These are almost always custom designed to meet a customer’s specific requirements. An IMA can be as simple as integrating a limiting function with an LNA to meet specific needs such as noise figure, gain, intercept point, and front end protection. A more complex assembly could be comprised of a RCVR front end, PA, T/R switch, filtering and up/down convert stages. The IMA offers the customer a single package that has all the component parts matched to one another in a usually smaller volume than if the components were interconnected individually.
Control products alter a signal in amplitude or phase or a signal’s path in a system. They include Attenuators Programmable & Fixed, Phase Shifters, Limiters, Switches Resistors, Terminations.
Attenuators reduce a signal’s amplitude frequently in fixed increments without altering any other of the signal’s characteristics such as phase or frequency. Attenuators can be implanted using PIN diodes to vary the attenuation continuously or through fixed attenuator ships often made on AlN. Some attenuator design will use PIN diodes to switch fixed attenuator chips to provide a step attenuator function. Power dissipation is an important consideration in attenuator selection, dissipation levels are available from fractions of a Watt in SMT chip packages to Kilowatts in air cooled finned housings and water cooled for very large amounts of power.
A phase shifter can be characterized as a linear two port device which alters the phase of its output signal in response to an external electrical command. (Mechanical phase shifters are not considered here.) Expressing this mathematically, with an input signal sin (ωt), the output will be A(n)*sin[(ωt+Θ(n)], where n is the programmed phase and A(n) is the insertion loss. The difference between the input phase and the output phase is the sum of the phase shift due to the propagation through the phase shifter plus the programmed phase shift.
The relative simplicity of the idea that any reactance placed in series or shunt with a transmission line will produce a phase shift has given rise to many different circuits over the years for use as phase shifters at microwave frequencies.
Usually, for high speed applications, the controlling elements have been semiconductor devices such as PIN, Schottky and varactor diodes, whereas for high power requirements, when slower switching speed can be tolerated, ferrites are frequently employed. The final choice of a phase shifter network and control element will depend on the required bandwidth, insertion loss, switching speed, power handling, accuracy and resolution. In addition, a choice between analog and digital control must also be made.
Analog phase shifters are devices whose phase shift changes continuously as the control input is varied and therefore offer almost unlimited resolution with monotonic performance. The most commonly used semiconductor control devices used in analog microwave phase shifters are varactor diodes, which act as current controlled variable resistors. Schottky diodes and ferrite devices are also used as variable elements in analog phase shifters but the former suffer from limited power handling capability and matching difficulty in broadband networks whereas the latter are generally larger, require more bias power, and are relatively slow compared to semiconductor designs.
Microwave & RF Switches fall into 2 basic catagories, electro-mechanical and solid state.
The microwave solid state switch at Kratos-MED (General Microwave) is usually implemented using PIN diodes though FET switches are becoming more widely available. There are two fundamental methods of connecting PIN diodes to a transmission line to provide a switching function: in series with the transmission line so that RF power is conducted when the PIN diode is forward biased and reflected when reverse biased; or in shunt with the transmission line so that the RF power is conducted when the diode is reverse biased and reflected when forward biased. A simple reflective SPST switch can be designed utilizing one or more PIN diodes in either configuration.
A multi-throw microwave switch essentially consists of combination of SPST switches connected to a common junction and biased so that each switch port can be enabled individually. The common junction of the switch must be designed to minimize the resistive and reactive loading presented by the OFF ports in order to obtain low insertion loss and VSWR for the ON port. There are two basic methods of realizing a multi-throw microwave switch common junction for optimum performance over a broad frequency range. The first employs series mounted PIN diodes connected to the common junction. A path is selected by forward biasing its series diode and simultaneously reverse biasing all the other diodes. This provides the desired low-loss path for the ON port with a minimum of loading from the OFF ports. The second method utilizes shunt mounted PIN diodes located a quarter wavelength from the junction. The diode(s) of the selected ON port is reverse biased while the OFF ports are forward biased to create a short circuit across the transmission line. As a result of the quarter wavelength spacing, the short circuits are transformed to open circuits at the junction. By proper choice of transmission line impedances and minimization of stray reactance it is possible to construct a switch of this type with low insertion loss and VSWR over a three to one bandwidth.
Relcomm Technologies : www.relcommtech.com
RelComm Technologies, established in April 1994, designs and manufactures Design Enhanced Application Specific RF Coaxial Relay Products for high volume commercial telecommunications infrastructure, military communications as well as test and measurement instrumentation operating from DC to 40 GHz. The management team has more than seventy-five years of combined experience in design, manufacturing and marketing of products for this industry. At RelComm Technologies we believe in understanding the total opportunity. This means targeting the goals of our customers, achieving those goals, establishing long term relationships that are mutually beneficial, and then, exceeding all expectations.
Typical electro mechanical switch specifications
Switches are offered in surface mount, SMA and N connector packages
|Nominal Impedance (Ohm)||50|
|Frequency Range (GHz)||DC – 1||1 – 2||2 – 4||4 – 8||8 – 12||12 – 18||18 – 26.5|
|Insertion Loss (dB max)||0.1||0.15||0.20||0.3||0.4||0.5||0.6|
|Isolation (dB minimum)||80||75||70||70||60||60||50|
|Operating Temp. Range||-30 to +85°C|
|Storage Temp. Range||-55 to +100°C|
|Nominal Operating Coil Voltages||5, 12, 15, 24, 28 VDC|
|Nominal Impedance (Ohm)||50|