A gain-variable numerically controlled oscillator

Abstract

This invention discloses a gain-variable numerically controlled oscillator, comprising a current-controlled oscillator, a coarse-tuning control circuit, a mid-tuning control circuit, a fine-tuning control circuit, and a gain-adjustable circuit. The coarse-tuning, mid-tuning, and fine-tuning control circuits control the current flowing into the current-controlled oscillator to control its oscillation frequency. The gain-adjustable circuit controls the current in the fine-tuning control circuit to control the frequency gain of the numerically controlled oscillator. By controlling the current in the fine-tuning control circuit through the gain-adjustable circuit to control the frequency gain of the numerically controlled oscillator, the flexibility of the system is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a gain variable digital controlled oscillator, belonging to the technical field of digital controlled oscillator. BACKGROUND

[0002] The digital controlled oscillator is an electronic oscillator whose oscillation frequency is controlled by digital code. The input digital code applied determines the instantaneous oscillation frequency. The digital controlled oscillator can be applied in all-digital phase-locked loop. The digital controlled oscillator can adopt the structure of current steering digital-to-analog converter and current controlled oscillator, and the digital code controls the current of the current steering digital-to-analog converter flowing into the current controlled oscillator to change the oscillation frequency of the digital controlled oscillator.

[0003] However, the existing digital controlled oscillator cannot accurately control the frequency gain, resulting in insufficient flexibility of the whole system.

[0004] The information disclosed in this BACKGROUND section is only for the purpose of increasing the understanding of the background of the present application and should not be taken as admitting that the information forms prior art that is already known to those of ordinary skill in the art. SUMMARY

[0005] The present application aims to overcome the deficiencies in the prior art, and provides a gain variable digital controlled oscillator, which controls the current in the fine tuning control circuit through the gain adjustable circuit to control the frequency gain of the digital controlled oscillator, thereby improving the flexibility of the system.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0007] The present application discloses a gain variable digital controlled oscillator, which comprises a current controlled oscillator, a coarse tuning control circuit, a medium tuning control circuit, a fine tuning control circuit and a gain adjustable circuit,

[0008] The coarse tuning control circuit, the medium tuning control circuit and the fine tuning control circuit are used for controlling the current flowing into the current controlled oscillator to control the oscillation frequency of the digital controlled oscillator.

[0009] The gain adjustable circuit is used for controlling the current in the fine tuning control circuit to control the frequency gain of the digital controlled oscillator.

[0010] Further, the gain adjustable circuit comprises a fourth current steering, a second amplifier, a third power tube, a fourth power tube and a MOS tube,

[0011] The current output end of the fourth current steering is connected with the second amplifier and the third power tube respectively.

[0012] The second amplifier is connected with the third power tube and the fourth power tube respectively.

[0013] The fourth power transistor is connected to a MOS transistor.

[0014] Furthermore, the fine-tuning control circuit includes a third current rudder, one end of which is connected to a MOSFET and the other end is connected to a current-controlled oscillator.

[0015] Furthermore, the current source within the third current rudder adopts a common source, common grid structure.

[0016] Furthermore, the coarse tuning control circuit includes a first amplifier, a first power transistor, a second power transistor, a capacitor, a resistor, and a first current rudder.

[0017] The current output terminal of the first current rudder is connected to the first amplifier and the first power transistor, respectively;

[0018] A capacitor and a resistor are connected between the first gate node of the first power transistor and the second power transistor.

[0019] The second power transistor is connected to a current-controlled oscillator.

[0020] Furthermore, the control word for the first current rudder is encoded using a thermometer.

[0021] Furthermore, the intermediate tuning control circuit includes a first amplifier, a first power transistor, a second power transistor, a capacitor, a resistor, and a second current rudder.

[0022] The current output terminal of the second current rudder is connected to the first amplifier and the first power transistor, respectively;

[0023] A capacitor and a resistor are connected between the first gate node of the first power transistor and the second power transistor.

[0024] The second power transistor is connected to a current-controlled oscillator.

[0025] Furthermore, the control word of the second current rudder is encoded in binary.

[0026] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0027] This invention improves control flexibility by controlling the current flowing into the current-controlled oscillator through coarse tuning control circuit, medium tuning control circuit, and fine tuning control circuit. The gain-adjustable circuit allows control of the current in the fine tuning control circuit, thereby controlling the frequency gain of the digitally controlled oscillator. This enables the frequency gain of the digitally controlled oscillator to be changed via digital codes, and the selection of the gain value is more flexible. Attached Figure Description

[0028] Figure 1 This is a circuit diagram of a variable-gain digitally controlled oscillator.

