C-Band Low Pass Filter

Status date

The main objective of the program was the qualification of a very high power C-band low pass filter for telecom or TT&C application, with high rejection up to Ku band and compact design construction.


The complete design was done in silver plated aluminium plus some plastics.


Corona was tested at ESA up to 180w, multipactor up to 500w and CW up to 120w (thermal environment at 80º) without degradation.


Main filter performances are:

Performance Measured Value
1. Frequency (MHz) 3680 - 4220
2. Insertion Loss (dB) <0.5
3. GD variation (ns) <0.2
4. VSWR <1.25 : 1
5. Out of band rejection. MHz                 dB
5825-5850       -60
5850-6725       -80
6725-7050       -65
7850-7950       -60
10750-14500    -60
15750-15850    -60
6. Power Handling (W)

160W Corona
500W Multipactor.
120W CW

7. Dimensions 145x73x35mm
8. Mass <250g

click for larger image


The main issue was to achieve a design capable to work at high power level without any degradation.


TWT state of art is moving quite quickly in the last years to very high power levels. The passive equipment associated to TT&C or channel paths need then to be adapted to the new requirements. This filter can work in high temperature environment (80º) up to 80-100W power input without any degradation.


The Feed consists of two stages: a band pass one, designed in ridge port technology, and a low pass, designed in corrugated ridge technology. The full structure is folded to reduce its lay-out, and input/output are mounted at 90º to facilitate its connectivity.


The develop plan was performed in three main phases; the design of the two filter stages and interaction determination, its manufacturing, tuning process and, finally, the qualification of the assembly, including all high power test.

Current status

The equipment today is fully qualified. The program is finished.