The electromechanical mechanism that transfers the RF contacts from one position to another. Most Dow- Key actuators use either linear or rotary magnetic solenoids acting on a mechanical linkage to the RF contacts.
The moving magnetic member of an electro magnetic switch or relay actuator structure.
Loss of signal in transmission through a component, or transmission line, usually referring to signal amplitude or signal power, and usually measured in decibels (dB).
The width of the pass band or operating band of a component. Usually expressed as either the frequency or percentage differences between the lower or the upper relative 3 dB points of the frequency response curve.
2-5. BCD (Binary Coded Decimal)
A method of storing or transmitting numeric (0 to 9) information that uses four data elements per digit. BCD data is normally organized to represent the quantities of 1, 2, 4, or 8, although schemes exist for 1, 2, 2, 4 and other codings. The data elements used can be any combination of serial or parallel transmission or storage media, such as digital Òbits,Ó data transmission lines, etc.
A moving contact member of an RF or microwave electromechanical switch or relay that has a thin, flat configuration.
2-7. BY-PASS SWITCH
A four port switch used for inserting or bypassing a circuit element.
2-8. CHARACTERISTIC IMPEDANCE OF A TRANSMISSION LINE
The characteristic Impedance of a transmission line is defined as the ratio of the complex voltage applied to the Input of an infinitely long transmission line to the complex current that would flow in that line. It Is the Impedance that the physical dimensions of the transmission line presents to a traveling wave.
An electromagnetic transmission line composed of two concentric conductors separated by an insulating material. If the outer conductor is truly seamless, such a transmission line is characterized by having no external fields and by having no susceptibility to external fields from other sources.
An assembly consisting of one or more windings of copper ‘magnet’ wire, usually wound on a form or bobbin that provides the actuating force to an electro mechanical switch or relay’s contact assembly.
2-11. COLD SWITCHING
Switching where the RF power is removed from the contacts during switch actuation. All Dow-key Microwave switching specifications are based on cold switching conditions, at a nominal temperature of 20 Degrees C.
2-12. CONTACT BOUNCE
The intermittent and undesirable opening of closed relay contact or closing of open contacts caused by one or more of the following:
1) impingement of mating contacts; 2) Impact of the armature against the coil core on pickup, or against The backstop on dropout 3) momentary hesitation, or reversal, of the armature motion during the pickup or dropout stroke.
2-13. CONTACT RESISTANCE
The electrical resistance across closed contacts as measured at their associated external terminals.
2-14. CONTACT WIPE
The scrubbing action between mating contacts.
2-15. DECIBELS (dB)
A logarithmic expression of a ratio between two quantities (commonly voltage, current, or power). Mathematically
dB – 10 x Log (P (2)/ P(1))
In the two quantities being compared are in identical Impedances, decibels are also equal to:
dB – 20 x Log (E(2)/E(l))
Db – 20 x Log (I(2)/I(1))
Energy losses in a component due to magnet or resistive losses.
2-17. DPDT (Double-Pole-Double-Throw switch)
A switch with two inputs and four outputs. Transfers the through connection from one pair of output connectors to the other pair with actuation. May be thought of as two SPDT switches mechanically linked together.
The application of power to an actuator coil winding of an electromechanical switch or relay. Use of this word assumes enough power to operate the relay, unless otherwise stated.
A switch with an actuator that contains a spring return mechanism to provide RF connection to one selected output when no voltage is applied to the actuating terminals. Failsafe switches require continuously applied actuator voltage to maintain RF connection to any other position.
2-20. GROUP DELAY
The propagation time delay of the envelope of an amplitude modulated signal as it passes through a component. Also called time delay or envelope delay. Group delay is proportional to the slope of the phase shift response versus frequency curve. Group delay distortion occurs when the delay Is not constant at all frequencies in the passband.
2-21. HOT SWITCHING
Switching where The RF power is applied to The switch contacts during switch actuation. All Dow-Key Microwave switching specifications are based on cold switching conditions, at a nominal temperature of 20 Degrees C. Please consult Dow-Key sales and applications engineers for Hot switching specifications.
