Radar device and gain adjustment method

Abstract

[Problem] To more appropriately adjust the gain of a reception signal. [Solution] This radar device comprises: a transmission unit that transmits a transmission signal having a frequency that varies over time; a reception unit that receives, as a reception signal, radio waves resulting from the reflection back of the transmission signal by an object; a frequency conversion unit that generates an in-phase signal and a quadrature signal on the basis of the reception signal; an amplitude signal generation unit that generates an in-phase amplitude signal indicating the amplitude of the in-phase signal and a quadrature amplitude signal indicating the amplitude of the quadrature signal; a maximum value selection unit that selects, as a maximum value signal, the signal from among the in-phase amplitude signal and the quadrature amplitude signal that has the highest level; and a gain adjustment unit that adjusts the gain of the reception signal on the basis of the maximum value signal.

Description

Technical Field

[0001] The present invention relates to a radar device and a gain adjustment method.

Background Art

[0002] Conventionally, in a radar device using the FM-CW (Frequency Modulated Continuous Wave) method, a technique for adjusting the gain of a received signal is known. For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2001-228240) discloses a received signal amplification device as follows. That is, the received signal amplification device is a received signal amplification device of an FMCW radar that transmits radio waves, receives reflected waves from a target, and obtains the distance to the target or the relative speed with the target. The received signal amplification device includes a plurality of amplifiers connected in cascade to amplify the received signal, and output selection means for selecting, from the amplifiers, the amplifier whose output voltage matches the input voltage range of the A / D conversion means and whose level is the highest, and guiding the output thereof to the A / D conversion means.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The technology described in Patent Document 1 adjusts the gain of the received signal by selectively using one or more amplifiers from among several amplifiers, making it difficult to finely adjust the gain of the received signal. Furthermore, the technology described as prior art in Patent Document 1, which controls the gain of the received signal using an AGC (Auto Gain Control) circuit, may not be able to properly adjust the gain of the received signal. When the gain of the received signal cannot be properly adjusted, for example, the strength of the received signal after gain adjustment may become excessively high. A technology that can adjust the gain of the received signal more appropriately than such conventional technologies is desired.

[0005] This invention was made to solve the above-mentioned problems, and its objective is to provide a radar device and a gain adjustment method that can more appropriately adjust the gain of the received signal. [Means for solving the problem]

[0006] (1) In order to solve the above problems, a radar device according to one aspect of the present invention comprises: a transmitting unit that transmits a transmission signal whose frequency is changed over time; a receiving unit that receives radio waves that have been reflected back by an object from the transmitted signal as a received signal; a frequency conversion unit that generates a common-mode signal and a quadrature signal based on the received signal; an amplitude signal generation unit that generates a common-mode amplitude signal indicating the amplitude of the common-mode signal and a quadrature amplitude signal indicating the amplitude of the quadrature signal; a maximum value selection unit that selects the one with the larger level among the common-mode amplitude signal and the quadrature amplitude signal as the maximum value signal; and a gain adjustment unit that adjusts the gain of the received signal based on the maximum value signal.

[0007] In this configuration, a common-mode signal and a quadrature signal are generated based on the received signal, and the gain of the received signal is adjusted based on the maximum value signal, which is selected as the larger of the two amplitude signals (common-mode amplitude signal and quadrature amplitude signal). This allows for adjustment of the gain of the received signal based on the larger amplitude of the two signals, even when the amplitudes of the common-mode signal and the quadrature signal differ due to the gain of each signal path. This prevents the strength of the received signal from becoming excessively high after gain adjustment. Therefore, the gain of the received signal can be adjusted more appropriately. Furthermore, the gain of the received signal can be adjusted according to the amplitude of the common-mode and quadrature signals, which have reduced interference from the transmitted signal to the received signal. Moreover, the process of generating common-mode and quadrature amplitude signals and selecting the maximum value signal can be realized with a simple circuit configuration consisting of general-purpose components such as operational amplifiers, resistors, capacitors, and diodes.

[0008] (2) The radar device may further include a low-pass filter that receives the maximum value signal and attenuates components of the maximum value signal that are above a predetermined frequency, and the gain adjustment unit may be configured to adjust the gain of the received signal based on the maximum value signal that has passed through the low-pass filter.

[0009] With this configuration, for example, the gain of the received signal can be adjusted based on the maximum value signal after ripple has been removed and smoothed, allowing for more precise gain adjustment according to the level of the received signal.

[0010] (3) The amplitude signal generation unit, the maximum value selection unit, the low-pass filter, and the gain adjustment unit may be configured as analog circuits.

[0011] This configuration allows for gain adjustment with higher responsiveness to fluctuations in the received signal level compared to configurations that use digital circuits to adjust the gain of the received signal.

