JP2023064016A - Wireless transmitting method, wireless transmitting device, wireless receiving method, wireless receiving device, and wireless communication method - Google Patents

Abstract

To provide a wireless transmitting method that can adjust a time, phase, and frequency offset (that is, synchronize) with a simple receiving device configuration, and is less likely to be out of synchronization due to the influence of interference or the like.SOLUTION: A wireless transmitting method is characterized in that a plurality of chirp signals are used as a synchronization signal or a part of the synchronization signal, and change rates of the plurality of chirp signals are different. By wirelessly transmitting, as the synchronization signal, a cross-carrier signal in which the chirp signals with the different change rates are combined, time delay can be detected accurately, and stable wireless communication synchronization can be achieved with a simple circuit.SELECTED DRAWING: Figure 7

Description

In wireless communication, it is essential to match the timing, phase, and frequency of the transmitted radio waves at the receiver, and this technique is called "synchronization." The present invention relates to a radio transmission method, a radio transmission device, a radio reception method, a radio reception device, and a radio communication method that achieve reliable synchronization even on a communication channel with noise or interference, and as a result, achieve stable radio transmission.

In wireless communication, a method of dividing data into predetermined chunks and transmitting the data is common. Such chunks of data are referred to by various terms such as blocks, packets, or frames. In the present invention, a chunk of data is described using the term "frame".

When data is transmitted on a frame-by-frame basis, it is necessary to match the reception timing of the frame, the frequency offset of the frame, and the carrier phase of the frame with the internal signal of the receiver, that is, "synchronization". For this reason, it is common to insert a sync signal at the beginning of the frame or in the middle of the frame. This synchronization signal is called by various names such as "preamble", "reference signal", and "frame sync", but it is still a function of synchronizing the receiver with the received radio signal.

JP 2016-46618 A Japanese Patent No. 6821231

FIG. 1 is a diagram briefly explaining two types of conventionally used wireless transmission formats. FIG. 1(A) is a general synchronization technique that adds a "preamble" to the beginning of a frame. A preamble 10 is followed by a frame sync 11 indicating the beginning of a frame and data 12. FIG. Of these, the preamble 10 and the frame sync 11 are synchronization signals. The data 12 includes a header, an error correction code, an error detection code, etc., although they are not shown because they are complicated.

If radio waves transmitted from another wireless transmitter arrive at the receiver at the same timing and interfere with the preamble 10 or frame sync 11, the synchronization will be disturbed and the rest of the data 12 may not be received. As described above, the synchronization method of FIG. 1A has a problem that the preambles are temporally concentrated.

Therefore, Patent Document 1 (Japanese Patent Laid-Open Publication No. 2016-46618) discloses a communication method in which synchronization signals 13 generated by pseudo-random numbers are evenly dispersed in frames as shown in FIG. 1(B).

By using the synchronization signal 13 that is evenly dispersed in the frame, it becomes resistant to interference. However, in order to achieve synchronization (to match time, frequency, phase, etc.), the receiver must decode the evenly distributed synchronization signal. The paradox exists that synchronization is required in order to detect the synchronization signal, since synchronization of the receiver is required for decoding. The method described in Patent Literature 1 has the drawback that the receiver is complicated and the power consumption is high in order to solve this paradox.

Therefore, Patent Literature 2 discloses a wireless transmission method and the like using "a narrowband synchronization signal that exists continuously over the entire frame period when viewed on the time axis".

In the wireless communication method described in Patent Document 2, detection of the narrowband synchronization signal can be processed by fast Fourier transform (FFT), so the paradox can be resolved and synchronization can be easily realized. However, even with the wireless communication method described in Patent Document 2, if there is a frequency offset in the reference frequency oscillator inside the transmitter, it is necessary to search for a frequency, which makes the synchronization circuit complicated. was there.

Therefore, the present invention provides a wireless transmission method that enables time, phase and frequency offsets to be adjusted (that is, synchronization is possible) with a simple receiver configuration, and that synchronization is less likely to be disturbed by the effects of interference. , a radio transmission device, a radio reception method, a radio reception device, and a radio communication method.

A radio transmission method of the present invention is a radio transmission method characterized by using a plurality of chirp signals as a synchronization signal or a part of the synchronization signal, and wherein the plurality of chirp signals have different change rates.

