A series resonant voltage controlled oscillator with mode switching function

Abstract

The application discloses a series resonant voltage-controlled oscillator with mode switching function, comprising a series resonant mode switching switch and two coupled series resonant oscillator units, the series resonant oscillator unit comprising an active negative resistance network and an LC resonant network, the LC resonant network comprising a first inductor, a first capacitor and a second inductor connected in series, the first inductor and the second inductor being connected with two output terminals of the active negative resistance network in one-to-one correspondence. A first node is arranged on a line between the first inductor and the active negative resistance network, and a second node is arranged on a line between the second inductor and the active negative resistance network, and the series resonant mode switching switch is used for controlling mode switching of even mode and odd mode. When the application is applied, the reliability of mode switching can be ensured, meanwhile, the parasitic capacitance of the mode switching switch cannot introduce a series resonant cavity, thereby the tuning range cannot be compressed, and the frequency tuning range of the series resonant oscillator can be widened.

Description

Technical Field

[0001] The present invention relates to integrated circuit design technology, in particular to a series resonant voltage-controlled oscillator with a mode switching function. Background Art

[0002] An oscillator is a device that converts DC power supply energy into an AC signal of a specific frequency. It does not require external signal excitation when used. The oscillator itself has positive feedback and a certain gain to overcome the loss in the circuit feedback path, so it can generate a self-sustaining and stable output oscillation signal. As one of the main categories of oscillators, the voltage-controlled oscillator is used in modules such as phase-locked loops and clock recovery circuits. It is one of the core modules of wireless communication systems. Types of voltage-controlled oscillators include LC voltage-controlled oscillators, RC voltage-controlled oscillators, and crystal voltage-controlled oscillators. The schematic diagram of the LC voltage-controlled oscillator is shown in the figure below. Figure 1 As shown in the figure, it is divided into an active negative resistance network and an LC resonant network. The inductor and capacitor in the LC resonant network have two resonance forms: parallel and series. Figure 2 As shown, in order to maintain the constant amplitude oscillation of the LC resonant network, an active negative resistance network must be introduced to compensate for the energy loss in the LC resonant network, thereby achieving the stability of the oscillation amplitude.

[0003] Phase noise is a critical oscillator specification. Due to the influence of noise in actual circuits, the phase of the oscillator's output signal will experience random jitter. In the frequency domain, this impact is the generation of sidebands on both sides of a single frequency spectrum, increasing the effective signal bandwidth and generating phase noise. For voltage-controlled oscillators, currently, extremely low phase noise can only be achieved by exponentially increasing the oscillator's signal power.

[0004] The most commonly used LC voltage-controlled oscillators are the mode switching oscillator based on parallel resonance and the series resonance oscillator. The schematic diagram of the mode switching oscillator based on parallel resonance is shown in FIG. Figure 3 As shown. Two LC parallel resonant oscillators are coupled together in an inductive or capacitive manner ( Figure 3 (a) is capacitive coupling, Figure 3 (b) is inductive coupling), the nodes N1 and N2, and the nodes N3 and N4 are in anti-phase; the phases between the nodes N1 and N3, and the nodes N2 and N4 are switched to the same or anti-phase odd-even mode by the mode switching circuit. Figure 3 (a) Different equivalent capacitances can be obtained by mode switching. Figure 3(b) Different equivalent inductances can be obtained by mode switching, and then the resonant frequency can be selected. The mode switching circuit has the following advantages: (1) In any mode, the switch in the mode switching circuit only affects the unwanted resonant frequency, and does not affect the quality factor of the resonator in the selected mode; (2) The mode switching circuit can be expanded, and 2 N oscillators are coupled together through N capacitors with different capacities, and then the odd and even modes are switched, and in the ideal case, a total of 2 N modes can be generated; (3) The mode switching technology based on parallel resonance can simultaneously realize wide tuning range and low phase noise. However, the use of 2 N oscillators in parallel can reduce the phase noise by 10Nlog 10 2dB, and multiple oscillators must be connected in parallel to obtain extremely low phase noise, which occupies a large chip area and limits the number of cores that can be integrated. At the same time, the mode switching switch circuit is located between the capacitor side nodes N 1，2，3，4 , and the parasitic capacitance of the switching switch is introduced into the resonant cavity, which compresses the frequency tuning range.

