Band-pass filter circuit for millimeter wave radar

Abstract

The utility model discloses a band-pass filter circuit for a millimeter wave radar, which belongs to the technical field of millimeter wave radars, and comprises multiple stages of cascaded filter amplification units, and each stage of filter amplification unit comprises a low-pass filter unit, a high-pass filter unit and an amplification unit which are connected in sequence; according to the utility model, each stage of filtering and amplifying unit adopts hybrid filtering, out-of-band noise is more accurately suppressed, the amplifying unit realizes signal amplification, and the gain of the filtering circuit is improved; meanwhile, the narrow-band-pass characteristic is formed through cascading, and the performance of the millimeter wave radar can be optimized.

Description

Technical Field

[0001] This utility model relates to the field of millimeter-wave radar technology, and in particular to a bandpass filter circuit for millimeter-wave radar. Background Technology

[0002] The history of millimeter-wave radar technology can be traced back to military radar systems of the 1940s. Its core technology lies in utilizing electromagnetic waves in the 30GHz to 300GHz frequency band to achieve high-precision target detection. With breakthroughs in frequency-modulated continuous wave (FMCV) technology and the introduction of multiple-input multiple-output (MIMO) arrays, millimeter-wave radar has gradually shifted from the military field to the civilian autonomous driving field. In 2016, Texas Instruments launched the first 77GHz automotive radar chipset, marking millimeter-wave radar as a core sensor for advanced autonomous driving.

[0003] The filtering circuits used in existing millimeter-wave radars are typically single-stage or two-stage cascaded structures, which only have frequency filtering capabilities and have the following shortcomings:

[0004] Single function: Each stage only performs filtering and has no signal amplification capability. The signal-to-noise ratio decreases after high-frequency signals are attenuated through multiple stages.

[0005] Bandwidth versus gain conflict: High-gain designs tend to lead to bandwidth broadening and deterioration of frequency selectivity;

[0006] Fixed parameters: The center frequency and bandwidth depend on the initial design and cannot adapt to frequency band drift in actual applications.

[0007] Therefore, it is urgent to improve the existing filtering circuits to optimize the performance of millimeter-wave radar. Utility Model Content

[0008] The purpose of this invention is to overcome the problems of existing filter circuits, optimize the performance of millimeter-wave radar, and provide a bandpass filter circuit for millimeter-wave radar.

[0009] The objective of this utility model is achieved through the following technical solution:

[0010] A bandpass filter circuit for millimeter-wave radar is provided, comprising cascaded multi-stage filter amplification units. Each stage of the filter amplification unit includes a low-pass filter unit, a high-pass filter unit, and an amplification unit connected in sequence. The low-pass filter unit is composed of a low-pass filter resistor and a low-pass filter capacitor connected in series, and the high-pass filter unit is composed of a high-pass filter capacitor and a high-pass filter resistor connected in series. The input terminal of the high-pass filter capacitor is connected between the low-pass filter resistor and the low-pass filter capacitor. The amplification unit includes a transimpedance amplifier and a feedback resistor. The positive input terminal of the transimpedance amplifier is connected between the high-pass filter capacitor and the high-pass filter resistor, and the feedback resistor is connected to the transimpedance amplifier. The low-pass filter resistor of the first-stage filter amplification unit is connected to the signal input terminal, and the transimpedance amplifier of the last-stage filter amplification unit is connected to the signal output terminal.

[0011] In some embodiments, the low-pass filter capacitor and the high-pass filter capacitor are both surface-mount capacitors, and the low-pass filter resistor, the feedback resistor, and the high-pass filter resistor are all thin-film resistors.

[0012] In some embodiments, a thermistor is connected in parallel to each stage of the filter amplification unit.

[0013] In some embodiments, the input and output terminals of each filter amplification unit are matched with a 50Ω impedance.

[0014] In some embodiments, adjacent filter amplification units are connected by an isolation resistor.

[0015] In some embodiments, a four-stage filtering amplification unit is included, wherein the gains of the first two stages of the filtering amplification unit are 4.8dB and 9.5dB, respectively, and the gains of the last two stages of the filtering amplification unit are 12dB and 5.7dB, respectively.

[0016] It should be further noted that the technical features corresponding to the above embodiments can be combined or substituted to form new technical solutions.

[0017] Compared with the prior art, the beneficial effects of this utility model are:

[0018] 1. This utility model includes cascaded multi-stage filtering and amplification units. Each stage of the filtering and amplification unit includes a low-pass filter unit, a high-pass filter unit, and an amplification unit connected in sequence. Each stage of the filtering and amplification unit adopts hybrid filtering to more accurately suppress out-of-band noise. The amplification unit embeds a transimpedance amplifier and, together with a feedback resistor, realizes signal amplification, improves the gain of the filtering circuit, and can compensate for subsequent cascade attenuation. At the same time, the narrow bandpass characteristic is formed by cascading, which can optimize the performance of millimeter-wave radar.