A radio transmission apparatus (2) to which the present invention is applied comprises modulation means (20) for encoding and modulating information to be radio-transmitted, synchronization signal generation means (23) for generating a synchronization signal, the modulation signal and the synchronization signal. Composite signal generating means (26) for generating a composite signal by combining signals, and high frequency modulation means (high frequency signal generating means) for generating a high frequency signal by superimposing a carrier signal on the composite signal. wherein the synchronization signal generating means (23) generates a cross-carrier signal by combining chirp signals with two different change rates (β1, β2). .

In the radio reception method of the present invention, the received radio signal is dechirped by a first chirp rate (β1) to create a first dechirp signal (Q1) (33A), and the received radio signal is subjected to a second chirp rate. A second dechirped signal (Q2) is created (33B) by applying dechirping processing by (β2), and the time of the received radio signal is calculated from the first dechirped signal (Q1) and the second dechirped signal (Q2). A radio reception method characterized by detecting (34) a delay (δ) and correcting (35) the time delay of the received radio signal.

A radio receiver (3) of the present invention comprises front-end means (30) for converting a received radio signal into an IQ signal, synchronization signal extraction means (32) for extracting a synchronization signal from the IQ signal, and In response, channel correction means (35) for correcting the time delay (δ) and phase rotation of the IQ signal to create a corrected IQ signal, and decoding means (38) for decoding the corrected IQ signal are used to obtain received data. configured to
The synchronization signal extracting means (32) includes first dechirping means (33A) for dechirping the IQ signal with a first chirp rate (β1) to obtain a first dechirping signal (Q1); second dechirping means (33B) for dechirping the signal with a second chirping rate (β2) to obtain a second dechirped signal (Q2); The radio receiving apparatus is characterized by including synchronization signal processing means (34) for detecting the time delay (.delta.) of the received radio signal.

In the wireless communication method of the present invention, a modulated signal (mod(t)) is generated by encoding and modulating transmission information, and two complex function signals exp(j2p·β1·t· t) and exp(j2p·β2·t·t) are generated, and a carrier signal is superimposed on the modulation signal and the sync signal to generate a high-frequency signal (TX(t)). is generated and transmitted as radio waves, and the high-frequency signal is received to restore the transmission information, wherein the synchronization signal (Cr(t)) included in the high-frequency signal is used to generate the time on the wireless transmission path A wireless communication method characterized by decoding and detecting the transmission information by detecting a delay (δ) and correcting the time delay.

[Effect of the invention]
According to the present invention, a radio transmission method, a radio transmission device, a radio reception method, a radio reception device, and a radio communication method are realized, in which synchronization signals are less disturbed by interference from other systems and can be transmitted more reliably. can. By using a wireless communication device to which these are applied, it is possible to realize stable communication. Further, in the radio transmission apparatus to which the radio transmission method according to the present invention is applied, transmission power is not allocated to useless signals such as preambles, and lower power consumption can be realized than before. In addition, since the radio receiving apparatus to which the radio receiving method according to the present invention is applied can efficiently realize synchronization signal processing, it is possible to operate the receiving apparatus with a simpler configuration and lower power consumption than before.

FIG. 2 is a diagram briefly explaining two types of conventionally used wireless transmission formats; 1 is a diagram illustrating the concept of the wireless communication format of the present invention; FIG. 1 is a block diagram of a wireless transmission device 2 of the present invention; FIG. 3 is a configuration diagram of a modulated pulse generation block 21 used in the radio transmission device 2; FIG. 3 is a configuration diagram of a down-chirp generation block 24A used in the radio transmission device 2; FIG. 3 is a diagram schematically showing each signal in the radio transmission device 2; FIG. FIG. 4 is a diagram schematically showing the spectrum of a radio transmission signal in the present invention; 1 is a block diagram of a radio receiver 3 of the present invention; FIG. 3 is a configuration diagram of synchronization signal extraction means 32 used in the radio receiving apparatus 3. FIG. 4 shows the spectrum and spectrogram of a transmitted radio wave in an experiment using the wireless transmission method of the present invention; It is an example of a constellation obtained by an experiment using the radio reception method of the present invention. FIG. 10 is a diagram schematically showing the spectrum of a radio transmission signal in the second embodiment; FIG. 12 is a diagram showing the concept of a wireless communication format in the third embodiment; FIG. It is a block diagram of the wireless transmission device 2 of the third embodiment. FIG. 12 is a diagram showing the concept of a wireless communication format in the fourth embodiment; FIG. FIG. 12 is a diagram showing the concept of a wireless communication format in the fifth embodiment; FIG.

