LU101285B1

LU101285B1 - Switchable dual-core injection-locked frequency divider with wide locking range

Info

Publication number: LU101285B1
Application number: LU101285A
Authority: LU
Inventors: Jianguo Ma; Shaohua Zhou
Original assignee: Qingdao Institute For Ocean Technology Of Tianjin Univ
Priority date: 2018-12-12
Filing date: 2019-07-02
Publication date: 2019-11-08
Also published as: CN111313892B; CN111313892A

Abstract

A switchable dual-core injection-locked frequency divider with a wide locking range utilizes different parasitic capacitances of cross-coupling transistors when two cores are turned on and off, so that two self-resonant frequencies of the frequency divider are distributed at different frequencies. The addition of locking ranges in two modes greatly expands the overall locking range; in the two modes, the oscillations both are at a lower resonance point of a transformer, and the quality factor of a resonant cavity is optimized to improve the phase noise of the frequency divider. By optimizing parameters of components such as the transformer, injection transistors, and cross-coupling transistors, a better overall performance can be achieved in terms of power consumption, an output power and the like; and the structure is simple and easy to integrate.

Description

SWITCHABLE DUAL-CORE INJECTION-LOCKED FREQUENCY DIVIDER WITH WIDE LOCKING RANGE

Technical field

The present invention belongs to the field of microwave engineering, and specifically relates to a switchable dual-core injection-locked frequency divider with a wide locking range.

Technical background A frequency divider is one of critical modules in a phase-locked loop system, and its performance will directly affect the quality of a signal source and the overall performance of a transceiver system. While implementing a frequency division function, we must comprehensively consider the performance indicators such as locking range, power consumption, phase noise, output power and chip area of the frequency divider. The frequency divider can be divided into a static frequency divider, a regenerative frequency divider and an injection-locked frequency divider. Among them, the injection-locked frequency divider has attracted continuous attention due to its high operating frequency and low power consumption. In the phase-locked loop system, the locking range of the injection-locked frequency divider needs to cover an output frequency range of a voltage-controlled oscillator. In order to avoid the influence of process deviation, the performance of the phase-locked loop system is ensured to be good, and achieving a wide locking range has become a major challenge in the design of an injection-locked frequency divider.

At present, a variety of techniques for expanding the locking range have been applied to the design of injection-locked frequency dividers. In 2013, Yue Chao and Howard C. Luong proposed a frequency tracking method that can increase the injection efficiency of an injection transistor and improve the locking range [1], In 2016, Sheng Lyang Jang et al. used a third-order resonant cavity to reduce the quality factor of a resonant cavity of a frequency divider, thereby increasing the locking range [2], In 2017, Alireza Imani and Hossein Hashemi proposed a distributed injection method, which uses the energy injected by multiple nodes to make the frequency divider perform the frequency division function at more resonance points and increase the bandwidth [3]. However, the existing methods described above have a limited effect on the improvement of the locking range, and fail to achieve an optimal compromise between various indicators, and cannot meet the strict requirements of a system for an injection-locked frequency divider.

Therefore, how to better expand the locking range has become a critical issue in the design of injection-locked frequency dividers.

[References] [1] Y. Chao and H. C. Luong,“Analysis and Design of a 2.9-mW 53.4-79.4-GHz Frequency-Tracking Injection-Locked Frequency Divider in 65-nm CMOS”,IEEE J. Solid-State Circuits, vol. 48, no. 10, pp. 2403-2418, Oct. 2013.

[2] S. L. Jang et al. “Triple-Resonance RLC-Tank Divide-By-2 Injection-Locked Frequency Divider”, Electronics Letters, vol. 52, no. 8, pp. 624-626, April 2016.

[3] Alireza Imani and Hossein Hashemi, “Distributed Injection-Locked Frequency Dividers”, IEEE J. Solid-State Circuits, vol. 52. no. 8. pp. 2083-2093. August 2017.

Summary of the invention

In order to solve the problems existing in the prior art, the present invention proposes a switchable dual-core injection-locked frequency divider with a wide locking range, which can realize a wider locking range and achieve better performance in terms of indicators such as phase noise, power consumption, output power. It has a better application prospect. A switchable dual-core injection-locked frequency divider with a wide locking range is proposed, which consists of two cores and one transformer. Each core is an injection-locked frequency divider with an LC structure. Taking core 1 as an example, sources and drains of a nMOS transistor M5 and a pMOS transistor M6 are separately connected as a pair of differential injection transistors, and an injected double frequency signal and an output feedback signal are mixed to obtain a fundamental frequency component; wherein L1 to L3 form one strong coupling transformer, as a resonant cavity of the frequency divider circuit, wherein the divided signals is filtered to obtain a final output signal, two ends of L1 and L2 are connected to sources and drains of the injection transistors, and two ends of L3 are used as differential output terminals; a gate of M1 is connected to a drain of M2, and a gate of M2 is connected to a drain of M1 to form a pair of cross-coupling transistors whose sources are connected to a tail current source, so that core 1 can be turned on or off by changing the magnitude of the tail current. The structural composition and connection relationship of core 2 are the same as core 1.

