Thread starter
chingkui
Start date
Dec 3,Tags
In summary, IF processing is more efficient, easier to decouple power supplies, and can handle more bandwidth than base-band processing.
chingkui
In the digital communication class I took, people talk about how to do detection and processing at the baseband. But from what I read, it seems that many systems do the signal processing at some intermediate frequency without mixing it all the way back to baseband. My questions are why and how:
1) Why would you want to process signal at IF band? wouldn't it be "easier" if you process baseband signal? And wouldn't the sampling rate be lower at baseband?
2) How exactly do you process the signal (such as detection, etc)? I know how you do it at baseband, but how do you accomplish the same thing with a signal oscillating at IF?
I have not yet been able to find the answer online and in books, I would greatly appreciate if anyone can point me to the right direction. Thanks.
JakeBrodskyPE
The answer to your question is that books don't usually discuss practicalities. Base-band processing may require significant gain across many octaves of bandwidth. This is not easy to do while keeping the power supply decoupled, and maintaining a good noise figure.
IF processing can handle a similar bandwidth with lower noise (the infamous 1/f flicker noise from many mixers is less at IF); it is easier to decouple the power supplies; and linearity is simpler.
So, unless there is a compelling reason why you want to do things at base-band (such as an A/D converter that you use for signal processing), IF processing is the typical way that many high performance receivers do their processing.
There are variants to IF processing such as using an image of the A/D converter, but that takes us down a rat-hole of discussions that people write papers and even books about.
Science Advisor
Gold Member
It all totally depends upon the particular system involved. The huge advantage of using an Intermediate Frequency in a receiver is that all channels can, on an individual basis, be mixed down and filtered through just one well defined filter (perhaps a crystal or SAW filter). I.F. 'processing' would normally just be limited to this filtering and, perhaps level / gain regulation, followed by demodulation / detection. But, as I have already said, the choices of what happens when and where are made on a system by system basis - there is no universal rule. Companding or surround sound processing would have to be done at baseband.
I think you may have an inappropriate idea of what constitutes 'baseband'. A baseband signal would normally be thought of as a signal that could come directly from a sound or video source - or that could be fed to a loudspeaker or monitor.
In all cases but high power AM transmissions, the modulation would be achieved at a convenient IF frequency and then up-converted to a required transmit frequency. AM (mf) transmitters very often actually modulate the kWs of carrier right at the transmitter output with enormous modulation transformers and modulation amplifiers. Great scary devices behind safety screens. This is much more efficient than using linear amplifiers to generate such high powers.
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rbj
i might suggest going to the USENET comp.dsp newsgroup and asking them. they'll help you flesh out the question. if it's a software radio, there are a few reasons for processing IF with DSP rather than processing the IF in analog.
Intermediate frequency (IF) signal processing refers to the manipulation and analysis of signals that have been translated to a specific intermediate frequency, typically in radio frequency (RF) systems. Baseband signal processing, on the other hand, deals with signals that have not been translated and are still in their original form.
Intermediate frequency is used in signal processing because it allows for easier and more efficient filtering, amplification, and demodulation of signals. By translating the signal to a specific intermediate frequency, it can be processed using standardized and specialized components, resulting in better overall performance.
Baseband signal processing has the advantage of being able to process the original signal without any translation, which can help preserve the quality of the signal. It also allows for a wider bandwidth and higher data rates compared to intermediate frequency processing.
Both intermediate frequency and baseband signal processing can be considered analog signal processing techniques. However, with the increasing use of digital communication systems, digital signal processing techniques have become more commonly used in both intermediate frequency and baseband processing. This allows for more precise and efficient manipulation of the signals.
Intermediate frequency processing is commonly used in radio frequency (RF) systems, such as in communication systems, radar systems, and satellite systems. Baseband signal processing is used in a variety of applications, including audio and video processing, data communications, and medical imaging systems.
