Multiple-injection-locked ring traveling wave oscillator, doppler radar and sounding device

Abstract

The application relates to the field of integrated circuits, in particular to a multi-injection-locked ring wave oscillator, and a Doppler radar and a physiological characteristic detection device based on the ring wave oscillator. The ring wave oscillator comprises 16 inductive elements, 4 variable capacitors and 4 mirror injection circuits. The inductive elements are connected in sequence and are connected in a loop. Each two adjacent inductive elements form a phase-shifting channel and are distributed in four orthogonal directions in sequence. Two phase-shifting channels in each direction are parallel to each other and are located on the inner and outer sides of the same layer of the layout. The phase-shifting channels on the inner and outer sides in adjacent directions are connected alternately, and the wires between the phase-shifting channels are distributed on the upper and lower layers of the layout and have equal distances. The mirror injection circuit and the variable capacitor are connected between the two phase-shifting channels in each direction and output an injection signal with a phase difference of 180 DEG to the phase-shifting channels. The application solves the problems of the existing Doppler radar oscillator, such as limited injection locking range, high noise and insufficient phase uniformity.

Description

Technical Field

[0001] This invention relates to the field of integrated circuits, and in particular to a multi-injection locked ring traveling wave oscillator, as well as a Doppler radar and physiological feature detection device based on the ring traveling wave oscillator. Background Technology

[0002] Respiratory and heart rate are key indicators for assessing human vital signs and are of great value in disease diagnosis, health monitoring, and emergency rescue. Non-contact vital sign detection technologies (such as radar detection) are gaining increasing attention due to their user-unobtrusiveness and ease of deployment. For example, Doppler radar can efficiently and stably detect echo signals caused by chest wall movement, which can then be used to monitor human vital signs in non-contact scenarios such as burn monitoring and earthquake rescue.

[0003] However, such detection devices use, for example Figure 1 Traditional injection-locked Doppler radars, as shown, have complex structures, requiring mixers for signal demodulation, resulting in high hardware costs and significant mixer noise that affects detection sensitivity. Based on this, researchers have proposed an alternative self-injection-locked radar based on a phase-locked loop (PLL). This radar uses an injection-locked oscillator as the demodulation core, possessing bandpass filtering characteristics, which reduces system complexity while maintaining overall performance. However, the inductively coupled (LC) oscillators in this type of Doppler radar still suffer from low injection sensitivity. For example, Figure 2 A simple ring oscillator with low power consumption and support for multi-phase operation is provided, but its operating frequency is relatively low and its phase noise is relatively high. Figure 3 An LC oscillator with low phase noise and suitable for high-frequency operation is provided, but it has the problem of not being able to generate multiple phases and requires complex circuitry to generate multiple phases. Figure 4 A ring traveling wave oscillator (RTWO) is proposed, which combines the advantages of ring oscillators and LC oscillators, exhibiting low phase noise and multi-phase injection point capability at high frequencies. However, the single injection circuit traditionally used suffers from low injection efficiency, effective injection only within half a cycle of the oscillator, and difficulty in common-mode level control, resulting in a limited locking range and affecting detection sensitivity. Figure 5 A ring traveling wave oscillator with a large injection lock-in range is further provided. However, this circuit needs to operate at low oscillation amplitude, and the asymmetry of the Möbius ring causes the phase of the ring traveling wave oscillator to become non-uniform when operating at low voltage, affecting its normal operation at low voltage. Summary of the Invention

[0004] To address the problems of limited injection lock range, high noise, and insufficient phase uniformity in existing Doppler radar oscillators, this invention provides a multi-injection lock ring traveling wave oscillator, as well as a Doppler radar and physiological feature detection device based on the ring traveling wave oscillator.