[0012] (4) The frequency conversion unit may generate the in-phase signal and the orthogonal signal in the baseband band, and the amplitude signal generation unit may generate the in-phase amplitude signal indicating the amplitude of the in-phase signal in the baseband band and the orthogonal amplitude signal indicating the amplitude of the orthogonal signal in the baseband band.

[0013] In this configuration, by adjusting the gain using common-mode and quadrature signals in the baseband band, the influence of interference from the transmitted signal on the received signal is reduced. The gain of the received signal can be adjusted according to the amplitude of the common-mode and quadrature signals, thereby suppressing malfunctions in the gain control.

[0014] (5) The radar device may further include an A / D conversion unit that digitally converts the in-phase signal and the quadrature signal, and a data conversion unit that converts the in-phase signal and the quadrature signal digitally converted by the A / D conversion unit into amplitude data indicating the relationship between distance and amplitude.

[0015] This configuration allows the radar device to detect the distance between itself and an object with a wide dynamic range, based on the transmitted signal and the received signal with adjusted gain.

[0016] (6) Furthermore, an embodiment of the present invention is a gain adjustment method for a radar device, comprising: transmitting a transmission signal whose frequency is changed over time; receiving a radio wave that has been reflected back by an object from the transmission signal as a received signal; generating a common-mode signal and a quadrature signal based on the received signal; generating a common-mode amplitude signal that shows the amplitude of the common-mode signal and a quadrature amplitude signal that shows the amplitude of the quadrature signal; selecting the signal with the larger level of the common-mode amplitude signal and the quadrature amplitude signal as the maximum value signal; and adjusting the gain of the received signal based on the maximum value signal.

[0017] In this way, by generating a common-mode signal and a quadrature signal based on the received signal, and adjusting the gain of the received signal based on the maximum value signal, which is selected as the larger of the two amplitude signals (the common-mode amplitude signal and the quadrature amplitude signal), when the amplitudes of the common-mode signal and the quadrature signal differ due to the gain of each signal path, the gain of the received signal can be adjusted based on the amplitude of the larger of the two amplitude signals, thereby suppressing the excessive increase in the strength of the received signal after gain adjustment. Therefore, the gain of the received signal can be adjusted more appropriately. Furthermore, the gain of the received signal can be adjusted according to the magnitude of the amplitudes of the common-mode signal and the quadrature signal, which have reduced interference from the transmitted signal to the received signal. Moreover, the process of generating a common-mode amplitude signal and a quadrature amplitude signal and selecting the maximum value signal can be realized with a simple circuit configuration consisting of general-purpose components such as operational amplifiers, resistors, capacitors, and diodes. [Brief explanation of the drawing]

[0018] [Figure 1] Figure 1 shows the configuration of a radar device according to an embodiment of the present invention. [Figure 2] Figure 2 shows the configuration of the adjustment unit in a radar device according to an embodiment of the present invention. [Figure 3] Figure 3 shows an example of a signal received by the amplitude signal generation unit in a radar device according to an embodiment of the present invention. [Figure 4] Figure 4 shows an example of a signal output by the amplitude signal generation unit in a radar device according to an embodiment of the present invention. [Figure 5] Figure 5 shows an example of a maximum value signal output by the maximum value selection unit in a radar device according to an embodiment of the present invention. [Figure 6] Figure 6 shows an example of the maximum value signal output by the LPF (Low Pass Filter) in a radar device according to an embodiment of the present invention. [Figure 7]FIG. 7 is a diagram showing an example of a signal output from a frequency conversion unit in a radar apparatus according to an embodiment of the present invention. [Figure 8] FIG. 8 is a diagram showing an example of a circuit configuration of an adjustment unit in a radar apparatus according to an embodiment of the present invention. [Figure 9] FIG. 9 is a diagram for explaining the operation of a circuit of an adjustment unit in a radar apparatus according to an embodiment of the present invention. [Figure 10] FIG. 10 is a diagram for explaining the operation of a circuit of an adjustment unit in a radar apparatus according to an embodiment of the present invention. [Figure 11] FIG. 11 is a flowchart defining an example of an operation procedure when a radar apparatus according to an embodiment of the present invention adjusts the gain of a received signal.

Embodiments for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and their descriptions will not be repeated. In addition, at least a part of the embodiments described below may be arbitrarily combined.

