CN201550100U - Frequency synthesis system based on varactor diode - Google Patents
Frequency synthesis system based on varactor diode Download PDFInfo
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- CN201550100U CN201550100U CN2009201443872U CN200920144387U CN201550100U CN 201550100 U CN201550100 U CN 201550100U CN 2009201443872 U CN2009201443872 U CN 2009201443872U CN 200920144387 U CN200920144387 U CN 200920144387U CN 201550100 U CN201550100 U CN 201550100U
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- capacitance diode
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Abstract
The utility model discloses a frequency synthesis system based on a varactor diode, which comprises a phase lock loop circuit, a passive loop filter, an oscillating circuit and a power divider, wherein the phase lock loop circuit is used for receiving a first frequency of a first input signal and a second frequency of a second input signal, comparing the phase positions of the first input signal and the second input signal and converting the comparison result into an electric current signal; the passive loop filter is connected with the phase lock loop circuit and converts the electric current signal into a control voltage; the oscillating circuit is connected with the passive loop filter and has a varactor diode which is controlled by the control voltage to change the second frequency of the second input signal; and the power divider is connected with the output terminal of the oscillating circuit and the second input terminal of the phase lock loop circuit. The frequency synthesis system has the advantages of small volume, low cost, high stability and reliable circuit performance; can ensure the quality of video image transmission; and can be widely applied to monitoring systems in the complex environment and in the dangerous place.
Description
Technical field the utility model relates to frequency synthesis technique, relates in particular to a kind of frequency synthesizer system based on variable capacitance diode.
Background technology is along with the open applications of 5.2GHz to 5.8GHz high-frequency band, and wireless transmission usually is used for monitoring or video transmission, thereby the output result of frequency synthesis can directly have influence on the transmission quality of wireless transmitting system.Yet traditional frequency synthesizer price is higher, and volume is bigger than normal, is difficult to satisfy user's designing requirement in narrow and small application scenario, some space.
On the other hand, use crystal oscillator to realize the circuit of frequency synthesis, though simplicity of design, reliable and stable, under the condition of a plurality of frequency bands of needs, the kind of crystal and quantity will correspondingly increase, thereby can't realize miniaturization and modularization.
Design specific to oscillator, because nonlinear circuit can't adopt the analysis theories of linear system to describe comprehensively, and the complex feedback mechanism of active device inside can not be described on the whole at all based on the linear circuit model of small-signal, thereby the pierce circuit design cycle of the prior art is longer, and design cost is higher.Though some manufacturer does the frequency range of oscillator very wide, the phase noise index is good, this broadband cost of manufacture height, and tuned speed is slow, is unfavorable for producing in batches.And the high Q element of adding can cause the bandwidth of oscillator to narrow down.
The summary of the invention the purpose of this utility model is to provide a kind of with low cost, miniaturization, and the reliable and stable frequency synthesizer system based on variable capacitance diode of circuit performance.
For achieving the above object, the technical scheme taked of the utility model is:
A kind of frequency synthesizer system based on variable capacitance diode comprises (a) phase lock circuitry, which comprises at least: first input end is used to receive the first frequency from first input signal of crystal oscillator; Second input is used to receive the second frequency of second input signal; And phase locking unit, compare first input signal and second phase of input signals, and convert comparative result to current signal; (b) passive ring filter electrically connects with the phase locking unit of phase lock circuitry, and converts current signal to control voltage; (c) oscillating circuit electrically connects with the passive ring filter, and this oscillating circuit has a variable capacitance diode, and controls variable capacitance diode to change the second frequency of second input signal by control voltage; And (d) power splitter, electrically connect with the output of oscillating circuit and second input of phase lock circuitry.
Wherein, oscillating circuit adopts carat bold and vigorous formula (Clapp) negative resistance oscillation circuit.
Wherein, an end of variable capacitance diode is electrically connected to the output of passive ring filter, and the other end is electrically connected to earthed voltage.Preferably, variable capacitance diode and inductance element, capacity cell are formed resonant tank, change second frequency thereby control voltage changes the capacitance of variable capacitance diode.
Wherein, the passive ring filter is a third-order low-pass filter.And third-order low-pass filter is composed in series by second order filter and extension filter.
