Broadband RF Amplifier

Within an RF signal chain, there is often the need to provide some signal conditioning in incoming, outgoing, or through signals. One of the most needed signal conditioning methods is amplification of signal energy, which is the key function of RF Amplifiers. Signal amplification involves increasing the amplitude of a signal, this could imply voltage, current, or power amplitude depending on the type of amplifier. In the case of RF amplifiers, typically an RF amplifier’s gain is referenced to the physical concept of power, and given in decibels per watt, or dB.

Power is the physical transition of energy over time, or joules per second (watt). For many consumer wireless applications a watt of RF power is relatively high, though some scientific and defense applications leverage kilowatts of RF power. Within a non-high power signal chain, RF power measured in watts, milliwatts, and microwatts is common. Decibels are a comparative quantity between two measures. Hence, a decibel per watt equates to a logarithmic scale where 0 dB is 1 watt of power, where +/- 3 dB from 0 dB equates roughly to doubling (positive) or halving (negative) the power, respectively.

This concept is important to understanding RF amplifiers as the key parameter for an RF amplifier is gain, which is given in dB. This gain refers to the comparison of the incoming power level to the outgoing power level from a signal injected in the RF amplifiers input compared to the signal exiting the RF amplifier output port. For instance, a 15 dB gain RF amplifier will increase the signal power by 15 dB, or roughly 2x2x2x2x2 = 32 times the original signal power.

RF amplifiers have many limitations, which is where there are varieties of RF amplifier types available, each designed with attributes designed for certain applications or even general performance. One key limitation of an RF amplifier is that the amplifier will increase the power of all signals present at the input as long as they are within the frequency of operation of the amplifier. This includes amplifying noise and interference. Hence, many amplifiers are paired with filters at the input and/or output to minimize the external interference at the input or output of the amplifier. RF amplifiers also add their own internally generated noise to a signal, this is known as added noise. Additionally, RF amplifiers are nonlinear devices that also inject some distortion into a signal, especially if the amplifier is driven close to saturation.

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Omnidirectional antenna

In today’s interconnected world, omnidirectional antenna types have become essential tools for expanding connectivity. Ideal for both indoor and outdoor use, serve as reliable solutions for users who need wide-ranging signal coverage without the hassle of constant adjustments. Supporting applications from mobile networks to Wi-Fi connectivity, omni antennas provide the flexibility and dependable performance needed across diverse environments. In this post we will explore the different omnidirectional antenna types.

Full 360-Degree Coverage for Outdoor Environments

One of the main attractions of an omnidirectional antenna for outdoor use is its ability to broadcast and receive signals in a full 360-degree radius. This feature makes it an excellent choice for open, expansive areas where users or devices may be moving in multiple directions, such as in public safety communications, outdoor Wi-Fi networks, and even event broadcasting. With various models designed to withstand harsh outdoor conditions, an omnidirectional antenna for outdoor use is often mounted on towers or poles in locations that require robust connectivity.

Boosting Indoor Connectivity with High-Gain Antennas

When it comes to indoor applications, omnidirectional antennas are frequently used to ensure uniform Wi-Fi coverage throughout an office or home. A high-gain omnidirectional antenna is especially useful in environments with many devices competing for bandwidth, as its increased gain can strengthen connectivity over greater distances compared to a standard antenna. The higher the gain, the farther the signal can reach, which can be an invaluable feature in challenging environments, including large buildings, crowded office spaces, and warehouses.

Versatile Frequencies for Wi-Fi and GSM Antennas

Beyond Wi-Fi, there are omnidirectional antenna types specifically designed for mobile network frequencies like GSM. Wi-Fi and GSM omnidirectional antennas are commonly used in devices that need to switch between internet and cellular connections seamlessly. These antennas are compatible with various frequency bands, including VHF, WiMAX, GSM, ISM, and standard Wi-Fi. Having a versatile, wide-band omnidirectional antenna allows users to maintain connectivity across several types of networks, an advantage in urban and rural areas alike.

