Antenna Backplane Layout With Phase-Shift Circuit for Crosstalk
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Solution Overview
Problem
The increased frequency and pin count in mmW phased array antennas cause severe signal rejection and crosstalk between differential pairs, leading to larger PCB sizes and higher costs, which are not feasible in certain environments.
Innovation Solution
Implementing a phase-shifting series resonant or tuning stub circuit between the outer conductors of differential pairs to provide an odd-integer multiple of 180-degree phase shift, reducing crosstalk and maintaining signal integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the spacing between traces of a differential pair is increased to reduce signal rejection, then the connector performance is improved, but the PCB size increases and cost increases
Solution Approach 1:
The patent applies asymmetry by creating unequal spacing between conductors in the differential pairs. Specifically, the first conductor is positioned at a first distance from the second differential pair while the second conductor is positioned at a second distance, where the first distance is greater than the second distance. This asymmetric configuration, combined with the phase-shifting circuit, allows for reduced signal rejection without requiring increased spacing between all conductors, thereby maintaining compact PCB size.
Solution Approach 2:
The patent introduces a phase-shifting series resonant or tuning circuit as an intermediary element coupled between the first conductor and the fourth conductor. This intermediary circuit provides approximately an odd-integer multiple of a 180 degree phase shift at a predetermined frequency, which compensates for signal rejection issues without requiring increased physical spacing between differential pair traces, thus avoiding PCB size expansion.
2Speed
If the pin count of the connector is increased to maintain transmission line functionality at higher frequencies, then the frequency performance is improved, but crosstalk between differential pairs increases
Solution Approach 1:
The asymmetric conductor positioning creates different coupling characteristics between adjacent differential pairs. By having the first conductor at a greater distance from the second differential pair than the second conductor, the patent reduces mutual coupling and crosstalk between pairs, enabling higher pin count connectors to operate at higher frequencies with reduced interference.
Solution Approach 2:
The phase-shifting series resonant circuit acts as an intermediary that introduces a controlled phase difference between signals on adjacent differential pairs. This phase shift of approximately an odd-integer multiple of 180 degrees causes signals to be out of phase, which reduces constructive interference and minimizes crosstalk between densely packed high-pin-count connector traces.
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 approach allows for the use of shorter, high pin count connectors, reducing PCB size and cost while maintaining system performance by minimizing signal rejection and crosstalk.
Implementation Method 1
A phase-shifting series resonant or tuning circuit is coupled between the first conductor and the fourth conductor and provides approximately an odd-integer multiple of a 180 degree phase shift at a predetermined frequency.
Implementation Method 2
A phase-shifting series resonant or tuning circuit is coupled between the first conductor and the fourth conductor and provides approximately an odd-integer multiple of a 180 degree phase shift at a predetermined frequency.
Data Source
AI summary
An antenna backplane including a printed circuit board (PCB) having a first differential pair with a first conductor and a second conductor and a second differential pair with a third conductor and a fourth conductor. The first conductor is positioned a first distance from the second differential pair and the second conductor is positioned a second distance from the second differential pair of conductors, where the first distance is greater than the second distance. The third conductor is positioned the second distance from the first differential pair and the fourth conductor is positioned a third distance from the first differential pair, where the third distance is greater than the second distance. A phase-shifting series resonant circuit is coupled between the first conductor and the fourth conductor that provides approximately an odd-integer multiple of a 180 degree phase shift at a predetermined frequency.