[0019] 2. In one example, this invention uses a precision surface-mount capacitor with an error of ±0.1% and a thin-film resistor with a temperature coefficient of ±5ppm / ℃, achieving a Q value of 80 (compared to a conventional filter Q value ≤50), and improving frequency selectivity by 60%.

[0020] 3. In one example, each stage of the filter amplification unit of this invention is connected in parallel with a thermistor to form a temperature compensation network. The resistance value is dynamically adjusted through a feedback circuit to compensate for the center frequency shift caused by temperature drift.

[0021] 4. In one example, the multi-stage filtering and amplification unit of this invention adopts a progressive gain distribution, which improves the signal strength while avoiding nonlinear distortion caused by high gain in a single stage.

[0022] 5. In one example, the input and output terminals of each stage of the filter amplification unit of this invention are matched with a 50Ω impedance, and adjacent filter amplification units are connected by an isolation resistor to reduce interstage coupling interference and return loss ≤-15dB.

[0023] 6. In one example, the first-stage filter in a fourth-order bandpass filter circuit has a center frequency of 24.12 GHz, a bandwidth of 240 MHz, and a gain of 4.8 dB. Simulation results show an attenuation of 68 dB in both low and high frequencies. The second-stage filter has a center frequency of 24.16 GHz, a bandwidth of 240 MHz, and a gain of 9.5 dB. Simulation results show an attenuation of 58 dB in both low and high frequencies. The third-stage filter has a center frequency of 24.13 GHz, a bandwidth of 240 MHz, and a gain of 12 dB. Simulation results show an attenuation of 45 dB in both low and high frequencies. The fourth-stage filter has a center frequency of 24.09 GHz, a bandwidth of 240 MHz, and a gain of 5.7 dB. Simulation results show an attenuation of 42 dB in both low and high frequencies. The total amplifier gain reaches 32 dB, with a maximum attenuation of 68 dB in both low and high frequencies. Attached Figure Description

[0024] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. The accompanying drawings are used to provide a further understanding of the present application and constitute a part of the present application. The same reference numerals are used in these drawings to denote the same or similar parts. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation of the present application.

[0025] Figure 1 This is a structural diagram of a cascaded multi-stage filtering and amplification unit shown in an embodiment of the present invention;

[0026] Figure 2 This is a structural diagram of each stage of the filtering and amplification unit shown in an embodiment of the present invention;

[0027] Figure 3This is a structural diagram of a fourth-order bandpass filter circuit shown in an embodiment of the present invention. Detailed Implementation

[0028] The technical solution of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0029] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0030] Furthermore, the technical features involved in the different embodiments of this utility model described below can be combined with each other as long as they do not conflict with each other.

[0031] Reference Figures 1-2 In one exemplary embodiment, a bandpass filter circuit for millimeter-wave radar includes cascaded multi-stage filter amplification units. The center frequency of each filter amplification unit is finely adjusted around 24.1 GHz. Each filter amplification unit includes a low-pass filter unit, a high-pass filter unit, and an amplification unit connected in sequence, so that each filter amplification unit has both amplification and filtering functions. The aim is to filter and enhance 24 GHz signals.

[0032] Combination Figure 3 A fourth-order bandpass filter circuit structure diagram is provided. The low-pass filter unit is composed of a low-pass filter resistor and a low-pass filter capacitor connected in series. The high-pass filter unit is composed of a high-pass filter capacitor and a high-pass filter resistor connected in series. The input terminal of the high-pass filter capacitor is connected between the low-pass filter resistor and the low-pass filter capacitor. The amplification unit includes a transimpedance amplifier and a feedback resistor. The positive input terminal of the transimpedance amplifier is connected between the high-pass filter capacitor and the high-pass filter resistor. The feedback resistor is connected to the transimpedance amplifier. The low-pass filter resistor of the first-stage filtering amplification unit is connected to the signal input terminal, and the transimpedance amplifier of the last-stage filtering amplification unit is connected to the signal output terminal.

[0033] Taking the first-stage filter amplification unit as an example, its structure integrates a low-pass filter unit (composed of R1 and C1), a high-pass filter unit (composed of C3 and R7), and an amplification unit. This combined circuit ensures that unwanted frequency components are filtered out while achieving appropriate gain amplification of the signal. The amplification unit embeds a transimpedance amplifier (IC), which, together with negative feedback resistors (R3, R4), amplifies the signal, achieving a minimum gain of 4.8dB per stage. This compensates for subsequent cascade attenuation, resulting in a total gain of 32dB (compared to ≤10dB for conventional filters). The remaining three stages are similar in structure to the first-stage filter amplification unit and will not be described in detail here.

[0034] Given the strict definition of the 24GHz millimeter-wave band (23.975GHz to 24.225GHz), the center frequency of this circuit is set at 24.1GHz, and a high-Q performance design is employed. A high Q value not only means excellent frequency selectivity for the filter but also higher gain at the resonant frequency, thereby enhancing signal stability and reliability. The center frequency of each stage is finely adjusted around 24.1GHz (e.g., 24.12GHz for the first stage, 24.16GHz for the second stage), forming a narrow-bandpass characteristic through cascading, with a bandwidth of 240MHz (conventional filter bandwidth ≥500MHz) and out-of-band rejection ≥42dB (conventional filter ≤30dB). The resistor and capacitor parameters of each filter stage need to be calculated and adjusted to ensure that the entire circuit can focus at this frequency point. Actual circuit specifications are shown in Table 1.