[0005] The schematic diagram of the series resonant oscillator is shown in Figure 4 , and compared with the schematic diagram of the parallel resonant oscillator shown in Figure 5 , the inductor and the capacitor in the series resonant oscillator are connected in series, unlike the traditional oscillator in which the inductor and the capacitor are connected in parallel. At the same time, under the same power voltage, the signal power of the series resonant oscillator is much higher than that of the parallel resonant oscillator, and the phase noise of the signal generated by the single-core series resonant oscillator is much lower than that of the single-core parallel resonant oscillator. The single-core series resonant oscillator can realize the low phase noise of the multi-core parallel resonant oscillator. However, the tuning range of the series resonant oscillator is limited. As shown in Figure 4 and Figure 5 , compared with the low-voltage swing signal at the X node of the traditional LC parallel resonant oscillator, the voltage signal at the Y node of the series resonant oscillator has a high swing. In order to ensure the tuning of the variable capacitor and the normal operation, a voltage dividing capacitor or other means is introduced to ensure the safety and reliability of the components, but this will limit the tuning of the series resonant oscillator, and therefore the output frequency range is narrow. SUMMARY

[0006] The purpose of the present application is to solve the problem of limited tuning range of the existing series resonant oscillator, and to provide a series resonant voltage-controlled oscillator with mode switching function, which can ensure the reliability of mode switching when applied, and the parasitic capacitance of the mode switching switch will not be introduced into the series resonant cavity, thereby not compressing the tuning range, and widening the frequency tuning range of the series resonant oscillator.

[0007] The purpose of the present application is mainly realized by the following technical solutions:

[0008] A series resonant voltage-controlled oscillator with mode switching function, comprising a series resonant mode switching switch and two series resonant oscillator units, the two series resonant oscillator units being coupled by capacitive coupling and / or inductive coupling; the series resonant oscillator unit comprising an active negative resistance network and an LC resonant network, the LC resonant network comprising a first inductor, a first capacitor and a second inductor connected in series, the first inductor being connected to the other end of the first capacitor and the second inductor being connected to the other end of the first capacitor and two output terminals of the active negative resistance network one by one; a first node is provided on the line between the first inductor and the active negative resistance network, and a second node is provided on the line between the second inductor and the active negative resistance network, the series resonant mode switching switch being used to control the switching of the two series resonant oscillator units in even mode and odd mode; wherein, when the two series resonant oscillator units are in even mode, the first nodes of the two series resonant oscillator units are connected, and the second nodes of the two series resonant oscillator units are connected; when the two series resonant oscillator units are in odd mode, the first node of each series resonant oscillator unit is connected to the second node of the other series resonant oscillator unit.

[0009] Further, when the two series resonant oscillator units are connected by capacitive coupling, two coupling capacitors are used, one coupling capacitor being connected to the line between the first inductor and the first capacitor of the two series resonant oscillator units, and the other coupling capacitor being connected to the line between the second inductor and the first capacitor of the two series resonant oscillator units.

[0010] Further, the active negative resistance network is realized by NMOS-NMOS inverter negative resistance circuit, PMOS-NMOS inverter negative resistance circuit, transistor negative resistance circuit or cross-pair tube negative resistance circuit.

[0011] Further, the first capacitor is realized by fixed capacitor, varactor diode or switched capacitor.

[0012] Further, the first inductor and the second inductor are realized by fixed inductor, switched inductor or switched coupling transformer.

[0013] Further, the series resonant mode switching switch is realized by two NMOS tubes directly connected, two PMOS tubes directly connected, two transistors directly connected, four NMOS tubes cross-connected, four PMOS tubes cross-connected or four transistors cross-connected.

[0014] Compared with the prior art, the application has the following beneficial effects: the application is composed of two series resonant oscillator units coupled together, both of the two series resonant oscillator units have their own current directions, when the two oscillator units are coupled together, two different resonant frequencies can be obtained by changing the relative polarity of the two series resonant oscillator units through a mode switching switch. Compared with the traditional parallel mode switching technology, the series resonant mode switching switch proposed in the application is not located at a high-voltage swing node but at a low-voltage node, thereby ensuring the reliability of mode switching. Meanwhile, the parasitic capacitance of the mode switching switch will not introduce a series resonant cavity, thereby not compressing the tuning range, so that the frequency tuning range of the application is also widened. BRIEF DESCRIPTION OF DRAWINGS

