NL2011996C2 - Controllable oscillator circuit and method for operating such circuit. - Google Patents

Controllable oscillator circuit and method for operating such circuit. Download PDF

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Publication number
NL2011996C2
NL2011996C2 NL2011996A NL2011996A NL2011996C2 NL 2011996 C2 NL2011996 C2 NL 2011996C2 NL 2011996 A NL2011996 A NL 2011996A NL 2011996 A NL2011996 A NL 2011996A NL 2011996 C2 NL2011996 C2 NL 2011996C2
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Prior art keywords
controllable
circuit
oscillator
resonator
value
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NL2011996A
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Dutch (nl)
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Antonius Johannes Maria Montagne
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Frapinv S B V
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
    • H03B5/00—Generation of oscillations using amplifier with regenerative feedback from output to input
    • H03B5/08—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance
    • H03B5/12—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device
    • H03B5/1237—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device comprising means for varying the frequency of the generator
    • H03B5/1262—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device comprising means for varying the frequency of the generator the means comprising switched elements
    • H03B5/1265—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device comprising means for varying the frequency of the generator the means comprising switched elements switched capacitors
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
    • H03B5/00—Generation of oscillations using amplifier with regenerative feedback from output to input
    • H03B5/08—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance
    • H03B5/12—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device
    • H03B5/1206—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device using multiple transistors for amplification
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
    • H03B5/00—Generation of oscillations using amplifier with regenerative feedback from output to input
    • H03B5/08—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance
    • H03B5/12—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device
    • H03B5/1237—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device comprising means for varying the frequency of the generator
    • H03B5/124—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device comprising means for varying the frequency of the generator the means comprising a voltage dependent capacitance
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
    • H03B5/00—Generation of oscillations using amplifier with regenerative feedback from output to input
    • H03B5/08—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance
    • H03B5/12—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device
    • H03B5/1237—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device comprising means for varying the frequency of the generator
    • H03B5/1293—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device comprising means for varying the frequency of the generator having means for achieving a desired tuning characteristic, e.g. linearising the frequency characteristic across the tuning voltage range
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
    • H03L7/00—Automatic control of frequency or phase; Synchronisation
    • H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
    • H03L7/08—Details of the phase-locked loop
    • H03L7/099—Details of the phase-locked loop concerning mainly the controlled oscillator of the loop
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03J—TUNING RESONANT CIRCUITS; SELECTING RESONANT CIRCUITS
    • H03J2200/00—Indexing scheme relating to tuning resonant circuits and selecting resonant circuits
    • H03J2200/10—Tuning of a resonator by means of digitally controlled capacitor bank

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inductance-Capacitance Distribution Constants And Capacitance-Resistance Oscillators (AREA)

