[time-nuts] Buffer / distribution amplifier for TCXO
Dear time nuts, Background: I have built a GPS receiver based around the SE4120L front end IC [1]. I used a KT3225 TCXO [2] at 16.3676MHz driving the front end through a 10nF series capacitor as in the example circuit in [1]. Inside the front end, this oscillator is multiplied up to form a local oscillator at 1571.2896 MHz. The 16.3676MHz signal is also divided to form a 4.0919MHz sampling clock. Digital I and Q samples then go to a DSP where the GPS signal processing is done in software. My receiver works nicely, getting it online was a boatload of fun and I'm hoping to make it available soon along with open-source software as a GPS experimenter's kit. Problem: I'd like to clock multiple receivers from a single 16.3676MHz oscillator, in order to combine measurements from multiple antennas. The clocks must be at the same frequency, i.e. from the same source, but it is not necessary that they have any particular phase relationship as phase offsets are removed in the navigation processing. What sort of distribution amplifier should I use to split the output of one TCXO into four front ends? Do I need some kind of impedance matching network? How would I go about designing that? This sort of analog/RF design is unfamiliar territory for me, though I'd like to learn. The TCXO advertises a minimum output level of 0.8Vpp into (10kohm in parallel with 10pF). The front end requires a minimum oscillator drive level of 0.2Vpp. The front end datasheet lists recommended crystal parameters including a load capacitance of 10pF (typ), although I don't know whether or not that refers to the front end input capacitance. My guess is that phase noise performance is not particularly crucial, at least by time-nuts standards. I guess it would be nice if the amplifier didn't make the phase noise significantly worse than it already is from the cheap TCXO. Many thanks, Henry Hallam [1] http://www.sige.com/support/download-form.html?dl=DST-00059_SE4120L_Datasheet_Rev_3p5_CYW_May-26-2009.pdf [2] http://global.kyocera.com/prdct/electro/pdf/tcxo/172_e.pdf ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Buffer / distribution amplifier for TCXO
Henry Hallam wrote: Dear time nuts, Background: I have built a GPS receiver based around the SE4120L front end IC [1]. I used a KT3225 TCXO [2] at 16.3676MHz driving the front end through a 10nF series capacitor as in the example circuit in [1]. Inside the front end, this oscillator is multiplied up to form a local oscillator at 1571.2896 MHz. The 16.3676MHz signal is also divided to form a 4.0919MHz sampling clock. Digital I and Q samples then go to a DSP where the GPS signal processing is done in software. My receiver works nicely, getting it online was a boatload of fun and I'm hoping to make it available soon along with open-source software as a GPS experimenter's kit. Problem: I'd like to clock multiple receivers from a single 16.3676MHz oscillator, in order to combine measurements from multiple antennas. The clocks must be at the same frequency, i.e. from the same source, but it is not necessary that they have any particular phase relationship as phase offsets are removed in the navigation processing. What sort of distribution amplifier should I use to split the output of one TCXO into four front ends? Do I need some kind of impedance matching network? How would I go about designing that? This sort of analog/RF design is unfamiliar territory for me, though I'd like to learn. The TCXO advertises a minimum output level of 0.8Vpp into (10kohm in parallel with 10pF). The front end requires a minimum oscillator drive level of 0.2Vpp. The front end datasheet lists recommended crystal parameters including a load capacitance of 10pF (typ), although I don't know whether or not that refers to the front end input capacitance. My guess is that phase noise performance is not particularly crucial, at least by time-nuts standards. I guess it would be nice if the amplifier didn't make the phase noise significantly worse than it already is from the cheap TCXO. Many thanks, Henry Hallam [1] http://www.sige.com/support/download-form.html?dl=DST-00059_SE4120L_Datasheet_Rev_3p5_CYW_May-26-2009.pdf [2] http://global.kyocera.com/prdct/electro/pdf/tcxo/172_e.pdf ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. The TCXO output waveform is presumably a clipped sinewave as required by the