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Crystal and frequency control glossary

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1996 Telecommunications Act

Legislation designed to spur competition among wireless and wireline carriers. Signed into law by President Clinton in February 1996.

2G

Abbreviation for second generation. An improvement over the original design.

3G

Abbreviation for third generation. The next generation of wireless technology beyond personal communications services. The new standard promises to offer increased capacity and high-speed data applications up to 2 megabits.

802.11

The Institute of Electrical and Electronics Engineers standard for wireless local area network interoperability.

A

A/D

Abbreviation for analog-to-digital.

Absolute maximum rating

Maximum rated voltage value assuring the normal operation of a crystal oscillator. Exceeding this value may result in a decrease in the reliability of a crystal oscillator.

AC

Abbreviation for alternating current. In electricity, alternating current (AC) occurs when charge carriers in a conductor or semiconductor periodically reverse their direction of movement. Household utility current in most countries is AC with a frequency of 60 hertz (60 complete cycles per second), although in some countries it is 50 Hz.

ACPR

Abbreviation for adjacent-channel power ratio.

Active satellite

A functioning satellite that receives and transmits or retransmits radio communication signals to or from a base station.

Activity

A term associated with the resistance of a crystal unit. A crystal unit with low resistance is said to have good activity while a crystal unit with high resistance is said to have bad activity.

Activity Dip

Used to describe an abrupt increase in the resistance and a perturbation in the frequency of a crystal unit, followed by an equally abrupt return to the prior values.

Activity Dip - illustration

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Adaptive array antennas

A type of advanced smart antenna technology that continually monitors a received signal and dynamically adapts signal patterns to optimize wireless system performance.

ADC

Abbreviation for analog-to-digital converter. A device that converts an analog signal to a digital signal that represents equivalent information.

AFC

Abbreviation for automatic frequency control.

AGC

Abbreviation for automatic gain control. A process or means by which gain is automatically adjusted in a specified manner as a function of a specified parameter, such as received signal level.

Aging

A systematic change in frequency and/or resistance with the passage of time due to internal changes in the crystal and/or oscillator. Aging is typically expressed as a maximum value in parts per million per year [ppm/year]. The rate of aging is typically greatest during the first 30 to 60 days after which time the aging rate decreases. Aging is affected by adsorption and desorption of contamination on the surfaces of the quartz, stress relief of the mounting and bonding structures, material outgassing, and seal integrity.

AGL

Measurement of tower height above the ground. Also referred to as tower height.

AM

Abbreviation for amplitude modulation. A type of transmission used in either the standard radio broadcast band at 535-1005 KHz, short-wave broadcasting and in some private radio services such as citizens band (CB) and aviation.

Amateur radio operator (HAM)

A noncommercial, private radio operator. There are six classes of amateur radio licenses that can be earned after passing FCC-administered examinations.

AMPS

Abbreviation for advanced mobile phone system. AMPS is a standard system for analog signal cellular telephone service in the United States and is also used in other countries. It is based on the initial electromagnetic radiation spectrum allocation for cellular service by the Federal Communications Commission (FCC) in 1970. Introduced by AT&T in 1983, AMPS became and currently still is the most widely deployed cellular system in the United States.

AMTA

Abbreviation for American Telecommunications Association. A Washington, DC based trade group representing specialized mobile radio operators.

Angle

The angle at which a resonator plate is cut from the quartz stone in relation to the original crystallographic axes. The angle of cut is critical to the performance of the crystal unit, particularly in the area of frequency deviation over a temperature range.

ANSI

Abbreviation for American National Standards Institute. The US standards-setting body. It is a non-governmental agency that develops and publishes standards for "voluntary" use.

Antenna

Any structure or device used to collect or radiate electromagnetic waves. A device that converts radio frequency electrical energy to radiated electromagnetic energy and vice versa; in a transmitting station, the device from which radio waves are emitted.

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APCO

Abbreviation for Association of Public-Safety Communications Officials-International. Trade group headquartered in South Daytona, Florida, representing law enforcement, fire, emergency services and other public-safety agency dispatchers and communications employees.

ASIC

Abbreviation for application-specific integrated circuit.

Assigned frequency

The center of the assigned frequency band assigned to a station. The frequency of the center of the radiated bandwidth.

ASK

Abbreviation for amplifier shift keying.

ASP

Abbreviation for application service provider. An ASP is a company that offers access over the Internet to applications and related services that would otherwise have to be located in their own personal or enterprise computers.

AT Strip

An AT-cut crystal in the shape of a rectangular strip. It has a higher ESR than a round AT-cut crystal but is smaller in size, thus allowing smaller crystal packages.

AT cut

The commercial designation for a specifically oriented resonator plate, having desirable and repeatable operating characteristics. A plate cut from a crystal of quartz such that the plate contains the X-axis and makes an angle of about 35 degrees with the optic or Z-axis. The AT-cut crystal is the most popular thickness-shear crystal unit manufactured today. It has excellent temperature and frequency characteristics. This design provides 70 to 80% of all crystal requirements. The frequency vs. temperature curve is a sine with the inflection temperature at ~ +25"C. Preferred for high frequency oscillator control over a wide temperature range for TCXO, VCXO, and Ovenized oscillators. Frequency range is from 500 KHz to 200MHz. Also used for filters. See BT cut.

AT-cut illustration

ATM

Abbreviation for asynchronous transfer mode. A high-speed multiplexing and switching method utilizing fixed-length cells of 53 octets to support multiple types of traffic. Note: ATM, specified in international standards, is asynchronous in the sense that cells carrying user data need not be periodic.

Attenuation values

A decrease in power of a received signal.

Attenuation

The maximum guaranteed reduction in power, ranging outside a specified frequency span. Spurious response attenuation is the minimum acceptable attenuation in the stopband, which allows for unwanted modes in the crystal.

Audio frequency (AF)

Generally in the range 20 Hz to 20 KHz.

AUTELSAF

European regional satellite facilities consortium owned by approximately 40 European countries

Automatic Frequency Control (AFC)

Similar to Automatic Fine Tune (AFT). A circuit that keeps a receiver in tune with the wanted transmission.

Authentication center

Abbreviation AuC. A functional piece of the HLR used to authenticate the user of mobile station equipment.

AVL

Abbreviation for Automatic Vehicle Location. Combining a locations-sensing device (such as a GPS receiver) with a wireless communications link to provide a home office or dispatcher with the location of a vehicle or mobile asset.

AWGN

Abbreviation for additive white gaussian noise. See white noise.

Axis

A direction in a quartz stone. The plural of "axis" is "axes."

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