CN104135233B

CN104135233B - Low-noise voltage-controlled oscillator biasing circuit and frequency source self-calibration method

Info

Publication number: CN104135233B
Application number: CN201310159077.9A
Authority: CN
Inventors: 李旺
Original assignee: CHENGDU CORPRO TECHNOLOGY Co Ltd
Current assignee: CHENGDU CORPRO TECHNOLOGY Co Ltd
Priority date: 2013-05-02
Filing date: 2013-05-02
Publication date: 2017-05-10
Anticipated expiration: 2033-05-02
Also published as: CN104135233A

Abstract

The invention discloses a low-noise voltage-controlled oscillator biasing circuit and a frequency source self-calibration method. A voltage division circuit comprises a resistor R1, a first bipolar junction transistor BJT1 and a second bipolar junction transistor BJT2 which are connected in series in sequence, wherein the R1 is connected with the collector of the BJT1; the emitter of the BJT1 is connected with the collector of the BJT2; the collector of the BJT1 is connected with the base of the BJT1; and the collector of the BJT2 is connected with the base of the BJT2. In a self-calibration state, voltage output by the biasing circuit is connected with the tuning voltage input end and the power supply end of an LC voltage-controlled oscillator respectively. The output noise of the biasing circuit disclosed by the invention is low, a filter capacitor does not need to be added externally, the pins of a chip can be effectively reduced, and the cost is reduced; and when a frequency source is in the self-calibration state, the voltage output by the biasing circuit is connected with the tuning voltage input end and the power supply end of the LC voltage-controlled oscillator respectively, so that influences caused by the change of an output DC (Direct-Current) point due to changes of the resistor and the BJTs in a whole temperature range can be effectively eliminated, and change of the frequency source along with temperature change in the self-calibration state is avoided.

Description

Low-noise voltage-controlled oscillator biasing circuit and frequency source method for self-calibrating

Technical field

The present invention relates to a kind of low-noise voltage-controlled oscillator biasing circuit and frequency source method for self-calibrating.

Background technology

At present, what frequency source circuit was used is LC voltage controlled oscillators, and its structure is as shown in figure 1, it is mainly by negative resistance, inductance Constitute with electric capacity, its power output is：Wherein, L is inductance, and C is electric capacity, and electric capacity C is again by parasitism Three parts of capacitor array of electric capacity, variable capacitance and PLC technology are constituted.The effect of electric capacity C2 and electric capacity C3 be every straight, and Give LC voltage controlled oscillators one DC point by other biasing circuits, make the capacitance of variable capacitance with LC voltage controlled oscillators two ends Voltage（Power end DC and VT input Vtune）The change of pressure reduction and linearly change, its variation relation such as Fig. 2 institutes Show.

As shown in figure 3, traditional biasing circuit typically completes partial pressure by resistance, but due to by series resistance R4, R5 group Into bleeder circuit noise it is relatively large, need outside biasing circuit increase a bulky capacitor（Electric capacity C4 in Fig. 3）Enter Row filtering, which increases the output pin of biasing circuit, increased circuit cost.

The content of the invention

It is an object of the present invention to provide a kind of novel low noise voltage controlled oscillator biasing circuit, using base stage and current collection The extremely short BJT pipes for connecing and high level poly resistance are used as partial pressure unit, and biasing circuit output noise is less, and need not be in outside plus filter Ripple electric capacity, only need to add small capacitances inside biasing circuit, be effectively reduced the pin of chip, reduces cost；

It is a further object to provide a kind of new frequency source method for self-calibrating, in frequency source circuit in certainly During align mode, the voltage of biasing circuit output connects respectively with the VT input and power end of LC voltage controlled oscillators, The change in the range of total temperature of resistance and BJT pipes can effectively be eliminated and caused output DC points change brought impact, be kept away Exempt from the frequency source in self calibration state to be changed by the change of temperature.

The purpose of the present invention is achieved through the following technical solutions：Low-noise voltage-controlled oscillator biasing circuit, with pressure Controlled oscillator is used cooperatively, and for the voltage controlled oscillator in frequency source circuit biasing is provided, it by constant voltage source, bleeder circuit and Filter capacitor C1 is constituted, and described bleeder circuit includes resistance R1, the first bipolar junction transistor BJT1 being sequentially connected in series and the Two bipolar junction transistor BJT2, resistance R1 are connected with the colelctor electrode of the first bipolar junction transistor BJT1, the first dipole The emitter stage of transistor BJT1 is connected with the colelctor electrode of the second bipolar junction transistor BJT2, the first bipolar junction transistor BJT1 Colelctor electrode connect with its base stage, the colelctor electrode of the second bipolar junction transistor BJT2 connects with its base stage；

The first partial pressure in parallel exports branch road between resistance R1 and the base stage of the first bipolar junction transistor BJT1；First is bipolar The second partial pressure in parallel exports branch road between the emitter stage of junction transistor BJT1 and the base stage of the second bipolar junction transistor BJT2； First partial pressure exports branch road and concatenates with filter capacitor C1 with after the second partial pressure output branch circuit parallel connection.

