JPH0690276B2 - Radar equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a radar that transmits a radio wave to a target and receives an echo reflected by the target to detect the target, and in particular, a continuous wave code The present invention relates to a radar device that uses a modulated transmission signal.

[Prior art]

Before describing the conventional technique, first, a sequence used for code modulation of a transmission signal will be described.

The term "series" as used herein means a time-series arrangement of the numerical values a _n shown in {a _n } = ... a _n-1 a _n a _{n + 1} (1). n is a factor indicating the order of arrangement. a _n is called a sequence component and is a complex number. Also, the sequence {a _n } is a periodic sequence,
There is N that satisfies a _{n + N} = a _n (2) for the components of the sequence, and N is called the period of the sequence. At this time, the series of the first equation can be expressed by the following equation.

{A _n } =… a _N-1 a ₀ a ₁ a ₂ … a _N-1 a ₀ a ₁ … (3) Autocorrelation defined by the following equation as a quantity that describes the mathematical properties of such a sequence. Functions are often used.

Here, * indicates a complex conjugate. As shown in the fourth equation, the autocorrelation function is defined only within the range of m = 0 to m = N−1 because the sequence {a _n } is a periodic sequence, and as a result, the autocorrelation function ρ _{( This is because m)} becomes a periodic function. The cycle is N, which is the same as the cycle of the series {a _n }.

ρ _{(m + N)} = ρ _(m) (5) When applying such a sequence to a real system, in many cases, the autocorrelation function of equation 4 may have the property shown in FIG. Required. That is, it is required that the autocorrelation function has a sharp peak at m = 0 and takes a "sufficiently small value" at other m (0 <m <N). The m = 0 part ρ _(o) of the autocorrelation function is called the main lobe. Also, the part of the autocorrelation function other than m = 0 ρ _{(m) (m = 1,} ～ _{, N-1)}
Is called a side lobe, and the size of the side lobe is related to the value of the main lobe ρ _(o) . Therefore, the fact that the size of the side lobe takes a "sufficiently small value" means that the relationship | ρ _(m) | << | ρ _(o) | _{m = 1,} ... _{, N-1} (6) is satisfied. Means

PN (PseudoNoise) sequences and orthogonal sequences are well known as sequences that satisfy equation 6.

A PN sequence is defined as a sequence whose autocorrelation function satisfies Eq. 7a.

Here, the subscript "PN" is added to clarify that the autocorrelation function is that of the PN sequence.

The M series, the quadratic residue series, and the Hall series are typical of the PN series, and these series are characterized in that the values of the components take either 1 or -1.

On the other hand, an orthogonal sequence is defined as a sequence whose autocorrelation coefficient satisfies (7b).

Here, the subscript "OR" has an orthogonal autocorrelation function (Orthogonal).
It is added to clarify that it is that of the series.

The orthogonal sequence has an extremely excellent property in the sense that the sixth formula is satisfied. The existence of an orthogonal sequence is not well known, and generally the component values have many different values.

Next, the operation of the radar device using the transmission signal code-modulated by such a sequence will be described. Conventionally, PN sequences are often used as sequences used for code modulation in radar devices.

Figure 6 shows, for example, the book "Radar Hand" by MI Skolnik.
2 is a block diagram of the radar device disclosed in "Book-Radar Handbook" PP16-27 to 16-28. In the figure, 1 is a local oscillator as a signal generating means for generating a sine wave signal, 2 is a modulator as a code modulating means for code-modulating the sine wave signal, 3 is a PN sequence generator as a code sequence generating means, Four
Is a power amplifier that amplifies the output signal of the modulator 2, 5 is a low noise amplifier that amplifies the received signal, 6 is a transmitting antenna,
Reference numeral 7 is a receiving antenna, 8 is a detector as a phase detecting means for phase detecting the output signal of the low noise amplifier 5, and 9 is a detector 8
A demodulator as a demodulation means for demodulating the output signal of 10a is a target A, and 10b is a target B. Also, {a _n } is a PN sequence, U
Is a transmission signal, S _a is a reflection signal generated by the transmission signal U being reflected at the target A (10a), and S _b is a transmission signal U being the target B (10b).
, R is a received signal, V is a detected signal, and Z is a demodulated signal.

