFSK is 0.8 MHz, and the modulation is 4 levels. Specifically, the frequencies selected by the MFSK of the primary modulation are four types of 0.2, 0.4, 0.6, and 0.8 MHz. These are denoted as f ^{(1) to} f ⁽⁴⁾ , respectively. On the other hand, the PSK modulation has two levels, and the phase (initial phase) has two types of 0 and 180 °. These are denoted as φ ⁽¹⁾ and φ ⁽²⁾ , respectively.

FIG. 2 is a diagram showing a relationship between a combination of frequencies f ^{(1) to} f ⁽⁴⁾ and phases φ ⁽¹⁾ and φ ⁽²⁾ and codeword chips. As shown in the figure, for example, the code word chip "0" is expressed by a combination of f ⁽¹⁾ φ ⁽¹⁾ . Encoding circuit 2
The primary modulation information given from the to the frequency synthesizer 6 indicates any one of these eight types. Similar to FIG. 6, for example, when transmitting “000”, the code word “7-6-5-2-
4-1-3 ”, f ⁽⁴⁾ φ ⁽²⁾ → f ⁽⁴⁾ φ ⁽¹⁾ → f
⁽³⁾ φ ⁽²⁾ → f ⁽²⁾ φ ⁽¹⁾ → f ⁽³⁾ φ ⁽¹⁾ → f ^{(1 )} φ
⁽²⁾ → f ⁽²⁾ φ ⁽²⁾ is modulated over 7 hopping cycles. In this way, the frequency utilization efficiency is improved by the mixed modulation method of MFSK and PSK. Here, P
Since SK has two levels, frequency utilization efficiency is doubled. Hereinafter, in a certain hopping cycle Hi, the frequency and the initial phase selected by the primary modulation will be described as fi and φi, respectively.

On the other hand, the frequency modulation range by frequency hopping of the secondary modulation is 25 MHz. The number of codeword chips included in the code sequence may be 31, for example. The secondary modulation information given from the spreading control circuit 4 to the frequency synthesizer 6 indicates any one of these 31 ways. In the hopping cycle Hi, the frequency selected by the secondary modulation is f ′.
Notated as i.

[Operation] Encoding processing by the encoding circuit 2,
The basics of the diffusion control by the diffusion control circuit 4 are as described in the conventional art. However, the difference here is that both outputs are used as primary and secondary modulation information, respectively.

In the DDS 600, the frequency synthesizer 6 first combines these two pieces of modulation information. The synthesis is performed by taking the algebraic sum of the two pieces of modulation information. The frequency fb of the transmission baseband signal to be finally output by the frequency synthesizer 6 and the initial phase φb are simply fb = fi + f′i φb = φi. Here, fi is 0.8 MHz or less, and f′i is 2
Since it is 5 MHz or less, the fb obtained by the algebraic sum is 25.8.
Below MHz.

FIG. 3 is a diagram showing a waveform of a signal generated in each part of the frequency synthesizer 6 according to fb and φb. First, FIG. 7A shows the output of the phase calculator in the DDS 600. The phase calculator is based on fb and φb,
The waveform of the transmission baseband signal, which is the final purpose, is sampled and output for each operation reference clock, and the output information is the phase. Here, φb = 0 °. Therefore, at the first sampling timing, the phase is 0 °, which increases uniformly for each operation reference clock. In the figure, 1 of the operation reference clock
The phase of the transmission baseband signal is 0 to 360 in about 3 cycles.
The frequency fb of the transmission baseband signal for one cycle
It was found that was 1/13 of the frequency fL of the operation reference clock.

Subsequently, the amplitude of the sine wave corresponding to each phase is found by referring to the sine wave lookup table using the phase of the transmission baseband signal as an index. FIG. 3B shows the discrete sine wave signal thus obtained. A continuous staircase waveform signal obtained by passing this signal through the D / A converter 602 is shown in FIG. 7C, and a signal obtained by further removing the harmonic component of this staircase waveform signal by the LPF 604. Are shown in (d). In this way, the primary and secondary modulations are completed, and the transmission baseband signal fS1 shown in (d) is output.

Thereafter, the mixer 10 mixes the transmission baseband signal and the carrier. At this point, a spread spectrum signal is generated, which is amplified by the transmission circuit 12,
It is transmitted from the antenna 14.

FIG. 4 is a diagram showing the relationship between the transmission baseband signal, the operation reference clock, the waveform of the carrier wave, and the phase.
In the figure, the transmission baseband signal is 25.8 MHz.
Below, the operation reference clock is about 33 MHz and the carrier is about 2
It is 500 MHz and the carrier frequency is drawn low to aid understanding. Here, the first three codeword chips “7” among the codewords corresponding to the data “000”.
Three hopping periods H1 to H3 corresponding to “6” and “5”
Is shown. 25 MHz for transmitted baseband signals
The effect of the f'i component hopping within is remarkable, and the effect of the fi component varying at 0.8 MHz or less is not apparent at the level of FIG.

