Glossary of Terms



AESA: active electronically steered antenna

Amplitude Match: The absolute difference in the amplitude response between a reference filter and a filter under test.

Amplitude tracking: The relative difference in the amplitude response between a reference filter and a filter under test.

Analog Driver: An accessory circuit for an oscillator of filter which permits its frequency to be changed by a continuously varying signal.

Attenuation: Theloss of a signal in transmission through a filter, which is generally referring to signal power or signal amplitude.

Attenuator: A passive network or device that takes a part of the input signal and transmits the remainder with the least distortion. Attenuators broaden the dynamic range of devices such as amplifiers, reduce signal levels to detectors, match circuits and are used in other ways in product design.

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Ball Bond: The thermo-compressed bond between a metalized pad and a wire which has a ball-shaped end to it.

Band Reject Filter: Also called a notch filter,this is afilter that rejects a band of frequencies and passes both higher and lower frequencies. Sometimes called a notch filter.

Bandpass Filter: A filter that passes one band of frequencies and rejects both higher and lower frequencies.

Base Station: A fixed transmitter/receiver with which a mobile radio transceiver creates a connection link for access to the public-switched telephone network. The bond is also designated a nail head bond from the appearance of the flattened ball.

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Circulator: A three-port ferromagnetic passive device used to control the direction of signal flow in an RF circuit.

Coaxial: A transmission line in which one conductor completely surrounds the other, the two being coaxial and separated by a continuous dielectric such as air or PTFE.

Conversion Loss: The ratio in dB of the IF output of a mixer to the rf input power. All conversion loss measurements and specification are normally based on the mixer being terminated on all ports and a stated LO signal power level being applied.

Cutoff Frequency (Fco): The upper passband edge in lowpass filters or the lower passband edge in highpass filters. The passband edge closest to the stop band.

CW – (Continuous Wave): Signal of constant amplitude.  Used to differentiate between the performance of a microwave component for continuous power level vs. pulsed signals.

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dB – (Decibel): A unit of gain equal to ten times the common logarithm of the ratio of two power levels or 20 times the common logarithm of the ratio between two voltages.

dBc: Decibel related to the signal of a carrier.  Passive intermodulation distortion is typically stated in dBc which takes into consideration the 43 dBm carrier tones.

dBm: Decibels related to 1mW – the standard unit of power level used in the microwave industry. 

Directional Coupler: A passive device used for sampling incident and reflected microwave power conveniently and accurately with minimal disturbance to the transmission line. Some general applications for directional couplers include line monitoring, power measurements and load source isolators.

Downconverter: An assembly of components that converts microwave signals to an intermediate frequency range for. Generally consists of an input filter, local oscillator filter, IF filter, mixer and frequently an LO frequency multiplier and one or more stages of IF amplification.

Dynamic Range: The range in dB between the noise floor of a device and its defined maximum output level. The term applies to both audio devices and RF equipment, but the maximum output level is defined differently.

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ECO: Formal documentation required to make any change in specification, construction details or components used in products that have been released to production and are documented.

Electronic Tuning: The maximum output frequency deviation possible without significantly affecting oscillator performance characteristics. Done by calibrating the varactor diode coupled to the dielectric resonator.

EMI – (Electromagnetic Interference):  Unintentional interfering signals generated within or external to electronic equipment.  Typical sources could be power line transients and electromechanical switching equipment.

Envelope Delay: The propagation time delay undergone by the envelope of an amplitude modulated signal as it passes through a filter. Envelope delay is proportional to the slope of the curve of phase shift as a function of frequency.

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Feedback Amplifier: These are microwave amplifiers (GaAs FET or bipolar transistor) using negative feedback in the amplification stages. Used to control input and output impedances, increase operating bandwidth and minimize performance variations caused by inherent variations in transistor parameters.

Filter: A selective network comprised of capacitors, inductors and / or resistors which passes a specific band of frequencies and attenuates the out of band frequencies.

Fourier Analysis: The process of analyzing a complex wave by separating it into a plurality of component wave, each of a particular frequency, amplitude and phase displacement.

Frequency Accuracy: The maximum output frequency deviation from a specified tuning function under specified conditions. May be expressed in Mhz, ppm, or ppm/°C.

