Multichannel RF Transceiver Global Biasing With Replica Current Mirrors
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Solution Overview
Problem
Existing RF transceivers face inefficiencies due to the substantial increase in current usage and power requirements resulting from replicating a uniform biasing current across multiple RF amplifiers, with smaller transistors experiencing lower than expected current density, especially below 2 µm emitter length, making uniform biasing impractical.
Innovation Solution
A global biasing circuit with a reference current source, reference diode, and current mirror transistors, along with replica impedances, is used to distribute a smaller replica reference current to each RF amplifier, ensuring uniform biasing while reducing overall current consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a common current source provides a reference bias current replicated in each RF amplifier, then uniform biasing current is ensured across all RF amplifiers, but overall current consumption increases substantially by up to 50%
Solution Approach 1:
The patent uses a current mirror circuit to replicate the reference bias current from a single reference transistor across multiple RF amplifiers. The current mirror copies the bias current waveform from the reference transistor to each amplifier transistor, ensuring uniform biasing while consuming significantly less total current than providing separate bias sources for each amplifier.
Solution Approach 2:
The reference transistor serves multiple functions simultaneously: it generates the bias current waveform, acts as the template for the current mirror, and provides the reference signal that is replicated across all RF amplifiers. This multi-functionality eliminates the need for separate bias current sources for each amplifier, reducing overall current consumption.
2Use of energy by moving object
If a smaller reference diode is used to generate bias current through current mirroring, then current consumption is reduced, but current density falls off substantially when emitter length falls below 2 µm
Solution Approach 1:
The patent changes the physical parameters of the reference transistor, specifically maintaining an emitter length of at least 2 µm to ensure adequate current density. By adjusting this critical dimension parameter, the patent achieves a balance between reduced current consumption and maintained current density uniformity, avoiding the subthreshold effects that plague smaller transistors.
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
The solution achieves significant current savings and maintains uniform biasing across RF amplifiers, reducing power requirements and improving efficiency by distributing a replica reference current that is less than half the reference current, typically around 0.2 to 0.01 times the reference current.
Implementation Method 1
a common current source may provide a reference bias current that is replicated in each RF amplifier
Implementation Method 2
a first replica impedance connected in series between the supply voltage line and the common voltage line
Data Source
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AI summary
A multichannel RF transceiver includes a global biasing circuit (102) comprising: a reference current source (306), a reference diode (307), a first current mirror transistor (304) and a first replica impedance (310); and a plurality of second current mirror transistors (3051-N), each having a gate connected to a gate of the first current mirror transistor (304). A plurality of RF amplifiers each comprise a second replica impedance (313) connected between a biasing node (314) connected to a drain of a respective one of the plurality of second current mirror transistors (3051-N) and a first RF amplifier transistor (315) connected to an RF input (317) and to the biasing node (314). The first and second replica impedances (310, 313) cause a replica reference current (IReplicaref) through the first and second replica impedances (310, 313) to be smaller than a reference current (ICref) from the reference current source (306).