TWI902321B - radar device - Google Patents

Abstract

A radar device includes an antenna, an input transformer connected to the antenna, an adjustable local oscillator amplifier for receiving a radar signal, a local oscillator transformer connected to the adjustable local oscillator amplifier, a mixer connected to both the input transformer and the local oscillator transformer, and an adjustable transimpedance amplifier connected to the mixer for outputting an intermediate frequency signal. The differential signal output from the local oscillator transformer is leaked to the antenna via a mixer and/or through the coupling between the local oscillator transformer and the input transformer. This leaked portion serves as the radar signal transmitted by the radar device of this invention, thereby detecting targets at shorter distances. This eliminates the need for a transmitting antenna and its associated amplification circuitry, achieving the objective of this invention.

Description

Radar device

This invention relates to a radar device, particularly a radar device applicable to short-range detection.

As shown in Figure 5, a typical radar device 80 has a transmitting antenna 81 and a receiving antenna 84. A radar signal synthesizer 83 outputs a radar signal A to an output antenna and a radar signal B to a mixer. The radar signal A to the output antenna is amplified by an output power amplifier 82 and then radiated as a radar wave by the transmitting antenna 81. The radar wave is reflected by a target 100 and then received by the receiving antenna 84. 4. After receiving the signal, a received reflected signal C is obtained. This received reflected signal C is amplified by a low-noise receiver amplifier (LNA) 85, and then mixed with the radar signal B output to the mixer by a mixer 86 to obtain an intermediate frequency (IF) signal D. The IF signal D is converted into digitized raw data E by an analog-to-digital converter (ADC) 87. The raw data E is processed by a digital signal processor (DSP) 88 to obtain a feature map. Thus, the relative distance and orientation between the target object 100 and the radar can be determined based on this feature map.

As shown in Figure 6, Figure 6 illustrates the relationship between the frequency difference fb and the signal delay time td of a typical radar device 80, the intermediate frequency (IF) signal D output after mixing the radar signal A and the reflected signal C, and the waveform of the IF signal D after Fourier transformation.

Because the emitted radar waves have a certain intensity, the radar device 80 can detect targets at relatively long distances. However, when detecting targets at shorter distances, the radar device 80 does not need to emit radar waves of such intensity. Therefore, how to modify a general radar device 80 to be suitable for detecting targets at shorter distances is a problem worth exploring and also has a certain market demand.

In view of the aforementioned problems of the prior art, the present invention provides a radar device, comprising: an antenna having a signal terminal; an input transformer having a primary side and a secondary side, one end of the primary side of the input transformer being connected to the signal terminal of the antenna, and the other end of the primary side of the input transformer being a ground terminal; an adjustable local oscillator amplifier having a pair of input terminals and a pair of output terminals, the pair of input terminals of the adjustable local oscillator amplifier receiving a radar signal; a local oscillator transformer having a primary side and a secondary side, the two ends of the primary side of the local oscillator transformer being connected to a pair of output terminals of the adjustable local oscillator amplifier; and a first input terminal, a second input terminal, and a first... A mixer having an output terminal, a second output terminal, a first control terminal, and a second control terminal; the first and second input terminals of the mixer are respectively connected to the two ends of the secondary side of an input transformer, and the first and second control terminals of the mixer are respectively connected to the two ends of the secondary side of a local oscillation transformer; an adjustable impedance amplifier having a first input terminal, a second input terminal, a first output terminal, and a second output terminal; the first and second input terminals of the adjustable impedance amplifier are respectively connected to the first and second output terminals of the mixer, and the first and second output terminals of the adjustable impedance amplifier jointly output an intermediate frequency signal.

The radar device of this invention discloses the following technical content: A portion of the differential signal output from the local oscillator transformer, after being leaked to the antenna via a mixer and/or through coupling between the local oscillator transformer and the input transformer, is used as a radar signal emitted by the radar device of this invention to detect targets at shorter distances. The strength of the radar signal emitted by the radar device of this invention can be controlled by adjusting the output amplitude of the adjustable local oscillator amplifier and/or by adjusting the input DC bias voltage Vos of the adjustable transimpedance amplifier. This ensures that the radar signal remains in a controllable and stable state, thus enabling stable detection of targets at shorter distances. Compared to conventional radar devices, the radar device of this invention eliminates the need for a transmitting antenna and its related amplification circuitry, resulting in a smaller size, lower power consumption, lower cost, and suitability for detecting targets at shorter distances, thus achieving the purpose of this invention.