Frequency Range: The minimum and maximum frequencies between which the specified component will meet all guaranteed specification.

Frequency Sensitivity: The maximum peak-to-peak variation in coupling (in dB) of a directional or hybrid coupler over the specified frequency range.  Also referred to as “flatness”.

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Gain block: A single stage of gain or a cascaded series of gain stages.

Gain, maximum stable: The maximum stable gain (MSG) of a device is defined when maximum available gain is undefined (K<1). It is merely the ratio of mag(S21)/mag(S12).

Gaussian Filter: A filter network designed to pass a step function with zero overshoot and minimum rise time. This is similar to a Bessel Filter.

GHz - (Gigahertz): A unit of frequency measure equal to 1000 MHz (Megahertz) or a billion hertz.

Gmax: Maximum Available Gain, also referred to as MAG, or the gain that is possible when a transistor is unconditionally stable and input / output ports are simultaneously conjugately matched

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Harmonic Intermodulation Distortion: In dB, the ratio of distortion to the IF output waveform that is generated by mixer-generated harmonics of the RF and LO input signals.

Harmonic Signals: These are signals which are coherently related to the output frequency, and are usually integer multiples of the output frequency.

Highpass Filter: A filter that passes high frequencies and attenuates low frequencies.

Hybrid Coupler: This isa passive device with 4 ports deployed to equally split an input signal with a resultant 90° phase shift between output signals, or to combine two signals but still keeping high isolation.

Hybrid Integrated Circuits: The combination of thin-film or thick-film circuitry deposited on substrates with components such as chip transistors, capacitors and others. Thin-film construction is used for microwave integrated circuits (MICs).

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IF: Intermediate Frequency. In superheterodyne receiving systems, the frequency that all selected signals are converted for additional amplification, filtering and eventual direction.

Impedance: In relation to filters, this isthe resistive source and load terminations that are necessary to achieve proper filter performance.

Insertion Loss: The change in load power due to the insertion of a particular device into a transmission system.

Isolation:  A unit of measure (in dB) that states the separation of signal levels on adjacent ports of a device.  The greater the isolation value, less interference from a signal on one port is present at the other.

Isolator: A circulator becomes an isolator by terminating one port. An isolator has the property that energy flows in one direction only. This is used for isolating components in a chain so that bad VSWRs don't contribute to gain ripple, or instabilities like unwanted oscillations.

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Jamming (military): The deliberate radiation, re-radiation or reflation of electromagnetic energy with object of impairing the use of electronic devices, equipment or systems by the enemy. Equipment may consist of rudimentary CW or noise transmitters, broadband transmitters or complex systems that generate deceptive signals.

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Khz: Kilohertz, 1,000 Hertz, or one thousand cycles per second.

Knee Voltage: the voltage at which curves transition from linear to saturation. In the linear region, IDS depends on both VGS and VDS. In the saturation region, IDS depends mainly on VGS and not VDS.

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Limiting Amplifier: This relates to analog signals and their processing, and also refers to the operating range of an amplifier where little or no distortion occurs.

Limiting Level: The input power level at which the input/output characteristics exhibit compression (i.e., the transfer function becomes nonlinear in that the output increases less than 1 dB for a 1 dB increase in input).

Linear Phase Response: A filter that demonstrates a constant change in degrees per unit of frequency, and the resulting plot of phase versus frequency is a straight line.

Lowpass Filter: A filter that passes low frequencies and attenuates high frequencies. It is also called an anti-aliasing filter.

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MHz - (Megahertz): A unit of frequency measure equal to 1000 kHz (Kilohertz) or a million hertz.

Microstrip – (Microstripline): A transmission line which has a metalized strip and solid ground plane metallization separated by a thin, solid dielectric. 

Microwaves: High frequency radio waves lying roughly between infrared waves and radio waves. Microwaves are generated by electron tubes, such as the klystron and the magnetron, or solid state devices with built-in resonators to control the frequency or by oscillators. Microwaves have many applications for radio, television, radar, test and measurement communications, distance and location measuring, and more.

MMIC: Monolithic Microwave Integrated Circuit designed using either silicon or GaAs devices.