SE4120L? In which case a linear distribution amplifier is probably required. With only a ~3V supply available, options for the distribution amplifier topology are somewhat limited. In principle you could use an emitter follower driving 4 other emitter followers with a resistor in series with the emitters of the output devices and the AC coupled loads to match the source to the interconnecting cable impedance to minimise reflections without requiring excessive dissipation in the emitter followers. With the low voltage supply available, using an RF choke is series with the emitter follower's emitter to ground resistor will also be useful in achieving the required dynamic range. Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Buffer / distribution amplifier for TCXO
Hi I suspect you will find that the phase noise floor of the distribution system does indeed matter. Likely the easy way to go: Square the TCXO up with a biased CMOS inverter (at least as fast as a 74AC04). Run a seperate inverter to drive each of the receivers. A hex inverter chip would do it all quite nicely. There should be plenty of isolation and far more signal than is needed. Attenuating it at the receiver with a pair of resistors should get all the levels to match up. If you want to get fancy, transformer couple into each receiver after attenuating. Bob -- From: Henry Hallam he...@pericynthion.org Sent: Wednesday, August 04, 2010 1:46 PM To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: [time-nuts] Buffer / distribution amplifier for TCXO Dear time nuts, Background: I have built a GPS receiver based around the SE4120L front end IC [1]. I used a KT3225 TCXO [2] at 16.3676MHz driving the front end through a 10nF series capacitor as in the example circuit in [1]. Inside the front end, this oscillator is multiplied up to form a local oscillator at 1571.2896 MHz. The 16.3676MHz signal is also divided to form a 4.0919MHz sampling clock. Digital I and Q samples then go to a DSP where the GPS signal processing is done in software. My receiver works nicely, getting it online was a boatload of fun and I'm hoping to make it available soon along with open-source software as a GPS experimenter's kit. Problem: I'd like to clock multiple receivers from a single 16.3676MHz oscillator, in order to combine measurements from multiple antennas. The clocks must be at the same frequency, i.e. from the same source, but it is not necessary that they have any particular phase relationship as phase offsets are removed in the navigation processing. What sort of distribution amplifier should I use to split the output of one TCXO into four front ends? Do I need some kind of impedance matching network? How would I go about designing that? This sort of analog/RF design is unfamiliar territory for me, though I'd like to learn. The TCXO advertises a minimum output level of 0.8Vpp into (10kohm in parallel with 10pF). The front end requires a minimum oscillator drive level of 0.2Vpp. The front end datasheet lists recommended crystal parameters including a load capacitance of 10pF (typ), although I don't know whether or not that refers to the front end input capacitance. My guess is that phase noise performance is not particularly crucial, at least by time-nuts standards. I guess it would be nice if the amplifier didn't make the phase noise significantly worse than it already is from the cheap TCXO. Many thanks, Henry Hallam [1] http://www.sige.com/support/download-form.html?dl=DST-00059_SE4120L_Datasheet_Rev_3p5_CYW_May-26-2009.pdf [2] http://global.kyocera.com/prdct/electro/pdf/tcxo/172_e.pdf ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Buffer / distribution amplifier for TCXO
On Wed, Aug 4, 2010 at 1:50 PM, Bruce Griffiths bruce.griffi...@xtra.co.nz wrote: The TCXO output waveform is presumably a clipped sinewave as required by the SE4120L? I posted the waveform at http://www.pericynthion.org/stuff/KT3225_500mV_per_div.jpg Does that count as clipped sine? If not, it seems to work anyway. In which case a linear distribution amplifier is probably required. With only a ~3V supply available, options for the distribution amplifier topology are somewhat limited. I'm making a custom board that will include the TCXO and distribution amplifier (as well as some digital stuff to allow the 4 receivers to communicate), so it can have whatever power supplies it needs. In principle you could use an emitter follower driving 4 other emitter followers with a resistor in series with the emitters of the output devices and the AC coupled loads to match the source to the interconnecting cable impedance to minimise reflections without requiring excessive dissipation in the emitter followers. With the low voltage supply available, using an RF choke is series with the emitter follower's emitter to ground resistor will also be useful in achieving the required dynamic range. Thanks. Henry ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Buffer / distribution amplifier for TCXO