The initial phase φb of the transmission baseband signal in each hopping cycle is 0 ° or 180 °. The phase at the end timing of each hopping cycle is f'i
However, in this embodiment, since the initial phase has information based on PSK, the situation at the end timing does not pose a problem. According to the frequency synthesizer 6 of the present embodiment, the initial phase can be accurately set to 0 ° or 180 ° at the start timing of each hopping cycle.
Unlike SK, it is not necessary to compare the phase at the start timing of the current hopping cycle with the phase at the end timing of the immediately preceding hopping cycle. According to the transmission block of this embodiment, the phase related to PSK can be independently set for each hopping cycle.

In the present invention, the hopping cycle is set to an integral multiple of the cycle of the carrier wave in order to ensure the confirmation of the initial phase. In order to realize this condition, in the present embodiment, a multiple relation of Expression 2 is provided between the carrier frequency fH and the frequency fL of the operation reference clock of the frequency synthesizer 6. Since the hopping cycle is determined by counting the operation reference clock in the frequency synthesizer 6, as long as the frequency-divided signal of the carrier is used as the operation reference clock, the hopping cycle is always a multiple of the cycle of the carrier. If this condition is satisfied, the carrier phase will always have the same value (probably 0 ° in FIG. 4) at the start timing of each hopping cycle, so the initial phase will be known even if the carrier is mixed with the transmission baseband signal. . In other words, according to the present embodiment, the spread spectrum signal can be generated in a state where the phase of the spread spectrum signal can be independently determined for each demodulation unit period, that is, for each hopping cycle.

The above is the contents of the present embodiment. It should be noted that the following improvements or modifications can be considered in this embodiment.

(1) In the present embodiment, MFSK has four levels and PSK has two levels, but naturally these may be combinations of any number of levels. If PSK is at the k level, the frequency utilization efficiency will be k times the initial level.

(2) In this embodiment, the MFS is used for the primary modulation.
Although a mixed modulation method of K and PSK is adopted, this may be only PSK on the principle of the present embodiment.

(3) Although the initial phase related to PSK is 0 ° or 180 °, this value can of course be arbitrarily determined.

Embodiment 2. Next, the reception block of the spread spectrum communication device will be described.

[Configuration] FIG. 5 is a configuration diagram of a spread spectrum communication apparatus (reception block) according to the present embodiment. As shown in the figure, the receiving block includes an antenna 30 for receiving a spread spectrum signal, a receiving circuit 32 for amplifying the received signal through a bandpass filter, a carrier wave oscillator 34 for outputting a signal having the same frequency fH as a carrier wave, and the carrier wave oscillator 34 generated here. First mixer 3 for mixing a carrier wave and an output signal of the receiving circuit 32
Holds 6.

On the other hand, like the transmission block, the carrier wave is 1 / m.
The frequency divider 38, the 1 / n frequency divider 40, the PLL control circuit 42, and the VCO 44 frequency-divide by 75 as shown in Equation 2 to generate an operation reference clock of frequency fL. The frequency synthesizer 50 includes a DDS 500, a D / A converter 502,
It has an LPF 504 and operates with an operation reference clock.

The spreading control circuit 52 performs the same spreading control as the transmission block according to the code sequence, and outputs the secondary modulation information. The frequency synthesizer 50 outputs a baseband signal (frequency fS2) obtained by only secondary modulation. This signal is mixed in the second mixer 54 with the output signal of the first mixer 36.

The output signal of the second mixer 54 is given to the synchronization control circuit 56 and the demodulation circuit 58. Synchronous control circuit 56
Synchronizes and holds it, and controls the operation timing of the spread control circuit 52. On the other hand, the demodulation circuit 58 demodulates the output signal of the second mixer 54, and the demodulated signal is decoded by the decoding circuit 60 into the original data.

[Operation] The spread spectrum signal received by the antenna 30 is first down-converted by the first mixer 36. In this reception block, unlike the transmission block, the frequency synthesizer 50 generates a baseband signal by only secondary modulation. Therefore, the secondary modulation component is removed from the output signal of the second mixer 54, and only the primary modulation component remains.