[0020] [Configuration and Basic Operation] [Radar Apparatus] FIG. 1 is a diagram showing the configuration of a radar apparatus according to an embodiment of the present invention. Referring to FIG. 1, a radar apparatus 300 includes a radar unit 201 and a display processing unit 202. The radar unit 201 includes a signal generation unit 110, a transmission unit 120, a transmission antenna 130, a reception antenna 140, a reception unit 150, a frequency conversion unit 170, an A / D (Analog to Digital) conversion unit 180, a signal processing unit 190, and an adjustment unit 100. The signal processing unit 190 is an example of a data conversion unit. The radar apparatus 300 is a radar apparatus of the FM-CW method and is mounted on a ship, for example. The radar apparatus 300 performs a process of displaying an echo image indicating the presence or absence of a target in a detection target area, which is an area monitored by the ship, and the distance between the radar apparatus 300 and the target, on a display device (not shown).

[0021] The radar unit 201 outputs echo data to the display processing unit 202 that shows the detection results of targets in the divided target areas, which are regions obtained by dividing the detection target area into multiple parts. The transmitting antenna 130 and the receiving antenna 140 rotate so that the azimuth angle of the direction of radiation of radio waves from the transmitting antenna 130 changes by a predetermined angle at each predetermined sweep period T. The radar unit 201 outputs echo data for each of the multiple divided target areas at each sweep period T to the display processing unit 202.

[0022] The display processing unit 202 performs processing to display echo images in the detection target area on the display device, based on multiple echo data received from the radar unit 201.

[0023] <Radar Section> The signal generation unit 110 repeatedly generates an analog signal of a predetermined pattern and outputs it to the transmission unit 120. More specifically, during the sweep period T, the signal generation unit 110 outputs to the transmission unit 120 an analog signal whose frequency increases by a predetermined amount per unit time, generated using, for example, an FM-CW modulation scheme. Specifically, for example, the signal generation unit 110 includes a voltage generation unit and a VCO (Voltage-Controlled Oscillator). During the sweep period T, the voltage generation unit generates an FM modulated voltage whose magnitude increases at a constant rate and outputs it to the VCO. The VCO generates an analog signal having a frequency corresponding to the magnitude of the FM modulated voltage received from the voltage generation unit and outputs it to the transmission unit 120.

[0024] The transmitting unit 120 transmits a transmission signal whose frequency is changed over time. More specifically, during the sweep period T, the transmitting unit 120 generates an RF (Radio Frequency) band transmission signal based on the analog signal received from the signal generation unit 110, and outputs the generated RF band transmission signal to the area to be divided via the transmitting antenna 130, which rotates in conjunction with the rotation of the radar unit 201. The transmitting unit 120 also outputs the generated RF band transmission signal to the frequency conversion unit 170. Specifically, for example, the transmitting unit 120 includes a frequency multiplier and a power amplifier. The frequency multiplier generates an RF band transmission signal based on the analog signal received from the signal generation unit 110, and outputs the generated transmission signal to the power amplifier and the frequency conversion unit 170. In the transmitting unit 120, the power amplifier amplifies the transmission signal received from the frequency multiplier, and outputs the amplified transmission signal to the area to be divided via the transmitting antenna 130.

[0025] The receiving unit 150 receives radio waves that have been reflected back by an object from the transmitted signal as a received signal. More specifically, the receiving unit 150 receives the RF band reflected signal, which is the signal that has been reflected by an object in the area to be divided from the transmitted signal transmitted from the transmitting antenna 130, via the receiving antenna 140 which rotates in conjunction with the rotation of the radar unit 201. For example, the receiving unit 150 amplifies the received RF band received signal and outputs it to the frequency conversion unit 170. More specifically, the receiving unit 150 includes a variable gain amplifier. The variable gain amplifier amplifies the received signal received via the receiving antenna 140 and outputs the amplified received signal to the frequency conversion unit 170. The variable gain amplifier changes its gain according to the control voltage received from the adjustment unit 100.

[0026] The receiving unit 150 may also be configured to attenuate the received RF band signal and output it to the frequency conversion unit 170. In this case, the receiving unit 150 includes a low-noise amplifier and a variable-gain attenuator instead of a variable-gain amplifier. The low-noise amplifier amplifies the received signal received via the receiving antenna 140. The variable-gain attenuator attenuates the received signal amplified by the low-noise amplifier and outputs the attenuated received signal to the frequency conversion unit 170. The variable-gain attenuator changes its gain, i.e., the attenuation rate, according to the control voltage received from the adjustment unit 100.

