Final week before presentation

Now that we have about five and a half days to complete the project, with a course test in between, we're approaching the final stretch and finish line. The past few weeks have been quite productive, with respect to design and fabrication, mostly due to the hard work of Maxwell and David in design, and Richard in fabrication of the Butler matrix. About two weeks ago, we received the masks that were used for etching or printing on the circuit board.

Initially, when we went to print the boards, there was a problem with the plastic protection machine, whose function is was to place a layer of plastic over the board so as to protect it, so we left the remainder of printing for Meng-Hung under the command of Grbic, who told us that we shouldn't have been in the 411 lab since we were not OSH), so last Friday, we were able to assemble the parts of the project while testing individual components in between.

I can't say if Maxwell or David have put more time in the lab, but the two of them have carried out the majority of design and lab time. Under the advise of Maxwell, I have taken responsibility for the written report as well as the presentation slides and the link budget and signal characteristics. I'm not writing the entire report, only formatting, organizing, compiling, and making sure all the parts are included.

We didn't meet today, but ideally I will have all member contributions of the report by Saturday afternoon/evening so that I can complete a rough draft of the report for Sunday, so that it can be revised by the group. It would be best to have slides ready that day so that we can begin to practice or presentation which will be held on Tuesday afternoon after 3pm. We must remember to provide Grbic with a compact disc of our our files by 2pm on Tuesday, including our presentation, since we'll be running the presentation from his personal computer.

Signal Generator

I met with Meng-Hung this morning, and we spoke about the equipment and how we might construct a signal similar to the HDTV signal. He mentioned that it's not essential to deliver HDTV data modulated signal through our system, that we could simply use a 2.4GHz signal without the modulated data.

He emphasized that we concentrate on our Bulter matrix design, so that we can begin to fabricate soon. Grbic also stressed this point, so I've sent an email message to the team saying that I'm willing to help with that aspect of our project for the next week, in preparation for our review this coming Thursday.

Manuals for Equiptment in Lab

This entry will mainly deal with how to construct a modulated signal in the lab, so that we can test the quality of our realized design. Although we have not completed our design, let alone the fabrication, we need to know if it is possible to modulate a signal in the lab. The team also scheduled a project review with professor next Thursday from 6:30-7pm (subject to change). In the review, Grbic will tell us if we are making progress to complete the project adequately, or if we need to pick up the pace.

Meng Hung sent an email with the signal generating equipment available to us in the lab. He mentioned three pieces, namely HP E4433B ESG-D Series Signal Generator, HP 8350A Sweep Oscillator, and HP D4000A Digital Signal Generator. I promptly located the manuals found on the Agilent website, which I can provide to you if you request a specific manual. On each of the three manuals, I searched for the pertinent information to phase modulation, and suggest reading a few times to familiarize with the modulation controls before actually testing our antenna array. The following page numbers correspond to the pages on the pdf files I have.

8350A p.72-3
E4433B p.124-136
D4000A p.55-7, 532-551 (similar to E4433B phase modulation)

I would like to schedule an appointment with Meng Hung, to actually attempt to construct a phase modulated signal at our frequency of operation. If the equipment does not support the frequency we're interested in transmitting, we may need to change the signal characteristics.

My Research Continued

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).

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.

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.

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.