CN103973228B - A kind of C-band voltage controlled oscillator - Google Patents

Abstract

The invention discloses a kind of C-band voltage controlled oscillator, including the load circuit for changing resonant frequency, for making the transistor circuit of whole circuit oscillation, for meeting terminating circuit and first, second match circuit of oscillating condition, described load circuit connects described transistor circuit through described first match circuit, and described transistor circuit connects described terminating circuit through described second match circuit.It is the voltage controlled oscillator of any one frequency in C-band that the present invention can realize mid frequency, and circuit design structure is simple, and cost is relatively low, the highest to requirement on machining accuracy, has higher cost performance；The most also there is low, the feature such as tuning range width, the linearity are good, output is high, band internal power is smooth of making an uproar mutually.

Description

A C-band voltage-controlled oscillator

technical field

The invention relates to a voltage-controlled oscillator (VCO for short), in particular to a C-band voltage-controlled oscillator, which belongs to the technical field of microwave communication.

Background technique

With the rapid development of the communication field, the requirements for electronic equipment are getting higher and higher, and the voltage-controlled oscillator is one of the very important components in the radio frequency communication system. A voltage-controlled oscillator is an oscillating circuit whose output frequency corresponds to the input control voltage, that is, the output frequency is a function of the input signal voltage. It is mainly used in phase-locked loops and frequency synthesizers to achieve an accurate reference frequency, which is critical to the performance of communication systems.

At present, there are many units researching and producing integrated voltage-controlled oscillator VCO at home and abroad. The foreign manufacturers mainly include Crystek Corporation, RF Micro Devices Inc, etc. The VCO produced by them has superior performance, but the price is also high, such as Crystek Corporation's CVCO55BH-4100 -4300, frequency range 4100~4300MHz, phase noise -113dBc/Hz@100kHz, wholesale price at least $30. It can be seen from the literature published by representative domestic scientific research units, such as the Institute of Microelectronics of the Chinese Academy of Sciences, the State Key Laboratory of Application-Specific Integrated Circuits and Systems of Fudan University, and the Institute of Radio Frequency and Optoelectronic Integrated Circuits of Southeast University, etc., that domestic C-band In the design and implementation of VCO, the 0.18μm CMOS process is often used. The phase noise at 1MHz frequency offset can often reach -110dBc/Hz, and the performance can reach below -120dBc/Hz, but there are also complicated design and high cost. High problem, cost performance is not high.

Contents of the invention

The technical problem to be solved by the present invention is to provide a C-band voltage-controlled oscillator with simple circuit structure, low cost, low requirement on machining accuracy and high cost performance.

The present invention adopts the following technical solutions for solving the problems of the technologies described above:

A C-band voltage-controlled oscillator, including a load circuit for changing the resonant frequency, a transistor circuit for oscillating the entire circuit, a terminal circuit for satisfying oscillation conditions, and first and second matching circuits, the load circuit The transistor circuit is connected to the transistor circuit via the first matching circuit, and the transistor circuit is connected to the terminal circuit via the second matching circuit; the transistor circuit includes a transistor, first to eighth capacitors, and first to second resistors , the first to the third microstrip line, the first to the second microstrip stub line, the first to the second DC power supply, one end of the first capacitor, the drain of the transistor and one end of the first microstrip line Point connection, the other end of the first microstrip line, the first microstrip stub line and one end of the first resistor are connected at the same point, the other end of the first resistor is connected to the positive pole of the first DC power supply, the sixth, seventh, The eighth capacitor is respectively connected in parallel to the positive and negative ends of the first DC power supply; the gate of the transistor is grounded through the second microstrip line; the second capacitor, the source of the transistor and one end of the third microstrip line are connected at a common point, The other end of the third microstrip line, the second microstrip stub line, and one end of the second resistor are connected at the same point, and the other end of the second resistor is connected to the positive pole of the second DC power supply, and the third, fourth, and fifth capacitors are respectively connected in parallel to the positive and negative poles of the second DC power supply; the negative poles of the first and second DC power supplies are both grounded; the load circuit includes first to second varactor diodes, ninth to twelfth capacitors, fourth to The sixth microstrip line, the third microstrip stub line, the third DC power supply, one end of the ninth capacitor, the cathode of the first varactor diode, the cathode of the second varactor diode and one end of the fourth microstrip line Common point connection, the other end of the fourth microstrip line, the third microstrip stub line and the positive pole of the third DC power supply are connected at the same point, and the tenth, eleventh, and twelfth capacitors are respectively connected in parallel to the third DC power supply At the positive and negative ends, the anode of the first varactor diode is grounded through the fifth microstrip line, the anode of the second varactor diode is grounded through the sixth microstrip line, and the negative pole of the third DC power supply is grounded.