In addition, in order to simplify the following description, all the mathematical expressions of signals use complex signals. Although such a complex signal does not physically exist, the real signal can correspond to the real part of the complex signal as shown by Euler's formula e ^jωt = cosωt + jsinωt (8) j: imaginary unit.

The local oscillator 1 generates a sine wave signal e ^jωt , and the modulator 2
Forward this to. On the other hand, the PN sequence generator 3 generates a PN sequence {a _n } and transfers it to the modulator 2. Modulator 2
Outputs the transmission signal U by code-modulating the sine wave signal e ^jωt using the PN sequence {a _n }. The transmission signal U is amplified by the power amplifier 4 and then radiated to the external space via the transmission antenna 6. A part of the transmission signal U radiated to the external space is reflected by the target A (10a) and the target B (10b), respectively, and as a result, a reflection signal S _a and a reflection signal S _b are generated. The reflected signal S _a and the reflected signal S _b are respectively received by the receiving antenna 7, and the received signal R
Becomes The received signal R is a combined signal of the reflected signal S _a and the reflected signal S _b , and has the following relationship.

R = S _a + S _b (9) The received signal R is amplified by the low noise amplifier 5 and then detected by the detector 8
Entered in. The detector 8 phase-detects the reception signal R to convert the reception signal R in the RF (Radio Frequency) band into the detection signal V in the video band, and then transfers it to the demodulator 9.
The demodulator 9 inputs the detected signal V and the PN sequence {a _n } transferred from the PN sequence generator 3, demodulates the code modulation applied to the detected signal V and outputs a demodulated signal Z.

The operation of the radar shown in FIG. 6 will be described in more detail with reference to FIGS. 7 and 8. FIG. 7 is a diagram showing the time relationship between the reception signal R and the transmission signal U, components of FIG. 8 is sequence a _n
FIG. In FIG. 7, U, S _a , S _b , and R represent the waveforms of the code-modulated transmission signal, the target A (10a) reflected signal, the target B (10b) reflected signal, and the received signal, respectively. As shown in FIG. 7, the component is switched every τ time, such as the component a ₀ in the time range from t = 0 to t = τ, and the component a _{1 in} the time range from t = τ to t = 2τ. A sine wave signal is code-modulated to generate a transmission signal. The mathematical expression U _(t) of the code-modulated transmission signal U can be given by the following expression.

Here, rect [t] is a rectangular function defined by the following equation.

The rectangular function is a mathematical representation of the switching of components,
The modulation is represented by the product of the component a _n and the sinusoidal signal e ^jωt . The fact that the modulation can be expressed by the product can be clarified by expressing the component a _n by a vector as shown in FIG. A _n | | amplitude components a _n represents the modulation of the amplitude of the sine wave signal, the phase phi _n components a _n denotes the modulation phase of the sinusoidal signal. When the sequence is a PN sequence, the value of the component a _n is either +1 or −1. Therefore, as is clear from the vector diagram of the components of the PN sequence shown in FIG. 10, the code modulation is 0 / π = 2. It is equivalent to phase modulation of phase.

Since the PN sequence {a _n } is a periodic sequence, the modulation applied to the sine wave signal also has a period as shown in FIG. The period T is represented by T = Nτ (12).

Since the reflected signal is generated when a part of the transmitted signal is reflected by the target, the waveforms of the reflected signals S _a and S _b are similar to the waveform of the transmitted signal, as shown in FIG. 7. Further, the timing at which the reflected signal is received by the receiving antenna 7 is delayed by the time required for the radio wave to propagate the round trip distance between the radar and the target. This time delay is t _a for the reflected signal S _{a in} FIG.
And the reflected signal S _b is represented by t _b . From this, the mathematical expressions S _a (t) and S _b (t) of the reflected signal S _a and the reflected signal S _b can be expressed by the following equations.

