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A vector signal generator will typically use I/Q data alongside some programmed frequency to generate its signal. [8] And similarly a vector signal analyser can provide a stream of I/Q data in its output. Many modulation schemes, e.g. quadrature amplitude modulation rely heavily on I/Q.
For a sine wave modulation, the modulation index is seen to be the ratio of the peak frequency deviation of the carrier wave to the frequency of the modulating sine wave. If h ≪ 1 {\displaystyle h\ll 1} , the modulation is called narrowband FM (NFM), and its bandwidth is approximately 2 f m {\displaystyle 2f_{m}\,} .
Modulation is continuous phase 4 FSK, with 1.4648 Hz tone separation. An Agilent Modulation Domain Analyzer 53310A showing the narrow band 4-FSK signal produced by a Raspberry Pi. Occupied bandwidth is about 6 Hz; Synchronization is via a 162 bit pseudo-random sync vector. Each channel symbol conveys one sync bit (LSB) and one data bit (MSB).
In a frequency or phase modulated signal, the signal amplitude is constant, so the points lie on a circle around the origin. The carrier representing each symbol can be created by adding together different amounts of a cosine wave representing the "I" or in-phase carrier, and a sine wave, shifted by 90° from the I carrier called the "Q" or ...
Single-sideband modulation with full carrier (e.g. as used by CHU) J: Single-sideband with suppressed carrier (e.g. Shortwave utility and amateur stations) K: Pulse-amplitude modulation: L: Pulse-width modulation (e.g. as used by WWVB) M: Pulse-position modulation: N: Unmodulated carrier (steady, single-frequency signal) P: Sequence of pulses ...
A frequency spectrum plot showing intermodulation between two injected signals at 270 and 275 MHz (the large spikes). Visible intermodulation products are seen as small spurs at 280 MHz and 265 MHz. 3rd order intermodulation products (D3 and D4) are the result of nonlinear behavior of an amplifier.
Some satellites transmit several BPSK streams at the same frequency in quadrature, in a form of quadrature amplitude modulation. However, unlike typical QAM systems where a single bit stream is split into two, half-symbol-rate bit streams to improve spectral efficiency , the in-phase and quadrature components of GPS signals are modulated by ...
IQ imbalance is a performance-limiting issue in the design of a class of radio receivers known as direct conversion receivers. [a] These translate the received radio frequency (RF, or pass-band) signal directly from the carrier frequency to baseband using a single mixing stage.