CN109782361B - A high-gain receiver for millimeter-wave passive imaging - Google Patents

Abstract

The invention belongs to the technical field of integrated circuits, and particularly relates to a high-gain receiver applied to millimeter wave passive imaging. The invention adopts a super-regenerative receiver circuit, which comprises: the circuit comprises an input matching network, a transformer matching network and an envelope detector, wherein the transformer matching network comprises a differential transistor pair. The invention can be used in passive imaging systems. Compared with the traditional passive millimeter wave imaging system, the high-gain receiver provided by the invention can realize ultra-wideband electromagnetic wave energy acquisition and 100dB gain, and can realize dynamic adjustment of the receiving range of the receiver by dynamically adjusting the bias voltage of the envelope detector. The invention adopts the gallium arsenide 0.15um process to realize the passive imaging from 80GHz to 100 GHz. The noise coefficient of the receiver is only 1.5dB, the gain of the receiver is 100dB, the dynamic range is 60dB, and the invention thoroughly overcomes the problem of bandwidth change caused by process error and temperature drift.

Description

A high-gain receiver for millimeter-wave passive imaging

technical field

The invention belongs to the technical field of integrated circuits, and in particular relates to a high-gain receiver used in passive imaging circuits.

Background technique

The microwave frequency is in the range of 30-300GHz, that is, the electromagnetic wave with the wavelength in the range of 1-10mm is defined as millimeter wave, and its wavelength range is in the middle of microwave and infrared light wave. Therefore, it not only has certain common characteristics with microwave and infrared wave, but also has many characteristics. Unique feature. Compared with microwave, when the antenna diameter is the same, the advantages of millimeter wave are reflected in narrow beam, good directivity, excellent anti-interference, high resolution, and good penetration characteristics in plasma; Compared with millimeter wave, millimeter wave has better penetration ability and strong diffraction performance, and the attenuation degree of gas, smoke, fog and other substances under the atmospheric window is extremely small, so in severe weather conditions or heavy smoke and dust conditions such as military applications, Millimeter wave passive imaging technology has greater advantages than traditional photoelectric imaging technology. The passive millimeter-wave imaging system has an all-day uninterrupted working mode and extremely high resolution, which can effectively identify target objects in the surrounding environment. Therefore, millimeter wave passive imaging technology has important practical value in remote sensing, navigation, security inspection and other fields.

The receiver front-end system is one of the key components of the entire millimeter-wave passive imaging system. Good RF front-end performance is very important for the subsequent processing of the received signal. The technical indicators of the receiver can represent the most important technical level of the millimeter wave imaging system. The receiver has the functions of amplifying the signal, linear conversion, and calibration. The sensitivity, linearity and stability of the receiver can characterize the corresponding indicators of the imaging system. The sensitivity of a receiver characterizes the minimum input signal strength at which the receiver can work properly. Sensitivity is related to system noise figure, bandwidth and signal modulation. Different bandwidths will affect the noise power entering the system and thus affect the sensitivity of the receiver; while different modulation methods have different requirements for the minimum detectable signal-to-noise ratio under the premise of ensuring that the bit error rate meets the requirements, which will affect the sensitivity of the receiver. The lower limit of the receiver's dynamic range is determined by the noise floor of the receiver system, while the upper limit is determined by nonlinear indicators such as the spurious-free dynamic range and the third-order truncation point. For the receiver system, the useful signals of the entire frequency band must be received to ensure that the signal is not distorted, that is, the passband of the receiver system. If the passband is too narrow, the useful broadband signals cannot pass through, resulting in signal distortion. Since the noise power is proportional to the bandwidth, the passband that is too wide will cause the noise power entering the system to be too large, which will also reduce the signal-to-noise ratio. . Therefore, the development of ultra-wideband high-gain receivers is of great significance for the technological development of millimeter-wave imaging.

SUMMARY OF THE INVENTION

In view of this, the present invention aims to provide a high-gain receiver applied to millimeter wave passive imaging.

