Radar power monitoring device, pulse compression radar device and radar power measurement method

Abstract

Radar performance monitoring device (30) comprising: a receiver (38) for receiving a transmission signal of which a temporal change in frequency is non-linear, wherein the transmission signal was transmitted by a radar unit (10) of a pulse compression radar device (1), a response signal generator (31) - to generate a response signal whose frequency changes linearly over time and - to send the response signal to the radar unit (10) in response to the transmission signal received by the receiver (38).

Description

Technical field

[0001] The present invention relates in principle to a radar power monitoring device, in particular a radar power monitoring device which is connected to a radar device for transmitting a signal whose frequency changes over time are not linear. Background of the invention

[0002] Oscillators and demodulators, such as those used in radar systems, can degrade with use and be damaged by intense external signals. Therefore, some applications incorporate radar monitoring to check whether the radar system's transmit power and receive sensitivity are sufficient.

[0003] A radar performance monitoring device receives a transmission signal from a radar unit of the radar system and transmits a response signal to the radar unit. The response signal is analyzed, and the resulting data is used, for example, to verify the performance of the radar system. JP 2011-043351 A discloses such a radar performance monitoring device.

[0004] The radar performance monitoring device disclosed in JP 2011-043351 A transmits a response signal that continuously changes frequency within a predetermined frequency range within a receiver band of the radar unit (so-called chirp signal). This design prevents, for example, a transmission band of the response signal from lying outside the receiver band of the radar unit, even if the frequency of the response signal is changed.

[0005] In recent years, radar performance monitoring devices have become known that feature configurations for transmitting a signal with a relatively long pulse length and a continuously changing frequency. Upon receiving the signal, pulse compression is performed. The transmission signal for the pulse compression radar device can be not only a linearly changing frequency signal (linear signal) but also a non-linearly changing frequency signal.

[0006] In conventional radar power monitoring devices provided in pulse compression radar systems from which non-linear signals are transmitted, it is known that it is necessary to transmit a response signal similar to a transmission signal, since in the case of transmission of a non-linear transmission signal, a signal from which a peak value has fallen (or a signal without a peak) can be detected if the frequency of the transmitted signal differs from that of the response signal, even if the radar unit performs pulse compression.

[0007] Consequently, there is a need for a radar power monitoring device that includes a configuration for generating the non-linear transmission signal (for example, a D / A converter or a mixer). Furthermore, radar power monitoring devices require receiving a reference signal from the radar unit to match the frequency of the transmission signal to that of the response signal. As described above, radar monitoring devices used in pulse compression radar systems that transmit non-linear signals have extremely complex configurations. Further prior art in this technical field is disclosed in documents US 7,688,257 B1, US 2005 / 0 190 100 A1, and DE 10 2007 041 669 A1. Summary of the invention

[0008] The present invention was made in view of the circumstances described above and is fundamentally aimed at providing a radar performance monitoring device which is suitable for checking the performance of a radar unit for transmitting a non-linear signal, but without requiring a configuration for generating the non-linear transmission signal or a reference signal from the radar unit.

[0009] According to one aspect of the present invention, a radar power monitoring device with the following configuration is proposed. The radar power monitoring device comprises a receiver for receiving a transmission signal, the temporal change of which is non-linear, wherein the transmission signal was transmitted from a radar unit of a pulse compression radar system, and a response signal generator for generating a response signal, the temporal change of which is linear, and for sending the response signal to the radar unit as a response to the transmission signal received by the receiver.

[0010] Even if the linear response signal is sent while the transmission signal is non-linear, a peak region of the response signal can be detected. Consequently, the configuration of the radar performance monitoring device can be simplified by appropriately implementing the function of verifying the radar unit's performance.

[0011] The response signal generator can generate the response signal in such a way that a gradient of the linear response signal coincides with a part of the non-linear transmission signal.

[0012] Consequently, even if the frequency of the transmission signal or the response signal changes over time, the function of the radar power monitoring device can be performed without changing the signal transmitted by the response signal generator.

[0013] The waveform of the transmission signal can be symmetrical with respect to a point corresponding to the center frequency of the transmission signal. The portion of the non-linear transmission signal can correspond to the center frequency of the transmission signal.

[0014] Consequently, the pulse compression radar device can achieve the result that the response signal does not necessarily have to follow the change in frequency of the transmission signal or the response signal by using a transmission signal which has a commonly used waveform.

[0015] The response signal generator can change the rate of change of the response signal's frequency over time.