Further, described resistance R1 is high level poly resistance.

Further, described the first partial pressure output branch road and the second partial pressure to be exported and be respectively equipped with switch on branch road.

The emitter stage and filter capacitor C1 of the second bipolar junction transistor BJT2 is grounded respectively.

Low-noise voltage-controlled oscillator biasing circuit frequency source method for self-calibrating, it is comprised the following steps：

（1）When frequency source circuit is in closed loop normal work, voltage and the electricity of LC voltage controlled oscillators that biasing circuit is exported Source connects；

（2）Frequency source circuit be in open loop self calibration state when, biasing circuit output voltage respectively with LC VCOs The VT input of device and power end connect.

Described LC voltage controlled oscillators are made up of two negative resistances parallel with one another, inductance ind and capacitor control circuit, electric capacity Control circuit is again by the capacitance C2, variable capacitance C being sequentially connected in series_VAR1, variable capacitance C_VAR2Constitute with capacitance C3, every The straight indirect LC that the resistance R2 and resistance R3 being serially connected, resistance R2 and resistance R3 are parallel between electric capacity C2 and capacitance C3 The power end of voltage controlled oscillator, variable capacitance C_VAR1With variable capacitance C_VAR2Indirect LC voltage controlled oscillators VT input End.

The invention has the beneficial effects as follows：

1）Using the BJT pipes of base stage and colelctor electrode short circuit and the structure of high level poly resistant series as partial pressure unit, with Traditional biasing circuit for carrying out partial pressure by resistant series is compared, and biasing circuit output noise is less, and need not be in outside plus filter Ripple electric capacity, only need to add small capacitances inside biasing circuit, be effectively reduced the pin of chip, reduces cost；

2）Frequency source circuit be in self calibration state when, biasing circuit output voltage respectively with LC voltage controlled oscillators VT input and power end connect, and can effectively eliminate the change in the range of total temperature of resistance and BJT pipes and caused Output DC points change brought impact, it is to avoid in self calibration state, frequency source is changed by the change of temperature.

Description of the drawings

Fig. 1 is LC voltage-controlled oscillator circuit structural representations；

Fig. 2 is the capacitance of variable capacitance in LC voltage controlled oscillators with the change curve of oscillator both end voltage pressure reduction Figure；

Fig. 3 is conventional bias electrical block diagram；

Fig. 4 is bias circuit construction schematic diagram of the present invention；

Fig. 5 is biasing circuit of the present invention and traditional resistor biasing circuit of divided voltage output voltage noise curve comparison diagram.

Specific embodiment

Technical scheme is described in further detail below in conjunction with the accompanying drawings, but protection scope of the present invention is not limited to Described below.

As shown in figure 4, low-noise voltage-controlled oscillator biasing circuit, uses cooperatively with LC voltage controlled oscillators, it is frequency source electricity LC voltage controlled oscillators in road provide voltage bias point, and it is by constant voltage source LDO_VDD, bleeder circuit and filter capacitor C1 groups Into described bleeder circuit includes high level poly resistance R1, the first bipolar junction transistor BJT1 being sequentially connected in series and second pair The bleeder circuit that pole junction transistor BJT2, high level poly resistance R1 and BJT pipes are composed in series is carried out point to the voltage that LDO is exported Pressure.High level poly resistance R1 is connected with the colelctor electrode of the first bipolar junction transistor BJT1, the first bipolar junction transistor BJT1 Emitter stage be connected with the colelctor electrode of the second bipolar junction transistor BJT2, the colelctor electrode of the first bipolar junction transistor BJT1 with Its base stage connects, and the colelctor electrode of the second bipolar junction transistor BJT2 connects with its base stage；

The first partial pressure in parallel exports branch road between high level poly resistance R1 and the base stage of the first bipolar junction transistor BJT1, First partial pressure exports branch road output voltage point DC1, and the first partial pressure output branch road is provided with switch KG1；First bipolar junction transistor The second partial pressure in parallel exports branch road, the second partial pressure between the emitter stage of pipe BJT1 and the base stage of the second bipolar junction transistor BJT2 Output branch road output voltage point DC2, the second partial pressure output branch road is provided with switch KG2.By the control choosing for switching KG1 and KG2 The capacitance for being selected primarily based upon variable capacitance of the voltage DC, electrical voltage point DC1 and electrical voltage point DC2 of selecting property ground output bias circuit Linear change it is interval, the such as dotted portion of Fig. 2.