Hereinafter, a form for carrying out the present disclosure (hereinafter referred to as an embodiment) will be described.

<First embodiment>
In the following, as an example, a case will be described in which BPSK (Binary Phase Shift Keying) with a symbol rate of fb (=100ksps) is used as a modulation method, and wireless transmission is performed with a frame of 0.5 seconds and a carrier frequency of fc=920MHz. Of course, it goes without saying that the present invention is not limited to this and can be implemented in various embodiments.

FIG. 2 is a diagram showing the concept of the wireless communication format of the present invention. In FIG. 2, the communication format of the present invention is shown with frequency on the vertical axis and time on the horizontal axis. Here, the data 12 includes an error correction code, authentication information, etc., but they are omitted in FIG. 2 for the sake of simplification. The frequency bandwidth occupied by data 12 is denoted by Bw. For example, when the symbol rate fb is 100ksps (Symbol Per Second), the frequency bandwidth Bw is approximately 150kHz.

In FIG. 2A, information transmitted as a frame consists of a frame sync 11 representing the frame start timing and data 12 . Generally, the frame sync 11 modulation method is often the same as that of the data 12 . At this time, the frequency bandwidth occupied by the frame sync 11 is also Bw.

In conventional communication methods, it was common to transmit a synchronization signal called a preamble near the beginning of a frame. On the other hand, in the communication format of the present invention shown in FIG. 2, the cross-carrier 14 is transmitted over substantially the entire time of the frame instead of the preamble.

As shown in FIGS. 2B and 2C, the cross-carrier 14 is composed of a down-chirp signal 14A and an up-chirp signal 14B. In this figure, the down-chirp signal 14A is a signal whose starting frequency is the frequency +fs and whose frequency thereafter drops at a predetermined chirp rate (β1). Similarly, the up-chirp signal 14B has a frequency of -fs as a starting point and thereafter increases at a predetermined chirp rate (β2). This figure illustrates a case where the frame time T is 0.5 seconds, the chirp start frequency fs=75 kHz, β1=-300 kHz/sec, and β2=+300 kHz/sec.

ここでαは定数、rect(t)は矩形関数である。 Assuming that the down-chirp signal 14A is Ca(t) and the up-chirp signal 14B is Cb(t), they can be expressed by the following equations 1 and 2, respectively.

where α is a constant and rect(t) is a rectangle function.

<Configuration of wireless transmitter>
FIG. 3 is a block diagram of the radio transmission device 2 of the present invention. FIG. 6 is a timing chart for schematically explaining the signals of the wireless transmission device 2. As shown in FIG. Transmission data “101101 . The symbol clock frequency is 100 kHz when the symbol rate fb is 100 ksps. The transmission data is modulated by the modulating means 20, added with the synchronizing signal (cross carrier 14) generated by the synchronizing signal generating means 23, amplified by the high frequency modulating means 27, and transmitted from the antenna 202 as radio waves TX(t). .

In FIG. 3 , the transmission data "101101..." is input to the modulated pulse generation block 21 and converted into one pulse (Mod Pulse) for each symbol. As shown in FIGS. 6A to 6C, Mod Pulse is a bipolar pulse train whose polarity changes according to transmission data.

Mod Pulse is low-pass filtered by the low-pass filter 22 to become the modulated signal mod(t). (FIG. 6(D)) As a characteristic of the low-pass filter 22, a Root Raised Cosine (RRC) characteristic capable of suppressing intersymbol interference can be used. In this case, the passband width Bw of the low-pass filter 22 is often about 1.5 times the symbol rate fb. In this embodiment, Bw = 150kHz.

A system controller (not shown) changes the Start Pulse (FIG. 6(E)) from "0" to "1" to instruct the start of data transmission, and at the same time, the cross-carrier signal Cr(t) is generated. Here, the cross-carrier signal Cr(t) is a signal obtained by synthesizing the down-chirp signal Ca(t) and the up-chirp signal Cb(t), as will be described later.