Technically described, the impedance of an electronic device or transmission line is the ratio of the complex (vector) voltage between the conductors (or their equivalent) to the complex (vector) current on the conductors (or their equivalent). Impedance is the AC (vector) equivalent of DC resistance.
2-23. INDICATOR CONTACTS
A set of auxiliary D.C. contacts which are mechanically linked to the actuator and that switch with the RF contacts. Indicator contacts are normally used with pilot lights to indicate the position of the RF contacts. They may also be used as interlock contacts or to provide status reporting to an external control system.
2-24. INPUT IMPEDANCE
The impedance measured at the input terminal of a component when it is properly terminated at its output.
2-25. INSERTION LOSS
The loss of energy attributed to any component (such as a switch, connector, filter, transmission line, etc.) which is inserted into a circuit. This loss is normally expressed in decibels (dB).
RF energy may leak from one conductor to another by radiation, ionization, capacitive coupling, or Inductive coupling. In the case of switching devices, isolation is the measurement of the power level at the unconnected RF out put(s) as referred to the power traveling between the input and the connected output. Isolation is normally specified in dB below the Input power level.
A switch with an actuator that contains a mechanism, either electrical, mechanical or magnetic, that will maintain a chosen RF contact path whether or not voltage is maintained on the control terminals after switching is accomplished.
2-28. LIFE (Mechanical)
A figure, normally expressed in the number of make-break cycles, of the number of times an electro mechanical switch or relay will operate with satisfactory electrical contact in the on position. Dow-Key Microwave specifies operating life at low power levels and no electrical erosion of the contacts, and bases these specifications on many computerized laboratory tests at various switching rates between approximately 1 and 20 cycles per second.
2-29. LOAD IMPEDANCE
The impedance that normally must be connected to the output terminal of a microwave component in order to meet the various performance specifications.
A microwave Transmission component utilizing a single conductor supported above a ground plane.
2-31. MICROWAVE FREQUENCY RANGE
Traditionally the frequencies where the electromagnetic wavelength is between 1 centimeter and 1 meter long; from approximately 3 GHz to 30 GHz. It is a portion of the electromagnetic spectrum where nearly all circuit components have dimensions that are an appreciable fraction of a wavelength. Common usage is from 1 GHz to (choose one) 12 GHz, 18 GHz 26 GHz or .40 GHz.
2-32. MISMATCH LOSS
The ratio, expressed in dB, of the incident power to the transmitted power at a load or discontinuity. A measure of loss caused by the reflection from the load or discontinuity.
2-33. MULTI-THROW / MULTI-POSITION SWITCH
A switch with one Input and more than two outputs. Standard Dow-Key multi throw switches provide up to 16 selectable outputs from a single input.
Components that translate electrical energy into optical energy, or visa versa.
2-35. POWER HANDLING CAPABILITY
The capability of a micro wave component or device to transmit a given amount of power through the device. For an electromechanical switch or relay, this is the ability to pass a given amount of RF or micro wave energy alter the contacts are closed. When electromechanical switches are used for power levels at or near their rated capacity, the RF or microwave energy should be removed during the switching cycle. Switching under power may be accomplished at significantly lower power levels, but it is difficult to establish a rating for such service because of the many external factors that affect this type of switching.
2-36. REFLECTION COEFFICIENT
A numerical ratio between the reflected voltage from a load or discontinuity and the voltage incident upon a load or discontinuity.
2-37. RETURN LOSS
The ratio, normally expressed in dB, between the power incident upon a load or discontinuity and the power reflected from the load or discontinuity. Also equal to 20 times the log of the reciprocal of the reflection coefficient.
2-38. RF FREQUENCY RANGE
The frequency range from approximately 100 KHz to 1 GHz.
2-39. RISE TIME
The length of time it takes for a step function at the output of a microwave component to move from 10% to 90% of its steady state value.
2-40. SELF DE-ENERGIZING / SELF CUTOFF
Applies to latching switches only. A switch that has the ability to disconnect the actuator drive circuit so that D.C. current will not be consumed after switching has been accomplished. Self- cutoff can be accomplished either by using mechanical contacts or integrated Circuit (IC) drive circuits.
