A millimeter wave radar LO phase synchronization system based on injection locking technology

Abstract

The utility model discloses a kind of millimeter wave radar LO phase synchronization systems based on injection locking technology, including voltage-controlled oscillator, multistage linkage injection locking frequency multiplier chain, resonant cavity collaborative design module, distributed phase synchronization network.It is applicable to multi-transmit multi-receive millimeter wave radar, or distributed millimeter wave radar and other high-performance systems.The utility model can greatly improve the consistency of radar signal, ensure that the LO phase synchronization error of different channels is less than 0.5°, the amplitude fluctuation is less than 0.1 dB in the ultra-wide band of more than 6GHz, the power fluctuation is less than 0.1dB, so the directivity error of radar beam after coherent synthesis can be greatly reduced, to prevent sidelobe deterioration and gain drop and other phenomena.

Description

Technical Field

[0001] This utility model relates to the field of millimeter-wave integrated circuit technology, and in particular to a phase synchronization system for millimeter-wave radar LO signals based on injection locking technology. Background Technology

[0002] To achieve beamforming, the front-end MMIC chip of millimeter-wave radar is usually in multiple transmit and receive mode, that is: N transmitters (Tx) transmit signals of different phases, which are received by M receivers (Rx). Through coherent synthesis technology, N times M virtual channels can be realized. Figure 1 and Figure 2 The diagrams show the structural schematic of a 2T4R (i.e., 2 transmit and 4 receive) MMIC and the analytical schematic of a virtual eight-channel transmit and receive beam.

[0003] When the consistency between N Tx and M Rx is poor, errors will be introduced after coherent synthesis, degrading radar beamforming performance, accuracy, and resolution. Taking the MMIC of NTMR as an example, the synthesized beam array factor at its transmitter can be expressed as:

[0004] Where β = 2π / λ, d m This refers to the antenna spacing. The phase error Δϕn can be approximated by a small angle as the beam angle deviation, i.e., Δθ. When the power of each path in Tx is inconsistent, the equivalent aperture efficiency decreases, leading to a significant drop in the actual antenna gain and causing an imbalance in the sidelobe distribution. If some channels have excessively high power, spectral aliasing will occur, resulting in grating lobes in the radar transmitted wave. If some channels have excessively low power, it will lead to a decrease in the overall signal-to-noise ratio.

[0005] For the reasons mentioned above, multi-transmitter, multi-receiver millimeter-wave radar (MMIC) must ensure consistency across all channels, with minimal fluctuations in both phase and power. Traditional local oscillator (LO) systems struggle to meet this requirement because the millimeter-wave band covers 76 to 81 GHz, making it difficult to maintain constant amplifier gain and resonator bandwidth across this wide frequency range. Summary of the Invention

[0006] To address the aforementioned problems in existing technologies, this utility model provides a millimeter-wave LO synchronization system based on injection locking technology, such as... Figure 3 As shown, this system includes a voltage-controlled oscillator, a multi-stage linkage injection-locked frequency multiplier chain, a resonant cavity collaborative design module, and a distributed phase synchronization network; The voltage-controlled oscillator operates at a low frequency to generate a fundamental frequency signal; The multi-stage linked injection-locked frequency multiplier chain consists of at least two cascaded injection-locked frequency multipliers (ILFDs) or injection-locked oscillators (ILOs), capable of multiplying the baseband signal to 76-81 GHz millimeter waves. This multi-stage linked ILFD can significantly reduce the design difficulty of the system phase-locked loop because the ILFD has very high nonlinear gain and excellent isolation. Therefore, this LO system will not require the use of buffers and impedance matching networks, which also greatly reduces the power consumption and noise of the LO link. The resonant cavity co-design module causes the center frequency of the resonant cavity of each injection-locked frequency multiplier or injection-locked oscillator to shift by a preset ratio, forming complementary power balance. The distributed phase synchronization network achieves real-time phase shaping by inserting injection-locked frequency multipliers or injection-locked oscillator modules in segments along the transmission line path.

