05-14-2023-1320 - A passband, Baseband, etc. (draft)

A passband is the range of frequencies or wavelengths that can pass through a filter. For example, a radio receiver contains a bandpass filter to select the frequency of the desired radio signal out of all the radio waves picked up by its antenna. The passband of a receiver is the range of frequencies it can receive when it is tuned into the desired frequency (channel).

A bandpass-filtered signal (that is, a signal with energy only in a passband), is known as a bandpass signal, in contrast to a baseband signal.^[1] The bandpass filter usually has two band-stop filters.

Filters

Unrestricted signal (upper diagram). Bandpass filter applied to signal (middle diagram). Resulting passband signal (bottom diagram). A(f) is the frequency function of the signal or filter in arbitrary units.

Passband modulation
Analog modulation
AM FM PM QAM SM SSB
Digital modulation
ASK APSK CPM FSK MFSK MSK OOK PPM PSK QAM SC-FDE TCM WDM
Hierarchical modulation
QAM WDM
Spread spectrum
CSS DSSS FHSS THSS
See also
Capacity-approaching codes Demodulation Line coding Modem AnM PoM PAM PCM PDM PWM ΔΣM OFDM FDM Multiplexing
v t e

In telecommunications, optics, and acoustics, a passband (a band-pass filtered signal) is the portion of the frequency spectrum that is transmitted (with minimum relative loss or maximum relative gain) by some filtering device. In other words, it is a band of frequencies which passes through some filter or a set of filters. The accompanying figure shows a schematic of a waveform being filtered by a bandpass filter consisting of a highpass and a lowpass filter.

Radio receivers generally include a tunable band-pass filter with a passband that is wide enough to accommodate the bandwidth of the radio signal transmitted by a single station.

Digital transmission

There are two main categories of digital communication transmission methods: baseband and passband.

• In baseband transmission, line coding is utilized, resulting in a pulse train or digital pulse amplitude modulated (PAM) signal. This is typically used over non-filtered wires such as fiber optical cables and short-range copper links, for example: V.29 (EIA/TIA-232), V.35, IEEE 802.3, SONET/SDH.
• In passband transmission, digital modulation methods are employed so that only a limited frequency range is used in some bandpass filtered channel. Passband transmission is typically utilized in wireless communication and in bandpass filtered channels such as POTS lines. It also allows for frequency-division multiplexing. The digital bitstream is converted first into an equivalent baseband signal, and then to a RF signal. On the receiver side a demodulator is used to detect the signal and reverse the modulation process. A combined equipment for modulation and demodulation is called a modem.

Details

This section does not cite any sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. (August 2018) (Learn how and when to remove this template message)

In general, there is an inverse relationship between the width of a filter's passband and the time required for the filter to respond to new inputs. Broad passbands yield faster response times.^{[citation needed]} This is a consequence of the mathematics of Fourier analysis.

The limiting frequencies of a passband are defined as those at which the relative intensity or power decreases to a specified fraction of the maximum intensity or power. This decrease in power is often specified to be the half-power points, i.e., 3 dB below the maximum power.

The difference between the limiting frequencies is called the bandwidth, and is expressed in hertz (in the optical regime, in nanometers or micrometers of differential wavelength).

The related term "bandpass" is an adjective that describes a type of filter or filtering process; it is frequently confused with "passband", which refers to the actual portion of affected spectrum. These two words are both compound words that follow the English rules of formation: the primary meaning is the latter part of the compound, while the modifier is the first part. Hence, one may correctly say 'A dual bandpass filter has two passbands'.

References

1. 
   

1. Belle A. Shenoi (2006). Introduction to digital signal processing and filter design. John Wiley and Sons. p. 120. ISBN 978-0-471-46482-2.

•  This article incorporates public domain material from Federal Standard 1037C. General Services Administration. (in support of MIL-STD-188).

Categories:

• Filter frequency response
• Physical layer protocols

 

https://en.wikipedia.org/wiki/Passband

In telecommunications and signal processing, baseband is the range of frequencies occupied by a signal that has not been modulated to higher frequencies.^[1] Baseband signals typically originate from transducers, converting some other variable into an electrical signal. For example, the electronic output of a microphone is a baseband signal that is analogous to the applied voice audio. In conventional analog radio broadcasting, the baseband audio signal is used to modulate an RF carrier signal of a much higher frequency.

A baseband signal may have frequency components going all the way down to DC, or at least it will have a high ratio bandwidth. A modulated baseband signal is called a passband signal. This occupies a higher range of frequencies and has a lower ratio and fractional bandwidth.

Various uses

Baseband signal

A baseband signal or lowpass signal is a signal that can include frequencies that are very near zero, by comparison with its highest frequency (for example, a sound waveform can be considered as a baseband signal, whereas a radio signal or any other modulated signal is not).^[2]

A baseband bandwidth is equal to the highest frequency of a signal or system, or an upper bound on such frequencies,^[3] for example the upper cut-off frequency of a low-pass filter. By contrast, passband bandwidth is the difference between a highest frequency and a nonzero lowest frequency.

Baseband channel

A baseband channel or lowpass channel (or system, or network) is a communication channel that can transfer frequencies that are very near zero.^[4] Examples are serial cables and local area networks (LANs), as opposed to passband channels such as radio frequency channels and passband filtered wires of the analog telephone network. Frequency division multiplexing (FDM) allows an analog telephone wire to carry a baseband telephone call, concurrently as one or several carrier-modulated telephone calls.

