A novel silicon-based millimeter-wave differential reflection phase shifter

Abstract

The present invention designs a novel silicon-based millimeter-wave differential reflective phase shifter, which uses two identical 6-bit control bit 90° reflective phase shift modules and one 1-bit control bit 180° phase shift module as basic units, wherein each 90° reflective phase shift module includes a differential 3dB orthogonal coupler and an LC series structure reflective load connected to its through end and coupling end, and the capacitor in the load is composed of a 6-bit digital control switch capacitor array. Changing the digital control signal can change the phase shift state, with a phase shift range of 360° and a phase shift accuracy of 11.25°. The present invention adopts measures such as providing 2-bit redundant bits and adding compensation resistors to enable the phase shifter to achieve higher phase shift accuracy and smaller gain error.

Description

Technical Field

[0001] The present invention belongs to the technical field of millimeter wave integrated circuits, and in particular relates to a silicon-based millimeter wave differential reflection type phase shifter with a novel structure. Background Art

[0002] With the development of wireless communication and integrated circuit technology, millimeter wave communication systems can achieve high data rates to meet the growing demand for massive information transmission. However, the attenuation during millimeter wave transmission leads to a decrease in signal-to-noise ratio. Phased array technology is one of the most effective ways to improve the signal-to-noise ratio of millimeter wave communication systems. Systems that use phased arrays extensively include automotive driving assistance systems, satellite communications, and smart home systems. Phase shifters are key components in phased array systems that control beams by changing the phase of each channel. Phase shifter circuits are widely used in both transmit and receive channels.

[0003] As a phase control circuit, in order to achieve signal phase control, the phase shifter needs to have high phase shift accuracy, wide phase shift range, and small gain error to accurately control the beam. Therefore, the technical indicators of the phase shifter include phase shift range, phase shift accuracy, gain error, power consumption, etc. In general, the development trend of the phase shifter is towards ultra-wideband, low power consumption, small size, and high performance.

[0004] The commonly used phase shifter structures can be divided into passive and active types according to whether there is energy loss. Active phase shifters mainly use vector synthesis structure; passive phase shifters mainly include reflection type structure and switch type structure. The reflection type changes the phase by changing the impedance of the load network, and the switch type changes the phase by controlling the conduction or shutdown of different phase shift units. Among them, the reflection type phase shifter has the advantages of no DC power consumption, high linearity, simple structure, and as the frequency increases, the area of ​​passive devices such as inductors in the circuit is reduced, and the area and cost problems that exist in it are also greatly alleviated.

[0005] The phase shift range of the reflective phase shifter is mainly determined by the tuning range of the reflective load. Existing reflective load structures include capacitive load structure, LC load structure and CLC load structure. Among them, the capacitive load structure has a small area, but a small phase shift range; the LC load structure and the CLC load structure are generally limited by the tuning range of the variable capacitor, which is usually less than 360°. In addition, the reflective phase shifter exhibits narrowband characteristics because its reflective load is a tuning network based on a single frequency point, and it only has good performance at the center frequency point, making it difficult to achieve 360°, broadband, high-precision, and low gain error phase shifting. Summary of the invention

[0006] The present invention aims to provide a silicon-based millimeter-wave differential reflection phase shifter with a novel structure, which can realize a 360°, broadband, high-precision, and low-gain-error phase shifting function.

[0007] In order to solve the above technical problems, the specific technical solutions of the present invention are as follows:

[0008] The present invention discloses a novel silicon-based millimeter-wave differential reflective phase shifter, comprising an input matching circuit, a first 90° reflective phase shifter, a second 90° reflective phase shifter, a 180° phase shifter and an output matching circuit, which are cascaded in sequence, and the four circuits all adopt a differential structure; the phase shifter has a total of 7-bit digital control signals VC1-VC7, and the digital control signals can control the phase shifter to work in different phase shift states, wherein the 6-bit digital control signals VC1-VC6 are used to control the phase shift of the reflective phase shifter circuit, and the 1-bit digital control signal VC7 is used to control the phase shift of the 180° phase shifter circuit.