The above-mentioned frequency synthesizer system that the utility model provides based on variable capacitance diode, utilize the phase locking unit in the phase lock circuitry can generate the lower frequency of phase noise, the passive ring filter can reduce volume and reduce noise, and oscillating circuit can make circuit output impedance low, thereby reduces the influence of load variations to frequency of oscillation.In addition, electronic component in passive ring filter, oscillating circuit and the power splitter all adopts the less surface mount elements of packing forms, therefore not only volume is little, with low cost, stability is high for whole frequency synthesizer system, and circuit performance is reliable, owing to guaranteed the quality of transmission of video images in the design, can be widely used in the surveillance of complex environment and dangerous situation, to replace the frequency synthesizer that price is higher, volume is bigger than normal in the prior art.
Description of drawings Fig. 1 illustrates the circuit theory schematic diagram according to frequency synthesizer system of the present utility model;
Fig. 2 illustrates the circuit diagram of the passive ring filter of frequency synthesizer system as shown in Figure 1.
Embodiment is described in further detail embodiment of the present utility model with reference to the accompanying drawings.
Before the description that launches the utility model embodiment, briefly introduce operation principle about variable capacitance diode.Variable capacitance diode VCD (Variable-Capacitance Diode) utilizes reverse biased to change the particular semiconductor device of PN junction capacitance.Variable capacitance diode adopts the low resistance hyperabrupt junction varactor, hyperabrupt junction varactor has the bigger ratio of varying capacitance, coverage because the junction capacitance of variable capacitance diode can change with the reverse biased that adds, is often used as frequency modulation, frequency sweep and phase control than broad.
Fig. 1 illustrates the circuit theory schematic diagram according to frequency synthesizer system of the present utility model.With reference to Fig. 1, this frequency synthesizer system comprises: phase lock circuitry which comprises at least: first input end is used to receive the first frequency from first input signal of crystal oscillator 18; Second input is used to receive the second frequency of second input signal; And phase locking unit 10, compare first input signal and second phase of input signals, and convert comparative result to current signal; Passive ring filter 12 electrically connects with the phase locking unit 10 of phase lock circuitry, and converts current signal to control voltage; Oscillating circuit 14 electrically connects with passive ring filter 12, and this oscillating circuit 14 has a variable capacitance diode V1, and controls variable capacitance diode V1 to change the second frequency of second input signal by control voltage; And power splitter 16, electrically connect with the output of oscillating circuit 14 and second input of phase lock circuitry.In addition, this frequency synthesizer system can also comprise microprocessor (as single-chip microcomputer), carries out transfer of data with phase locking unit 10.For example, single-chip microcomputer can provide latch signal LE, data-signal DATA and clock signal clk to phase locking unit 10.
The output signal of crystal oscillator 18 is connected to an input Ref of phase locking unit 10, as the first frequency of first signal; The output signal of oscillating circuit 14 is connected to another input RFin of phase locking unit 10 via power splitter 16, and as the second frequency of secondary signal, and an output VP of phase locking unit 10 is connected to passive ring filter 12.It can also be seen that from Fig. 1 passive ring filter 12 is connected with oscillating circuit 14.Phase locking unit 10 in this frequency synthesizer system can be, for example but have more than and be confined to the ADF4106 chip of ADI company.The phase place of the phase of input signals of phase locking unit 10 comparison crystal oscillators 18 and the output signal of oscillating circuit 14, and export result's phase error electric current as a comparison.This phase error electric current generates control voltage and loads on the variable capacitance diode V1 that links to each other with its output the other end ground connection of variable capacitance diode V1 after carrying out filtering through passive ring filter 12.When control voltage changed, the capacitance of the PN junction of variable capacitance diode V1 also changed thereupon.Because variable capacitance diode V1 in the oscillating circuit 14 and inductance L 1 and capacitor C 4 constitute the resonant tank of oscillating circuit, so the PN junction capacitance variations of variable capacitance diode V1 can change the second frequency of the secondary signal of oscillating circuit output.This frequency of oscillation feeds back to phase locking unit 10 through power splitter 16, thereby has formed frequency synthesizer system of the present utility model.
