Millimeter wave phase shifter of quadrature coupler

Abstract

The embodiment of the invention provides a millimeter wave phase shifter of a quadrature coupler, and the phase shifter comprises an input balun which is used for receiving a single-ended signal, converting the single-ended signal into an input differential signal, and transmitting the input differential signal to a quadrature signal generator; the orthogonal signal generator is used for generating an orthogonal signal based on the input differential signal and sending the orthogonal signal to the variable gain amplifier through the transformer; the transformer is connected with the orthogonal signal generator and the variable gain amplifier and is used for carrying out interstage matching on the orthogonal signal generator and the variable gain amplifier; the variable gain amplifier is used for performing gain control based on the orthogonal signals and synthesizing the orthogonal signals into output differential signals; and the output balun is used for converting the output differential signal into a single-ended signal and outputting the single-ended signal.

Description

Technical Field

[0001] This document relates to the field of millimeter wave integrated circuit phased array technology, and in particular to a millimeter wave phase shifter of an orthogonal coupler. Background Art

[0002] With the rapid development of 5G technology, higher requirements are placed on the spectrum utilization and signal processing accuracy of communication systems. With the development and progress of science and technology, the millimeter wave band (30GHz to 300GHz) has attracted widespread attention due to its rich spectrum resources, and wireless communication and sensor technology in the millimeter wave band have gradually become a hot spot for technological development. Although the millimeter wave band has significant advantages in fields such as high-speed communication, it also faces considerable challenges. For example, millimeter wave signals will face large losses and serious attenuation and electromagnetic interference during transmission. In order to solve the problems existing in the millimeter wave band, phased array technology is currently used for improvement. As the core module of the millimeter wave phased array system, the phase control accuracy of the phase shifter directly affects the overall performance of the phased array system. This technological breakthrough enables the millimeter wave phase shifter to better meet the needs of high precision and high flexibility. Researching and developing millimeter wave phase shifters with externally adjustable orthogonal signals can not only improve the overall performance of the phased array system, but also promote the innovative application of related technologies.

[0003] Current phase shifters can be mainly divided into passive phase shifters and active phase shifters based on whether they are active or passive. Passive phase shifters are further divided into transmission line type, reflection type, switch type, and passive vector modulation type; active phase shifters include vector modulation type. Compared with passive phase shifters with narrow bandwidth and poor phase resolution, active vector modulation phase shifters have certain power consumption, but can provide higher phase control accuracy and larger bandwidth. The existing active vector modulation phase shifters use an orthogonal signal generator to generate orthogonal I and Q signals, and then use an amplitude modulation module to perform gain modulation and phase shift control. The operating frequency range of the phase shifter is determined by the orthogonal signal generator. The orthogonal generator uses an RC-CR network, an LC resonant orthogonal network, a high- and low-pass filter network structure, a branch line coupler, and a hybrid orthogonal coupler. The operating frequency range, the phase and amplitude of the generated orthogonal signal of these structures are fixed, and cannot be changed after design and tape-out. Therefore, there is an urgent need for a phase shifter whose operating frequency can be adjusted by an external voltage. The capacitance value of the coupling capacitor between the inductors in the orthogonal coupler can change the coupling capacitor between the inductors in the orthogonal coupler, so that the phase shifter can work in different frequency bands and realize multi-band operation. Moreover, the phase shifter can fine-tune the phase and amplitude of the orthogonal signal generator after the entire design is completed or the chip is taped out, making the phase shift effect more accurate. Summary of the invention

[0004] The object of the present invention is to provide a millimeter wave phase shifter of an orthogonal coupler, aiming to solve the above-mentioned problems in the prior art.

[0005] The present invention provides a millimeter wave phase shifter of an orthogonal coupler, comprising:

[0006] An input balun, for receiving a single-ended signal, converting the single-ended signal into an input differential signal, and sending the input differential signal to an orthogonal signal generator;

[0007] an orthogonal signal generator, configured to generate an orthogonal signal based on the input differential signal and send the orthogonal signal to the variable gain amplifier through the transformer;

[0008] A transformer, connecting the orthogonal signal generator and the variable gain amplifier, for performing inter-stage matching between the orthogonal signal generator and the variable gain amplifier;

[0009] A variable gain amplifier, configured to perform gain control based on the orthogonal signals and synthesize the orthogonal signals into an output differential signal;

[0010] The output balun is used to convert the output differential signal into a single-ended signal and output it.