The GPS receiver chip actually specifies that a clipped sinewave should be used. Presumably this is necessary to limit the harmonic contents. In which case low pass filtering the CMOS outputs may be necessary. The 74AHC04 or equivalent may be a better choice as its ground and Vcc bounce is lower than that of a 74AC04. Bruce Bob Camp wrote: Hi I suspect you will find that the phase noise floor of the distribution system does indeed matter. Likely the easy way to go: Square the TCXO up with a biased CMOS inverter (at least as fast as a 74AC04). Run a seperate inverter to drive each of the receivers. A hex inverter chip would do it all quite nicely. There should be plenty of isolation and far more signal than is needed. Attenuating it at the receiver with a pair of resistors should get all the levels to match up. If you want to get fancy, transformer couple into each receiver after attenuating. Bob -- From: Henry Hallam he...@pericynthion.org Sent: Wednesday, August 04, 2010 1:46 PM To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: [time-nuts] Buffer / distribution amplifier for TCXO Dear time nuts, Background: I have built a GPS receiver based around the SE4120L front end IC [1]. I used a KT3225 TCXO [2] at 16.3676MHz driving the front end through a 10nF series capacitor as in the example circuit in [1]. Inside the front end, this oscillator is multiplied up to form a local oscillator at 1571.2896 MHz. The 16.3676MHz signal is also divided to form a 4.0919MHz sampling clock. Digital I and Q samples then go to a DSP where the GPS signal processing is done in software. My receiver works nicely, getting it online was a boatload of fun and I'm hoping to make it available soon along with open-source software as a GPS experimenter's kit. Problem: I'd like to clock multiple receivers from a single 16.3676MHz oscillator, in order to combine measurements from multiple antennas. The clocks must be at the same frequency, i.e. from the same source, but it is not necessary that they have any particular phase relationship as phase offsets are removed in the navigation processing. What sort of distribution amplifier should I use to split the output of one TCXO into four front ends? Do I need some kind of impedance matching network? How would I go about designing that? This sort of analog/RF design is unfamiliar territory for me, though I'd like to learn. The TCXO advertises a minimum output level of 0.8Vpp into (10kohm in parallel with 10pF). The front end requires a minimum oscillator drive level of 0.2Vpp. The front end datasheet lists recommended crystal parameters including a load capacitance of 10pF (typ), although I don't know whether or not that refers to the front end input capacitance. My guess is that phase noise performance is not particularly crucial, at least by time-nuts standards. I guess it would be nice if the amplifier didn't make the phase noise significantly worse than it already is from the cheap TCXO. Many thanks, Henry Hallam [1] http://www.sige.com/support/download-form.html?dl=DST-00059_SE4120L_Datasheet_Rev_3p5_CYW_May-26-2009.pdf [2] http://global.kyocera.com/prdct/electro/pdf/tcxo/172_e.pdf ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Buffer / distribution amplifier for TCXO
