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A radio frequency power amplifier (RF power amplifier) is a type of electronic amplifier that converts a low-power radio-frequency signal into a higher power signal. Typically, RF power amplifiers drive the antenna of a transmitter. In radio transmission, transmitter power output (TPO) is the actual amount of power (in watts) of radio frequency (RF) energy that a transmitter produces at its output. ... The radio antenna's design "focuses" the signal toward the horizon, creating gain and increasing the ERP. example of RF we look at RF transistors are designed to handle high-power radio frequency (RF) signals in devices such as: ... Radio transmitters. Television monitors. RF signals and measure a wide range of signal parameters. ... the capability to measure input and output power on a device, circuit, or system and compute a gain or loss. RF travel make For a 2.4 GHz transmission path to transmit 5 miles, you would need antennas at 9.6 m (31 ft). For 900 MHz at 20 miles (32 km), you would need antennas of at least 46 m (152 ft) to achieve a good signal. In many practical settings, your transceivers may function with a lower antenna height, but the higher the better. The Received Signal Strength Indicator (RSSI) measures the amount of power present in a radio signal. It is an approximate value for signal strength received on an antenna. Measuring the signal strength at the receiving antenna is one way to determine the quality of a communication link. ... The RSSI is measured in dBm. A tuned amplifier that amplifies the signals commonly used in radio communications. Amplifier designs in the radio-frequency (RF) range differ significantly from conventional low-frequency circuit approaches; they consequently require special, distributed circuit considerations. In telecommunications, particularly in radio frequency, signal strength (also referred to as field strength) refers to the transmitter power output as received by a reference antenna at a distance from the transmitting antenna.
The main element of RF sensors based on diode detectors is that it uses diode rectifiers in order to produce an output. The RF power sensors using these diodes make it possible for RF power to get dissipated in a load. The detector then rectifies the voltage signal that appears across the load. RF in wireless communication : RF signals are easily generated, ranging 3kHz to 300GHz. These are used in wireless communication because of their property to penetrate through objects and t
ravel long distances. Radio communication depends on the wavelength, transmitter power, receiver quality, type, size and height of the antenna. There are basically three different types of wireless networks – WAN, LAN and PAN: Wireless Wide Area Networks (WWAN): WWANs are created through the use of mobile phone signals typically provided and maintained by specific mobile phone (cellular) service providers. RF detectors really work? Bug detectors, though slightly more complex than camera detectors, are fairly simple to use. Since bugs transmit RF (radio frequency) signals, bug detectors hone in on those signals and indicate that there is a bug present, by lighting up, making a sound, or both . RF detector detect ; A radio frequency (RF) detector is a device used to detect the presence of RF waves either in a wireless or wired (on RF Cable) physical transmission medium. They are also known as RF power detectors or RF responding detectors and are available as devices or modules. Hidden camera detector ; Hidden Camera Detector
Professional detectors offer two methods of finding a camera: either they look for that glint from the lens (much like using a flashlight or smartphone), or they detect RF broadcasts from a wireless camera. ... A camera lens should light up in the detector's viewfinder, making it easy to spot. Listening Device Detectors ; A radiofrequency detector can scan for transmitters. Turn off all wireless devices, including smartphones and routers, then slowly and carefully move the bug detector around your home. Anything that's broadcasting a radio signal will be found.
RF power amplifier
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A radio frequency power amplifier (RF power amplifier) is a type of electronic amplifier that converts a low-power radio-frequency signal into a higher power signal. Typically, RF power amplifiers drive the antenna of a transmitter. Design goals often include gain, power output, bandwidth, power efficiency, linearity (low signal compression at rated output), input and output impedance matching, and heat dissipation.
The basic applications of the RF power amplifier include driving to another high power source, driving a transmitting antenna and exciting microwave cavity resonators. Among these applications, driving transmitter antennas is most well known. The transmitter–receivers are used not only for voice and data communication but also for weather sensing (in the form of a radar).
RF power amplifiers using LDMOS (laterally diffused MOSFET) are the most widely used power semiconductor devices in wireless telecommunication networks, particularly mobile networks. LDMOS-based RF power amplifiers are widely used in digital mobile networks such as 2G, 3G, and 4G.