[0011] The millimeter-wave phase shifter with an externally calibrated orthogonal coupler of the embodiment of the present invention can be applied to the 5G RF millimeter-wave phased array system. By applying voltage externally, the operating frequency range of the orthogonal coupler and the phase and amplitude of the orthogonal signal can be adjusted, and the operating frequency and root mean square (RMS) phase and gain error of the phase shifter can be effectively changed, thereby realizing the switching of the operating frequency, the phase synthesis of multiple frequency bands, and the precise control of the millimeter-wave signal. This flexibility enables the phase shifter to adapt to the requirements of various frequency bands in the 5G system, especially the millimeter-wave band, increases the adjustable parameters, and realizes multi-band millimeter-wave communication. The phase shifter can work in a wider range of application scenarios. In addition, the ability to fine-tune and calibrate the phase shifter after tape-out makes the final system performance more accurate and reliable, which can effectively improve the transmission quality and signal stability of 5G communication. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate one or more embodiments of this specification or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this specification. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0013] Figure 1is a schematic diagram of a millimeter wave phase shifter of an orthogonal coupler according to an embodiment of the present invention;

[0014] Figure 2 is a schematic diagram of a hybrid orthogonal coupler according to an embodiment of the present invention;

[0015] Figure 3 is a schematic diagram of a MOS varactor according to an embodiment of the present invention;

[0016] Figure 4 is a schematic diagram of a variable gain amplifier according to an embodiment of the present invention;

[0017] Figure 5 is a detailed structural schematic diagram of a millimeter wave phase shifter of a cross-coupler according to an embodiment of the present invention;

[0018] Figure 6 is a schematic diagram of a DAC structure according to an embodiment of the present invention;

[0019] Figure 7 It is a schematic diagram of the working frequency switching / calibration principle of the single-ended orthogonal coupler according to an embodiment of the present invention. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to better understand the technical solutions in one or more embodiments of this specification, the following will be combined with the drawings in one or more embodiments of this specification to clearly and completely describe the technical solutions in one or more embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of this specification, not all of the embodiments. Based on one or more embodiments of this specification, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this document.

[0021] According to an embodiment of the present invention, a millimeter wave phase shifter of an orthogonal coupler is provided. Figure 1 Schematic diagram of a millimeter wave phase shifter of an orthogonal coupler according to an embodiment of the present invention. Figure 1 As shown, the millimeter wave phase shifter of the orthogonal coupler according to the embodiment of the present invention specifically includes:

[0022] The input balun 10 is used to receive a single-ended signal, convert the single-ended signal into an input differential signal, and send the input differential signal to the orthogonal signal generator; the input balun 10 is implemented based on a transformer; the input balun 10 specifically includes: a single-ended input end, used to receive a single-ended signal; a differential output end, used to convert the input single-ended signal into an input differential signal and complete impedance matching;

[0023] The orthogonal signal generator 12 is used to generate an orthogonal signal based on the input differential signal and send the orthogonal signal to the variable gain amplifier through the transformer; the orthogonal signal generator 12 is a hybrid orthogonal coupler that can be externally calibrated.

[0024] The externally calibrated hybrid orthogonal coupler is a vertically coupled transformer structure. Four adjustable capacitors Cv1-Cv4 are respectively arranged at the positions where the interlayer coupling capacitors of the externally calibrated hybrid orthogonal coupler are located. A switch is respectively arranged at the voltage bias of each adjustable capacitor. The switch is used to control the access of the corresponding adjustable capacitor Cv1-Cv4, and is connected to the control voltage through the switch, and the capacitance of the adjustable capacitor Cv1-Cv4 is changed by the control voltage.

[0025] The adjustable capacitors Cv1-Cv4 use MOS varactor, wherein the MOS varactor is a varactor diode based on MOS structure, and the capacitance value is adjusted by changing the gate voltage. It is widely used in radio frequency circuits, tuned amplifiers and frequency modulation circuits, and has the advantages of wide tuning range and low power consumption; the size of the MOS varactor is controlled by the voltage VGB between the gate and the substrate. According to the difference of VGB, the MOS varactor works in different areas, and the substrate of the MOS varactor is disconnected from other poles and directly connected to the lowest potential in the circuit.

