Timeline for Tuning a SAW filter?
Current License: CC BY-SA 3.0
13 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Aug 21, 2016 at 10:17 | history | tweeted | twitter.com/StackHam/status/767304577901289472 | ||
| Aug 20, 2016 at 22:12 | comment | added | Marcus Müller | the path of choice would probably really be tuning the sytem that puts your signal onto 437 MHz to put it somewhere else. | |
| Aug 20, 2016 at 22:11 | comment | added | Marcus Müller | drop the "extra LNA" idea; what you want the filter for is attenuating noise, letting through signal, to get better SNR; if you now attenuate the signal, let through the noise, you make your SNR worse, and you'd be better off without the filter/with a simpler, wider filter. | |
| Aug 20, 2016 at 22:10 | comment | added | Sam | @MarcusMüller Hmm, I hadn't really thought about adding more mixers but that would probably work reasonably well as there are some pretty narrowband SAWs out there for 433.9MHz (like 10-15dB attenuation at 437MHz at reasonable prices). The only other thing I was thinking would be to just put up with the higher attenuation and just add an extra LNA to compensate for the high attenuation after the SAW, hopefully that should still keep out most of the unwanted tones (I just gotta hope no-one nearby opens their garage door...) Oh well, looks like I've got some fiddling to do, thanks for your help. | |
| Aug 20, 2016 at 8:58 | comment | added | Marcus Müller | @Sam Hm, yeah, that's pretty true. So I'm afraid you might need to modify parts of your exisiting project to use e.g. 433.9 MHz, or you could actually add another mixer state. Assuming your signal is bound to be at 437 MHz, mixing with a 3 MHz tone should reproduce the signal at 434 MHz (and 441 MHz, but that's what you'll filter out); you might want to use a narrower SAW to also get rid of the LO's power | |
| Aug 19, 2016 at 22:24 | comment | added | Sam | @MarcusMüller Mainly because I would like to use more common SAW filters in a project, e.g. 433.9MHz is a common center frequency while 437MHz is not, and the attenuation of most 433.9MHz SAWs at 437MHz is on the order of 10dB or more. Companies like Epcos do make SAW filters at other frequencies but as you move out of the commercial market, the price tends to go up while availability goes down. | |
| Aug 19, 2016 at 20:22 | comment | added | Marcus Müller | @Sam what is the actual reason you want to tune the SAW? | |
| Aug 19, 2016 at 9:40 | answer | added | Marcus Müller | timeline score: 2 | |
| Aug 18, 2016 at 23:12 | comment | added | Sam | I was hoping I could pull the frequency by a few tenths of a percent by adjusting the matching network or some such, a full chemical etch sounds like it'd require quite a bit of prep work and some... unpleasant compounds | |
| Aug 18, 2016 at 23:01 | comment | added | EEd | I did actual work on quartz but not SAW. So, not 100% sure how a 'related process' can be practiced in SAW filter. | |
| Aug 18, 2016 at 15:21 | comment | added | user157 | @EEd, why not post that as an answer? | |
| Aug 18, 2016 at 12:38 | comment | added | EEd | Quartz crystal can increase or decrease freq, by small amount only (not a few MHz), by soaking in chemical solutions that deposit or etch the quartz mass. Wonder if similar apply to SAW as both based on some form of 'mechanical vibration'. This patent paper describes tuning by mechanical deformation. Not sure if used in practice. | |
| Aug 18, 2016 at 10:02 | history | asked | Sam | CC BY-SA 3.0 |