[0005] The technical solution provided by this invention is as follows:

[0006] A multi-injection locked ring traveling-wave oscillator includes 16 inductive elements rf1~rf16; 4 variable capacitors Cv1~Cv4; and 4 mirror injection circuits. rf1~rf16 are connected sequentially and end-to-end. Every two adjacent inductive elements form a phase-shifting channel, and the eight phase-shifting channels are sequentially distributed in four orthogonal directions. The two phase-shifting channels in each direction are parallel to each other and located on the inner and outer sides of the same layer of the layout. The inner phase-shifting channel in the previous direction is connected to the outer phase-shifting channel in the next direction; the outer phase-shifting channel in the previous direction is connected to the inner phase-shifting channel in the next direction; thus forming a two-layer Möbius strip structure.

[0007] In every two adjacent directions, the inner phase-shifting channel and the outer phase-shifting channel are electrically connected by two sets of wires respectively; in this invention, these two sets of wires are arranged on the upper and lower layers at the same plane position in the layout, and the distance between the two sets of wires on the layout is equal.

[0008] In each direction of the layout, the first inductive element in the inner and outer phase-shifting channels serves as two injection ports with a phase gap of 180°, and is electrically connected to the two outputs of a mirror injection circuit. Each mirror injection circuit is used to output a set of injection signals A and B with a phase difference of 180° based on a set of differential input signals.

[0009] Furthermore, in both the inner and outer phase-shifting channels, the tail end of the first inductive element is connected to the two ends of a variable capacitor.

[0010] As a further improvement of the present invention, the conductor connecting the inner and outer phase-shifting channels in adjacent directions is composed of a first branch segment connected to the preceding phase-shifting channel, a collinear end located in the middle, and a second branch segment connected to the following phase-shifting channel. The first branch segments connecting the ends of two phase-shifting channels in any direction are arranged along the upper and lower layers respectively and extend inward at a 45° angle, thus overlapping the upper and lower layers of the same point P in the layout plane. The second branch segments connecting the beginning ends of two phase-shifting channels in the next direction are also arranged along the upper and lower layers respectively and extend inward at a 45° angle, thus overlapping the upper and lower layers of the same point Q in the layout plane. The collinear segment in the layout plane includes two mutually perpendicular and equidistant sub-segments; the two collinear segments connect nodes P and Q along the upper and lower layers respectively.

[0011] As a further improvement of this invention, each mirror injection circuit consists of four PMOS transistors P1~P4 and five NMOS transistors N1~N5. The sources of P1~P4 are connected to VDD; P1 is connected to the drain of N1. P2 is connected to the drain of N2; P1 is connected to the gate of N1 and serves as the non-inverting input port Vinj+; P2 is connected to the gate of N2 and serves as the inverting input port Vinj-. The drains of P1, N1, P3, and N3 are connected to the gates of P4 and N4, serving as the output port of one of the injection signals A; the drains of P2, N2, P4, and N4 are connected to the gates of P3 and N3, serving as the output port of one of the injection signals B. The sources of N3 and N4 are connected to the drain of N5; the gate of N5 is connected to the reference voltage signal Vbias; the sources of N1, N2, and N5 are connected to VSS.

[0012] As a further improvement of the present invention, the variable capacitor and the mirror injection circuit in each direction are arranged in the region between the two phase-shifting channels in that direction; both are located on the same layer as the inductive elements in the inner and outer phase-shifting channels.

[0013] As a further improvement of the present invention, the positions of the variable capacitors and the mirror injection circuits in different directions are arranged rotationally symmetrically on the layout, with a rotation angle of 90°.

[0014] As a further improvement of the present invention, the multi-injection locked ring traveling wave oscillator includes eight injection ports located on each phase shift channel, and the phase difference between the injection signals of the injection ports in adjacent phase shift channels is 45°.

[0015] As a further improvement of the present invention, the variable capacitor is an interdigitated capacitor.

[0016] As a further improvement of the present invention, the inductive element uses a high-layer metal wire.

[0017] The present invention also includes a Doppler radar that employs a multi-injection locked ring traveling wave oscillator as described above.