MTBF – (Mean Time Between Failure): The average time between failures of a component, sometimes attributed to the “useful life” of the materials used to assemble the device.  MTBF assumes that the component can be “renewed” or fixed after each failure and returned to service immediately after failure.

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Network Analyzer: A microwave test system that characterizes devices by their small-signal scattering parameters (S-parameters). The measurements include the ratio of magnitude and phase of input and output signals at the various ports of a network with the other ports terminated in the specified characteristic impedance.

NF: Noise Figure. In dB, the ratio between the signal-to-noise ratio applied to the input of the microwave component and the signal-to-noise ratio measured at its output. It is one indication of the amount of added noise to a signal by the component during operation.

Nf50: Optimum Noise Figure. A measure of the noise generated by a transistor when tuned for minimum noise figure at a given frequency.

Non-Coherent Signals: The limiting factor for most Wilkinson power dividers used as combiners is power dissipation. When input signals are out of phase, non-coherent or have amplitude unbalance this causes a cancellation across the isolation resistors resulting in power dissipation. 

Non-Linear Transmission Line: A nonlinear transmission line is a form of artificial transmission line created by a periodic structure of series inductors and shunt capacitors.

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Oscillator: Oscillators provide the signal source for all microwave systems, including both transmitters and receivers.

Oscillator Load: The maximum VSWR seen by the oscillator at the output port, referenced to 50°.

Output Frequency: The frequency of the desired output of a component. Undesired frequency components may include harmonics, subharmonics, 3/2 harmonics or nonharmonic spurious signals.

Output VSWR: Minimum voltage standing wave ratio of a power divider at any output port over the specified frequency range with all other ports terminated in 50 ohm loads.

Overshoot: In percent terms, the amount that a signal exceeds its steady state output on its initial rise.

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Passband: The band of frequencies that passes through a filter with essentially no attenuation.

Passivation: The formation of an insulated layer directly over a metal to protect the surface from contaminants, moisture or particles.

Phase Balance: The maximum peak-to-peak phase difference (in degrees) between the output ports of a power divider over the specified frequency range.

Phase Shift: A signal changing as it passes through a filter. A delay in time of the signal referredto as phase lag, and in normal network phase lag increases withfrequency, producing a positive envelope delay.

Power Divider: A passive resistive network that divides equally the power applied to the input port between any number of output ports without affecting significantly the phase relationship or causing distortion.

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Q: The Q or figure merit of a filter is a measure of the sharpness of response or its frequency selectivity.

QPR: Quadrature Partial Response. A method of modulating a microwave carrier with two parallel streams of filtered digital bit streams carried in phase quadrature relationship. QPR normally uses 3-level partial response and occupies one-half the bandwidth of QPSK.

QPSK: Quadrature Phase Shift Keying (quadriphase). A method of modulating a microwave carrier with two parallel streams of NRZ digital bit streams so that data is translated into 90° phase shifts of the carrier.

Quadrature: Having a characteristic 90° phase shift. Term describes a coupler in which the two output signals are 90° out of phase. In telecommunications, it is used for modulation techniques such as QPR and QPSK.

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Relative Attenuation: This is attenuation measured with the point of minimum attenuation taken at 0dB. Relative attenuation = attenuation minus insertion loss.

Return Loss: When expressed in dB is the ratio of reflected power to incident power. It is a measure of the amount of reflected power on a transmission line when it is terminated or connected to any passive or active device. Once measured, it can be converted by equation to reflection coefficient which can be converted to VSWR.

RF: Radio Frequency.Generally referring to any frequency at which the radiation of electromagnetic energy is possible typically above 50 MHz.  Over 1000 MHz and up is considered microwave.

RF Leakage: The amount of energy which radiates (leaks) from a connector or a device.  This is usually tested at one frequency and expressed in dB. 

Ripple: The wavelike variations in the amplitude response of a filter. Chebyshev and Elliptic function filters have characteristics such that the differences in peaks and valleys of the amplitude response in the passband are always the same. Butterworth, Bessel and Gaussian filters do not have ripple. Ripple is usually measured in dB.

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Shape Factor (Bandwidth Ratio): In a filter, the ratio comparing the high-attenuation level bandwidth and low attenuation level bandwidth. Or the ratio of the 3dB bandwidth to the stopband bandwidth.