1: Radar Device

10: First Line

11: Input Transformer

12: Mixer

121: First Input Terminal

122: Second Input Terminal

123: First Output Terminal

124: Second Output Terminal

125: First control terminal

126: Second Control Terminal

13: Impedance Amplifier

131: First Input Terminal

132: Second Input Terminal

133: First Output Terminal

134: Second Output Terminal

14: Adjustable Impedance Amplifier

15: Low Noise Amplifier (LNA)

20: Local Oscillator Amplifier

21: Adjustable local oscillator amplifier

22: Local Oscillation Transformer

70: Target

71: Output Antenna

72: Output Power Amplifier

73: Radar Signal Synthesizer

77: Analog-to-Digital Converter

78: Digital Signal Processor

80: Radar Device

81: Output Antenna

82: Output Power Amplifier

83: Radar Signal Synthesizer

84: Receive Antenna

85: Low-noise receiver amplifier

86: Mixer

87: Analog-to-Digital Converter

88: Digital Signal Processor

100: Target

A: Radar signal output to the output antenna

B: Radar signal output to the mixer.

C: Received reflected signal

D: Intermediate Frequency Signal

E: Original Data

M1: First transistor

M2: Second transistor

M3: Third transistor

M4: Fourth transistor

Vos: Input DC bias voltage

Figure 1A is a circuit diagram of a first embodiment of the radar device of the present invention.

Figure 1B is a measurement diagram of the coupling strength between two transformers in a first embodiment of the radar device of the present invention.

Figure 2A is a circuit diagram of a second embodiment of the radar device of the present invention.

Figure 2B is a measurement diagram of the coupling strength between two transformers in a second embodiment of the radar device of the present invention.

Figure 3A is a circuit diagram of a radar device according to a third embodiment of the present invention.

Figure 3B is a schematic diagram of the radar device according to the third embodiment of the present invention.

Figure 4A is a schematic diagram of a radar device according to a fourth embodiment of the present invention.

Figure 4B is a schematic diagram of a radar device according to a fifth embodiment of the present invention.

Figure 5 is a circuit diagram of a typical radar device.

Figure 6 is a schematic diagram of the signal of a typical radar device.

The following, with reference to the accompanying drawings and preferred embodiments, further illustrates the technical means employed by the present invention to achieve its intended purpose.

Please refer to Figure 1A, which is a circuit diagram of a first embodiment of the radar device 1 of the present invention. The radar device 1 of the present invention includes an antenna 10 having a signal terminal and an input transformer 11 having a primary side and a secondary side. One end of the primary side of the input transformer 11 is connected to the signal terminal of the antenna 10, and the other end of the primary side of the input transformer 11 is a ground terminal connected to a ground voltage terminal. The radar device 1 of the present invention also includes an adjustable local oscillator amplifier 21 having a pair of input terminals and a pair of output terminals, and a local oscillator transformer having a primary side and a secondary side. Oscillator 22, the two ends of the primary side of the local oscillator 22 are connected to a pair of outputs of the adjustable local oscillator amplifier 21, and a pair of inputs of the adjustable local oscillator amplifier 21 are connected to a radar signal synthesizer (not shown) to receive a radar signal, which may be, for example, a frequency modulated continuous wave (FMCW) radar signal.

The radar device 1 of the present invention further includes a mixer 12 having a first input terminal 121, a second input terminal 122, a first output terminal 123, a second output terminal 124, a first control terminal 125, and a second control terminal 126. The first input terminal 121 and the second input terminal 122 of the mixer 12 are respectively connected to the two ends of the secondary side of the input transformer 11, and the first control terminal 125 and the second control terminal 126 of the mixer 12 are respectively connected to the two ends of the secondary side of the local oscillation transformer 22. The radar device 1 of the present invention further includes a trans-impedance amplifier having a first input terminal 131, a second input terminal 132, a first output terminal 133, and a second output terminal 134. Amplifier 13, the first input terminal 131 and the second input terminal 132 of the impedance amplifier 13 are respectively connected to the first output terminal 123 and the second output terminal 124 of the mixer 12. The first output terminal 133 and the second output terminal 134 of the impedance amplifier 13 are connected to an analog-to-digital converter (ADC, not shown), and the ADC is then connected to a digital signal processor (DSP, not shown). The first output terminal 133 and the second output terminal 134 of the impedance amplifier 13 output an intermediate frequency signal to the ADC (not shown). The ADC (not shown) outputs digitized raw data to the DSP (not shown), and the DSP (not shown) outputs a feature map. This map allows us to determine the relative distance and orientation between a short-range target and the first celestial antenna (10).