The synchronization signal generating means 23 comprises a down-chirp (β1) generation block 24A and an up-chirp (β2) generation block 24B, which generate a down-chirp signal Ca(t) and an up-chirp signal Cb(t), respectively. These signals are added by adder 25 to generate cross-carrier signal Cr(t).

Here, down-chirp signal Ca(t) and up-chirp signal Cb(t) may be simplified. This is the case when the two chirp plates have different polarities and the same amplitude (ie, β=-β1=+β2). In this case, the cross-carrier signal Cr(t) becomes a real number and can be expressed by the cosine function (cosine) shown in Equation 3, which can be simplified.

The adder 26 adds the modulating signal mod(t) and the cross-carrier signal Cr(t) and supplies the result to the mixer 28 . As described above, when -β1=β2, the cross-carrier signal Cr(t) becomes a real number and the imaginary part becomes unnecessary. Adder 26 can also be omitted by feeding the signal into the Q axis of mixer 28 . Experimental examples (FIGS. 10 and 11) to be described later show a case where −β1=β2.

The modulated signal mod(t) and the cross-carrier signal Cr(t) are combined by the mixer 28, and the carrier (frequency fc) supplied from the local oscillator 29 is superimposed thereon. Carrier frequency fc can be, for example, 920 Mz. Bandpass filter 200 removes unwanted components contained in the signal from mixer 28 . The output of the bandpass filter 200 is amplified by the linear amplifier 201 and transmitted from the antenna 202 to the air as radio waves TX(t).

FIG. 4 is a configuration diagram of the modulated pulse generation block 21 used in the radio transmission device 2. As shown in FIG. The configuration of the modulated pulse generation block 21 will be described with reference to FIG. Transmission data is input every symbol clock (syclk) and converted into a bipolar signal by the mapper 210 . That is, if the transmission data is "1", it is converted to "+1", and if the transmission data is "0", it is converted to "-1".

A rising edge detection circuit 211 generates a pulse at the rising edge of the symbol clock (syclk). The rise detection circuit 211 is composed of a PLL circuit 213 , a D flip-flop 214 , a NOT gate 215 and an AND gate 216 . The rising edge detection circuit 211 generates a rising edge pulse at the timing when the symbol clock (syclk) changes from logic "0" to logic "1".

The PLL circuit 213 generates a clock X16 obtained by multiplying the frequency of the symbol clock (syclk) by 16. In this example, the symbol clock (syclk) is 100 kHz, so the clock X16 is a high-speed clock of 1.6 MHz. The rising edge pulse is multiplied by the output of mapper 210 by multiplier 212 and output as one bipolar pulse (Mod Pulse) per symbol.

The Mod Pulse generated in this manner is a bipolar impulse train whose polarity changes according to the transmission data, as shown in FIG. 6(C). Also, since Mod Pulse is synchronized with the rise of the symbol clock (syclk), it changes at the center of the time (Ts) during which one symbol is transmitted.

The synchronization signal generating means 23 is composed of a down-chirp generating means 24A, an up-chirp generating means 24B, and an adder 25. FIG. FIG. 5 is a configuration diagram of the down chirp generating means 24A. Since the chirp rate of the up-chirp generating means 24B is different, the description thereof is omitted.

In FIG. 5, when Start Pulse changes from "0" to "1" to instruct the start of data transmission, the counter 240 starts counting the clock X16. When the frequency of the clock X16 is 1.6 MHz, the count value n, which was "0" at the start of the frame, is a 20-bit integer that changes up to 800,000 at the end of the frame after 0.5 seconds.

ここで関数mod( )は剰余演算を表し、ΔはクロックＸ１６の逆数（0.625μ秒）である。 The nonvolatile memory 241 receives a 20-bit address and outputs prewritten 8-bit data. As such a non-volatile memory 241, for example, a semiconductor (AT27C080) manufactured by ATMEL can be used. By writing in advance the value shown in Equation 4 for each address (n), it is possible to generate the phase θ ₁ (n) of the down-chirp signal with the initial frequency fs and change rate β1.

where the function mod() represents the remainder operation and Δ is the reciprocal of the clock X16 (0.625 µs).