The baseband unit (BBU) is another important component of the telecommunication infrastructure. Unlike the RRU which is located at the top of the tower, the BBU is located at the foot of the tower. In this article, we discuss, what BBU is, its functions, as well as its components.
Image: BBU
What Is a Baseband Unit?
The baseband is the original frequency spectrum of a transmission signal before it is modulated. Additionally, it can also be referred to as a method of data transmission where both analog and digital data are transferred through a single, non-multiplexed channel.
Image: Baseband Transmission
In a telecom system, a BBU processes baseband. The BBU and the RF processing unit (or RRU) are both components of a typical telecom station. Positioned within the equipment room, the BBU is connected to the RRU through optical fiber links. This facilitates a physical communication interface.
Components of the BBU
The BBU is made up of the following components which are all inserted into dedicated slots:
Image: Components of the BBU
LBBP
The acronym LBBP stands for LTE Baseband Processing Unit. LBBP can be found in different variations including LBBPa, LBBPb, and LBBPc in some series. In series like the Huawei BBU , the LBBP module is denoted as UBBP.
The difference between LBBP and UBBP is that LBBP is designed for LTE or 4G communication, while UBBP is designed for 2G and 3G communication. Nevertheless, they both have similar functions such as:
UMPT
UMPT, an abbreviation for Universal Main Processing and Transmission Unit, performs the following key functions:
UPEU
UPEU, an acronym for Universal Power and Environment Interface Unit, performs the following essential functions:
FAN
The Fan unit serves the dual purpose of heat dissipation from the BBU and the monitoring of inlet temperature. Furthermore, it regulates the rotational speed of the fans and communicates fan status information to the Universal Main Processing and Transmission Unit (UMPT) within the BBU.
Functions of BBU
Below are the functions of the BBU:
NOTE: A GPS sensor is built into the BBU to track its installation location. The GPS coordinates are routinely tracked and then sent to the control center of the telecommunications provider in the event that the BBU is removed without authorization.
Thread starter
chingkui
Start date
Dec 3,Tags
In summary, IF processing is more efficient, easier to decouple power supplies, and can handle more bandwidth than base-band processing.
chingkui
In the digital communication class I took, people talk about how to do detection and processing at the baseband. But from what I read, it seems that many systems do the signal processing at some intermediate frequency without mixing it all the way back to baseband. My questions are why and how:
1) Why would you want to process signal at IF band? wouldn't it be "easier" if you process baseband signal? And wouldn't the sampling rate be lower at baseband?
2) How exactly do you process the signal (such as detection, etc)? I know how you do it at baseband, but how do you accomplish the same thing with a signal oscillating at IF?
I have not yet been able to find the answer online and in books, I would greatly appreciate if anyone can point me to the right direction. Thanks.
JakeBrodskyPE
The answer to your question is that books don't usually discuss practicalities. Base-band processing may require significant gain across many octaves of bandwidth. This is not easy to do while keeping the power supply decoupled, and maintaining a good noise figure.
IF processing can handle a similar bandwidth with lower noise (the infamous 1/f flicker noise from many mixers is less at IF); it is easier to decouple the power supplies; and linearity is simpler.
So, unless there is a compelling reason why you want to do things at base-band (such as an A/D converter that you use for signal processing), IF processing is the typical way that many high performance receivers do their processing.
There are variants to IF processing such as using an image of the A/D converter, but that takes us down a rat-hole of discussions that people write papers and even books about.
Science Advisor
Gold Member
It all totally depends upon the particular system involved. The huge advantage of using an Intermediate Frequency in a receiver is that all channels can, on an individual basis, be mixed down and filtered through just one well defined filter (perhaps a crystal or SAW filter). I.F. 'processing' would normally just be limited to this filtering and, perhaps level / gain regulation, followed by demodulation / detection. But, as I have already said, the choices of what happens when and where are made on a system by system basis - there is no universal rule. Companding or surround sound processing would have to be done at baseband.