Concepts of RF Power Amplification
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Introduction
RF Power Amplifier design is a complicated task, which very often involves a team of engineers working on its different aspects (system design, circuit implementation and testing, mechanical design, control circuitry – to name a few). In order to synchronize their efforts, all team members have to have a clear understanding of the common goals and methods of their solution.
These notes describe basic amplifier requirements, mention approaches for meeting them, and briefly discuss a design flow. To keep them useful for all team members (regardless of their specialty or experience), formulas were avoided in the text and just a few of them are given in the appendix. For the same reason references were deliberately omitted: those who are interested in them can Google the subject or request them from the author.
Power Amplifier Requirements
The RF Power Amplifier (PA) is the last component of a transmitter chain. The purpose of a transmitter is to deliver an RF signal with required properties and specified power level to the antenna; and the need for the PA is in amplification of that signal to the level expected at antenna port.
That is, in order to do the job, the PA has to meet the following requirements:
It has to have sufficient Gain – to amplify RF signal to the level expected at Antenna Port. It is expressed as the difference between input and output RF powers.
It has to have sufficient Power Handling Capability – to be able to sustain a RF power level expected by the Antenna Port. Sometimes it is expressed as “dissipated power”, however for high power RF transistors it is often given as “Saturated Power” level.
It has to be distortion-free – in order for a system’s receiver to be able to recognize radiated signal. It is expressed as a degree of linearity.
It has to be stable – to avoid a creation of oscillations over anticipated variations of external conditions (that is, changes in temperature, load, frequency, DC and RF powers)
In addition, it is preferable that PA requirements are to be met efficiently. It is needed to avoid wasting of DC power, and/or to preserve the battery drainage. The problem with efficient amplifiers though, is that they do introduce additional distortions which increase with increasing efficiency. In order to deal with this issue, a number of linearization techniques have been developed. Amplifiers are divided into different classes (Class A to C for controlled current source and Class D and above for switched mode amplifiers) and linearization, specific for a given class, is applied.
All these requirements have to be met over the frequency band of operation (which might be 3-to-5 times wider than the occupied bandwidths if linearization techniques are to be used).
A detailed description of requirements is given below.
1. Gain
For a Power Amplifier, gain is defined as the difference between the power of the RF signal applied to PA input and the one delivered to the antenna port. While this property is the most important for the PA (it is the purpose of Power Amplifiers to create Gain), its actual value is of a lesser importance. Really, the gain of a last stage could be easily increased by adding extra preamplifiers preceding the final stage of a Power Amplifier. That is, the value of the Gain could be reduced for the sake of achieving other parameters (better match, linearity or efficiency). Very often two Gain values are included on PA spec sheets – they are a small signal gain (that is, gain at the significantly reduced level of an input signal; expressed as S21) and a large signal gain (gain at 1 dB compression point).
2. Output Power
Power Handling Capability is defined as the maximum power that an amplifier can handle without damage. Its value depends on the size and configuration of a transistor’s die and the proper application of cooling. This parameter should be large enough to sustain an RF power level expected by the Antenna Port. Sometimes it is expressed as “dissipated power” (which is the product of a current flowing through collector/drain and the voltage across the device); however, for high power transistors it is usually given as “output power at 1 dB Compression Point” or “Saturated Power.”
3. Linearity
Linearity is the measure of an amplifier’s distortions. Distortions are happening when RF signals with variable envelopes are applied to a nonlinear amplifier; they have to be low enough for the system’s receiver to recognize what the transmitter is sending. Mathematically, the distortions are realized as an interaction between additional spectral components created by the amplifier’s nonlinear transfer function (I-V DC curves).
For CW signals their measure is Compression Point or Intercept Point; for digitally modulated signals the figures of merit are Adjacent Channel Power (ACP – the measure of out-of-band interference) and Error Vector Magnitude (EVM – the measure of in-channel distortions). Distortions can be compensated by the application of products with the same amplitude and the opposite polarity to undesirable ones – the process which is called “linearization.”
There are two basic approaches to linearization – one of them is called Feedback, where the corrections for creating a distortion-free operation are done at the amplifier’s input (predistorters are operating on this principle), and the other is Feed-Forward, where the corrections are applied to the output of the amplifier. The first approach is cheaper, however it cannot compensate for distortions from heavily compressed amplifiers (above 1 dB compression point).