[0026] The orthogonal signal generator 12 is specifically used for: receiving the output differential signal of the input balun, controlling the on / off of the MOS varactor through an external switch on the MOS varactor gate, controlling the capacitance of the varactor through voltages Vg1-Vg4, and generating two differential orthogonal signals I± and Q± through an orthogonal coupler from the input differential signal, which are sent to the variable gain amplifier through transformers respectively.

[0027] A transformer 14, connected to the orthogonal signal generator and the variable gain amplifier, for performing inter-stage matching between the orthogonal signal generator and the variable gain amplifier;

[0028] The variable gain amplifier 16 is used to perform gain control based on the orthogonal signal and synthesize the orthogonal signal into an output differential signal; the variable gain amplifier 16 includes multiple sets of current steering structures and uses an external DAC for gain control, wherein a set of current steering structures includes: transductors M1-M4 for gain amplification and synthesis, constant current source tubes M5-M6 for gain control, and M1-M6 constitute a Gilbert unit structure.

[0029] The transformer 14 supplies power to the gate of the transconductor of the variable gain amplifier 16 through a tap; and the output balun 18 supplies power to the drain of the transconductor of the variable gain amplifier 16 through a tap.

[0030] The variable gain amplifier 16 is specifically used for:

[0031] The orthogonal signal sent by the orthogonal signal generator is received through the gate of the variable gain amplifier's transconductor, and the gain is amplified and synthesized through the transconductor. The DAC outputs the current value under different phase shift working states and copies it to the constant current source tube of the variable gain amplifier to change the output gain and realize gain control and synthesis. The DAC adopts a current steering structure.

[0032] The output balun 18 is used to convert the output differential signal into a single-ended signal and output it. The output balun 18 is implemented based on a transformer; the output balun 18 specifically includes: a differential input end, used to receive the output differential signal, convert the output differential signal into a single-ended signal, and complete impedance matching; a single-ended output end, used to output a single-ended signal.

[0033] The above technical solution of the embodiment of the present invention is described in detail below in conjunction with the accompanying drawings.

[0034] like Figure 1 As shown, the embodiment of the present invention proposes a vector modulation millimeter wave phase shifter with an externally calibrated orthogonal coupler, which specifically includes: an input balun, which is responsible for converting a single-ended signal into a differential signal; an orthogonal signal generator (I / Q Generator) adopts an externally calibrated hybrid orthogonal coupler, which is responsible for generating orthogonal signals; a variable gain amplifier (VGA) adopts a current steering structure for gain control and signal synthesis, and the VGA adopts an external DAC for gain control; a transformer is used for matching between the orthogonal signal generator and the variable gain amplifier; an output balun is responsible for converting a differential signal into a single-ended signal for subsequent measurement. The input matching Balun is implemented based on a transformer, has a single-ended input end, and has a differential output end, which is used to convert the input single-ended signal into a differential signal and complete impedance matching.

[0035] The principle of hybrid orthogonal coupler used in the orthogonal signal generator is as follows: Figure 2 . The orthogonal coupler adopts a vertically coupled transformer structure. Cv1-4 is an adjustable capacitor. Here, a varactor is used. In addition, there are interlayer coupling capacitors between IN and CPL, THRU and ISO ports (not marked on the figure). IN+ and IN- are differential signal input terminals, THU+ and THU- are pass-through terminals, CPL+ and CPL- are coupling terminals, ISO+ and ISO- are isolation terminals, and are connected to 100 ohm resistors. Within the operating frequency range, the output signals of the THU and CPL ports differ in phase by 90° and are balanced in amplitude.

[0036] Through the analysis of the coupler, it can be known that the interlayer coupling capacitance of the orthogonal coupler is related to the frequency and port impedance of the coupler. The port impedance setting does not change. By changing the adjustable capacitors Cv1-4, the interlayer coupling capacitance of the orthogonal coupler can be changed, thereby changing the working frequency of the coupler. By changing Cv1-4 respectively, the phase or amplitude of the orthogonal signal generated by the coupler can also be calibrated or fine-tuned. In the present invention, the adjustable capacitor is added to the interlayer coupling capacitor position of the orthogonal coupler, and a switch is added to the voltage bias of each adjustable capacitor. The switch controls the access of the adjustable capacitor Cv1-4, and the wire is pulled to the outside. The control voltage can change the capacitance of the adjustable capacitor. The adjustable capacitor can use a varactor. The capacitance range of a single varactor that can be changed at high frequency is very small. Therefore, a plurality of varactor series arrays or the number of varactor grids can be modified to expand the capacitance range.