[0007] When the frequency of the input signal is close to the natural frequency of the injection-locked circuit (or, for an ILFD, twice the frequency of the input signal must be close to the natural frequency of the ILFD), the injection-locked circuit can provide a huge nonlinear gain. For example, for an ILFD, when the frequency of its input signal is half of its natural frequency, even if the power of the input signal is as low as -90 dBm, the output of the ILFD will still be at full swing because no energy needs to be consumed to compensate for phase errors. In this case, the ILFD can provide a voltage gain greater than 90 dB, while the power consumption is often less than 2 mA. This is something that no other linear frequency multiplier can achieve.

[0008] The aforementioned millimeter-wave radar LO phase synchronization system based on injection locking technology is integrated into a single MMIC chip and supports a multi-transmit and multi-receive architecture with N×M virtual channels; it includes: an on-chip LO distribution network: which distributes the frequency-multiplied signal to N transmit channels and M receive channels through a power divider; Channel-level injection lockout buffer: Located at the entrance of each Tx / Rx channel, providing gain compensation, isolation enhancement, and harmonic filtering functions; The distributed phase synchronization network includes: dividing a long transmission line into several segments, each segment having a length less than λ / 10, where λ is the millimeter wave wavelength, and setting an injection-locked relay module between the segmented transmission lines to perform phase synchronization and harmonic filtering on the signal, with an isolation of >30 dB; The channel-level injection lock-in buffer is a low-quality-factor broadband ILO with a resonant frequency covering 76-81GHz and a relatively flat output power across the entire frequency band.

[0009] The multi-level linkage injection locking frequency multiplier chain satisfies: The center frequency of the k-th resonant cavity If the number of cascaded injection locking module levels is less than 4, then Δf is required.k >5% locking range; if the number of cascaded injection locking modules is more than 4, then Δf k It can be proportionally reduced to 1% of the locking range; adjacent level Δf k With opposite signs, the power complementarity condition is satisfied: , of which LR k This represents the locking range for the k-th level.

[0010] Preferably, when the frequency of the input signal deviates from the natural frequency of the injection-locked oscillator (ILO), this LO synchronization system can still balance them, keeping the power of the LO signal constant over a wide bandwidth of 76 to 81 GHz. Taking an injection-locked oscillator (ILO) as an example, according to the Adler equation, when the frequency of the injected locking signal is not at the center of the locking range, the amplitude v of the ILO's output signal... o Approximately: Where V DD Where is the power supply voltage (assuming the oscillator is at full swing), Δf is the frequency deviation, and LR is the lockout range of ILO; In designing each stage of the ILO or ILFD in this LO system, the center points of their resonant cavities are offset from one another according to a specific ratio, thereby achieving complementary and balanced signal power from a full-chain perspective. (See schematic diagram for reference.) Figure 4 ; The more ILFDs or ILOs cascaded in this LO system, the smaller the Δf between each stage, and the flatter the power of the final LO signal within the band, no longer changing with the frequency or power of the input signal.

[0011] Furthermore, the injection-locked frequency multiplier chain includes replaceable modules. Any stage in this LO system chain can be freely replaced, including but not limited to: injection-locked oscillator (ILO), injection-locked frequency multiplier (ILFD), injection-locked triplet (ILFT), or higher-order injection-locked multiple multiplier (ILFM). When choosing different injection-locked modules for replacement, the magnitude of the resonant cavity frequency offset Δf between them needs to be adjusted to maintain power balance, but the underlying logic remains unchanged.

[0012] Furthermore, the output of the millimeter-wave radar LO phase synchronization system based on injection locking technology satisfies the following requirements: within the 76-81 GHz full frequency band, the phase synchronization accuracy satisfies the phase difference between multiple channels < 0.5°; and the power consistency satisfies the power fluctuation between channels < 0.1 dB.

[0013] Furthermore, this LO system is suitable for cascaded or distributed radar architectures—using a single LO to drive various transceivers distributed at the far end of the PCB, including: Cross-chip LO distribution: Multiple MMICs are connected via PCB transmission lines, and each MMIC has an ILO relay module at its input; Phase error suppression: Phase shift caused by path length difference is corrected by ILO in real time, and the residual after correction is <1°; If there are many transceivers and their positions are asymmetrical, phase ambiguity is likely to occur. The LO system of this utility model can perform multiple phase corrections on the PCB, which greatly improves channel consistency. When this LO system is applied to on-chip signal distribution, the link is changed to a distributed structure, with the transmission lines distributed among the various injection and locking modules. This avoids using long transmission lines at once and reduces phase errors caused by transmission line mismatch. Because each injection and locking does not change the signal phase, even if the frequencies of the input and output signals are 1 to N times the frequency, their phases are always synchronized. Using this LO system is equivalent to performing phase synchronization shaping every time a short section of the transmission line is passed, ensuring that the error of the final output signal is minimized.