I think you may have an inappropriate idea of what constitutes 'baseband'. A baseband signal would normally be thought of as a signal that could come directly from a sound or video source - or that could be fed to a loudspeaker or monitor.
In all cases but high power AM transmissions, the modulation would be achieved at a convenient IF frequency and then up-converted to a required transmit frequency. AM (mf) transmitters very often actually modulate the kWs of carrier right at the transmitter output with enormous modulation transformers and modulation amplifiers. Great scary devices behind safety screens. This is much more efficient than using linear amplifiers to generate such high powers.
rbj
i might suggest going to the USENET comp.dsp newsgroup and asking them. they'll help you flesh out the question. if it's a software radio, there are a few reasons for processing IF with DSP rather than processing the IF in analog.
Intermediate frequency (IF) signal processing refers to the manipulation and analysis of signals that have been translated to a specific intermediate frequency, typically in radio frequency (RF) systems. Baseband signal processing, on the other hand, deals with signals that have not been translated and are still in their original form.
Intermediate frequency is used in signal processing because it allows for easier and more efficient filtering, amplification, and demodulation of signals. By translating the signal to a specific intermediate frequency, it can be processed using standardized and specialized components, resulting in better overall performance.
Baseband signal processing has the advantage of being able to process the original signal without any translation, which can help preserve the quality of the signal. It also allows for a wider bandwidth and higher data rates compared to intermediate frequency processing.
Both intermediate frequency and baseband signal processing can be considered analog signal processing techniques. However, with the increasing use of digital communication systems, digital signal processing techniques have become more commonly used in both intermediate frequency and baseband processing. This allows for more precise and efficient manipulation of the signals.
Intermediate frequency processing is commonly used in radio frequency (RF) systems, such as in communication systems, radar systems, and satellite systems. Baseband signal processing is used in a variety of applications, including audio and video processing, data communications, and medical imaging systems.
The baseband unit (BBU) is another important component of the telecommunication infrastructure. Unlike the RRU which is located at the top of the tower, the BBU is located at the foot of the tower. In this article, we discuss, what BBU is, its functions, as well as its components.
Image: BBU
What Is a Baseband Unit?
The baseband is the original frequency spectrum of a transmission signal before it is modulated. Additionally, it can also be referred to as a method of data transmission where both analog and digital data are transferred through a single, non-multiplexed channel.
Image: Baseband Transmission
In a telecom system, a BBU processes baseband. The BBU and the RF processing unit (or RRU) are both components of a typical telecom station. Positioned within the equipment room, the BBU is connected to the RRU through optical fiber links. This facilitates a physical communication interface.
Components of the BBU
The BBU is made up of the following components which are all inserted into dedicated slots:
Image: Components of the BBU
LBBP
The acronym LBBP stands for LTE Baseband Processing Unit. LBBP can be found in different variations including LBBPa, LBBPb, and LBBPc in some series. In series like the Huawei BBU , the LBBP module is denoted as UBBP.
The difference between LBBP and UBBP is that LBBP is designed for LTE or 4G communication, while UBBP is designed for 2G and 3G communication. Nevertheless, they both have similar functions such as:
UMPT
UMPT, an abbreviation for Universal Main Processing and Transmission Unit, performs the following key functions:
UPEU
UPEU, an acronym for Universal Power and Environment Interface Unit, performs the following essential functions:
FAN
The Fan unit serves the dual purpose of heat dissipation from the BBU and the monitoring of inlet temperature. Furthermore, it regulates the rotational speed of the fans and communicates fan status information to the Universal Main Processing and Transmission Unit (UMPT) within the BBU.
Functions of BBU
Below are the functions of the BBU:
NOTE: A GPS sensor is built into the BBU to track its installation location. The GPS coordinates are routinely tracked and then sent to the control center of the telecommunications provider in the event that the BBU is removed without authorization.