Balanced Frequency Doubler Topology Without Transformer Baluns
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Solution Overview
Problem
Current frequency doublers are either unbalanced, leading to 1/f noise impairment and local oscillator leakage, or they suffer from inefficiencies due to the use of transformer baluns, and there is a lack of truly balanced frequency doublers without unbalanced nodes in the literature.
Innovation Solution
A balanced frequency doubler design comprising two push-push frequency doubler units arranged in parallel, with phase-shifted input signals generating second harmonic frequencies, and the output signal formed by the difference between voltage drops across electrical loads, ensuring balanced operation without unbalanced nodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a common-source circuit with matched second harmonic is used for frequency doubling, then the circuit is simple to implement, but it produces unbalanced output with low fundamental rejection and output power lower than 0 dBm
Solution Approach 1:
The frequency doubler is divided into two separate push-push doubler units operating in parallel, each handling specific phase inputs. This segmentation allows balanced operation while maintaining implementation simplicity, resolving the contradiction between ease of manufacture and output performance.
Solution Approach 2:
Two push-push doubler units are merged in parallel configuration with their outputs combined through voltage subtraction. This merging achieves balanced output with high fundamental rejection and output power above 0 dBm, while keeping each individual unit simple to implement.
2Reliability
If a transformer balun is added to a push-push doubler to achieve balanced output, then balanced signaling is obtained, but transformer losses reduce efficiency and add device complexity
Solution Approach 1:
The transformer balun component is completely removed from the circuit. Instead, balanced output is achieved by directly combining the outputs of two push-push doubler units through voltage subtraction, eliminating transformer losses while maintaining balanced signaling.
Solution Approach 2:
The mechanical transformer-based balancing approach is replaced with an electrical voltage subtraction method. This substitution eliminates the physical transformer and its associated losses, achieving balanced output through circuit topology rather than magnetic coupling.
3Device complexity
If a single Gilbert cell is used for frequency doubling, then integration is achieved, but truly balanced signaling with both amplitude and phase balance cannot be accomplished
Solution Approach 1:
The frequency doubling function is segmented into two separate push-push doubler units instead of one integrated Gilbert cell. Each unit processes specific phase inputs and their outputs are combined to achieve both amplitude and phase balance, resolving the limitation of single-cell approaches.
Solution Approach 2:
The solution moves from a single-plane integrated Gilbert cell to a two-dimensional parallel configuration of push-push units. This dimensional expansion enables simultaneous achievement of amplitude and phase balance while maintaining integration through shared biasing and compact layout.
4Power
If unbalanced or pseudo balanced local oscillator signal generation is used, then output power can be achieved, but local oscillator leakage increases risking receiver performance
Solution Approach 1:
The circuit uses symmetric balanced operation with two push-push units producing equal and opposite outputs. This symmetric design inherently cancels local oscillator leakage, achieving high output power above 0 dBm without the harmful leakage effects of unbalanced designs.
Data Source
AI summary
The invention inter alia relates to a balanced frequency doubler comprising a first frequency doubler unit providing a first input port and a second input port, a second frequency doubler unit providing a third input port and a fourth input port, wherein the first, second, third and fourth input port are configured to receive a first, second, third and fourth input signal, respectively, wherein the first, second, third and fourth input signals all have the same first harmonic frequency, but are phase-shifted relative to one another, wherein a first current, the frequency spectrum of which comprises a second harmonic frequency that is double the first harmonic frequency, is driven through the first frequency doubler unit in response to the first and second input signal, wherein a second current, the frequency spectrum of which also comprises the second harmonic frequency, is driven through the second frequency doubler unit in response to the third and fourth input signals, and wherein a balanced output signal of the frequency doubler is influenced by the first and second current.