[0014] The more injection-locked modules cascaded in a LO system, the better the phase synchronization effect. In a multi-transmitter / multi-receiver millimeter-wave chip, the more transmit and receive channels there are, the more complex the LO distribution system becomes, and the worse the consistency of each channel becomes. For example, it is almost impossible to achieve perfect central symmetry of the LO transmission lines connecting each receiver or transmitter in an 8T8R 77 GHz millimeter-wave front-end chip. Using this LO synchronization system, the long transmission line can be broken into several small segments, and ILFD or ILO can be inserted between each segment to synchronize their phase at all times, ensuring that the transceiver signals are consistent. At the same time, the LO signal power of each channel is balanced to ensure that they are flat in the 76 to 81 GHz wideband. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the 2T4R MMIC structure; Figure 2 This is a schematic diagram illustrating the analysis of a virtual eight-channel transmit / receive beam; Figure 3 This is a schematic diagram of the structure of this utility model; Figure 4 This is a schematic diagram of the multi-stage injection-locked resonant cavity design and power equalization analysis in this utility model; Figure 5This is the single-chip NTMR millimeter-wave MMIC on-chip LO system in Embodiment 1 of this utility model; Figure 6 This is a schematic diagram of the LO system of the multi-MMIC cascaded millimeter-wave radar or distributed radar in Embodiment 2 of this utility model; Figure 7 This is a schematic diagram of the simulation results of the four-channel Tx LO signal in Embodiment 1 of this utility model; Figure 8 This is a schematic diagram of the simulation results of the 5GHz to 80GHz LO signal in Embodiment 2 of this utility model; Detailed Implementation

[0017] To make the objectives and advantages of this utility model clearer, the present utility model will be specifically described below with reference to embodiments. It should be understood that the following text is only used to describe one or more specific embodiments of this utility model and does not strictly limit the specific scope of protection claimed by this utility model.

[0018] Example 1 focuses on a radar MMIC chip with N transmitters and M receivers, utilizing this LO phase synchronization system to provide carrier signals for N transmitters and M receivers. For example... Figure 5As shown, the VCO oscillation frequency range is approximately 18.5 to 20.5 GHz. After quadrupling the frequency, it produces the required 76 to 81 GHz millimeter-wave LO signal (with a certain margin). The first-stage injection-locked frequency multiplier (ILFD) multiplies the VCO frequency by 2, resulting in a frequency range of 37 to 41 GHz. The LC resonator of ILFD1 is offset by a Δf from the second-stage frequency multiplier, so the multiplied signal is not full-swing, but very close. After the second-stage frequency multiplier, the signal becomes 74 to 82 GHz, meeting the frequency modulation range of millimeter-wave radar. The center point of the LC resonator of the second-stage ILFD2 is offset by Δf in the opposite direction, precisely canceling the frequency offset effect of ILFD1. As a result, the output signal of ILFD2 has constant power within a large bandwidth of 76 to 81 GHz—although not full-swing, the amplitude fluctuation is less than 0.05 dB within the 74 to 82 GHz range. After ILFD2, the LO signal passes through a quarter-wavelength transmission line and a power divider, transforming from one path to N+M paths, which are then transmitted to N transmitters and M receivers respectively. Upon arrival at the transceiver, the LO system employs a wideband injection-locked oscillator (ILO) operating in the millimeter-wave band before each channel. Its functions are: (1) to replace the traditional buffer and provide gain, compensating for energy loss during transmission; (2) to provide input-output isolation greater than 30 dB, preventing inter-channel interference; (3) to filter out noise: because the ILO possesses first-order filtering characteristics, it can filter out harmonics and interference signals coupled into the LO system during transmission, ensuring that the phase noise of the LO signal is unaffected; and (4) to perform phase shaping: providing a consistent load for the LO system, avoiding phase errors caused by inconsistent input impedances between the transceiver and transmitter. This LO synchronization system ultimately achieves the following at the millimeter-wave front end of the NTMR: inter-channel power fluctuation less than 0.1 dB, phase error fluctuation less than 0.5°, and overall power consumption less than 20 mW (including VCO).

