CN103107809A - Phase-locked loop circuit - Google Patents
Phase-locked loop circuit Download PDFInfo
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- CN103107809A CN103107809A CN2011103552024A CN201110355202A CN103107809A CN 103107809 A CN103107809 A CN 103107809A CN 2011103552024 A CN2011103552024 A CN 2011103552024A CN 201110355202 A CN201110355202 A CN 201110355202A CN 103107809 A CN103107809 A CN 103107809A
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Abstract
The invention discloses a phase-locked hoop circuit which is used for frequency modulation and composed of a phase discriminator (101), a loop filter (103), a voltage-controlled oscillator (104), a switch unit (106) and a voltage feedback unit (107). By utilizing the phase-locked loop circuit, in the process of modulating a frequency signal, after the phase-locked loop locks frequency, the switch unit (106) and the voltage feedback unit (107) control frequency control voltage of the voltage-controlled oscillator (104). Thus, frequency control voltage of the voltage-controlled oscillator (104) does not change a lot when the phase-locked loop is in an open loop, and therefore drifting of frequency of the voltage-controlled oscillator is reduced.
Description
Technical field
The present invention relates to a kind of phase-locked loop circuit, reduce the circuit of the shift of carrier in modulated process when relating in particular to loop open loop after the locking of phase-locked loop in the direct modulation frequency signal process of voltage controlled oscillator carrier frequency.
Background technology
Please refer to Fig. 1, Fig. 1 is existing phase-locked loop structures circuit, and phase-locked loop is that output phase and fixed phase are relatively obtained the stable system that exports, and is comprised of a phase discriminator, a loop filter and a voltage controlled oscillator.In the communication technology in modern times, frequency modulation(FM) can adopt voltage controlled oscillator directly to modulate, loop open loop after the phase-locked loop locking frequency, and then the signal with modulation directly is modulated on carrier frequency by voltage controlled oscillator.Further, please refer to Fig. 2, Fig. 2 is the another kind of structural circuit of existing phase-locked loop, and phase-locked loop can increase charge pump or frequency divider, improves the performance of system.
With this kind method modulation frequency signal, still need to keep the output frequency (carrier frequency) of voltage controlled oscillator to stablize in certain hour when requiring after the phase-locked loop locking frequency open loop, but, during the phase-locked loop open loop, input due to the frequency control voltage that has disconnected voltage controlled oscillator, the frequency control voltage of voltage controlled oscillator is changed, cause the output frequency of voltage controlled oscillator to drift about.
Summary of the invention
When the main technical problem to be solved in the present invention is the phase-locked loop open loop, reduce the phenomenon that has the input of frequency control voltage to cause the appearance of voltage controlled oscillator output frequency to be drifted about due to voltage controlled oscillator.
For solving the problems of the technologies described above, the invention provides a kind of phase-locked loop circuit, described phase-locked loop circuit also includes switch element and voltage feedback unit and forms except phase discriminator, loop filter, voltage controlled oscillator; Wherein, described switch element is used for controlling by switching signal the FEEDBACK CONTROL voltage input loop filter that described voltage feedback unit is exported when the loop open loop; Described voltage feedback unit is used for producing FEEDBACK CONTROL voltage when loop-locking, and keeps when the loop open loop and export FEEDBACK CONTROL voltage to described switch element.
Further, described switch element can be designed as single metal-oxide-semiconductor switch transmission circuit; Can also be designed to by a PMOS pipe and a NMOS pipe transmission gate circuit that consists of in parallel, an end of transmission gate is connected with the FEEDBACK CONTROL voltage output end of described voltage feedback unit, and the other end is connected with the input of described loop filter; Further, two substrates of described PMOS pipe and NMOS pipe can also all be connected to the voltage end of described FEEDBACK CONTROL, and described metal-oxide-semiconductor electrode structure can be polygon or circle.
Described voltage feedback unit is designed to a voltage follower circuit, the voltage after when following loop-locking, loop filter is processed; Further, described voltage follower circuit is designed to be arranged on the unity gain buffer between described loop filter and described voltage controlled oscillator.
Further, described phase-locked loop circuit can comprise that one is connected to the charge pump between described phase discriminator and loop filter, the frequency divider of can also connecting on the feedback path of described voltage controlled oscillator and described phase discriminator.
The invention has the beneficial effects as follows: during the open loop of phase-locked loop locking frequency loop, control by switching signal the frequency control voltage that voltage feedback unit output feedback voltage is controlled voltage controlled oscillator, can not cause the frequency control voltage of voltage controlled oscillator to change too greatly, reduce the frequency of voltage controlled oscillator and drift about; The passgate structures that switch adopts PMOS and NMOS to compose in parallel, the source of metal-oxide-semiconductor, drain terminal and substrate all maintain on same current potential, can reduce the electric leakage of metal-oxide-semiconductor, thereby reduce the drift of the frequency control voltage of voltage controlled oscillator; Phase-locked loop circuit increases charge pump or frequency divider, better improves Systems balanth.