The exponential function block 242 is composed of a non-volatile memory or the like, and outputs cos {θ _{1 (} n)} as the real part and sin {θ ₁ (n)} as the imaginary part for the phase θ 1 (n) of the down-chirp signal. do. The amplifier 243 multiplies the output of the exponential function block 232 by a predetermined constant α to output as a down-chirp signal Ca(t). If there is interference from other systems and the synchronization is disturbed, a large value can be adopted for α to improve the synchronization performance.

As shown in FIG. 6(F), the down-chirp signal phase θ ₁ (n) generated in the manner described above gradually changes with the passage of time, and the degree of change is represented by a quadratic function. . As a result, the real part cos {θ ₁ (n)} of the down chirp signal Ca(t) becomes a chirp signal whose frequency decreases with time as illustrated in FIG. 6(G).

ここでε_TXは無線送信装置２で生じる送信周波数の偏差である。 As described above, the cross-carrier signal Cr(t) is generated as a synchronization signal simultaneously with the modulating signal mod(t). These are synthesized by the mixer 28, and the carrier (frequency fc) is superimposed by the high frequency modulation means 27 to produce the transmission signal TX(t) (see FIGS. 6(H) and 6(I)). The transmission signal TX(t) can be represented by Equation 5 below.

Here, ε _TX is the transmission frequency deviation that occurs in the radio transmission device 2 .

FIG. 7 is a diagram schematically showing the spectrum of the transmission signal TX(t). The frame sync 11 and data 12 are BPSK modulated signals (mod(t)) having a flat frequency characteristic of approximately 150 kHz centered on the carrier frequency fc. Also, as illustrated in FIG. 7, the cross-carrier signal Cr(t) is composed of up-chirp and down-chirp around the carrier frequency fc, so it is observed as a character "X" in the figure.

<Configuration of wireless receiver>
FIG. 8 is a block diagram of the radio receiver 3 of the present invention. The radio receiver 3 of the present invention comprises an antenna 301, a front end 30, a synchronization signal extraction means 32, a channel correction means 35 and a decoding means .

ここでφc(t)は無線伝搬で発生する位相回転であり、多くの場合その周波数成分は数ヘルツ程度の緩やかな変化である。またδは無線通信で生じる時間遅れであり、ε_TXは無線送信装置２で生じた周波数偏差である。 The received signal RX(t) received by the antenna 301 is expressed by the following equation 6,

Here, φc(t) is the phase rotation that occurs in radio propagation, and in many cases, its frequency component changes gently on the order of several hertz. δ is the time delay that occurs in wireless communication, and _εTX is the frequency deviation that occurs in the wireless transmission device 2 .

Front end 30 comprises amplifier 302 , bandpass filter 303 , local oscillator 304 , mixer 305 and AD converter 306 . A weak radio wave received by an antenna 301 is amplified by an amplifier 302, unnecessary frequency components are removed by a bandpass filter 303, carrier wave frequency (fc) components are removed by a mixer 305 and a local oscillator 304, and an AD converter 306 Convert to digital information (IQ signal). Here, sampling of the AD converter 306 is performed by the system clock (CLK), and the frequency of the system clock (CLK) is set sufficiently high, for example, 1.5MH. A sampling interval Δ of the AD converter 306 is the reciprocal of the system clock (CLK).

ここでε_rは無線送信装置２による周波数偏差ε_TXと、無線受信装置３に搭載された局部発振器３０４の周波数偏差ε_RXを加えた値であり、送受信を総合した周波数偏差である。 The IQ signal IQ _B (n) shown in the following equation 7 can be obtained by the front end 30 described above.

Here, ε _r is the sum of the frequency deviation ε _TX of the radio transmitter 2 and the frequency deviation ε _RX of the local oscillator 304 mounted on the radio receiver 3, and is the total frequency deviation of transmission and reception.

上式７の位相回転φ(n)と、時間遅れδを求めて補正することにより同期が実現できる。 As described above, the IQ signal IQ _B (n) has a total of three phase deviations, ie, the frequency shift ε _r and the gentle phase rotation φc. Putting these components together as φ(n),

Synchronization can be realized by obtaining and correcting the phase rotation φ(n) and the time delay δ in the above equation (7).