Generic math formulas are given in the appendix.
4. Efficiency
Efficiency is a measure of DC energy loss when it is transferred to RF power. In hand-held units, an inefficient PA is draining the battery and producing excessive heat; in high-power stationary units it requires complicated cooling systems and increases the cost of operation.
However having ideal sinusoidal RF signal at an amplifier’s output (like in Class A amplifiers) makes the PA lose 50% of its DC power by repeating redundant (positive and negative) information about amplitudes of Voltage and Current; mathematically it is shown by calculating Average Powers, expressed as integrals of instantaneous powers for DC (which is constant) and RF (which is proportional to sin2[t]).
In order to increase efficiency, the redundancy of Voltage/Current amplitudes has to be eliminated, which is done with the introduction of a Class B amplifier. In this class a conduction angle is reduced by a biasing amplifier to the origin of its transfer function, which makes the PA transfer only half (positive OR negative) of input RF sinusoids. However, due to the nonlinearities of transfer function (especially pronounced at its origin) – maximum efficiency for this method would not exceed 78%.
A better method to increase efficiency is to use a switch modulated by input RF signal. The DC supply of that switch, expressed as Idc*Vdc, is providing a required value for RF output power (when the switch is opened – all DC power is applied to the output load, when it is closed – none is coming to that load; so all DC is applied to the load at intervals directed by input RF data stream). Theoretically this method provides 100% efficiency; the Gain in this model of operation is defined as before (the difference between input and output RF powers); it works because output DC power is higher than input RF one.
The obvious issue with this method, however, is that all variations of an input amplitude are lost – so for variable envelopes, one needs to use alternative means of their recovery. Examples of these means are LINC (“Linear amplification with Nonlinear Components” – a method based on idea that any amplitude-modulated signal can be expressed as a sum of two different constant-envelope but phase-modulated signals) and EER (”Envelope Elimination and Restoration” – a method which detects an amplitude of an RF signal, amplifies a phase portion of the RF input signal, and modulates the resulting signal by detected amplitude variation).
In order to keep an amplifier’s high efficiency over the range of output powers (vs. achieving it only at the highest level) a technique called Load Modulation is used. For switched amplifiers included in LINC system it is achieved by combining signals from each branch on non-isolated power combiners; however this technique is applied to non-switched amplifiers, too. It is called a Doherty amplifier (the idea of which is to combine very efficient and very linear amplifier on one modulated load), and it allows a reasonable compromise between linearity and efficiency.
5. Stability
The RF Power Amplifier has to be stable (that is, oscillation free) over its operational range (over variations in temperature, frequencies, and power levels). Oscillations are caused by a positive feedback from the amplifier’s output; one has to be careful to avoid them or to dump them with additional circuitry.
For small signal operations, stable conditions are found from so-called “Stability Factor,” which is a formula derived from S-parameters (parameters describing transfer characteristics of a linear circuit). However, for large signal operations (that is, the most important area of Power Amplifier’s operation) stability has to be determined from Load Pull measurements.
Design Flow
The typical design of an RF Power Amplifier for a Base Station starts from the requirements supplied by the customer. Based on power and frequency requirements, the output transistors (as a rule – it is a pair of transistors) are to be chosen. Then, based on a budget and requirements, the amplifier’s configuration and class are determined. Input and output matching circuits are designed from load-pull contours, either measured or provided with the transistor’s data sheets. Initial (small signal) simulation of matching circuitry is done based on ideal components and CW input signal. Initial verification of small signal simulations is done on demo boards, provided by the transistors’ manufacturers.
Customer requirements should also include a form factor for the amplifier which is a starting point for a mechanical team working on a design of enclosure. From this design an allocated room for a final stage of Power Amplifier is found. Knowing that, a preliminary layout is created and simulated using a large signal simulation with the input waveform supplied by the customer. The first round of simulations is done with still ideal components; at the next round – all known parasitics are to be included. The goal of this simulation is to come up with a PCB layout. When satisfactory results are achieved, EM simulation is conducted in order to include an influence of the enclosure (metal walls and cover) on the layout.
