Filter Responses

The following graphs provide a quick reference for the frequency responses of the low-loss filters used in AML antennae. The antenna models associated with a given filter are identified in the figure captions.

Interdigital and combline filters enable low passband insertion loses to be obtained over a wide range of bandwidths from a few MHz to over 100 MHz with a rapid out of band roll-off. Unlike ceramic or SAW filters, the centre frequency is not irrevocably fixed to a predetermined value, but can be factory (re)tuned. In-house design and manufacture also enable bespoke frequency responses to be offered for limited numbers.

Figure 1. Interdigital filter for DGPS, GPS, Galileo and GLONASS reception with additional notch filtering to attenuate Inmarsat interference above 1626.5 MHz (used in AD491/AD540)
Figure 2. Comparison of Interdigital filters used in the AD491 and AD591. The latter has extreme attenuation to mitigate the effects of close range Inmarsat uplink interference within the frequency range 1626 – 1660 MHz.
Figure 3. Interdigital filter for L2 GPS and GLONASS reception over the frequency range 1164 to 1254 MHz (AD491/AD540)
Figure 4. Dual interdigital filter for the frequency range 1164 to 1254 MHz (AD591)
Figure 5. Comparison of Comb-line filter responses as used in the AD420/AD422. The red line is a response typical for the reception of DGPS spotbeam services in the frequency range 1525 to 1560 MHz, and the green line is an extended response to incorporate L1 GPS at 1575.42MHz. As an option, the broader bandwidth filter can also be factory tuned for GPS and GLONASS reception over the range 1563 to 1610 MHz
Figure 6. Interdigital filter response for Iridium band reception over the frequency range 1616.5MHz to 1626.5MHz (AD512)
Figure 7. Comparison of a comb-line filter (AD420/AD422) with a narrower band interdigital filter tuned for DGPS reception within the frequency range 1531 MHz to 1541 MHz (AD430). Two ceramics filters intended for L1 GPS reception at 1575.42MHz are shown to the right
Figure 8. Ceramic filter for DGPS, GPS, and GLONASS (AD416)
Figure 9. Ceramic filter for GPS, and GLONASS (AD416)
Figure 10. Amplifier gain and noise figure with front end interdigital filter as used in the AD430 tuned for use with DGPS spot beam services within the frequency range 1531 to 1541MHz.
Figure 11. Amplifier gain and noise figure with front end interdigital filter tuned to receive a 1546MHz DGPS spot beam service, as used in the AD431. The bandwidth was designed to allow application at 1539.9MHz and 1559MHz without retuning.
Figure 12. Gain and noise figure for amplifier with comb-line front end filter as used in the AD420/AD422 tuned for use within the range 1520 to 1559 MHz.