First partial pressure exports branch road and concatenates with filter capacitor C1 with after the second partial pressure output branch circuit parallel connection.

As seen in Figure 5：Under the conditions of same LDO output voltages, the present invention adopts the output of biasing circuit Voltage noise（In -17dB or so）Significantly lower than the output voltage noise of traditional employing electric resistance partial pressure configuration biases circuit（- 15dB or so）.

（1）When frequency source circuit is in closed loop normal work, voltage and the electricity of LC voltage controlled oscillators that biasing circuit is exported Source DC end connects；

（2）Frequency source circuit be in open loop self calibration state when, biasing circuit output voltage respectively with LC VCOs The VT input Vtune ends of device and power end DC ends connect.

When frequency source circuit is in self calibration state, the variable capacitance C in LC voltage controlled oscillators_VAR1One terminating resistor R2, the DC ends of a termination biasing circuit（The first partial pressure output branch road can be optionally exported by opening switch KG1 or KG2 defeated The DC1 for the going out or DC2 of the second partial pressure output branch road output）；Variable capacitance C in LC voltage controlled oscillators_VAR2One terminating resistor R3, the DC ends of a termination biasing circuit.

The voltage DC of biasing circuit is not only connected to the DC ports in LC voltage controlled oscillators, and is connected to LC voltage controlled oscillators Vtune ends, this is because the BJT pipes Vbe in biasing circuit can change with the change of temperature so that output bias voltage DC1 and DC2 also can variation with temperature and change, variable capacitance capacitance linearly becomes with both end voltage pressure reduction in observation Fig. 2 Change curve to understand, the central point of the relatively linear part of curve be in the equal position of variable capacitance both end voltage, therefore, can The two ends for becoming electric capacity are all connected on the output voltage DC of biasing circuit so that in self calibration state, and frequency source is not by temperature Change and change.

Claims

1. low-noise voltage-controlled oscillator biasing circuit frequency source method for self-calibrating, the low-noise voltage-controlled oscillator biasing circuit with Voltage controlled oscillator is used cooperatively, and for the voltage controlled oscillator in frequency source circuit biasing is provided, and the low-noise voltage-controlled oscillator is inclined Circuits are made up of constant voltage source, bleeder circuit and filter capacitor C1, and described bleeder circuit includes the resistance being sequentially connected in series R1, the first bipolar junction transistor BJT1 and the second bipolar junction transistor BJT2, resistance R1 and the first bipolar junction transistor The current collection of the colelctor electrode connection of BJT1, the emitter stage of the first bipolar junction transistor BJT1 and the second bipolar junction transistor BJT2 Pole connects, and the colelctor electrode of the first bipolar junction transistor BJT1 connects with its base stage, the collection of the second bipolar junction transistor BJT2 Electrode connects with its base stage；

The first partial pressure in parallel exports branch road between resistance R1 and the base stage of the first bipolar junction transistor BJT1；First dipole The second partial pressure in parallel exports branch road between the emitter stage of transistor BJT1 and the base stage of the second bipolar junction transistor BJT2；First Partial pressure exports branch road and concatenates with filter capacitor C1 with after the second partial pressure output branch circuit parallel connection；Described first partial pressure output branch road and Switch is respectively equipped with second partial pressure output branch road, it is characterised in that：The low-noise voltage-controlled oscillator biasing circuit frequency source Method for self-calibrating is comprised the following steps：

(1) when frequency source circuit is in closed loop normal work, voltage and the power end of LC voltage controlled oscillators that biasing circuit is exported Connection；

(2) frequency source circuit be in open loop self calibration state when, biasing circuit output voltage respectively with LC voltage controlled oscillators VT input and power end connect；Described LC voltage controlled oscillators are by two negative resistances parallel with one another, inductance ind and electricity Hold control circuit composition, capacitor control circuit is again by the capacitance C2, variable capacitance C being sequentially connected in series_VAR1, variable capacitance C_VAR2 With capacitance C3 compositions, the resistance R2 and resistance R3 being serially connected is parallel between capacitance C2 and capacitance C3, electricity The power end of the indirect LC voltage controlled oscillators of resistance R2 and resistance R3, variable capacitance C_VAR1With variable capacitance C_VAR2Indirect LC it is voltage-controlled The VT input of oscillator.