filter types between antenna and LNA?

[7rots51]

types of lna

What filter types is used between receiver antenna and LNA ?

what is thier typical insertion loss and selectivity?

which companies make them?

how to make them and plzzzz pdf about them?

 

[khouly]

sfdr and pre-lna filter

in CDMA mobiles the duplexer is always SAW , with very high selectrivity and about 2 dB insersion loss

khouly

 

[7rots51]

200mhz lna

what is used for non-ISM non-GSM bands?

 

[Azulykit]

The answer to such a general question is also general. A band pass filter is usually present to keep out of band signals from saturating the LNA and compressing the desired signal. The insertion loss is usually as low as cost and size will accommodate to minimize the impact on noise figure.

 

[A.Anand Srinivasan]

the filter used is bandpass filter... the insertion loss is generally made to be as low as 1-2dB but even this has some effect as it becomes the first stage in the cascade of systems....

 

[7rots51]

what topology for BPF is used? microstrip filters or LC?

what is the most used topologies?

 

[A.Anand Srinivasan]

it depends on the frequency range to be filtered.... mostly the signal is downconverted and then filtered...

 

[sergio mariotti]

I think You should provide more details or requirements. Whithout more details the answer may be "it depend !"

I suppose such filter are used to prevent intermodulation of LNA.
If the low noise is a non-compromise request, you may place the filter just after a small gain LNA rather than fron-end.
I.e a 10 dB Gain LNA followed by a good but non excellent BPF may set the IIP3 in the +5...+10dBm range, wich is an excellent value.

Otherwise, as example, for professial use (I mean cost effective), a very low loss filter may be used, largest size combline, or waveguide, may loose less than 0.5dB for 30% BW.
One of the most exotic solution is the use of cryogenerator to cool down both a superconductive filter and the LNA. But, at present, the SC filter may be designed only with moderate BW and it's non-linear for very strong signals.

 

[A.Anand Srinivasan]

I think You should provide more details or requirements. Whithout more details the answer may be "it depend !"

I suppose such filter are used to prevent intermodulation of LNA.
If the low noise is a non-compromise request, you may place the filter just after a small gain LNA rather than fron-end.
I.e a 10 dB Gain LNA followed by a good but non excellent BPF may set the IIP3 in the +5...+10dBm range, wich is an excellent value.

Otherwise, as example, for professial use (I mean cost effective), a very low loss filter may be used, largest size combline, or waveguide, may loose less than 0.5dB for 30% BW.
One of the most exotic solution is the use of cryogenerator to cool down both a superconductive filter and the LNA. But, at present, the SC filter may be designed only with moderate BW and it's non-linear for very strong signals.

i disagree with the usage of LNA in front of the filter because it heavily lowers the IIP3 point and compromises the SFDR of the system....

 

[kushal.khanal]

hi there
i am in same confusion to to get the band pass filter for my transducer

between 39-41 khz and central frequency 40khz;
and i want to use RC filter filter i.e. passive one;

can this give acuurate filtering;

should i use this type of band pass filter before LNA;
i am using LM833 as LNA;

can anyone suggest low cost BPF(band pass filter)
suggest me somthing guys

regards

 

[7rots51]

I want to have a filter in 1500MHZ in front of LNA and 50MHZ BW,my system NF=1.5 db max.

What filter type is suitable ?
Microstrip or LC or other type?

 

[mohandes79]

it depends on your circuit specifications

 

[rogerynt]

If board size is available, I prefer to use microstrip bandpass filter due to cost issue.

If board size is limited then choose multilayer bandpass filter.

For application need very high out band suppression : choose saw filter

Rogerynt

 

[7rots51]

size and cost is not an issu.

NF is important,filters with lower loss is better.

now?

 

[zkmicrowave]

the specification of the filter between antenna and lna,may be required for the system spc.

 

[7rots51]

does microstrip filter give low loss (1db or lower ) at about 1.5GHZ ?

what about CAVITY filters?
How to design them? any link?

 

[g579]

Microstrip filters are generally higher loss filters, than cavity filters.
At 1500 MHz a 50 MHz BW, I think a cavity filter is a must, if you want a noise fig. of 1.5 dB for the filter plus LNA system.
For cavity filters, you should look for Matthaei, Young, Jones, this is an old book, but a reference not to be missed. See:

 

[7rots51]

in VHF (100-200MHZ) what filters is low loss and suitable for pre-LNA block?

LC have higher loss than 1 dB,A filter with low loss ,(Ignore custom SAW filters)

 

[khouly]

most use LC in this range even with high loss about 2 dB

khouly

 

[g579]

For 100 -200 MHz try helical filter (to be simpler a low freq. cavity filter).