neazoi
Advanced Member level 6
sw3ora
Hello all,
I design a high performance ssb system for SW that I could also use for upconversion to 10GHz.
I am using the filter method with an IF of 500KHz.
I have two identical ssb filters of 501.650KHz, BW 2.7KHz, which are ok for ssb voice operation (300Hz-3KHz of audio signal).
My carrier is at 500KHz.
I use mc1496 for DSB modulator which gives -65dB carrier suppression @500KHz.
I do not know the exach response of the ssb filter but it should suppress the carrier even more, as it is outside of its limits.
1. Now the question is, can I use both filters in series to suppress even more the unwanted carrier?
Well I guess I can, but if the filter has a curve response, if I connect them in series then the output will become narrower (sharper). If from the other side the crystal filter has a more square-like response, the output will not change too much but it will filter better the unwanted carrier and sideband. Are my considerations right?
2. I consider especially phase noise, so I do not use a mixer for upconversion, but a Schottky diode doubler to get lots of even harmonics through the SW bands (ok sw is noisy by itself but I need the system for 10GHz upconversion too). Then I can keep the wanted harmonic by just using a single crystal in series, to reject others. If even harmonics considered for 500KHz, then I will have one harmonic every 500KHz. Are my considerations right?
3. what is approximately the bandwidth of a standard quartz crystal? How many KHz?
Thank you very much, these are a bit more technical questions but I cannot find many RF forums to ask.
Konstantinos Giannopoulos (SW3ORA)
Computer and Telecommunications Engineer
Director of the Greek Microwave Group (www.microwave.gr)
Hello all,
I design a high performance ssb system for SW that I could also use for upconversion to 10GHz.
I am using the filter method with an IF of 500KHz.
I have two identical ssb filters of 501.650KHz, BW 2.7KHz, which are ok for ssb voice operation (300Hz-3KHz of audio signal).
My carrier is at 500KHz.
I use mc1496 for DSB modulator which gives -65dB carrier suppression @500KHz.
I do not know the exach response of the ssb filter but it should suppress the carrier even more, as it is outside of its limits.
1. Now the question is, can I use both filters in series to suppress even more the unwanted carrier?
Well I guess I can, but if the filter has a curve response, if I connect them in series then the output will become narrower (sharper). If from the other side the crystal filter has a more square-like response, the output will not change too much but it will filter better the unwanted carrier and sideband. Are my considerations right?
2. I consider especially phase noise, so I do not use a mixer for upconversion, but a Schottky diode doubler to get lots of even harmonics through the SW bands (ok sw is noisy by itself but I need the system for 10GHz upconversion too). Then I can keep the wanted harmonic by just using a single crystal in series, to reject others. If even harmonics considered for 500KHz, then I will have one harmonic every 500KHz. Are my considerations right?
3. what is approximately the bandwidth of a standard quartz crystal? How many KHz?
Thank you very much, these are a bit more technical questions but I cannot find many RF forums to ask.
Konstantinos Giannopoulos (SW3ORA)
Computer and Telecommunications Engineer
Director of the Greek Microwave Group (www.microwave.gr)