Grounding for high frequency active circuits and in rf packages

[abhijitrc]

HI,

I just want to share one of my observation during characterization of RF package of the receiver operating at ku-band, i have faced oscillations once the required bias is given(rf is switched off). The bias network consist of quarter wave length transformer and a radial stub. Bias have been provided to LNA and the succeeding amplifiers( Here in our package Rf section consist of LNA and two amplifiers and they have been cascaded and each stage has a gain of 9 dB) through a sequential bias network and also proper feed throughs have been provided at the walls of the package, my observations are:

a. Oscillations arises once the required DC have been provided to each amplifier circuits( even others are turned off).

b.I have seen that with proper wire routing ( wire has to run through the base of the package) from feed-through to the bias network but along with that we have to place absorbers around the feed-throughs to kill the kind of DC oscillations .

c. Without absorbers near feed-throughs we are not able to supress the oscillations, since absorbers near the feed-throughs are not a good option, kindly suggest a permanent remedy , Plz hepl me!! waiting for an help.!!!!!

 

[chuckey]

Replace feed throughs with low pass filters in same package, put ferrite beads on leads?
Frank

 

[abhijitrc]

Replace feed throughs with low pass filters in same package, put ferrite beads on leads?
Frank

Actually by feedthrough i mean to state that this is bolt style EMI filters( AVX KYOCERA MAKE),but how can i put ferrite beads on the leads?? Actually how it will hepl??

- - - Updated - - -

Replace feed throughs with low pass filters in same package, put ferrite beads on leads?
Frank

Actually by feedthrough i mean to state that this is bolt style EMI filters( AVX KYOCERA MAKE),but how can i put ferrite beads on the leads?? Actually how it will hepl??

- - - Updated - - -

Replace feed throughs with low pass filters in same package, put ferrite beads on leads?
Frank

BY feed -throughs i mean to say that these are bolt syle EMI filters, and what type of ferrite beads i could put on the leads?? any specific part number? name of the manufacturer??? Kindly suggest me??

- - - Updated - - -

Replace feed throughs with low pass filters in same package, put ferrite beads on leads?
Frank

BY feed -throughs i mean to say that these are bolt syle EMI filters, and what type of ferrite beads i could put on the leads?? any specific part number? name of the manufacturer??? Kindly suggest me??

- - - Updated - - -

Replace feed throughs with low pass filters in same package, put ferrite beads on leads?
Frank

BY feed -throughs i mean to say that these are bolt syle EMI filters, and what type of ferrite beads i could put on the leads?? any specific part number? name of the manufacturer??? Kindly suggest me??

 

[chuckey]

Ferrite beads put some inductance into the leads thus increasing their impedance at RF. They are also "lossy", that is the inductance appears to have a high DC resistance which stops them resonating with any capacitance.
Frank

 

[vfone]

Add some series resistors to the quarter wave TL and might solve the problem. Check their values to meet the linearity requirements of your amplifiers.

 

[abhijitrc]

Do u know any manufacturer supplying ferrite beads?? What type of ferrite beads i can use in my configuration?? kindly help me, so that i could purchase that purchase that particular.

 

[Borber]

You may try to glue some conductive foam under the box cover. Such is black foam for ESD protection of sensitive semiconductors. It acts like absorber to EM field inside the box.

 

[abhijitrc]

Ferrite beads put some inductance into the leads thus increasing their impedance at RF. They are also "lossy", that is the inductance appears to have a high DC resistance which stops them resonating with any capacitance.
Frank

By placing the ferrite beads on the leads of low pass filters(since ferrites are slightly conductive), is there any chances of hazards!!

 

[abhijitrc]

Replace feed throughs with low pass filters in same package, put ferrite beads on leads?
Frank

Dear sir,

I had applied the technique of putting ferrite beads on the leads of low pass filters but satellite receivers it has to go to vibration test, hence putting ferrite beads on the leads will not work in that condition, is there any alternative approach ??? can i use enamel copper wire !!!, is there any other way to increase the impedance at RF?? Plz guide me , as technique of implementing ferrite bead in the leads of low pass filter works greatly , if we do not put the receiver into vibration, but vibration is mandatory for satellite receiver!! Wanting a great help!!!!