HOME

TheInfoList



OR:

An RF probe is a device which allows
electronic test equipment Electronic test equipment is used to create signals and capture responses from electronic devices under test (DUTs). In this way, the proper operation of the DUT can be proven or faults in the device can be traced. Use of electronic test equipmen ...
to measure
radio frequency Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around to around . This is roughly between the uppe ...
(RF) signal in an
electronic circuit An electronic circuit is composed of individual electronic components, such as resistors, transistors, capacitors, inductors and diodes, connected by conductive wires or traces through which electric current can flow. It is a type of electri ...
.


History

In 1980 Reed Gleason and Eric Strid invented the first high frequency wafer probe while working at Tektronix. They later went on to found Cascade Microtech in 1983. RF energy may be challenging to measure for one or more reasons, depending on the nature of the circuit to be measured and the measuring equipment at hand. The first kind of difficulty arises when the RF energy to be measured is at a
frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from '' angular frequency''. Frequency is measured in hertz (Hz) which is ...
too high for available test equipment, such as a low-bandwidth oscilloscope, to process directly. In that case, the RF has to be converted to a DC or near-DC signal. In this situation, a simple probe type sometimes called an RF detector can be used to convert the RF signal to DC. Such device will work as a RF
rectifier A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. The reverse operation (converting DC to AC) is performed by an inve ...
and give a pulsed DC
volt The volt (symbol: V) is the unit of electric potential, electric potential difference ( voltage), and electromotive force in the International System of Units (SI). It is named after the Italian physicist Alessandro Volta (1745–1827). D ...
age. The second kind of difficulty arises when RF energy has to be measured in a circuit which is sensitive to small changes in its electrical environment. For example, with some oscillator circuits, the presence of an ordinary wire within a few centimeters of the active components may change the amplitude or frequency of oscillations, or even prevent the circuit from oscillating at all. In that case, the signal has to be acquired by a measurement probe which extracts very little energy from the circuit. This can be achieved by employing very thin conductors, or tiny coils kept at some minimum separation from the active elements of the circuit. In a situation, where circuit loading rather than high frequency is the real problem, a variety of small-geometry,
high impedance In electronics, high impedance means that a point in a circuit (a node) allows a relatively small amount of current through, per unit of applied voltage at that point. High impedance circuits are low current and potentially high voltage, whereas l ...
probes can be used, sometimes including an
amplifier An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It may increase the power significantly, or its main effect may be to boost th ...
to boost the tiny amount of energy extracted from the circuit to a level that allows it to be measured by available high-frequency test equipment. Coaxial structures with spring-loaded inner and outer conductors can serve as an RF probe for modern communication electronics. Such probes are for instance being used in mass-production, in-line testing of communication electronics such as mobile phone industry. RF probes are especially relevant for switches and RF traces in printed circuit boards as well as terminations of RF components. In such systems, like many other RF circuits, there is a higher requirement of matching probe impedance with that of the DUT. Efficient matching avoids reflection which in turn leads to efficient power transfer. The second challenge to keep the power transfer efficient, is to keep the insertion loss as low as possible. Optimizing these parameters generally gets more challenging as the frequency increases.


References

* The Encyclopedia of Electronic Circuits by Rudolf F. Graf, William Sheets. Published by McGraw-Hill Professional, 1996 - , {{ISBN, 978-0-07-011275-9


External links


Post to sci.electronics.design
Radio electronics Electronic circuits Electronic test equipment