[0018] The present invention also includes a physiological characteristic detection device for detecting human vital signs through non-contact vital sign detection technology. The physiological characteristic detection device uses the aforementioned Doppler radar, which is used to detect the phase change of the echo signal caused by the movement of the human chest wall, thereby extracting respiratory and heartbeat information.

[0019] The present invention has the following beneficial effects:

[0020] The multi-injection-locked ring traveling-wave oscillator provided by this invention features complementary injection circuits at all eight phase nodes of the loop, with a 45° phase difference between the injected signals, sequentially injecting into the eight nodes of the ring traveling-wave oscillator. This increases the injection-locking range to eight times that of single injection and improves the signal-to-noise ratio by 9 dB. The mirror injection circuit in the circuit adopts a complementary structure of NMOS and PMOS in parallel, which can effectively inject signals in both the positive and negative half-cycles of the oscillator, achieving twice the injection efficiency of conventional circuits.

[0021] This invention also optimizes the transmission path, spatial layout, and performance of the ring traveling wave oscillator at the circuit structure and layout design levels, ensuring that the traveling wave propagates at a consistent distance in each segment within the ring, suppressing standing wave generation, reducing oscillation amplitude, and expanding the locking range. The resulting ring traveling wave oscillator, with a Möbius strip structure, exhibits a strictly rotationally symmetric circuit layout, significantly improving circuit stability. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a conventional Doppler radar as described in the background section.

[0023] Figure 2 The circuit diagram is for the ring oscillator described in the background section.

[0024] Figure 3 The circuit diagram is for the LC oscillator described in the background section.

[0025] Figure 4 The circuit diagram is shown for the ring traveling wave oscillator and the injection lock circuit used therein, as described in the background section.

[0026] Figure 5 The circuit diagram is for a ring traveling wave oscillator with a large injection lock-in range, as described in the background section.

[0027] Figure 6 This is a circuit diagram of the multi-injection locked ring traveling wave oscillator provided in Embodiment 1 of the present invention.

[0028] Figure 7 This is a circuit diagram of the mirror injection circuit used in Embodiment 1 of the present invention.

[0029] Figure 8 This is the layout design of the multi-injection locked ring traveling wave oscillator provided in Embodiment 1 of the present invention.

[0030] Figure 9 This is a circuit diagram of the Doppler radar provided in Embodiment 2 of the present invention. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "or / and" as used herein includes any and all combinations of one or more of the associated listed items.

[0033] Example 1

[0034] This embodiment provides a multi-injection locked ring traveling-wave oscillator. Each of the eight phase nodes in the ring traveling-wave oscillator is equipped with a mirror injection circuit. Each mirror injection circuit sequentially injects an injection signal with a 45° phase difference into each phase node, increasing the injection locking range to eight times that of single-node injection, or 64 times the equivalent signal power. Due to the non-correlation of thermal noise, multi-injection only increases the noise power by eight times, thus improving the signal-to-noise ratio by 9 dB. Furthermore, this invention arranges the transmission path of the ring traveling-wave oscillator in a double-layer layout space according to the structure of a Möbius strip, ensuring that the propagation distance of the traveling wave is consistent across all segments within the ring, suppressing standing wave generation; thereby reducing the oscillation amplitude and expanding the locking range of the oscillator.

