Cat5e Shielded | RF Amplifiers | Cellular Repeate | Wireless Products

Type of coax cables used affects their use and longevity. Inferior quality cables can cause greater damage when used commercially on a distribution system. Hence it is important to select the right quality cables to ensure that you do not face any problems in future because of their faulty make. However it becomes really difficult to judge the quality of the cable just based on their manufacturing details as most of the times quantifiable data regarding their performance is not available.

To make things easier you can always rely on different types of cables available to make it easier for you to select the right type of cable based on your requirements. Whenever you need to buy new cable just go through the specifications and you should be able to buy the right type of it. Alphabetically coax cables are of 4 different types A, B, C and D.

Type A: More commonly known as semi-airspaced dielectric coax cables have longitudinal space running through it and so the popular name.

Type B: Though they look similar to type A coax cables, what differentiates them from type A cables is the foam used in their making. They are superior to type A as they last longer and are more robust. Previously manufactured type B cables easily soaked in moisture which ultimately affected their performance, however recent time cables come with a promise of better quality and higher level moisture resistance.

Type C: Popularly sold as “satellite downlead” Type C coax cables consists of low density copper braid and the screen is wrapped in very thin (not visible to the naked eye) silver colored material. Distinct quality of these coax cables is that the dielectric slides easily inside the screen, hence one has to be cautious when installing them.

Type ‘D’: Also known as “low loss cables” to disparate them from other similar cables used in VHF. Though you can find them in white sheath, they basically have brown sheath.

Most of the wireless systems are built using voltage controlled oscillators to control the movement of the frequency from source to unit. As the name hints two oscillators are used in dual-conversion systems. While one fine tunes all the input channel frequencies other functions at a pre-determined single frequency. They can be used either as an IC, module or discrete component circuit however they are more frequently used as part of an IC or a discrete circuit due to the price constraints.

Discrete-feature of voltage controlled oscillators is that they offer greater freedom to enhance performance of system including phase noise, tuning range, current consumption, output power, cost etc. Usually voltage controlled oscillators cannot be adjusted on as required bases, hence the RF engineer is faced with the challenge to develop a VCO that can be assembled without making any adjustments, such a VCO is called trimless VCO.

Designing a trimless VCO is not easy as it needs combination of design fundamentals and up-to-date RF engineering skills to make sure that the design is properly centered and that the oscillator tunes to the desired frequency as and when variations occur in supply voltage, component values and temperature. Developing a practically feasible RF VCO would mean you need to consider all the different types of oscillator topologies available, but the best and the most profitable topology has been that of Colpitts common-collector topology.

If you want to develop a low cost, flexible and high performance voltage control oscillator then using inductor-capacitor (LC) tank circuit which also includes a low-cost varactor diode and surface mount inductor. Oscillation frequency changes with every change in the inductor or capacitor, parallel resonance circuit in the oscillator tank controls the oscillation frequency. Inductor and varactor can be used to implement parallel- or series-mode network type resonance.

RF power amplifiers fall into different classes based on their peculiar endurance, linearity and distortion levels. Class E is one of the finest types of RF power amplifiers used to achieve greater efficiency. What sets them apart is that the transistor in Class E amplifier acts as a switch with ON/OFF function. To avoid recurring high voltage and current fluctuations, load network controls the voltage and current waveforms in such a manner that power dissipation is lowest at all the times especially in between switching transitions.

Another feature which differentiates Class E RF power amplifiers from Class B and C is that they can function with reduced power losses by an approx factor of 2.3. If class B and C amplifiers have drain efficiency of 65% the same would be 85% in case of Class E amplifiers. Both fixed tuned operations and narrowband operations for frequencies as wide as 1.8:1 can be performed using Class-E amplifiers. They can be even designed to work as they are without needing any “fiddling” or “tweaking”.

Efficiency for a Class E RF power amplifier lies in the amount of output power it gives without wasting much power. Below are the 6 principles that help the amplifier achieve its maximum productivity:

• When “On” transistor in the amplifier acts as a low resistance closed switch ensuring that the voltage remains close to Zero even when the current flowing is high.
• When “Off” transistor in the amplifier acts as open switch and keeps the current at zero even when the voltage is high.
• Voltage of the transistor will not rise until the current returns to zero
• Voltage of the transistor will become zero even before the current starts to increase
• Transistor voltage remains zero before the switch is turned “ON”
• Voltage slope of the transistor also remains zero at the time of turn “ON”

When all these principles are adhered to the RF power amplifier does not face situations of immediate increase in voltage and current and so are able to function as expected for a longer duration of time.

For those who are less familiar with RF amplifiers, it is a device through which the input can be amplified for a much intensified output. Sound signals by themselves are really weak but can be made stronger using an amplifier. They come in many different types based on their design which indicates the circuitry within it and are represented through classes A, B, AB, C and D.

Class A: Very low distortion, highly inefficient is how you can define class a amplifiers. Distortion level in an amp depends on the transistor; transistors in class A are little bias, and they remain half ON even when the device is idle, lot of power is thus wasted. With this bias are they actually useful? Yes they are mainly used for circuits requiring less power as Class A RF amplifiers will then maintain low distortion. Some extremely discriminating listeners are often found using high end Class A amps.

Class B: Though these are more efficient than Class A amps they too suffer from crossover distortion which takes place when the level of signal is low. They are used in all those low cost designs where the sound quality required is not that high like pocket transistor radios or clock radio circuits (these devices now use IC amplifiers).