The mixer 12 is composed of a first transistor M1, a second transistor M2, a third transistor M3, and a fourth transistor M4 connected in parallel. The gates of the first transistor M1 and the fourth transistor M4 are connected, and the gates of the second transistor M2 and the third transistor M3 are connected. The drain of the first transistor M1 and the drain of the second transistor M2 are connected to form the first input terminal 121 of the mixer 12. The source of the first transistor M1 and the source of the second transistor M2 are connected to form the mixer 12. The first output terminal 123 of mixer 12 is connected to the drain of the third transistor M3 and the drain of the fourth transistor M4, forming the second input terminal 122 of mixer 12. The source of the third transistor M3 and the source of the fourth transistor M4 are connected to form the second output terminal 124 of mixer 12. The gate of the first transistor M1 and the gate of the fourth transistor M4 are connected to form the first control terminal 125 of mixer 12. The gate of the second transistor M2 and the gate of the third transistor M3 are connected to form the second control terminal 126 of mixer 12.

The adjustable local oscillator amplifier 21 may have an output amplitude control terminal (not shown) that receives an output amplitude adjustment signal to control the magnitude of its output amplitude, or the output amplitude may be controlled by directly changing the circuitry of the adjustable local oscillator amplifier 21.

In a first embodiment of the radar device 1 of the present invention, when the local oscillator transformer 22 transmits a control signal (i.e., a differential signal) to the first control terminal 125 and the second control terminal 126 of the mixer 12, the differential signal may leak to the antenna 10 through the mixer 12 and the input transformer 11. This is mainly because there may be a size mismatch between the first transistor M1/second transistor M2 and the third transistor M3/fourth transistor M4 of the mixer 12, or because there is coupling between the input transformer 11 and the local oscillator transformer 22.

Please refer to Figure 1B. Figure 1B is a measurement diagram of the coupling strength between two transformers in the first embodiment of the radar device 1 of the present invention. In Figure 1B of this embodiment, a first measurement value "-58.0 dBm" is the measured signal strength of the input transformer 11 when there is no coupling between the input transformer 11 and the local oscillating transformer 22 (i.e., the local oscillating transformer 22 is not present). In Figure 1B of this embodiment, a second measured value "-47.0 dBm" represents the measured signal strength of the input transformer 11 when there is coupling between the input transformer 11 and the local oscillating transformer 22 (i.e., the local oscillating transformer 22 is present). It can be seen that the differential signal of the local oscillating transformer 22 directly contributes 11 dBm to the measured signal strength of the input transformer 11.

Based on Figure 1B, it can be seen that when the output amplitude of the adjustable local oscillator amplifier 21 is increased, the contribution of the differential signal of the local oscillator transformer 22 directly to the strength of the measurement signal of the input transformer 11 (i.e., the strength of the differential signal of the local oscillator transformer 22 leaking to the input transformer 11) will also increase. Therefore, when detecting targets at shorter distances, in the first embodiment of the radar device 1 of the present invention, the portion of the differential signal leaked from the local oscillator transformer 22 to the antenna 10 can be used as a radar signal emitted by the radar device 1 of the present invention, thereby detecting targets at shorter distances. The intensity of the radar signal emitted by the radar device 1 of the present invention can be controlled by controlling the output amplitude of the adjustable local oscillator amplifier 21, thus keeping the radar signal in a controllable and stable state, and thus stably detecting targets at shorter distances. Compared to conventional radar devices, the first embodiment of the radar device 1 of the present invention can omit the transmitting antenna and its related amplification circuit, thereby reducing the size, power consumption, and cost of the radar device 1, and making it suitable for detecting targets at shorter distances, thus achieving the purpose of the present invention.

Please refer to Figure 2A, which is a circuit diagram of a second embodiment of the radar device 1 of the present invention. In this second embodiment, an adjustable impedance amplifier 14 replaces the impedance amplifier 13 in the first embodiment of the radar device 1, and a local oscillator amplifier 20 without amplitude adjustment function replaces the adjustable local oscillator amplifier 21 in the first embodiment of the radar device 1.

