A TEMPERATURE DEPENDENT PIN DIODE MODEL FOR SIMPLE TEMPERATURE INVARIANT ATTENUATOR CIRCUITS

摘要

In this article a temperature dependent equivalent circuit of a forward-biased PIN diode is discussed. Using this equivalent circuit, the temperature behavior of a PIN diode attenuator circuit is analyzed and test results are presented. A novel control circuit is also offered for temperature invariant variable attenuation over a very wide range of temperature. This proposed circuit uses no separate temperature sensor or compensating mechanism, but responds directly to the junction temperature of the PIN diode. The junction temperature of the PIN diode modifies the diode current in such a way that its RF resistance remains invariant over the temperature range. This prevents any errors caused by temperature gradients, or by self-heating of the diodes due to high RF levels. PIN diodes have been widely used in various microwave and RF applications wherever an electronically variable RF resistance is re- quired, such as in variable attenuators, phase shifters, linearizers, variable gain amplifiers, electronically steered array antennas, etc. In general, a PIN diode's RF resistance is controlled by adjusting the bias current, since it is known that a PIN diode works as a current-controlled device. Under constant current bias conditions, however, the RF resistance of commercially available PIN diodes varies with temperature, which results in the RF attenuation also varying with temperature.