Pierce Oscillator Port Decoupling for Far-Out and Closed-In Phase Noise
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Solution Overview
Problem
Conventional Pierces oscillators are unable to simultaneously reduce far-out phase noise (frequency offsets above 10KHz) and closed-in phase noise (frequency offsets below 100Hz) due to limitations in voltage signal amplitude, which affects active device nonlinearity and driving capability.
Innovation Solution
An oscillator apparatus with an inverting transconductance amplifier, capacitors, and a resonator, where the capacitance of the first capacitor is smaller than the second capacitor, and a DC coupling circuit is used to enhance signal amplitude and avoid non-linear operating regions, allowing for independent common mode definition and reduced phase noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a conventional Pierce oscillator generates a larger voltage signal to improve device driving capability, then the driving capability is improved, but the larger amplitude causes active devices to be affected by nonlinearity effects and increases closed-in phase noise
Solution Approach 1:
The oscillator is divided into two independent ports: a first port (output port) with larger voltage swing for driving capability, and a second port (input port) with smaller voltage swing to avoid nonlinearity. This segmentation allows each port to have optimized amplitude characteristics independently, resolving the contradiction between driving capability and nonlinearity effects.
2Object-generated harmful factors
If a conventional Pierce oscillator generates a smaller voltage signal to avoid nonlinearity effects, then closed-in phase noise is reduced, but the device driving capability is limited
Solution Approach 1:
The oscillator provides two separate output ports with different amplitude characteristics: the second port (input port) delivers smaller amplitude signals to avoid nonlinearity effects and reduce closed-in phase noise, while the first port (output port) delivers larger amplitude signals for sufficient driving capability. This segmentation resolves the contradiction by providing both signal types simultaneously.
3Ease of operation
If AC coupling capacitors are used to couple the oscillator output to the driver, then signal transmission is achieved, but signal attenuation and loss occur
Solution Approach 1:
The AC coupling capacitors are removed from the signal path by implementing direct DC coupling between the oscillator output and the driver circuit. This extraction of the problematic component eliminates the associated signal attenuation and energy loss while maintaining signal transmission functionality through a lossless direct connection.
Data Source
Figure 1
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AI summary
An oscillator apparatus (100) includes an oscillator core circuit (105). The oscillator core circuit (105) includes an inverting transconductance amplifier (1052), at least one first capacitor (1053A, 4053A), at least one second capacitor (1053B, 4053B), and a resonator (1054). The at least one first capacitor (1053A, 4053A) is connected between an input of the inverting transconductance amplifier (1052) and a ground level. The at least one second capacitor (1053B, 4053B) is connected between an output of the inverting transconductance amplifier (1052) and the ground level. The resonator (1054) has a first port connected to the input of the inverting transconductance amplifier (1052) and a second port connected to the output of the inverting transconductance amplifier (1052). The first port is decoupled from the second port.