[0016] Consequently, even if the transmission signal transmitted by the radar unit is changed or the radar power monitoring device is connected to different radar equipment, the radar power monitoring device can still be used in such cases.

[0017] The response signal generator may include a phase synchronization circuit that includes a sweep frequency function for changing the frequency of the response signal.

[0018] Consequently, the signal, which exhibits a linear change over time, can be easily generated by a simple control.

[0019] According to a further aspect of the present invention, a pulse compression radar device is provided. The device comprises the radar power monitoring device according to one of the aspects described above and a radar unit for transmitting the transmission signal, receiving the response signal, and performing pulse compression of the response signal based on the transmission signal.

[0020] Consequently, the pulse compression radar system can be comprehensively implemented as a radar power monitoring device in a simple configuration.

[0021] According to a further aspect of the present invention, a method for measuring radar power is provided. The method comprises sending a transmission signal from a pulse compression radar unit, the temporal change of which is linear, receiving the transmission signal from a radar power monitoring device of the pulse compression radar unit, transmitting a response signal from the radar power monitoring device to the radar unit, the temporal change of which is linear, in response to the transmission signal, and performing pulse compression of the response signal based on the transmission signal.

[0022] Consequently, even if the linear response signal is transmitted while the transmission signal is non-linear, a peak portion of the response signal can be detected. Therefore, the configuration of the radar performance monitoring device can be simplified by appropriately implementing the function of verifying the radar unit's performance. Brief description of the drawings

[0023] The present disclosure of the invention is illustrated by means of examples, which are not limited to the figures and the accompanying drawings. In the drawings, identical reference numerals refer to identical elements. The drawings show: Fig. Figure 1 shows a block diagram of an embodiment of a pulse compression radar device according to an exemplary embodiment of the invention; Fig. Figure 2 is a diagram illustrating pulse compression; Fig. Figure 3 is a graph showing a change in the frequencies of a transmission signal and a response signal over time; Fig. Figure 4 is an example of displaying a radar image of the response signal; Fig. Figure 5 is a diagram showing a processed signal obtained by pulse compression of linear and non-linear response signals; Fig. Figure 6 is a diagram showing a state when the frequencies of the transmission signal or the response signal have been changed; Fig. Figure 7 shows a block diagram of a modified embodiment of the pulse compression radar device; and Fig. Figure 8 shows a block diagram of a conventional pulse compression radar device. Detailed description

[0024] In the following, exemplary embodiments of the present invention are described in detail with reference to the accompanying drawings. Fig. Figure 1 shows a block diagram of an embodiment of a pulse compression radar device 1 according to an embodiment of the present invention.

[0025] The pulse compression radar 1 according to this embodiment is a radar device installed on a ship (hereinafter referred to as "concerning a ship" or simply "the ship"), wherein the radar device can detect the position and speed of a target object by transmitting radio waves (transmission signal) with a slow pulse duration and pulse compression, and by analyzing a received signal representing the transmission signal reflected from the target object. Furthermore, the pulse compression radar 1 comprises a radar unit 10 for transmitting radio waves to a PM unit 30 (radar performance monitoring device) for checking the performance of the radar unit 10, and a control circuit 40.

[0026] The radar unit 10 comprises a transmission signal generation circuit 11 as a design for transmitting the transmission signal, a D / A converter 12, a mixer 13, a local oscillator 14, a transmit amplifier 15, a circulator 16 and a radar antenna 17.

[0027] The transmission signal generation circuit 11 generates a transmission signal that has a predetermined waveform (a temporal change in frequency). In this embodiment, the transmission signal generation circuit 11 generates a non-linear transmission signal (non-linear chirp signal) and outputs it to the D / A converter 12. The D / A converter 12 converts the transmission signal generated by the transmission signal generation circuit 11 from a digital signal to an analog signal and outputs it to the mixer 13.

[0028] The local oscillator 14 comprises an oscillator 25, a PLL (phase synchronization circuit) IC 26 and a VCO (voltage-controlled oscillator) 27.

[0029] The oscillator 25 can generate a signal with a predetermined frequency. The PLL IC 26 controls the VCO 27 to output a local oscillator signal (station transmission signal).

[0030] Mixer 13 mixes the transmission signal input from D / A converter 12 with the station transmission signal output from local oscillator 14. This increases the transmission signal frequency to a suitable transmission frequency. Mixer 13 outputs the transmission signal at the increased frequency to transmission amplifier 15. Transmission amplifier 15 amplifies the transmission signal and transmits it externally via radar antenna 17 and circulator 16. The transmission signal is the non-linear chirp signal as previously described (see R*(t) of Fig. 3)).