[0027] The frequency conversion unit 170 generates an I signal Si and a Q signal Sq based on the received signal received by the receiving unit 150. For example, the frequency conversion unit 170 generates a baseband I signal Si and a Q signal Sq. The I signal Si is an example of a common-mode signal. The Q signal Sq is an example of a quadrature signal. The I signal Si and the Q signal Sq are signals having a frequency component that is the difference between the frequency component of the transmitted signal transmitted by the transmitting unit 120 and the frequency component of the received signal received by the receiving unit 150. More specifically, the frequency conversion unit 170 includes two mixers. A branching unit (not shown) branches the transmitted signal output from the transmitting unit 120 and adds a 90° phase difference to the branched transmitted signals before outputting them to each mixer in the frequency conversion unit 170. Another branching unit (not shown) branches the received signal output from the receiving unit 150 and outputs it to each mixer in the frequency conversion unit 170. The two mixers in the frequency conversion unit 170 multiply the transmitted signal and the received signal, respectively, to generate a baseband beat signal Sbb consisting of a pair of I signal Si and Q signal Sq, and output it to the adjustment unit 100 and the A / D conversion unit 180. For example, the frequency conversion unit 170 outputs the beat signal Sbb, from which low-frequency and DC components have been removed by a capacitor, to the adjustment unit 100 and the A / D conversion unit 180.

[0028] The adjustment unit 100 performs AGC (Automatic Gain Control) on the variable gain amplifier in the receiving unit 150 based on the beat signal Sbb received from the frequency conversion unit 170. For example, the adjustment unit 100 performs IAGC (Instantaneous Auto Gain Control) on the variable gain amplifier. More specifically, the adjustment unit 100 generates a control voltage based on the beat signal Sbb received from the frequency conversion unit 170 and adjusts the gain of the received signal by feeding back the generated control voltage to the variable gain amplifier. Details of the adjustment unit 100 will be described later.

[0029] The A / D conversion unit 180 digitally converts the I signal Si and the Q signal Sq. Specifically, the A / D conversion unit 180 converts the analog beat signal Sbb received from the frequency conversion unit 170 into a beat signal SD, which is a digital signal consisting of a pair of I signals Si and Q signals Sq. More specifically, the A / D conversion unit 180 generates N beat signals SD, each consisting of N pairs of I signals Si and N pairs of Q signals Sq, by sampling at a predetermined sampling frequency during each sweep period T, and outputs them to the signal processing unit 190. N is an integer greater than or equal to 2.

[0030] The signal processing unit 190 converts the I signal Si and Q signal Sq, which have been digitally converted by the A / D conversion unit 180, into amplitude data DS, which shows the relationship between distance d and amplitude. That is, the signal processing unit 190 converts the beat signal SD received from the A / D conversion unit 180 into amplitude data DS, which shows the relationship between distance d from the radar device 300 and amplitude. More specifically, for each sweep period T, the signal processing unit 190 receives N beat signals SD from the A / D conversion unit 180, each consisting of N sets of I signals Si and N Q signals Sq, and converts the beat signals SD from complex voltage to actual signal voltage by calculating the sum of the squares of the I signals Si and Q signals Sq for each set. The signal processing unit 190 then generates a power spectrum by performing processes such as window function processing and FFT processing on the beat signals SD converted to actual signal voltage. The signal processing unit 190 generates amplitude data DS by performing processes such as multiplying the frequency in the generated power spectrum by a predetermined coefficient C to convert the frequency to distance. The signal processing unit 190 then generates echo data by logarithmically transforming the absolute value of the generated amplitude data DS, and outputs the generated echo data to the display processing unit 202.

[0031] The radar device 300 may also be configured to include a single antenna that functions as both a transmitting antenna 130 and a receiving antenna 140, instead of the transmitting antenna 130 and the receiving antenna 140. In this case, for example, the transmitting unit 120 transmits the transmission signal to the area to be divided via the circulator and the antenna. Also, for example, the receiving unit 150 receives the reception signal via the antenna and the circulator.

[0032] <Display Processing> The display processing unit 202 generates integrated data, which is the echo data for the detection target area, based on the echo data for each segmented area received from the signal processing unit 190, and then processes the display of the echo image for the detection target area on a display device (not shown) based on the generated integrated data.

[0033] (adjustment section) Figure 2 shows the configuration of the adjustment unit in a radar device according to an embodiment of the present invention. Referring to Figure 2, the adjustment unit 100 includes an amplitude signal generation unit 10, a maximum value selection unit 20, a low-pass filter (LPF) 30, and a gain adjustment unit 40.

[0034] (amplitude signal generation section) The amplitude signal generation unit 10 generates an amplitude signal Smi, which represents the amplitude of the I signal Si, and an amplitude signal Smq, which represents the amplitude of the Q signal Sq. For example, the amplitude signal generation unit 10 generates an amplitude signal Smi, which represents the amplitude of the I signal Si in the baseband band, and an amplitude signal Smq, which represents the amplitude of the Q signal Sq in the baseband band. The amplitude signal Smi is an example of an in-phase amplitude signal. The amplitude signal Smq is an example of an orthogonal amplitude signal.

