RF and Microwave Lab Rules

RF and Microwave Laboratory (ECEE 254)

Rules of Use

Department of Electrical and Computer Engineering

425 UCB

University of Colorado

Boulder, CO 80309

The latest version of these rules can be found at http://ece-www.colorado.edu/~kuester/labrules.htm .

Responsible Faculty Members:

Prof. E. F. Kuester ECOT 248 (303) 492-5173 kuester@schof.colorado.edu

Prof. Z. Popović ECOT 252 (303) 492-0374 zoya@schof.colorado.edu

(Revised 19 December 2007)

The RF/Microwave Laboratory in Room ECEE 254 of the Engineering Center is intended for the use of students, faculty and staff of the ECE Department of UCB who are taking a course which requires use of the lab facilities, or who are working on projects involving antenna design or circuits operating at RF or higher frequencies. Unlike some other labs in the department, this room is not operated as an open lab. All users must have prior permission to use the lab (enrolment in a class which uses the lab constitutes such permission for the duration of the course). Users wishing to use the lab without the supervision of a responsible faculty member or of a qualified TA must undergo certification in the proper use of the lab facilities.

There are two paramount concerns that underlie the rules that have been put in place for this lab. The first is your personal safety and that of the other users of the lab. A scientific lab is not an ordinary environment, and contains many possible hazards to your health and well being. Exercise discretion when you are in the lab, and avoid actions that pose a danger to people or property.

The second concern is the condition of the equipment in the lab. The total value of this equipment easily exceeds $1,000,000. Not only are many instruments very expensive to replace, they are likewise quite costly even to repair. Since the budget for maintenance of this lab is modest at best, negligent or abusive treatment of lab facilities will not be tolerated, and may constitute grounds for termination of your privilege to use the lab.

Indeed, violations of any lab rule might result in the removal of your privilege to use the lab. This might be a real hardship to you, particularly if you are enrolled in a class that uses the lab, or if your thesis research depends on the use of lab facilities. Such circumstances will not affect the decision to revoke your lab privileges, so think when you’re using the lab.

General

All laws and rules of the University of Colorado apply to the use of this lab. In particular, smoking is not permitted in the lab (as indeed is the case in the entire Engineering building), and the presence of firearms is prohibited. It is the responsibility of any user of University facilities to know and abide by all University regulations.

Permission to Use the Lab

Permission can be obtained only from one of the responsible faculty members listed above. They will arrange for a certification test for you to ensure that you are qualified to use the relevant equipment.

Responsible Use

It will be your and your advisor’s/instructor’s responsibility to ensure that you are familiar with the responsible and proper use of all instruments that you will make use of and that you have been appropriately trained in their use. Graduate student users, technicians and staff are asked to use the laboratory responsibly and to set a good example for undergraduate students. All users are expected to familiarize themselves with the laboratory rules and abide by them.

Available Equipment

A summary of the major equipment in the laboratory is available. In addition, an assortment of multimeters, DC power supplies, function generators, antennas, waveguide and coaxial hardware is also available. Disposable supplies such as solderable connectors, substrates, etc., are generally expected to be provided by the users of the lab.

Damage and Accident

Damage to any instrument is very expensive and accompanied by long repair periods. Students, faculty and staff depend on the instruments' availability and reliable performance for research and teaching alike. Damage to the instruments will have serious consequences for both students and instructors.

It is very important that any damage or accident (injurious or otherwise) in the laboratory be reported immediately. If problems can be addressed at an early stage, it will be easier to keep the laboratory in good and safe working condition. Naturally, anybody can have an accident. Fairness, circumstances and a rather generous willingness to forgive are negotiable. However, malicious damage or failure to report an incident will reduce or eliminate any flexibility we might choose to use in dealing with you. Permanent exclusion from the lab could result from such behavior.