[0031] The radar antenna 17 transmits the transmission signal as described above and receives a reflection signal, which is obtained as a received signal from the reflection of the transmission signal off a target object (an echo source). Furthermore, the radar antenna 17 repeats the transmission of the radio waves while rotating in a horizontal plane at a predetermined rotational speed. In the previously described configuration, a 360° scan in the horizontal plane around a ship can be performed, and the status of the target objects surrounding the ship can be determined.

[0032] The circulator 16 can suitably switch a signal path so that the high-energy transmission signal from the transmission signal amplifier 15 is not input into the circuit on the receiving side, but the received signal is suitably input into the circuit on the receiving side.

[0033] The following describes a configuration for processing the received signal from the radar antenna. The radar unit 10 comprises, as a configuration for processing the received signal, a receiver amplifier 18, a mixer 19, an analog-to-digital converter 20, and a signal processing circuit 21.

[0034] The receiver amplifier 18 performs the processing to amplify the received signal, which is weak at a low level. By passing the signal through the receiver amplifier 18, the weak received signal level can be amplified to a level at which the following procedure can be carried out. The amplified received signal is then output to the mixer.

[0035] Mixer 19 can reduce the frequency of the received signal by mixing it with the station transmission signal of the local oscillator 14, similar to mixer 13. Mixer 19 outputs the received signal at the reduced frequency to the A / D converter 20. The A / D converter 20 converts the received signal at the reduced frequency from an analog signal to a digital signal.

[0036] The signal processing circuit 21 performs pulse compression of the received signal from the A / D converter 20, taking into account the input transmission signal, etc. The pulse compression is, as shown in Fig. Figure 2 shows the processing for obtaining a processed signal by compressing (demodulating) a signal pulse based on the received signal and a complex conjugation of the transmitted signal. The signal processing circuit 21 generates a radar image based on the processed signal.

[0037] In particular, the signal processing circuit 21 obtains a distance from the radar antenna 17 to the target object based on a time difference between the time at which the radar antenna 17 transmits the signal and the time at which the radar antenna 17 receives the reflected signal. Furthermore, the signal processing circuit 21 determines the detection of the target object based on the direction of the radar antenna 17 when the signal is detected. As previously described, the signal processing circuit 21 generates the radar image and displays it on a screen (not shown).

[0038] The following is a description of the PM unit 30 (radar power monitoring device). The PM unit 30 comprises a response signal generator 31, a response amplifier 35, a switch 36, a PM antenna 37, and a detector (receiver) 38.

[0039] The response signal generator 31 comprises, in a configuration for generating the response signal, an oscillator 32, a PLL-IC 33 and a VCO 34.

[0040] The oscillator 32 can generate a signal with a predetermined frequency. The PLL IC 33 controls the VCO 34 so that it outputs the response signal. In this embodiment, the response signal output by the VCO 34 is a linear signal in which the frequency changes after a certain time interval and the magnitude of the frequency change is fixed (a linear chirp signal) (see E(t) of Fig. 3).

[0041] It should be noted that in this embodiment, the PM unit has a configuration for transmitting the linear signal, while the radar unit has a configuration for transmitting the non-linear signal. Nevertheless, the performance of the radar unit 10 can be adequately detected (the reasons for this will be described later).

[0042] Furthermore, the PLL IC 33 features a sweep frequency function that can change the frequency of the output signal. Consequently, the PLL IC 33 can easily generate a signal that changes its frequency over time. The response signal generator 31 outputs the linear response signal, which it generated, to the response amplifier 35.

[0043] The response amplifier 35 amplifies the response signal and outputs it to the switch 36. The switch 36 can toggle between a state in which the response signal has been transmitted to the PM antenna 37 and a state in which the signal received by the PM antenna 37 has been output to the detector 38 (transmission signal transmitted by the radar unit 10).

[0044] Switch 36 is normally in the state where the signal received by PM antenna 37 has been output to detector 38. As soon as detector 38 detects the transmission signal from radar unit 10, which was received by PM unit 30, PM unit changes the state of switch 36 to a state where the response signal is transmitted to PM antenna 37, for transmission of the response signal to radar unit 10 (radar antenna 17).