The adjustable impedance amplifier 14 may have a DC bias input control terminal (not shown) to receive a DC bias input control signal, thereby controlling the magnitude of an input DC bias voltage Vos. Alternatively, the magnitude of the input DC bias voltage Vos of the adjustable impedance amplifier 14 may be controlled by directly changing the circuitry of the adjustable impedance amplifier 14.

Please refer to Figure 2B. Figure 2B is a measurement diagram of the coupling strength between the two transformers in the second embodiment of the radar device 1 of the present invention. In Figure 2B, when the input DC bias voltage Vos of the adjustable impedance amplifier 14 of the present embodiment is 0V, the measured signal strength of the input transformer 11 is -58dBm. When the input DC bias voltage Vos of the adjustable impedance amplifier 14 is 5mV, the measured signal strength of the input transformer 11 is... Given a value of -52.5 dBm, it can be seen that for every 5 mV increase in the input DC bias Vos of the adjustable impedance amplifier 14, the measured signal strength of the input transformer 11 increases by 5.5 dBm. Therefore, increasing the input DC bias Vos of the adjustable impedance amplifier 14 increases the coupling strength between the two transformers in this embodiment (i.e., the strength of the differential signal leakage from the local oscillation transformer 22 to the input transformer 11).

Based on Figure 2B, in the second embodiment of the radar device 1 of the present invention, the portion of the differential signal leaked from the local oscillation transformer 22 to the first antenna 10 can be used as a radar signal emitted by the radar device 1 of the present invention, thereby detecting targets at shorter distances. The intensity of the radar signal emitted by the radar device 1 of the present invention can be controlled by the input DC bias voltage Vos, thus maintaining the radar signal in a controllable and stable state, thereby enabling stable detection of targets at shorter distances. Compared to conventional radar devices, the second embodiment of the radar device 1 of the present invention can omit the transmitting antenna and its related amplification circuit, thereby reducing the size, power consumption, and cost of the radar device 1, and making it suitable for detecting targets at shorter distances, thus achieving the purpose of the present invention.

Please refer to Figure 3A, which is a circuit diagram of a third embodiment of the radar device 1 of the present invention. In this third embodiment, the radar device 1 of the present invention simultaneously incorporates the adjustable local oscillator amplifier 21 of the first embodiment and the adjustable transimpedance amplifier 14 of the second embodiment, with the remaining circuitry being the same as that in the first and second embodiments. Thus, in the third embodiment of the radar device 1 of the present invention, the adjustable local oscillator transformer 21 can... The portion of the differential signal leaked to the first antenna 10 is used as a radar signal emitted by the radar device 1 of the present invention to detect targets at shorter distances. In a third embodiment of the radar device 1 of the present invention, the output amplitude of the adjustable local oscillator amplifier 21 and/or the magnitude of the input DC bias voltage Vos of the adjustable transimpedance amplifier 14 can be controlled to better maintain the radar signal in a controllable and stable state, thus enabling stable detection of targets at shorter distances. Compared to conventional radar devices, the third embodiment of the radar device 1 of the present invention can omit the transmitting antenna and its related amplification circuit, thereby reducing the size, power consumption, and cost of the radar device 1, and making it suitable for detecting targets at shorter distances, thus achieving the purpose of the present invention.

Please refer to Figure 3B, which is a schematic diagram of the radar device 1 of the present invention in a third embodiment. In addition to the components shown in Figure 3A, Figure 3B also includes an output antenna 71, an output power amplifier 72, a radar signal synthesizer 73, an analog-to-digital converter 77, and a digital signal processor 78. The presence or absence, or operation, of the output antenna 71 and the output power amplifier 72 does not affect the aforementioned functions of the present invention. Yes, that is, regardless of whether the output antenna 71 and the output power amplifier 72 are present and working, present and not working, or absent, the function of the first antenna 10 and related circuits of the present invention to transmit a radar signal S1 and receive a reflected wave signal S2 of the radar signal S1 to detect a target 70 at a short distance will not be affected, nor will the function of the first antenna 10 and related circuits of the present invention to receive general input signals will be affected. The radar signal synthesizer 73 outputs a radar signal S to the output power amplifier 72 and the adjustable local oscillator amplifier 21. The output power amplifier 72 amplifies the radar signal S and outputs it to the output antenna 71 to transmit a radar signal (i.e., the output antenna 71 and the output power amplifier 72 are present and working). The radar signal S is amplified by the adjustable local oscillator amplifier 21 and output to the local oscillator transformer 22, and then input through the mixer 12 and the input transformer 11. The radar 10 generates and transmits the radar signal S1. Simultaneously, the general input signal (not shown) received by the radar 10 is output to the analog-to-digital converter (ADC) 77 via the input transformer 11, the mixer 12, and the adjustable impedance amplifier 14. The ADC 77 then outputs the converted digital signal to the digital signal processor (DSP) 78. For further technical details, please refer to the relevant content in Figures 1A to 3A of the aforementioned specification. In one embodiment, the adjustable local oscillator amplifier 21 in Figure 3B can be replaced by the local oscillator amplifier 20; in another embodiment, the adjustable impedance amplifier 14 in Figure 3B can be replaced by the impedance amplifier 13.