Description

Controllable oscillator circuit and method for operating such circuit
The present invention relates to a controllable oscillator circuit and method for operating such circuit. PLL frequency synthesizers use controlled oscillators (usually voltage-controlled oscillators or VCOs). A typical structure of a frequency synthesizer with output divider according to the state of the art is shown in figure 1. The output frequency fout is synthesized from the input frequency ƒ as:
Figure NL2011996CD00021
Alternative structures use an input divider instead of an output divider or use both input and an output dividers.
The relative acute range of such a synthesizer is defined as the relative range of the input frequencies or the relative range of the output frequencies that can be handled without changing the divider settings. It is equal to the relative tuning range of the controlled oscillator.
If an over-all frequency range needs to be completely covered, the tuning range of the controlled oscillator should at least equal the frequency difference that is obtained by changing the output divider settings by one step.
In such cases, the relative acute tuning range:
Figure NL2011996CD00022
of a controlled oscillator should at least be:
Figure NL2011996CD00023
From this it follows that PLL synthesizers, that need to have a large over-all frequency range, require either low-resolution integer dividers and VCOs with a relatively large tuning range, or high-resolution fractional dividers and VCOs with a relatively small tuning range. A small tuning range of the controlled oscillator or a low-sensitivity controlled oscillator is beneficial to the carrier to noise ratio of the synthesized output frequency. Hence, the best possible solution for a wide-range synthesizer is the one that combines an low-sensitivity or narrow-range controlled oscillator with a fractional divider.
The frequency generated by a controlled oscillator, apart from its controlling quantity, also depends on temperature, which usually puts a serious constraint to its tuning range. The relative tuning range of a controlled oscillator in a PLL loop must be large enough to compensate for the changes in its output frequency due to temperature variations.
For practical integrated circuit voltage-controlled oscillators (YCOs) this temperature requirement as well as requirements that follow from production tolerances often dominate the functional requirement for the desired actual range. As a consequence, the controlled oscillator must be designed with a sensitivity larger than desired, which imposes serious limitations to the achievable carrier to noise ratio.
Besides accepting a smaller operating frequency range and / or temperature range a known solution to is using a controlled oscillator with digital range switching. A low-noise oscillator as applied in IC technology usually comprises a positive feedback loop around a resonator and an active circuit. The active circuit compensates for the energy losses in the resonator. By doing so, it establishes sustained harmonic oscillations.
In a controlled oscillator, one of the resonator elements is realized as voltage-controlled or current-controlled element. Usually voltage-dependent capacitors or varicaps are used for this purpose. By making the control range of this element relatively small with respect to its typical value, a low-sensitivity controlled oscillator can be obtained.
Range switching can then be implemented by adding resonator elements (usually capacitors) to the resonator or removing those elements from the resonator with the aid of switches. Such a solution for a voltage-controlled oscillator is shown in figure 2.
However, switching of the range of the controlled oscillator during operation causes abrupt phase and frequency errors in the PLL synthesizer. These errors last until the synthesizer has settled to its new operating point. Such transient behaviour is unacceptable in low-noise applications.
Another solution known in the art is to use a temperature-compensated controlled oscillator, which is a controlled oscillator that has both a low-sensitivity control input and a high-sensitivity control input. The latter one is used for temperature compensation. A disadvantage of such a solution is the active state of the high-sensitivity control input during normal operation. Any noise on this input strongly decreases the carrier to noise ratio of the oscillator. In fact one seems to have a high-sensitivity controlled oscillator rather than a low-sensitivity controlled oscillator.
It is a goal of the present invention to provide a solution that takes away the above disadvantages, or at least provides a useful alternative to the state of the art. The invention thereto proposes a controllable oscillator circuit, comprising a controllable oscillator; a resonance circuit, coupled to the controllable oscillator, and comprising an inductive part, comprising one or more inductive components switched in series with respect to each other, and each parallel with a controllable resistor element; and /or a capacitive part, comprising one or more capacitive components switched in parallel with respect to each other, and each in series with a controllable resistor element.
In general, the resonance circuit may comprise a so called LC resonance circuit, an RC resonance circuit, or an RL resonance circuit. In addition to an inductive part - if present -, comprising one or more inductive components switched in series with respect to each other, and each parallel with a controllable resistor element, one inductive element may be present, in series with the other inductive elements, but without a controllable resistor element, and in addition to a capacitive part - if present -, comprising one or more capacitive components switched in parallel with respect to each other, and each in series with a controllable resistor element, one capacitive component, parallel to the other capacitive components may be present, but without a resistor element in series. These inductive and capacitive elements provide a base functionality, which can be “tuned” by “adding” the other elements.
The invention provides a solution for the problem sketched above. It comprises a low-sensitivity controlled oscillator with the capacitive components switched in parallel with respect to each other, and each in series with a controllable resistor providing an analogue range switching that can be used for temperature compensation without a significant noise penalty. The analogue range switching provides proportional coupling or decoupling of resonator elements to or from the resonator, by connecting them through controlled resistors whose values change from Rs = o to -¾ = 00 , slow enough to prevent unacceptable phase changes in the oscillator output signal, and fast enough to maintain PLL lock during temperature changes. The term resonator elements here refers to inductive, capacitive and resistive elements.
The controllable oscillator circuit according to the invention has several advantages. A first advantage is that, during steady-state behaviour of the oscillator, the carrier to noise ratio of the oscillator is not degraded, neither by added resonator losses, nor by noise from the controlling quantities for the series resistors.
This is because during steady-state operation, the range switching capacitors are either fully connected to the resonator Rs = 0 or are completely removed -¾ = oo from the resonator. Hence, during steady state operation, the quality factor of the resonator is not degraded by any series resistances of the capacitors that are coupled to or decoupled from the resonator. Moreover, any noise on the controlling quantities for the controlled resistors does not degrade the carrier to noise ratio of the oscillator because these controlling quantities do not affect the resonance frequency of the resonator because the capacitors are either completely coupled to the resonator or completely decoupled from the resonator. A second advantage is that the transition between different steady states, that is full conductance and full resistance of the controllable resistor, takes place as so called ‘soft switching’, which does not introduce abrupt phase changes or phase transient effects in the output signal of the oscillator.
While slowly changing the series resistance of the inductance or capacitance to be added or removed, the effective resonator capacitance slowly varies with time and the controlling quantity (voltage in case of a VCO) of the oscillator can smoothly be manipulated to its midscale value. In a first approach, no phase shift in the output signal of the oscillator is observed if the rate of change of the control voltage is much lower than the reciprocal value of the PLL bandwidth. The PLL then instantaneously adapts to the new properties of the oscillator's resonator.
As a third advantage, it is to be remarked that the carrier to noise ratio of the oscillator is not noticeably adversely affected by the soft switching mechanism. This is the case because with soft switching, the quality factor of the resonator is only slightly degraded during a limited time interval, since the degradation of the carrier to noise ratio equals the degradation of the quality factor of the resonator. It will be shown that this degradation during range switching is low if the added capacitance is a small fraction of the total resonator capacitance. In a preferred embodiment, the at least one controllable resistor is a voltage controlled switch, such as a MOS transistor, or a current controlled switch, such as a PN diode.
The invention will now be elucidated into more detail with respect to the following figures. Herein: - Figure 3 shows an implementation of a voltage-controlled oscillator in which the frequency can be controlled over a narrow frequency range by controlling the value of the resistive elements; - Figure 4 shows a simplified circuit model; - Figure 5 shows a table with the resonance frequency as a function of the relative time constant. - Figure 6 shows the quality factor as a function of the relative time constant.
Figure 3 shows an implementation of a voltage-controlled oscillator in which the frequency can be controlled over a narrow frequency range by controlling the value of the resistive elements. The frequency of the VCO increases with its control voltage. Consider this circuit as a part of a PLL synthesizer that has its control voltage, during normal operation, at the midscale value of its control range.
If, due to temperature changes, the VCO control voltage reaches the lower limit of its control range, the series resistance of a capacitor to be added to the resonator is slowly reduced from a very high to a negligibly low value. This effectively slowly increases the resonator parallel capacitance and thereby increases the control voltage of the oscillator. If the control voltage of the VCO reaches its upper limit of the control range, the resonator capacitance is slowly decreased by slowly increasing the value of the series resistance of one of its connected range selection capacitors, from a negligibly low to a very high value.
Figure 4 shows a simplified circuit model for calculation purposes. The following definition of states will be used: a capacitor is fully added to the resonator if the time constant that it forms with its series resistance is much smaller than the reciprocal value of the angular frequency of oscillation, and a capacitor is fully removed from the resonator if the time constant that it forms with its series resistance is much higher than the reciprocal value of the angular frequency of oscillation.
In general, the common value of the capacitors is controllable over a range wherein the largest and the smallest value differ such, that the resonance frequency differs at least the same factor as the upper and the lower value of the control range that can be obtained with the voltage signal.
Figure 5 shows the relative change of the resonance frequency (vertical: U* Τρς i'C·' ) when a series network that consists of a capacitor with a capacitance «C (0 < a <:< 1) in series with a resistor Rs, is placed in parallel with a parallel resonator circuit that has a resonator capacitance of C and an ideal inductor with an inductance L (RL = 0);
Figure NL2011996CD00071
The ratio of the time constant of the parallel RC branch (RsaC) and the reciprocal value of the angular resonance frequency of the basic LC resonator (%/LC) is taken as x-axis variable:
Figure NL2011996CD00072
x Ranges from 0.01 to 100 (logarithmic scale), with the parameter “stepping from 0.01 until 0.1.
Figure 5 clearly shows that the resonance frequency of the resonator shifts with the series resistance of the parallel branch. The highest sensitivity for resistance change is obtained around x = 7, this is the region in which the time constant of the series branch equals the reciprocal value of the angular frequency Vic .
Figure 6 shows the quality factor Q of the resonator (vertical) when a series network that consists of a capacitor with a capacitance aC in series with a resistor Rs, is placed in parallel with a parallel resonator circuit that has a resonator capacitance of C and an inductor with an inductance L and a quality factor Qi= 10.
Figure NL2011996CD00081
The ratio of the time constant of the parallel RC branch and the reciprocal value of the angular resonance frequency of the basic LC resonator WLC) is taken as x-axis variable:
Figure NL2011996CD00082
x Ranges from 0.01 to 100 (logarithmic scale), with the parameter a stepping from 0.01 until 0.1.
Figure 6 clearly shows the decrease of the quality factor for values around x = 1, which occur when the time constant of the series branch approaches the reciprocal value of the angular resonance frequency of the original LC resonator. During soft switching with a = ti.i (so 10% of the original resonator capacitance is added), the quality factor of the resonator drops to 65% of its original value, which results in a temporarily degradation of the carrier to noise ratio during soft switching of about 3dB.
Figure 4 can be used to explain the effect of soft switching on the quality factor Q. Consider the resonator, with the parallel branches L, C, and a<~' + -¾ , as depicted below. Also consider that ureAaC . js case if x = i
The quality factor Q of the resonator can be evaluated from the quality factor Qi of the inductor and the quality factor of the capacitor Qc as:
Figure NL2011996CD00091
The quality factor of a resonator element can be defined as:
Figure NL2011996CD00092
The quality factor of the resonator capacitor (that consists of the two capacitors) can now be evaluated as follows. Under the given conditions, the total stored energy Ec on the capacitors can be evaluated as:
Figure NL2011996CD00093
In which Vc is the peak voltage across the resonator. The energy losses ER in the series resistor, over one cycle, can be evaluated as:
Figure NL2011996CD00094
Using the condition-ω res^s U = 1 we obtain:
Figure NL2011996CD00095
Hence, the quality factor Qc of the total resonator capacitor can be obtained as:
Figure NL2011996CD00096
With a = 0,1 this yields Qc = 21 with Qt = 10 this yields a quality factor of the resonator: Q = 6.77. This roughly corresponds to the value found in the graph for x = 1 and e = 0.1 .
Consider a VCO with a tuning range of +/- 0.1%, which is part of a PLL synthesizer with a bandwidth of more than 100kHz. The temperature coefficient of the VCO is 300ppm/K and the operating temperature range of the PLL is from -25 to + 75 degrees Celsius.
Over this operating range the VCO frequency drift (for a fixed input voltage amounts 3%, or 30 times its operating range. For maintaining PLL lock over the complete temperature range one could decide to add 60 RC branches to the resonator with capacitances that are 0.1% (<* = o.ooi ) of the initial resonator capacitance.
If we assume a temperature change during operation of 1 degree Celsius per second, the number of required VCO range changes equals 60 per 100 seconds. Considering the bandwidth of the PLL synthesizer, a soft switching traject of about 10ms would be long enough to prevent abrupt phase changes in the output signal, and short enough to adjust to temperature changes. During a fraction of this soft switching traject, say 1 ms, the CNR of the VCO is degraded from lets say 10 to 9.95. The average drop AQ of the quality factor then equals:
Figure NL2011996CD00101
Since the change in the CNR of the VCO is equal to the change of the quality factor of the resonator, the average change in the CNR (5.2mdB) will hardly be observable!
Techniques for realization of current or voltage dependent resistors are known. An important aspect of the soft-switching controlled oscillator is that the series resistance in the parallel branch should be very high when this branch is made inactive. This is because an inactive parallel branch behaves resistive at the resonance frequency and, as a consequence, its resistance affects the quality factor of the resonator. Controlled resistors that can be controlled over a very large resistance range, can easily be realized with MOS transistors or PN diodes.
Besides the embodiments shown, multiple other embodiments are possible, which are all believed to fall within the scope of the present invention as defined in the following claims.

Claims (10)

1. Een bestuurbaar oscillatorcircuit, omvattende: Een bestuurbare oscillator; Een resonantiecircuit, gekoppeld aan de bestuurbare oscillator, en omvattende: o een inductief gedeelte, omvattende een of meer inductieve componenten in serie geschakeld met elkaar, en elk parallel met een bestuurbaar weerstandelement; en/of o een capacitief deel, omvattende een of meer capacitieve componenten parallel aan elkaar geschakeld, en elk in serie met een bestuurbaar weerstandselement.A controllable oscillator circuit, comprising: A controllable oscillator; A resonance circuit, coupled to the controllable oscillator, and comprising: o an inductive portion, comprising one or more inductive components connected in series with each other, and each in parallel with a controllable resistor element; and / or a capacitive part, comprising one or more capacitive components connected in parallel to each other, and each in series with a controllable resistance element. 2. Circuit volgens conclusie 1, verder omvattende een besturing voor de oscillator en/of ten minste een van de bestuurbare weerstandselementen.Circuit according to claim 1, further comprising a control for the oscillator and / or at least one of the controllable resistance elements. 3. Circuit volgens conclusie 1 of 2, waarbij ten minste een bestuurbare weerstand een spanningsgestuurde schakelaar omvat, zoals een MOS transistor.The circuit according to claim 1 or 2, wherein at least one controllable resistor comprises a voltage-controlled switch, such as an MOS transistor. 4. Circuit volgens conclusie 1 of 3, waarbij ten minste een bestuurbare weerstand een stroomgestuurde schakelaar is, zoals een PN diode.The circuit of claim 1 or 3, wherein at least one controllable resistor is a current controlled switch, such as a PN diode. 5. Circuit volgens een van de voorgaande conclusies, waarbij de besturing geconfigureerd is voor het geleidelijk veranderen van de waarde van het weerstandselement.Circuit according to one of the preceding claims, wherein the control is configured to gradually change the value of the resistor element. 6. Circuit volgens een van de voorgaande conclusies, waarbij de gemeenschappelijke waarde van de capaciteiten bestuurbaar is over een range waarin de grootste en de kleinste waarde zodanig verschillen dat de resonantiefrequentie ten minste dezelfde factor verschilt als de bovenste en onderste waarde van een besturingsinterval dat bereikt kan worden met het spanningssignaal.Circuit according to one of the preceding claims, wherein the common value of the capacitances is controllable over a range in which the largest and the smallest values differ such that the resonance frequency differs by at least the same factor as the upper and lower value of a control interval that reaches can be with the voltage signal. 7. Werkwijze voor het bedrijven van een bestuurbaar oscillatorcircuit, omvattende de stappen van: Het verschaffen van een bestuurbaar oscillatorcircuit volgens een van de voorgaande conclusies; Het bepalen van een gewenste verandering in een oscillatiefrequentie; Het geleidelijk wijzigen van de weerstandswaarde van ten minste een weerstandselement.A method for operating a controllable oscillator circuit, comprising the steps of: providing a controllable oscillator circuit according to any of the preceding claims; Determining a desired change in an oscillation frequency; Gradually changing the resistance value of at least one resistance element. 8. Werkwijze volgens conclusie 7, waarbij het veranderen van de weerstandswaarde het veranderen van de waarde van een maximale geleidbaarheid tot de maximale weerstand van een element omvat, of vice versa.The method of claim 7, wherein changing the resistance value comprises changing the value from a maximum conductivity to the maximum resistance of an element, or vice versa. 9. Werkwijze volgens conclusie 7 of 8, omvattende het veranderen van een frequentiebesturingsspanning van het oscillatorcircuit simultaan met de weerstandswaarde.A method according to claim 7 or 8, comprising changing a frequency control voltage of the oscillator circuit simultaneously with the resistance value. 10. Werkwijze volgens conclusie 9, waarbij de frequentiebesturingsspanning en de weerstandswaarde zodanig zijn gearrangeerd dat de uitgangsfrequentie van het circuit onveranderd blijft.The method of claim 9, wherein the frequency control voltage and the resistance value are arranged such that the output frequency of the circuit remains unchanged.
NL2011996A 2013-12-20 2013-12-20 Controllable oscillator circuit and method for operating such circuit. NL2011996C2 (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030025579A1 (en) * 2001-07-31 2003-02-06 Christensen Kaare Tais IGFET and tuning circuit
US20060192598A1 (en) * 2001-06-25 2006-08-31 Baird Rex T Technique for expanding an input signal
WO2008114383A1 (en) * 2007-03-19 2008-09-25 Fujitsu Limited Voltage controlled oscillator and synthesizer circuit

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20060192598A1 (en) * 2001-06-25 2006-08-31 Baird Rex T Technique for expanding an input signal
US20030025579A1 (en) * 2001-07-31 2003-02-06 Christensen Kaare Tais IGFET and tuning circuit
WO2008114383A1 (en) * 2007-03-19 2008-09-25 Fujitsu Limited Voltage controlled oscillator and synthesizer circuit

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
LEE J H ET AL: "A Low Phase Noise Octa-Phase LC VCO for Multi-band Direct Conversion Receiver", IEEE ELECTROMAGNETICS IN ADVANCED APPLICATIONS, 2007, September 2007 (2007-09-01), pages 411 - 414, XP031163748 *
MAZZANTI A ET AL: "Analysis and design of a dual band reconfigurable VCO", IEEE ELECTRONICS, CIRCUITS AND SYSTEMS, ICECS, 13 December 2004 (2004-12-13), pages 37 - 40, XP010774792 *

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