When one of the cores is turned on, the core is used to perform a frequency dividing function, and its cross-coupling transistors provide a negative resistance to the circuit to compensate for a loss of the entire resonant cavity. When the other core is turned off, its cross-coupling transistors can be regarded as an active capacitor, which becomes a part of the resonant cavity of the core turned on, improving its quality factor, and vice versa. The two cores operate alternately to realize two modes of the switchable dual-core injection locked frequency divider.

The transformer in this topology has two functions. On the one hand, it makes two independently operable cores coupled together, and makes full use of their characteristics when being turned off, further improving the quality factor of the resonant cavity of the frequency divider and improving phase noise; and on the other hand, it realizes coupling output of signals of the frequency divider and increases an output power. A switchable dual-core injection locked frequency divider with a wide locking range utilizes different parasitic capacitances of cross-coupling transistors when two cores are turned on and off, so that two self-resonant frequencies of the frequency divider are distributed at different frequencies. The addition of locking ranges in two modes greatly expands the overall locking range; in the two modes, the oscillations both are at a lower resonance point of a transformer, and the quality factor of a resonant cavity is optimized to improve the phase noise of the frequency divider. By optimizing parameters of components such as the transformer, injection transistors, and cross-coupling transistors, a better overall performance can be achieved in terms of power consumption, an output power and the like; and the structure is simple and easy to integrate.

Brief description of the drawings

Fig. 1 is a schematic diagram of a switchable dual core injection-locked frequency divider with a wide locking range; and

Fig. 2 is a schematic diagram of the operating frequency distribution of mode 1 and mode 2 of the frequency divider.

Detailed description of the embodiments

In order to more clearly explain the technical solutions of the present invention, the present invention will be further described below in conjunction with the accompanying drawings.

An injection-locked frequency divider with an LC structure can be expressed by Equation (1) to indicate the relationship between its locking range and circuit parameters:

(1) where Q is the quality factor of a resonant cavity, footer is the self-resonant frequency of the frequency divider, η is the injection efficiency of an injection transistor, linj is an injection current, and losc is a DC current of the frequency divider circuit.

It can be seen that in order to expand the locking range of the frequency divider, it is necessary to increase the injection efficiency η and reduce the quality factor Q of the resonant cavity. However, in order to ensure a gain condition of the frequency divider and make it work stably, the Q value needs to be sufficiently large; otherwise the power consumption of the circuit may greatly increase. The topology proposed by the invention can effectively improve the injection efficiency η of the injection transistor, and achieve a better overall performance of the frequency divider by selecting an appropriate quality factor Q of the resonant cavity.

As shown in Fig. 1, core 1 and core 2 are injection-locked frequency dividers with two LC structures, respectively. Among them, M1 to M4 are cross-coupling transistors, which provide a negative resistance to the circuit of the frequency divider when being turned on, and compensates for the loss of the resonant cavity. M5 to M8 are injection transistors that acts as a mixer to mix an injected double frequency signal with a fundamental frequency feedback signal to obtain a

fundamental frequency output and perform the frequency division function. The injection transistors of this topology adopt a form where sources and drains of a pair of nMOS and pMOS are separately connected, and while the differential injection is realized, the transconductance is enhanced, improving the injection efficiency, and reducing the magnitude of overall parasitic capacitance, so that the locking range of the frequency divider has been improved. The transformer adopts a combination of coaxial coupling and vertical coupling to reduce the parasitic capacitance of the transformer and make the coupling coefficients between L1, L2 and L3 almost equal. Finally, the fundamental frequency signal is differentially output by the coupling of the transformer.

The switchable dual-core structure proposed by the present invention fully utilizes the parasitic capacitance of different cross-coupling transistors when the two cores are turned on and off, and further improves the quality factor of the resonant cavity compared with the existing frequency divider topology. Since the self-resonant frequencies of the two cores both are at a lower resonance point of the transformer, the Q value is larger, so that the phase noise of the frequency divider is optimized. In addition, when the tail current is small, the cross-coupling transistor is no longer used as a module providing a negative resistance, but is considered to be an active capacitor as a part of the resonant cavity. By selecting an appropriate tail current value, the quality factor is set so that it can be compromised between the phase noise and the lock range for obtaining a better overall performance.

The switching between the two modes of this topology is achieved by changing the magnitude of the tail current sources lBi and lB2. In a conventional switching mode, a switch structure with a larger loss is often used. However, the present invention uses a tail current source for switching, which reduces its influence on the quality factor of the resonant cavity, and is improved in terms of the lock range and the phase noise. As shown in Fig. 2, when the value of Ib2 is small, core 1 is turned on, core 2 is turned off, and the frequency divider enters mode 1. This topology can be frequency divided in the range of fo to f-|. In contrast, when the value of lBi is small, core 2 is turned on, core 1 is turned off, and the frequency divider enters mode 2. Since the parasitic capacitances of M1, M2, M3, and M4 are different in the two cores, and the parameters of the cross-coupling transistors are different, the operating frequency band of the frequency divider can be shifted up, and it is frequency divided in the range of f2 to f3. By adjusting the component parameters so that f2^fi, the locking ranges of the two modes are connected to become an overall wide locking range, namely, fo to f3, which significantly improves the performance of the frequency divider.