[0035] Specifically, such as Figure 6As shown, the multi-injection locked ring traveling wave oscillator provided in this embodiment includes 16 inductive elements rf1~rf16; 4 variable capacitors Cv1~Cv4; and 4 stub injection circuits. In practical applications, the variable capacitors in this RF device can be interdigitated capacitors; the inductive elements can be high-layer metal wires. In the ring traveling wave oscillator of this embodiment, the 16 inductive elements rf1~rf16 are connected sequentially and end-to-end; every two adjacent inductive elements form a phase-shifting channel, and the phase difference between adjacent phase-shifting channels is 45°; thus forming a full-cycle loop. The stub injection circuit adopts a mirror structure design and has two output ports for injection signals. Each stub injection circuit can be used to generate a set of injection signals A and B with a phase difference of 180° based on a set of differential input signals Vinj+ and Vinj-; and output them to the injection ports in the corresponding two phase-shifting channels. Eight injection ports utilize a complementary injection circuit to sequentially input signals with a 45° phase difference. After superposition, these signals are equivalent to a single signal, resulting in a 64-fold power increase. Simultaneously, the noise levels are independent, and the power is eight times the original, significantly improving the system's signal-to-noise ratio. A variable capacitor is used to change the frequency of the ring traveling-wave oscillator. Since the oscillation frequency of a ring traveling-wave oscillator consisting only of transmission lines is related to the size of the ring, achieving the target 20GHz frequency would require a very large transmission line loop, greatly increasing chip cost. Therefore, in practical designs, capacitors are added to the loop to reduce the frequency.

[0036] To optimize the transmission path in the traveling-wave ring oscillator, this embodiment sequentially distributes eight phase-shifting channels in four orthogonal directions at the layout level. Each direction includes two phase-shifting channels with a phase difference of 180°, which are parallel to each other and located on the inner and outer sides of the same layer of the layout. In the ring path formed by the various phase-shifting channels, the inner phase-shifting channel in the previous direction is connected to the outer phase-shifting channel in the next direction; the outer phase-shifting channel in the previous direction is connected to the inner phase-shifting channel in the next direction; thus forming a two-layer Möbius strip structure; the Möbius strip is approximately square in shape on the plane.

[0037] Specifically, such as Figure 6 As shown, a first phase-shifting channel and a fifth phase-shifting channel are arranged parallel to each other in the first direction; a second phase-shifting channel and a sixth phase-shifting channel are arranged parallel to each other in the second direction; a third phase-shifting channel and a seventh phase-shifting channel are arranged parallel to each other in the third direction; and a fourth phase-shifting channel and an eighth phase-shifting channel are arranged parallel to each other in the fourth direction. The first phase-shifting channel is located in the inner layer of the first direction; the second phase-shifting channel is located in the outer layer of the second direction; the third phase-shifting channel is located in the inner layer of the third direction; the fourth phase-shifting channel is located in the outer layer of the fourth direction; the fifth phase-shifting channel is located in the outer layer of the first direction; the sixth phase-shifting channel is located in the inner layer of the second direction; the seventh phase-shifting channel is located in the outer layer of the third direction; and the eighth phase-shifting channel is located in the inner layer of the fourth direction.

[0038] Furthermore, in the layout of the ring traveling wave oscillator of this embodiment, the inner phase-shifting channel and the outer phase-shifting channel are electrically connected by two sets of wires in two adjacent directions. In this embodiment, these two sets of wires are arranged on the upper and lower layers at the same plane position in the layout, and the distance between the two sets of wires on the layout is equal.

[0039] Based on the above connection relationship, the transmission path of the ring traveling wave oscillator is as follows: First, starting from the first channel inside the first direction, it proceeds counterclockwise through the second channel outside the second direction; then through the third channel inside the third direction; then through the fourth channel outside the fourth direction; then through the fifth channel outside the first direction; then through the sixth channel inside the second direction; then through the seventh channel outside the third direction; then through the eighth channel inside the fourth direction; and then back to the first channel inside the first direction, thus forming a loop.

[0040] Based on this, in each direction of the layout, the first ends of the first inductive element in the inner phase-shifting channel and the outer phase-shifting channel serve as two injection ports with a phase gap of 180°, and are electrically connected to the two outputs of a mirror injection circuit. One end of the variable capacitor is connected to the tail end of the first inductive element in the inner phase-shifting channel, and the other end is connected to the tail end of the first inductive element in the outer phase-shifting channel.