Here, η _a and η _b are definitions showing the radio wave reflection intensities of the target A (10a) and the target B (10b), respectively.

Since the received signal R is a signal in which both the reflected signal S _a and the reflected signal S _b are combined as shown in the ninth equation, its mathematical expression R (t) is given by the following equation.

The detector 8 phase-detects the received signal R, which is mathematically equivalent to multiplying by e ^−jωt . Therefore, the mathematical expression V (t) of the detection signal V is given by the following expression.

Inside the demodulator 9, correlation processing between the detection signal V and the PN sequence {a _n } is performed. There are two methods of correlation processing, an analog method and a digital method, but the difference between both methods is only whether the demodulated signal Z which is the processing result is output as an analog signal or a digital signal.

Here, the case where the correlation processing is a digital method will be described. At this time, first, the detection signal V transferred from the detector 8 is sampled inside the demodulator 9 and converted into a digital signal. The sampling period at this time is set equal to the switching time τ of the component shown in FIG. 7. The mathematical expression of the detection signal V (kτ) (k = ... -1,0,1 ...) Converted into a digital signal is given by the following expression from the 16th expression.

However, in Equation 17, t _a = k _a τ (18a) t _b = k _b τ (18b).

Expression 17 can be simply written as shown in the following expression, considering that the rectangular function rect [t] becomes 0 except 0t <1 as shown in expression 11.

Next, the demodulator 9 outputs the sampled detection signal V (k) and the PN transmitted from the PN sequence generator 3 as shown in the equation (19).
Using the sequence {a _n }, the correlation processing operation as shown in the following equation is performed and the demodulated signal Z (k) is output.

Substituting equation (19) into equation (20) in order to explain the details of the composite signal Z (k) shown in equation (20) yields equation (21).

Comparing the equations (21) and (4), the term indicated by [] in the equation (21) is nothing but the autocorrelation function of the PN sequence {a _n }.
If the equation ₍ 21 ₎ is written using the autocorrelation function ρ _{PN (m)} of the PN sequence, the equation ₍ 22 ₎ is obtained.

As shown in the formula (22), the demodulated signal Z (k) is the sum of the autocorrelation functions of the PN series.

Now, an example of the amplitude waveform of Z (k) obtained by the above-described operation is shown in FIGS. 9 (a) and 9 (b). FIG. 9 (a) shows the amplitude waveform of Z (k) in the case of η _a η _b , and FIG. 9 (b) shows the amplitude waveform of Z (k) in the case of η _a >> η _b. There is. In these figures, Z _a and Z _b are main lobes of the autocorrelation function, and Y _a and Y _b are side lobes of the autocorrelation function. As shown in FIGS. 9A and 9B, it can be seen that the main lobe and the side lobes interfere when the sequence is the PN sequence. As shown in FIG. 9 (a), there is no difference in the sizes of η _a and η _b (target A
If there is no difference in the radio wave reflection intensities of (10a) and target B (10b)), the interference between the main lobe and the side lobe does not pose a problem so much and it is possible to detect that two target reflected signals have been received from the demodulated signal. However, when there is a large difference between η _a and η _b (there is a large difference in the radio wave reflection intensities of the target A (10a) and the target B (10b)), the interference between the main lobe and the side lobe becomes a big problem. . For example if the main lobe Z _b of FIG. 9 (b) are shown so that the target B (10b) is buried in the side lobes Y _a target A (10b), receives the reflected signals of the two targets from the demodulated signal Can no longer be detected.
Such a situation in which there are large differences in the radio wave reflection intensities of two adjacent targets often occurs in the actual operating environment of a radar, and, for example, an airplane flying near a mountain is a typical example. It is something.

Although the number of targets is limited to two in the above description, the same applies when the reflected signals from N targets are received at the same time.

[Problems to be Solved by the Invention]

As described above, in the conventional radar device that code-modulates the transmission signal by using the PN sequence, the range side lobe occurs in the demodulated signal, and when the large target and the small target are present close to each other, the large target is generated. The demodulation signal of the small target is buried in the range side lobe of the demodulation signal of, and as a result, it is difficult to detect the small target.

