Degeneration for a wideband voltage-controlled oscillator
First Claim
1. A voltage-controlled oscillator (VCO) circuit comprising:
- a tank circuit coupled to a pair of nodes, the pair of nodes including a first node and a second node;
a first cross-coupled transistor pair of a first transistor type, a drain terminal of a first transistor of the first cross-coupled transistor pair connected to the first node of the pair of nodes, a drain terminal of a second transistor of the first cross-coupled transistor pair connected to the second node of the pair of nodes, and a source terminal of the first transistor of the first cross-coupled transistor pair and a source terminal of the second transistor of the first cross-coupled transistor pair connected to a third node;
a second cross-coupled transistor pair of a second transistor type, a drain terminal of a third transistor of the second cross-coupled transistor pair connected to the first node of the pair of nodes, a drain terminal of a fourth transistor of the second cross-coupled transistor pair connected to the second node of the pair of nodes, and a source terminal of the third transistor of the second cross-coupled transistor pair and a source terminal of the fourth transistor of the second cross-coupled transistor pair connected to a fourth node; and
a degeneration network comprising;
a first inductor connected between the third node and a supply voltage;
a second inductor connected between the fourth node and a ground; and
a capacitor, a first terminal of the capacitor connected to the third node and a second terminal of the capacitor connected to the fourth node, the capacitor comprising a switched degeneration capacitor bank configured to provide a degeneration capacitance value selected from multiple capacitance values based on a degeneration-tuning control signal.
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Accused Products
Abstract
The present disclosure describes aspects of degeneration for a wideband voltage-controlled oscillator (VCO) circuit. In some aspects, the VCO circuit includes a degeneration network that includes a first inductor, a second inductor, and a capacitor. The degeneration network is connected between the a supply voltage and ground, with the capacitor connected across the differential VCO, between the sources of cross-coupled PMOS transistors and the sources of cross-coupled NMOS transistors. Control circuitry selects an inductance value of a switched inductance network to select a frequency band in which the VCO circuit operates. The control circuitry also sets a switched capacitor bank and a variable capacitor bank to tune the VCO circuit to an operating frequency within the selected frequency band. The control circuitry further tunes the degeneration network to degenerate the VCO circuit to reduce phase noise in an output signal of the VCO circuit.
16 Citations
30 Claims
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1. A voltage-controlled oscillator (VCO) circuit comprising:
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a tank circuit coupled to a pair of nodes, the pair of nodes including a first node and a second node; a first cross-coupled transistor pair of a first transistor type, a drain terminal of a first transistor of the first cross-coupled transistor pair connected to the first node of the pair of nodes, a drain terminal of a second transistor of the first cross-coupled transistor pair connected to the second node of the pair of nodes, and a source terminal of the first transistor of the first cross-coupled transistor pair and a source terminal of the second transistor of the first cross-coupled transistor pair connected to a third node; a second cross-coupled transistor pair of a second transistor type, a drain terminal of a third transistor of the second cross-coupled transistor pair connected to the first node of the pair of nodes, a drain terminal of a fourth transistor of the second cross-coupled transistor pair connected to the second node of the pair of nodes, and a source terminal of the third transistor of the second cross-coupled transistor pair and a source terminal of the fourth transistor of the second cross-coupled transistor pair connected to a fourth node; and a degeneration network comprising; a first inductor connected between the third node and a supply voltage; a second inductor connected between the fourth node and a ground; and a capacitor, a first terminal of the capacitor connected to the third node and a second terminal of the capacitor connected to the fourth node, the capacitor comprising a switched degeneration capacitor bank configured to provide a degeneration capacitance value selected from multiple capacitance values based on a degeneration-tuning control signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A voltage-controlled oscillator (VCO) comprising:
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a tank circuit coupled to a pair of nodes, the pair of nodes including a first node and a second node; a first cross-coupled transistor pair of a first transistor type, a drain terminal of a first transistor of the first cross-coupled transistor pair connected to the first node of the pair of nodes, a drain terminal of a second transistor of the first cross-coupled transistor pair connected to the second node of the pair of nodes, and a source terminal of the first transistor of the first cross-coupled transistor pair and a source terminal of the second transistor of the first cross-coupled transistor pair connected to a third node; a second cross-coupled transistor pair of a second transistor type, a drain terminal of a third transistor of the second cross-coupled transistor pair connected to the first node of the pair of nodes, a drain terminal of a fourth transistor of the second cross-coupled transistor pair connected to the second node of the pair of nodes, and a source terminal of the third transistor of the second cross-coupled transistor pair and a source terminal of the fourth transistor of the second cross-coupled transistor pair connected to a fourth node; and means for providing differential degeneration to the VCO, comprising; a first inductor connected between the third node and a supply voltage; a second inductor connected between the fourth node and a ground; and means for providing a degeneration capacitance having a degeneration capacitance value selected from multiple capacitance values, the means for providing the degeneration capacitance connected to the third node and the fourth node. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
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21. A voltage-controlled oscillator (VCO) operating method comprising:
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generating an oscillating signal having a fundamental frequency using a VCO, the VCO comprising; a tank circuit; a first cross-coupled transistor pair of a first transistor type, drain terminals of the first cross-coupled transistor pair being connected to the tank circuit, and source terminals of the first cross-coupled transistor pair connected to a first node; and a second cross-coupled transistor pair of a second transistor type, drain terminals of the second cross-coupled transistor pair of the second transistor type being connected to the tank circuit, and source terminals of the second cross-coupled transistor pair connected to a second node; presenting a frequency-dependent impedance to the source terminals of the first and second cross-coupled transistor pairs using a resonant circuit, the resonant circuit comprising; a first inductor connected between the first node and a supply voltage; a second inductor connected between the second node and a ground; and a capacitor connected between the first node and the second node, the capacitor comprising a switched degeneration capacitor hank configured to provide a degeneration capacitance value selected from multiple capacitance values based on a degeneration-tuning control signal, wherein the resonant circuit is tuned to resonate at a frequency that is approximately twice the fundamental frequency. - View Dependent Claims (22, 23, 24, 25)
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26. A frequency synthesizer apparatus, comprising:
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a phase locked loop (PLL) synthesizer comprising; a reference oscillator configured to generate a reference frequency signal; and a voltage-controlled oscillator (VCO) configured to generate an output signal having a frequency that is controlled at least partially by the reference frequency signal, the VCO including a degeneration network that is configured to degenerate phase noise in the output signal of the VCO in response to a degeneration-tuning control signal, the degeneration network comprising a degeneration capacitor bank that is configured to tune the degeneration network in relation to the frequency of the VCO; and a control signal generator configured to provide; a band-selection control signal to select an inductance value from multiple inductance values provided by a switched inductor network included in the VCO, the selected inductance value determining a frequency band of operation for the frequency synthesizer; a coarse-tuning control signal and a fine-tuning control signal to set the frequency of the output signal of the VCO; and the degeneration-tuning control signal to tune the degeneration network to provide at least one differential degeneration signal to reduce the phase noise in the output signal of the VCO. - View Dependent Claims (27, 28, 29, 30)
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Specification