KR20110136574A - Range resolution improvementand method of short range radar apparatus of direct sequence-ultra wide band type - Google Patents

Abstract

PURPOSE: A resolution improvement method of a direct sequence ultra-wideband mode short range radar apparatus is provided to use an analog mode which uses an analog correlator in a distance resolution processor, thereby improving precision and distance resolution. CONSTITUTION: A system clock generator(11) generates a system clock. A phase-locked loop(16) generates a high frequency signal. A first clock converter(12) and second clock converter(17) convert frequencies. A first PRBS(Pseudo Random Binary Sequence) pattern generator(13) and second PRBS pattern generator(18) generates a PRBS signal. A distance resolution processor(23) computes the distance from a subject with an auto-correlation characteristic.

Description

Range resolution improvement and method of short range radar apparatus of direct sequence-ultra wide band type

The present invention relates to a short-range location tracking technology using radio waves, and more specifically, to implement a short-range location tracking radar system in a DS-UWB (Direct Sequence-Ultra Wide Band: DS-UWB) method within 1 GHz bandwidth The present invention relates to a method for improving the distance resolution of a DS-UWB type short-range radar device, which is suitable for a vehicle-mounted type by having a high precision and high resolution accuracy of less than ten centimeters (cm).

The short-range radar device detects an object within a range of several hundred meters and measures a distance and a moving speed of a target.The short-range radar device transmits radio waves to detect a time difference between a transmitting wave and a receiving wave, and uses the detected time difference to The distance and the relative speed with respect to the vehicle or obstacle is determined, and a plurality of vehicles can be used simultaneously in the same area because they are mounted in a specific place or a vehicle such as a tram and a vehicle. As such, when a plurality of radar devices are used in the same region, the distance and the moving speed of the target can be accurately obtained by preventing interference between radar devices.

When multiple radar devices are used in the same area, to prevent interference, it is desirable to use frequencies in the bands far enough apart, but the number of radar devices used is limited because the bands that can be allocated within a given bandwidth are limited. It must be.

In order to overcome this, generally, a signal of a plurality of channels down by the hopping frequency (f _h ) is generated based on one transmission frequency (f ₀ ) so that the transmission frequency signal and the signals of the changed channels are alternately generated. Although a radar apparatus for transmitting and receiving has been developed, when using a plurality of channels down to the hopping frequency as described above, distance resolution is improved, but distance measurement ambiguity occurs.

In radar devices, distance resolution means the ability to separate two objects and identify them. Distance ambiguity means that the measured distance is unreliable for targets outside the range that can be measured by the radar device. For example, for a radar device with an unambiguous measuring distance of 100m, if the target is located at 110m, the radar device will display this moving target as 10m. Therefore, when the displayed position is 10m, it is difficult to determine whether it is actually 10m or 110m.

These radar devices are largely pulsed, frequency modulated continuous wave (hereinafter referred to as 'FMCW'), and direct sequence ultra wideband (hereinafter referred to as 'DS-UWB'). It is divided into three.

The pulsed radar device transmits an impulse string, detects a signal reflected from a subject, and measures a time difference between a transmission signal and a reception signal to calculate a distance.

The FMCW-type radar device continuously transmits a radio signal that changes periodically to the surface of the measurement object, receives it, calculates a frequency difference between the frequency at the time of oscillation and the reflected signal, and converts the distance.

In the conventional radar device of the DS-UWB method, the autocorrelation property of the random number code uses a property similar to that of an impulse, as shown in FIG. 1, and modulates and transmits a random number code to a carrier, and is reflected from a subject. The distance from the subject can be measured by calculating a correlation value on the random number coding time axis that transmits the received signal and examining the correlation value at a specific time value. In particular, this DS-USB radar device has a very high power efficiency compared to the pulse method, and there is no signal interference between devices in the same device, and a narrow bandwidth is used in the signal processing. Therefore, compared to the impulse method or the FMCW method, it is possible to measure the distance with very high resolution even at low power, and has the ability to identify the subject even when there are several subjects at the same time.

On the other hand, the short-range radar device for vehicle front sensing measures the speed and distance of the preceding vehicle and obstacles in front of the vehicle by using the short-range radar sensor attached to the front of the vehicle. It is possible to drive safely, and such a short-range radar device is used as a core technology for an adaptive cruise control system.