Digital baseband transmission

Main article: Line code

Digital baseband transmission, also known as line coding,^[5] aims at transferring a digital bit stream over baseband channel, typically an unfiltered wire, contrary to passband transmission, also known as carrier-modulated transmission.^[6] Passband transmission makes communication possible over a bandpass filtered channel, such as the telephone network local-loop or a band-limited wireless channel.^[7]

Baseband transmission in Ethernet

The word "BASE" in Ethernet physical layer standards, for example 10BASE5, 100BASE-TX and 1000BASE-SX, implies baseband digital transmission (i.e. that a line code and an unfiltered wire are used).^[8][9]

Baseband processor

A baseband processor also known as BP or BBP is used to process the down-converted digital signal to retrieve essential data for a wireless digital system. The baseband processing block in GNSS receivers is responsible for providing observable data: that is, code pseudo-ranges and carrier phase measurements, as well as navigation data.^[7]

Equivalent baseband signal

IQ modulation and demodulation

An equivalent baseband signal or equivalent lowpass signal is—in analog and digital modulation methods for (passband) signals with constant or varying carrier frequency (for example ASK, PSK QAM, and FSK)—a complex valued representation of the modulated physical signal (the so-called passband signal or RF signal). The equivalent baseband signal is ${\displaystyle Z(t)=I(t)+jQ(t)}$ where ${\displaystyle I(t)}$ is the inphase signal, ${\displaystyle Q(t)}$ the quadrature phase signal, and ${\displaystyle j}$ the imaginary unit. In a digital modulation method, the ${\displaystyle I(t)}$ and ${\displaystyle Q(t)}$ signals of each modulation symbol are evident from the constellation diagram. The frequency spectrum of this signal includes negative as well as positive frequencies. The physical passband signal corresponds to

${\displaystyle I(t)\cos (\omega t)-Q(t)\sin (\omega t)=\mathrm{R}\mathrm{e}\{Z(t)e^{j\omega t}\}}$

where ${\displaystyle \omega }$ is the carrier angular frequency in rad/s.^[10]

Modulation

A signal at baseband is often used to modulate a higher frequency carrier signal in order that it may be transmitted via radio. Modulation results in shifting the signal up to much higher frequencies (radio frequencies, or RF) than it originally spanned. A key consequence of the usual double-sideband amplitude modulation (AM) is that the range of frequencies the signal spans (its spectral bandwidth) is doubled. Thus, the RF bandwidth of a signal (measured from the lowest frequency as opposed to 0 Hz) is twice its baseband bandwidth. Steps may be taken to reduce this effect, such as single-sideband modulation. Conversely, some transmission schemes such as frequency modulation use even more bandwidth.

The figure below shows AM modulation:

Comparison of the equivalent baseband version of a signal and its AM-modulated (double-sideband) RF version, showing the typical doubling of the occupied bandwidth.

See also

Look up baseband in Wiktionary, the free dictionary.

• Complex envelope
• Broadband
• In-phase and quadrature components
• Narrowband
• Wideband

References

 

Jeff Rutenbeck, Tech Terms: What Every Telecommunications and Digital Media Professional Should Know, p. 24, CRC Press, 2012 ISBN 1136034501

Steven Alan Tretter (1995). Communication System Design Using Dsp Algorithms: With Laboratory Experiments for the TMS320C30. Springer. ISBN 0-306-45032-1.

Mischa Schwartz (1970). Information, Transmission, Modulation and Noise: A Unified Approach to Communication Systems. McGraw-Hill. ISBN 9780070557611.

Chris C. Bissell and David A. Chapman (1992). Digital Signal Transmission. Cambridge University Press. ISBN 0-521-42557-3.

Mikael Gustavsson and J. Jacob Wikner (2000). CMOS Data Converters for Communications. Springer. ISBN 0-7923-7780-X.

Jan W. M. Bergmans (1996). Digital Baseband Transmission and Recording. Springer. ISBN 0-7923-9775-4.

"Baseband Processing - Navipedia". gssc.esa.int. Retrieved 2022-07-04.

IEEE 802.3 1.2.3 Physical layer and media notation

"IEEE Get Program". standards.ieee.org. IEEE. Retrieved 29 March 2017.

10. Proakis, John G. Digital Communications, 4th edition. McGraw-Hill, 2001. p150

Authority control: National	Germany

Category:

• Signal processing

 

https://en.wikipedia.org/wiki/Baseband

https://en.wikipedia.org/wiki/Analytic_signal#Complex_envelope

https://en.wikipedia.org/wiki/Broadband

https://en.wikipedia.org/wiki/In-phase_and_quadrature_components

https://en.wikipedia.org/wiki/Narrowband

https://en.wikipedia.org/wiki/Wideband

https://en.wikipedia.org/wiki/Radiation_pattern

https://en.wikipedia.org/wiki/Photonic_integrated_circuit

https://en.wikipedia.org/wiki/Near-field_scanner

https://en.wikipedia.org/wiki/Baseband

https://en.wikipedia.org/wiki/Bandwidth_(signal_processing)#Fractional_bandwidth

https://en.wikipedia.org/wiki/Passband

https://en.wikipedia.org/wiki/Radio_frequency

https://en.wikipedia.org/wiki/Transducer

https://en.wikipedia.org/wiki/Ethernet_physical_layer

https://en.wikipedia.org/wiki/Baseband_processor

https://en.wikipedia.org/wiki/Amplitude_modulation

https://en.wikipedia.org/wiki/Sideband