Reserving Equipment

Equipment can sometimes be reserved provided you have permission and are certified to use it. Requests to reserve the RF/Microwave laboratory or any of its specific instrumentation can be made to any of the responsible faculty listed above. People who have reserved the lab or its equipment in advance have priority and are entitled to ask anybody who is currently occupying the reserved equipment to make it available immediately. Instructional use of the lab and its equipment always takes precedence over other uses. We will try to make every effort to accommodate any reasonable request for use of the lab within these guidelines.

Please cancel your reservation if you do not intend to make use of it after all, so that other users may have the opportunity to use the equipment.

All users of certain equipment, whether by reservation or not, are required to enter their name(s) into the appropriate equipment user registers available in the laboratory. Failure to log your usage will result in revocation of your lab privileges.

Removal and Return of Equipment

Removal of any equipment from the lab is possible, but absolutely requires the prior written consent of one of the responsible faculty. To request such usage, write down what you wish to borrow, sign and date your request, and get it signed by a responsible faculty member. Upon obtaining the written approval, the faculty member will make a record indicating who has borrowed it, where it is located, the date it was borrowed and the date it is to be returned. There will be no borrowing of equipment for indefinite periods: the normal borrowing period will not exceed 1 day. In no case will the loan period exceed 3 months, but renewals will be permitted under extraordinary circumstances. Special authorization by all responsible faculty is required for any loan period longer than one day. Remember: such authorized removal of equipment still requires you to sign for the instrument and assume responsibility for its care and proper return to the lab. Equipment in current use can not be signed out. When the equipment is returned, the faculty member who authorized its loan will note the date of its return and who returned it.

Visitors

Visitors are welcome in the laboratory provided they abide by the laboratory’s rules. They must be accompanied by at least one authorized person (a faculty, TA or a grad student specifically authorized to accompany visitors). This authorized person takes full responsibility for the visitors and may not leave the visitors unattended.

No external persons (including visitors) are allowed to make use of the laboratory unless by prior written arrangement with a responsible faculty member. Usage charges for this or any other Electromagnetics Group lab by parties outside of the department will be assessed according to affiliation, level of support required and instruments used.

Computer Use

The computers in this lab are primarily for use with the measurement equipment in the lab. These uses have priority over any other use (such as email, web surfing, etc.). A number of useful programs have been installed on these computers to facilitate microwave and RF design and measurement tasks. Please do not alter the installations in any way. Do not add, remove or change data or programs from these computers without permission from a responsible faculty member. Please save your own data to some form of removable media or email it to yourself, since preservation of data saved to the hard disks cannot be guaranteed.

Connectors: Use and Care

A variety of connectors are used in the lab with different instruments. An overview of RF and microwave connectors can be found at

http://ece-www.colorado.edu/~kuester/Coax/connchart.htm

and should be carefully studied. Note especially the following points.

BNC connectors are well known and are cheap, but inefficient at microwave frequencies. 3.5 mm SMA connectors cost about $50 each and are used with the network analyzers. Note the difference between 3.5 mm SMA connectors and 3.5 mm precision connectors even though they are designed to interface with each other. The 3.5 mm precision connectors have only air dielectric. Always check visually that you are not accidentally using one. Precision connectors are much more expensive than SMA connectors and can be easily destroyed if care is not taken. N-type connectors are a little more robust, but should still be treated with respect. Spectrum analyzers, microwave oscillators and power meters, to name only a few, utilize these connectors. The other major type of connector of importance in the microwave lab is the 7mm APC-7 connector. These connectors cost close to $500 each and should be treated very carefully. The APC-7 connector is a sexless connector and the faces (but not the outer sleeves) of two connectors connect flush against each other. The smoothness and cleanness of these faces is what makes the APC-7 such a high quality connector, and these faces should be protected at all times. These connectors should always be stored with the threaded sides of the connector extending as far as possible past the flat surface, and covered with a plastic protector. Every student using the lab should have had a detailed education in the proper care and use of connectors. If you have not had a connector training session, ask someone to help you or tell your advisor or instructor so that he/she can either show you or get someone who can help you. No excuses will be accepted for the mistreatment of connectors.