Description of drawings
Fig. 1 is a kind of structural circuit figure of existing phase-locked loop;
Fig. 2 is the another kind of structural circuit figure of existing phase-locked loop;
Fig. 3 is the phase-locked loop structures circuit diagram in the embodiment of the present invention one;
Fig. 4 is the phase-locked loop switch element structural circuit figure in the embodiment of the present invention one;
Fig. 5 is the planar structure schematic diagram of the phase-locked loop metal-oxide-semiconductor in the embodiment of the present invention one;
Fig. 6 is the phase-locked loop structures circuit diagram in the embodiment of the present invention two;
Fig. 7 is the phase-locked loop structures circuit diagram in the embodiment of the present invention three.
Embodiment
By reference to the accompanying drawings the present invention is described in further detail below by embodiment.
Of the present inventionly mainly be contemplated that: because be during due to the cycle of phase-locked loop open loop, disconnected the input of the frequency control voltage of voltage controlled oscillator, the frequency control voltage of voltage controlled oscillator is changed, caused the output frequency of voltage controlled oscillator to drift about.For the output frequency that reduces voltage controlled oscillator drifts about, way of the present invention is: increase a switch element and a voltage feedback unit in phase-locked loop circuit, like this, when the cycle of phase-locked loop open loop, pass through switch element, voltage feedback unit output feedback voltage is controlled the frequency control voltage of voltage controlled oscillator, and the frequency control voltage of voltage controlled oscillator can not vary widely, thereby can reduce the phenomenon of the output frequency generation drift of voltage controlled oscillator; In addition, increase the performance that charge pump or frequency divider better improve system in phase-locked loop circuit.
Embodiment one:
Please refer to Fig. 3, Fig. 3 is the circuit diagram of the first embodiment of phase-locked loop circuit of the present invention, and described phase-locked loop includes phase discriminator 101, loop filter 103, and voltage controlled oscillator 104, switch element 106, and Voltage Feedback module 107 forms; Wherein, phase discriminator 101 is connected with loop filter 103, loop filter is connected with voltage controlled oscillator 104, the output of voltage controlled oscillator 104 is connected to the feedback signal input of phase discriminator 101, switch element 106 is connected to the input of loop filter 103, and voltage feedback unit 107 is connected on switch element 106.During described cycle of phase-locked loop locking, described phase discriminator 101, described loop filter 103 and described voltage controlled oscillator 104 form loop voltage controlled oscillator 104 output frequencies are locked, the output frequency of voltage controlled oscillator 104 is locked, the described switch element 106 of this process is not worked, and described voltage feedback unit 107 produces feedback voltage; Afterwards, described cycle of phase-locked loop open loop, described switch element 106 is controlled in the described voltage feedback unit 107 described loop filters 103 of output FEEDBACK CONTROL voltage input by switching signal, described loop filter 103 output voltage signals continue to control the frequency control voltage of described voltage controlled oscillator 104, the frequency control voltage of described voltage controlled oscillator 104 can not change too large, can reduce the phenomenon of the drift of described voltage controlled oscillator 104 output frequencies.
described switch element can be designed as the transmission gate that two metal-oxide-semiconductors consist of, the present embodiment adopts by a PMOS pipe and a NMOS pipe transmission gate circuit that consists of in parallel, please refer to Fig. 4, wherein, one end of described transmission gate is connected with the FEEDBACK CONTROL voltage output end of voltage feedback unit, the other end is connected with the frequency control voltage of described voltage controlled oscillator, be that the other end is connected with the input of loop filter 103, because the PMOS pipe is good to the transmission of input signal high level, and the NMOS pipe is good to the low level transmission performance of input signal, PMOS pipe and the parallel connection of NMOS pipe make input signal all to become output signal and not loss, because the POMS pipe is structurally symmetrical with the NMOS pipe, so the input of described transmission gate and output can exchange, when switch element receives switching signal, the feedback voltage of Voltage Feedback module just can be delivered in described loop filter 103 by described transmission gate is break-even, and then the frequency control voltage of control voltage controlled oscillator.
Further, the source of metal-oxide-semiconductor, drain terminal and substrate terminal can be connected with FEEDBACK CONTROL voltage, the source of metal-oxide-semiconductor, drain terminal, lining end all maintain on same current potential like this, can reduce the electric leakage of metal-oxide-semiconductor, reduce better the drift of the output frequency of voltage controlled oscillator.Described switch element can also be designed to the switch transmission circuit of simple single metal-oxide-semiconductor, does not do detailed elaboration at this.
