The limiters below are available:

Technical Overview, Pin Diode Limiters

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

Applications

Limiter Specification Allowances:
Limiter specifications compromise among several different parameters,
the most important of which are:

• Frequency band,
• Input power and
• Flat leakage.

Other parameters, generally specified by the above three, are as follows:

Recovery Time:
The time period from the end of 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 then when it is totally saturated. This increase in power 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

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 it is 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.

The following formula applies for source VSWRs over 2.0:1:

PA =     ______ Ps _________,

               [1 ± (PF_L *PF_S) ] ²

where PA equals actual power,
Ps equals source power, 
PF_L equals load (limiter) power factor 0.96 typical,
and PF_S equals source power factor.
 

Other Considerations
The following information is meant to assist systems engineers in specification and usage of passive limiters:

1. The difference between the flat leakage and the 1.0 dB compression point is typically between 10 and 13 dBm, but may vary according to limiter type.
   
2. Noise of-10 dBm may be generated following the start of limiter compression. However, limiters can and usually do exhibit Signs of limiter compression can be exhibited at 0 dBm.
   
3. Limiters dissipate approximately 8% of incident power as heat. Therefore, all limiters should be attached to a heat sink whose temperature does not exceed the maximum rated ambient temperature.
   
4. Limiters are inherently broadband components. Band limitation results from DC return required in some limiter designs. Limiters with bandwidths of up to 10:1 are relatively straightforward, while those with bandwidths exceeding 10: 1 are progressively more complicated and costly.

CAUTION!  Limiters are NOT bilateral components! They have both an input and an output.  Backwards installation will cause a limiter to burn out.