Digital bandwidth
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From: billoo on 25 Jul 2006 10:36 Hi I am currently working on a project which involves determining the relationship between the the "bandwidth"(as my advisor puts it) and power consumption of an I/Q transmitter. The I/Q transmitter works as follows: In-Phase: Even bits of PN sequence ---> DAC ---> LPF --> multiply by cosine --> transmit Quad-Phase: Odd bits of PN sequence --> DAC --> LPF --> mult. by sine --> transmit The problem is that my advisor wants me to see how the power consumption changes as you change the bandwidth of the input data (the PN sequence). I have a power model and a power estimator worked out nicely for the transmitter itself. However, I dont know what he means by changing the bandwidth of the input data. Does it mean that I change the pattern of 1s and 0s or just increase/decrease the number of bits (resolution) of the PN sequence? Please help, I have come this far working hard on my simulator and I dont want to stop short just on something small I don't understand for the simulation itself. Thank You Mohammed Billoo
From: Jerry Avins on 25 Jul 2006 11:42 billoo wrote: > Hi > > I am currently working on a project which involves determining the > relationship between the the "bandwidth"(as my advisor puts it) and > power consumption of an I/Q transmitter. The I/Q transmitter works as > follows: > > In-Phase: Even bits of PN sequence ---> DAC ---> LPF --> multiply by > cosine --> transmit > > Quad-Phase: Odd bits of PN sequence --> DAC --> LPF --> mult. by sine > --> transmit > > The problem is that my advisor wants me to see how the power > consumption changes as you change the bandwidth of the input data (the > PN sequence). I have a power model and a power estimator worked out > nicely for the transmitter itself. However, I dont know what he means > by changing the bandwidth of the input data. Does it mean that I change > the pattern of 1s and 0s or just increase/decrease the number of bits > (resolution) of the PN sequence? Please help, I have come this far > working hard on my simulator and I dont want to stop short just on > something small I don't understand for the simulation itself. I don't understand what you need. some people seem to feel that my asking questions is an attack, but my only other course is ignoring you. 1) Is there a reason you can't ask your adviser? 2) A DAC operation is usually performed on several bits at a time. If you are sending ones and zeros, what does the DAC operation consist of? 3) How is the PN sequence production related to the LPF bandwidth? Jerry -- Engineering is the art of making what you want from things you can get.
From: billoo on 25 Jul 2006 12:06 Jerry Avins wrote: > billoo wrote: > > Hi > > > > I am currently working on a project which involves determining the > > relationship between the the "bandwidth"(as my advisor puts it) and > > power consumption of an I/Q transmitter. The I/Q transmitter works as > > follows: > > > > In-Phase: Even bits of PN sequence ---> DAC ---> LPF --> multiply by > > cosine --> transmit > > > > Quad-Phase: Odd bits of PN sequence --> DAC --> LPF --> mult. by sine > > --> transmit > > > > The problem is that my advisor wants me to see how the power > > consumption changes as you change the bandwidth of the input data (the > > PN sequence). I have a power model and a power estimator worked out > > nicely for the transmitter itself. However, I dont know what he means > > by changing the bandwidth of the input data. Does it mean that I change > > the pattern of 1s and 0s or just increase/decrease the number of bits > > (resolution) of the PN sequence? Please help, I have come this far > > working hard on my simulator and I dont want to stop short just on > > something small I don't understand for the simulation itself. > > I don't understand what you need. some people seem to feel that my > asking questions is an attack, but my only other course is ignoring you. > > 1) Is there a reason you can't ask your adviser? > > 2) A DAC operation is usually performed on several bits at a time. If > you are sending ones and zeros, what does the DAC operation consist of? > > 3) How is the PN sequence production related to the LPF bandwidth? > > Jerry > -- > Engineering is the art of making what you want from things you can get. > ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ 1) I have asked my pofessor and he is working on numerous projects and it takes him a while to reply to my emails and I saw that the groups generally respond quickly. 2) My project involves modelling the power consumption of the ZigBee CC2420 radio module. I modelled the DAC as an R-2R ladder which means that a 1 closes a circuit for a set of resistors to generate a particular output voltage and the 0 leaves the circuit open. 3) I am not concerned about the analag bandwidth but the digital bandwidth of the data stream going into the DAC. I want to graph the change in digital bandwidth from 0 to pi versus the power consumed by the analog component (since it is the most power hungry). So basically, I have the data stream of 1s and 0s coming out of the digital part of the circuit. I want to vary the bandwidth of the 1s and 0s and then see how the power consumed of the analog circuit changes. My question is what does the bandwidth of digital signal depend on (e.g. number of 1s and 0s, bit resolution)? Thank You Mohammed Billoo