The present invention has been made to solve the above problems, and uses an orthogonal sequence as a sequence used for code modulation of a transmission signal, suppresses the occurrence of range side lobes of a demodulated signal as much as possible, and sets a large target and a small target. It is an object of the present invention to provide a radar device that can easily detect a small target even when the radars are in close proximity.

[Means for Solving the Problems]

In the radar apparatus according to the present invention, orthogonal sequence generating means (orthogonal sequence generator 11) is provided as code sequence generating means, and the orthogonal sequence generating means has components 0 and 1 and a period of N.
And an M-sequence generating means (M-sequence generator 24) for outputting an M-sequence signal, and a replacement means connected to the output side of the M-sequence generating means for replacing the components of the input signal and outputting the output signal ( Component replacement unit 25), and this replacement unit sets A ₀ as a positive real number when the component of the input signal is 0. If 1, then A ₁ is a positive real number And the phase difference φ ₁ −φ ₀ and the amplitude ratio.
A ₁ / A ₀ It is characterized in that it is configured to satisfy.

[Action]

In the orthogonal sequence generating means (orthogonal sequence generator 11) provided in the radar device according to the present invention, the means for replacing the M sequence whose output signal component generated by the M sequence generating means (M sequence generator 24) is 0, 1 ( When the component of the M-sequence is 0 inside the replacing means, A ₀ is set as a positive real number. If 1, then A ₁ is a positive real number And the trigonometric function f with φ ₁ −φ ₀ as the phase
Two functions f ₂ (A ₁ / A ₀ ), f ₃ (A ₁ / A ₀ ) of amplitude ratio A ₁ / A ₀ where ₁ (φ ₁ −φ ₀ ) is a coefficient of the linear expression of period N of M sequence The orthogonal sequence is generated so that it becomes equal to the ratio of).

Example of Invention

FIG. 1 is a block diagram showing the configuration of a radar device according to an embodiment of the present invention. In FIG. 1, components corresponding to those shown in FIG. 5 are designated by the same reference numerals, and their description will be omitted. A feature of this embodiment is that an orthogonal sequence generator (orthogonal sequence generator) 11 is provided as a code sequence generator. This orthogonal sequence generator 11 is
M-sequence generating means (M-sequence generating means 24) for outputting M-sequence signals whose components are 0 and 1 and whose period is N
And a component replacer (replacement means) connected to the output side of the M-sequence generator and replacing the components of the input signal and outputting the output signal. This component replacer uses A ₀ as a positive real number when the component of its input signal is 0. If 1, then A ₁ is a positive real number And the phase difference φ ₁ −φ ₀ and the amplitude ratio.
A ₁ / A ₀ is f ₁ ； φ ₁ −φ ₀ Trigonometric function f ₂ ; N is a quadratic function of A ₁ / A ₀ whose coefficient is a linear function f ₃ ; N is a linear function of A ₁ / A ₀ of a coefficient It is configured to satisfy a linear function. Also in FIG.
C _n indicates an orthogonal sequence component. The embodiment shown in FIG. 1 is the fifth embodiment.
The difference from the conventional example shown in the figure is that the means for generating a sequence is
The other configuration is exactly the same except that the orthogonal sequence generator 11 is used instead of the PN sequence generator 3.

Therefore, the operation of the embodiment is almost equivalent to the operation of the conventional example, and the mathematical description of the operation is that the component a _n of the PN sequence in the equations (9) to (21) is the component C of the orthogonal sequence. It can be explained by replacing it with _n . As a result, the demodulated signal Z (k) can be expressed by the following equation using the autocorrelation function ρ _{OR (m)} of the orthogonal sequence shown in the equation 7b.

The demodulated signal Z shown in the equation (23) thus obtained
An example of the amplitude waveform of (k) is shown in (c) of FIG.

As shown in (c) of FIG. 9, when the transmission signal is code-modulated using the orthogonal sequence, the side lobe of the demodulation signal becomes 0, and the interference between the target A and the target B is eliminated. As a result, even when there is a difference in magnitude between the radio wave reflection intensities η _a and η _b ,
The small target is not buried in the side lobe of the large target,
It becomes possible to extremely easily detect a small target close to the large target.