The high-gain receiver applied to millimeter-wave passive imaging provided by the present invention, its circuit structure is shown in FIG. 1, including the following modules: input matching network 101, ultra-wideband transformer matching network 102, envelope detector 104; ultra-wideband There are differential NMOS transistor pairs 103 in the transformer matching network 102, where:

The input matching network 101 includes four on-chip passive inductors, the middle tap of the output inductor at the right end is connected to the bias voltage _VB , and the upper and lower ends are respectively connected with the two differential NMOS transistor pairs of the ultra-wideband transformer matching network 102. grid connection;

In the UWB transformer matching network 102, there are four stages of transformers; each stage of the transformer is composed of differential NMOS transistor pairs and four on-chip passive inductors; the output terminals of the two differential NMOS transistor pairs, namely the drains, are connected to the two outputs At the upper and lower ends of the inductor, the sources of the differential NMOS transistor pairs are grounded, and the gates of the differential NMOS transistor pairs are respectively connected to the upper and lower ends of the two input inductors; the middle taps of the two output inductors are connected to the power supply voltage VDD; these two The output inductors are coupled to the input of the next-stage differential NMOS transistor pair through the inductance of the bias voltage _VB ; the signal is coupled to the input end of the envelope detector 104 through a four-stage transformer;

The envelope detector 104 includes two output differential NMOS transistor pairs M3, two input resistors _RB , one output resistor RD and two DC blocking capacitors _{C A} ; the two input inductors are connected to the two DC blocking capacitors C One end of _A and the other ends of the two DC blocking capacitors C _A are respectively connected to the gates of the output differential NMOS transistor pair M3, and at the same time, the bias voltage V _B provides bias to the output differential NMOS transistor pair M3 through the two input resistors _RB Voltage; the drain of the output differential NMOS transistor pair M3 is connected to the power supply voltage VDD, the common source of the two output differential NMOS transistor pairs M3 is the output terminal, and its source is connected to one end of the output resistor _RD , and the output resistor _RD the other end is grounded.

In the present invention, by adjusting the bias voltage of the envelope detector 104, the receiving range of its receiver can be dynamically adjusted.

Preferably, in the present invention, the DC blocking capacitor _CA is composed of an on-chip metal-insulator-metal capacitor (MIM-cap).

Preferably, in the present invention, the pair of differential NMOS transistors are both MOSFETs, that is, field effect transistors.

The invention can be used in a passive imaging system to image an object by detecting electromagnetic waves radiated by the object. Compared with the traditional passive millimeter-wave imaging system, the high-gain receiver proposed by the present invention can realize ultra-wideband electromagnetic wave energy collection and 100dB gain. By dynamically adjusting the bias voltage of the envelope detector, dynamic Adjust the reception range of its receiver. The invention adopts the gallium arsenide 0.15um process, and realizes passive imaging from 80GHz to 100GHz. The noise figure of the receiver is only 1.5dB, the gain of the receiver is 100dB, and the dynamic range is 60dB. The present invention completely overcomes the problem of bandwidth variation caused by process error and temperature drift.

Description of drawings

Figure 1 is a schematic diagram of a millimeter-wave ultra-wideband passive imaging chip.

Figure 2 is a schematic diagram of an ultra-wideband transformer.

FIG. 3 is a schematic diagram of an equivalent circuit diagram of an ultra-wideband transformer.

Figure 4 is a schematic diagram of a theoretical model of an ultra-wideband transformer.

Detailed ways

The invented high-gain receiver applied to millimeter-wave passive imaging will be further described below with reference to the accompanying drawings. In the various figures, like elements are designated by like reference numerals. For the sake of clarity, various parts in the figures have not been drawn to scale. Furthermore, well-known parts may not be shown in the figures.

Numerous specific details of the present invention are described hereinafter in order to provide a clearer understanding of the present invention. However, as can be understood by one skilled in the art, the present invention may be practiced without these specific details.

FIG. 1 shows a schematic diagram of a millimeter-wave ultra-wideband passive imaging chip according to the prior art.

