Zero Bias Schottky Diode Detector at Temperature Extremes - App Note

The zero bias Schottky diode detector is ideal for RF/ID tag applications where it can be used to fabricate a receiver which consumes no primary power. However, its performance is heavily dependent upon its saturation current, which is a strong function of temperature. At both low and high temperature extremes, this dependence can lead to degradation in performance. The behavior of zero bias Schottky diodes is analyzed, experimental data is given, and a solution to the loss of performance at cold temperatures is presented. The zero bias Schottky diode detector [1], [2] is widely used in RF/ID and other applications where no primary (DC) power is available in the standby or "listen" mode. When combined with a simple antenna to form a receiver, it lacks the sensitivity of the superheterodyne receiver, but offers the advantages of very low cost and zero power consumption. The single diode detector is shown in Figure 1. RL is the video load resistance. L, the shunt inductance, provides a current return path for the diode, and is chosen to be large (compared to the diode's impedance) at the input or RF frequency. C, the bypass capacitance, is chosen to be sufficiently large that its capacitive reactance is small compared to the diode's impedance but small enough to avoid having its reactance load the video circuit [3].