[0037] like Figure 3 As shown in the figure, MOS varactor is a variable capacitance diode based on MOS structure, which adjusts the capacitance value by changing the gate voltage. It is widely used in RF circuits, tuned amplifiers and frequency modulation circuits, and has the advantages of wide tuning range and low power consumption; the size of the capacitance is controlled by the voltage VGB between the gate and the substrate. Cv is used as Figure 3 The structure shown is an array of varactors.

[0038] Depending on the VGB, the MOS tube works in different areas. When |VGB|>|VT|, an inversion carrier channel is formed and it works in the strong inversion area. In order to obtain the monotonous change characteristic of CMOS when VG changes in a large range, the substrate of the MOS tube can be disconnected from other poles and directly connected to the lowest potential in the circuit.

[0039] like Figure 4 As shown, the variable gain amplifier adopts a current steering structure. In the millimeter wave frequency band, a complex circuit structure will have many parasitics, affecting the circuit performance. This structure is simple, with a small additional phase shift and good linearity. The structure is as follows, where transistors M1-M4 are transconductors responsible for gain amplification, and M5-M6 are constant current source tubes responsible for gain control.

[0040] The entire circuit diagram is as follows Figure 5As shown, the single-ended signal is converted into a differential signal through the input balun and enters the orthogonal coupler which can be externally calibrated. The external switch on the gate of the varactor controls the opening / closing of the varactor. The capacitance of the varactor is controlled by the voltage Vg1-Vg4. The signal generates two differential orthogonal signals I± and Q± through the orthogonal coupler, which enter the gate input of the variable gain amplifier transconductance stage M1-M8 through the transformer respectively. The output of the orthogonal signal generator and the input of the variable gain amplifier are matched with impedance by a transformer. The gate of the variable gain amplifier transconductor M1-M8 is powered by the transformer tap. The output of the variable gain amplifier adopts a balun to directly realize the function of converting the differential signal to a single-ended signal, and the balun tap is used to power the drain of the transconductor M1-M8. The constant current source tubes are M9-M12. The DAC outputs the current value under different phase shift working states, which is copied to the constant current source tubes M9-M12 through tubes M13-M16, thereby changing the output gain and realizing gain control and synthesis.

[0041] DAC uses a current steering structure such as Figure 6 As shown, where N is the number of phase shifter bits.

[0042] The millimeter wave phase shifter with an externally calibrated orthogonal coupler of the embodiment of the present invention can be applied to a radio frequency millimeter wave phased array system. By adjusting the phase and amplitude of the orthogonal signal of the orthogonal coupler through external voltage application, the operating frequency and RMS phase / gain error of the phase shifter can be adjusted, and the phase shifter can be operated in different frequency bands to achieve multi-band millimeter wave communication. The additional adjustable quantity is also conducive to fine-tuning and calibrating the phase shifter after tape-out, making the result more accurate. The architecture adopted by the phase shifter is an active vector modulation phase shifter, and its main architecture includes: an input balun, an externally calibrated orthogonal coupler, a variable gain amplifier, and an output balun.

[0043] Finally, combine Figure 7 , taking a single-ended orthogonal coupler as an example, the principle of operating frequency switching / calibration of the orthogonal coupler is explained.

[0044] like Figure 7 As shown, the input port is port 1, the through port is port 2, the coupled port is port 3, the isolated port is port 4, and k is the coupling coefficient. According to the symmetry line P1, P2 can be divided into four parts, which are four modes. The port input impedance is even-even mode (P1, P2 open circuit), even-odd mode (P1 open circuit, P2 short circuit), odd-even mode (P1 short circuit, P2 open circuit) and odd-odd mode (P1, P2 short circuit). The reflection coefficients of the four modes (Γ ee ,Γ eo ,Γ oe ,Γ oo ) The S parameters of each port of the coupler are calculated as follows:

[0045]

[0046] The scattering matrix of an ideal hybrid coupler is:

[0047]

[0048] Substituting it into the scattering matrix of the ideal hybrid coupler, we can calculate:

[0049]