Next, the operation of the orthogonal sequence generator 11, which is the most important component in the radar device according to this embodiment, will be described.
FIG. 2 is a diagram showing the configuration of the orthogonal sequence generator 11.

In FIG. 2, reference numeral 24 is an M-sequence generator composed of a linear feedback shift register (hereinafter referred to as a linear feedback shift register as appropriate), 22a, 22b, 22c and 22d are delay elements, and 23 is an exclusive OR operation. The numeral 25 is a component replacing device as a replacing means for replacing the value of the M-series component with a complex number, which is composed of a microcomputer or the like.

Numerical values of 0 or 1 are stored in the delay elements 22a to 22d. The transfer of the numerical values in these delay elements has a cycle, and the numerical values are transferred in the direction of the arrow for each clock. The numerical value b _n of the delay element 22d is output to the outside as an M-sequence component and transferred to the component replacement unit 25. The exclusive OR calculator 23 calculates the exclusive OR of the numerical values b _n and the numerical values d _n transferred from the delay element 22a and the delay element 22d, and transfers the numerical value e _n as the calculation result to the delay element 22a. . Table 2 shows the definition of exclusive OR.

In the linear feedback shift register having such a configuration, a series generated by inputting initial values other than all zeros to the delay elements 22a to 22d is a known M series. The M-sequence is the sequence generated from the linear feedback shift register and has the maximum period. In the example of FIG. 1, the delay element in the linear feedback shift register has four stages, but in general, this can be extended to k stages. However, in order to generate the M-sequence with the k-stage linear feedback shift register, it is necessary to satisfy the limited combination of the positions of the feedback taps. This combination has already been sought, and one example is shown in Table 3-1 to Table 3-3.

In Tables 3-1 to 3-3, the numbers of connection taps correspond to the numbers of delay elements. For example, in FIG.
a is number 1, delay element 22b is number 2, delay element 22c is number 3, and delay element 22d is number 4.

The period N of the M sequence generated by the combinations shown in Tables 3-1 to 3-3 is determined by the number k of stages of the linear feedback shift register, and is given by the following equation.

N = 2 ^k −1 (29) For example, in the case of the four stages shown in FIG. 2, the period of the M code sequence is 15
Is. That is, the case of k = 4 and N = 15 is shown.

Next, the component replacer 25 inputs the M sequence {b _n } generated by the linear feedback shift register 24, and internally replaces the component b _n with the component C _n.
Replace with. The operation of the component replacer 25 will be described below with reference to the flowchart shown in FIG. First, the component replacer
25 inputs the component b _n sequentially transferred from the linear feedback shift register 24 in step 26. Then, in step 27, the value is checked. If b _n = 0, then step 29
Is executed, and if b _n = 1 then step 28 is executed. If step 28 is performed, the component C _n has Is set to a complex number and is output to the outside in step 30. On the other hand, when step 29 is executed, the component C _n has the value Is set to a complex number and is output to the outside in step 30. At this time, the component replacer 25 is set so that the parameters A ₁ and φ ₁ shown in Equation 30 and the parameters A ₀ and φ ₀ shown in Equation 31 satisfy the following equation.

As shown in Equation 32, the phase difference φ ₁ −φ ₀ and the amplitude ratio
A ₁ / A ₀ is important, and in normal operation, φ ₀ = 0 (33a) and A ₀ = 1 (33b).

It will be described below that the sequence {C _n } of the components generated in this way is an orthogonal sequence.

The autocorrelation function of the sequence {C _n } other than m = 0 according to the embodiment of the present invention can be written from the fourth equation as follows.

here Number of combinations The number of combinations of components that are The number of combinations of components that are Is the number of combinations.

Since the sequence {C _n } is a sequence obtained by substituting the components of the M sequence {b _n }, α, β, γ and δ may be considered as follows.