The synchronization control circuit 56 synchronizes the timing of the received signal with the spreading control by a known method, and the spreading control circuit 5
By issuing an instruction to 2, the timing of the output signal of the frequency synthesizer 50 is controlled. Once the synchronization is captured, it is maintained in a known manner thereafter. After the synchronization acquisition, a meaningful primary modulation component appears in the output signal of the second mixer 54. The demodulation circuit 58 extracts information based on MFSK and PSK from the signal for each hopping cycle.
Since the extracted information has four levels for MFSK and two levels for PSK, one of eight codeword chips is received in each hopping cycle. Similar to the first embodiment, when one codeword is formed by seven codeword chips, the decoding circuit 60 obtains 3-bit data such as “000” every 7 hopping cycles, and the 3-bit data is converted into parallel / serial data. By doing so, the original data is decrypted.

Also in the reception block, the hopping cycle is set to an integral multiple of the carrier cycle. This is to match the specifications of the transmission block, but with this setting,
The receiving block can reliably detect the initial phase of each hopping cycle. If there is no known relationship between the hopping period and the carrier period on the transmission block side, the correct initial phase of the hopping period cannot be known even if the receiving block performs down conversion with the same carrier. Because there is an unspecified difference between the carrier phases on the transmitting block side and the receiving block side, the initial phase of each hopping cycle that remains after down-conversion is significant unless the carrier phase has a fixed relationship with the hopping cycle. This is because it cannot be played.

As described above, the reception block is the same as the transmission block.
By detecting the initial phase independently in each hopping period, PS can be used for the primary modulation of FH spread spectrum communication.
It becomes possible to use K. It should be noted that the same improvement or modification as the first embodiment can be considered in the present embodiment. Further, in the present embodiment, the start timing of each hopping cycle is considered as the determination timing of the phase related to PSK, but other predetermined timing may be used. For example, the determination may be made at a timing sufficiently close to the start timing. Also, MFS
4 kinds of fi relating to K and initial phase 0 °, 180 °
By holding 4 × 2 = 8 different signal waveforms as a function of time in a storage device and performing a comparison calculation with the down-converted received signal, theoretically, at any timing during each hopping cycle, the memory It is also possible to determine the initial phase by reading the corresponding part of.

[0062]

According to the spread spectrum communication method of the present invention, a modulation method including at least a phase deviation is adopted as the primary modulation, and the phase of the spread spectrum signal can be independently determined for each demodulation unit period. Since the spread spectrum signal is generated in PSK modulation, PSK modulation can be performed in FH spread spectrum communication, for example. Therefore, the frequency utilization efficiency is improved.

When the phase of the spread spectrum signal is controlled so as to be determined at a predetermined timing (for example, start timing) of each demodulation unit period, the phase determination may be performed at that timing, and information transmission by PSK is performed. It will be possible.

When the demodulation unit period is set to an integral multiple of the carrier cycle and the phase control is performed so that the phase of the spread spectrum signal at the start timing of each demodulation unit period can be determined due to the primary and secondary modulation, Since the phase component due to the carrier wave itself is constant and known, it is possible to add a meaningful phase deviation at the start timing of each demodulation unit period and demodulate this.

In the case of including the step of determining the frequency and the phase by integrating the primary and secondary modulation information, the primary modulation and the secondary modulation can be performed integrally so as to realize the determined frequency and phase, and the hardware The wear configuration can be simplified. In addition, the information can be integrated by, for example, an algebraic sum, and the processing efficiency is improved. The point that phase modulation such as PSK can be used is as described above.

According to the spread spectrum communication device of the present invention, and particularly the transmission block thereof, the above effects can be realized as a device. If the hopping period is generated as an integral multiple of the period of the operation reference clock of the frequency synthesizer, the phase deviation due to the carrier wave becomes constant and known, and the receiving block can demodulate the phase information.

According to the spread spectrum communication apparatus of the present invention, particularly the receiving block thereof, it is possible to demodulate the information by phase modulation according to the same principle as the transmitting block. When the demodulation circuit handles the phase shift information as independent information for each hopping cycle, a modulation method such as differential PSK is unnecessary.

When the transmission block or the reception block determines the frequency ratio of the carrier wave and the operating clock by the two frequency dividers, a desired frequency ratio can be easily realized by appropriately selecting the frequency divider. it can. High frequency dividers often have a fixed division ratio,
This configuration improves design flexibility.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a spread spectrum communication device (transmission block) according to a first embodiment.

FIG. 2 is a diagram showing a relationship between a combination of frequencies f ^{(1) to} f ⁽⁴⁾ and phases φ ⁽¹⁾ and φ ⁽²⁾ and a codeword chip in the first embodiment.

FIG. 3 is a diagram showing a waveform of a signal generated in each part of the frequency synthesizer 6 in accordance with fb and φb in the first embodiment.

FIG. 4 is a diagram showing a relationship between a transmission baseband signal, an operation reference clock, a waveform of a carrier wave, and a phase in the first embodiment.

FIG. 5 is a configuration diagram of a spread spectrum communication device (reception block) according to a second embodiment.