FIG. 9 shows the configuration of the synchronizing signal extracting means 32 which receives the IQ signal IQ _B (n) and the system clock CLK as inputs, detects the transmission line characteristics (δ, φ(n)), and outputs them. The sync signal extraction means 32 extracts the down-chirp sync signal Q ₁ (n) and the up-chirp sync signal Q ₂ (n) by two dechirp circuits 33A and 33B. Next, the synchronization signal processing means 34 is configured to detect the transmission path characteristics (.delta., .phi.(n)).

When a system controller (not shown) starts synchronizing signal extraction, the counter 79 counts the system clock CLK and outputs a count value n.

The dechirping circuit 33A comprises a non-volatile memory 331A and a phase reverse rotation block 330A, performs chirp correction at a chirp rate β1 on the IQ signal IQ _B (n), and extracts the down chirp synchronization signal Q ₁ (n). A dechirping circuit 33B performs chirp correction at a chirping rate β2 on the IQ signal IQ _B (n) to extract an up-chirped synchronizing signal Q ₂ (n).

By writing the phase θ ₃ (n) shown in the following equation 9 corresponding to the address (n) of the nonvolatile memory 331A, a down-chirp signal with an initial frequency fs and a chirp rate β1 can be generated. The phase θ ₄ (n) derived by the non-volatile memory 331B can be constructed in the same way, except that the chirp rate is changed to β2 and the initial frequency to +fs. (See Equation 10 below.)

Phase derotation blocks 330A and 330B, also comprised of non-volatile memory, perform chirp correction on the IQ signal IQ _B (n) to produce a down-chirp sync signal Q ₁ (n) as shown in Equations 11 and 12 below. Extract the up-chirp sync signal Q ₂ (n).

Fast Fourier Transforms (FFT) 70A and 70B perform Fourier transforms on the down-chirp sync signal Q ₁ (n) and the up-chirp sync signal Q ₂ (n) to obtain frequency responses. Peak detection circuits 72A and 72B detect frequencies (fd, fu) at which the frequency response peaks. Subtraction circuit 76 finds the difference between the two peak frequencies (fd, fu) and division circuit 73 divides by 2β to find time delay δ from equation 13 below.

By the above processing, the frequency deviation _εr is removed, and the accurate time delay δ can be obtained. As a result, the delay circuit 36 shown in FIG. 8 can correct the time delay .delta.

Peak filters 71A and 71B are narrowband filters that extract spectral components around two peak frequencies (fd, fu). Inverse Fourier transform circuits 74A and 74B inverse Fourier transform the signal components extracted by the peak filters 71A and 71B. The arctangent calculators 75A and 75B detect the phase component φ(n) of the transmission line characteristic by extracting the phase component from the output of the inverse Fourier transform circuit. An adder circuit 77 adds the outputs of the two arctangent calculators 75A and 75B, and a divider circuit 78 divides the result by 2 to obtain the phase component φ(n) of the transmission line characteristic with less noise after averaging processing. be able to.

In the configuration of the radio receiver 3 shown in FIG. 8, the phase rotation correction circuit 36 reversely rotates the phase of the IQ signal IQ _B (n) by -φ(n), thereby correcting the frequency deviation and phase rotation occurring in the transmission path. is corrected and output as an IQ signal IQ _C (n).

As described above, the synchronizing signal extracting means 32 extracts the down-chirp synchronizing signal Q ₁ (n) and the up-chirp synchronizing signal Q ₂ (n) by the two dechirp circuits 33A and 33B, and the synchronizing signal processing means 34 The channel characteristics (δ, φ(n)) can be detected and output, and the transmission channel characteristics (δ, φ(n)) thus obtained are used to generate the IQ signal IQ _B (n). Synchronization can be achieved by correcting.

<Experimental results>
FIG. 10 shows an example of experimental results using the wireless transmission method of this system. FIG. 10A shows the result of observing the transmission signal TX(t) output from the radio communication apparatus of this system with a spectrum analyzer. A spectrum spread over the BPSK modulation bandwidth (Bw=150 kHz) is confirmed near the carrier frequency (fc=920 MHz).