In the case of automobiles, in particular for forward looking systems such as automatic brakes and automated driving control, FMCW radars are used. In the case of FMCW radar, the frequency of the transmitted signal replaces the start frequency to the end frequency. The transmitted signal is reflected by the obstacle and received by the FMCW receiver. The signal received by the FMCW receiver from the transmitter to the obstacle and thus back to the receiver is delayed in time according to the travel time of the electromagnetic wave. Since the frequency of the transmitted signal varies over time, the frequency of the received signal at any time is slightly different from the frequency of the transmitted signal. In the absence of a Doppler shift, the distance to the obstacle can be calculated by comparing the frequency of the received signal with the frequency of the transmitted signal. The presence of the Doppler shift shifts the frequency of the received signal and causes the obstacle to appear closer or farther relative to the actual position.

UltraWideband (UWB) impulse radars are used in vehicle warning systems. UWB based radars, however, are undesirable because these radars transmit energy over a very wide bandwidth and generate electromagnetic interference that can interfere with other radio frequency systems such as radio broadcasting, television, cellular phones, and the like. UWB radars must operate at very low power to avoid violating standards promulgated by the Federal Communications Commission (FCC). UWB radars also require antennas that can be used with very wideband signals transmitted and received by the radar. However, very wide broadband antennas can be difficult to design and mount.

The technical problem to be solved by the present invention is to implement a range resolver processor (analogue) using an analog correlator to increase the accuracy and distance resolution, within 10 GHz bandwidth of less than 10 centimeters (cm) It is to provide a method for improving the distance resolution of a DS-UWB type short-range radar device that can represent accuracy.

One embodiment of the present invention for achieving the above object, by transmitting a high-frequency modulated PRBS signal generated by the system clock, and detected as a PRBS signal from the receiving end (Rx) signal, the distance resolution processor to measure the distance to the subject A method for improving distance resolution in a radar apparatus, comprising: a time difference? At a start point of PRBS of a transmission signal and a start point of PRBS of a reception signal; and a self-correlation function based on a time difference? A first step of calculating a value of Rz (τ)) and a second step of calculating a time difference τ of a maximum value of the autocorrelation function calculated in the first step as a time difference τ of a transmission signal and a reception signal; The auto-correlation function Rz (τ) is obtained in the period T of the original signal z (t) and the signal z (t + τ) and the original signal z (t), which are moved by the time τ. about,

This is a method to improve the distance resolution of DS-UWB short-range radar device.

According to the method of improving the distance resolution of the DS-UWB type short-range radar device according to the present invention, since the analog method using an analog correlator is implemented, an accuracy of less than ten centimeters (cm) can be obtained within 1 GHz bandwidth. It will be able to be extended to the application fields of short range radar for non-contact precision distance measurement, and will also be useful for automobile collision prevention, autonomous driving, automatic parking and machinery industry, shipbuilding industry and defense industry.

1 is a block diagram of a conventional DS-UWB radar apparatus.
2 is a block diagram of a DS-UWB type high precision short-range radar device according to the present invention.

Hereinafter, the configuration and operation of a method for improving distance resolution of a DS-UWB short-range radar device according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

The terms or words used in this specification and claims are not to be construed as limiting in their usual or dictionary meanings, and the inventors may properly define the concept of terms in order to best explain their invention in the best way possible. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention. Therefore, since the embodiments shown in the specification and the configuration shown in the drawings is only one of the most preferred embodiment of the present invention, it is understood that there may be various equivalents and modifications that can replace them at the time of the present application shall.

2 is a block diagram schematically showing the overall configuration of a DS-UWB system short-range radar apparatus according to an embodiment of the present invention, the radar apparatus according to an embodiment of the present invention generates a system clock serving as a reference signal A system clock generator 11, a phase locked loop 16 for generating a high frequency signal, a first clock converter 12 and a second clock converter 17 for frequency conversion, and a first PRBS pattern generator for generating a PRBS signal 13 and the second PRBS pattern generator 18, the transmitter mixer 14 and receiver mixer 19 for modulation / demodulation, the transmitter (Tx) bandpass filter 15 and the receiver (Rx) band for band filtering A pass filter 20, a low pass filter 21 for detecting the PRBS, a sampler 22, and a distance resolution processor 23 for calculating a distance from the subject by autocorrelation characteristics.

In addition, the radar apparatus according to another embodiment of the present invention, the vehicle communication unit 24 for communication with the vehicle controller, the key input unit 25 for the interface between the user and the system, the display unit for displaying the time difference value and the distance to the target At least one or more of (26) is comprised.

As shown in FIG. 2, the system clock generator 11 generates a system clock that is a reference signal for generating a high frequency signal and a data sequence to generate a phase locked loop (PLL) 16, a first clock converter 12, and a second clock. The clock converter 17 provides a reference signal.

Phase Locked Loop (16) generates a high frequency (RF) PLL signal using the system clock as a reference signal, and can generate hundreds of MHz to GHz.

The first clock converter 12 and the second clock converter 17 frequency-convert the system clock to generate a first clock signal and a second clock signal, respectively, and are controlled by the distance resolution processor 23 to correspond to the data transmission rate. The clock is provided to the first PRBS pattern generator 13 and the second PRBS pattern generator 18, respectively.

The first PRBS pattern generator 13 and the second PRBS pattern generator 18 are controlled by the distance resolution processor 23 and each of which is frequency converted in the first clock converter 12 and the second clock converter 17. Each pseudo clock random polynomial is applied to a clock signal to generate a PRBS signal having a maximum length. This PRBS signal is inconsistent and unpredictable, like noise.

The transmitter mixer 14 performs high frequency modulation by mixing the PRBS signal generated by the first PRBS pattern generator 13 with the high frequency PLL signal generated by the phase locked loop 16 to move the PRBS signal to the high frequency PLL signal band. do.

The first band pass filter 15 of the transmitting end Tx filters the high frequency modulated PRBS signal and transmits only a signal having a desired frequency band to the transmitting end Tx.

The second band pass filter 20 of the receiving end Rx filters the signal coming from the receiving end to receive only the signal of the desired frequency band and transmits the signal to the receiving end mixer 19.

The receiver mixer 19 receives the signal received through the second band pass filter 20 of the receiver, the high frequency PLL signal generated by the phase locked loop 16 and the PRBS signal generated by the second PRBS pattern generator 18. Mixing outputs a PRBS signal mixed with a high frequency (RF) signal.

The low pass filter 21 removes the high frequency (RF) signal from the signal mixed by the receiver mixer 19 and passes only the PRBS signal.

The sampler 22 samples the PRBS signal filtered by the low pass filter 21.

The distance resolution processor 23 controls the operation of each of the clock converters 12 and 17 and the PRBS pattern generators 13 and 18, and determines the autocorrelation function Rz (?) From the output signal of the sampler 22. The time difference between the transmission signal and the reception signal is calculated using the characteristic. The distance measurement algorithm mounted on the distance resolution processor 23 gives a time difference τ between the start time of the PRBS of the transmission signal and the start time of the PRBS of the received signal, and the autocorrelation function of the time difference τ between the transmission signal and the reception signal in the received signal. A first step of calculating a value of Rz (τ) and a time difference τ of the maximum value of the autocorrelation function calculated in the first step as a time difference τ of a transmission signal and a reception signal; In this case, the auto-correlation function Rz (τ) is obtained by comparing the original signal z (t) with the signal z (t + τ) and the original signal z (t) which is moved by the time τ. For the period T, one defined by Equation 1 below is used.

The distance resolution processor 23 calculates an autocorrelation function Rz (τ) for various time difference τ values of the transmission signal and the received signal, and searches for the time difference τ value at which the function value becomes the maximum. The resolution is determined as the minimum value of the time difference τ found. In particular, the distance resolution processor 23 used in the present invention can increase the distance resolution by calculating a function value in an interpolation method for the time existing between the found minimum time difference τ.

The vehicle communication unit 24 is connected by the distance resolution processor 23 to enable a communication interface between the system and the vehicle controller to transmit and receive data between the vehicle controller and the distance resolution processor 23.

The key input unit 25 is connected to the distance resolution processor 23 to process an interface between the user and the system.

The display unit 26 controls the display operation by the distance resolution processor 23, and displays the calculated time difference value and the distance to the target.

Referring to the operation of the DS-UWB short-range radar apparatus according to the present invention configured as described above are as follows.

First, the system clock generator 11 generates a system clock that is a reference signal for generating an RF signal and a data sequence for high frequency (RF) modulation, and fixes the first clock converter 12, the second clock converter 17, and a phase lock. The loop 16 provides a reference clock signal.

Each of these clock converters 12 and 17 converts the frequency of the system clock to provide clock signals corresponding to the data transfer rates to the PRBS pattern generators 13 and 18, and the phase locked loop 16 A high frequency signal is generated using a reference signal (System Clock) provided by the clock generator 11 to supply a high frequency PLL signal to each mixer 14 and 19 of a transmitter and a receiver, and typically generates from several hundred MHz to several tens of GHz. .

Each of the PRBS pattern generators 13 and 18 generates a PRBS signal that is inconsistent and unpredictable, such as noise, from the clock signal provided by each clock converter, and sends it to each of the mixers 14 and 19 of the transmitter and the receiver. Each of the PRBS pattern generators 13 and 18 generates an irregular signal of maximum length using a PRBS generating polynomial.