Further, the metal-oxide-semiconductor of described switch element can be designed as various shape, as triangle, and polygon, circular etc., consider the electric leakage of metal-oxide-semiconductor, the present embodiment is designed to octagon, please refer to Fig. 5, wherein, the drain electrode of metal-oxide-semiconductor is in the inside, and the source electrode of metal-oxide-semiconductor is at outermost, one side the grid of metal-oxide-semiconductor is in the middle of drain electrode and source electrode and outwards drawing at octagon.
Embodiment two:
please refer to Fig. 6, Fig. 6 is the circuit diagram of the another kind of embodiment of phase-locked loop circuit of the present invention, described phase-locked loop includes phase frequency detector 101 ', charge pump 102, loop filter 103, voltage controlled oscillator 104, switch element 106, and Voltage Feedback module 107 forms, wherein, phase frequency detector 101 ' is connected with charge pump 102, charge pump 102 is connected with loop filter 103, loop filter 103 is connected with voltage controlled oscillator 104, the output of controlled oscillator 104 is connected to the feedback signal input of phase frequency detector 101 ', switch element 106 is connected to the input of loop filter 103, voltage feedback unit 107 is connected on switch element 106, when described cycle of phase-locked loop closed pair voltage controlled oscillator output frequency locks, the output signal of described phase frequency detector 101 ' is fainter, described charge pump 102 can amplify the output signal of described phase frequency detector 101 ', for the capacitor charge and discharge of described loop filter 103, guarantee loop stability and improve loop tracks performance and noise characteristic.Further, on the feedback path of voltage controlled oscillator 104 and phase frequency detector 101 ', a frequency divider 105 can also be set, wherein frequency divider 105 is connected on the feedback path of described voltage controlled oscillator 104 and phase frequency detector 101 '; The clock signal of system is provided due to the general quartz crystal oscillator that adopts, and the frequency of quartz crystal oscillator is not easy to change, the output signal of 105 pairs of described voltage controlled oscillators 104 of a frequency divider of connecting on the feedback path of described voltage controlled oscillator 104 and described phase frequency detector 101 ' is carried out frequency division and is processed, and can obtain the frequency signals outputs of satisfying system requirements more.
Embodiment three:
please refer to Fig. 7, Fig. 7 is the circuit diagram of the third embodiment of phase-locked loop circuit of the present invention, described phase-locked loop includes phase frequency detector 101 ', loop filter 103, voltage controlled oscillator 104, switch element 106, and voltage follower circuit 108 forms, wherein, phase frequency detector 101 ' is connected with loop filter 103, loop filter 103 is connected with voltage follower circuit 108, voltage follower circuit 108 is connected with voltage controlled oscillator 104, the output of controlled oscillator 104 is connected to the feedback signal input of phase frequency detector 101 ', switch element 106 is connected to the input of loop filter 103, the output of voltage follower circuit 108 is connected on switch element 106.The output voltage of voltage follower 108 is identical with input voltage, output voltage is followed the variation of input voltage, during the cycle of phase-locked loop locking, the voltage that described voltage follower circuit 108 is followed described loop filter 103 forms feedback voltage, during the cycle of phase-locked loop open loop, described voltage follower circuit 108 keeps formed feedback voltage and feedback voltage is offered described switch element 106, described switch element 106 is delivered to described loop filter 103 to described feedback voltage, and then controls the frequency control voltage of described voltage controlled oscillator.
Further, described voltage follower 108 can also be designed to a unity gain buffer, and wherein, described unity gain buffer is between loop filter 103 and described voltage controlled oscillator 104; The input impedance of unit gain is infinitely great, and output impedance is 0, and output can better be followed the value of input voltage and do not lost.
Further, described phase-locked loop also can increase the performance that charge pump 102 and/or frequency divider 105 improve system, explains in embodiment two, no longer repeats here.
Above content is in conjunction with concrete execution mode further description made for the present invention, can not assert that concrete enforcement of the present invention is confined to these explanations; Therefore, for the general technical staff of the technical field of the invention, without departing from the inventive concept of the premise, can also make some simple deduction or replace, all should be considered as belonging to protection scope of the present invention.
Claims (10)
1. phase-locked loop circuit comprises: phase discriminator, loop filter, voltage controlled oscillator, it is characterized in that, and also comprise: switch element and voltage feedback unit;
Described switch element is used for controlling by switching signal the FEEDBACK CONTROL voltage input loop filter that described voltage feedback unit is exported when the loop open loop;
Described voltage feedback unit is used for producing FEEDBACK CONTROL voltage when loop-locking, and keeps when the loop open loop and export FEEDBACK CONTROL voltage to described switch element.