The control circuitry team applies their firmware and hardware to the amplifier’s prototype assembled on demo boards. They are to build their final version to the form factor given to them by the mechanical team.
Finally, the prototype of the amplifier is assembled into the required enclosure, fine-tuned and then tested using a customer-supplied waveform.
In the RF signal chain, the power amplifier (PA) is the active element located between the transmitter signal chain circuitry and the antenna, Figure 1. It is often a single discrete component, one with requirements and parameters which differ from those of much of the transmit chain as well as the receiver circuitry.
Many Applications
General-purpose RF amplifiers are needed in virtually all wireless designs. Below is just a sample of the broad usage:
4G FDD and TDD base stations
5G base stations
Wireless repeaters
Distributed antenna systems
Infrastructure point-to-point radios
Public safety wireless equipment
Military radios
Test and measurement equipment
RF Amplifier Specifications
These are the features and specifications to consider in selecting an all-purpose linear RF amplifier.
Frequency range: The broader the better for an all-purpose part. Most designs are in the 500-MHz to near 5-GHz range to cover most applications.
Gain: This depends on the application, but something in the 10- to 20-dB range is useful. And you want that gain to be the same over a wide frequency range. In most RF amplifiers, the gain will vary somewhat over a wide frequency range. Look for an amplifier with gain flatness over segments over a ±100-MHz range that’s as low as possible, less than about ±0.2 dB.
Input/output impedance: 50 Ω, of course. A must standard impedance spec for most RF signal chains.
Noise figure: Noise levels are high at these high frequencies. So, noise figure (NF) is usually critical. Remember that NF is a measure of how much noise the amplifier produces. It’s the ratio of the signal-to-noise (S/N or SNR) ratio of the amp input to the signal-to-noise (S/N or SNR) ratio of the amp output expressed in dB.
NF = 10log (SNR in/SNR out)
A signal chain that adds no noise would have a 0-dB NF. Anything less than about 3 dB is good at these frequencies; the lower the better. Seek out 2 dB as a goal.
Output power: This is the maximum power output possible with a 50-Ω load at the highest supply voltage. It’s usually given in dBm, referenced to 1 mW. The typical range is typically 12 to 28 dBm.
Third-order intercept and 1-dB compression points: The third-order intercept (IP3) and 1-dB compression (P1dB) points are measures of the linearity and efficiency in an amplifier used for power gain. With most wireless standards using OFDM, CDMA, or some other broadband modulation scheme, good linearity is essential for maximum retention of the data details and best bandwidth usage.
As you increase the input power to an amplifier, its output power will rise linearly. At some point the output will begin to flatten or compress, indicating distortion is occurring.
Solid-state technology: Amplifiers at these high frequency ranges can be made of CMOS silicon, but more likely they’re made with gallium arsenide (GaAs) or silicon germanium (SiGe). SiGe is generally the more reliable of the two. These compound semiconductors generally perform better than silicon at the higher frequencies.
DC power: Most IC RF amplifiers operate from a supply voltage in the 1.8- to 6-V range. Current levels vary with supply voltage and the power generated and can range from 20 mA to over 100 mA. If the amplifier has a standby or low-power mode, current level should drop to no more than a few milliamps.
Packaging: Virtually all available amps are surface-mount in tiny packages. DFN and SOT-89 are common, but others are used. Sizes range from 5 × 5 mm down to 2 × 2 mm.
Temperature: Most cover the range from −40°C to +85°C or +105°C.
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RF AMPLIFIER EFFICIENCY
BACKGROUND
► The RF Front End (RFFE) is primarily judged by cost, and 4 technical parameters:
1. Output Power
2. Frequency/Bandwidth
3. Linearity
4. Energy Efficiency
► Energy Efficiency is the differentiator
► Usually, the Transmitter/PA consumes the greatest amount of power in the radio, and is the
focus for much of the Energy Efficiency development.
DEFICIENCY & LOSS :
► All of the circuit components are lossy,
dissipating power, reducing energy efficiency.
► Most power losses occur in the device (the
controlled current source) itself.
► Simultaneous existence of voltage across,
and current through, the device.