Henry Hallam wrote: On Wed, Aug 4, 2010 at 1:50 PM, Bruce Griffiths bruce.griffi...@xtra.co.nz wrote: The TCXO output waveform is presumably a clipped sinewave as required by the SE4120L? I posted the waveform at http://www.pericynthion.org/stuff/KT3225_500mV_per_div.jpg Does that count as clipped sine? If not, it seems to work anyway. Its something like a clipped sine albeit with some ringing as it is clipped. It more closely resembles a low pass filtered square wave. In which case a linear distribution amplifier is probably required. With only a ~3V supply available, options for the distribution amplifier topology are somewhat limited. I'm making a custom board that will include the TCXO and distribution amplifier (as well as some digital stuff to allow the 4 receivers to communicate), so it can have whatever power supplies it needs. In principle you could use an emitter follower driving 4 other emitter followers with a resistor in series with the emitters of the output devices and the AC coupled loads to match the source to the interconnecting cable impedance to minimise reflections without requiring excessive dissipation in the emitter followers. With the low voltage supply available, using an RF choke is series with the emitter follower's emitter to ground resistor will also be useful in achieving the required dynamic range. Thanks. Henry Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Buffer / distribution amplifier for TCXO
Hi The phase noise floor of the HC is *much* higher than the floor of the AC gates. The main reason it specifies clipped sine is that's what the cheap TCXO's put out. Bob On Aug 4, 2010, at 6:42 PM, Bruce Griffiths wrote: The GPS receiver chip actually specifies that a clipped sinewave should be used. Presumably this is necessary to limit the harmonic contents. In which case low pass filtering the CMOS outputs may be necessary. The 74AHC04 or equivalent may be a better choice as its ground and Vcc bounce is lower than that of a 74AC04. Bruce Bob Camp wrote: Hi I suspect you will find that the phase noise floor of the distribution system does indeed matter. Likely the easy way to go: Square the TCXO up with a biased CMOS inverter (at least as fast as a 74AC04). Run a seperate inverter to drive each of the receivers. A hex inverter chip would do it all quite nicely. There should be plenty of isolation and far more signal than is needed. Attenuating it at the receiver with a pair of resistors should get all the levels to match up. If you want to get fancy, transformer couple into each receiver after attenuating. Bob -- From: Henry Hallam he...@pericynthion.org Sent: Wednesday, August 04, 2010 1:46 PM To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: [time-nuts] Buffer / distribution amplifier for TCXO Dear time nuts, Background: I have built a GPS receiver based around the SE4120L front end IC [1]. I used a KT3225 TCXO [2] at 16.3676MHz driving the front end through a 10nF series capacitor as in the example circuit in [1]. Inside the front end, this oscillator is multiplied up to form a local oscillator at 1571.2896 MHz. The 16.3676MHz signal is also divided to form a 4.0919MHz sampling clock. Digital I and Q samples then go to a DSP where the GPS signal processing is done in software. My receiver works nicely, getting it online was a boatload of fun and I'm hoping to make it available soon along with open-source software as a GPS experimenter's kit. Problem: I'd like to clock multiple receivers from a single 16.3676MHz oscillator, in order to combine measurements from multiple antennas. The clocks must be at the same frequency, i.e. from the same source, but it is not necessary that they have any particular phase relationship as phase offsets are removed in the navigation processing. What sort of distribution amplifier should I use to split the output of one TCXO into four front ends? Do I need some kind of impedance matching network? How would I go about designing that? This sort of analog/RF design is unfamiliar territory for me, though I'd like to learn. The TCXO advertises a minimum output level of 0.8Vpp into (10kohm in parallel with 10pF). The front end requires a minimum oscillator drive level of 0.2Vpp. The front end datasheet lists recommended crystal parameters including a load capacitance of 10pF (typ), although I don't know whether or not that refers to the front end input capacitance. My guess is that phase noise performance is not particularly crucial, at least by time-nuts standards. I guess it would be nice if the amplifier didn't make the phase noise significantly worse than it already is from the cheap TCXO. Many thanks, Henry Hallam [1] http://www.sige.com/support/download-form.html?dl=DST-00059_SE4120L_Datasheet_Rev_3p5_CYW_May-26-2009.pdf [2] http://global.kyocera.com/prdct/electro/pdf/tcxo/172_e.pdf ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Buffer / distribution amplifier for TCXO
