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|
| ALC |
automatic level control |
| analog |
A signal with an amplitude that can have a continuous range of values. |
| AWG |
arbitrary waveform generator—A waveform generator capable of generating waveforms of arbitrary, user-defined shapes. The desired signal is designed by the user, loaded into the waveform generator memory, and output through a DAC. |
|
| bandwidth |
The measure of a circuit or transmission channel to pass a signal without significant attenuation over a range of frequencies. Bandwidth can also refer to the information rate (in bits per second) that can pass through a circuit or transmission channel. |
| baseband signal |
See message signal. |
|
| carrier |
The signal that carries the information encoded or modulated on it. Typically, the carrier is a fixed frequency sine wave, which may be amplitude-, phase-, or frequency- modulated. |
| carrier frequency |
The frequency of the carrier signal that is a sinusoidal signal upon which the desired signal to be transmitted is modulated. The sinusoidal signal "carries" the modulation. |
| center frequency |
The frequency of the middle of the bandwidth of a channel. |
| CW |
continuous wave—A continuous sine wave that is the carrier wave in a radio transmission. |
|
| DAC |
digital-to-analog converter—An electronic device, often an integrated circuit, that converts a digital number into a corresponding analog voltage or current. |
| DDS |
direct digital synthesis—A signal generation technique that yields very high-frequency resolution. |
| DMA |
direct memory access—Method by which data can be transferred to/from computer memory from/to a device or memory on the bus while the processor performs another task. |
| digital modulation |
A technique for encoding digital data on a carrier frequency. |
| downconverter |
A signal conditioning device that converts a specific band of high-frequency (RF) signals to lower, more manageable IF frequencies that can be digitized. |
| DUC |
digital upconverter |
|
| EVM |
error vector magnitude—A measurement of demodulator performance in the presence of impairments. The soft symbol decisions obtained after decimating the recovered waveform at the demodulator output are compared against the ideal symbol locations. The root mean square (RMS) error vector magnitude and phase error are used to determine the EVM measurement over a window of N demodulated symbols. |
|
| FIR |
finite-impulse response—Used to describe a filter with no feedback elements. |
| FM |
frequency modulation |
| FSK |
frequency-shift keying—A type of frequency modulation which assigns bit values to discrete frequency levels. |
| frequency deviation | Refers to the maximum absolute difference, during a specified period, between the instantaneous frequency of the modulated wave and the carrier frequency. |
|
| IF |
intermediate frequency—Refers to the signal passed from the AWG module front panel CH 0 SMA connector to the upconverter module front panel INPUT SMA connector. This signal is upconverted to the requested RF output signal. |
| IQ signal |
A control signal for changing an RF carrier signal. |
|
| low-pass filter |
A circuit that attenuates the high-frequency components in an analog signal and only passes low frequencies. For imaging, a low-pass filter removes detail and blurs the image. |
|
| message signal |
Contains the data for transmission. The message signal is used to modulate the carrier wave to create the modulated wave for transmission. The message signal data is recovered from the modulated wave by a process of demodulation. The message signal is often referred to as the baseband signal or the information signal. |
| modulated wave |
The signal for transmission, which consists of the carrier wave modulated by the message signal. The message signal is recovered by the receiver through a process of demodulation. |
| modulation |
A process, or the result of a process, by which characteristics of a carrier wave are altered according to information in the information signal to give rise to a modulated wave, which is transmitted. |
| MER |
modulation error ratio—A measure of the signal-to-noise ratio (SNR) in a digitally modulated signal. Like SNR, MER is usually expressed in dB. |
| module |