As shown in FIG. 1 , the existing millimeter-wave ultra-wideband passive imaging chip 100 includes an input matching network 101 , an ultra-wideband transformer matching network 102 , and an envelope detector 104 , and the ultra-wideband transformer matching network includes a differential NMOS transistor pair 103 . The input matching network 101 includes four on-chip passive inductors, the middle tap of the output inductor at the right end is connected to the bias voltage _VB , and the upper and lower ends are respectively connected to the gates of the two input NMOS transistors of the UWB transformer matching network. The UWB transformer matching network 102 consists of two differential NMOS transistors and four on-chip passive inductors. The outputs of the two input NMOS transistors, that is, the drains, are connected to the input terminals of the two left inductors, the sources of the NMOS transistors are grounded, and the gates of the NMOS transistor pairs are connected to the upper and lower ends of the two input inductors respectively; the middle tap of the right inductor is connected to The power supply voltage VDD is connected. These two output inductances are in turn coupled to the input or gate of the next stage differential transistor through the inductance biased at voltage _VB . The signal is coupled to the input of the envelope detector through a four-stage ultra-wideband transformer. The envelope detector 104 includes two NMOS transistors M3 (differential transistor pairs), two input resistors R _B , one output resistor R _D and two DC blocking capacitors C _A . The double-ended input is connected to two DC blocking capacitors C _A . _The other ends of the two DC blocking capacitors CA are respectively connected to the gates of the NMOS differential transistor pair M3. At the same time, the bias voltage _VB provides a bias voltage to the NMOS differential transistor pair M3 through the two input resistors _RB . The drain of M3 is connected to the power supply voltage VDD, the common source of the two NMOS transistors is the output terminal, and outputs a voltage signal, the source is connected to the resistor _RD , and the other end of the resistor _RD is grounded.

Figure 2 shows a schematic diagram of an ultra-wideband transformer.

As shown in FIG. 2 , the transformer 200 is composed of three OI layers and two switches. Among them, the two ends of the innermost coil are connected to the switch Switch 2 through the EA layer; the two ends of the middle coil are connected to the P1 and P2 ports through the EA layer, and the middle tap of the middle coil is connected to the power supply voltage VDD; the outermost layer Both ends of the coil are connected to the switch Switch1. The thickness of the three OI layers is 3.3um, the inner diameter of the innermost coil is 12um, the inner diameter of the middle coil is 22um, and the inner diameter of the outermost coil is 32um. The thickness of the EA layer is 0.9um. By changing the states of switches Switch1 and Switch2, the equivalent inductance value L _eq of the transformer seen from ports P1 and P2 can be changed. State 1 of the switch means closed, state 0 means open. When the state of Switch (1,2) is 00, the value of the equivalent inductance L _eq is 91pH; when the state of Switch (1,2) is 10, the value of the equivalent inductance L _eq is 79pH; ,2) when the state is 01, the value of the equivalent inductance L _eq is 65pH; when the state of Switch (1,2) is 11, the value of the equivalent inductance L _eq is 47pH.

FIG. 3 shows a schematic diagram of an equivalent circuit diagram of an ultra-wideband transformer.

As shown in Figure 3, the equivalent circuit diagram of an UWB transformer includes inductors, capacitors, variable capacitors, resistors, and transformers. The two inductors L _s are connected to the left plates of the two capacitors C _s , and the two ends of the resistors are respectively connected to the right plates of the two capacitors C _s . A capacitor of value C _p /2 is connected across the resistor in parallel with the variable capacitor C _var . The variable capacitor C _var is used for fine tuning, and increasing the value of the inductance L _s can increase the fine tuning range of the variable capacitor. The back-end load inductance transformer is used to select the passband. The two switches connected to the inductor correspond to the switches Switch1 and Switch2 in Figure 2, respectively.

Figure 4 shows a schematic diagram of a theoretical model of an ultra-wideband transformer.

As shown in Figure ₄ , the NMOS transistor is used as a switch, the gate of the NMOS transistor is connected to the control signal, the source is grounded, and the drain is connected to the upper end of the inductor L2. When the control signal is 0, the NMOS switch is turned off; when the control signal is 1, the NMOS switch is turned on. The equivalent inductance L _eq is viewed from the left end of the inductance L ₁ , the lower end of the inductance L ₁ is grounded, the lower end of the inductance L ₂ is grounded, and the turns ratio of the inductances L ₁ and L ₂ is k. When the switch is turned on, the NMOS transistor is equivalent to a resistor R _on . At this time, the theoretical model of the UWB transformer includes three resistors and three inductors. _The right end of the resistor R1 is connected to the left end of the inductor L1 _- M, and the common end of the inductor L1 _- M and the inductor L2 _- M is connected to the inductor M. One end, the lower end of the inductor M is connected to the ground, the right end of the inductors L ₂ -M is connected to R ₂ , and the other end of the resistor R ₂ is connected to the equivalent resistor R _on that turns on the NMOS transistor. When the switch is turned off, the NMOS transistor is equivalent to a capacitor Coff. At this time, the theoretical model of the ultra-wideband transformer includes two resistors, three inductors and _one capacitor. The right end of the resistor R1 is connected to the left end of the inductor L1 _- M, and the common terminal of the inductor L1 _- M and the inductor L2 _- M is connected. One end of the inductor M, the lower end of the inductor M is connected to the ground, the right end of the inductors L ₂ -M is connected to the resistor R ₂ , and the other end of the resistor R ₂ is connected to the equivalent capacitor C _off that turns off the NMOS transistor.