[0041] Considering that two adjacent phase-shifting channels are always distributed on the inner and outer sides of adjacent directions, and there will be two conductors connecting different phase-shifting channels in adjacent directions, in order to ensure that the two conductors have the same length, suppress interference, and do not interfere with each other, this embodiment places the two conductors on the upper and lower layers of the layout, and adopts the following spatial layout method:

[0042] The conductor connecting the inner and outer phase-shifting channels in adjacent directions consists of a first branch segment connecting the first phase-shifting channel, a collinear end located in the middle, and a second branch segment connecting the second phase-shifting channel. The first branch segments connecting the ends of two phase-shifting channels in any direction are arranged along the upper and lower layers and extended inwards at a 45° angle, thus overlapping the upper and lower layers of the same point P in the layout plane. The second branch segments connecting the beginning ends of two phase-shifting channels in the next direction are also arranged along the upper and lower layers and extended inwards at a 45° angle, thus overlapping the upper and lower layers of the same point Q in the layout plane. The collinear segment in the layout plane comprises two mutually perpendicular and equidistant sub-segments; the two collinear segments connect nodes P and Q along the upper and lower layers, respectively.

[0043] by Figure 6Taking the spatial distribution of the conductors between the four transfer channels in the first and second directions as an example: the first branch segment at the end of the first transfer channel turns 45 degrees towards the fifth channel, and the first branch segment at the end of the fifth transfer channel turns 45 degrees towards the first channel. The two intersect at point P on the plane. Among them, the first branch segment at the end of the first transfer channel is located on the upper layer of the layout, and its end can be denoted as P1, while the first branch segment at the end of the fifth transfer channel is located on the lower layer of the layout, and its end can be denoted as P2.

[0044] The second branch of the second transfer channel turns 45 degrees towards the sixth channel, and the second branch of the sixth transfer channel turns 45 degrees towards the second channel. The two branches intersect at point Q on the plane. The second branch of the second transfer channel is located on the upper layer of the layout, and its end can be denoted as Q1. The second branch of the sixth transfer channel is located on the lower layer of the layout, and its end can be denoted as Q2.

[0045] Finally, in the upper and lower layers of the layout, P1 and Q1 are connected along the same trajectory, as are P2 and Q2. This forms corresponding collinear segments. Analyzing the above paths reveals that the trajectory of the conductor between the first and second shift channels is exactly the same as that of the conductor between the fifth and sixth shift channels, with only angular deviations. Furthermore, the paths of the two conductors in different directions are rotationally symmetrical about the center of the circular traveling wave oscillator layout. Therefore, this ensures that the traveling wave propagates at a consistent distance in each segment within the ring, suppressing the generation of standing waves.

[0046] It is important to emphasize that the spatial distribution of conductors between adjacent phase-shifting channels is not unique. The above description is only a typical example. In other embodiments, the spatial layout of the conductors can be further optimized. For example, the collinear segments can be changed from two mutually perpendicular straight lines to a straight line directly connecting points P and Q, etc. It is only necessary to ensure that the two sets of conductors in these adjacent directions are arranged on the upper and lower layers of the same plane in the layout, without interfering with each other; and that the distance between the two sets of conductors on the layout is equal.

[0047] In practical applications, the mirror injection circuit described above, which can output an injection signal with a 180° phase difference, can be used as follows: Figure 7As shown, the circuit configuration consists of four PMOS transistors P1-P4 and five NMOS transistors N1-N5. The sources of P1-P4 are connected to VDD; P1 is connected to the drain of N1. P2 is connected to the drain of N2; P1 is connected to the gate of N1 and serves as the non-inverting input port Vinj+; P2 is connected to the gate of N2 and serves as the inverting input port Vinj-. The drains of P1, N1, P3, and N3 are connected to the gates of P4 and N4, serving as the output port for one of the injected signals A; the drains of P2, N2, P4, and N4 are connected to the gates of P3 and N3, serving as the output port for one of the injected signals B. The sources of N3 and N4 are connected to the drain of N5; the gate of N5 is connected to the reference voltage signal Vbias; the sources of N1, N2, and N5 are connected to VSS.

