Fourth-Order Image Rejection Mixer With 90° LO Phase Cancellation
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Solution Overview
Problem
Conventional image rejection mixers suffer from unwanted frequency components near the desired RF frequency, particularly in harmonic mixers, which require additional filtering to suppress these spurious signals.
Innovation Solution
The use of a 90-degree LO distributor with a phase difference instead of the conventional LO distributor, combined with fourth-order harmonic mixers and 90-degree IF and RF synthesis distributors, to suppress unwanted frequency components by synthesizing desired and image waves out of phase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional LO distributor is used in a harmonic mixer, then the device can operate as an image rejection mixer, but unwanted frequency components exist at the vicinity of the desired RF frequency
Solution Approach 1:
The patent changes the phase difference parameter of the LO distributor from the conventional value (not specified) to exactly 90 degrees. This parameter change causes unwanted frequency components to be synthesized out of phase and cancelled, while desired signals are synthesized in phase and reinforced, resolving the contradiction between suppressing harmful frequency components and maintaining image rejection performance
Solution Approach 2:
The patent converts the harmful unwanted frequency components into beneficial cancellations by using the 90-degree phase difference. The same mixing process that generates unwanted components also enables their cancellation when signals are recombined with the correct phase relationship, turning the harmful effect into a useful image rejection mechanism
2Productivity
If a harmonic mixer is used to extract IF signal and RF signal components, then mixing function is achieved, but a lot of unwanted frequency components exist near the desired wave
Solution Approach 1:
The patent segments the signal processing into two distinct paths: one path processes desired frequency components while the other processes image and unwanted components. By using two separate mixers with 90-degree phase difference and then recombining them, the system separates desired signals from spurious components, enabling efficient signal extraction while suppressing unwanted frequency components
Solution Approach 2:
The 90-degree LO distributor acts as an intermediary element that introduces a controlled phase shift between the two mixing paths. This intermediary phase shift enables the subsequent cancellation of unwanted frequency components when the paths are recombined, while preserving the desired signal components
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 configuration effectively reduces unwanted frequency components near the desired wave, alleviating the need for steep filters and improving the overall performance of image rejection mixers in wireless communication devices.
Implementation Method 1
a 90-degree LO distributor 5 which distributes and outputs an input signal at a first terminal from second and third terminals with a phase difference of 90 degrees
Implementation Method 2
first and second fourth-order harmonic mixers 7a and 7b that output an RF as a mixed wave of a fourth order component of an input LO signal frequency and an IF first order component
Implementation Method 3
output an RF as a mixed wave of a fourth order component of an input LO signal frequency and an IF first order component
Implementation Method 4
a 90-degree IF synthesis distributor 4 which distributes and outputs an input signal at a first terminal from second and third terminals with a phase difference of 90 degrees
Implementation Method 5
there is a harmonic mixer for extracting intermediate frequency (hereinafter, referred to as IF) signal and RF signal components by using an antiparallel diode pair in which diodes are connected to each other at reversed polarity
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
Provided are an image rejection mixer and a communication device, which may suppress unwanted frequency components of a high power output assuming a fourth-order harmonic mixer. An image rejection mixer and a communication device include first and second fourth-order harmonic mixers (7a and 7b), a 90-degree IF synthesis distributor (4), a 90-degree LO distributor (5), and a 90-degree RF synthesis distributor (6). Use of the 90-degree distributors for LO distribution of the fourth-order harmonic image rejection mixer suppresses the unwanted frequency components of the high power output.