Below, be described further for this frequency synthesizer system.When closed loop circuit is started working, usually the frequency of oscillation that does not add when controlling voltage from the frequency of the input signal of crystal oscillator 18 and oscillating circuit 14 is inequality, owing to have intrinsic difference on the frequency between these two signals, phase difference between them also can change always, constantly changes to surpass 2 π.And phase locking unit 10 is the cycle with phase difference 2 π, and the phase error electric current of phase locking unit 10 outputs is as a result just swung in a certain scope.Under the control of this phase error electric current, the frequency of oscillation of oscillating circuit 14 also just changes within corresponding scope.If can changing to the frequency of crystal oscillator 18, the frequency of oscillation of oscillating circuit 14 equates that then this closed loop circuit might settle out on this frequency.Under this stable state, be zero from the difference on the frequency between the output signal of the input signal of crystal oscillator 18 and oscillating circuit 14, the phase difference between the two changes no longer in time, and phase error electric current at this moment is a fixed value.If input signal generation phase place or frequency change (disturb or modulate caused), by the FEEDBACK CONTROL of closed control circuit self, the frequency of oscillation of oscillating circuit 14 and phase place will be followed the tracks of the variation of this input signal.
Because the frequency of oscillation of oscillating circuit 14 is to be controlled by the control voltage that loads on variable capacitance diode V1 two ends, so oscillating circuit 14 also can be described as voltage controlled oscillator, it belongs to the voltage-frequency conversion equipment, and its frequency of oscillation is along with control voltage carries out linear change.For example, be confined to but have more than, oscillating circuit 14 can adopt carat bold and vigorous formula (Clapp) negative resistance oscillation circuit, one of its design at the active negative resistance circuit under the large-signal limit to offset load and other the positive resistance elements in the closed loop circuit.Variable capacitance diode V1 and inductance L 1, capacitor C 4 constitute resonant tank, thereby change the capacitance change frequency of oscillation of variable capacitance diode V1 with the control voltage of passive ring filter 12 outputs.Wherein capacitor C 4 can be used for regulating resonance frequency, improve the temperature variant frequency drift problem of junction capacitance of variable capacitance diode V1, the size of adjusting capacitor C 4 simultaneously can guarantee that variable capacitance diode V1 is operated in linear zone, helps accurately regulating output signal frequency and reduces nonlinear distortion.In addition, starting of oscillation active device Q1 can adopt radio frequency low-noise bipolar transistor BFP640, to reduce the phase noise of oscillating circuit, increases working band simultaneously, improves the resonant tank loaded Q.Resistance R 4 and R5 are used to regulate the quiescent point of starting of oscillation active device Q1, mainly play direct current biasing.Collector electrode at bipolar transistor BFP640 inserts a treble attenuation circuit that is composed in parallel by resistance R 6, inductance L 2 series connection backs and capacitor C 6, under the situation that does not influence direct current biasing, utilize the filtering characteristic of inductance and electric capacity, the power of output signal high band is carried out suitable decay, thereby improved the flatness of the interior output power signal of frequency band of oscillating circuit 14, guaranteed that oscillating circuit 14 has power output comparatively uniformly in whole frequency band.In addition, resistance R 7 also plays direct current biasing and the degenerative effect of voltage.The base capacity C5 of cross-over connection between transistor and earth terminal meanwhile, also carries out filtering to the direct current that is input to transistor base to the effect of base stage interchange ground connection.
It is pointed out that the junction capacitance of variable capacitance diode and controlling between the voltage is non-linear variation relation, thereby the control characteristic of oscillating circuit also is non-linear.For example, the principal element that influences the oscillator linearity is the C-V characteristic of variable capacitance diode, even select good variable capacitance diode, and the also linearity that not necessarily can obtain.So how obtain oscillator frequency-voltage curve preferably? because the capacitance the when capacitance of variable capacitance diode when voltage is low is more higher than voltage is big, thereby, if it is connected with a capacitances in series, then the electric capacity change amount at low terminal voltage place is bigger than the electric capacity change amount at high terminal voltage place, suitably the electric capacity in the selective resonance loop (promptly, the capacitor C 4 of connecting), just can carry out suitable reactance compensation, so that obtain frequency-voltage curve preferably to oscillator with variable capacitance diode V1.
Fig. 2 illustrates the circuit diagram of the passive ring filter of frequency synthesizer system as shown in Figure 1.As shown in Figure 2, passive ring filter 12 is third-order low-pass filters, and, be composed in series by second order filter 20 and extension filter 22.Wherein, second order filter 20 comprises two branch roads, that is, and and the branch road that branch road that capacitor C 1 is formed and capacitor C 2 and resistance R 1 are composed in series.Wherein, extension filter 22 is made up of resistance R 2 and capacitor C 3, is used to suppress the output ripple of phase error voltage, reduces error.More specifically, adopt the transfer function of the passive ring filter 12 of third-order low-pass filter to be expressed as:
Wherein,
τ
2=R
2C
2, τ
3=R
3C
3, and K
dBe the sensitivity of phase locking unit, K
vBe the sensitivity of voltage controlled oscillator, N is a frequency dividing ratio.Signal S1 among Fig. 2 represents the phase error voltage from phase locking unit 10, and signal S2 represents the control voltage of passive ring filter 12 outputs.
