After presenting my research to the team last week, Max suggested I find more about the HDTV signal we'll be transmitting, such as its modulation type, bandwidth, and frequency. In addition, Professor Grbic suggested a reading in the coursepack for lecture today, and the topic of discussion is link design and link budget. The readings of pertinence to our design are p.125-134 and p.149-159 of the coursepack. These sections will be valuable in our understanding of requirements for design. Note that spring break is next week, so there will not be a group meeting during the week. Our project review comes the second week after we return to class, namely on March 12/13.
In response to Max's request, I have found the following information that should useful in our design:
Quadrature phase shift modulation, eight phase shift modulation, and sixteen quadrature amplitude modulation are specified, where the bandwidth efficiency improves respectively for the schemes listed, and in order to send a signal with the same quality, the power delivered must increase.
There is also mention of forward error coding (FEC), which adds inormation to the signal to improve the reconstruction at the demodulator on the recevier, and it descreases power consumtion for transmission, but it takes more bandwidth.
Refer to source for system interface of transmission (p.10), error performance requirements, including bit error rate (p.14-15),
(Source: www.atsc.org/standards/a_80.pdf)
On the next resource, there is another system definition, which defined an alternate transmitter and modulation station that offers two modes, terrestrial broadcast mode (8-VSB), and a high data rate mode(16-VSB).
(Source: http://www.atsc.org/standards/a_53-Part-1-6-2007.pdf)
The bandwidth of the video signal is approximately 6.0MHz, and the frequency of transmitted signal is deendant of the modulation scheme.
These topics must be explored in further depth in order for a successful chance for design. I will be working closely with Max to work out the specifications on the signal type, and we must wok closely with Richie and Dave to make sure our Butler matrix can interface with properly. I plan to study these standards established by the Advanced Television Systems Committee Inc. (ATSC).
Tuesday, February 19, 2008
Grbic's Comments (to the team) on our Project Proposal
1) For switching, you probably need buy or design some sort of RF SP4T
switch.
2) Just a thought....you may want to purchase 4 cheap monopoles (for the
frequency of interest) with SMA connectors on them for testing purposes, in
addition to designing your own antennas (patches for example). This way you
can compare the performance of both sets of antennas. Also, you will not
have to wait on the patch antenna design to test your Butler matrix.
3) You will need to purchase 50 ohm SMA terminations. I don't think we have
enough to terminate the other ports of your Butler matrix while testing 2
ports at a time.
switch.
2) Just a thought....you may want to purchase 4 cheap monopoles (for the
frequency of interest) with SMA connectors on them for testing purposes, in
addition to designing your own antennas (patches for example). This way you
can compare the performance of both sets of antennas. Also, you will not
have to wait on the patch antenna design to test your Butler matrix.
3) You will need to purchase 50 ohm SMA terminations. I don't think we have
enough to terminate the other ports of your Butler matrix while testing 2
ports at a time.
Wednesday, February 13, 2008
Link Design and HD Signal Research
Each member of the team was designated an aspect of the project to further research. It is important that each individual understand each component thoroughly, but in the interest of detailed research, we have concentrated on specific areas. David and Richie were asked to research the Bulter matrix concept. Chris and Max were asked to research the link budget and the HD signal, and in addition, Max will study antenna design.
The majority of my research on link design is sourced from Professor Grbic's lecture 11 & 12 notes. The following summary contains the points that I felt are necessary to understanding before we start design.
Noise depends on the noise temperature of the receiver system and the receiver noise bandwidth, where the bandwidth is determined by the data rate of transfer (or channel capacity) and the type of modulation coding. Modulation is a technique used to manipulate a message signal by using the message to vary the amplitude, phase frequency, or polarization of a certain carrier wave. Demodulation is the procedure of extracting the message signal by a receiver system from the received modulated carrier wave.
Due to environmental factors and noise from channel or circuit, we will notice a certain amount of error in the received signal. Error coding is the attempt to undo the error between the intended transmit message and the error filled message seen by the receiver. The process of error coding is achieved by using mathematics to formulate the message into an encoded set of bits, allowing the receiver to identify error, or undesired contamination, and in the best case, the receiver system can strip the signal of error. There is a tradeoff between decreasing the bit error rate and increasing the bandwidth of reception or similarly decrease the channel capacity. Examples of encoding methods are binary phase shift keying, quadriphased phase shift keying, binary frequency shift keying, multiple frequency shift keying, and binary amplitude shift keying.
We can measure the signal to noise ratio for a digital communication system by taking the ratio of the amount of energy received for a bit to the noise spectral density, and this ratio must pass a certain threshold to ensure the signal can be demodulated correctly. We can plot the bit error rate to the signal to noise ratio described above to give the designer the ability to choose the best performance for the digital link for a given amount of radio frequency power. We can use a certain strategy to find the amount of transmit power required to demonstrate an effective and error minimized link. The strategy is to first determine the maximum bit error rate that is allowed, then to find the signal to noise ratio for the digital link based on the type of modulation, and finally to factor in path loss to determine the minimum amount of transmit power required.
The majority of my research on link design is sourced from Professor Grbic's lecture 11 & 12 notes. The following summary contains the points that I felt are necessary to understanding before we start design.
Noise depends on the noise temperature of the receiver system and the receiver noise bandwidth, where the bandwidth is determined by the data rate of transfer (or channel capacity) and the type of modulation coding. Modulation is a technique used to manipulate a message signal by using the message to vary the amplitude, phase frequency, or polarization of a certain carrier wave. Demodulation is the procedure of extracting the message signal by a receiver system from the received modulated carrier wave.
Due to environmental factors and noise from channel or circuit, we will notice a certain amount of error in the received signal. Error coding is the attempt to undo the error between the intended transmit message and the error filled message seen by the receiver. The process of error coding is achieved by using mathematics to formulate the message into an encoded set of bits, allowing the receiver to identify error, or undesired contamination, and in the best case, the receiver system can strip the signal of error. There is a tradeoff between decreasing the bit error rate and increasing the bandwidth of reception or similarly decrease the channel capacity. Examples of encoding methods are binary phase shift keying, quadriphased phase shift keying, binary frequency shift keying, multiple frequency shift keying, and binary amplitude shift keying.
We can measure the signal to noise ratio for a digital communication system by taking the ratio of the amount of energy received for a bit to the noise spectral density, and this ratio must pass a certain threshold to ensure the signal can be demodulated correctly. We can plot the bit error rate to the signal to noise ratio described above to give the designer the ability to choose the best performance for the digital link for a given amount of radio frequency power. We can use a certain strategy to find the amount of transmit power required to demonstrate an effective and error minimized link. The strategy is to first determine the maximum bit error rate that is allowed, then to find the signal to noise ratio for the digital link based on the type of modulation, and finally to factor in path loss to determine the minimum amount of transmit power required.
Wednesday, February 6, 2008
First group meeting after proposal deadline
After meeting to discuss the next phase of our project, we quickly scanned our schdule of work, and David noticed that our chart does not include the one week vacation at the end of February. Max will adjust accordingly, since during this one week period, the team will probably not be able to progress with fabrication of the final design, which would be complete in the ideal situation. At the moment, we're deciding which area's of the project we would like to research, and will inform the team of our preference by Friday, so that we can start collecting nessesary resources. We need to decide if a team member should write minutes at our weekly meeting, and also if leader and minute taker roles should rotate or stay constant.
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