[0029] Figure 2 This is a schematic diagram of the third current rudder;

[0030] Figure 3 This is a schematic diagram of a fully digital phase-locked loop using a numerically controlled oscillator;

[0031] In the diagram: 1. First amplifier; 2. Second amplifier; 3. Current-controlled oscillator; 4. Resistor; 5. Capacitor; 6. First current rudder; 7. Second current rudder; 8. Third current rudder; 9. Fourth current rudder; 10. MOSFET; 21. First power transistor; 22. Second power transistor; 23. Third power transistor; 24. Fourth power transistor; 31. First port; 32. Second port; 33. Third port; 34. Fourth port; 35. First node; 36. Second node; 37. Third node; 38. Fourth node; 41. First gate node; 42. Second gate node; 801. Fifth port; 802. Sixth port; 803. First transmission gate; 804. Second transmission gate; 805. Inverter. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0033] This embodiment provides a gain-variable numerically controlled oscillator, which includes a current-controlled oscillator 3, a coarse tuning control circuit, a medium tuning control circuit, a fine tuning control circuit, and a gain-adjustable circuit.

[0034] The coarse tuning control circuit, the intermediate tuning control circuit, and the fine tuning control circuit are used to control the current flowing into the current-controlled oscillator 3 in order to control the oscillation frequency of the numerically controlled oscillator.

[0035] The gain-adjustable circuit is used to control the current in the fine-tuning control circuit to control the frequency gain of the numerically controlled oscillator.

[0036] The technical concept of this invention is to control the current in the fine-tuning control circuit by using a gain-adjustable circuit, thereby controlling the current flowing into the current-controlled oscillator 3, and further controlling the frequency gain of the digitally controlled oscillator to improve the overall flexibility.

[0037] like Figure 1 As shown, the coarse tuning control circuit includes a first amplifier 1, a first power transistor 21, a second power transistor 22, a capacitor 5, a resistor 4, and a first current rudder 6; the intermediate tuning control circuit includes a first amplifier 1, a first power transistor 21, a second power transistor 22, a capacitor 5, a resistor 4, and a second current rudder 7. It should be noted that the coarse tuning control circuit and the intermediate tuning control circuit overlap at the first node 35.

[0038] Specifically, one input terminal of the first amplifier 1 is the third port 33, which is connected to the reference voltage, and the other input terminal is connected to the first node 35; the current output terminals of the first current rudder 6 and the second current rudder 7 are connected to the first node 35, so that the output current of the first current rudder 6 or the second current rudder 7 flows into the first amplifier 1.

[0039] The source of the first power transistor 21 is connected to the first port 31, and the first port 31 is connected to the power supply voltage; the drain of the first power transistor 21 is connected to the first node 35; the gate of the first power transistor 21 is connected to the output of the first amplifier 1 through the first gate node 41.

[0040] The first gate node 41 is connected to the gate of the second power transistor 22 via capacitor 5 and resistor 4. Capacitor 5, resistor 4, and the gate of the second power transistor 22 are connected to the second node 36. The source of the second power transistor 22 is connected to the second port 32, which is connected to an analog voltage. The drain of the second power transistor 22 is connected to the third node 37. Capacitor 5 and resistor 4 form a low-pass filter to filter high-frequency noise from the first power transistor 21. Capacitor 5 can be a MOSFET to perform low-pass filtering on the "mirrored" current in the coarse and medium tuning control circuits. It is important to emphasize that, based on the "virtual short" characteristic of the first amplifier 1, the voltage at the first node 35 is equal to the reference voltage, which can suppress the channel modulation effect of the current source in the first current rudder 6 or the second current rudder 7, thereby minimizing the current nonlinearity caused by the channel modulation effect.

[0041] When the current in the first current rudder 6 or the second current rudder 7 changes, the current flowing through the first power transistor 21 also changes accordingly. Since the voltage at the first node 35 remains constant, the change in current is reflected at the first gate node 41 of the first power transistor 21. The gate voltage of the second power transistor 22 changes with the first node 35. In this embodiment, the width-to-length ratio of the first power transistor 21 to the second power transistor 22 is M, so the current flowing into the third node 37 is M times the changing current in the first current rudder 6 or the second current rudder 7. Combining the "virtual off" characteristic of the first amplifier 1 and the continuity of current, the current change in the first current rudder 6 or the second current rudder 7 is converted into the gate voltage of the second power transistor 22.

[0042] In this embodiment, the first port 31 and the second port 32 are connected to the outputs of different low-dropout regulators to avoid noise in the first power transistor 21 and the second power transistor 22 from interfering with each other through the power line.

[0043] The gain-adjustable circuit includes a fourth current rudder 9, a second amplifier 2, a third power transistor 23, a fourth power transistor 24, and a MOSFET 10. The current output terminal of the fourth current rudder 9 is connected to a fourth node 38, which is connected to the input terminal of the second amplifier 2 and the drain of the third power transistor 23. The other output terminal of the second amplifier 2 is connected to a fourth port 34, which is connected to a reference voltage. The gate of the third power transistor 23 is connected to the output terminal of the second amplifier 2 through a second gate node 42, which is connected to the gate of the fourth power transistor 24. The sources of the third power transistor 23 and the fourth power transistor 24 are connected to a second port 32, which is connected to an analog voltage. The drain of the fourth power transistor 24 is connected to the MOSFET 10.