2-41. SMITH CHART
A diagram of complex impedance expressed In reflection coefficient form and displayed in polar co-ordinates. Normalized impedance and admittance parameters, electrical length in wavelengths, standing wave ratios, and attenuation parameters are also shown as overlays to the basic reflection coefficient parameters. The Smith Chart was originally developed in approximately 1939 by Phillip H. Smith of the Bell Telephone Laboratories to aid in the solution of transmission line and waveguide impedance matching problems.
2-42. SOURCE IMPEDANCE
The output impedance of the circuit that drives the component The Impedance of the circuit that the component must work from or be tested in.
Single Pole Switch. A switch with one input and two outputs. Transfers the through connection from one output to the other output with switch actuation.
Single-Pole-Single-Throw switch, A switch with one input and one output. Provides an ON-OFF switching function with actuation.
A form of microwave transmission line comprised of a conductor sandwiched between two ground planes.
2-46. SUSPENDED SUBSTRATE
A form of microwave transmission line comprised of a conductor suspended in a microwave cavity on a thin dielectric support.
2-47. SWITCH FORM
The operational configuration of a set of electromagnetic switch or relay contacts.
2-48. SWITCHING TIME / OPERATING TIME
The total amount of time between application of the control voltage to the control or actuator terminals and the completion of contact closure, or switching, including all contact bounce (if any). Total switching time includes the following
1 – Driver Delay (If switch has an internal driver)
2- Inductive delay in the actuator coil
3- Mechanical transfer time of the HF contacts
4. Contact Bounce lime.
The release time is normally less than the switching time. Switching time can be reduced by the application of a higher than normal voltage to The actuator coil during switching (over driving). This overdrive voltage must be reduced to a voltage within the switch”s specified continuous duty range after switching is completed. Please see the Switch Applications ups and Traps section for further information. Dew-Key specifies switching time at 20 Degrees C., and nominal actuator coil voltage.
2-49. TIME DELAY
The propagation time delay of the envelope of an amplitude modulated signal as it passes through a component, also called group delay or envelope delay. line delay is proportional to the slope of the phase shift response versus frequency curve. Time delay distortion occurs when the delay is not constant at all frequencies in The passband.
2-50. TRANSFER SWITCH
A four port switch that provides two Independent pairs of HF paths. These pairs are actuated simultaneously, similar to a double pole- double-Throw switch, such That the outputs are transferred (or exchanged) between the inputs.
2-51. TRANSMISSION LINE
Technically described, a transmission line in a system of material boundaries forming a continuous path from one place to another and capable of directing the transmission of electromagnetic energy along this path. If the geometrical dimensions and material constants are identical in all transverse sections, the line Is said to be uniform.
2-52. TRAVELLING WAVES
Electromagnetic energy is carried along a transmission line in the form of guided electric and magnetic fields that comprise an electromagnetic wave. These waves are composed of electric and magnetic fields that Inter act while periodically varying with time and that also adjust their configuration to fit the material boundaries in a manner that satisfies Maxwell’s equations. When electric charges are set into motion, the magnetic field caused by the current of- moving charges and the electric field caused by the presence of charges are not established throughout space instantaneously, but travel down a transmission line at a finite Velocity. The voltage impressed by a generator on one end of a trans mission line does not reach The load connected to the far end of that transmission line Instantaneously, but travels down The transmission line at a finite velocity and reaches the load somewhat later. The velocity of propagation depends upon the medium comprising the transmission line, in which the electric and magnetic fields exist. For air-Insulated transmission lines, the velocity is nearly equal to that of light in free space. The velocity is somewhat lower in transmission lines that use a solid dielectric insulation.
2-53. VSWR (Voltage Standing Wave Ratio)
The measured ratio of the electrical field strength at a voltage maximum on a transmission line to the electrical field strength of an adjacent voltage minimum.
The distance that an electromagnetic wave travels in one complete cycle.