Connectors should be cleaned regularly. As a general rule of thumb: clean before and after each use! Only the approved cleaning solutions provided in the lab should be used to clean connectors. Isopropanol (NOT rubbing alcohol) is recommended. Under no circumstances should methylated spirits or benzene or any other similar solution be used to clean connectors. There should be clean Q-tips or similar applicators available in the lab to clean connectors with; if not, bring your own supply. Apply the cleaning solution to a Q-tip (not directly to the connector) and gently clean the connector. Never spray the cleaning solution directly into a connector. Do not use cleaning solution on a resistive material, as it can degrade the performance of loads. Cleaning connectors regularly will not only make them last longer, but will also provide better results for your measurements.

Before Leaving the Lab

Make sure that all equipment you used has been turned off and returned to the place from which you obtained it. All cables and probes must be returned to their appropriate place on the cable racks or in the storage cabinets. Please remove all temporary markings and/or tape you from all items before returning them, and replace them in an orderly manner in the place they belong.

NOTE: Certain instruments (such as the network analyzers) may be left running, but their display intensity should be turned down to protect the screen from burn-in. Similarly, the microwave oscillators may be placed into "stand-by" mode or left on if they will be used again by you within 24 hours. These instruments have long (several hours) warm-up periods. If in doubt, please switch off.

General Conduct

People from different walks of life have to work together in this laboratory. To ensure that everybody can use the laboratory to the fullest extent, the following general rules should be followed:

Cables and other equipment not currently in use must be returned to their proper places and not thrown or placed aside "somewhere".
Broken cables should be reported to the appropriate responsible person (instructor or TA).
Do not leave the door open outside of class times or TA office hours.
Do not admit anyone by opening the door for them; all persons authorized to get into the lab will have their own key or card access.
No unauthorized experiments or other activities are to be conducted in the lab

Food in the Laboratory—NONE!

Various substances are used in the laboratory. Some of them are highly toxic (acids, compounds containing cyanides and barium, etc.). Contamination of food or drink with such substances is very hazardous for obvious reasons. Direct interaction of food or drink with precision measuring instruments can at best compromise their calibration and at worst damage their basic operation. Food also attracts rodents that may eventually cause damage to equipment. Therefore:

No eating, drinking, smoking, chewing gum, use of inhalators, or other consumption is allowed in the laboratory. Food for consumption must not be kept in the laboratory. No food or beverages may be prepared inside or brought into the laboratory. Equipment Safety and Care

Appropriate precautions can secure the safety of instruments and ensure worry-free measurements for all parties concerned. The department has only limited money available for the upkeep of this lab, and would prefer to spend it on upgrading of laboratory facilities rather than repair or replacement of equipment. Therefore, please follow these guidelines:

Damaged or broken equipment is to be reported immediately to the TA or instructor.
You are not allowed to repair any equipment. Our staff is trained to take appropriate action for improperly functioning instruments.
You are not allowed to open any equipment.
Do not try to operate equipment you think you know how to use but don’t! Ask someone who is knowlegeable to show you how to use it correctly.
Equipment must be set up, operated and maintained according to the manufacturer’s instructions.
Do not obstruct the ventilation of any equipment.
Make absolutely sure of the maximum power levels for each specific instrument and take precautions that this level is never exceeded. Take special care when active circuits are connected to the network analyzers and spectrum analyzers and be very certain that measures are taken to protect the instrument against unwanted power.
Always make sure that a DC block is present when measuring with the spectrum analyzer and do not remove it unless you are very sure of what you are doing. Let your TA or instructor check your measurement set-up before it is powered up.
Electrically ground yourself before touching the ports of the network analyzer and make sure that all cables are statically discharged before they are connected to the network analyzer. This means use a wrist strap at all times when working with the network analyzer!
Special care should be exercised when using calibration standards. Relace them in their storage box immediately after use. Do not borrow standards from one set to use with another. Do not use calibration standards for any other purpose than calibration; for example, they should not be used to terminate ports during a measurement!