Is that also true for AHC devices which otherwise have similar characteristics (apart from ground bounce) to AC devices? Bruce Bob Camp wrote: Hi The phase noise floor of the HC is *much* higher than the floor of the AC gates. The main reason it specifies clipped sine is that's what the cheap TCXO's put out. Bob On Aug 4, 2010, at 6:42 PM, Bruce Griffiths wrote: The GPS receiver chip actually specifies that a clipped sinewave should be used. Presumably this is necessary to limit the harmonic contents. In which case low pass filtering the CMOS outputs may be necessary. The 74AHC04 or equivalent may be a better choice as its ground and Vcc bounce is lower than that of a 74AC04. Bruce Bob Camp wrote: Hi I suspect you will find that the phase noise floor of the distribution system does indeed matter. Likely the easy way to go: Square the TCXO up with a biased CMOS inverter (at least as fast as a 74AC04). Run a seperate inverter to drive each of the receivers. A hex inverter chip would do it all quite nicely. There should be plenty of isolation and far more signal than is needed. Attenuating it at the receiver with a pair of resistors should get all the levels to match up. If you want to get fancy, transformer couple into each receiver after attenuating. Bob -- From: Henry Hallamhe...@pericynthion.org Sent: Wednesday, August 04, 2010 1:46 PM To: Discussion of precise time and frequency measurementtime-nuts@febo.com Subject: [time-nuts] Buffer / distribution amplifier for TCXO Dear time nuts, Background: I have built a GPS receiver based around the SE4120L front end IC [1]. I used a KT3225 TCXO [2] at 16.3676MHz driving the front end through a 10nF series capacitor as in the example circuit in [1]. Inside the front end, this oscillator is multiplied up to form a local oscillator at 1571.2896 MHz. The 16.3676MHz signal is also divided to form a 4.0919MHz sampling clock. Digital I and Q samples then go to a DSP where the GPS signal processing is done in software. My receiver works nicely, getting it online was a boatload of fun and I'm hoping to make it available soon along with open-source software as a GPS experimenter's kit. Problem: I'd like to clock multiple receivers from a single 16.3676MHz oscillator, in order to combine measurements from multiple antennas. The clocks must be at the same frequency, i.e. from the same source, but it is not necessary that they have any particular phase relationship as phase offsets are removed in the navigation processing. What sort of distribution amplifier should I use to split the output of one TCXO into four front ends? Do I need some kind of impedance matching network? How would I go about designing that? This sort of analog/RF design is unfamiliar territory for me, though I'd like to learn. The TCXO advertises a minimum output level of 0.8Vpp into (10kohm in parallel with 10pF). The front end requires a minimum oscillator drive level of 0.2Vpp. The front end datasheet lists recommended crystal parameters including a load capacitance of 10pF (typ), although I don't know whether or not that refers to the front end input capacitance. My guess is that phase noise performance is not particularly crucial, at least by time-nuts standards. I guess it would be nice if the amplifier didn't make the phase noise significantly worse than it already is from the cheap TCXO. Many thanks, Henry Hallam [1] http://www.sige.com/support/download-form.html?dl=DST-00059_SE4120L_Datasheet_Rev_3p5_CYW_May-26-2009.pdf [2] http://global.kyocera.com/prdct/electro/pdf/tcxo/172_e.pdf ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Buffer / distribution amplifier for TCXO
Bruce Griffiths wrote: In which case a linear distribution amplifier is probably required. With only a ~3V supply available, options for the distribution amplifier topology are somewhat limited. In principle you could use an emitter follower driving 4 other emitter followers with a resistor in series with the emitters of the output devices and the AC coupled loads to match the source to the interconnecting cable impedance to minimise reflections without requiring excessive dissipation in the emitter followers. With the low voltage supply available, using an RF choke is series with the emitter follower's emitter to ground resistor will also be useful in achieving the required dynamic range. Bruce A more efficient buffer amplifier circuit schematic is attached. The series transformer feedback stage has high input impedance and an