Class AB: As you might have guessed Class AB combines all the good things about Class A and Class B. It is the most common variety of RF amplifiers seen in home stereos. With these, low signal would mean worst distortion and usually lowest at the time when signal reaches clipping point. Class AB amplifiers are equipped with two slightly ON transistors to eliminate crossover distortion present in Class B amplifiers.

Class C: Tremendous distortion caused by Class C makes them unsuitable for using in audio circuits; so are used only in RF circuits. Even in RF circuits filters are used to ensure that the final signal received is acceptable. They are more efficient then all the above Classes.

Class D: Though Class D amplifiers have been around for more than 5 long decades they can be seen in recent time semiconductor devices only recently. Advance power capacity, speed and efficiency of latest semiconductors make it less expensive to use Class D amplifiers in them. While all the above mentioned Classes use semi conductor devices in linear mode Class D uses them in OFF and ON mode just like switches.

Performance of a high power RF amplifier depends on its resiliency to provide outstanding performance for a much longer period of time that is most likely to be more than 20 years. Resiliency of an amplifier is termed as ruggedness in the electronics world. Most of the amp manufacturers consider ruggedness as one of the most crucial aspects of their design process.

From times known silicon based technologies like bipolar or LDMOS have been used to manufacture high power RF amplifiers. Though they are cost effective, they have low ruggedness ratings. LDMOS has an integral damaging mechanism formed into the structure of the transistor which reduces the function of the amplifier at high operating voltage.

Checking Ruggedness:
At times power supplied to the amplifier can be really high, ruggedness refers to its ability to withhold the power mismatch condition and deliver expected results without any failure or long term degradation. High power amplifier is reliable only if it displays ability to handle huge power distribution internally in the active area without hindering its performance. Although no features or qualities can be used to determine ruggedness it is generally a function of magnitude and phase of the mismatch, the thermal dissipation properties of the amplifier and the output power level conditions.

Semi conductor device manufacturers gauge ruggedness in high power amplifiers differently. Some maintain that the amplifier is ok if the output remains the same under all circumstances. However this is not an appropriate measure because amplifiers manufactured using the Bipolar technology do deliver desired results though the test damages some of the cells. The result remains unaffected because other active cells provide the required power at a higher temperature, so the performance is not affected.

Few others specify that the amplifier can be considered as reliable so far as it does not show more than 20% shift in DC test parameters.

Cell phones keep you connected everywhere you go, however they have a limitation and that is they need appropriate signals to be able to connect you to others. When the signals are low or are not available then it is nothing less than an empty device of no use. You feel frustrated in situations like this, but now no more because now we have cellular repeater, a cell phone signal amplifier.

What is a cellular repeater? As commonly defined in the wireless telecommunications industry cellular repeater is a type of BDA (Bi-Directional Amplifier) used to improve cell phone reception with the means of a reception antenna, an internal rebroadcast antenna and a signal amplifier. They are a smaller version of the broadcast towers used by network providers to be implemented in a building. The best part of using them is that it is really easy to install, even you by yourself can do it.

Here is a step by step guide on installation of cellular repeater:

• Cellular repeaters are available in kits and can be bought from a nearby cellular store. Along with it you will also need some household tools and hardware supplies.
• You need to fit the repeater at a place where your cell phone shows maximum coverage. Hence ascertain the area in your building with maximum coverage by moving around with your cell phone, stop when it shows full network availability.
• Fix the “Donor” antenna bracket against the wall this can be done using few wooden screws and a screwdriver. Loosen the bracket at the top so as to fit in the donor base, tighten the collar once done.
• Now it is time to connect the coax cable to a power source, if you have one outside then this should not be a big problem. If not then you will have to look for the nearest power source to the donor inside the house; drill a hole into the wall, window or door; pass the cable through it and connect.
• Fix the BDA next to the power source, plug in the cord
• Fix the other end of the coax cable into the Donor and screw the coverage antenna on a central wall that is common for all the rooms in the house. Ensure that you fit the cable high on the wall so as to receive optimum benefit
• Fix the other end of the coax cable into the BDA output, run the cable up to the coverage antenna and fix it in the coax input given on the antenna.
• Do not leave the cable hanging down the walls fix it appropriately using “U” clamp staples and use silicone paste to seal all empty spaces around the holes.

Cables – they are everywhere we use them in one or other electrical appliances but what is special about Coax cables. An easy paradigm to understand them would be human body - just like arteries carry blood to different parts of our body cables are used to carry electricity needed to run different electric appliances. Coax cables are one among the many different types of cables available in the market. Though mainly used in computers they are also used in video and radio electronics. Its core objective is to transform electricity between the main power source and the disparate parts of the appliances.

How do you identify coax cables? Generally all cables consist of inner and outer layers, as you strip the outer layer in these cables you will notice that the inner layer consists of copper wire wrapped in white insulator which again has a copper screen layered over it. Number of copper wires in the inner layer can vary depending on its capacity; more wires would mean that the cable will be able to carry more electricity at a much faster speed.

White insulator is generally made of solid polyethylene mainly because it is less expensive and easily available. Copper screen consisting of braided copper wires is layered over the insulator for added flexibility. The outer layer consists of black plastic; it is an essential element of a cable as it traps the electricity inside the cable, so you do not get a shock when you touch the cable.

Though they have been traditionally used to carry electricity they are also made to carry radio signals as the inner copper wiring and the copper screen run on the same geometrical axis. It would be worth noting that it is because of this particular feature that these cables are called coaxial (having a common axis) cables. Outside magnetic forces can easily interrupt or terminate radio signals. However the coaxial nature of coax cables and the plastic cables which create a perfect vacuum inside do not allow the signals to escape and hence they are used for transmitting radio signals.