On-Chip Antenna Efficiency via Substrate Segmentation
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Solution Overview
Problem
CMOS technology faces challenges in achieving efficient THz radiating arrays due to high silicon substrate permittivity leading to radiation loss, inefficient THz generation, and locking issues, particularly in the 'THz Gap' frequency range, which limits scalability and increases costs.
Innovation Solution
The solution involves creating isolated individual areas for on-chip antennas using metallized channels in the silicon substrate to conserve gain, employing a differential Colpitts VCO topology for efficient THz generation, and implementing wireless subharmonic injection locking to achieve frequency and phase locking without the need for expensive technologies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If on-chip antennas are designed upon a grounded silicon substrate, then integration is simplified, but radiation efficiency deteriorates due to waves getting trapped and coupled to surface wave modes
Solution Approach 1:
The patent segments the continuous silicon substrate by introducing trenches that divide the substrate into isolated regions. Each antenna element is positioned within its own isolated region, preventing electromagnetic coupling between adjacent antenna elements and reducing surface wave effects while maintaining integration simplicity
Solution Approach 2:
The patent introduces an intermediary structure (trenches filled with dielectric material or air gaps) between the antenna elements and the silicon substrate. This intermediary layer acts as a barrier that reduces the coupling of electromagnetic waves to surface wave modes while allowing the antennas to remain integrated on the silicon chip
2Loss of energy
If antenna array area is increased to achieve maximum gain, then radiation efficiency improves, but silicon area consumption increases non-proportionally
Solution Approach 1:
By segmenting the substrate into isolated regions, the patent enables compact antenna element spacing without mutual interference. This allows the antenna array to achieve maximum gain with a smaller overall silicon footprint, as each element operates independently within its isolated region
Solution Approach 2:
The patent applies local quality changes by creating regions with different electromagnetic properties around each antenna element. The trenches and filling materials modify the local electromagnetic environment to enhance radiation efficiency without requiring a large overall array area
3Reliability
If active multiplier chains are used to lock THz signals to reference frequency, then frequency locking is achieved, but DC power consumption increases significantly
Solution Approach 1:
The patent replaces the active multiplier chain mechanism with a passive frequency multiplication approach. The non-linear capacitance of the varactor diode in the VCO circuit naturally generates harmonic frequencies, eliminating the need for power-hungry active multipliers while achieving the same frequency locking function
4Quantity of substance
If harmonic generation is used to produce THz frequencies from mm-wave sources, then THz signal generation is achieved, but generation efficiency and output power are reduced
Solution Approach 1:
The patent employs dynamic frequency multiplication through a voltage-controlled oscillator that can be tuned to generate the desired THz frequencies. The VCO's non-linear characteristics dynamically generate harmonics with higher efficiency than static multiplier chains, improving both output power and generation efficiency
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 results in high-gain, low-cost THz radiating arrays with efficient power transmission and reduced DC power consumption, overcoming previous limitations in antenna efficiency and locking mechanisms, enabling scalable and cost-effective THz frequency operation.
Implementation Method 1
The silicon bulk in standard CMOS has a high permittivity and low resistivity that incurs significant radiation loss at 0.3 THz with bulk thickness of 100-800 μm. If an on-chip antenna is designed upon a grounded silicon substrate (low or high relative permittivity), electromagnetic waves will radiate and propagate out of the antenna in all directions. All the waves radiating inside the substrate will reverberate between the ground-plane and the dielectric/air interface.
Implementation Method 2
In the ubiquitous cross-coupled pair, there is inevitable tradeoff between its tuning range, output power and phase noise, especially when additional buffers and passive multipliers are used to drive the antenna at harmonics of the generated fundamental.
Implementation Method 3
Subharmonic injection locking can be area and power efficient, but still requires lower (but mm-wave) LO distribution that consumes area, power and do not scale in 2D so easily.
Data Source
AI summary
Technique for improving efficiency of on-chip antennas, comprising placing each antenna on an individual area on the chip, defined by channels provided in the chip before or after placing the antenna(s). The channels may be metallized. Frequency of a radiating antenna element may be locked by wireless injection locking using a locked subharmonic frequency.