[0035] Table 1. Parameters of each component in the four-stage bandpass filter circuit.

[0036]

[0037] Both the low-pass and high-pass filter capacitors are surface-mount capacitors, while the low-pass filter resistor, feedback resistor, and high-pass filter resistor are all thin-film resistors. Specifically, the filter circuit uses precision surface-mount capacitors with an error of ±0.1% and thin-film resistors with a temperature coefficient of ±5ppm / ℃, achieving a Q value of 80 (compared to ≤50 for conventional filters) and improving frequency selectivity by 60%.

[0038] Furthermore, each stage of the filter amplification unit is connected in parallel with thermistors (R3, R5, R13, R15) to form a temperature compensation network. The resistance value is dynamically adjusted through the feedback circuit to compensate for the center frequency shift caused by temperature drift.

[0039] Furthermore, each stage of the filter amplification unit is matched with a 50Ω impedance at its input and output terminals, forming an impedance matching design.

[0040] Furthermore, adjacent filter amplification units are connected by isolation resistors (such as R9 and R19) to reduce interstage coupling interference. The return loss of conventional filters is ≥-10dB, while the return loss of this application is ≤-15dB.

[0041] Furthermore, the gains of the first two filter amplification units are 4.8dB and 9.5dB, respectively, and the gains of the last two filter amplification units are 12dB and 5.7dB, respectively.

[0042] In summary, the first-stage filter in this four-stage bandpass filter circuit has a center frequency of 24.12 GHz, a bandwidth of 240 MHz, and a gain of 4.8 dB. Simulation results show an attenuation of 68 dB in both low and high frequencies. The second-stage filter unit has a center frequency of 24.16 GHz, a bandwidth of 240 MHz, and a gain of 9.5 dB. Simulation results show an attenuation of 58 dB in both low and high frequencies. The third-stage filter unit has a center frequency of 24.13 GHz, a bandwidth of 240 MHz, and a gain of 12 dB. Simulation results show an attenuation of 45 dB in both low and high frequencies. The fourth-stage filter unit has a center frequency of 24.09 GHz, a bandwidth of 240 MHz, and a gain of 5.7 dB. Simulation results show an attenuation of 42 dB in both low and high frequencies. The total amplifier gain reaches 32 dB, with a maximum attenuation of 68 dB in both low and high frequencies.

[0043] The above detailed embodiments are a detailed description of the present utility model. It should not be considered that the specific embodiments of the present utility model are limited to these descriptions. For those skilled in the art, several simple deductions and substitutions can be made without departing from the concept of the present utility model, and all of these should be considered to fall within the protection scope of the present utility model.

Claims

1. A bandpass filter circuit for millimeter-wave radar, characterized in that, The system includes cascaded multi-stage filtering and amplification units. Each stage comprises a low-pass filter unit, a high-pass filter unit, and an amplification unit connected in series. The low-pass filter unit consists of a low-pass filter resistor and a low-pass filter capacitor connected in series, and the high-pass filter unit consists of a high-pass filter capacitor and a high-pass filter resistor connected in series. The input terminal of the high-pass filter capacitor is connected between the low-pass filter resistor and the low-pass filter capacitor. The amplification unit includes a transimpedance amplifier and a feedback resistor. The positive input terminal of the transimpedance amplifier is connected between the high-pass filter capacitor and the high-pass filter resistor, and the feedback resistor is connected to the transimpedance amplifier. The low-pass filter resistor of the first-stage filtering and amplification unit is connected to the signal input terminal, and the transimpedance amplifier of the last-stage filtering and amplification unit is connected to the signal output terminal.

2. The bandpass filter circuit for millimeter-wave radar according to claim 1, characterized in that, Both the low-pass and high-pass filter capacitors are surface-mount capacitors, and the low-pass filter resistor, feedback resistor, and high-pass filter resistor are thin-film resistors.

3. The bandpass filter circuit for millimeter-wave radar according to claim 1, characterized in that, Each stage of the filtering and amplification unit is connected in parallel with a thermistor.

4. The bandpass filter circuit for millimeter-wave radar according to claim 1, characterized in that, Each stage of the filter amplification unit is matched with a 50Ω impedance at both its input and output.

5. A bandpass filter circuit for millimeter-wave radar according to claim 4, characterized in that, Adjacent filter amplification units are connected by isolation resistors.

6. A bandpass filter circuit for millimeter-wave radar according to claim 1, characterized in that, It includes a four-stage filtering and amplification unit, wherein the gains of the first two stages of the filtering and amplification unit are 4.8dB and 9.5dB, respectively, and the gains of the last two stages of the filtering and amplification unit are 12dB and 5.7dB, respectively.

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