[0035] Figure 3 shows an example of a signal received by the amplitude signal generation unit in a radar device according to an embodiment of the present invention. In Figure 3, the solid line represents the I signal Si, and the dashed line represents the Q signal Sq.

[0036] Figure 4 shows an example of a signal output by the amplitude signal generation unit in a radar device according to an embodiment of the present invention. In Figure 4, the solid line represents the amplitude signal Smi, and the dashed line represents the amplitude signal Smq.

[0037] Referring to Figures 3 and 4, for example, the amplitude signal generation unit 10 receives the baseband I signal Si and Q signal Sq output from the frequency conversion unit 170, and outputs an amplitude signal Smi, which represents the absolute value of the level of the received I signal Si, and an amplitude signal Smq, which represents the absolute value of the level of the received Q signal Sq, to ​​the maximum value selection unit 20.

[0038] More specifically, the amplitude signal generation unit 10 outputs the amplitude signal Smi, which is the full-wave rectified waveform of the I signal Si, and the amplitude signal Smq, which is the full-wave rectified waveform of the Q signal Sq, to ​​the maximum value selection unit 20.

[0039] The radar unit 201 may also be configured to include an offset application circuit (not shown). This offset application circuit receives the I signal Si and Q signal Sq output from the frequency conversion unit 170, applies a predetermined level of offset voltage Vo to the received I signal Si and Q signal Sq, and outputs them to the adjustment unit 100 and the A / D conversion unit 180. This allows, for example, a unipolar A / D converter to be used as the A / D conversion unit 180.

[0040] In this case, the amplitude signal generation unit 10 receives the baseband I signal Si and Q signal Sq output from the offset application circuit and outputs an amplitude signal Smi, which represents the absolute value of the level of the received I signal Si, and an amplitude signal Smq, which represents the absolute value of the level of the received Q signal Sq, to ​​the maximum value selection unit 20.

[0041] (Maximum value selection section) The maximum value selection unit 20 selects the one with the higher level between the amplitude signal Smi and the amplitude signal Smq as the maximum value signal Smax.

[0042] Figure 5 shows an example of a maximum value signal output by the maximum value selection unit in a radar device according to an embodiment of the present invention.

[0043] Referring to Figure 5, the maximum value selection unit 20 outputs the maximum value signal Smax, obtained by taking the maximum value of the amplitude signals Smi and Smq received from the amplitude signal generation unit 10, to the LPF 30.

[0044] (LPF) The LPF30 receives a maximum value signal Smax and attenuates the components of the maximum value signal Smax that are above a predetermined frequency.

[0045] Figure 6 shows an example of the maximum value signal output by the LPF in a radar device according to an embodiment of the present invention.

[0046] Referring to Figure 6, the LPF 30 filters the maximum value signal Smax received from the maximum value selection unit 20, and outputs the maximum value signal Fmax, which is a smoothed signal with ripple removed, to the gain adjustment unit 40.

[0047] The level of the maximum value signal Fmax output by the LPF30 is close to the peak voltage of the sinusoidal wave when the I signal Si and Q signal Sq received by the amplitude signal generation unit 10 from the frequency conversion unit 170 are sinusoidal waves. Furthermore, the level of the maximum value signal Fmax is proportional to the levels of the I signal Si and Q signal Sq received by the amplitude signal generation unit 10 from the frequency conversion unit 170.

[0048] (Gain adjustment section) The gain adjustment unit 40 adjusts the gain of the received signal based on the maximum value signal Smax. For example, it adjusts the gain of the received signal based on the maximum value signal Fmax after passing through the LPF 30.

[0049] More specifically, the gain adjustment unit 40 generates a control voltage corresponding to the level of the maximum value signal Fmax received from the LPF 30, and outputs the generated control voltage to the variable gain amplifier in the receiving unit 150.

[0050] For example, the gain adjustment unit 40 includes an integrator utilizing an operational amplifier. This integrator receives a maximum value signal Fmax at its non-inverting input terminal, a predetermined level reference voltage Vref at its inverting input terminal, and outputs a control voltage from its output terminal. For example, the reference voltage Vref is preset based on the dynamic range of the A / D conversion unit 180.

[0051] Figure 7 shows an example of a signal output by a frequency conversion unit in a radar device according to an embodiment of the present invention. In Figure 7, the solid line represents the I signal Si output from the frequency conversion unit 170 to the A / D conversion unit 180 in the radar device 300, and the dashed line represents the I signal Si output from the frequency conversion unit 170 to the A / D conversion unit 180 in a radar device that does not have an adjustment unit 100.

[0052] Referring to Figure 7, in a radar system without an adjustment unit 100, the level of the received signal received via the receiving antenna 140 increases, which may cause a beat signal Sbb that does not fit the dynamic range of the A / D conversion unit 180 to be output from the frequency conversion unit 170 to the A / D conversion unit 180.

