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Airband Bandpass

DESIGN GOALS

The Bandpass has to attenuate unwanted frequencies (e.g. IF, Image) or other
strong carriers (outside the Airband) which would drive the LNA into saturation
and would cause unwanted IM Products.

On the other hand the Insertion Loss ( S₂₁ ) shall be as low as possible in order
not to decrease System performance (Increase of Noise Figure).

As the Filter is wide as a barn door, we decided to use a combined Highpass/Lowpass approach.

The Filter was developped using capacitively coupled Pi-Lowpass Elements.

FILTER (SIMULATION)

Using RF Sim 99 we developped the following Filter :

OPEN SCHEMATICS IN NEW WINDOW CLICK HERE

Using ideal Elements the Filter has the following Amplitude Response :

Vertical : TOP + 10 dB, 10 dB / DIV, Horizontal 50 MHz / DIV, ( DC to 500 MHz )

FILTER (REAL WORLD)

Using real Elements the Filter looks like this :

and has a Frequency Response like this :

( measured with Rohde & Schwarz FSP 3 )

COMPONENT DATA

Units are [pF] and [nH] and [mm]

The above mentioned TRIM-C 9 pF is a heirloom from my former company.

Make shure all components are HI-Q in order to achieve low Insertion Loss.
The spacing walls (see picture) avoid stray coupling at higher Frequencies.

**** Airband Bandpass ****

DESIGN GOALS

FILTER (SIMULATION)

Using RF Sim 99 we developped the following Filter :

OPEN SCHEMATICS IN NEW WINDOW CLICK HERE

Using ideal Elements the Filter has the following Amplitude Response :

Vertical : TOP + 10 dB, 10 dB / DIV, Horizontal 50 MHz / DIV, ( DC to 500 MHz )

FILTER (REAL WORLD)

Using real Elements the Filter looks like this :

and has a Frequency Response like this : ( measured with Rohde & Schwarz FSP 3 )

COMPONENT DATA

Units are [pF] and [nH] and [mm]

Name

Value

Construction Details

L1

105 nH

Diam.: 6 Wire.Diam.: 1 Spacing:1 N:7

C1

100 pF

REICHELT CY 22-2 100P

C2

23 pF

REICHELT CY 22-2 15P // TRIM-C 9 pF

L2

60 nH

Diam.: 5.5 Wire.Diam.: 1 Spacing:1 N:5

C3

24 pF

REICHELT CY 22-2 15P // TRIM-C 9 pF

C4

47 pF

REICHELT CY 22-2 47P

C5

9 pF

TRIM-C 9 pF

L3

102 nH

Diam.: 6 Wire.Diam.: 1 Spacing:1 N:7

C6

14 pF

REICHELT CY 22-2 10P // TRIM-C 9 pF

C7

100 pF

REICHELT CY 22-2 100P

C8

19 pF

REICHELT CY 22-2 15P // TRIM-C 9 pF

L4

105 nH

Diam.: 6 Wire.Diam.: 1 Spacing:1 N:7

C9

14 pF

REICHELT CY 22-2 10P // TRIM-C 9 pF

C10

56 pF

REICHELT CY 22-2 56P

C11

13 pF

REICHELT CY 22-2 10P // TRIM-C 9 pF

L5

89 nH

Diam.: 6.1 Wire.Diam.: 1 Spacing:1 N:6

C12

2 pF

TRIM-C 9 pF

C13

56 pF

REICHELT CY 22-2 56P

The above mentioned TRIM-C 9 pF is a heirloom from my former company. Make shure all components are HI-Q in order to achieve low Insertion Loss. The spacing walls (see picture) avoid stray coupling at higher Frequencies.

Your valuable comment :

Airband Bandpass

and has a Frequency Response like this :

( measured with Rohde & Schwarz FSP 3 )

The above mentioned TRIM-C 9 pF is a heirloom from my former company.

Make shure all components are HI-Q in order to achieve low Insertion Loss.
The spacing walls (see picture) avoid stray coupling at higher Frequencies.