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Design
A minimal footprint of the RF current source can be found in RF-VtoI.sch and RF-VtoI.brd. The RF-VtoI eagle files are designed to be imported into another eagle project that contains the PCB antenna design (see RF_antenna.brd and RF_antenna_B.brd for examples). The output of the current feedback amplifier just needs to be connected to Rs via a PCB trace that defines the antenna.
The Qucs simulations contained in RF_VtoI_prj can help with selection of component values. If you already have an antenna designed, the simulations can also help determine how well the RF current source can drive it. Note that the AC simulations in RF_VtoI_prj linearize the system and do not account for saturation effects. Therefore, the simulation output is only reliable for low drive currents (low control voltages).
The Qucs files have been updated to allow transient simulations (which do not linearize the circuit). We have found that the transient simulations give better agreement with experimental data and allow estimation of saturation effects. Non-linear effects seem to increase in importance when operating an antenna near the current-feedback amplifier's corner frequency. Simulations of low-inductance antennas should therefore use transient simulations to choose component values. The transient simulations are much slower than AC simulations, so they should be deployed after using AC simulations to gain some intuition for the behavior of the RF current source with a new antenna.
To get the best performance, Lg must have a high self-resonant frequency. We have found that chip inductors from Coilcraft yield good performance. The pads on our circuit are for Coilcraft's 1008 chip inductor package.