From: Richard Owlett on 25 Jul 2006 13:40 Mohammed, Jerry's questions are often more instructive than some answers. Some pupils of DSP object to being required to think. Students do it and then realize why mentor asked the question. If you are not a native English speaker [ or even if you are ] a study of the fine distinctions between "pupil" and "student" would be instructive. Jerry, ask away. The ignorant will be made wise and foolish will be offended. Editorial comment. *TOO many* "student bodies" are just a conglomeration of pupils. PS. I think Mohammed can be used as an example of "How to Ask a Question". billoo wrote: > Jerry Avins wrote: > >>billoo wrote: >> >>>Hi >>> >>>I am currently working on a project which involves determining the >>>relationship between the the "bandwidth"(as my advisor puts it) and >>>power consumption of an I/Q transmitter. The I/Q transmitter works as >>>follows: >>> >>>In-Phase: Even bits of PN sequence ---> DAC ---> LPF --> multiply by >>>cosine --> transmit >>> >>>Quad-Phase: Odd bits of PN sequence --> DAC --> LPF --> mult. by sine >>>--> transmit >>> >>>The problem is that my advisor wants me to see how the power >>>consumption changes as you change the bandwidth of the input data (the >>>PN sequence). I have a power model and a power estimator worked out >>>nicely for the transmitter itself. However, I dont know what he means >>>by changing the bandwidth of the input data. Does it mean that I change >>>the pattern of 1s and 0s or just increase/decrease the number of bits >>>(resolution) of the PN sequence? Please help, I have come this far >>>working hard on my simulator and I dont want to stop short just on >>>something small I don't understand for the simulation itself. >> >>I don't understand what you need. some people seem to feel that my >>asking questions is an attack, but my only other course is ignoring you. >> >>1) Is there a reason you can't ask your adviser? >> >>2) A DAC operation is usually performed on several bits at a time. If >>you are sending ones and zeros, what does the DAC operation consist of? >> >>3) How is the PN sequence production related to the LPF bandwidth? >> >>Jerry >>-- >>Engineering is the art of making what you want from things you can get. >> > > > 1) I have asked my pofessor and he is working on numerous projects and > it takes him a while to reply to my emails and I saw that the groups > generally respond quickly. > > 2) My project involves modelling the power consumption of the ZigBee > CC2420 radio module. I modelled the DAC as an R-2R ladder which means > that a 1 closes a circuit for a set of resistors to generate a > particular output voltage and the 0 leaves the circuit open. > > 3) I am not concerned about the analag bandwidth but the digital > bandwidth of the data stream going into the DAC. I want to graph the > change in digital bandwidth from 0 to pi versus the power consumed by > the analog component (since it is the most power hungry). So basically, > I have the data stream of 1s and 0s coming out of the digital part of > the circuit. I want to vary the bandwidth of the 1s and 0s and then see > how the power consumed of the analog circuit changes. My question is > what does the bandwidth of digital signal depend on (e.g. number of 1s > and 0s, bit resolution)? > > Thank You > Mohammed Billoo >
From: Jerry Avins on 25 Jul 2006 15:03
billoo wrote: > Jerry Avins wrote: >> billoo wrote: >>> Hi >>> >>> I am currently working on a project which involves determining the >>> relationship between the the "bandwidth"(as my advisor puts it) and >>> power consumption of an I/Q transmitter. The I/Q transmitter works as >>> follows: >>> >>> In-Phase: Even bits of PN sequence ---> DAC ---> LPF --> multiply by >>> cosine --> transmit >>> >>> Quad-Phase: Odd bits of PN sequence --> DAC --> LPF --> mult. by sine >>> --> transmit >>> >>> The problem is that my advisor wants me to see how the power >>> consumption changes as you change the bandwidth of the input data (the >>> PN sequence). I have a power model and a power estimator worked out >>> nicely for the transmitter itself. However, I dont know what he means >>> by changing the bandwidth of the input data. Does it mean that I change >>> the pattern of 1s and 0s or just increase/decrease the number of bits >>> (resolution) of the PN sequence? Please help, I have come this far >>> working hard on my simulator and I dont want to stop short just on >>> something small I don't understand for the simulation itself. >> I don't understand what you need. some people seem to feel that my >> asking questions is an attack, but my only other course is ignoring you. >> >> 1) Is there a reason you can't ask your adviser? >> >> 2) A DAC operation is usually performed on several bits at a time. If >> you are sending ones and zeros, what does the DAC operation consist of? >> >> 3) How is the PN sequence production related to the LPF bandwidth? >> >> Jerry >> -- >> Engineering is the art of making what you want from things you can get. >> > > 1) I have asked my pofessor and he is working on numerous projects and > it takes him a while to reply to my emails and I saw that the groups > generally respond quickly. > > 2) My project involves modelling the power consumption of the ZigBee > CC2420 radio module. I modelled the DAC as an R-2R ladder which means > that a 1 closes a circuit for a set of resistors to generate a > particular output voltage and the 0 leaves the circuit open. Unless there is something decidedly peculiar about the transmitter module, it's power consumption is independent of the modulating waveform if it is FM or PM, and proportional to the duty cycle if it is AM. The duty cycle is not a function of bandwidth. PN sequences make good streams of random bits, but groups of N successive bits make poor random numbers, I suggest that you get your pseudo-random numbers some other way, say with a well designed linear congruential generator. > 3) I am not concerned about the analag bandwidth but the digital > bandwidth of the data stream going into the DAC. I want to graph the > change in digital bandwidth from 0 to pi versus the power consumed by > the analog component (since it is the most power hungry). So basically, > I have the data stream of 1s and 0s coming out of the digital part of > the circuit. I want to vary the bandwidth of the 1s and 0s and then see > how the power consumed of the analog circuit changes. My question is > what does the bandwidth of digital signal depend on (e.g. number of 1s > and 0s, bit resolution)? The bandwidth of a stream of random numbers is 1/2 the number-generation rate. Higher frequencies that you might imagine are present are aliased into that range or removed by the reconstruction filter that follows the DAC. (That's what the LPF is for. Properly designed, it passes no significant amount of any frequency higher than half the sample rate.) 4) Are you sure you understood what your professor asked you to do? Jerry -- Engineering is the art of making what you want from things you can get. |