Please refer to Figure 4A, which is a schematic diagram of a fourth embodiment of the radar device 1 of the present invention. In addition to the components in Figure 3B, Figure 4A also includes a low noise amplifier (LNA) 15. The LNA 15 is used to receive a signal transmitted from the antenna 10, amplify it, and output it to the input transformer 11. The cascode stage of the LNA 15 can be removed to reduce the isolation between the output and input terminals of the LNA 15. Alternatively, a capacitive coupling path can be deliberately added to reduce the isolation between the output and input terminals of the LNA 15. In one embodiment, the adjustable local oscillator amplifier 21 in FIG4A can be replaced by the local oscillator amplifier 20; in another embodiment, the adjustable transimpedance amplifier 14 in FIG4A can be replaced by the transimpedance amplifier 13.

Please refer to Figure 4B, which is a schematic diagram of a fifth embodiment of the radar device 1 of the present invention. The components in Figure 4B are the same as those in Figure 4A. The only difference between Figure 4B and Figure 4A is the position of the low-noise amplifier (LNA) 15; all other technical features are the same. That is, in Figure 4B, the LNA 15 is located between the input transformer 11 and the mixer 12. In one embodiment, the adjustable local oscillator amplifier 21 in Figure 4B can be replaced by the local oscillator amplifier 20; in another embodiment, the adjustable impedance amplifier 14 in Figure 4B can be replaced by the impedance amplifier 13.

The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make some modifications or alterations to the disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the present invention, shall still fall within the scope of the present invention.

1: Radar Device

10: First Line

11: Input Transformer

12: Mixer

121: First Input Terminal

122: Second Input Terminal

123: First Output Terminal

124: Second Output Terminal

125: First control terminal

126: Second Control Terminal

13: Impedance Amplifier

131: First Input Terminal

132: Second Input Terminal

133: First Output Terminal

134: Second Output Terminal

21: Adjustable local oscillator amplifier

22: Local Oscillation Transformer

M1: First transistor

M2: Second transistor

M3: Third transistor

M4: Fourth transistor

Claims (15)