Claims

1. Umschaltbarer1. Switchable

2-Kern-Frequenzteiler mit Injektionsverriegelung und großem Verriegelungsbereich, dadurch gekennzeichnet, dass er aus zwei Kernen und einem Transformator besteht, wobei jeder Kern ein injektionsverriegelter Frequenzteiler mit LC-Struktur ist; wobei in Kern 1 die Sources und Drains eines nMOS-Transistors M5 und eines pMOS-Transistors M6 getrennt als ein Paar Differentialinjektionstransistoren verbunden sind, und ein injiziertes Doppelfrequenzsignal und ein Ausgangsrückkopplungssignal gemischt werden, um eine Grundfrequenzkomponente zu erhalten, und wobei L1 bis L3 einen starken Kopplungstransformator als Resonanzhohlraum der Frequenzteilerschaltung bilden, wobei die geteilten Signale gefiltert werden, um ein endgültiges Ausgangssignal zu erhalten, wobei zwei Enden von L1 und L2 mit Sources und Drains der Injektionstransistoren verbunden sind und zwei Enden von L3 als Differenzausgangsanschlüsse verwendet werden; wobei ein Gate von M1 mit einem Drain von M2 verbunden ist und ein Gate von M2 mit einem Drain von M1 verbunden ist, um ein Paar von Kreuzkopplungstransistoren zu bilden, deren Sources mit einer Schwanzstromquelle verbunden sind, so dass der Kern 1 durch Ändern der Größe des Schwanzstroms ein- oder ausgeschaltet werden kann; wobei die strukturelle Zusammensetzung und die Verbindungsbeziehung des Kerns 2 die gleichen sind wie die des Kerns 1; wobei wenn einer der Kerne eingeschaltet ist, der Kern verwendet wird, um eine Frequenzteilungsfunktion auszuführen, und seine Kreuzkopplungstransistoren einen negativen Widerstand für die Schaltung liefern, um einen Verlust des gesamten Resonanzhohlraums zu kompensieren, wobei wenn der andere Kern ausgeschaltet ist, seine Kreuzkopplungstransistoren als aktiver Kondensator betrachtet werden können, der ein Teil des Resonanzhohlraums des eingeschalteten Kerns wird, wodurch sein Qualitätsfaktor verbessert wird, und umgekehrt, und wobei die zwei Kerne abwechselnd arbeiten, um zwei Modi des umschaltbaren injektionsverriegelten Doppelkern-Frequenzteilers zu realisieren; wobei einerseits der Transformator zwei unabhängig voneinander betreibbare Kerne miteinander gekoppelt macht und ihre Eigenschaften beim Ausschalten voll ausnutzt, wodurch der Qualitätsfaktor des Resonanzhohlraums des Frequenzteilers weiter verbessert und das Phasenrauschen verbessert wird, und andererseits es eine Kopplungsausgabe von Signalen des Frequenzteilers realisiert und eine Ausgangsleistung erhöht.Injection-locked, dual-core frequency divider having a large interlocking area, characterized in that it consists of two cores and one transformer, each core being an LC-locked injection locked frequency divider; wherein in core 1, the sources and drains of an nMOS transistor M5 and a pMOS transistor M6 are separately connected as a pair of differential injection transistors, and an injected dual frequency signal and an output feedback signal are mixed to obtain a fundamental frequency component, and L1 to L3 are strong Forming the coupling transformer as the resonant cavity of the frequency divider circuit, wherein the divided signals are filtered to obtain a final output signal, wherein two ends of L1 and L2 are connected to sources and drains of the injection transistors and two ends of L3 are used as differential output terminals; wherein a gate of M1 is connected to a drain of M2 and a gate of M2 is connected to a drain of M1 to form a pair of cross-coupling transistors whose sources are connected to a tail current source so that the core 1 is changed by changing the size the tail current can be switched on or off; wherein the structural composition and the bonding relationship of the core 2 are the same as those of the core 1; wherein when one of the cores is on, the core is used to perform a frequency division function, and its cross coupling transistors provide a negative resistance to the circuit to compensate for loss of the entire resonant cavity, with the other core being off, its cross coupling transistors as more active Capacitor, which becomes part of the resonant cavity of the turned-on core, thereby improving its quality factor, and vice versa, and wherein the two cores operate alternately to realize two modes of the switchable injection-locked dual-core frequency divider; on the one hand, the transformer makes two independently operable cores coupled to each other and fully utilizes their properties at turn-off, further improving the quality factor of the resonance cavity of the frequency divider and improving phase noise, and on the other hand realizing coupling output of signals from the frequency divider and increasing output power.