As used herein, the terms "comprising", "comprising" or any other variation thereof are intended to encompass a non-exclusive inclusion such that a recited list of elements (such as a process, method, article or device) includes not only those elements, Other elements not explicitly listed are also included. Without further limitation, an element qualified by the phrase "comprises a..." does not preclude the presence of additional identical elements in addition to the inclusion of said element.

In the present invention, the embodiments do not describe all the details in detail, nor do they limit the invention to only the specific embodiments described. Numerous variations are possible in light of the above description. This specification selects and specifically describes these embodiments in order to better explain the principle and practical application of the present invention, so that those skilled in the art can make good use of the present invention and modifications based on the present invention. The present invention is to be limited only by the claims and their full scope and equivalents.

Claims (4)

1. A high-gain receiver applied to millimeter wave passive imaging is characterized in that a circuit structure comprises the following modules: an input matching network 101, an ultra-wideband transformer matching network 102, an envelope detector 104, the ultra-wideband transformer matching network 102 having a differential NMOS transistor pair 103, wherein:

the above-mentionedAn input matching network 101 including four on-chip passive inductors, a center tap of a right-end output inductor, and a bias voltage V_BThe two differential NMOS transistor pairs are connected, and the upper end and the lower end of the two differential NMOS transistor pairs are respectively connected with the grid electrodes of the ultra-wideband transformer matching network 102;

a four-stage transformer is arranged in the ultra-wideband transformer matching network 102; each stage of transformer consists of a differential NMOS transistor pair and four on-chip passive inductors; the four on-chip passive inductors are respectively provided with two output inductors and two input inductors; the output ends (namely drain electrodes) of the two differential NMOS transistor pairs are connected with the upper end and the lower end of the two output inductors, the source electrodes of the differential NMOS transistor pairs are grounded, and the grid electrodes of the differential NMOS transistor pairs are respectively connected with the upper end and the lower end of the two input inductors; the middle taps of the two output inductors are connected with a power supply voltage VDD; the two output inductors pass through a bias voltage V_BIs coupled to the input of the next stage differential NMOS transistor pair; the signal is coupled to the input of the envelope detector 104 via a four-stage transformer;

the envelope detector 104 comprises two output differential NMOS transistor pairs M3, two input resistors R_BAn output resistor R_DAnd two blocking capacitors C_A(ii) a Two input inductors are connected with two DC blocking capacitors C_AOne end of (1), two DC blocking capacitors C_ARespectively connected to the gates of the output differential NMOS transistor pair M3, while a bias voltage V is applied_BThrough two input resistors R_BProviding a bias voltage to the output differential NMOS transistor pair M3; the drains of the output differential NMOS transistor pair M3 are connected to the power supply voltage VDD, the common source of the two output differential NMOS transistor pairs M3 is the output terminal, and the source thereof is connected to the output resistor R_DIs connected to an output resistor R_DAnd the other end of the same is grounded.

2. The high-gain receiver applied to millimeter wave passive imaging according to claim 1, wherein the blocking capacitor C is_AIs composed of an on-chip metal-insulator-metal capacitor.

3. The high-gain receiver applied to millimeter wave passive imaging according to claim 1, wherein the differential NMOS transistor pair is a MOSFET (field effect transistor).

4. The high gain receiver applied to millimeter wave passive imaging according to claim 1, wherein the receiving range of the receiver is dynamically adjusted by adjusting a bias voltage of the envelope detector 104.

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