[0009] Furthermore, the input matching circuit includes a capacitor and an inductor, which are composed of an LC network, with the capacitor in parallel and the inductor in series. The input end of the input matching circuit is connected to the capacitor and the inductor respectively, the other end of the capacitor is grounded, and the other end of the inductor is the output end of the input matching circuit. The input matching circuit is used to match the input standard 50 ohm impedance to the characteristic impedance of the differential 3dB orthogonal coupler.

[0010] Further, the first 90° reflective phase shift circuit and the second 90° reflective phase shift circuit have the same structure and the same digital control signal; the first 90° reflective phase shift circuit includes a first differential 3dB quadrature coupler and a first reflective load network connected thereto; the second 90° reflective phase shift circuit includes a second differential 3dB quadrature coupler and a second reflective load network connected thereto;

[0011] The first differential 3dB orthogonal coupler and the second differential 3dB orthogonal coupler are both transformer-based differential couplers, and both include a through terminal THR±, a coupling terminal COU±, an input terminal IN±, and an isolation terminal OUT±; the first reflective load network and the second reflective load network have the same structure;

[0012] The first differential 3dB orthogonal coupler input terminal IN± and isolation terminal OUT± are respectively connected to the inductance of the input matching circuit and the input terminal IN± of the second 3dB orthogonal coupler, and the isolation terminal OUT± of the second differential 3dB orthogonal coupler is connected to the 180° phase shift circuit.

[0013] Furthermore, the reflective load network includes an inductor and a 6-bit digitally controlled switch capacitor array, the inductor and the digitally controlled switch capacitor array constitute a series resonant network, the digitally controlled switch capacitor array includes 6 parallel units, each unit has the same structure, and includes a capacitor and a MOS switch tube, one end of the capacitor is connected to the inductor, and the other end is connected to the drain of the switch tube M1~M6, and the source of the switch tube M1~M6 is grounded; the capacitor size in each unit structure is different, and the open tube size in each unit structure is different.

[0014] Furthermore, the inductor is connected to the through terminal THR± or the coupling terminal COU± of the differential 3dB orthogonal coupler, and the 6-bit digital control signal is respectively applied to the gates of the 6 MOS tubes to control their on and off;

[0015] Furthermore, the differential 3dB orthogonal coupler is a transformer-based differential coupler, including a through-end THR±, a coupling end COU±, an input end IN± and an isolation end OUT±, which is achieved by coupling the top metal and the second top metal coil width. The length of the coil is mainly determined by the inner diameter and the spacing, and affects the operating frequency of the coupler. The line width determines the coupling coefficient between the two layers of metal. The transformer-based coupler uses inductive and capacitive coupling to establish an orthogonal phase relationship between the through-end THR± and the coupling end COU±. When the frequency increases, the amplitude of the through-end THR± decreases, showing a low-pass response; the amplitude of the coupling end COU± increases, showing a high-pass response. Matching at the center frequency, the through-end THR± and the coupling end COU± have the same amplitude and a phase difference of 90°. The signal is input from the input end IN± of the differential 3dB orthogonal coupler and output from the isolation end OUT±.

[0016] Further, the 180° phase shift circuit includes two pairs of switch tubes, one pair of switch tubes includes switch tubes M7 and M8, and the other pair of switch tubes includes switch tubes M9 and M10; the sources of switch tubes M7 and M8 are connected together, the sources of M9 and M10 are connected together, the drains of M7 and M9 are connected together, and the drains of M8 and M10 are connected together. The gate of each switch tube is connected to a compensation resistor R, and the 1-bit digital control signal VC7 is connected to the gates of switch tubes M7 and M10 respectively through the compensation resistor R. The 1-bit digital control signal VC7 passes through an inverter and then transmits to the series compensation resistor R before being connected to the gates of switch tubes M8 and M9. The source of the switch tube is connected to the isolation terminal OUT± of the second differential 3dB orthogonal coupler, that is, the output terminal of the second 90° reflective phase shift circuit, and the drains of the two pairs of switch tubes are connected to the input terminal of the output matching circuit respectively. The 1-bit digital control signal VC7 cooperates with the inverter to control the switching state of the four transistors. The MOS tube works in the linear region or the cut-off region, and can achieve two phase shift states of 0° and 180°.

[0017] Furthermore, the output matching circuit is a transformer, which is used to match the output impedance of the inverter circuit to a standard 50 ohm impedance at the output end.

[0018] Furthermore, all inductors are implemented using spiral inductors.