[0015] The accompanying drawings, which are included to provide a further understanding of the embodiments of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the embodiments of the application. In the drawings:

[0016] Figure 1 LC voltage-controlled oscillator schematic diagram;

[0017] Figure 2 LC voltage-controlled oscillator energy compensation schematic diagram;

[0018] Figure 3 Parallel resonant mode switching oscillator structure schematic diagram;

[0019] Figure 4 Series resonant oscillator schematic diagram;

[0020] Figure 5 Parallel resonant oscillator schematic diagram;

[0021] Figure 6 Structure schematic diagram of the application in a specific embodiment adopting capacitive coupling mode coupling connection;

[0022] Figure 7 NMOS-NMOS inverter negative resistance circuit schematic diagram;

[0023] Figure 8 PMOS-NMOS inverter negative resistance circuit schematic diagram;

[0024] Figure 9 Triode negative resistance circuit schematic diagram;

[0025] Figure 10 Crossed pair tube negative resistance circuit schematic diagram;

[0026] Figure 11 Series resonant mode switching switch implementation form schematic diagram;

[0027] Figure 12This is a schematic diagram of a mode switching principle when a capacitive coupling connection is adopted in a specific embodiment of the present invention;

[0028] Figure 13 A schematic diagram comparing a capacitive coupling connection with a parallel resonant mode switching according to a specific embodiment of the present invention;

[0029] Figure 14 This is a schematic diagram of a specific embodiment of the present invention using an inductive coupling method for coupling connection;

[0030] Figure 15 This is a schematic diagram of a specific embodiment of the present invention using both capacitive coupling and inductive coupling;

[0031] Figure 16 Schematic diagram of the coupling mode between multi-core series resonant oscillators. DETAILED DESCRIPTION

[0032] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with examples and drawings. The exemplary embodiments of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.

[0033] Example 1:

[0034] like Figure 6 As shown, a series resonant voltage-controlled oscillator with a mode switching function includes a series resonant mode switching switch and two series resonant oscillator units, and the two series resonant oscillator units are coupled and connected in a capacitive coupling manner. Figure 6 The two series resonant oscillator units are respectively series resonant oscillator unit 1 and series resonant oscillator unit 2. The series resonant oscillator units of this embodiment include an active negative resistance network and an LC resonant network. The LC resonant network includes a first inductor L1, a first capacitor C1, and a second inductor L2 connected in series. The other end of the first inductor L1 connected to the first capacitor C1 and the other end of the second inductor L2 connected to the first capacitor C1 are connected to the two output ends of the active negative resistance network in a one-to-one correspondence. In this embodiment, a first node is provided on the line between the first inductor L1 and the active negative resistance network, and a second node is provided on the line between the second inductor L2 and the active negative resistance network. The series resonant mode switch of this embodiment is used to control the two series resonant oscillator units to switch between even mode and odd mode. When the two series resonant oscillator units are in even mode, the first nodes of the two series resonant oscillator units are connected, and the second nodes of the two series resonant oscillator units are connected. When the two series resonant oscillator units are in odd mode, the first node of each series resonant oscillator unit is connected to the second node of the other series resonant oscillator unit.

[0035] The two series resonant oscillator units of this embodiment are connected through capacitive coupling and are specifically implemented by two coupling capacitors. The two coupling capacitors correspond to Figure 6 The capacitor C m The two ends of one coupling capacitor are respectively connected to the line between the first inductor L1 and the first capacitor C1 of the two series resonant oscillator units, and the two ends of the other coupling capacitor are respectively connected to the line between the second inductor L2 and the first capacitor C1 of the two series resonant oscillator units.

[0036] The active negative resistance network of this embodiment is implemented by using an NMOS-NMOS inverter negative resistance circuit, a PMOS-NMOS inverter negative resistance circuit, a transistor negative resistance circuit or a cross-pair transistor negative resistance circuit. Figure 7 As shown, the schematic diagram of the negative resistance circuit of the PMOS-NMOS inverter is as follows Figure 8 As shown, the schematic diagram of the transistor negative resistance circuit is as follows Figure 9 As shown, the schematic diagram of the cross-pair negative resistance circuit is as follows Figure 10 As shown, different active circuits have different performances such as phase noise and power consumption, and can be selected according to the performance requirements.