[0019] Example 2 illustrates the LO synchronization scheme for cascaded and distributed radar. To achieve high-channel and dense point clouds, and to ensure fine azimuth and elevation resolution, millimeter-wave radar often employs a cascaded approach. This involves cascading two to eight millimeter-wave microcontrollers (MMICs) with a single signal processing chip, using coherent synthesis technology to achieve multiple virtual channels. Common imaging radars require at least 30,000 point clouds and 192 channels. This means that at least four 3T4R MMICs need to be cascaded before being connected to the signal processing chip. One MMIC acts as the master, providing LO signals to all MMICs, while the other MMICs are slaves, only able to use the LO signal supplied by the master chip. Distributed radar works similarly, using a single LO chip on the PCB to drive several transceiver chips. The LO desynchronization problems faced by both are very similar: when the LO signal transmission path lengths are unequal (e.g., between chips / boards) or there are significant manufacturing errors, phase and power differences are introduced between different channels, leading to decreased coherence of the synthesized signal, drastic deterioration of phase noise, and a decline in radar beamforming performance. The performance loss caused by signal inconsistency between channels is more severe in high-channel radars. Furthermore, the complexity of traditional tree-structured distribution networks increases exponentially, and impedance matching becomes difficult, leading to a deterioration in signal integrity. These problems can be addressed and improved through this LO synchronization system.

[0020] In such Figure 6 In Example 2, the VCO of the LO chip generates a 5 GHz signal (frequency modulation range of 4.5 to 5.5 GHz), which is transmitted off-chip and distributed to three independent radars via board-level transmission lines. Each radar chip employs a four-stage cascaded ILFD LO synchronization system. Simultaneously with transmitting the 5 GHz signal, the LO system transmits the VCO's frequency modulation signal, i.e., the control word controlling the frequency modulation capacitor array or the frequency modulation voltage controlling the varactor diode. Other radars, upon receiving the 5 GHz signal, simultaneously receive this control voltage, which is used to adjust their own resonant frequency in real time, ensuring that the received 5 GHz LO signal is in the middle of their locking range. This maximizes the output amplitude of the ILFD, achieving full swing, determined only by the power supply voltage and independent of the input frequency. As a result, after four-stage cascaded ILFDs, the 5 GHz signal is multiplied to 80 GHz (frequency modulation range of 72 to 88 GHz), the phase of the LO signal is synchronized with the VCO's 5 GHz signal, the inter-channel phase error is less than 1°, and the amplitude fluctuation of the LO signal is less than 0.1 dB. To further reduce the phase error between channels, the transmission lines on the PCB can be divided into several segments, and a relay phase shaping ILO can be inserted between each segment. This can further reduce the phase error to within 0.2°.

[0021] like Figure 7This is a schematic diagram of the simulation results of the four-channel Tx LO signal in Example 1. The simulation results show that the voltage amplitude of the four transmit channels (LO_Tx1 to LO_Tx4) maintains a transient response of 180 mV to 0 mV within a time window of 7.16-7.195 ns. The waveforms exhibit highly consistent synchronization characteristics with minimal deviation between channels, indicating that the LO phase synchronization system effectively achieves phase alignment and amplitude stability of multi-carrier signals and has a fast settling time. This further verifies the distributed driving capability of the 76-81 GHz LO signal in the millimeter-wave radar system and meets the stringent requirements of the N-transmit M-receive architecture for phase consistency.

[0022] like Figure 8 The simulation results of the 5GHz to 80GHz LO signal in Example 2 are shown. The simulation results demonstrate the transient response characteristics of the 5GHz to 80GHz LO signal: 1. Input stage: The 5GHz VCO signal (6vco) exhibits a stable amplitude of 363.1mV, with a frequency modulation range of 4.5-5.5 GHz and a clean time-domain waveform; 2. Output stage: After four stages of ILFD frequency multiplication, the 80GHz signal maintains precise synchronization within a time window of 7.33-7.34 ns. This verifies the linearity of the cascaded frequency multiplication system, the effectiveness of the system's phase synchronization mechanism, and the good stability of cross-chip phase-locked loop.