[0019] Furthermore, the output matching transformer is implemented by using an octagonal spiral wide-side stacked structure.

[0020] The novel silicon-based millimeter-wave differential reflection phase shifter of the present invention has the following advantages:

[0021] First, the present invention adopts two-stage 90° reflective phase shifting circuits to realize 90° range phase shifting and 180° phase shifting circuits to realize 180° phase shifting, which can ensure that the phase shifter can realize a 360° phase shifting range and has a wider bandwidth performance and higher phase shifting accuracy.

[0022] Second, the present invention adds a compensation resistor to the gate of the MOS switch tube, which can reduce the loss and insertion loss fluctuation.

[0023] Thirdly, the present invention improves the phase shift accuracy by increasing the number of bits of the digitally controlled switch capacitor array and providing redundant phase shift states. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic diagram of the circuit structure of an existing reflective phase shifter;

[0025] Figure 2 It is a schematic diagram of the circuit structure of a novel silicon-based millimeter-wave differential reflection phase shifter of the present invention;

[0026] Figure 3 is a layout of a differential 3dB orthogonal coupler of the present invention;

[0027] Figure 4 It is a schematic diagram of the circuit structure of the LC reflective load of the present invention;

[0028] Figure 5 It is a schematic diagram of the circuit structure of a 180° phase shifter;

[0029] Figure 6 It is a schematic diagram of 32 phase simulation curves after selecting 19.5~23.5GHz phase shifters;

[0030] Figure 7 It is a schematic diagram of the RMS phase error simulation curve of the 19.5-23.5GHz phase shifter;

[0031] Figure 8 It is a schematic diagram of the RMS gain error simulation curve of the 19.5-23.5GHz phase shifter. DETAILED DESCRIPTION

[0032] In order to better understand the purpose, structure and function of the present invention, a novel silicon-based millimeter-wave differential reflection phase shifter of the present invention is further described in detail below in conjunction with the accompanying drawings.

[0033] like Figure 1 The figure is a schematic diagram of the circuit structure of an existing reflective phase shifter. An embodiment of the present invention provides a digitally controlled phase shifter circuit with an operating frequency band of 19.5 to 23.5 GHz. The circuit realizes a 360° phase shift with a phase shift accuracy of 11.25°.

[0034] Figure 2 An overall circuit architecture diagram of a digitally controlled phase shifter provided in an embodiment of the present invention adopts a cascade structure of a two-stage reflective phase shift circuit and a 180° phase shift circuit.

[0035] The reflective phase shift circuit adopted in this embodiment is as follows Figure 2 As shown, after the differential signal passes through the input matching circuit, it enters the first 90° reflective phase shift circuit and is first input into the first differential 3dB quadrature coupler. The through-end THR± and the coupled end COU± of the coupler adopt an LC series load network. The load impedance changes the phase of the reflected signal, thereby realizing the change of the output signal phase. The isolation end OUT± of the differential 3dB quadrature coupler is the differential signal output port; the differential signal then passes through an identical reflective phase shift circuit, the first 90° reflective phase shift circuit, and the two reflective phase shift circuits can respectively realize a phase shift in the range of 90°. After passing through the two reflective phase shift circuits, a phase shift in the range of 180° can be realized.

[0036] The differential 3dB orthogonal coupler adopted in this embodiment is as follows Figure 3 As shown in the figure, the differential 3dB orthogonal coupler is a transformer-based differential coupler. All four ports are differential, which is achieved by coupling the top metal and the second top metal coil width. The length of the coil is mainly determined by the inner diameter and the spacing, and affects the operating frequency of the coupler. The line width determines the coupling coefficient between the two layers of metal. The transformer-based coupler uses inductive and capacitive coupling to establish an orthogonal phase relationship between the through-end THR± and the coupled end COU±. When the frequency increases, the amplitude of the through-end THR± decreases, showing a low-pass response; the amplitude of the coupled end COU± increases, showing a high-pass response. Matching at the center frequency, the through-end THR± and the coupled end COU± have the same amplitude and a phase difference of 90°. The signal is input from the input end IN± of the differential 3dB orthogonal coupler and output from the isolation end OUT±.