[0048] Analysis of the circuit structure of the mirror injection circuit provided in this embodiment reveals that the output port of each injected signal adopts a complementary structure of NMOS and PMOS in parallel, thus effectively injecting signals in both the positive and negative half-cycles of the oscillator, with an injection efficiency twice that of traditional circuits.

[0049] In practical applications, this embodiment arranges the variable capacitors and mirror injection circuits in each direction in the region between the two phase-shifting channels in that direction; both are located on the same layer as the inductive elements in the inner and outer phase-shifting channels. With this spatial layout, the variable capacitors and mirror injection circuits in different directions are arranged rotationally symmetrically on the layout, with a rotation angle of 90°.

[0050] Finally, the overall layout of the multi-injection locked ring traveling wave oscillator designed in this embodiment is as follows: Figure 8 As shown in the figure, the circuit has a strictly symmetrical structure, which helps to improve system stability and makes it suitable for low-power scenarios such as the Internet of Things.

[0051] Example 2

[0052] Based on the performance advantages of the multi-injection locked ring traveling wave oscillator provided in Embodiment 1, this embodiment further provides a Doppler radar, such as... Figure 9 As shown, this Doppler radar employs a multi-injection locked ring traveling wave oscillator, as described in Example 1, to construct the required phase-locked loop (PLL) structure. Because this ring traveling wave oscillator can expand the injection locking range, it can improve the radar's sensitivity and detection range. The oscillator improves the system's signal-to-noise ratio through multi-point signal injection. The optimized oscillator structure also helps to achieve low-amplitude, phase-uniform ring traveling wave oscillations, enhancing the performance stability of the Doppler radar.

[0053] Building upon this, this embodiment also provides a physiological characteristic detection device for detecting human vital signs using non-contact vital sign detection technology. This device employs Doppler radar, as described above, to detect phase changes in echo signals caused by chest wall movement, thereby extracting respiratory and heartbeat information. Compared to other life detection technologies, the Doppler radar-based life detection provided in this embodiment offers higher stability and is suitable for non-contact scenarios such as burn monitoring and earthquake rescue.

[0054] Performance testing

[0055] To verify the performance of the multi-injection-locked ring traveling-wave oscillator provided by this invention, engineers conducted simulations and performance tests on relevant radar transceiver systems using a 22nm CMOS process. Simulations verified that the chip maintains phase uniformity even at oscillation amplitudes as low as 100mV, demonstrating extremely strong VSWR suppression performance, ensuring the system meets design requirements. To verify the system's injection-lock sensitivity, off-chip signal injection tests were performed on the chip. Under specific injection signal strengths, the frequency of the injection signal was adjusted, and it was observed whether the oscillator oscillated at the frequency of the injection signal. When the oscillator can lock, the maximum difference between the injection signal frequency and the oscillator's own frequency is the injection-lock range of the oscillator. When the injection-lock range is so small as to be indistinguishable (approximately 100kHz), it is considered the sensitivity limit of the oscillator's injection-lock range. Tests showed that the chip's injection-lock sensitivity is -90dBm, significantly higher than existing similar designs. These tests demonstrate that the Möbius strip structure and multi-injection-locking circuit structure of the multi-injection-locked ring traveling-wave oscillator proposed in this invention can ensure good phase uniformity at low oscillation amplitudes, thereby significantly improving the oscillator's injection-lock range.