Choosing the Right Connector

An omnidirectional antenna with an N connector or SMA connector is also designed for practical use and easy installation. These connectors offer durable, high-quality connections that can support a wide range of devices, making them particularly popular in environments requiring dependable, long-term setups. An N connector is common for outdoor and high-power applications, while SMA connectors are typically found in lower power devices. The choice of connector can affect the performance and ease of installation, making it essential to select the right termination based on the specific installation needs and environment.

Radomes: From Fiberglass to Polycarb

An omni antenna has a radome – the protective outer cover or enclosure that shields its radiating elements from environmental factors. Valued for their robustness, fiberglass radomes provide excellent resistance to UV rays, temperature extremes, and high winds, which makes them ideal for harsh outdoor environments. PVC radomes are generally more cost-effective and offer moderate protection, but they lack the weather resistance of fiberglass, making them suitable for milder climates or indoor applications. ABS radomes are strong and impact-resistant but tend to have limited UV protection, which can make them more vulnerable to degradation in direct sunlight. Polycarbonate radomes are known for their exceptional impact resistance and strength, providing a tough outer layer that is often used in industrial settings where physical protection is a priority.

Final Thoughts

To summarize, omnidirectional antenna types are invaluable in today’s fast-paced, connectivity-driven world. Whether it’s wide-band omnidirectional antennas for covering large distances, Wi-Fi and GSM omni antennas for versatile indoor-outdoor connectivity, or a high-gain omni directional antennas for extended range, these devices provide unmatched flexibility and reliability. Utilizing the right Omnidirectional antenna types will help you achieve optimal results in your wireless network.

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Low Noise RF Amplifier

Throughout the signal chain and especially at a signal input stage, RF signals for communications and sensing can be extremely weak. RF Low Noise Amplifiers (LNAs) are the most common method for increasing the signal level of these very weak signals while minimizing the introduction of signal degrading factors. Of these signal degrading factors, added noise, added phase noise, and distortion are generally of the greatest concerns. However, the limited bandwidth of an LNA may also result in lost signal information.

The dynamic range of an RF system often depends on performance on an LNA near the signal input stage. This input stage can be a signal generator, antenna/probe, or possibly even over a length of lossy transmission line/waveguide path. Another use case for an LNA would be as a bi-directional amplifier. If multiple stages of amplification are needed, the added noise figure and distortion characteristics of the LNA become even more critical.

There is a trade-off in LNA performance with added noise figure, gain, bandwidth, linearity/distortion, size, complexity, cost, ruggedness, and longevity. It is possible to make a very high gain LNA with very low added noise, but this amplifier may have a very limited bandwidth. Conversely, a wide bandwidth LNA may have a good added noise figure but be of limited gain. Design of an LNA requires knowledge of the application and the priorities of the signal chain performance factors. For instance, it may be that the bandwidth requirements necessitate multiple gain stages to ensure wide bandwidth performance while achieving the necessary gain. However, it may be preferable to optimize the noise figure with a single High Gain Low Noise Amplifier stage and sacrifice some bandwidth while keeping a moderate gain level.

Other factors to consider may involve the portability of the LNA. Higher gain, power, and performance LNAs are often generally larger than lower performing LNAs. It may be necessary to use an LNA with poorer performance to retain some power margin. Higher frequency LNAs also tend to be less efficient than lower frequency LNAs, as operating at higher frequencies leads to greater RF losses. Hence, it may be necessary to use multiple LNAs that are optimized over different frequency ranges and multiplexers/filter banks to ensure the desired frequency range is adequately accounted for while meeting system level performance figures.

In terms of linearity, the output power for 1 dB compression/1 dB compression point (P1dB), saturated output power (Psat), and output third order intercept point (IP3) are the most common figures-of-merit (FOMs) considered.  Gain flatness and gain variation over temperature or other environmental factors may also be important for some applications that may be exposed to harsh environmental conditions, such as marine, aerospace, extreme climates, or space.

