A kind of X-band voltage controlled oscillator
Technical field
The invention belongs to electronic technology field, relate to voltage controlled oscillator, especially a kind of X-band voltage controlled oscillator based on BZN dielectric film voltage controlled capacitor and U-shaped coupled resonators.
Background technology
Frequency source is the critical component in the electronic system, at microwave communication, radar system, electronic countermeasures, guidance, instrument and instrument measurement, and all has widely in the field such as biomedical engineering and uses.In all wireless systems, the frequency source part that more is absolutely necessary plays a part very importantly to whole system, therefore often be called as in " heart " of electronic system.Along with the development of technology such as radar, electronic countermeasures, satellite communication, increasingly high requirement has been proposed also for the indexs such as spectral purity, frequency stability, frequency resolution and bandwidth of operation of frequency source.
In the microwave frequency source, voltage controlled oscillator (VCO) is its core building block, in order to produce the controlled microwave oscillation signal of frequency.The tuning characteristic of VCO and phase noise have directly determined the quality of each item performance index of frequency source.In order to make the frequency-tunable of VCO, just need in the VCO circuit, add electric tuning or magnetic tuning device, and the noise that loss produced of tuned cell is the important component part that causes in the VCO phase noise.
The main tunable devices that adopts has semiconductor variable capacitance diode, ferroelectric capacitor, micro electromechanical structure (MEMS) electric capacity, mechanical varactor etc. among the VCO at present, and table 1 is seen in the contrast of their various aspects of performance.Semiconductor variable capacitance diode is compared with mechanical capacitance with MEMS electric capacity with ferroelectric capacitor, and adjustable rate is big, and electric speed governing degree is high, can be competent in broadband, victory up to octave to become the frequency hopping source, and its application is quite extensive.However, the varactor radio frequency loss is relatively large, and particularly at microwave and millimeter wave frequency band, its loss further increases, and causes that the phase noise of VCO circuit worsens.
The performance of table 1 variable capacitance diode, ferroelectric capacitor, MEMS electric capacity and mechanical capacitance relatively
Parameter |
Semiconductor variable capacitance diode |
Ferroelectric capacitor |
MEMS electric capacity |
The machinery varactor |
Adjustable rate |
High (2~5: 1) |
High (2~3: 1) |
Low by (<1.5: 1) |
Moderate |
Radio frequency loss (Q) |
In (Q<60) |
In (Q<40 are present) |
Good (Q<200) |
Good |
Control voltage |
<10V (single-stage) |
10~90V (bipolar) |
50~100V (bipolar) |
- |
Modulating speed |
Hurry up |
Hurry up |
Slowly |
Slowly |
The power bearing capacity |
Difference |
Relevant with voltage |
Excellent |
Excellent |
Cost |
Moderate~height |
Low |
High |
Low |
BZN (bismuth zinc niobate) film is one of current electric tuning material of new generation of studying; BZN dielectric film voltage controlled capacitor is compared with conventional semiconductor variable capacitance diode; The loss of BZN dielectric film voltage controlled capacitor under microwave frequency is lower; Q value (quality factor) is higher, and the tunable capacitor that therefore adopts the BZN film to make replaces BZN dielectric film voltage controlled capacitor and will the phase noise of VCO be made moderate progress.
Summary of the invention
The present invention provides a kind of X-band voltage controlled oscillator, and it is tuning that this voltage controlled oscillator adopts BZN dielectric film voltage controlled capacitor that circuit is carried out, and tuning bandwidth is greater than 100MHz; Adopt the resonant tank of half-wavelength U type microstrip line coupled resonators simultaneously, reduced the phase noise of voltage controlled oscillator as VCO.