output impedance matched to the transmission line (yes it works well with long transmission lines as well). However a trifilar wound RF transformer is required. In principle the various GPS receivers could be connected to taps along an end terminated transmission line using feedthrough connections with compensation for the tap shunt capacitance if necessary. A lower impedance line (eg 50 ohms) could also be driven at the expense of a higher collector current. In this case the value of R3 would need to be reduced to around 100 ohms or so. Bruce attachment: TCXO_BUFFER.gif___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Buffer / distribution amplifier for TCXO
Hi It's a speed thing. The faster silicon based CMOS is , the quieter it seems to be. Bob On Aug 4, 2010, at 8:21 PM, Bruce Griffiths wrote: Is that also true for AHC devices which otherwise have similar characteristics (apart from ground bounce) to AC devices? Bruce Bob Camp wrote: Hi The phase noise floor of the HC is *much* higher than the floor of the AC gates. The main reason it specifies clipped sine is that's what the cheap TCXO's put out. Bob On Aug 4, 2010, at 6:42 PM, Bruce Griffiths wrote: The GPS receiver chip actually specifies that a clipped sinewave should be used. Presumably this is necessary to limit the harmonic contents. In which case low pass filtering the CMOS outputs may be necessary. The 74AHC04 or equivalent may be a better choice as its ground and Vcc bounce is lower than that of a 74AC04. Bruce Bob Camp wrote: Hi I suspect you will find that the phase noise floor of the distribution system does indeed matter. Likely the easy way to go: Square the TCXO up with a biased CMOS inverter (at least as fast as a 74AC04). Run a seperate inverter to drive each of the receivers. A hex inverter chip would do it all quite nicely. There should be plenty of isolation and far more signal than is needed. Attenuating it at the receiver with a pair of resistors should get all the levels to match up. If you want to get fancy, transformer couple into each receiver after attenuating. Bob -- From: Henry Hallamhe...@pericynthion.org Sent: Wednesday, August 04, 2010 1:46 PM To: Discussion of precise time and frequency measurementtime-nuts@febo.com Subject: [time-nuts] Buffer / distribution amplifier for TCXO Dear time nuts, Background: I have built a GPS receiver based around the SE4120L front end IC [1]. I used a KT3225 TCXO [2] at 16.3676MHz driving the front end through a 10nF series capacitor as in the example circuit in [1]. Inside the front end, this oscillator is multiplied up to form a local oscillator at 1571.2896 MHz. The 16.3676MHz signal is also divided to form a 4.0919MHz sampling clock. Digital I and Q samples then go to a DSP where the GPS signal processing is done in software. My receiver works nicely, getting it online was a boatload of fun and I'm hoping to make it available soon along with open-source software as a GPS experimenter's kit. Problem: I'd like to clock multiple receivers from a single 16.3676MHz oscillator, in order to combine measurements from multiple antennas. The clocks must be at the same frequency, i.e. from the same source, but it is not necessary that they have any particular phase relationship as phase offsets are removed in the navigation processing. What sort of distribution amplifier should I use to split the output of one TCXO into four front ends? Do I need some kind of impedance matching network? How would I go about designing that? This sort of analog/RF design is unfamiliar territory for me, though I'd like to learn. The TCXO advertises a minimum output level of 0.8Vpp into (10kohm in parallel with 10pF). The front end requires a minimum oscillator drive level of 0.2Vpp. The front end datasheet lists recommended crystal parameters including a load capacitance of 10pF (typ), although I don't know whether or not that refers to the front end input capacitance. My guess is that phase noise performance is not particularly crucial, at least by time-nuts standards. I guess it would be nice if the amplifier didn't make the phase noise significantly worse than it already is from the cheap TCXO. Many thanks, Henry Hallam [1] http://www.sige.com/support/download-form.html?dl=DST-00059_SE4120L_Datasheet_Rev_3p5_CYW_May-26-2009.pdf [2] http://global.kyocera.com/prdct/electro/pdf/tcxo/172_e.pdf ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