[0045] The radar unit 10 receives the response signal and performs, for example, pulse compression to generate the radar image. A user can monitor the performance of the radar unit 10 by checking the radar image. Fig. Figure 4 shows an example of the radar image of the response signal. In this embodiment, the PM unit 30 transmits the response signal at a multitude of times while the signal intensity is reduced, so that the subsequently transmitted response signal has a lower intensity. According to this embodiment, the receiving sensitivity of the radar unit can be checked based on the number of displayed echoes of the response signal. It should be noted that the transmission performance of the radar unit 10 can be checked using the PM unit 30 by changing a transmission time of the response signal according to the intensity of the transmitted signal.

[0046] The following describes the difference between a configuration according to this example and a conventional configuration.

[0047] First, a simple description of a conventional radar power monitoring device 1 is given. A conventional PM unit 30 comprises, as in Fig. Figure 8 shows a response signal generation circuit 61, a D / A converter 62, and an additional mixer 63, compared to the configuration of the PM unit 30 according to this embodiment. Furthermore, the conventional pulse compression radar 1 is configured with a connection circuit to the local oscillator 14 of the radar unit 10 with the PLL IC 33.

[0048] The response signal generation circuit 61 can generate the non-linear response signal similarly to the transmission signal generation circuit 11. The D / A converter 62 converts the response signal from a digital signal into an analog signal. The mixer 63 increases the frequency of the response signal based, for example, on the local signal output by the local oscillator.

[0049] As described above, the conventional configuration requires a device to generate a complex response signal. Furthermore, the conventional PM unit 30 requires a circuit to receive the local signal from the radar unit 30 in order to match its frequency with the radar unit 10.

[0050] In the configuration described above, the conventional pulse compression radar 1 can transmit the response signal at the same frequency (same waveform) as the transmission signal. Consequently, a very accurate processing signal can be obtained by pulse compression of the response signal as described above.

[0051] The following is a detailed description of the waveform of the transmission signal and the response signal according to this embodiment. As in Fig. As shown in Figure 3, the transmitted signal (R*(t)) has a point-symmetric waveform where the point of symmetry indicates a center frequency, and the response signal (E(t)) exhibits a waveform tuned to intersect the point that indicates the center frequency of the transmitted signal and has a gradient that is the same as the gradient of the transmitted signal that indicates the center frequency. In other words, the response signal has a waveform close to the center frequency of the transmitted signal, approximating it.

[0052] Consequently, by performing pulse compression on the response signal, the processed signal, which has a peak, can be obtained (see the solid line in Fig. 5) In the conventional configuration, as in Fig. As shown in Figure 5, the echo can be detected with higher accuracy than in the configuration according to this embodiment. However, even in a configuration according to this embodiment, the radar power of the radar unit 10 can be checked with the radar power monitoring device, since it is only necessary to know the position of the peak (e.g., only the position of the peak that is higher than the background noise).

[0053] Furthermore, the configuration according to this embodiment does not require a response signal generation circuit 61, a D / A converter 62, a mixer 63 and a connection circuit for connecting the local oscillator 14 to the PLL IC 33, as is the case in conventional designs.

[0054] In conventional embodiments, the signal output by the local oscillator 14 (oscillator 25) is output to the PLL IC. The frequency of the transmitted signal can differ from that of the response signal, corresponding to a time period of the crystal oscillator used (chronological change characteristics). Although, as in Fig. As shown in Figure 6, if the difference between the transmission signal (R*(t)) and the response signal (E''(t)) is small, significant distortion of the processed signal and a degradation (disappearance) of the peak can occur. It should be noted that in the crystal oscillator, the frequency of the signal can vary not only over time but also, for example, due to changes in ambient temperature.

[0055] Consequently, if the echo response signal is weakened (disappears), its cause remains unclear, in particular whether it was caused by a change in the frequency of the transmitted signal or the response signal, or by the receiving system of the radar unit 10. Therefore, the performance of the radar unit 10 cannot be adequately determined.

[0056] On the other hand, it is true, as in Fig. As shown in Figure 6, in this embodiment, the direction in which the frequency of the transmitted signal (R*(t)) (gradient at the center frequency) changes coincides with the gradient of the response signal (E(t)). Consequently, the processed signal exhibits a similar shape to the response signal, even if the frequency of the transmitted signal changes, since the transmitted signal simply follows the response signal. In other words, according to this embodiment, the influence of the characteristics of the oscillator's time-varying behavior and the like can be eliminated without performing any special synchronization.