α; the number of combinations of components in which both b _n and b _{n + m} are 0 β; the number of combinations of components in which b _n is 0 and b _{n + m} is 1 γ; b _n is 1 and b _n The number of combinations of components in which _{+ m} is 0; δ; the number of combinations of components in which both b _n and b _{n + m} are 1.

It can be shown that α, β, γ, and δ take constant values irrespective of the size of m from the nature of the M series. α, β,
The properties of the M-sequence required to derive the values of γ and δ are shown below. These are disclosed in "Code Theory" (3rd edition) (published on July 20, 1976, Shokoido) by Miyagawa, Iwadare, et al.

(1) The cycle of the M sequence is N = 2 ^k −1.

(2) In one cycle of the M sequence, 0 is N = 2 ^k−1 −1 and 1 is
2 ^k-1 are included.

(3) A vector | B _i (i = 0, ..., N-1) is defined from one period {b ₀ , b ₁ , ..., B _N-1 } of the M sequence as shown in the following equation.

At this time, the Hamming distance d _H (| B _i , | of vectors | B _i and | B _j
B _j ), regardless of the combination of | B _i and | B _j ,
The Hamming distance is d _H (| B _i , | B _j ) = 2 ^k−1 i ≠ j (36). Hamming distance is the two vectors | A ＝ (a ₀ , a ₁ , ..., a _N-1 ), | B ＝ (b ₀ , b ₁ , ..., b _N-1 ). Is the distance defined by.

The values of α, β, γ, δ are the vectors | B ₀ and | B _m (m = 1,2,
, N−1) components can be compared and derived.

First, the sum of α and δ is calculated as the 37th b in the vectors | B ₀ and | B _m .
Ε _{n of the} equation is the number of components for which ε _n = 0. Since the Hamming distance between | B ₀ and | B _m is 2 ^k-1 as shown in the 36th formula, regardless of the value of m, α + δ = N−2 ^k−1 = 2 ^k− 1−2 ^{k− 1} = 2 ^k-1 -1 (38). Next, let us consider β and γ.

Again, the vector | b _n = 0 in B _0, the vector | Placing and B a b _{n + m} = 1 and becomes the number of combinations of ingredients beta in ^{_{m β = 2 k-2 +}} d (39), the vector | B ₀ The number γ of the combinations of components where b _n = 1 and b _{n + m} = 0 in the vector | B _m can be expressed as γ = 2 ^k−2 −d (40). This is because the Hamming distance between the vectors | B ₀ and | B _m is d _H (| B ₀ , B _m ) = β + γ = 2 ^k−1 .

On the other hand, the vector according to the nature of the M-sequence | component 0 in B ₀
Each p ₀ the number of remaining components 0 in B _0, the number of remaining components 1 When p ₁ | is the number 2 ^k-1 -1, because the number of component 1 was 2 ^k-1, the vector It is given by the following formula.

p ₀ = 2 ^k-1 −1−β = 2 ^k−2 −1−d (41a) p ₁ = 2 ^k−1 −γ = 2 ^k−2 + d (41b) Similarly, in vector | B _m , the rest The number of components 0 of q ₀ ,
If the remaining number of components 1 is q ₁ , then each is given by the following equation.

q ₀ = 2 ^k-1 -1 γ = 2 ^k-2 -1 + d (42a) q ₁ = 2 ^k-1 -β = 2 ^k-2 -d (42b) However, both p ₀ and q ₀ are vectors. In | B ₀ , | B _m , since it represents the number of combinations of components in which b _n is 0 and b _{n + m} is 0, p ₀ = q ₀ (43a) must be satisfied. Similarly, p ₁ and q ₁ are both vectors | B ₀ ,
| B _m represents a combination of components in which b _n is 1 and b _{n + m} is 1, so p ₁ = q ₁ (43b).

From equations 43a and 43b, d = 0 is obtained, from which β and γ are both equal and given by the following equation regardless of the value of m.

β = γ = 2 ^k−2 (45) Further, the number of components 0 and the number of components 1 of the vector | B ₀ and the vector | B _m are 2 ^k−1 − as shown in Property 2 of the M sequence, respectively. Since there are 1 and 2 ^k-1 , α, β, γ, and δ must satisfy the following relationships.

