I have to design for homework a filter with this requirements:
Type Bandpass
Nominal center frequency (F0) [GHz] 11.5 GHz
BW 2 dB [GHz] 11-12
Insertion loss @ F0 [dB] 4.5 max
Rejection band 30 dBc [GHz] [10-10.6;12.4-13.5]
Rejection band 40 dBc [GHz] [16-18]
Rejection band 60 dBc [GHz] [0.1-10;13.5-16]
Return Loss @ BW 2dB [dB] 10 min

Amplitude Ripple in any BW 25 MHz in BW 2dB ± 0.2 dB pK max
Phase Ripple in any BW 25 MHz in BW 2dB ± 2° dB pK max
Nominal impedance [Ω] 50

I can't understand the highlighted requirements: they seems to be not consistent.
Could help me, please?

 

The BW figure is the bandwidth at which the response drops 2 dB from the CENTER of the passband. Since all filters have some kind of Gaussian style curve, rather than an instantaneous cutoff, you have to define at which point the filter is considered "off". (By the way 2 dB is a very lax figure for most passive filters). Some filter designs specify TWO different bandwidths, such as 6 dB and 60 db. The ratio of these is known as the shape factor....generally the steeper, the better.

Insertion loss is the loss through the filter IN THE PASSBAND. Obviously you WANT a lot of insertion loss OUTSIDE the passband. But it is a general figure for the efficiency of the circuit.

Amplitude ripple is a figure for multipole filters....it is the ratio of the maximum to minimum response INSIDE the passband of the filter.

Hope this helps. There are a lot more figures that give you more detail, but these are the important ones.

Eric

 

The BW figure is the bandwidth at which the response drops 2 dB from the CENTER of the passband. Since all filters have some kind of Gaussian style curve, rather than an instantaneous cutoff, you have to define at which point the filter is considered "off". (By the way 2 dB is a very lax figure for most passive filters). Some filter designs specify TWO different bandwidths, such as 6 dB and 60 db. The ratio of these is known as the shape factor....generally the steeper, the better.

Insertion loss is the loss through the filter IN THE PASSBAND. Obviously you WANT a lot of insertion loss OUTSIDE the passband. But it is a general figure for the efficiency of the circuit.

Amplitude ripple is a figure for multipole filters....it is the ratio of the maximum to minimum response INSIDE the passband of the filter.

Hope this helps. There are a lot more figures that give you more detail, but these are the important ones.

Eric

So if I want to evaluate the minimum order of a Chebyshev filter which satisfies the requirements, should I use 0.2dB as ripple and 11-12 GHz as pass-band? Is the ripple +- 0.2 dB compared to insertion loss at central frequency?
I found that the minimum order should be 5. Am I right?

 

The BW figure is the bandwidth at which the response drops 2 dB from the CENTER of the passband. Since all filters have some kind of Gaussian style curve, rather than an instantaneous cutoff, you have to define at which point the filter is considered "off". (By the way 2 dB is a very lax figure for most passive filters). Some filter designs specify TWO different bandwidths, such as 6 dB and 60 db. The ratio of these is known as the shape factor....generally the steeper, the better.

Insertion loss is the loss through the filter IN THE PASSBAND. Obviously you WANT a lot of insertion loss OUTSIDE the passband. But it is a general figure for the efficiency of the circuit.

Amplitude ripple is a figure for multipole filters....it is the ratio of the maximum to minimum response INSIDE the passband of the filter.

Hope this helps. There are a lot more figures that give you more detail, but these are the important ones.

Eric

Another question: how can the response drop 2db in the passband if the ripple must be +-0.2dB in the same band?