[0037] The first capacitor C1 of this embodiment is implemented using a fixed capacitor, a varactor diode, or a switched capacitor. The first capacitor L1 of this embodiment is connected to both sides of the differential terminal. This embodiment can adjust the output frequency by controlling the capacitance variation. By adjusting the number of capacitor groups and the size of the first capacitor L1, different frequency tuning ranges can be achieved, thereby achieving continuous coverage of the oscillator output frequency.

[0038] In this embodiment, the first inductor L1 and the second inductor L2 are implemented using fixed inductors, switched inductors, or switched coupling transformers. This embodiment can adjust the output frequency by controlling the inductor variation. By adjusting the inductor switches, different equivalent inductance values ​​can be obtained, thereby achieving different frequency tuning ranges.

[0039] like Figure 11 As shown, the series resonant mode switch of this embodiment is implemented by directly connecting two NMOS tubes, directly connecting two PMOS tubes, directly connecting two transistors, cross-connecting four NMOS tubes, cross-connecting four PMOS tubes or cross-connecting four transistors. Figure 11In the embodiment, P1+ is the first node of the series resonant oscillator unit 1, P1- is the second node of the series resonant oscillator unit 1, P2+ is the first node of the series resonant oscillator unit 2, and P2- is the second node of the series resonant oscillator unit 2. This embodiment operates in the same phase in the even mode and in the opposite phase in the odd mode. When the same phase operation is required, the switch in the same phase operation is closed, the switch in the opposite phase operation is opened, P1+ and P2+ are connected together, and P1- and P2- are connected together. When the opposite phase operation is required, the switch in the same phase operation is opened, the switch in the opposite phase operation is closed, P1+ and P2- are connected together, and P1- and P2+ are connected together.

[0040] The parallel resonant oscillator mode switch is located at the nodes on both sides of the capacitor. If the series resonant mode switch is also located at the nodes on both sides of the capacitor, the high swing voltage of the series resonance will face the problems of mode switching reliability and the parasitic capacitance of the mode switch will introduce the resonator into the compressed frequency tuning range. The two series resonant oscillator units of this embodiment are coupled by a capacitor C m Coupled together, and then use the mode switching switch circuit to switch between odd and even modes. Different from the mode switching switch circuit based on parallel resonance, the series resonance mode switch circuit of this embodiment does not have a coupling capacitor C m At both ends, thus avoiding the parasitic capacitance of the mode switching switch to be introduced into the resonant cavity, resulting in a compressed frequency tuning range. At the same time, the series resonant mode switching switch is not at C m This also avoids the mode switching instability and reliability issues caused by high swing voltage signals.

[0041] like Figure 12 As shown, in this embodiment, in odd mode, the input voltages of the two resonators are differential, so the coupling capacitor C m The voltage across the two ends is differential, then C m The virtual ground in the middle, the equivalent capacitance of the resonator is C+2C m , the odd-mode resonant frequency is ω odd =[L(C+2C m )] -1 / 2 。 In even mode, the input voltages of the two resonators are in phase, so no current flows through C m , C m is short-circuited, the equivalent capacitance of the resonator is C, and the even-mode resonant frequency is ω even =(LC) -1 / 2 。

[0042] Figure 13 The comparison between the mode switching technology of this embodiment and parallel resonance is shown. Figure 13For the parallel resonance of (a), the mode switching circuit is located between the capacitor C and the coupling capacitor C m Therefore, the parasitic capacitance of the switch will be introduced into the capacitor network, and then into the parallel resonant cavity, compressing the frequency tuning range. Figure 13 (b) For the proposed series resonant mode switching switch, the mode switching circuit is not located between the capacitor C and the coupling capacitor C. m The capacitor port network of the series resonant mode is not connected to the capacitor port network, so the parasitic capacitance of the switch will not be introduced into the capacitor network and the frequency tuning range will not be compressed. m This also avoids coupling C m The high swing voltage signals at both ends cause mode switching instability and reliability issues.

[0043] This embodiment achieves a wide tuning range and extremely low phase noise. By switching the coupling modes of the two series resonator oscillator units through a series resonant mode switching switch, two different oscillation frequencies are achieved, significantly increasing the output frequency range of the series resonant oscillator. Furthermore, the mode switching switch is not located within the series resonant cavity, minimizing the impact on phase noise and frequency tuning range. Therefore, compared to conventional series resonant oscillators, the present invention significantly increases the output frequency range and offers advantages in overall performance.