Further, the terminal circuit includes a resistor with a value of 50Ω.

Further, the first matching circuit includes a seventh microstrip line, a grounded oscillator port connected to the other end of the ninth capacitor, and the seventh microstrip line, the other end of the first capacitor and the grounded oscillator port are connected at a common point three-port connector.

Further, the second matching circuit includes an eighth microstrip line connected to the second capacitor.

Preferably, the transistor is a BFP640-NPN silicon germanium RF transistor.

Preferably, the varactor is an SMV2019-079 silicon hyperabrupt junction varactor.

Compared with the prior art, the present invention adopts the above technical scheme and has the following beneficial effects: a voltage-controlled oscillator whose center frequency is any frequency point in the C-band can be realized, the circuit design structure is simple, the cost is low, and the processing accuracy is not required. High, with high cost performance; in addition, it has the characteristics of low phase noise, wide tuning range, good linearity, high output power, and flat power in the band.

Description of drawings

Fig. 1 is a functional block diagram of a C-band voltage-controlled oscillator of the present invention.

Fig. 2 is an overall circuit diagram of a C-band voltage-controlled oscillator of the present invention.

Among them: C1~C12 are capacitors, R1, R2, and Term1 are resistors, TL1~TL8 are microstrip lines, Tee1~Tee6 are three-port connectors, Stub1~Stub3 are microstrip stubs, Cros1 is a four-port connector, Osc1 is the grounded oscillator port, SMV2019-1~2 are varactor diodes, X1 is a transistor, SRC1~SRC3 are DC power supplies, V1~V3 are microstrip grounding holes, and Stub1~Stub3 are microstrip stubs.

Fig. 3 is a transient simulation start-up diagram of the present invention.

Fig. 4 is a harmonic balance simulation-frequency modulation linearity simulation diagram of the present invention.

Fig. 5 is a harmonic balance simulation of the present invention - a graph of output power varying with output frequency.

Fig. 6 is a harmonic balance simulation of the present invention - a simulation diagram of various harmonics.

Fig. 7 is a harmonic balance simulation-phase noise simulation diagram of the present invention.

detailed description

Embodiments of the present invention are described in detail below, examples of which are shown in the drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the figures are exemplary only for explaining the present invention and should not be construed as limiting the present invention.

As shown in Figure 1, a C-band voltage-controlled oscillator includes a load circuit, a transistor circuit, a terminal circuit, and first and second matching circuits. The load circuit is connected to the transistor circuit through the first matching circuit, and the transistor circuit is connected to the transistor circuit through the second matching circuit. Connect the terminal circuit, the load current changes the capacitance of the varactor diode through the change of the voltage, thereby changing the frequency; the transistor circuit mainly controls the entire circuit through the voltage control of the field effect tube, and is determined by setting the static operating point of the field effect tube S parameter, so as to determine the stability coefficient of the transistor to judge the oscillation condition that the transistor meets; the main requirement of the terminal circuit is to be able to make the voltage reflection coefficient of the input port |ΓIN|>1, so as to achieve the oscillation condition.

As shown in Figure 2 is the overall circuit diagram of a C-band voltage-controlled oscillator of the present invention, the transistor circuit includes transistor X1, capacitors C1~C8, resistors R1, R2, microstrip lines TL1~TL3, three-port connector Tee1~ Tee4, microstrip stubs Stub1~Stub2, DC power supply SRC1~SRC2, microstrip grounding hole V1, C1 is connected to the drain of transistor X1 through Tee1, the third port of Tee1 is connected to one end of R1 through TL1 and Tee3, and the The other end is connected to the positive pole of SRC1, C6, C7, and C8 are respectively connected in parallel to the positive and negative poles of SRC1, the third port of Tee3 is connected to Stub1; the gate of transistor X1 is grounded through TL2 and V1; the source of transistor X1 is connected through Tee2 C2, the third port of Tee2 is connected to one end of R2 via TL3 and Tee4, the other end of R2 is connected to the positive pole of SRC2, C3, C4, and C5 are respectively connected in parallel to the positive and negative ends of SRC2, and the third port of Tee4 is connected to Stub2; SRC1 Both negative poles of SRC2 and SRC2 are grounded.

