Ring Oscillator Circuit for 90-Degree Phase Shift
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing oscillation circuits face challenges in generating signals with a 90° phase difference, particularly for direct conversion and integration, as they are either limited to narrow bands or unsuitable for semiconductor integration, and fluctuate with high-intensity input signals.
Innovation Solution
A ring oscillator-based oscillation circuit that generates two output signals with a 90° phase difference by using a differential type ring oscillator with interpolation type delay circuits and multiplying portions to produce mixed signals, allowing for broad band operation and integration without frequency fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an LC oscillator is used to generate signals with a 90° phase difference through halved frequency division, then the frequency can be varied by using a variable condenser for broadband operation, but it is difficult to integrate into semiconductor LSI chips
Solution Approach 1:
The patent replaces the mechanical LC oscillator circuit with a ring oscillator implemented using differential type inversion amplifiers and delay circuits that can be fabricated as semiconductor integrated circuits. This substitution maintains the frequency variation capability through control voltage while enabling LSI integration, thus resolving the contradiction between broadband adaptability and ease of manufacture.
2Device complexity
If the oscillation frequency of the LC oscillator is set to the same as the local signal for direct conversion, then the circuit construction is simple, but the frequency fluctuates with high-intensity input signals making direct conversion difficult
Solution Approach 1:
The patent employs a ring oscillator where the oscillation frequency is dynamically controlled by a control voltage applied to differential type inversion amplifiers. This dynamic control mechanism allows the oscillator to maintain stable frequency operation even with high-intensity input signals, while keeping the circuit construction relatively simple through the use of standard amplifier and delay circuit building blocks.
3Manufacturing precision
If RC filters are used to phase shift the LC oscillator signal by 45° to obtain 90° phase difference signals, then two signals with the required phase difference are obtained, but the frequency range is restricted by the cut-off frequency of the RC filter limiting it to a narrow band
Solution Approach 1:
The patent segments the oscillation loop into multiple delay circuits, each contributing a specific phase delay. By combining the phase delays of multiple segments (inversion amplifiers and delay circuits), the total phase difference of 90° is achieved across a broad frequency range without being constrained by RC filter cut-off frequencies, thus resolving the contradiction between phase precision and bandwidth.
Data Source
AI summary
An oscillation circuit for generating two oscillation signals having a phase difference of 90° by using an LC oscillator has a disadvantage for integration. Therefore, a differential type ring oscillator comprising interpolation type delay circuits of four stages is used as an original oscillator without using any LC oscillator. The oscillation frequency of the original oscillator is set to f/2. Intermediate signals S(k) having a phase difference of 45(k−1)° with respect to a reference phase are obtained as the outputs of the respective stages of the original oscillator. A multiplying circuit 22 generates the product signal of S(2) and S(4) in mixers. This product signal is vibrated at cos (ft/2), and the output signal Vout1 is generated on the basis of the product signal. A multiplying circuit generates the product signal of S(1) and S(3) in mixers. This product signal is vibrated at cos(ft/2+π/2), and the output signal Vout2 is generated on the basis of the product signal. Vout1, Vout2 are output as the oscillation signals having the frequency f and the phase difference of 90°.