RF Modulator Circuit Using 25% LO Duty Cycle for Lower Noise
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing modulation circuits in wireless communication devices face challenges in reducing drive amplitude requirements and improving output voltage swing while maintaining signal-to-noise ratio, particularly due to conventional fifty percent duty cycle local oscillator signals.
Innovation Solution
A modulation circuit with a local oscillator configured to generate signals at a twenty-five percent duty cycle, combined with a transconductance and mixer stage circuit, reduces current consumption and noise, allowing for improved output power and signal-to-noise ratio without degrading performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional fifty percent duty cycle local oscillator signals are used, then the modulation circuit operates with standard current consumption, but the current consumption and noise are higher than necessary
Solution Approach 1:
The patent changes the duty cycle parameter of the local oscillator signal from the conventional 50% to 25%. This parameter change reduces the current consumption and noise in the modulation circuit while maintaining the signal-to-noise ratio through compensating design adjustments in the transconductance and mixer stages
2Loss of energy
If the local oscillator duty cycle is reduced to twenty-five percent, then current consumption and noise are halved, but output power is reduced by 3 dB
Solution Approach 1:
The patent accepts the 3 dB reduction in output power as a trade-off for halving the noise, and compensates by optimizing other circuit parameters including the transconductance values and mixer stage design to maintain overall system performance
3Force
If conventional modulation circuits are used, then drive amplitude requirements are standard, but the drive amplitude requirements are higher than necessary
Solution Approach 1:
The patent combines the transconductance stage and mixer stage into an integrated configuration where the local oscillator signal directly controls the mixing process. This merging reduces the drive amplitude requirements by eliminating separate amplification stages while maintaining signal integrity through the unified circuit design
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The twenty-five percent duty cycle modulation circuit halves current consumption and noise, maintaining signal-to-noise ratio while reducing output power by 3 dB, and offers improved output voltage swing and reduced drive amplitude requirements.
Implementation Method 1
a local oscillator circuit configured to generate one or more local oscillator signals at a desired frequency and with a duty cycle at or about twenty-five percent
Implementation Method 2
a mixer stage circuit configured to generate one or more mixer output signals responsive to the one or more current signals and the one or more local oscillator signals
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A modulation circuit for use in a radiofrequency transmitter includes a local oscillator circuit configured to generate one or more local oscillator signals at a desired frequency and with a duty cycle at or about twenty-five percent, and a modulator configured to generate one or more modulated signals responsive to the one or more local oscillator signals and one or more baseband information signals. In at least one embodiment, the modulation circuit includes a modulator comprising a combined mixing and transconductance circuit that includes a transistor circuit for each baseband information signal serving as a modulation input to the modulator. Each transistor circuit comprises a first transistor driven by the baseband information signal and coupling a modulator output node to a corresponding transconductance element, and a second transistor driven by one of the one or more local oscillator signals and coupling the corresponding transconductance element to a signal ground node.