FIG. 10B is the result of spectrogram observation of the transmission signal TX(t). Here, the spectrogram is a method of creating a two-dimensional image with time on the vertical axis and frequency on the horizontal axis, and expressing the signal intensity by pixel brightness. From this spectrumgram, it was confirmed that the cross-carrier signal Cr(t) whose frequency changes with time is displayed like an "X" centered on the carrier frequency.

FIG. 11 is a constellation observed in the radio receiver of the present invention. Due to the frequency deviation (ε _TX , ε _Rx ) generated in each of the transmitter and receiver, and the phase rotation applied in the propagation path, the constellation of the IQ signal IQ _B (n) before synchronization correction is swirling. rotating. (FIG. 11A) On the other hand, the constellation of the IQ signal IQ _C (n) subjected to the synchronizing signal processing of the present invention is in a decodable state as the rotation stops perfectly. (FIG. 11B) Here the I axis is a BPSK modulated signal, so it is divided into two levels "+1, -1". A wide band is observed on the Q-axis as the cross-carrier signal Cr(t).

From the above experiments, it was confirmed that synchronization is possible by using a cross-carrier signal that combines two chirp signals with different change rates.

<Second embodiment>
FIG. 12 is a diagram schematically showing the spectrum of a radio transmission signal in the second embodiment according to the invention. FIG. 12A uses two different chir rates (β1, β2) as the cross-carrier signal Cr(t) as in the first embodiment. In FIG. 12B, different chirp rates (β3, β4) are used as the cross-carrier signal Cr(t). These four chir plates (β1, β2, β3, β4) are different from each other.

For example, when company A uses the signal in FIG. 12A and company B uses the signal in FIG. It is possible to prevent the synchronization signals from interfering with each other due to the different plates. By changing the chirp rate according to the system in this way, it is possible to operate a plurality of different systems in the same frequency band.

<Third embodiment>
FIG. 13 is a diagram showing the concept of the wireless communication format in the third embodiment related to the present invention. In this figure, the down-chirp signal 14A and the up-chirp signal 14B are periodically turned on and off. Also, the turn-on time zones 14A and 14B are configured to be different from each other so that the down-chirp signal 14A and the up-chirp signal 14B do not interfere with each other. Therefore, interference between the down-chirp signal 14A and the up-chirp signal 14B can be prevented.

FIG. 14 is a block diagram of a wireless transmission device 2 that implements the method of FIG. 13 (the method of periodically turning on and off the down-chirp signal 14A and the up-chirp signal 14B). In the figure, an oscillator 231 generates a periodic signal, and an inverting circuit 232 switches two analog switches 230A and 230B in opposite phases, whereby the down-chirp signal 14A and the up-chirp signal 14B are switched at timings that do not overlap each other. . A low-pass filter (LPF) 233 removes high frequency components generated at switching timing.

A configuration of the radio receiving apparatus 3 when periodically switching between the down-chirp signal 14A and the up-chirp signal 14B will be described. By narrowing the passband of the narrow band filters (peak filters 71A and 71B) mounted in the sync signal extracting means 32, the intermittently transmitted down-chirp signal 14A and up-chirp signal 14B can be smoothed. As a result, synchronization can be realized using the radio receiving apparatus 3 described in the first embodiment as it is.

<Fourth embodiment>
FIG. 15 is a diagram showing the concept of the wireless communication format in the fourth embodiment. FIG. 15 shows a fourth embodiment in which the wireless communication method described in the third embodiment is further developed. In the wireless communication format shown in this figure, a BPSK signal (frame sync 11 and data 12) is intermittently transmitted. At the timing when the BPSK signal is interrupted, the down-chirp signal 14A and the up-chirp signal 14B are alternately switched and inserted as the cross-carrier signal. By configuring in this way, it is possible to prevent interference between the BPSK signal and the cross-carrier signal.

<Fifth embodiment>
FIG. 16 is a diagram showing the concept of the wireless communication format in the fifth embodiment. FIG. 16 shows a fifth embodiment in which the radio communication method described in the first embodiment is further developed. In the radio communication format shown in this figure, signals are created by adding cross-carrier signals 14A and 14B to BPSK signals (frame sync 11 and data 12), and chirp modulation is applied to these signals. As a result, the signal frequency band is widened from fc-fs to fc+fz, and it becomes possible to realize stable communication by reducing the influence of interference.