FIG. 6 is a diagram showing a relationship between a bit string of data and a code word to be converted.

[Explanation of symbols]

2 encoding circuit, 4 spreading control circuit, 6,50 frequency synthesizer, 8,34 carrier oscillator, 10 mixer, 12 transmitting circuit, 14,30 antenna, 16, 4
4 VCO, 18,38 1 / m frequency divider, 20, 40
1 / n frequency divider, 22, 42 PLL control circuit, 32 receiving circuit, 36 first mixer, 52 spreading control circuit, 54
Second mixer, 56 synchronization control circuit, 58 demodulation circuit,
60 decoding circuit, 500, 600 DDS, 502,
602 D / A converter, 504, 604 LPF.

Claims (12)

[Claims] 1. A method for encoding data to generate primary modulation information, generating secondary modulation information by spread control, and generating a spread spectrum signal based on these modulation information, wherein the primary modulation information is used. As a spread spectrum communication, a spread spectrum signal is generated in a state in which the phase of the spread spectrum signal can be independently determined for each demodulation unit period Method. 2. The method according to claim 1, wherein the phase of the spread spectrum signal is controlled so that the phase of the spread spectrum signal is determined at a predetermined timing of each demodulation unit period, and thereby the phase of the signal is demodulated. A spread spectrum communication method characterized in that the determination can be made independently in a unit period. 3. The spread spectrum communication method according to claim 2, wherein the predetermined timing is a start timing of each demodulation unit period. 4. The method according to claim 3, wherein the primary modulation and the secondary modulation are performed, and then the carrier having a fixed frequency is mixed to generate the spread spectrum signal. The demodulation unit period is set to an integral multiple of the period of the carrier wave, and phase control is performed so that the phase of the spread spectrum signal at the start timing of each demodulation unit period can be determined due to the primary modulation and the secondary modulation. A spread spectrum communication method characterized by the above. 5. A step of encoding data to be transmitted, a step of generating primary modulation information by a modulation method including at least a phase deviation based on the encoded data, and a spread code sequence for frequency hopping. To generate secondary modulation information by spreading control according to, to determine the frequency and phase by combining the primary and secondary modulation information, and to achieve the determined frequency and phase. A step of performing modulation integrally to generate a transmission baseband signal; and a step of generating a spread spectrum signal by mixing a carrier wave whose phase is independently recognizable in each hopping period with the transmission baseband signal. , A frequency hopping spread spectrum communication method comprising: 6. The spread spectrum communication method according to claim 5, wherein the hopping cycle is an integral multiple of a cycle of a carrier wave. 7. An encoding circuit for encoding data to be transmitted and for generating primary modulation information by a modulation method including at least phase deviation, and for generating secondary modulation information by spreading control according to a spreading code sequence for frequency hopping. A spreading control circuit, a frequency synthesizer that combines the primary modulation information and the secondary modulation information to perform primary modulation and secondary modulation in a lump, and mixes the carrier with the transmission baseband signal. A spread spectrum communication device comprising: a mixer for generating a spread spectrum signal, and applying a signal obtained by dividing a carrier wave as an operation reference clock of the frequency synthesizer. 8. The spread spectrum communication device according to claim 7, wherein the frequency synthesizer generates a hopping cycle with an integral multiple of a cycle of the operation reference clock. 9. A first mixer for mixing a carrier into a received spread spectrum signal to remove a carrier frequency component; a spread control circuit for generating secondary modulation information by spread control according to a spread code sequence for frequency hopping; A frequency synthesizer that generates a baseband signal based on secondary modulation information, a second mixer that mixes the output signal of the first mixer and the output signal of the frequency synthesizer to remove the secondary modulation component, and the second mixer A demodulation circuit that demodulates the output signal of to extract the primary modulation information, and a decoding circuit that decodes the data based on the extracted primary modulation information. A spread spectrum communication device characterized by being provided as an operation reference clock of a frequency synthesizer. 10. The apparatus according to claim 9, wherein the frequency synthesizer generates a hopping cycle with an integral multiple of a cycle of the operation reference clock, and the demodulation circuit includes at least phase deviation information as primary modulation information. A spread spectrum communication device characterized by extraction. 11. The spread spectrum communication apparatus according to claim 10, wherein the demodulation circuit handles the phase deviation information as independent information for each hopping cycle. 12. The apparatus according to claim 7, wherein the apparatus further comprises: a voltage controlled oscillator that outputs an operation reference clock; and a 1 / m frequency divider that divides a carrier wave by m. , A 1 / n frequency divider that divides the operation reference clock by n, and a signal divided by these frequency dividers are input, and the voltage controlled oscillator is such that the frequency ratio between the carrier wave and the operation clock is m: n. A spread spectrum communication device comprising: