KR20010063212A - Circuit for eliminating low frequency noise of fmcw radar - Google Patents

Abstract

PURPOSE: A low frequency noise exclusion circuit is provided to prevent the distortion and saturation of signals by eliminating noise signals included in signals outputted from IF amplifier. CONSTITUTION: A low frequency noise exclusion circuit(100) is composed of the third low pass filter(110) and an adder(120). The third pass filter(110) passes only low frequency noise signals, making middle frequency outputted from automatic gain controller(15) get feedback. The adder eliminates noise signals included in wireless frequency outputted from IF amplifier(27), after adding wireless frequency from IF amplifier(27) to low frequency noise signals. A logic block(12) creates continuous wave of voltage type and outputs continuous wave to a D/A convertor(13), when DSP(11) of a signal processing part(10) outputs globular wave. The D/A convertor(13) converts digital signals into analog signals and outputs the analog signals to the first low pass filter(14). The first low pass filter(14) passes only signals of band to want pass.

Description

Low frequency noise elimination circuit of FMC double U radar {CIRCUIT FOR ELIMINATING LOW FREQUENCY NOISE OF FMCW RADAR}

The present invention relates to a frequency modulated continuous wave (FMCW) radar, and more particularly, to a low frequency noise cancellation circuit of an FMCW radar for removing a low frequency noise signal from a signal input from a receiver.

In general, radar (Radar Detection and Ranging) is a sensor that detects the presence of objects at a distance beyond human visual field limits, and has all-weather functions regardless of weather conditions or day and night, and from a short distance to the horizon beyond the horizon. Because of the unique signal characteristics that can detect long-range objects, it is a completely different electromagnetic sensor than conventional methods.

Radar is an all-weather electronic eye that uses electromagnetic waves to see long-range targets. Early warning, port monitoring, as well as civil use, such as air navigation and control, earth and space exploration, meteorological observation, ship navigation, vehicle speed measurement, and collision avoidance. It is used for military purposes such as air defense, air defense, and missile guidance control.

These radars have various types of radars, which are classified according to radio wave types.

Radar is divided into continuous wave radar and pulse radar. Continuous wave radar is divided into Doppler radar, FMCW radar, and pulse radar is divided into pulse radar and pulse compression radar.

Unlike the pulse radar, the FMCW radar is a radar that simultaneously receives the reflected wave signals from the target while continuously transmitting the continuous wave signals. The continuous wave signal of this radar has the disadvantage of not knowing the distance to the target because there is no refraction of time other than phase, but it is very suitable for detecting the velocity to the moving target. In addition to the pulse radar has the advantage that can detect the target at close range.

As shown in FIG. 1, the FMCW radar includes a signal processor 10 and a transceiver 20.

When the square wave is output from the digital signal processing (DSP) 11 of the signal processor 10, the logic block 12 generates and outputs a continuous wave (CW) that is a triangular wave in the form of voltage.

Then, the D / A converter 13 converts the digital signal supplied from the logic block 12 into an analog signal, and the first low pass filter 14 of the analog band supplied from the D / A converter 13 Only pass the signal.

When the analog signal of a predetermined band is input to the voltage controlled oscillator 21 of the transceiver 20 by the first low pass filter 14, the voltage controlled oscillator 21 is driven to perform radio frequency modulation as shown in FIG. 2. The radio frequency is radiated outward through the transmission antenna 23.

When the radio frequency is received from the receiving antenna 24 of the transceiver 20, the low noise amplifier 25 amplifies the radio frequency by a predetermined level and supplies it to the mixer 26. The mixer 26 generates an intermediate frequency by mixing the radio frequency supplied from the directional coupler 22 with the signal supplied from the low noise amplifier 25. The intermediate frequency generated by the mixer 26 is amplified by a predetermined level through the IF amplifier 27 and then input to the automatic gain adjuster 15 of the signal processor 10.

The auto gain controller 15 adjusts and outputs the gain of the input intermediate frequency under the control of the logic block 12, and the second low pass filter 16 outputs only the frequencies of the desired band among the input intermediate frequencies. Output to converter 17.

The A / D converter 17 converts the input intermediate frequency into a digital signal and outputs it to the logic block 12. The logic block 12 transfers it to the DSP 11, and the DSP 11 stores the digital signal in memory. After storing in (18), the distance to the target is detected by the Fast Fourier Transform (FFT) technique.

However, in the conventional FMCW radar, when the reception gain is increased for the target detection, as shown in FIG. 3, the saturation phenomenon is generated by the low frequency noise signal included in the intermediate frequency, resulting in distortion of the signal. If it is small, the far-field signal is weak and there is a problem that can not be detected.

FFT processing of the received signal detected in the rising and falling sections of the continuous wave and the received signal in which the saturation phenomenon occurs has resulted in distortion of the processing signal, resulting in another problem of deteriorating the reliability of the system due to misunderstanding of the detection information.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to feed back some of the intermediate frequencies output from the automatic gain regulator and input the filtered low frequency noise signal component to the adder, which is included in the signal output directly from the IF amplifier. By eliminating low frequency noise signal components, it is possible to prevent distortion and saturation of the signal, thereby increasing the reliability of the system.

1 is a block diagram schematically showing a conventional FMCW radar

2 is a waveform diagram illustrating an output waveform of part a of FIG. 1;

3 is a waveform diagram illustrating an output waveform of part b of FIG. 1;

4 is a block diagram schematically showing an FMCW radar including a low frequency noise cancellation circuit according to the present invention.

5 is a waveform diagram illustrating an output waveform of part a of FIG. 4;

6 is a waveform diagram illustrating an output waveform of part b of FIG. 4;

<Explanation of symbols for main parts of the drawings>

10 signal processing unit 11 DSP

12: logic block 13: A / D converter

14: first low pass filter 15: automatic gain regulator

16: second low pass filter 17: D / A converter

18: memory 20: transceiver

21: voltage controlled oscillator 22: directional coupler

23: transmitting antenna 24: receiving antenna

25 low noise amplifier 26 mixer

27: IF amplifier 100: low frequency noise cancellation circuit

110: third low pass filter 120: adder

Features of the low frequency noise cancellation circuit of the FMCW radar of the present invention for achieving the above object,

A signal processor for generating a digital signal, converting the analog signal into an analog signal, and outputting the converted analog signal into a digital signal to calculate a distance to the target, and transmitting an analog signal supplied from the signal processor, and reflecting the target signal In the FMCW radar composed of a transceiver for receiving an analog signal,

After feeding back the intermediate frequency supplied from the transceiver, only the low frequency noise signal is passed therethrough, and the sum of the intermediate frequency supplied from the transceiver to the signal processing unit and the low frequency noise included in the intermediate frequency supplied from the transceiver And a low frequency noise canceling circuit for canceling the signal.

Here, the low frequency noise cancellation circuit,

A low pass filter that feeds only a low frequency noise signal by feeding back an intermediate frequency whose gain is adjusted by the signal processor;

And an adder configured to add the radio frequency supplied from the transceiver and the low frequency noise signal supplied from the low pass filter to remove the low frequency noise signal included in the intermediate frequency output from the transceiver.

Hereinafter, the configuration and operation of the low frequency noise cancellation circuit of the FMCW radar according to the present invention will be described in detail with reference to FIGS. 4 to 6. In FIG. 4, the same code | symbol is attached | subjected about the same part as the conventional FMCW radar shown in FIG. 1, and the duplication description is abbreviate | omitted.

4 is a block diagram schematically showing an FMCW radar including a low frequency noise cancellation circuit according to the present invention, FIG. 5 is a waveform diagram showing an output waveform of part a of FIG. 4, and FIG. 6 is a block diagram of part b of FIG. 4. A waveform diagram showing an output waveform.

Referring to FIG. 4, the low frequency noise cancellation circuit 100 includes a third low pass filter 110 and an adder 120.

The third low pass filter 110 feeds back only the low frequency noise signal by feeding back the intermediate frequency output from the automatic gain adjuster 15.

The adder 120 sums the radio frequency supplied from the IF amplifier 27 and the low frequency noise signal supplied from the third low pass filter 110 to obtain a low frequency noise signal included in the radio frequency output from the IF amplifier 27. Remove it.

Hereinafter, the operation of the low frequency noise canceling circuit according to the present invention will be described in more detail with reference to FIGS. 4 to 6.

When the square wave is output from the DSP 11 of the signal processing unit 10, the logic block 12 generates and outputs a continuous wave, which is a triangular wave in the form of voltage, and outputs it to the D / A converter 13.

Then, when the D / A converter 13 converts the digital signal into an analog signal and outputs it to the first low pass filter 14, the first low pass filter 14 passes only signals of a desired band.

When an analog signal of a predetermined band is input to the voltage controlled oscillator 21 of the transceiver 20 by the first low pass filter 14, the voltage controlled oscillator 21 starts driving and transmits a frequency-modulated radio frequency to the transmitting antenna. Transmit via 23.

When a radio frequency is received from the reception antenna 24 of the transceiver 20, the radio frequency is amplified by the low noise amplifier 25 and then supplied to the mixer 26. The mixer 26 generates an intermediate frequency by mixing the radio frequency supplied from the directional coupler 22 with the signal supplied from the low noise amplifier 25. The intermediate frequency generated by the mixer 26 is amplified by a predetermined level through the IF amplifier 27 and then input to the automatic gain controller 15 of the signal processor 10 through the adder 120 of the low frequency noise removing circuit 100. do.

The automatic gain regulator 15 then adjusts and outputs the gain of the input intermediate frequency under the control of the logic block 12.

On the other hand, when the intermediate frequency is output from the automatic gain regulator 15, it is fed back to the third low pass filter 110 of the low frequency noise canceling circuit 100 with a slight phase delay, and the third low pass filter 110. Only the low frequency noise signal passes through and is input to the negative end of the adder 120.

The adder 120 then adds the low frequency noise signal supplied from the third low pass filter 110 at the intermediate frequency supplied from the mixer 26 to output the intermediate frequency from which the low frequency noise signal has been removed. In more detail, when the signal fed back from the automatic gain controller 15 passes through the third low pass filter 110, the waveform shown in FIG. 5 is output from the third low pass filter 110. When this is added to the waveform of FIG. 2, an intermediate frequency from which the low frequency noise signal is removed is output as shown in FIG. 6.

When the intermediate frequency from which the low frequency noise signal is removed is output from the automatic gain adjuster 15 and input to the second low pass filter 16, the second low pass filter 16 only the frequency of the desired band among the input intermediate frequencies. Output to A / D converter 17 is performed.

The A / D converter 17 converts the input intermediate frequency into a digital signal and outputs it to the logic block 12. The logic block 12 transmits it to the DSP 11, and the DSP 11 transmits the digital signal. After storing in the memory 18, the distance to the target is detected by the FFT technique.

Therefore, the present invention feeds back some of the intermediate frequencies output from the automatic gain regulator, filters only the low frequency noise signal, inputs it to the adder, and removes the low frequency noise signal included in the signal directly output from the IF amplifier.

As described above, according to the low frequency noise cancellation circuit of the FMCW radar according to the present invention, a part of the intermediate frequencies output from the automatic gain regulator is fed back to input the filtered low frequency noise signal to the adder and included in the signal output directly from the IF amplifier. By eliminating the low frequency noise signal, it is possible to prevent distortion and saturation of the signal, thereby increasing the reliability of the system.

Claims (2)

A signal processor for generating a digital signal, converting the analog signal into an analog signal, and outputting the converted analog signal into a digital signal to calculate a distance to the target, and transmitting an analog signal supplied from the signal processor, and reflecting the target signal In the FMCW radar composed of a transceiver for receiving an analog signal, After feeding back the intermediate frequency supplied from the transceiver, only the low frequency noise signal is passed therethrough, and the sum of the intermediate frequency supplied from the transceiver to the signal processing unit and the low frequency noise included in the intermediate frequency supplied from the transceiver A low frequency noise canceling circuit of a FMCW radar, characterized by including a low frequency noise canceling circuit for canceling a signal. The method of claim 1, The low frequency noise cancellation circuit, A low pass filter that feeds only a low frequency noise signal by feeding back an intermediate frequency whose gain is adjusted by the signal processor; And an adder for summing a low frequency noise signal supplied from the low pass filter and a radio frequency supplied from the transceiver to remove a low frequency noise signal included in an intermediate frequency output from the transceiver. Low frequency noise cancellation circuit.