The Schottky diode, named after German physicist Walter H. Schottky, is a semiconductor diode formed by the junction of a semiconductor with a metal. It has a low forward voltage drop and a very fast switching action. Compared with the point contact diode used in similar applications, the zero bias Schottky diode has a wider dynamic range, increased thermal stability, and more accurate square law response. Zero bias Schottky diodes are used in precision testing equipment, transmitter, power, signal monitoring, missile guidance systems, and as microwave power detectors.
The zero bias Schottky diode detector is a type of RF power detector that does not need a bias voltage to operate and is widely used in RFID and other applications where no primary (DC) power is available in the standby or listen mode. Thus, power efficient or passive operation systems can use these detectors and forgo the large energy storage systems, DC bias, or low-power receiver circuitry. In this way, the zero bias Schottky diode detector is ideal for RFID tag applications where it can be combined with a simple antenna to form a receiver and, although it lacks the sensitivity of the superheterodyne receiver, it offers the advantages of reduced cost and zero power consumption. Although seemingly cost-effective, the performance of the zero bias Schottky diode detector is dependent upon its saturation current, frequency, temperature, DC bias, and ideality factor which, at both low and high temperature extremes, can lead to degradation in performance.
The zero bias Schottky diode detector has an established use in the detection of power at mm- and submm-wavelengths allowing for effective detection and mixing of electromagnetic radiation in the range through microwave to terahertz. These diode detectors can operate at ambient or cryogenic temperatures and have much faster response time when compared with room temperature detectors, such as Golay cells, pyroelectric detectors, or bolometers. When the diodes are optimized to have a low forward turn-on voltage, these detectors can achieve excellent frequency response and bandwidth, even with zero-bias.
Although the zero bias Schottky diode is less sensitive than alternative superconducting detectors, they generally do not require cooling and that makes them the devices of choice for applications where sensitivity is less of a priority. In the emerging field of terahertz technology, there is a need for cost-effective detectors for laboratory use as well as for serial compact and midsize instruments. Modern zero bias Schottky diode detectors are designed for use in power measurements, analyzing radar performance, leveling pulsed signal sources, AM noise measurements, microwave system monitoring, and in ultra-broadband and mm-Wave applications.
Commonly packaged in either inline coaxial barrel connectors, or waveguide-to-coaxial packages for millimeter-wave applications, zero bias Schottky diode detectors are typically compact and less expensive than other RF detector devices. Their simple construction also lends these devices to being relatively rugged and stable over a wide range of temperatures.
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