SMR: Specialized Mobile Radio. A private business service using mobile radiotelephones and base stations communicating via the public phone network.

Spectrum: The complete range of electromagnetic waves which can be transmitted by natural sources such as the sun, and man-made devices such as cellular phones. Electromagnetic waves vary in length and therefore have different characteristics. Longer waves in the low-frequency range can be used for communications, while shorter waves of high frequency show up as light. Spectrum with even shorter wavelengths and higher frequencies are used in X rays.

Step Function: A signal characterized by instantaneous changes between amplitude levels. The term usually refers to a rectangular front wave-form used for making tests of transient responses.

Stopband: That part of the frequency spectrum that is subjected to a specified amount of attenuation by a filter.

Stripline: A transmission line consisting of a conductor above or between extended conducting surfaces.  Higher frequencies or broadband devices tend to favor stripline technology.

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Temperature: The minimum and maximum ambient temperatures a given component can operate at and still meet all guaranteed specifications unless otherwise noted.

Termination (RF Loads): Used at the end of a transmission line designed to absorb RF power with very little reflection, effectively terminating the line or port in its characteristic impedance.

Thin Film: A thin-film (usually less than 10,000 Angstroms thickness) deposited onto substrate by an accretion process such as vacuum evaporation, sputtering or pyrolytic decomposition.

Time Delay: The slope of the phase versus the frequency curve. In a loose sense, this is the time it takes a designated point in a wave to pass through a filter. It is also called envelope delay.

Transition Band: The range of frequencies that bounda passband / stopband interface.

Transmission Line: The conductive connections between circuit elements which carry signal power.  Wire, coaxial cable, microstrip and stripline traces and waveguide are common examples.

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Ultrasonic Bonding: A process involving the use of ultrasonic energy and pressure to join two materials.

Uplink: The earth-to-satellite microwave link and related components such as earth station transmitting equipment. The satellite contains an uplink receiver; uplink components in the earth station are involved with the processing and transmission of signal to satellite.

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Varactor: A diode which, when operated in a reversed-biased condition, provides a junction capacitance that varies with applied voltage. Used as an "electrically variable" capacitor in tuned circuits (such as those in varactor-tuned oscillators) or as frequency multiplier.

Voltage Standing Wave Ratio ( VSWR): In a stationary wave system, the ratio of the amplitude of the electric field or voltage at a voltage maximum to that at the adjacent voltage minimum.

Vapor Phase Epitaxy (epitaxial): An epitaxial layer on a transmitter wafer or chip formed by condensing a single-crystal layer of semiconductor material on the surface of the wafer.

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Wafer: A single slice of substrate material (silicon or gallium arsenide) upon which many transistors are fabricated. The wafer is then tested, scribed and broken apart to produce transistor chips.

Wilkinson Power Divider: A passive device that equally splits an input signal to each output or combines signals to a common port.  Wilkinson power divider differ from reactive splitters as the output ports are isolated, so signals entering one of the output ports will not interfere with signals on the adjacent port.  The limiting factor for Wilkinson power dividers used as combiners is power dissipation. When input signals are out of phase, non-coherent or have amplitude unbalance this causes a cancellation across the isolation resistors resulting in power dissipation.

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YIG: Yttrium-iron garnet is a synthetic crystalline ferrite containing yttrium and iron (Y3Fe6O16). If a single crystal sphere of YIG is immersed in a magnetic field, and RF energy is coupled into it via a magnetic loop, the crystal will resonate at a frequency linearly proportional to the magnetic field strength. In practical YIG-tuned oscillators and filters, the magnetic field is derived from an electromagnet and the resonant frequency of the YIG sphere is proportional to the current flowing through the magnetic coil.

YIG-tuned Filter: A microwave filter using YIG sphere as the resonant element.

YIG-tuned Oscillator: A microwave tunable oscillator using the YIG sphere as the frequency determining element. YIG-tuned oscillators can be made with Gunn-diode technology or, add an internal buffer amplifier to minimize frequency pulling, and produce additional output power capability. YIG-tuned oscillators are fundamental oscillators; they do not contain frequency multiplication circuitry.

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