[0056] The above-described embodiments are merely one implementation of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A multi-injection locked ring traveling wave oscillator, characterized in that, It includes 16 inductive elements rf1~rf16; 4 variable capacitors Cv1~Cv4 and 4 mirror injection circuits, wherein rf1~rf16 are connected in sequence and end to end; In the layout, every two adjacent inductive elements form a phase-shifting channel, and the eight phase-shifting channels are sequentially distributed in four orthogonal directions; the two phase-shifting channels in each direction are parallel to each other and located on the inner and outer sides of the same layer of the layout; among them, the inner phase-shifting channel in the upper direction is connected to the outer phase-shifting channel in the lower direction; the outer phase-shifting channel in the upper direction is connected to the inner phase-shifting channel in the lower direction; thus forming a two-layer Möbius strip structure; Two sets of conductors that connect the inner and outer phase shift channels in adjacent directions are arranged on the upper and lower layers at the same plane position in the layout, and the distance between them is equal. In each direction of the layout, the first end of the first inductive element in the inner phase-shifting channel and the outer phase-shifting channel serves as two injection ports with a phase gap of 180°, and is electrically connected to the two outputs of a mirror injection circuit; the two output ports of each mirror injection circuit are used to output a set of injection signals A and B with a phase difference of 180° according to a set of differential input signals; the tail end of the first inductive element in the inner phase-shifting channel and the outer phase-shifting channel is connected to the two ends of a variable capacitor.

2. The multi-injection locked ring traveling wave oscillator according to claim 1, characterized in that: The conductor that connects the inner and outer phase shifting channels in adjacent directions consists of a first branch segment connected to the first phase shifting channel, a collinear end located in the middle, and a second branch segment connected to the second phase shifting channel. The first branch segment connecting the ends of two phase shift channels in any direction is arranged along the upper and lower layers respectively and extended at a 45° offset to the inner side, thus overlapping the upper and lower layers of the same point P in the layout plane. The second branching segment connecting the first ends of the two phase shifting channels in the next direction is also arranged along the upper and lower layers respectively and extended at a 45° offset to the inner side, thus overlapping the upper and lower layers of the same point Q in the layout plane. Collinear segments in the layout plane consist of two sub-segments that are perpendicular to each other and equidistant; the two collinear segments are connected to nodes P and Q along the upper and lower layers respectively.

3. The multi-injection locked ring traveling wave oscillator according to claim 1, characterized in that: Each mirror injection circuit consists of four PMOS transistors P1~P4 and five NMOS transistors N1~N5. The sources of P1~P4 are connected to VDD; P1 is connected to the drain of N1; P2 is connected to the drain of N2; P1 is connected to the gate of N1 and serves as the non-inverting input port Vinj+; P2 is connected to the gate of N2 and serves as the inverting input port Vinj-; the drains of P1, N1, P3, and N3 are connected to the gates of P4 and N4, serving as the output port of one of the injection signals A; the drains of P2, N2, P4, and N4 are connected to the gates of P3 and N3, serving as the output port of one of the injection signals B; the sources of N3 and N4 are connected to the drain of N5; the gate of N5 is connected to the reference voltage signal Vbias; and the sources of N1, N2, and N5 are connected to VSS.

4. The multi-injection locked ring traveling wave oscillator according to claim 3, characterized in that: The variable capacitors and mirror injection circuits in each direction are arranged in the area between the two phase shift channels in the corresponding direction; Both are located on the same layer as the inductive elements in the inner and outer phase-shifting channels.

5. The multi-injection locked ring traveling wave oscillator according to claim 4, characterized in that: The variable capacitors and mirror injection circuits in different directions are arranged rotationally symmetrically on the layout, with a rotation angle of 90°.

6. The multi-injection locked ring traveling wave oscillator according to claim 5, characterized in that: It includes eight injection ports located on each phase-shifting channel, with a phase difference of 45° between the injection signals of the injection ports in adjacent phase-shifting channels.

7. The multi-injection locked ring traveling wave oscillator according to claim 1, characterized in that: The variable capacitor is an interdigitated capacitor.

8. The multi-injection locked ring traveling wave oscillator according to claim 1, characterized in that: The inductive element uses high-layer metal wires.

9. A Doppler radar, characterized in that: It employs a multi-injection locked ring traveling wave oscillator as described in any one of claims 1-8.

10. A physiological characteristic detection device, used to detect human vital signs through non-contact vital sign detection technology, characterized in that: It employs the Doppler radar as described in claim 9, which is used to detect phase changes in echo signals caused by human chest wall movement, thereby extracting respiratory and heartbeat information.

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