A radar device includes: an antenna having a signal terminal; an input transformer having a primary side and a secondary side, one end of the primary side of the input transformer being connected to the signal terminal of the antenna, and the other end of the primary side of the input transformer being a ground terminal; an adjustable local oscillator amplifier having a pair of input terminals and a pair of output terminals, the pair of input terminals of the adjustable local oscillator amplifier receiving a radar signal; a local oscillator transformer having a primary side and a secondary side, the two ends of the primary side of the local oscillator transformer being connected to a pair of output terminals of the adjustable local oscillator amplifier; and a device having a first input terminal, a second input terminal, a first output terminal, and a second... A mixer having an output terminal, a first control terminal, and a second control terminal, wherein the first and second input terminals of the mixer are respectively connected to the two ends of the secondary side of an input transformer, and the first and second control terminals of the mixer are respectively connected to the two ends of the secondary side of a local oscillation transformer; a transimpedance amplifier having a first input terminal, a second input terminal, a first output terminal, and a second output terminal, wherein the first and second input terminals of the transimpedance amplifier are respectively connected to the first and second output terminals of the mixer, and the first and second output terminals of the transimpedance amplifier jointly output an intermediate frequency signal. The radar device as described in claim 1, wherein the pair of inputs of the adjustable local oscillator amplifier is connected to a radar signal synthesizer; and the first and second outputs of the impedance amplifier are connected to an analog-to-digital converter. A radar device includes: an antenna having a signal terminal; an input transformer having a primary side and a secondary side, one end of the primary side of the input transformer being connected to the signal terminal of the antenna, and the other end of the primary side of the input transformer being a ground terminal; a local oscillator amplifier having a pair of input terminals and a pair of output terminals, the pair of input terminals of the local oscillator amplifier receiving a radar signal; a local oscillator transformer having a primary side and a secondary side, the two ends of the primary side of the local oscillator transformer being connected to a pair of output terminals of the local oscillator amplifier; and a first input terminal, a second input terminal, a first output terminal, a second output terminal, and a... A mixer having a first control terminal and a second control terminal, wherein the first input terminal and the second input terminal of the mixer are respectively connected to the two ends of the secondary side of an input transformer, and the first control terminal and the second control terminal of the mixer are respectively connected to the two ends of the secondary side of a local oscillation transformer; an adjustable impedance amplifier having a first input terminal, a second input terminal, a first output terminal, and a second output terminal, wherein the first input terminal and the second input terminal of the adjustable impedance amplifier are respectively connected to the first output terminal and the second output terminal of the mixer, and the first output terminal and the second output terminal of the adjustable impedance amplifier jointly output an intermediate frequency signal. The radar device as described in claim 3, wherein the pair of inputs of the local oscillator amplifier is connected to a radar signal synthesizer; and the first and second outputs of the adjustable impedance amplifier are connected to an analog-to-digital converter. A radar device includes: an antenna having a signal terminal; an input transformer having a primary side and a secondary side, one end of the primary side of the input transformer being connected to the signal terminal of the antenna, and the other end of the primary side of the input transformer being a ground terminal; an adjustable local oscillator amplifier having a pair of input terminals and a pair of output terminals, the pair of input terminals of the adjustable local oscillator amplifier receiving a radar signal; a local oscillator transformer having a primary side and a secondary side, the two ends of the primary side of the local oscillator transformer being connected to a pair of output terminals of the adjustable local oscillator amplifier; and having a first input terminal, a second input terminal, a first output terminal, and a second output terminal. A mixer having a first input terminal, a first control terminal, and a second control terminal, wherein the first and second input terminals of the mixer are respectively connected to the two ends of the secondary side of an input transformer, and the first and second control terminals of the mixer are respectively connected to the two ends of the secondary side of a local oscillation transformer; and an adjustable impedance amplifier having a first input terminal, a second input terminal, a first output terminal, and a second output terminal, wherein the first and second input terminals of the adjustable impedance amplifier are respectively connected to the first and second output terminals of the mixer, and the first and second output terminals of the adjustable impedance amplifier jointly output an intermediate frequency signal. As described in claim 5, in the radar device, the pair of inputs of the adjustable local oscillator amplifier is connected to a radar signal synthesizer; the first and second outputs of the adjustable impedance amplifier are connected to an analog-to-digital converter. The radar device as described in claim 1, wherein the grounding terminal of the input transformer is connected to a ground voltage terminal. The radar device as described in claim 2, wherein the analog-to-digital converter is further connected to a digital signal processor. The radar device as described in claim 8, wherein the analog-to-digital converter receives the intermediate frequency (IF) signal and converts the IF signal into digitized raw data, and the digital signal processor receives the digitized raw data and converts the digitized raw data into a feature map. The radar device as described in any of claims 1 to 9 further comprises a low-noise amplifier between the first antenna and the input transformer, such that the first antenna and the input transformer are no longer directly connected. The low-noise amplifier has an output terminal and an input terminal; the input terminal of the low-noise amplifier is connected to the signal terminal of the first antenna, and the output terminal of the low-noise amplifier is connected to the primary side terminal of the input transformer. The radar device as described in claim 10, wherein the low-noise amplifier does not have a stacking stage. As described in claim 10, the radar device has a capacitively coupled path between the output and input of the low-noise amplifier. The radar device as described in any of claims 1 to 9 further comprises a low-noise amplifier located between the input transformer and the mixer, such that the input transformer and the mixer are no longer directly connected. The low-noise amplifier has a pair of output terminals and a pair of input terminals. The pair of input terminals of the low-noise amplifier are respectively connected to the two ends of the secondary side of the input transformer, and the pair of output terminals of the low-noise amplifier are respectively connected to the first input terminal and the second input terminal of the mixer. The radar device as described in claim 13, wherein the low-noise amplifier does not have a stacking stage. As described in claim 13, the radar device has a capacitively coupled path between the output and input of the low-noise amplifier.