[0044] The fine-tuning control circuit includes a third current rudder 8, one end of which is connected to a MOSFET 10 and the other end is connected to a third node 37.

[0045] To reduce channel modulation effects, the current source within the third current rudder 8 employs a common-source, common-gate structure to increase the output impedance of the current source. For example... Figure 2 As shown, the third current rudder 8 includes an inverter 805, a first transmission gate 803, and a second transmission gate 804. The inverter 805 converts the input signal into a differential signal, which is used to control the first transmission gate 803 and the second transmission gate 804. The first transmission gate 803 is connected to the fifth port 801, which is connected to the power supply voltage. The second transmission gate 804 is connected to the sixth port 802, which is connected to the third node 37 through the current output terminal of the third current rudder 8.

[0046] It should be emphasized that the output current of the second power transistor 22 and the output current of the third current rudder 8 pass through the third node 37 and together constitute the control current of the current-controlled oscillator 3.

[0047] Similar to the way the coarse and medium tuning control circuits control the output current, the current change in the fourth current rudder 9 is directly reflected in the current of the fourth power transistor 24. This current is then mirrored to the current source in the third current rudder 8 through the MOSFET 10. In other words, the current change in the fourth current rudder 9 directly alters the magnitude of the single-bit current in the third current rudder 8. Therefore, the current value of the fine-tuning current source is controlled by the fourth current rudder 9, thereby changing the frequency gain of the current-controlled oscillator 3.

[0048] The control words for the first current rudder 6 and the third current rudder 8 use thermometer encoding to improve linearity. The control word for the second current rudder 7 uses binary encoding.

[0049] like Figure 3The illustrated all-digital phase-locked loop (PLL) uses logic control for frequency calibration. The input control words for the coarse and intermediate tuning control circuits of the numerically controlled oscillator (CNC) are the first current rudder (6) and the second current rudder (7). The input control word for the fine tuning control circuit, the fourth current rudder (9), is provided by a digital filter. The coarse and intermediate tuning control circuits perform frequency locking on the PLL, while the fine tuning control circuit performs phase locking. The fine tuning control circuit controls the current of its own circuit, thus controlling the frequency gain of the CNC oscillator during phase locking. This achieves adjustable frequency gain for the CNC oscillator.

[0050] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0051] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A gain variable digital controlled oscillator, characterized by, The digital controlled oscillator comprises a current-controlled oscillator (3), a coarse tuning control circuit, a medium tuning control circuit, a fine tuning control circuit and a gain adjustable circuit, The coarse tuning control circuit, the medium tuning control circuit and the fine tuning control circuit are used for controlling the current flowing into the current-controlled oscillator (3) to control the oscillation frequency of the digital controlled oscillator. The gain adjustable circuit is used for controlling the current in the fine tuning control circuit to control the frequency gain of the digital controlled oscillator. The gain adjustable circuit comprises a fourth current steering (9), a second amplifier (2), a third power tube (23), a fourth power tube (24) and a MOS tube (10), The current output ends of the fourth current steering (9) are connected with the second amplifier (2) and the third power tube (23) respectively. The second amplifier (2) is connected with the third power tube (23) and the fourth power tube (24) respectively. The fourth power tube (24) is connected with the MOS tube (10). The fine tuning control circuit comprises a third current steering (8), one end of which is connected with the MOS tube (10) and the other end of which is connected with the current-controlled oscillator (3).

2. The variable gain digitally controlled oscillator of claim 1, wherein, The current source in the third current steering (8) adopts a common source and common gate structure.

3. The variable gain digitally controlled oscillator of claim 1, wherein, The coarse tuning control circuit comprises a first amplifier (1), a first power tube (21), a second power tube (22), a capacitor (5), a resistor (4) and a first current steering (6), The current output ends of the first current steering (6) are connected with the first amplifier (1) and the first power tube (21) respectively. The first capacitor node (41) of the first power tube (21) is connected with the second power tube (22) through the capacitor (5) and the resistor (4). The second power tube (22) is connected with the current-controlled oscillator (3).

4. The variable gain digitally controlled oscillator of claim 3, wherein, The control word of the first current steering (6) adopts a thermometer code.

5. The variable gain digitally controlled oscillator of claim 1, wherein, The medium tuning control circuit comprises a first amplifier (1), a first power tube (21), a second power tube (22), a capacitor (5), a resistor (4) and a second current steering (7), The current output ends of the second current steering (7) are connected with the first amplifier (1) and the first power tube (21) respectively. The first capacitor node (41) of the first power tube (21) is connected with the second power tube (22) through the capacitor (5) and the resistor (4). The second power tube (22) is connected with the current-controlled oscillator (3).

6. The variable gain digitally controlled oscillator of claim 5, wherein, The control word of the second current steering (7) adopts a binary code.

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