[0053] In contrast, in the radar device 300, the adjustment unit 100 performs IAGC (Integrated A / D Correction Gauge), so that the level of the beat signal Sbb output from the frequency conversion unit 170 to the A / D conversion unit 180 converges to the level of the reference voltage Vref. Therefore, even if the level of the received signal increases, the level of the beat signal Sbb output from the frequency conversion unit 170 to the A / D conversion unit 180 can be adjusted to match the dynamic range of the A / D conversion unit 180.

[0054] (Circuit configuration) Figure 8 shows an example of the circuit configuration of the adjustment unit in a radar device according to an embodiment of the present invention. Figure 8 shows the circuit configuration of the amplitude signal generation unit 10, the maximum value selection unit 20, and the LPF 30.

[0055] Referring to Figure 8, the amplitude signal generation unit 10, the maximum value selection unit 20, and the LPF 30 are all composed of analog circuits. More specifically, the amplitude signal generation unit 10 and the maximum value selection unit 20 have input terminals T1 and T2, resistors R1 to R10, diodes D1 to D6, and operational amplifiers OP1 to OP4. The LPF 30 has a resistor R11, a capacitor C1, and an output terminal T3. For example, the resistance values ​​of resistors R1 to R10 are the same.

[0056] Input terminal T1 receives the I signal Si output from the frequency conversion unit 170. Input terminal T2 receives the Q signal Sq output from the frequency conversion unit 170. Output terminal T3 outputs the maximum value signal Fmax to the gain adjustment unit 40.

[0057] Input terminal T1 is connected to the first terminal of resistor R1. Input terminal T2 is connected to the first terminal of resistor R6.

[0058] The second terminal of resistor R1 is connected to the first terminal of resistor R2, the inverting input terminal of op-amp OP1, and the first terminal of resistor R3. The non-inverting input terminal of op-amp OP1 is connected to ground. The second terminal of resistor R2 is connected to the first terminal of resistor R4, and the anode of diode D1. The cathode of diode D1 is connected to the output terminal of op-amp OP1, and the anode of diode D2. The second terminal of resistor R4 is connected to the first terminal of resistor R5, and the inverting input terminal of op-amp OP2. The second terminal of resistor R3 is connected to the cathode of diode D2, and the non-inverting input terminal of op-amp OP2. The output terminal of op-amp OP2 is connected to the anode of diode D3.

[0059] The second terminal of resistor R6 is connected to the first terminal of resistor R7, the inverting input terminal of op-amp OP3, and the first terminal of resistor R8. The non-inverting input terminal of op-amp OP3 is connected to ground. The second terminal of resistor R7 is connected to the first terminal of resistor R9, and the anode of diode D4. The cathode of diode D4 is connected to the output terminal of op-amp OP3, and the anode of diode D5. The second terminal of resistor R9 is connected to the first terminal of resistor R10, and the inverting input terminal of op-amp OP4. The second terminal of resistor R8 is connected to the cathode of diode D5, and the non-inverting input terminal of op-amp OP4. The output terminal of op-amp OP4 is connected to the anode of diode D6.

[0060] The second terminal of resistor R5 is connected to the cathode of diode D3, the second terminal of resistor R10 is connected to the cathode of diode D6, and the first terminal of resistor R11 is connected to the first terminal of resistor R11. The second terminal of resistor R11 is connected to the first terminal of capacitor C1 and the output terminal T3. The first terminal of capacitor C1 is connected to ground.

[0061] Figure 9 is a diagram illustrating the operation of the adjustment section circuit in a radar device according to an embodiment of the present invention. Figure 9 shows the operation of the circuit in the amplitude signal generation section 10 and the maximum value selection section 20 when the potentials of node N1 at the first end of resistor R1 and node N2 at the first end of resistor R6 are positive.

[0062] Referring again to Figure 8, when the potential V1 at node N1 of the first end of resistor R1 and the potential V2 at node N2 of the first end of resistor R6 are positive, diodes D1 and D4 conduct, and diodes D2 and D5 do not conduct. Therefore, when V1 and V2 are positive, the amplitude signal generation unit 10 and the maximum value selection unit 20 are represented by the equivalent circuit shown in Figure 9.

[0063] In this case, operational amplifiers OP1 to OP4 perform inverting amplification. Therefore, the potential V3 at node N3, between the output terminal of operational amplifier OP2 and the anode of diode D3, is equal to V1. Also, the potential V4 at node N4, between the output terminal of operational amplifier OP4 and the anode of diode D4, is equal to V2.

