GENERAL M2 GLOBAL�S standard and high power isolator and circulator goods are available in Coax, Waveguide, Drop-in, Puck, and Dual Junction configurations, within the frequency range 300 MHz to 40 GHz. All models have been optimized to meet the following parameters for many popular applications: bandwidth, VSWR, isolation, insertion loss, temperature, and size. These and other parameters could be selectively optimized for your specific application. The following is a brief description of the various parameters and available options.
VSWR VSWR, or Voltage Standing Wave Ratio, is really a measure of the signal reflected from a given port whenever a signal is used to that port. For critical applications, a Smith Chart (by having an impedance plot recorded in a specified reference plane), can be provided with each device. A typical specification for VSWR is 1.25; however, values of just one.10 can be achieved for some device configurations.
ISOLATION This parameter is used to specify overturn loss sign of an isolator, between the output and input ports. All isolators described within this catalog consist of a circulator by having an internal termination. The three parameters, isolation, VSWR, and insertion loss, have to specify electrical performance of an isolator, whereas a circulator is totally defined by its VSWR and insertion loss. Although a circulator can be created into an isolator by terminating one port, it doesn't have an intrinsic isolation value. With a termination on the third port, the isolation measured depends on the VSWR of both termination and also the circulator port. Most isolators are specified at 20 dB, but values of 26 dB can be obtained for narrow band applications.
Example: A circulator has a measured VSWR of just one.2 for those three ports. If an ideal test termination with a VSWR equal to 1.00 were put on Port 3, the resulting isolation from Port 2 to Port 1 would be the return loss equal to the circulator VSWR, in this case 20.8 dB. If an evaluation termination with a VSWR of 1.05 were placed on Port 3, the isolation from Port 2 to Port 1 would vary between 18.2 and 22.5 dB, with respect to the phase distinction between the two VSWRs.
INSERTION LOSS This parameter is used to specify the forward loss characteristics of an isolator or circulator. Most in our catalog models have an insertion loss specification between 0.2 to 0.4 dB. Many low noise systems require an isolator with as low an insertion loss as you possibly can. For these applications, the insertion loss can be minimized by utilizing low loss ferrite and dielectric materials, and by silver plating circuit elements. Insertion lack of .10 dB is routinely achieved being produced for certain device configurations.
OPERATING TEMPERATURE RANGE The operating temperature range of an isolator or circulator is restricted by the properties of magnets and ferrite materials. In general, as the operating frequencies decrease, isolator temperature sensitivity increases. Catalog units utilize temperature compensation maaterials where possible. Operating temperatures from -20 to +65�C or from -40�C to 100�C are normal, although some models are restricted to 0 to 50�C. Special temperature compensation can be provided for most units to operate from -55 to +125�C.
MAGNETIC SHIELDING Catalog units all have sufficient magnetic shielding for general handling and mounting, and could be mounted within 1/2 inch of one another (or using their company magnetic materials) without degrading electrical performance. For tighter applications (mounting in direct connection with a magnetic plate), additional shielding are usually necesary, usually increasing package size.
RFI SHIELDING Standard Models have an RFI leakage specification at close proximity of -40 dB. Special packaging and sealing methods are for sale to improve RFI shielding. Leakage values as much as 100 dB can be provided in a nominal cost. RFI leakage is usually not specified for Puck configurations.
TERMINATION RATING The termination is made to safely dissipate reverse power in to the isolator heat sink. The termination power rating ought to be specified to exceed power levels that may occur under normal or anticipated fault conditions. Maximum reverse power depends upon the customer application, but might be as high as the ability applied to the input port.
Isolators are rated for reverse power levels between 1 and 500 Watts, depending on device configuration and termination capabilities. Special design considerations are required for pulsed signals with high peak power.
POWER RATING The input capacity to an isolator or circulator can be supplied from a continuous wave (CW) or a pulsed source. In the case of a pulsed source, both peak and average power aspects of the pulse train should be specified in to determine adequate safety margins.
CW (or average) power ratings depend on frequency as well as on device configuration. Low frequency waveguide devices generally have the highest power ratings.
Isolators and circulators for top peak power applications have particular design features to prevent breakdown or arcing, which may otherwise cause permanent degradation in performance. Proper connector selection, optimized internal geometry, and encapsulation are required to maximize the peak power capacity for a particular model. Peak power levels as much as 5 kW are possible on certain models. Contingent on the peak power level and other parameters, units could be provided that will operate to altitudes well over 100,000 feet.
High peak powers may cause an increase in the insertion reduction in below-resonance designs, due to non-linearity effects of the ferrite material. This increase can occur at peak power levels considerably lower than that required for breakdown or arcing. The increased insertion loss would cause more capacity to be dissipated in the ferrite region from the device, that could result in overheating. Special ferrite materials are used to avoid this situation. Such non-linearity effects don't occur in above resonance models.
The CW power rating of an isolator or circulator is dependent upon its insertion loss, the interior geometry of the ferrite region, and the type of cooling available. The insertion lack of an isolator or circulator leads to a small fraction from the input power to be absorbed and dissipated within the ferrite region and the conductor surfaces as heat. Adequate cooling techniques are necessary to insure the ferrite material doesn't reach an excessive temperature. Mounting the unit to a heat sink is sufficient in many cases when the average power is moderate.
In high power applications, a component with a high VSWR connected to the output port of an isolator will reflect a substantial amount of power. The temperature from the ferrite region along with the internal voltage will increase, causing performance to deteriorate or arcing to happen below the rated electricity.
Isolators and circulators that meet stringent peak and average power levels require design considerations for many parameters. These include normal and worst-case load VSWR conditions and the cooling that might be required under worst of all conditions.
CONNECTORS The connectors utilized on coaxial models are N-Type or SMA female. Other connectors could be provided based on operating frequency and package size; however, certain types may cause some electrical degradation.
INSERTION PHASE Many applications require isolators and circulators to be supplied as phase matched sets. Although our catalog models are not phase matched, this selection can be provided on the specified basis. The tolerance in phase matching will depend on the particular model and size the lot to become matched. Phase matched pairs can usually be provided to within �5 degrees. Linearity of the insertion phase is also specified. It is usually defined as a deviation from the best fit straight line of insertion phase versus frequency.