[0037] The reflective load circuit adopted in this embodiment is as follows Figure 4As shown, the signal enters from the input end, passes through an inductor L, and then enters the digital control switch capacitor array. The capacitor array consists of 6 units in parallel. Each unit consists of capacitors Ci of different sizes and switch tubes Mi of different sizes. The switch tubes Mi are controlled one by one by the digital control signal VCi, where i = 1, 2, 3...6; when the VCi digital control signal is high, the switch tube Mi is turned on, and the capacitor Ci of the branch where it is located plays a role; when the VCi digital control signal is low, the switch tube Mi is turned off, and the branch where it is located is disconnected. In addition, a high resistance R is added to the gate of each switch tube to reduce loss and reduce the fluctuation of insertion loss.

[0038] The 180° phase shift circuit adopted in this embodiment is as follows Figure 5 As shown, the source electrodes of the switch tubes M7 and M8 are connected together, the source electrodes of M9 and M10 are connected together, the drain electrodes of M7 and M9 are connected together, the drain electrodes of M8 and M10 are connected together, and the gate electrodes of each transistor are connected to a compensation resistor R. M7 and M10, M8 and M9 are differential pairs of tubes, the gate control voltages of M7 and M10 are VC7, and the gate control voltages of M8 and M9 are / VC7. When VC7 is at a high level, M7 and M10 are turned on, the transistors are equivalent to small resistors, and the branch where they are located presents a low resistance state. At this time, / VC7 is at a low level, M8 and M9 are turned off, the transistors are equivalent to large capacitors, and the branch where they are located presents a high resistance state. At this time, after the RF signal flows in from the input port IN+, it will flow through the branch where M7 is located to reach the circuit output terminal OUT+, and after the RF signal flows in from the input port IN-, it will flow through the M10 branch to reach the circuit output terminal OUT-, and the output state is defined as 0°. When VC7 is at a low level, M7 and M10 are cut off, the transistor is equivalent to a large capacitor, and the branch where it is located is in a high-resistance state. At this time, / VC7 is at a high level, M8 and M9 are turned on, the transistor is equivalent to a small resistor, and the branch where it is located is in a low-resistance state. At this time, the RF signal flows from the input port IN+ and then flows through the branch where M8 is located to reach the circuit output terminal OUT+. The RF signal flows from the input port IN- and then flows through the M9 branch to reach the circuit output terminal OUT-. The output state is defined as 180°. In both states, the circuit does not produce a large amount of attenuation to the RF signal, and there is only a small amount of loss. After the differential signal passes through the inverting circuit, it passes through the transformer to complete impedance matching and is finally output.

[0039] To demonstrate the effectiveness of this embodiment, simulation results of the 19.5-23.5 GHz phase shifter are summarized as follows.

[0040] like Figure 6 As shown, it is a schematic diagram of a phase simulation curve of selecting 32 appropriate phase shift states of the phase shifter in the range of 19.5 to 23.5 GHz in this embodiment, covering a phase shift range of 360° with a step of 11.25°.

[0041] like Figure 7As shown, it is a simulation curve of the RMS phase error of the phase shifter of this embodiment. The RMS phase error at the center frequency of 21.5 GHz is 2.67°, and the maximum RMS phase error within 19.5-23.5 GHz is 3.81°.

[0042] like Figure 8 As shown, it is a simulation curve of the RMS gain error of the phase shifter of this embodiment. The RMS gain error at the center frequency of 21.5 GHz is 0.47 dB, and the maximum RMS gain error within 19.5 to 23.5 GHz is 0.63 dB.

[0043] In summary, the novel silicon-based millimeter-wave differential reflection phase shifter of the present invention can have the following technical effects:

[0044] First, the two-stage reflective phase shift circuit and the 180° phase shift circuit cascade structure used in the present invention can ensure that the phase shifter can achieve a 360° phase shift range;

[0045] Second, the present invention adds a compensation resistor to the gate of the MOS switch tube, which can reduce the loss and insertion loss fluctuation.

[0046] Thirdly, the present invention increases the number of bits of the digitally controlled switch capacitor array and can provide redundant phase shift states to improve phase shift accuracy.