α + γ = α + β = 2 ^k-1 -1 (46a) β + δ = γ + δ = 2 ^k-1 (46b) Substituting the 45th formula into formulas 46a and 46b, α = 2 ^k-2 -1 (47) We obtain δ = 2 ^k-2 (48). Α and δ given by the 47th equation and the 48th equation satisfy the 38th equation and are consistent.

Substituting the values of β and γ shown in the 45th equation and the values of α and δ shown in the 47th and 48th equations into the 34th equation, the autocorrelation function of the series {C _n } according to the embodiment is You can write like a formula.

The condition for the sequence {C _n } to be an orthogonal sequence is ρ _(m) = 0,
Since (m = 1, 2, ..., N−1), the 32nd expression is derived from this. Note that the relationship of Expression 29 is used to derive Expression 32.

From the above, it is understood that the sequence generated by the above embodiment is an orthogonal sequence.

FIG. 5 is an example of a vector diagram of components of an orthogonal sequence according to the embodiment of the present invention. As shown in FIG. 5, in the orthogonal sequence according to the embodiment of the present invention, there are two component values, 1 and Aa ^{j φ} .

Although the linear feedback shift register is shown as an example of the M-sequence generator in the above embodiment, the present invention can be widely applied to M-sequence generators other than the linear feedback shift register.

〔The invention's effect〕

As described above, according to the present invention, M-sequence generating means for generating an M-sequence having a component of 0,1 and a period of N, and an input M-sequence component connected to the output side of the M-sequence generating means. To
Since the value is constituted by the orthogonal sequence generating means having a replacement means for replacing each according to 0 and 1, the range side lobe of the demodulated signal, that is, the generation of the side lobe of the radar reception signal is suppressed as much as possible, As a result, even when the large target and the small target are present close to each other, the small target can be easily detected, and thus the detection performance can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a radar device according to an embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of an orthogonal sequence generator in this embodiment, and FIG. 3 is that of FIG. Flowchart showing operation of component replacer, fourth
FIG. 5 is a diagram showing the waveform of the autocorrelation number, FIG. 5 is a vector diagram of components of an orthogonal sequence, FIG. 6 is a block diagram showing the configuration of a radar device according to a conventional example, and FIG. , FIG. 8 is a vector diagram of series components, FIGS. 9A to 9C are diagrams showing demodulated signal waveforms, and FIG. 10 is a vector diagram of PN sequence components. 1 ... Local oscillator (signal generation means), 2 ... Modulator (code modulation means), 8 ... Detector (phase detection means), 9 ...
Demodulator (demodulation means), 11 ... Orthogonal sequence generator (orthogonal sequence generation means), 24 ... M sequence generator (M sequence generation means),
25: Component replacement device (replacement means).

Claims (1)

[Claims] 1. A signal generating means for generating a sine wave signal, a code modulating means for code modulating the sine wave signal, a phase detecting means for phase detecting a received signal, and an output signal of the phase detecting means. In a radar device including demodulation means, code sequence generation means for generating a code sequence to be supplied to the code modulation means and the demodulation means, an orthogonal sequence generation means is provided as the code sequence generation means, and the orthogonal sequence generation means is provided. The means is composed of 0 and 1 and outputs M-sequence generating means for outputting an M-sequence signal having a cycle of N. The M-sequence generating means is connected to the output side of the M-sequence generating means and replaces the components of the input signal to output. And a replacement means for outputting a signal, which replacement means A ₀ when the component of the input signal is ₀
Be a positive real number If 1, then A ₁ is a positive real number And the phase difference φ ₁ −φ ₀ and the amplitude ratio.
A ₁ / A ₀ is f ₁ ； The quadratic function of A ₁ / A ₀ whose coefficient is the linear function of f ₂ ; N whose phase is φ ₁ −φ ₀ is the coefficient of the linear function of f ₃ ; N A ₁ / A ₀ The radar device is configured so as to satisfy a linear function of