The load circuit includes the first~second varactor diodes SMV2019-1~2, capacitors C9~C12, microstrip lines TL4~TL6, three-port connector Tee5, microstrip stub Stub3, DC power supply SRC3, microstrip grounding circle Holes V2~V3, four-port connector Cros1, the cathode of SMV2019-1 and the cathode of SMV2019-2 are respectively connected to two opposite ports of Cros1, the anode of SMV2019-1 is grounded through TL5 and V2, the anode of SMV2019-2 is grounded through TL6 and V3 is grounded; the third port of Cros1 is connected to C9; the fourth port of Cros1 is connected to the positive pole of SRC3 through TL4 and Tee5, C10, C11, and C12 are respectively connected in parallel to the positive and negative ends of SRC3, and the third port of Tee5 is connected to Stub3, SRC3 The negative pole is grounded.

The terminal circuit is connected to a 50Ω resistor through a quarter-wavelength high-impedance line, and the design mainly requires that the voltage reflection coefficient of the input port |ΓIN|>1; the first matching circuit includes Tee6 connected to C1, and Tee6 The second port of Tee6 is connected to TL7, the ground oscillator port Osc1 is connected to the third port of Tee6, and the other end of Osc1 is connected to C9; the second matching circuit includes TL8 connected to C2.

For the selection of transistors, select RF transistors with low 1/f noise, which can work in low frequency and intermediate frequency regions, and have low noise characteristics in the working frequency band. Based on the above considerations, the present invention selects the BFP640-NPN silicon-germanium RF transistor of Infineon Company. The best noise of this transistor is better than 1dB in the 3-5GHz frequency range, and the cut-off frequency reaches 70GHz, which fully meets the requirements of an oscillator tube.

In addition, the SMV2019-079 silicon hyperabrupt junction varactor diode of SKYWORKS is selected as the varactor diode used in the present invention. The varactor diode has a small series resistance and a large varactor ratio. Two identical varactor diodes are installed in the circuit to form an anti-series form. In this structure, since the voltage direction of the radio frequency signal applied to the two varactor diodes is opposite, when the radio frequency signal makes a varactor diode When the equivalent capacitance increases, the equivalent capacitance of the other varactor will decrease, so that the influence of the radio frequency signal on the equivalent capacitance of the varactor can be suppressed.

The overall circuit is to connect the above-mentioned varactor diode tuning circuit, transistor DC bias circuit, and terminal circuit through the first and second matching circuits. The microstrip line in the circuit is mainly used to match the varactor diode tuning circuit and transistor DC bias circuit to meet the start-up conditions of the voltage-controlled oscillator. In addition, for the selection of capacitors and resistors, in addition to meeting the withstand voltage and power requirements, they must also be selected according to their functions in the circuit. For charging resonant devices and capacitors in high-frequency paths, it is necessary to choose devices with small packages and high Q values to reduce parasitic parameters and loss capacitors; for DC blocking capacitors, its loss should be taken into consideration, and large capacitance loss cannot be selected. For large capacitors, of course, you can’t choose a capacitor with too small capacitance; for resistors, the small package, resistance value and power can meet the requirements.

As shown in Figure 3, it is a transient simulation start-up diagram of the present invention, the horizontal axis represents time/nanosecond, and the vertical axis represents output voltage/volt, wherein m1 represents that when the time is 25.73 nanoseconds, the output voltage is 1.336 volts, m2 means that when the time is 38.90 nanoseconds, the output voltage is 1.332 volts. The simulation results show that the voltage-controlled oscillator can oscillate stably and the oscillation time is short (about 6ns).

As shown in Figure 4, it is the harmonic balance simulation-frequency modulation linearity simulation diagram of the present invention, the horizontal axis represents the tuning voltage/volt, and the vertical axis represents the frequency modulation linearity/Hz, wherein m1 represents when the tuning voltage is 1.000 volts, the frequency modulation The linearity is 4.524GHz, ind Delta represents the voltage difference from m2 to m1 is 9.000 volts, dep Delta represents the frequency difference from m2 to m1 is 235.5MHz, the dotted line in the figure is the frequency modulation linearity curve, and the straight line is used to calculate the linearity It can be seen that when the tuning voltage is 1~10V, the frequency modulation linearity is better, and the calculated frequency modulation linearity is better than 3%.

As shown in Figure 5, it is the graph of the harmonic balance simulation of the present invention-output power changing with the output frequency, the horizontal axis represents the output frequency/Hz, and the vertical axis represents the output power/decibel milliwatt, wherein m represents when the output frequency is When the output frequency is 4.572GHz, the output power is 11.98dBm, and m4 means that when the output frequency is 4.760GHz, the output power is 11.687dBm. With the change of the output frequency, the output power of the VCO does not change much, which fully meets the requirements of practical applications.