Technical scheme of the present invention is following:
A kind of X-band voltage controlled oscillator, as shown in Figure 5, be made on the alumina ceramic substrate, comprise a half-wavelength U type microstrip line coupled resonators, a BZN dielectric film voltage controlled capacitor C
vWith a gaas fet.Half-wavelength U type microstrip line coupled resonators by a half-wavelength U type mini strip line resonator with constitute with the microstrip line of two parallel couplings of side of half-wavelength U type mini strip line resonator respectively.In the half-wavelength U type microstrip line coupled resonators, with an end of the microstrip line 20 of a parallel coupling of side of half-wavelength U type mini strip line resonator through BZN dielectric film voltage controlled capacitor C
vGround connection; With an end of the microstrip line 8 of the parallel coupling of another side of half-wavelength U type mini strip line resonator through behind first little band connecting line 9 again through build-out resistor R1 ground connection, the other end is successively through connecing the source S of gaas fet behind the second little band connecting line 7, the first capacitance C2 and the 3rd little band connecting line 6.The grid G of gaas fet is through phase adjusted microstrip line 4 ground connection, and the drain D of gaas fet is successively through linking to each other with output microstrip line 1 behind the little band connecting line of the first little band high resistant line the 3, the 4th 2, the second capacitance C1.BZN dielectric film voltage controlled capacitor C
vVoltage-controlled signal put on the intermediate point with the microstrip line 20 of a parallel coupling of side of half-wavelength U type mini strip line resonator through second little band high resistant line 22, have the low pass filter that constitutes by the first shunt capacitance C5 and first fan-shaped offset of microstrip open circuit minor matters 23 on second little band high resistant line 22.The drain D bias voltage of gaas fet puts on the 4th little band connecting line 2 through the 3rd little band high resistant line 11, has the low pass filter that is made up of the second shunt capacitance C3 and second fan-shaped offset of microstrip open circuit minor matters 12 on the 3rd little band high resistant line 11.The source S bias voltage of gaas fet puts on the 3rd little band connecting line 6 through the 4th little band high resistant line 14, has the low pass filter that is made up of the 3rd shunt capacitance C4 and the 3rd fan-shaped offset of microstrip open circuit minor matters 15 on the 4th little band high resistant line 14.
High Q resonant tank is one of important measures that reduce the VCO phase noise, and the present invention adopts the resonant tank of half-wavelength U type mini strip line resonator as VCO, and shown in Fig. 1 (a), Fig. 1 (b) is the lumped parameter equivalent circuit of half-wavelength U type resonator.C wherein
e, L
e, G
eCharacterize half-wavelength U type resonator respectively in resonance frequency omega
0Neighbouring electric capacity, inductance and conductance property, and the resonance frequency of half-wavelength U type resonator
For the resonance frequency that makes resonator can be regulated, the present invention utilizes BZN dielectric film voltage controlled capacitor C in a side of half-wavelength U type resonator
vCarry out the energy coupling through one section parallel coupled
line 20 and half-wavelength U type resonator, realize the tuning of resonance frequency with this; Opposite side at half-wavelength U type resonator is coupled to 50 ohm microstrip through another section parallel coupled
line 8, sets up with negative resistance circuit and gets in touch, and finally realizes the tuning of VCO frequency of oscillation.
U type coupled resonators structure and equivalent electric circuit thereof utilize the power coupled relation of the equivalent parallel coupled line of transformer shown in Fig. 2 (a), then load BZN dielectric film voltage controlled capacitor C
vAfter U type coupled resonators can be converted into the equivalent electric circuit shown in Fig. 2 (b).Use L
tExpression BZN dielectric film voltage controlled capacitor C
vBe presented on the inductance at place, coupling slit after the microstrip line impedance conversion, then half-wavelength U type resonator loads BZN dielectric film voltage controlled capacitor C
vAfter equivalent inductance be expressed as L
Et, and:
L wherein
t'=L
t/ N
v 2, N
vTransformation ratio for Equivalent Transformer.Therefore, the natural resonance frequency of half-wavelength U type resonator does
Shown in following formula, along with BZN dielectric film voltage controlled capacitor C
vWith half-wavelength U type coupled resonators transformation ratio N
vVariation, the resonance frequency of half-wavelength U type resonator also and then changes, thereby makes half-wavelength U type resonator at BZN dielectric film voltage controlled capacitor C
vWith half-wavelength U type coupled resonators transformation ratio N
vExcursion in obtain certain resonant bandwidth.BZN dielectric film voltage controlled capacitor C
vVariation be that variation through its control voltage realizes and half-wavelength U type coupled resonators transformation ratio N
vVariation then can realize that the adjusting of the two reaches the required bandwidth requirement of whole X-band voltage controlled oscillator through this through the slit of regulating between half-wavelength U type resonator and the parallel coupled line 20.
Biasing and tuning circuit adopt high low-impedance line to realize chokes.The biasing circuit chokes are made up of fan-shaped offset of microstrip open circuit minor matters 12,15 and high impedance microstrip line 11,14, are 1/4 operation wavelength.The tuning circuit chokes are made up of with high impedance microstrip line 22 fan-shaped offset of microstrip open circuit minor matters 23, are 1/4 operation wavelength.
To sum up, X-band voltage controlled oscillator provided by the invention adopts low-loss alumina ceramic substrate and microstrip line integrated technique, has little, the lightweight characteristics of volume; It is tuning to adopt BZN dielectric film voltage controlled capacitor that circuit is carried out, and tuning bandwidth is greater than 100MHz; Adopt the resonant tank of half-wavelength U type microstrip line coupled resonators simultaneously, reduced the phase noise of voltage controlled oscillator as VCO.
Description of drawings
Fig. 1 is half-wavelength U type mini strip line resonator structure and equivalent electric circuit thereof.