Of course, as shown in the second embodiment, multiplexing can also be achieved by changing the two chirp rates (β5 and β6) depending on the system. It is also possible to intermittently intermittently cross-carrier signals and data signals as shown in the third and fourth embodiments.

Claims (11)

A radio transmission method, wherein a plurality of chirp signals are used as a synchronization signal or part of said synchronization signal, said chirp signals having different rates of change. 2. The radio transmission method according to claim 1, wherein two change rates ([beta]1, [beta]2) of the plurality of different change rates have the same absolute value and different signs. 2. The method of claim 1, wherein said plurality of chirp signals are present for substantially the entire duration of a frame. Modulation means (20) for encoding and modulating information to be wirelessly transmitted, Synchronization signal creation means (23) for creating a synchronization signal, Synthesis signal creation for synthesizing the modulation signal and the synchronization signal to create a synthesized signal. means (26); and high-frequency modulation means 27 (high-frequency signal generating means) for generating a high-frequency signal by superimposing a carrier signal on the combined signal, wherein
A radio transmitting apparatus, wherein the synchronization signal generating means (23) generates a cross-carrier signal by synthesizing chirp signals with two different change rates (β1, β2). 5. The radio transmitting apparatus according to claim 4, wherein the two different change rates have the same absolute value and different signs. 5. The radio transmitting apparatus according to claim 4, wherein the cross-carrier signal is a signal that exists continuously over the entire frame period. dechirping the received radio signal with a first chirping rate (β1) to create a first dechirping signal (Q1) (33A);
dechirping the received radio signal with a second chirping rate (β2) to create a second dechirping signal (Q2) (33B);
detecting a time delay (δ) of the received radio wave signal from the first dechirped signal (Q1) and the second dechirped signal (Q2) (34);
A radio reception method characterized by correcting (35) the time delay of the received radio signal. detecting a first peak frequency (fd) from the first dechirped signal; detecting a second peak frequency (fu) from the second dechirped signal; and difference between the first and second frequency peaks. 8. A method of radio reception as claimed in claim 7, characterized in that the time delay ([delta]) of the received signal is detected by detecting (76) . front-end means (30) for converting a received radio signal into an IQ signal; synchronization signal extraction means (32) for extracting a synchronization signal from the IQ signal; and time delay (δ) of the IQ signal according to the synchronization signal. and channel correction means (35) for correcting the phase rotation to generate a corrected IQ signal, and decoding means (38) for decoding the corrected IQ signal to obtain received data,
The synchronization signal extracting means (32) includes first dechirping means (33A) for dechirping the IQ signal with a first chirp rate (β1) to obtain a first dechirping signal (Q1); second dechirping means (33B) for dechirping the signal with a second chirping rate (β2) to obtain a second dechirped signal (Q2); A radio receiving apparatus comprising a synchronization signal processing means (34) for detecting a time delay (.delta.) of said received radio wave signal. The synchronization signal extracting means (34)
First FFT means (70A) for fast Fourier transforming the first dechirped signal (Q1), and first peak detection means for detecting a first peak frequency (fd) from the output of the first FFT means (72A) and
Second FFT means (70B) for fast Fourier transforming the second dechirped signal (Q2), and second peak detection means for detecting a second peak frequency (fu) from the output of the second FFT means (72B) and
10. The method according to claim 9, wherein the time delay ([delta]) of the received radio wave signal is detected by subtraction means (76) for detecting the difference between the first frequency peak and the second frequency peak. radio receiver. A modulation signal (mod(t)) is created by encoding and modulating transmission information, and two complex function signals exp(j2p*β1*t*t) and exp(j2p*β2) with linearly varying frequencies are generated.・Create a synchronous signal (Cr(t)) containing t・t), superimpose a carrier signal on the modulated signal and the synchronous signal to create a high-frequency signal (TX(t)), and transmit it as a radio wave. , a wireless communication method for receiving the high-frequency signal and restoring the transmission information,
A radio characterized by detecting a time delay (δ) in a radio transmission path from the synchronization signal (Cr(t)) contained in the high-frequency signal, and decoding and detecting the transmission information by correcting the time delay. Communication method.

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