As shown in Figure 6, it is the harmonic balance simulation of the present invention-each harmonic simulation diagram, the horizontal axis represents the harmonic order/order, and the vertical axis represents power/decibel milliwatt, wherein m1 represents when the harmonic order is 1 , the power is 11.950 dBm, and the simulation results show that the second harmonic is lower than the fundamental.

As shown in Figure 7, it is the harmonic balance simulation-phase noise simulation diagram of the present invention, the horizontal axis represents the noise frequency/MHz, and the vertical axis represents the phase noise/dBc, wherein m represents when the offset center frequency is 100.0kHz, the phase The noise reaches -94.51dBc/Hz, and m3 means that when the offset center frequency is 1.000MHz, the phase noise reaches -114.7dBc/Hz.

The simulation results from Figure 3 to Figure 7 show that the phase noise of the VCO at the center frequency of 4.64GHz is -95.4dBc/Hz, and when the tuning voltage changes from 1-10V, the frequency range is 235 MHz, and the frequency modulation linearity is better than 3%, and the output The maximum power can reach 11.65dBm, and the in-band power flatness is ±0.2 dBm. In summary, the design of a C-band voltage-controlled oscillator has been verified.

The above embodiments are only to illustrate the technical ideas of the present invention, and can not limit the protection scope of the present invention with this. All technical ideas proposed in accordance with the present invention, any changes made on the basis of technical solutions, all fall within the protection scope of the present invention. Inside.

Claims (7)

1. a C-band voltage controlled oscillator, it is characterised in that: include the load circuit for changing resonant frequency, whole for making The transistor circuit of individual circuit oscillation, for meeting terminating circuit and first, second match circuit of oscillating condition, described negative Carrying circuit and connect described transistor circuit through described first match circuit, described transistor circuit is through described second match circuit even Connect described terminating circuit；

Described transistor circuit include transistor, the first ~ the 8th electric capacity, the first ~ the second resistance, the first ~ the 3rd microstrip line, first ~ the second microstrip stubs, the first ~ the second DC source, described one end of first electric capacity, the drain electrode of transistor and the first microstrip line One end concurrent connect, one end concurrent of the other end of the first microstrip line, the first microstrip stubs and the first resistance connects, first The other end of resistance connects the positive pole of the first DC source, and the six, the seven, the 8th electric capacity are connected in parallel on the first DC source respectively Positive and negative end；The grid of transistor is through the second microstrip line ground connection；Second electric capacity, the source electrode of transistor and the one of the 3rd microstrip line End concurrent connects, and one end concurrent of the other end of the 3rd microstrip line, the second microstrip stubs and the second resistance connects, the second resistance The other end connect the positive pole of the second DC source, the three, the four, the 5th electric capacity are connected in parallel on the positive and negative of the second DC source respectively Two ends, pole；The equal ground connection of negative pole of first, second DC source；

Described load circuit include the first ~ the second varactor, the 9th ~ the 12nd electric capacity, the 4th ~ the 6th microstrip line, the 3rd Microstrip stubs, the 3rd DC source, one end of described 9th electric capacity, the negative electrode of the first varactor, the second transfiguration two pole The negative electrode of pipe and one end concurrent of the 4th microstrip line connect, and the other end of the 4th microstrip line, the 3rd microstrip stubs and the 3rd are straight The positive pole concurrent of stream power supply connects, the ten, the 11st, the 12nd electric capacity be connected in parallel on the both positive and negative polarity two of the 3rd DC source respectively End, the anode of the first varactor through the 5th microstrip line ground connection, the anode of the second varactor through the 6th microstrip line ground connection, The minus earth of the 3rd DC source.

2. C-band voltage controlled oscillator as claimed in claim 1, it is characterised in that: described terminating circuit includes a resistance.

3. C-band voltage controlled oscillator as claimed in claim 2, it is characterised in that: described resistance sizes is 50 Ω.

4. C-band voltage controlled oscillator as described in any one of claim 1-3, it is characterised in that: described first match circuit includes Ground connection oscillator port that 7th microstrip line and the 9th electric capacity other end connect, make the 7th microstrip line, the other end of the first electric capacity Three port connectors connected with ground connection oscillator port concurrent.

5. C-band voltage controlled oscillator as described in any one of claim 1-3, it is characterised in that: described second match circuit includes The 8th microstrip line being connected with described second electric capacity.

6. C-band voltage controlled oscillator as described in any one of claim 1-3, it is characterised in that: described transistor is BFP640- NPN type SiGe type RF transistor.

7. C-band voltage controlled oscillator as described in any one of claim 1-3, it is characterised in that: described varactor is SMV2019-079 silicon super sudden change junction varactor.