Refers to the NI 5650/5651/5652 hardware, or to one of the two hardware components of the NI 5670/5671/5672 RF signal generator: the AWG module or the upconverter module. |
| MSK |
minimum shift keying—A subtype of FSK modulation. MSK uses a half-cycle sinusoidal pulse, making the phase change linear and keeping side lobes low to control adjacent-channel interference. |
| MXI |
Multisystem Xtension Interface—A high-speed serial interface bus designed
to connect computers to PXI, or to connect multiple PXI chassis. In this
document, MXI refers to NI MXI-3 or MXI-4 systems. |
|
| NCO |
numerically controlled oscillator—An oscillator that has a frequency that is controlled by a digital pattern. |
| NI 5421/5441/5442 |
NI 5421/5441/5442 refers to the AWG module included with the NI 5610 upconverter
module to make up the NI 5670/5671/5672. Supported AWG modules include the
NI PXI-5421 or NI PXI-5441. |
| NI 5650/5651/5652 |
NI 5650/5651/5652 refers to the NI PXI-5650, NI PXI-5651, or NI PXI-5652 RF
signal generators. These devices consist of a single PXI hardware module. |
| NI 5670/5671/5672 |
NI 5670/5671/5672 refers to the NI PXI-5670, NI PXI-5671, or NI PXIe-5672 RF signal
generators. The NI 5670/5671/5672 instruments are comprised of an upconverter
hardware module, an AWG hardware module, and the NI-RFSG instrument
driver. There is no single physical device labeled “NI PXI-5670,” “NI PXI-5671,” or
“NI PXIe-5672.” |
|
| OCXO |
oven-controlled crystal oscillator |
| OOK |
on-off keying—A modulation scheme which consists of keying a sinusoidal carrier signal on and off with a unipolar binary signal. |
| OSP |
onboard signal processing |
|
| phase noise |
Noise in a carrier signal due to phase and frequency modulation in the signal. Phase noise is normally very close to the carrier, and is measured in decibels relative to the carrier frequency (dBc). |
| PLL |
phase-locked loop—An electronic circuit which forces an output frequency to be locked to the same phase as a reference frequency. |
| PRBS |
pseudorandom bit sequence |
| PSD |
power spectral density—The power of a signal measured in the frequency domain and normalized to a 1 Hz bandwidth. |
| PCI Express |
PCI Express eXtensions for Instrumentation—The PXI implentation of PCI Express, a scalable full-simplex serial bus standard that operates at 2.5 Gbps and offers both asynchronous and isochronous data transfers. |
| PXI Express-Compatible Module |
A modified PXI module that is compatible with existing PXI chassis slots and PXY hybrid chassis slots. PXI Express-comptabile modules preserve hardware and software compatibility, with the exception of local bus features. |
|
| SFDR |
spurious free dynamic range—The separation or distance, expressed in dB, from the amplitude of the fundamental frequency and the next highest spur. |
| SINAD |
signal-to-noise distortion |
| SMA |
A small type of threaded coaxial signal connector typically used in higher frequency applications. |
| SMB |
sub-miniature type B—A small coaxial signal connector typically used in high-frequency applications. SMC uses a threaded connector, while the SMB "snaps" to the mating connector. |
| SMC |
sub-miniature type C—A small coaxial signal connector typpically used in high-frequency applications. SMC uses a threaded connector, while the SMB "snaps" to the mating connector. |
| SNR | signal-to-noise ratio—The ratio of the desired signal amplitude to the noise signal amplitude at a given point in time. SNR is expressed as 20 times the logarithm of the amplitude ratio, or 10 times the logarithm of the power ratio. SNR is usually expressed in dB and in terms of peak values for impulse noise and root-mean-square values for random noise. In defining or specifying the SNR, specify the signal and noise characterizations, for example, peak-signal-to-peak-noise ratio to avoid ambiguity. |
|
| TOI |
third order intercept—The theoretical level at which the third order harmonic distortion component has the same level as the fundamental tone. |
| tuning speed | The time required by a signal to lose lock on one frequency and jump to another frequency within a given frequency tolerance.
|
|
| VCO |
voltage-controlled oscillator |
| VCXO |
voltage-controlled crystal oscillator |
| VSG |
vector signal generator |