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High Gain RF Amplifier

RF sensing and communication applications often involve very weak signal levels. It is often necessary to use RF Amplifiers to increase the gain, or signal level, of these signals in order to digitize them or otherwise condition these signals to usable levels. However, there are a few trade-offs to consider when increasing a signal’s power level, especially at very high gain factors.

As with all performance parameters and signal quality factors, attempting to improve one factor/parameter tends to require sacrificing another, or several. For instance, the gain bandwidth product (GBP) is a figure of merit that compares the open-loop gain of an amplifier with the available bandwidth at that gain level. With many amplifiers, increasing the gain lowers the available bandwidth, while attempting to achieve a wide-bandwidth necessitates using lower gain. Bandwidth in this case is defined as the frequency range over which the amplifier gain is relatively flat.

There are also other considerations when attempting to optimize an amplifier for gain. These include noise and stability. Typically, higher gain amplifiers also introduce higher levels of added-noise figure. Even with very low added noise figure amplifiers, the noise of the signals will ultimately also be amplified just as much as the original signal. This is why filters are often used at various stages in signal conditioning to limit the amount of out-of-band noise energy. However, it is often very difficult to remove the in-band noise that is added by increasing the gain of a signal.

With stability, the higher gain amplifier typologies must be carefully designed to avoid becoming unstable over the specified input signal energy, loading, and frequency range. This includes accounting for dynamic factors over the entire specified range of the amplifier’s operation, such as temperature and other environmental factors. As this requires accounting for the behavior of the load, high gain/RF Power Amplifiers are often tested using load-pull and other methods that vary the load behavior to properly qualify an amplifier design.

Though many RF amplifiers are designed with a fixed gain profile, some are designed to vary the gain over a range. These amplifiers are known as RF Variable Gain Amplifiers (VGAs), and exhibit the same trade-offs and fixed gain amplifiers, but also present more nuanced performance. VGAs are often used in test and measurement applications or automated testing. However, there are many types of integrated VGAs used for radio and radar designs that may benefit from operating at varying gain levels either at the signal input stage or output stage.

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Custom Coaxial Cable Assembly

As more technology becomes electrified and wirelessly connected, there is an ever-growing need for more nuanced and diverse RF and high-speed digital interconnect. A key enabling technology for this are RF Coaxial Cable Assemblies that can be customized with different connector and cable types. Most standard coaxial cable assemblies are made with in-series connectors. Some are made with between-series connectors. This means that most coaxial cable assemblies have the same type of coaxial connector on both sides. However, there are many situations that may benefit from having different coaxial connector types on either end. Having a between-series coaxial cable assembly can eliminate the need for an adapter or two, and result in lower insertion loss and PIM response compared to alternative approaches.

Other cases arise where a particular cable configuration may be needed, with specific connectors and cable type, that are only offered in standard lengths that are not ideal for a given application. The length of a cable has a significant impact on the signal chain a cable is used in. For coaxial cables, the insertion loss, delay, and VSWR change with the length of a cable, specifically these factors increase with the length of a cable. For some applications that are trying to achieve optimal dynamic range, then it is desirable to have the exact length of cable that is necessary. This would minimize the insertion loss of a cable. In the case of delay, that is a function of the length as well, and some applications may need a very specific delay. A targeted delay can be achieved by knowing the per-unit-length reactance of a cable and choosing the appropriate length. If a desired cable doesn’t come in the exact length needed, either to minimize insertion loss and VSWR or to hit a targeted delay, then a user can either order a custom cable or attempt to fabricate their own cable.

Historically, ordering a custom coaxial cable has required consulting a coaxial cable manufacturer and going through a quoting process. In order to keep costs viable, an order of tens or hundreds of cables would be required, depending on the specialized features of the custom cables. Fortunately, there are now tools, such as The Cable Creator, which make the process of designing and ordering custom cables a simple online process that requires filling out a simple set of forms.

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