[0064] Figure 10 is a diagram illustrating the operation of the adjustment section circuit in a radar device according to an embodiment of the present invention. Figure 10 shows the operation of the circuits in the amplitude signal generation section 10 and the maximum value selection section 20 when the potentials of node N1 at the first end of resistor R1 and node N2 at the first end of resistor R6 are negative.

[0065] Referring again to Figure 8, when the potentials V1 at node N1 and V2 at node N2 are negative, diodes D2 and D5 conduct, and diodes D1 and D4 do not conduct. Therefore, when V1 and V2 are negative, the amplitude signal generation unit 10 and the maximum value selection unit 20 are represented by the equivalent circuit shown in Figure 10.

[0066] In this case, the potential V5 at node N5 on the non-inverting input terminal side of op-amp OP2 is (-2 / 3) × V1, according to the virtual short condition of op-amp OP1 and Kirchhoff's laws. Also, the potential V6 at node N6 on the non-inverting input terminal side of op-amp OP4 is (-2 / 3) × V2, according to the virtual short condition of op-amp OP3 and Kirchhoff's laws. Furthermore, op-amps OP2 and OP4 perform non-inverting amplification. Therefore, the potential V3 at node N3 is equal to -V1. Also, the potential V4 at node N4 is equal to -V2.

[0067] As explained with reference to Figures 9 and 10, V3 and V4 are equal to V1 and V2, respectively, when V1 and V2 are positive, and equal to -V1 and -V2, respectively, when V1 and V2 are negative. In other words, V3 and V4 are equal to the absolute values ​​of V1 and V2, respectively.

[0068] When V3 is greater than V4, diode D3 conducts and diode D6 does not conduct. On the other hand, when V4 is greater than V3, diode D6 conducts and diode D3 does not conduct. Therefore, the potential V10 at node N10, which is the cathode side of diode D3 and the cathode side of diode D6, is equal to the larger of the two potentials, V3 and V4.

[0069] Based on the above, the amplitude signal generation unit 10 and the maximum value selection unit 20 receive the I signal Si and the Q signal Sq, and output the maximum value signal Smax, obtained by taking the maximum value of the amplitude signal Smi, which is the full-wave rectified waveform of the received I signal Si, and the amplitude signal Smq, which is the full-wave rectified waveform of the received Q signal Sq, to ​​the subsequent LPF 30. When the amplitude signal generation unit 10 receives the I signal Si and the Q signal Sq to which the offset voltage Vo has been applied by the offset application circuit described above, the offset voltage Vo is applied to the non-inverting input terminal of the operational amplifier OP1 and the non-inverting input terminal of the operational amplifier OP3.

[0070] [Operation Flow] Figure 11 is a flowchart illustrating an example of the operation procedure when a radar device according to an embodiment of the present invention adjusts the gain of a received signal.

[0071] Referring to Figure 11, first, the radar device 300 transmits a transmission signal whose frequency is changed over time (step S102).

[0072] Next, the radar device 300 receives the radio waves that have been reflected back by an object from the transmitted signal as a received signal (step S104).

[0073] Next, the radar device 300 generates a baseband I signal Si and a Q signal Sq based on the received signal (step S106).

[0074] Next, the radar device 300 generates an amplitude signal Smi, which represents the amplitude of the baseband I signal Si, and an amplitude signal Smq, which represents the amplitude of the baseband Q signal Sq (step S108).

[0075] Next, the radar device 300 selects the one with the larger level between the amplitude signal Smi and the amplitude signal Smq as the maximum value signal Smax (step S110).

[0076] Next, the radar device 300 generates a maximum value signal Fmax by filtering the maximum value signal Smax (step S112).

[0077] Next, the radar device 300 adjusts the gain of the received signal based on the maximum value signal Fmax. More specifically, the gain adjustment unit 40 in the radar device 300 outputs a control voltage corresponding to the level of the maximum value signal Fmax to the variable gain amplifier in the receiving unit 150 (step S114).

[0078] However, the technology described in Patent Document 1 makes it difficult to finely adjust the gain of the received signal. Furthermore, the technology described as prior art in Patent Document 1, which uses an AGC circuit to control the gain of the received signal, may not be able to properly adjust the gain of the received signal. There is a need for a technology that can adjust the gain of the received signal more appropriately than such conventional technologies.

[0079] In contrast, in the radar device 300 according to an embodiment of the present invention, the transmitting unit 120 transmits a transmission signal whose frequency is changed over time. The receiving unit 150 receives the radio waves that have been reflected back by an object as a received signal. The frequency conversion unit 170 generates an I signal Si and a Q signal Sq based on the received signal. The amplitude signal generation unit 10 generates an amplitude signal Smi, which indicates the amplitude of the I signal Si, and an amplitude signal Smq, which indicates the amplitude of the Q signal Sq. The maximum value selection unit 20 selects the one with the larger level between the amplitude signal Smi and the amplitude signal Smq as the maximum value signal Smax. The gain adjustment unit 40 adjusts the gain of the received signal based on the maximum value signal Smax.