[0023] In summary, this LO phase synchronization system can meet the strict synchronization requirements of distributed radar arrays for high-frequency LO signals, satisfy the phase consistency requirements of multi-transmitter multi-receiver millimeter-wave radar MMICs, and significantly improve the consistency of radar signals.

Claims

1. A millimeter-wave radar LO phase synchronization system based on injection locking technology, characterized in that... This includes a voltage-controlled oscillator, a multi-stage linkage injection-locked frequency multiplier chain, a resonant cavity collaborative design module, and a distributed phase synchronization network. The voltage-controlled oscillator is used to generate the fundamental frequency signal; The multi-stage linkage injection-locked frequency multiplier chain is composed of at least two stages of injection-locked frequency multipliers or injection-locked oscillators cascaded together, which multiplies the base frequency signal to a high-frequency carrier, wherein the high-frequency carrier is a 76-81GHz millimeter wave. The resonant cavity co-design module causes the center frequency of the resonant cavity of each injection-locked frequency multiplier or injection-locked oscillator to shift by a preset ratio, forming complementary power balance. The distributed phase synchronization network achieves real-time phase shaping by inserting injection-locked frequency multipliers or injection-locked oscillator modules in segments along the transmission line path.

2. The millimeter-wave radar LO phase synchronization system based on injection locking technology according to claim 1, characterized in that: The multi-level linkage injection locking frequency multiplier chain satisfies: The center frequency of the k-th resonant cavity If the number of cascaded injection locking module levels is less than 4, then Δf is required. k >5% locking range; if the number of cascaded injection locking modules is more than 4, then Δf k It can be proportionally reduced to a 1% locking range; Adjacent level Δf k With opposite signs, the power complementarity condition is satisfied: , of which LR k This represents the locking range for the k-th level.

3. The millimeter-wave radar LO phase synchronization system based on injection locking technology according to claim 1, characterized in that: The distributed phase synchronization network includes: dividing a long transmission line into several segments, each segment having a length less than λ / 10, where λ is the millimeter wave wavelength, and placing injection-locked relay modules between the segmented transmission lines to perform phase synchronization and harmonic filtering on the signal, with an isolation of >30 dB.

4. A millimeter-wave radar LO phase synchronization system based on injection locking technology according to claim 1, characterized in that: The system is integrated into a single MMIC chip, including: On-chip LO distribution network: Distributes the frequency-multiplied signal to N transmit channels and M receive channels through a power divider; Channel-level injection lockout buffer: Located at the entrance of each Tx / Rx channel, it provides gain compensation, isolation enhancement, and harmonic filtering functions.

5. A millimeter-wave radar LO phase synchronization system based on injection locking technology according to claim 4, characterized in that, The channel-level injection lock-in buffer is a low-quality-factor broadband ILO with a resonant frequency covering 76-81 GHz and a relatively flat output power across the entire frequency band.

6. A millimeter-wave radar LO phase synchronization system based on injection locking technology according to claim 1, characterized in that: The system output meets the following requirements: within the 76-81 GHz full frequency band, the phase synchronization accuracy meets the requirement that the phase difference between multiple channels is <0.5°; and the power consistency meets the requirement that the power fluctuation between channels is <0.1 dB.

7. A millimeter-wave radar LO phase synchronization system based on injection locking technology according to claim 1, characterized in that, Suitable for cascaded or distributed radar architectures, including: cross-chip LO distribution: multiple MMICs are connected via PCB transmission lines, and each MMIC has an ILO relay module at its inlet; phase error suppression: phase shift caused by path length difference is corrected by ILO in real time, and the residual after correction is <1°.

8. A millimeter-wave radar LO phase synchronization system based on injection locking technology according to claim 1, characterized in that, The injection-locked frequency multiplier chain includes replaceable modules, including but not limited to ILO, ILFD, injection-locked triple frequency multiplier, or higher-order injection-locked multiplier; during replacement, power balance is maintained by adjusting the resonant cavity frequency offset Δf.

9. A millimeter-wave radar LO phase synchronization system based on injection locking technology according to claim 1, characterized in that: It supports a multi-transmitter, multi-receiver architecture with N×M virtual channels.

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