Surface acoustic wave bandpass filters
The Frequency Control Products Group in Astrium has over 25-years experience in SAW bandpass filters, and offers a comprehensive capability, including a continuing world-class design and modelling capability, together with space-qualified manufacturing facilities, all at Stevenage, UK. A wide range of filter transfer functions are feasible, with fractional bandwidths extending from 0.01% to 100%, and centre frequencies from 10MHz to 1GHz. Low in-band amplitude and phase ripples, and high close-in stopband suppression, are also typical. SAW filters are ideal for space applications, being very compact and robust.
Features / technical details
Narrowband Quartz Filters
Analogue IF processors
UHF and L-band, bandwidth up to 5%
Low amplitude/phase/group delay ripples
Sharp cut-off, high stopband suppression
Good temperature stability
Bandwidth Switchable SAW Filters (BSSF) - filters with contiguous passbands can be electrically linked and then selected/de-selected by switching
Examples:
- 4.5 MHz at 200MHz
- 11 MHz at 312MHz
- 2.5 MHz at 160MHz
- 30 MHz at 668MHz
- 50 MHz at 1GHz
Wideband Filters
- Pre/post filters for digital signal processors
- High UHF, 5 - 30% bandwidth
- A “complementary chirp” transducer capability allows SAW filters and delay lines with >100% fractional bandwidth
- Lithium tantalate
Performance
| Frequency range | 10MHz – 1GHz |
| Fractional bandwidth | 0.01% to 5% (quartz) |
| Fractional bandwidth | 5% to >100% (lithium niobate/tantalate) |
| Inband ripple - amplitude | <0.8dB pk-pk |
| Inband ripple - phase | <5 degrees pk-pk |
| Inband ripple - group delay | <200ns pk-pk |
| Transition bandwidth | Few 100’s kHz min (passband to stopband edges) |
| Close-in stopband | 40 – 50dB |
| Far-out stopband | >-60dB |
| Size | 20 x 15 x 6mm typical |
| Temperature stability (quartz) | Parabolic, δF/F = -0.03*(T-T0)2 ppm |
| Frequency/temperature stability (lithium niobate, lithium tantalate) | Linear, 90ppm/°C, 30ppm/°C |
| Weight | 10 grams typical |
Benefits
- Radiation tolerant – total dose and prompt radiation
- Mechanically robust – to withstand launch vibration and solar panel deployment
Interfaces
- Surface mount, e.g. flatpack, DIL for PCB mounting, custom hybrid.
Environment
- G-sensitivity: <1x10-9/g
- Operating temperature: -30°C to +85°C
- Radiation tolerance: >1Mrad
Categories
Applications
- Bandpass filters for signal channelisation in satellite-based analog IF processors
- Pre- and post-processor filtering for in-orbit broadband digital processor applications
Reference customers
- Inmarsat-4
- Skynet-5