Fig. 2 is half-wavelength U type microstrip line coupled resonators structure and equivalent electric circuit thereof.
Fig. 3 is the physical dimension signal of U type microstrip line coupled resonators in the specific embodiment of the invention.
Fig. 4 is in the X-band voltage controlled oscillator provided by the invention, the connection of gaas fet signal.
Fig. 5 is the circuit structure signal of X-band voltage controlled oscillator provided by the invention.
Embodiment
A kind of X-band voltage controlled oscillator; As shown in Figure 5; Be made in dielectric constant and be 9.9, thickness is that 0.635mm, loss tangent are on 0.0002 the alumina ceramic substrate, to comprise a half-wavelength U type microstrip line coupled resonators, a BZN dielectric film voltage controlled capacitor C
vWith a gaas fet.Half-wavelength U type microstrip line coupled resonators by a half-wavelength U type mini strip line resonator with constitute with the microstrip line of two parallel couplings of side of half-wavelength U type mini strip line resonator respectively.In the half-wavelength U type microstrip line coupled resonators, with an end of the microstrip line 20 of a parallel coupling of side of half-wavelength U type mini strip line resonator through BZN dielectric film voltage controlled capacitor C
vGround connection; With an end of the microstrip line 8 of the parallel coupling of another side of half-wavelength U type mini strip line resonator through behind first little band connecting line 9 again through build-out resistor R1 ground connection, the other end is successively through connecing the source S of gaas fet behind the second little band connecting line 7, the first capacitance C2 and the 3rd little band connecting line 6.The grid G of gaas fet is through phase adjusted microstrip line 4 ground connection, and the drain D of gaas fet is successively through linking to each other with output microstrip line 1 behind the little band connecting line of the first little band high resistant line the 3, the 4th 2, the second capacitance C1.BZN dielectric film voltage controlled capacitor C
vVoltage-controlled signal put on the intermediate point with the microstrip line 20 of a parallel coupling of side of half-wavelength U type mini strip line resonator through second little band high resistant line 22, have the low pass filter that constitutes by the first shunt capacitance C5 and first fan-shaped offset of microstrip open circuit minor matters 23 on second little band high resistant line 22.The drain D bias voltage of gaas fet puts on the 4th little band connecting line 2 through the 3rd little band high resistant line 11, has the low pass filter that is made up of the second shunt capacitance C3 and second fan-shaped offset of microstrip open circuit minor matters 12 on the 3rd little band high resistant line 11.The source S bias voltage of gaas fet puts on the 3rd little band connecting line 6 through the 4th little band high resistant line 14, has the low pass filter that is made up of the 3rd shunt capacitance C4 and the 3rd fan-shaped offset of microstrip open circuit minor matters 15 on the 4th little band high resistant line 14.
In the such scheme:
Said half-wavelength U type microstrip line coupled resonators is as shown in Figure 3; Wherein the width of a side of half-wavelength U type mini strip line resonator is that 0.62mm, length are 1.98mm; The width of another side is that 0.4mm, length are 1.98mm; The base width is 0.62mm; Two sides are at a distance of 1.48mm, are that the width of the microstrip line 8 of 0.2mm is that 0.62mm, length are 1.98mm with a parallel coupling of side, coupling spacing, are that the width of the microstrip line 20 of 0.1mm is that 0.4mm, length are 1.98mm with the parallel coupling of another side, coupling spacing;
The model of said gaas fet is CF001, and die-size is 400um * 250um; The width of said output microstrip line 1, first little band connecting line 9, second little band connecting line the 7, the 3rd little band connecting line the 6, the 4th little band connecting line 2 is 0.62mm; The width of said first little band high resistant line 3 is that 100um, length are 1.6mm; The width of said phase adjusted microstrip line 4 is that 100um, length are 1.3mm; The width of said second little band high resistant line the 22, the 3rd little band high resistant line the 11 and the 4th little band high resistant line 14 is that 0.1mm, length are 1/4 wavelength; The resistance of said build-out resistor R1 is 50 ohm; The capacitance of said shunt capacitance (C3, C4, C5) is 20pf; The capacitance of said capacitance (C1, C2) is 20pf; Said BZN dielectric film voltage controlled capacitor C
vThe capacitance variation scope be 0.24~1.2pf; The fan-shaped angle of said first fan-shaped offset of microstrip open circuit minor matters 23, second fan-shaped offset of microstrip open circuit minor matters 12, the 3rd fan-shaped offset of microstrip open circuit minor matters 15 should be big as far as possible, and the line radius is 3.4mm.
The technical indicator of above-mentioned X-band VCO is through actual measurement, and its output frequency is 9.6GHz~9.77GHz, and bandwidth is 170MHz, and the phase noise coefficient is less than-115dBc.