Multichannel RF Transceiver 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 when emitter length falls below 2 mm, 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 and an op-amp, is used to replicate 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 provided to each RF amplifier, but overall current consumption increases substantially by up to 50%
Solution Approach 1:
The biasing system is segmented into a reference branch and multiple replica branches. Each branch independently generates its bias current through local replica impedances and current mirror transistors, eliminating the need for a single high-current common source while maintaining uniformity across all RF amplifiers.
Solution Approach 2:
Instead of directly replicating a large reference bias current to each RF amplifier, the invention creates copies of the biasing circuitry using current mirror transistors and replica impedances. These copies generate equivalent bias currents locally, reducing the load on the reference current source and overall power consumption.
2Use of energy by moving object
If a small reference diode with defined current density is used to replicate bias current in each RF amplifier, then current overhead is reduced, but the smaller transistor exhibits lower than expected current density when emitter length falls below 2 mm
Solution Approach 1:
Replica impedances are introduced as intermediary elements between the current mirror transistors and the RF amplifiers. These impedances ensure that the bias current is properly established and maintained at the correct current density level, compensating for the size effects in smaller transistors and ensuring reliable uniform biasing across all amplifiers.
3Use of energy by moving object
If replica impedances with selected impedance values are used to cause smaller replica reference current, then current savings are achieved, but circuit complexity increases with additional components
Solution Approach 1:
The biasing circuit is merged with the RF amplifier structure, where replica impedances and current mirror transistors are integrated into each amplifier's biasing network. This consolidation achieves current savings while managing complexity by combining functions rather than adding separate independent circuits.
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 by distributing a smaller replica reference current to each RF amplifier, maintaining uniform biasing and improving efficiency, thereby reducing overall current overhead.
Implementation Method 1
a first current mirror transistor and a first replica impedance connected in series between the supply voltage line and the common voltage line; and a plurality of second current mirror transistors, each having a gate connected to a gate of the first current mirror transistor
Implementation Method 2
a reference current source and a reference diode connected in series between a supply voltage line and a common voltage line
Implementation Method 3
an impedance value of the first and second replica impedances is selected to cause a replica reference current through the first and second replica impedances to be smaller than a reference current from the reference current source
Data Source
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).