In frequency synthesizer system of the present utility model, adopted high performance electric current phase discriminator in the phase locking unit 10, can generate the lower frequency of phase noise.In addition, oscillating circuit 12 adopts carat bold and vigorous formula (Clapp) oscillating structures, makes circuit output impedance low, can be directly and the circuits cascading of back, reduce the influence of load variations to frequency.
Above, describe embodiment of the present utility model with reference to the accompanying drawings.But those skilled in the art can understand, and under the situation that does not depart from spirit and scope of the present utility model, can also do various changes and replacement to embodiment of the present utility model.These changes and replacement all drop in the utility model claims institute restricted portion.
Claims (6)
1. the frequency synthesizer system based on variable capacitance diode is characterized in that, this frequency synthesizer system comprises:
(a) phase lock circuitry which comprises at least:
First input end is used to receive the first frequency from first input signal of crystal oscillator;
Second input is used to receive the second frequency of second input signal; And
Phase locking unit is used for comparison first input signal and second phase of input signals, and converts comparative result to current signal;
(b) passive ring filter electrically connects with the phase locking unit of phase lock circuitry, and converts current signal to control voltage;
(c) oscillating circuit electrically connects with the passive ring filter, and this oscillating circuit has a variable capacitance diode, and controls variable capacitance diode to change the second frequency of second input signal by control voltage; And
(d) power splitter electrically connects with the output of oscillating circuit and second input of phase lock circuitry.
2. frequency synthesizer system as claimed in claim 1 is characterized in that, described oscillating circuit adopts a carat bold and vigorous formula negative resistance oscillation circuit.
3. frequency synthesizer system as claimed in claim 1 is characterized in that an end of described variable capacitance diode is electrically connected to the output of passive ring filter, and the other end is electrically connected to earthed voltage.
4. frequency synthesizer system as claimed in claim 3 is characterized in that, described variable capacitance diode and inductance element, capacity cell are formed resonant tank, changes second frequency thereby control voltage changes the capacitance of variable capacitance diode.
5. frequency synthesizer system as claimed in claim 1 is characterized in that, described passive ring filter is a third-order low-pass filter.
6. frequency synthesizer system as claimed in claim 5 is characterized in that described third-order low-pass filter is composed in series by second order filter and extension filter.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2009201443872U CN201550100U (en) | 2009-12-05 | 2009-12-05 | Frequency synthesis system based on varactor diode |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2009201443872U CN201550100U (en) | 2009-12-05 | 2009-12-05 | Frequency synthesis system based on varactor diode |
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| CN201550100U true CN201550100U (en) | 2010-08-11 |
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| CN2009201443872U Expired - Fee Related CN201550100U (en) | 2009-12-05 | 2009-12-05 | Frequency synthesis system based on varactor diode |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104536284A (en) * | 2014-10-10 | 2015-04-22 | 北京空间机电研究所 | Clock management circuit of remote sensing camera |
| CN105429653A (en) * | 2015-11-26 | 2016-03-23 | 青岛盛嘉信息科技有限公司 | Sinusoidal signal generation circuit |
| CN107666285A (en) * | 2017-10-26 | 2018-02-06 | 宝鸡烽火诺信科技有限公司 | One kind miniaturization high-frequency voltage controlled oscillator |
-
2009
- 2009-12-05 CN CN2009201443872U patent/CN201550100U/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104536284A (en) * | 2014-10-10 | 2015-04-22 | 北京空间机电研究所 | Clock management circuit of remote sensing camera |
| CN105429653A (en) * | 2015-11-26 | 2016-03-23 | 青岛盛嘉信息科技有限公司 | Sinusoidal signal generation circuit |
| CN107666285A (en) * | 2017-10-26 | 2018-02-06 | 宝鸡烽火诺信科技有限公司 | One kind miniaturization high-frequency voltage controlled oscillator |
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|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| C17 | Cessation of patent right | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20100811 Termination date: 20121205 |