2. phase-locked loop circuit according to claim 1, is characterized in that, described switch element is single metal-oxide-semiconductor switch transmission circuit.
3. phase-locked loop circuit according to claim 1, it is characterized in that, the transmission gate circuit of described switch element for being consisted of by a PMOS pipe and the parallel connection of a NMOS pipe, described transmission gate circuit one end is connected with the FEEDBACK CONTROL voltage output end of described voltage feedback unit, and the other end is connected with the input of described loop filter.
4. phase-locked loop circuit according to claim 3, is characterized in that, two substrate terminal of described PMOS pipe and NMOS pipe all are connected to the FEEDBACK CONTROL voltage output end of described voltage feedback unit.
5. phase-locked loop circuit according to claim 3, is characterized in that, described voltage feedback unit is voltage follower circuit, the output voltage after when following loop-locking, loop filter filtering is processed.
6. phase-locked loop circuit according to claim 5, is characterized in that, described voltage follower circuit is unity gain buffer, is arranged between described loop filter and described voltage controlled oscillator.
7. according to claim 2-6 described phase-locked loop circuits of any one, is characterized in that, the utmost point distributed architecture of described metal-oxide-semiconductor is polygon or circle.
8. according to claim 1-6 described phase-locked loop circuits of any one, it is characterized in that, also comprise charge pump, described phase discriminator is phase frequency detector, described charge pump is arranged between described phase frequency detector and loop filter, described charge pump is used for the output signal of described phase frequency detector is amplified, and exports to described loop filter.
9. according to claim 1-6 described phase-locked loop circuits of any one, is characterized in that, also comprises frequency divider, is connected on the feedback network of described voltage controlled oscillator and described phase discriminator, is used for that voltage controlled oscillator output signal is carried out frequency division and processes.
10. phase-locked loop circuit according to claim 8, is characterized in that, also comprises frequency divider, is connected on the feedback network of described voltage controlled oscillator and described phase discriminator, is used for that voltage controlled oscillator output signal is carried out frequency division and processes.
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| CN201110355202.4A CN103107809B (en) | 2011-11-10 | 2011-11-10 | A kind of phase-locked loop circuit |
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| CN201110355202.4A CN103107809B (en) | 2011-11-10 | 2011-11-10 | A kind of phase-locked loop circuit |
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| CN103107809A true CN103107809A (en) | 2013-05-15 |
| CN103107809B CN103107809B (en) | 2016-04-27 |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107979370A (en) * | 2017-12-11 | 2018-05-01 | 哈尔滨理工大学 | A kind of high-precision phase-locked loop circuit of broadband |
| CN111262582A (en) * | 2020-02-13 | 2020-06-09 | 广州全盛威信息技术有限公司 | Ultra-wideband frequency generator for generating multi-phase local oscillator signals |
| WO2020155015A1 (en) * | 2019-01-31 | 2020-08-06 | 华为技术有限公司 | Cmos transistor, circuit for driving liquid crystal pixels, and cmos transmission gate |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2001018968A1 (en) * | 1999-09-07 | 2001-03-15 | Telefonaktiebolaget Lm Ericsson (Publ) | Method and arrangement for locking a control voltage to a voltage-controlled oscillator |
| CN1658508A (en) * | 2005-04-11 | 2005-08-24 | 威盛电子股份有限公司 | High-speed double power-supply phase-lock loop |
-
2011
- 2011-11-10 CN CN201110355202.4A patent/CN103107809B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2001018968A1 (en) * | 1999-09-07 | 2001-03-15 | Telefonaktiebolaget Lm Ericsson (Publ) | Method and arrangement for locking a control voltage to a voltage-controlled oscillator |
| CN1372721A (en) * | 1999-09-07 | 2002-10-02 | 艾利森电话股份有限公司 | Method and arrangement for locking a control voltage to voltage-controlled oscillator |
| CN1658508A (en) * | 2005-04-11 | 2005-08-24 | 威盛电子股份有限公司 | High-speed double power-supply phase-lock loop |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107979370A (en) * | 2017-12-11 | 2018-05-01 | 哈尔滨理工大学 | A kind of high-precision phase-locked loop circuit of broadband |
| WO2020155015A1 (en) * | 2019-01-31 | 2020-08-06 | 华为技术有限公司 | Cmos transistor, circuit for driving liquid crystal pixels, and cmos transmission gate |
| CN112823474A (en) * | 2019-01-31 | 2021-05-18 | 华为技术有限公司 | CMOS transistor, circuit for driving liquid crystal pixel and CMOS transmission gate |
| CN111262582A (en) * | 2020-02-13 | 2020-06-09 | 广州全盛威信息技术有限公司 | Ultra-wideband frequency generator for generating multi-phase local oscillator signals |
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| CN103107809B (en) | 2016-04-27 |
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