Quadrature Subharmonic Mixer Polyphase Filter
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Solution Overview
Problem
Existing subharmonic mixers in wireless communication devices require lossy polyphase filters or complex phase shift circuitry to generate 90° phase separation, leading to substantial power consumption and reduced receiver efficiency.
Innovation Solution
A quadrature subharmonic mixer is implemented using a polyphase filter to generate quadrature components of the local oscillator signal, combined with a summing and scaling element to create additional components, which are then used with a radio frequency signal by mixer elements to achieve downconversion without altering the RF signal, thereby eliminating the need for lossy polyphase filtering in the RF path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lossy polyphase filters are used to generate quadrature components of the RF signal, then 90° phase separation is achieved, but power consumption increases and receiver efficiency decreases
Solution Approach 1:
The patent introduces a local oscillator signal as an intermediary to achieve quadrature mixing. Instead of directly filtering the RF signal through lossy polyphase filters, the invention uses LO signals at frequencies f/2, f/2+90°, -f/2, and -f/2+90° to mix with the RF signal, thereby obtaining the desired quadrature components without substantial power loss.
Solution Approach 2:
The invention changes the frequency parameter of the local oscillator signal from the traditional f to f/2 (subharmonic frequency). This parameter change enables the mixer to operate with reduced power consumption while still achieving the required 90° phase separation through the combination of subharmonic mixing and quadrature LO signals.
2Reliability
If complex phase shift circuitry is used to generate quadrature components of the LO signal, then 90° phase separation is achieved, but device complexity and power consumption increase
Solution Approach 1:
The patent uses a simplified phase shift circuit that generates quadrature components of the subharmonic LO signal. Instead of complex circuitry operating at the full RF frequency, the invention employs intermediate subharmonic signals at f/2, which require less complex phase shift circuitry to achieve the same 90° phase separation.
3Productivity
If subharmonic mixing is used with traditional phase shifting methods, then downconversion is achieved, but receiver efficiency is reduced due to power loss
Solution Approach 1:
The patent converts the potential disadvantage of using subharmonic frequencies into a benefit. By using LO signals at f/2 instead of f, the invention reduces power consumption and improves efficiency. The subharmonic mixing technique, when combined with quadrature LO signals, transforms what could be a source of inefficiency into a power-saving mechanism.
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
This solution reduces power consumption and improves receiver efficiency by avoiding lossy polyphase filtering in the RF path, allowing for efficient downconversion of RF signals while maintaining receiver sensitivity.
Implementation Method 1
a polyphase filter configured to generate quadrature components of a local oscillator (LO) reference signal
Implementation Method 2
a plurality of mixer elements configured to combine the quadrature components of the LO reference signal and the additional components of the LO reference signal with a radio frequency (RF) signal to obtain a downconverted RF signal
Data Source
AI summary
A quadrature subharmonic mixer comprises a polyphase filter configured to generate quadrature components of a local oscillator (LO) reference signal, a summing and scaling element configured to create additional components of the LO reference signal, and a plurality of mixer elements configured to multiply the quadrature components of the LO reference signal and the additional components of the LO reference signal with a radio frequency (RF) signal to obtain a downconverted version of the RF signal.