► Improvements in energy efficiency are
generally made by:
1. Better semiconductor technology
2. Efficiency enhancement schemes
FUNDAMENTAL TECHNIQUES
► All techniques for improving efficiency of a
device can be broken down and classified:
1. Load Modulation
2. Supply Modulation
3. Waveform Engineering
► Not all enhancement schemes leverage each
technique to the same extent.
► Different device technologies exhibit different
sensitivities to the techniques.
► Perfectly implemented schemes do not
necessarily fully leverage device capabilities.
LOAD MODULATION
► In Load Modulation, the load impedance
presented to (especially the fundamental
frequency) is modified.
► Generally, maximise the voltage swing, the
peak-to-peak voltage, across the device.
SUPPLY MODULATION
► In Supply Modulation, the supply voltage to
the device is modified.
► Generally, the goal is to ensure that the
minimum voltage in the RF envelope
approaches zero.
WAVEFORM ENGINEERING
► In Waveform Engineering, the shapes of the
RF waveforms are modified .
THEORETICAL LIMIT: MAXIMALLY EFFICIENT
► By applying all 3 techniques optimally, the Maximally Efficient Amplifier can be defined
► Squared-up Voltage and Current waveforms
1. Dissipation in the device is zero, but not necessarily in the other components
2. Anyway, nothing said about how those waveforms are created
► What practical steps can be taken?
SUFFICIENTLY EFFICIENT: PRACTICAL LIMIT
► Harmonic Load-Pull measurements, over a
range of bias conditions, can explore device
performance potential.
► In the worst case, see how much performance
is missing with the chosen implementation.
► Alternatively, for example:
1. Identify a complimentary, additional,
technique.
2. Identify the most suitable, existing,
known, scheme before designing.
3. Implement the device in a novel, highly
optimised, scheme.
CONCLUSIONS
► Typical off-the-shelf Devices are capable of much better performance than off-the-shelf
Enhancement Schemes would have you believe.
► Performing a comprehensive, harmonic Load-pull measurement on a device or technology will,
as a minimum, allow you to see just how much performance is missing.
► If efficient RFFE development is your lifeblood, understand which of the 3 fundamental
techniques work best for your technology and application. Develop schemes that better leverage them .
RF SATCOM design :
The energy efficiency of an RF frontend (RFFE) is a vital characteristic,
whether a radio is battery or mains
powered. For battery powered, reducing the maximum current drawn from the
battery increases the time between charges.
For mains powered, important properties
such as size, weight and power are dictated
by the RFFE efficiency. Consequently, many
amplifier architectures and inventions have
been developed to minimize wasted energy
in the transmitter. Although improving efficiency, some of these rely on theoretically
impossible modes of operation, and some fail to fully use
the device’s capabilities.
fundamental research in RF technology for satellite communication.
RF SATELLITE COMMUNICATION?
Ecosyatem design :
Within this ecosystem we like to act as your preferred partner for applied research and technology developments to enable future design . the focus design is on phased array antenna systems and the building blocks they encompass. Whether you need a break-through step in MMIC design using GaN technology, multipaction-free analogue front-end design, wide steering phased antenna design or RF lens antennas, you can rely on TNO to translate state-of-the art research results into new SatCom technology.
MMIC DESIGN AND TESTING
the design and testing of Monolithic Microwave Integrated Circuits (MMICs) in GaAs, GaN and SiGe technology. MMICs designs have been successful, ranging from L-band to W-band, with the focus on components for phased array radar front-ends and telecommunication. Examples of such components are high-power amplifiers, multi-function chips (beamformers), mixers, and low-noise amplifiers.
FRONT-END ELECTRONICS / BEAM FORMING NETWORK
For RF and µWave communication systems, Front-End electronics is planning design to ranging from the synthesised RF/µWave signal generation, specific modulation (data/frequency) and power amplification for the transmit signal to low noise amplification, demodulation and high-speed sampling/digitization of the receive signal. TNO has a strong and long heritage in designing such Front-End electronics for all kinds of Radar and Communication systems, optimised for the specific requirements of the application, either for steerable ‘single-beam’ as well as for ‘multi-beam’ array systems.
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RF for the future of life as the basis for the language of telecommunications
Electronics base station keeping teritory
SMART ELECTRONICS WITH TIME WINDOWS
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