The PRBS signal and the high frequency PLL signal thus produced are supplied to the transmitter mixer 14 connected to the transmitter Tx, and the mixer 14 of the transmitter performs high frequency modulation on the PRBS signal using the property of multiplying the two signals. . That is, when the high frequency PLL signal and the PRBS signal are mixed by the transmitter mixer 14, the PRBS signal can move to the PLL frequency band. The high frequency modulated PRBS signal is a desired frequency through the band pass filter 15 of the transmitter. After filtering to the band is transmitted to the outside through the antenna of the transmitter (Tx).

In addition, the received signal received through the antenna of the receiver Rx is filtered to the desired frequency band through the band pass filter 20 of the receiver and then transmitted to the receiver mixer 19, in which the receiver signal and phase are received. The high frequency PLL signal provided from the fixed loop 16 and the PRBS signal provided from the second PRBS pattern generator 18 are mixed, and the PRBS signal mixed with the high frequency PLL signal is detected at the output thereof and provided to the low pass filter 21. .

The low pass filter 21 removes the high frequency signal from the mixed signal of the high frequency PLL signal and the PRBS signal to provide the sampler 22 after leaving only the PRBS signal, and the sampler 22 samples from the signal filtered through the LPF. Is carried out.

Finally, the distance resolution processor 23 calculates the time difference τ between the transmission signal and the reception signal using the property of Rz (τ), which is an autocorrelation function. When the time difference τ is given at the start of the PRBS and the autocorrelation function (Rz (τ)) is calculated for the time difference τ in the received signal, the time difference τ at the point at which the value becomes maximum is the time difference τ between the transmission signal and the received signal. Will be chosen. In this case, the distance resolution processor 23 calculates an autocorrelation function value for each of a plurality of time difference τ values, and finds a maximum value of the function value. The resolution of this distance resolution processor 23 is determined by the minimum value of the time difference τ value. Since this time difference value cannot be made infinitely small, the autocorrelation function value for the time values existing between the time difference τ values is calculated through the interpolation method. By using this, the resolution can be increased.

The autocorrelation function is a function of only the time difference τ, and multiplies and integrates the original signal z (t) with the signal z (t + τ) shifted by the time τ during the period T of the original signal z (t) to obtain an average over the period. For example, if τ = 0, Rz (τ) becomes Rz (0) and eventually becomes the square of the magnetic signal, so Rz (τ) becomes the largest value. As τ increases, z (t) and z (t + τ) become different values, and the integrated mean becomes smaller than Rz (0). The autocorrelation function Rz (τ) becomes a function of the time difference τ and the degree of correlation varies depending on the time difference.

In general, the maximum is τ = 0 and the minimum is τ = T / 2, and the autocorrelation function uses the autocorrelation function when the transmission and reception signals have a time difference, and Rz (τ) is maximum. τ becomes the time difference between the transmission signal and the reception signal. Therefore, using the autocorrelation function, the time difference can be found.

As described above, the present invention has been described by way of limited embodiments and drawings, but the present invention is not limited to the above-described embodiments, which can be variously modified and modified by those skilled in the art to which the present invention pertains. Modifications are possible. Accordingly, the spirit of the present invention should be understood only by the claims set forth below, and all equivalent or equivalent modifications thereof will belong to the scope of the present invention.

11: system clock generator 12,17: clock converter
13,18: PRBS pattern generator 14,19: mixer
15,20: band pass filter 16: phase locked loop
21 low pass filter 22 sampler
23: distance resolution processor 24: vehicle communication unit
25: key input unit 26: display unit

Claims (2)

In the method of improving the distance resolution in the radar apparatus for transmitting a high frequency modulated PRBS signal generated by the system clock, and detected as a PRBS signal from the receiving end signal, and measuring the distance to the subject through a distance resolution processor,
A first step of giving a time difference τ at the start time of the PRBS of the transmission signal and the start time of the PRBS of the reception signal, and calculating the autocorrelation function Rz (τ) based on the time difference τ of the transmission signal and the reception signal from the reception signal. ;
And a second step of calculating a time difference τ value at which the autocorrelation function value calculated in the first step is a maximum as a time difference τ value between the transmission signal and the reception signal.
The auto-correlation function Rz (τ) is based on the period z of the original signal z (t) and the signal z (t + τ) and the original signal z (t), which are moved by the time τ,

Method for improving the distance resolution of the DS-UWB type short-range radar device, characterized in that. The method of claim 1, wherein the second step,
The autocorrelation function Rz (τ) is calculated for various time difference τ values of the transmission signal and the received signal, and the time difference τ value is searched to maximize the function value. A method of improving the distance resolution of a DS-UWB short-range radar device, characterized in that the function value of time existing between the searched minimum time difference (τ) values is calculated by an interpolation method in order to increase the distance resolution determined by the minimum value.

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