[0050] It can be seen that the coupling capacitor C m The size will affect the operating frequency ω0 of the coupler and change the coupling capacitor C m The operating frequency of the coupler can be changed. The operating frequency and characteristic impedance of the phase shifter can also be fine-tuned in this way.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A millimeter wave phase shifter of an orthogonal coupler, characterized in that: include: An input balun, for receiving a single-ended signal, converting the single-ended signal into an input differential signal, and sending the input differential signal to an orthogonal signal generator; an orthogonal signal generator, configured to generate an orthogonal signal based on the input differential signal and send the orthogonal signal to the variable gain amplifier through the transformer; A transformer, connecting the orthogonal signal generator and the variable gain amplifier, for performing inter-stage matching between the orthogonal signal generator and the variable gain amplifier; A variable gain amplifier, configured to perform gain control based on the orthogonal signals and synthesize the orthogonal signals into an output differential signal; The output balun is used to convert the output differential signal into a single-ended signal and output it.

2. The millimeter wave phase shifter of the orthogonal coupler according to claim 1, characterized in that: The input balun and the output balun are implemented based on transformers; The input balun specifically includes: A single-ended input terminal, used for receiving a single-ended signal; The differential output terminal is used to convert the input single-ended signal into an input differential signal and complete impedance matching; The output balun specifically includes: A differential input terminal, used for receiving an output differential signal, converting the output differential signal into a single-ended signal, and completing impedance matching; Single-ended output terminal, used to output single-ended signal.

3. The millimeter wave phase shifter of the orthogonal coupler according to claim 1, characterized in that: The orthogonal signal generator is a hybrid orthogonal coupler which can be externally calibrated.

4. The millimeter wave phase shifter of the orthogonal coupler according to claim 3, characterized in that: The externally calibrated hybrid orthogonal coupler is a vertically coupled transformer structure. Four adjustable capacitors Cv1-Cv4 are respectively arranged at the positions where the interlayer coupling capacitors of the externally calibrated hybrid orthogonal coupler are located. A switch is respectively arranged at the voltage bias of each adjustable capacitor. The switch is used to control the access of the corresponding adjustable capacitor Cv1-Cv4, and is connected to the control voltage through the switch, and the capacitance of the adjustable capacitor Cv1-Cv4 is changed by the control voltage.

5. The millimeter wave phase shifter of the orthogonal coupler according to claim 4, characterized in that: The adjustable capacitors Cv1-Cv4 use MOS varactors, wherein the MOS varactor is a varactor diode based on a MOS structure, and the capacitance value is adjusted by changing the gate voltage; the capacitance value of the MOS varactor is controlled by the voltage VGB between the gate and the substrate, and the MOS varactor works in different areas according to the difference in VGB, and the substrate of the MOS varactor is directly connected to the lowest potential in the circuit.

6. The millimeter wave phase shifter of the orthogonal coupler according to claim 5, characterized in that: The orthogonal signal generator is specifically used for: The input differential signal is received, which refers to the differential signal after the single-ended signal is converted through the input balun. The MOS varactor is turned on / off by an external switch on the MOS varactor gate, and the capacitance of the varactor is controlled by the voltage Vg1-Vg4. The input differential signal generates two differential orthogonal signals I± and Q± through an orthogonal coupler, which are sent to the variable gain amplifier through transformers respectively.

7. The millimeter wave phase shifter of the orthogonal coupler according to claim 1, characterized in that: The variable gain amplifier includes multiple sets of current steering structures and uses an external DAC for gain control, wherein one set of current steering structures includes: transconductors M1-M4 for gain amplification and synthesis, constant current source tubes M5-M6 for gain control, and the transconductors M1-M4 and constant current source tubes M5-M6 constitute a Gilbert unit.

8. The millimeter wave phase shifter of the orthogonal coupler according to claim 7, characterized in that: The transformer supplies power to the gate of the transconductor of the variable gain amplifier through a tap; and the output balun supplies power to the drain of the transconductor of the variable gain amplifier through a tap.

9. The millimeter wave phase shifter of the orthogonal coupler according to claim 8, characterized in that: The variable gain amplifier is specifically used for: The orthogonal signal sent by the orthogonal signal generator is received through the gate of the transconductor of the variable gain amplifier, and the gain is amplified and synthesized through the transconductor. The DAC outputs the current value under different phase shift working states and is copied to the constant current source tube of the variable gain amplifier through the current mirror to change the output gain and realize gain control and synthesis.

10. The millimeter wave phase shifter of the orthogonal coupler according to claim 9, characterized in that: The DAC adopts a current steering structure.

Images