Microwave Limiters: Application Notes

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Kratos General Microwave offers PIN diode-based limiters, supporting up to 600 watts of pulsed power.

The limiters can be supplied in various configurations: connectorized, drop-in or with field-removable connectors.

The limiters can be supplied as stand alone limiters, or as integrated modules that include the limiter and a control component such as a switch or attenuator as specified in the following:

SWITCH LIMITERS
A switch module is available in front or after the limiter, handling up to 25-watt CW/ 250-watt Peak power.

LIMITER ATTENUATOR
Provides combined protection and attenuation capabilities (Option).

LIMITER AMPLIFIER
A limiter and an amplifier module that maintains the required power. Signal is amplified if power is not within the specified range (Option).

 

Low Power Limiters

Support 1GHz – 18GHz, up to 20-Watts Average
power and 500-watt Peak power.

High Power Limiters

Support 1GHz – 12GHz, up to 60-Watts Average
power and 400-watt Peak power.

Parameters Trade-off

The main parameters of Limiter specifications are Frequency Band, Input Power and Flat Leakage. Note that there is a trade-off between these parameters.

 

  • Broadband
  • Coaxial and Drop-In Modules
  • High-Power Ratings

Medium Power Microwave Limiter

Medium Power Limiter

High Power Microwave Limiter

High Power Limiter

Switch Microwave Limiter

Switch Limiter

 

 

 

DEFINITION OF PARAMETERS

Recovery Time:

The time period from the end of a high power pulse to the point where the insertion loss value has returned to within 3 dB of the quiescent loss state.

Spike Leakage:

After pulsed high power is applied, the limiter will momentarily pass significantly more power than when it is totally saturated. This power rise is seen as a spike on the leading edge of the leakage pulse. The rise time of the high power pulse and the turn-on time of the diode determine the spike’s amplitude. The spike is defined by its energy content, i.e., in ergs. The formula for calculating the spike leakage is as follows:

          SPIKE LEAKAGE (ERGS) = ts x Ps x 107 

where ts equals spike width at the half-power point in seconds, and Ps equals maximum spike amplitude in watts.

Spike Leakage

Power Handling:

There are two important things to consider when defining the power handling required of a limiter. Two important considerations for defining the required power handling of a limiter are:

  • Peak Pulsed Power: for narrow pulses, equated to an equivalent CW power by multiplying the Peak Power  by the Duty Cycle. For pulses exceeding 10 microseconds, Peak Power is considered CW
  • Source VSWR: When is it fully turned on, the Limiter short circuits across the transmission line, and 90% incident power is reflected back towards the source.  

Any mismatch at the source reflects power back toward the limiter, resulting in standing waves.  In a correct limiter-source phase relationship, the maximum current point occurs at the input diode, causing the diode to dissipate a greater level of power than incident power.  For a source VSWR of up to 2.0:1, an approximate maximum effective power can be achieved by multiplying the source VSWR by the incident power.

 

      CONSIDERATIONS IN USING LIMITERS

  • The difference between the flat leakage and the 0.1 dB compression point is typically between 10 and 13 dBm, but may vary according to limiter type
  • Noise of 10 dBm may be generated following the start of limiter compression. However, limiters can and usually do exhibit signs of limiter compression at 0 dBm
  • Limiters dissipate approximately 8% of incident power as heat. Therefore, all limiters should be attached to a heatsink whose temperature does not exceed the maximum rated ambient temperature
  • Limiters are inherently broadband components. Band limitation results from DC return are required by some limiter designs. Limiters with bandwidths of up to 10:1 are relatively simple, while those with bandwidths exceeding 10: 1 are progressively more complex and costly.

CAUTION! Limiters are NOT bilateral components! They have a defined input and output.  Backwards installation will damage the component.

 

 

 

ENVIRONMENTAL RATINGS
Operating Temperature
Range.................................
­–55°C to +85°C

Non-Operating
Temperature Range....... 

–55°C to +85°C
Humidity............................. RTCA/DO-160D, Category B Sec. 6.3.2).
RH Operating 95% @ 60 oC
Shock................................. RTCA/DO-160D Section 7 Category B
Vibration............................ RTCV/DO-160D Category R or R2 Sec conde,) Section 8, Par. 8.7.2 Fig. 8-1 & 8-4. Curve C & C1, G rms 4.12 & 5.83.
Random 30 min at performance level and 3 Hrs at endurance level for each axis.
Altitude................................ (70,000 ft.)
Temp. Cycling.................... MIL-STD-202F, Method 107D, Cond. A, 5 cycles

Approved for Public Release - DoD DOPSR Case No. 14-S-0622
 

 

 

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