[0080] In this configuration, an I signal Si and a Q signal Sq are generated based on the received signal, and the gain of the received signal is adjusted based on the maximum value signal Smax, which is selected as the larger of the amplitude signal Smi (which indicates the amplitude of the I signal Si) and the amplitude signal Smq (which indicates the amplitude of the Q signal Sq). Therefore, when the amplitudes of the I signal Si and the Q signal Sq differ due to the gain of each signal path, the gain of the received signal can be adjusted based on the amplitude of the larger of the I signal Si and the Q signal Sq, thus suppressing the excessive increase in the strength of the received signal after gain adjustment. Consequently, the gain of the received signal can be adjusted more appropriately. Furthermore, the gain of the received signal can be adjusted according to the magnitude of the amplitudes of the I signal Si and Q signal Sq, which have reduced interference from the transmitted signal to the received signal. Moreover, the process of generating the amplitude signal Smi and the amplitude signal Smq and selecting the maximum value signal Smax can be realized with a simple circuit configuration consisting of general-purpose components such as operational amplifiers, resistors, capacitors, and diodes.

[0081] The embodiments described above should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than the above description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of symbols]

[0082] 10 Amplitude signal generation section 20 Maximum value selection section 30 LPF 40 Gain adjustment section 100 Adjustment section 110 Signal generation unit 120 Transmitter 130 Transmitting Antenna 140 Receiving Antenna 150 Receiver 170 Frequency conversion section 180 A / D conversion unit 190 Signal Processing Unit 201 Radar Section 202 Display Processing Unit 300 Radar Equipment T1, T2 Input Terminals T3 Output Terminal R1~R11 Resistors OP1~OP4 Operational Amplifiers D1~D6 Diodes C1 Capacitor

Claims

1. A transmitting unit that transmits a transmission signal whose frequency changes over time, A receiving unit that receives the radio waves that have been reflected back by an object from the transmitted signal as a received signal, A frequency conversion unit that generates in-phase signals and quadrature signals based on the received signal, An amplitude signal generation unit that generates an in-phase amplitude signal indicating the amplitude of the in-phase signal and an orthogonal amplitude signal indicating the amplitude of the orthogonal signal, A maximum value selection unit selects the one with the higher level from the in-phase amplitude signal and the quadrature amplitude signal, which are analog signals, as the maximum value signal. A low-pass filter that receives the maximum value signal and attenuates components of the maximum value signal that are above a predetermined frequency, A gain adjustment unit adjusts the gain of the received signal based on the maximum value signal that has passed through the low-pass filter, A / D conversion unit that digitally converts the in-phase signal and the quadrature signal, A radar device comprising: a data conversion unit that converts the common-mode signal and the quadrature signal, which have been digitally converted by the A / D conversion unit, from complex voltages to real signal voltages; generates a power spectrum using the converted signals; and generates amplitude data showing the relationship between distance and amplitude by converting the frequency in the power spectrum into distance.

2. The radar device according to claim 1, wherein the amplitude signal generation unit, the maximum value selection unit, the low-pass filter, and the gain adjustment unit are all configured by analog circuits.

3. The frequency conversion unit generates the in-phase signal and the quadrature signal in the baseband band, The radar apparatus according to claim 1 or 2, wherein the amplitude signal generation unit generates an in-phase amplitude signal indicating the amplitude of the in-phase signal in the baseband band and an orthogonal amplitude signal indicating the amplitude of the orthogonal signal in the baseband band.

4. A gain adjustment method for a radar device, A transmission signal with a frequency that changes over time is sent. The aforementioned transmitted signal is reflected by an object and the resulting radio waves are received as the received signal. Based on the received signal, an in-phase signal and an orthogonal signal are generated. An in-phase amplitude signal showing the amplitude of the in-phase signal and an orthogonal amplitude signal showing the amplitude of the orthogonal signal are generated. Of the analog signals, the one with the higher level between the in-phase amplitude signal and the quadrature amplitude signal is selected as the maximum value signal. Upon receiving the maximum value signal, the components of the maximum value signal that are above a predetermined frequency are attenuated. Based on the attenuated maximum signal, the gain of the received signal is adjusted. The in-phase signal and the quadrature signal are digitally converted, A gain adjustment method comprising: converting the digitally converted common-mode signal and quadrature signal from complex voltage to real signal voltage; generating a power spectrum using the converted signals; and generating amplitude data showing the relationship between distance and amplitude by converting the frequency in the power spectrum into distance.

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