[0044] Example 2:

[0045] like Figure 14 As shown, the difference between this embodiment and embodiment 1 is that the two series resonant oscillator units in this embodiment are coupled and connected in an inductive coupling manner.

[0046] Example 3:

[0047] like Figure 15 As shown, the difference between this embodiment and embodiment 1 and embodiment 2 is that the two series resonant oscillator units in this embodiment are coupled and connected by capacitive coupling and inductive coupling at the same time.

[0048] Example 4:

[0049] The difference between this embodiment and any one of the embodiments 1 to 3 is that: Figure 16 As shown, the series resonant oscillator of this embodiment is expanded to 2 N Nuclear. Figure 16 As shown, taking the quad-core as an example, there are three coupling modes between oscillators:

[0050] Coupling method 1: Figure 16 The two series resonant oscillators on both sides of ①, ②, ③ and ④ are connected through capacitive coupling;

[0051] Coupling mode two: Figure 16 The two series resonance oscillators on the left and right sides of ①, ②, ③ and ④ are connected through inductive coupling;

[0052] Coupling mode three: Figure 16 The two series resonance oscillators on the left and right sides of ① and ③ are connected through inductive coupling; Figure 16 The two series resonance oscillators on the left and right sides of ② and ④ are connected through capacitive coupling. This embodiment is extended to multiple modes of multi-core oscillators, which can further expand the frequency tuning range.

[0053] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A series resonant voltage-controlled oscillator with a mode switching function, characterized in that: The invention comprises a series resonant mode switching switch and two series resonant oscillator units; the series resonant oscillator unit comprises an active negative resistance network and an LC resonant network, the LC resonant network comprises a first inductor, a first capacitor and a second inductor connected in series in sequence, the other end of the first inductor being connected to the first capacitor end and the other end of the second inductor being connected to the first capacitor end are connected to the two output ends of the active negative resistance network in a one-to-one correspondence; a first node is provided on the line between the first inductor and the active negative resistance network, and a second node is provided on the line between the second inductor and the active negative resistance network; the series resonant mode switching switch is used to control the two series resonant oscillator units to switch between an even mode mode and an odd mode mode; wherein, when the two series resonant oscillator units are in the even mode mode, the first nodes of the two series resonant oscillator units are connected and the second nodes of the two series resonant oscillator units are connected; when the two series resonant oscillator units are in the odd mode mode, the first node of each series resonant oscillator unit is connected to the second node of the other series resonant oscillator unit; The two series resonant oscillator units are respectively a first series resonant oscillator unit and a second series resonant oscillator unit. The first series resonant oscillator unit and the second series resonant oscillator unit are coupled and connected in a capacitive coupling manner through two coupling capacitors; wherein, one end of a coupling capacitor is connected to the line between the first inductor and the first capacitor in the first series resonant oscillator unit, and the other end thereof is connected to the line between the first inductor and the first capacitor in the second series resonant oscillator unit; one end of the other coupling capacitor is connected to the line between the second inductor and the first capacitor in the first series resonant oscillator unit, and the other end thereof is connected to the line between the second inductor and the first capacitor in the second series resonant oscillator unit.

2. The series resonant voltage controlled oscillator with mode switching function according to claim 1, characterized in that: The active negative resistance network is realized by using an NMOS-NMOS inverter negative resistance circuit, a PMOS-NMOS inverter negative resistance circuit, a triode negative resistance circuit or a cross-pair transistor negative resistance circuit.

3. The series resonant voltage controlled oscillator with mode switching function according to claim 1, characterized in that: The first capacitor is implemented by a fixed capacitor, a varactor diode or a switched capacitor.

4. The series resonant voltage controlled oscillator with mode switching function according to claim 1, characterized in that: The first inductor and the second inductor are implemented by using a fixed inductor, a switching inductor or a switching coupling transformer.

5. A series resonant voltage controlled oscillator with mode switching function according to any one of claims 1 to 4, characterized in that: The series resonant mode switching switch is implemented in the form of two NMOS tubes directly connected, two PMOS tubes directly connected, two transistors directly connected, four NMOS tubes cross-connected, four PMOS tubes cross-connected or four transistors cross-connected.

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