[0057] As previously described, the PM unit 30 in this embodiment comprises the detector 38 and the response signal generator 31. The detector 38 receives the non-linear chirp signal as the transmission signal transmitted by the radar unit 10 of the pulse compression radar. The response signal generator 31 generates the linear chirp signal as the response signal and transmits the response signal to the radar unit 10 in response to the transmission signal received by the detector 38.

[0058] In this way, even if the linear response signal is transmitted while the transmission signal is non-linear, the peak component of the response signal can be detected. Consequently, the configuration of the radar performance monitoring device can be simplified by appropriately applying the function to verify the performance of the radar unit.

[0059] Notwithstanding the fact that the suitable embodiment according to the present invention is described above, the configuration can also be modified by way of example as follows.

[0060] The configuration of the response signal generator 31 is not limited to the example described above and can, for example, be configured to generate the response signal using a DDS (Direct Digital Synthesizer) 51, as described in Fig. 7 is shown.

[0061] Furthermore, the PLL-IC 33 cannot have a sweep frequency function. Additionally, the various oscillators do not necessarily have to be crystal oscillators and can also be a type of atomic oscillator, for example rubidium or digitally controlled oscillators (for example, ring oscillators).

[0062] Furthermore, it is only necessary that the response signal generator 31 generates the response signals in such a way that the gradient of the linear response signal matches a part of the non-linear transmission signal, and the waveform generated by the transmission signal generation circuit 11 can also be different from the example described above.

[0063] The present invention is not limited to application in ship radar devices, but it can also be used in radar devices in a lighthouse and for monitoring the position of a moving body and the like, and furthermore the configuration can be such that it is installed in a moving body, such as an aircraft or a motor vehicle.

[0064] Specific embodiments of the present invention were described in the preceding description. However, those skilled in the art in this field will recognize that various modifications and changes can be made without departing from the scope of the present invention as defined in the claims. Consequently, the description and figures are to be considered primarily illustrative rather than restrictive, and all modifications intended to remain within the scope of the invention are included. The benefits, advantages, solutions to problems, and all elements providing a benefit, advantage, or solution that have been highlighted or emphasized are not to be considered essential features or elements of any or all claims.The invention is defined by the attached claims, including the amendments defined during the pendency of the present application and all claims equivalent to these claims.

Claims

[1] Radar power monitoring device (30) comprising: a receiver (38) for receiving a transmission signal of which a temporal change in frequency is non-linear, wherein the transmission signal was transmitted by a radar unit (10) of a pulse compression radar device (1), a response signal generator (31) - to generate a response signal whose frequency changes linearly over time and - to send the response signal to the radar unit (10) in response to the transmission signal received by the receiver (38). [2] Radar power monitoring device (30) according to claim 1, wherein the response signal generator (31) generates the response signal such that a gradient of the linear response signal matches a part of the non-linear transmission signal. [3] Radar power monitoring device (30) according to claim 2, wherein a waveform of the transmission signal is symmetrical with respect to a point corresponding to a center frequency of the transmission signal, and wherein the part of the non-linear transmission signal corresponds to the center frequency of the transmission signal. [4] Radar power monitoring device (30) according to one of claims 1 to 3, wherein the response signal generator (31) can change the rate of change of the frequency of the response signal over time. [5] Radar power monitoring device (30) according to any one of claims 1 to 4, wherein the response signal generator (31) comprises a phase synchronization circuit comprising a sweep frequency function for changing the frequency of the response signal. [6] Pulse compression radar device (1) comprising: the radar power monitoring device (30) according to one of claims 1 to 5 and a radar unit (10) - for transmitting the transmission signal, - to receive the response signal, - to perform pulse compression of the response signal based on the transmission signal. [7] Methods for measuring radar power, comprising: Transmission of a transmission signal from a pulse compression radar (1) with a non-linear change in frequency over time; reception of the transmission signal from a radar power monitoring device (30) of the pulse compression radar (1); Transmitting a response signal, of which a temporal change in frequency is linear, from the radar power monitoring device (30) to the radar unit (10) in response to the transmission signal, and performing pulse compression of the response signal based on the transmission signal. [8] Method for measuring radar power according to claim 7, wherein sending the response signal comprises transmitting the response signal to the radar unit (10) such that a gradient of the linear response signal matches a part of the non-linear transmission signal. [9] Method for measuring radar power according to claim 8, wherein a waveform of the transmission signal is symmetrical with respect to a point corresponding to a center frequency of the transmit signal, and wherein the part of the non-linear transmission signal corresponds to the center frequency of the transmission signal.

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