To ensure accurate measurements as well as to protect the sensitive input circuitry of some of the equipment from damage: All cellular phones, pagers and other pieces of personal communication equipment are to be turned off BEFORE entering the laboratory. This means TURNED OFF, not merely put in standby mode! Common causes of damage

Power cables that are not grounded – MAKE SURE ALWAYS TO USE CORRECTLY GROUNDED POWER CORDS; DO NOT USE "HANDMADE" SUBSTITUTES.
DC voltages and currents on active circuits – Use capacitive decoupling and make sure that coupling capacitors are discharged and power supplies switched off before the circuit is connected.
Static charges on long cables – ALWAYS discharge cables before they are connected.
High power levels – Be very careful with amplifiers and oscillators. Use attenuators.
Mechanical damage to connectors – Connectors and cables are VERY expensive and sensitive. Handle them with great care and they will last a long time and can be used by everyone. Read the paragraph about connectors very carefully and FOLLOW ITS INSTRUCTIONS !!!

Anechoic Chamber

The anechoic chamber is very prone to electrostatic charging. This can be fatal for the network analyzer. The cables, antennas and portions of human anatomy inside the chamber get charged very easily. When entering the chamber therefore, all cables must be disconnected form the network analyzer. When you emerge from the chamber you should first discharge yourself, and then discharge the cables that are to be connected to the network analyzer. The anti-static grounding strap should be worn at all times, while a cable can be discharged by connecting a load or a short circuit to it.

The absorbers inside the chamber are expensive and it is critically important that their tips remain sharp. The absorbing cones should therefore never be stacked on top of each other or anything else put on the tips of the cones. Two absorbing blocks should not even be stacked with the top one upside down on each other, since that will also damage the tips. If any of the blocks are removed form the chamber, they should be packed neatly outside the chamber in the lab and returned when the measurement is finished.

Personal Safety

Apart from keeping the equipment running, we would also like to see our users stay alive and healthy. You are therefore asked:

Not to test any wires with your tongue or touch any live-wires
To regard all wires as live-wires
Not to operate faulty equipment, as it may endanger life. Please report faulty equipment.

The use of radiation hazard meters is recommended if you are using power levels in excess of 30 dBm, in order to limit radiation exposure to personnel and keep them within safe limits.

The probability of the presence of EM fields at significant levels is rather higher in this lab than in most others. Persons with pacemakers or similar devices should not enter the lab.

Capacitors are to be safely discharged before their return and a short should be placed across their terminals to prevent electrostriction from occurring.

Ground wires may not be removed from any cables or sockets. Although their removal might prevent ground-loops (which are undesirable in some cases), they also float the respective instrument at an unspecified (possibly high) voltage. If ground loops are a concern, obtain suitable isolation transformers as necessary.

General Safety

For general safety the following also have to be adhered to:

No chemicals, biological materials and cultures, radioactive materials, isotopes, explosives, flammables, or guns may be brought into the laboratory. If such is required for official experiments, written permission, approved by the responsible faculty and by the chair of the department is required. Training in the handling of such materials, the safety of others, and provision for proper storage and disposal must be ensured beforehand. This will have to be adequately demonstrated to the satisfaction of the responsible faculty beforehand as well.
Cryogenic liquids have to be in proper containers for transport and storage, and must not be left unattended. People wishing to use such materials must be trained in their handling ahead of time. Prior written authorization by the responsible faculty is required for their use in the lab. Appropriate warning signs as well as labels describing their contents are required.
No open flames are allowed in the laboratory.
Approved warning signs should be displayed in areas of danger.
You should adhere to all warning signs and signals.
You must know where fire extinguishers are and be familiar with their proper use.
In the event of a fire, follow fire regulations.
Safety measures are not allowed to be removed, impaired, tampered with and/or rendered ineffective.
No unauthorised private experiments are allowed.
Apply good, sound reasoning in the laboratory ... and if possible when you leave the lab, too.

All members of the faculty and staff of the ECE department are charged with ensuring the safety of this laboratory. They are empowered to enforce all rules governing its use and to stop any unsafe practice or conduct in the laboratory.