[0047] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A novel silicon-based millimeter-wave differential reflection phase shifter, characterized in that: It includes an input matching circuit, a first 90° reflective phase shift circuit, a second 90° reflective phase shift circuit, a 180° phase shift circuit and an output matching circuit, and they are cascaded in sequence, and the input matching circuit, the first 90° reflective phase shift circuit, the second 90° reflective phase shift circuit, and the 180° phase shift circuit all adopt a differential structure; The input matching circuit comprises a capacitor and an inductor, the input end of the input matching circuit is connected to the capacitor and the inductor respectively, the other end of the capacitor is grounded, and the other end of the inductor is the output end of the input matching circuit; The first 90° reflection type phase shift circuit and the second 90° reflection type phase shift circuit have the same structure and the same digital control signal; the first 90° reflection type phase shift circuit includes a first differential 3dB orthogonal coupler and a first reflection load network connected thereto; the second 90° reflection type phase shift circuit includes a second differential 3dB orthogonal coupler and a second reflection load network connected thereto; The first differential 3dB orthogonal coupler and the second differential 3dB orthogonal coupler are both transformer-based differential couplers, and both include a through terminal THR±, a coupling terminal COU±, an input terminal IN±, and an isolation terminal OUT±; The first differential 3dB orthogonal coupler input terminal IN± and the isolation terminal OUT± are respectively connected to the inductance of the input matching circuit and the input terminal IN± of the second 3dB orthogonal coupler, and the isolation terminal OUT± of the second differential 3dB orthogonal coupler is connected to the 180° phase shift circuit; The 180° phase shift circuit includes two pairs of switch tubes, one pair of switch tubes includes switch tubes M7 and M8, and the other pair of switch tubes includes switch tubes M9 and M10; the source electrodes of the switch tubes M7 and M8 are connected together, the source electrodes of M9 and M10 are connected together, the drain electrodes of M7 and M9 are connected together, and the drain electrodes of M8 and M10 are connected together, and the gate electrode of each switch tube is connected to a compensation resistor R, and a 1-bit digital control signal is connected to the gate electrodes of the switch tubes M7 and M10 respectively through the compensation resistor R, and the 1-bit digital control signal is inverted and connected to the gate electrodes of the switch tubes M8 and M9 through the compensation resistor R; the source electrode of the switch tube is connected to the isolation terminal OUT± of the second differential 3dB orthogonal coupler, that is, the output terminal of the second 90° reflective phase shift circuit, and the drain electrodes of the two pairs of switch tubes are respectively connected to the input terminal of the output matching circuit; The output matching circuit is a transformer used to match the output impedance of the inverter circuit to the standard 50 ohm impedance of the output terminal.

2. A novel silicon-based millimeter-wave differential reflection phase shifter according to claim 1, characterized in that: The reflective load network includes an inductor and a 6-bit digitally controlled switch capacitor array, which form a series resonant network. The digitally controlled switch capacitor array includes six units connected in parallel, each unit has the same structure, including a capacitor and a MOS switch tube, one end of the capacitor is connected to the inductor, and the other end of the capacitor is connected to the drain of the switch tube M1 to M6, and the source of the switch tube M1 to M6 is grounded; the size of the capacitor in each unit structure is different from each other, and the size of the open tube in each unit structure is different from each other; The inductor is connected to the through terminal THR± or the coupling terminal COU± of the differential 3dB coupler, and the 6-bit digital control signal is respectively added to the gates of the six MOS switch tubes to control their conduction and shutdown.

3. A novel silicon-based millimeter-wave differential reflection phase shifter according to claim 1, characterized in that: The differential 3dB orthogonal coupler is realized by coupling the wide sides of the top metal and the second top metal coils; the length of the coil is mainly determined by the inner diameter and the spacing, and affects the operating frequency of the coupler, and the line width determines the coupling coefficient between the two layers of metal; the transformer-based coupler uses inductive and capacitive coupling to establish an orthogonal phase relationship between the through-end THR± and the coupled end COU±; when the frequency increases, the amplitude of the through-end THR± decreases, showing a low-pass response; the amplitude of the coupled end COU± increases, showing a high-pass response; matching at the center frequency, the through-end THR± and the coupled end COU± have the same amplitude and a phase difference of 90°; the signal is input from the input end IN± of the differential 3dB orthogonal coupler and output from the isolation end OUT±.

4. A novel silicon-based millimeter-wave differential reflection phase shifter according to claim 1, characterized in that: The transformer is realized by using an octagonal spiral wide-side laminated structure.

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