Cat5e Shielded | RF Amplifiers | Cellular Repeate | Wireless Products

Coax Cable is a type of wire that consists of a center wire surrounded by insulating materials and then a grounded shield of braided wire. Coax cable is a cable type used to carry radio signals, video signals, measurement signals and data signals. The shield minimizes electrical and radio frequency interference.

Coax cabling is the primary type of cabling used by the cable television industry and is also widely used for computer networks, such as Ethernet. It is more expensive than standard telephone wire; it is much less susceptible to interference and can carry much more data than a telephone wire.

A coax cable consists of two conductors that share a common axis. The inner conductor is typically a straight wire, either solid or stranded and the outer conductor is typically a shield that might be braided or a foil. Coax cables exist because we can't run open-wire line near metallic objects (such as ducting) or bury it. We trade signal loss for convenience and flexibility.

Coax cable consists of an insulated center conductor which is covered with a shield. The signal is carried between the cable shield and the center conductor. This arrangement give quite good shielding agains noise from outside cable, keeps the signal well inside the cable and keeps cable characteristics stable.

The cable is designed to carry a high-frequency or broadband signal, as a high-frequency transmission line. Sometimes DC power (called bias) is added to the signal to supply the equipment at the other end, as in direct broadcast satellite receivers. Because the electromagnetic field carrying the signal exists (ideally) only in the space between the inner and outer conductors, it cannot interfere with or suffer interference from external electromagnetic fields.

Coax cables may be rigid or flexible. Rigid types have a solid sheath, while flexible types have a braided sheath, both usually of thin copper wire. The inner insulator, also called the dielectric, has a significant effect on the cable's properties, such as its characteristic impedance and its attenuation. The dielectric may be solid or perforated with air spaces. Connections to the ends of coax cables are usually made with RF converter.

Shireen Inc. has rolled out an optical repeater module designed for WCDMA networks. The RF module is used to monitor and control optical output power, LD bias current, received optical power, input and output RF signal power of Master, received FSK signal power and RF Gain control through the MCU. It is also used for RoHS compliant products.

The optical module for the repeater includes a linear analog PD with high sensitivity and a high power DFB laser, a low noise, linear RF amplifiers, as well as built-in Bi-Di components and FSK monitor. 9.6 and 19.2kbit/s data rates are provided for selection. In the slave, a laser with a wavelength of 1.5µm is selected as transmitter and an analog PD as optical signal receiver.

About Shireen Inc.

Shireen, Inc. designs, develops and manufactures components and systems for the Broadband Wireless, SCADA, Military and Telecommunications industries. Our solutions include everything from “mission critical” components for military communication systems to increasing the power of WiFi installations.

The optical module for the repeater includes a linear analog PD with high sensitivity and a high power DFB laser, a low noise, linear RF amplifier, as well as built-in Bi-Di components and FSK monitor. 9.6 and 19.2kbit/s data rates are provided for selection. In the slave, a laser with a wavelength of 1.5µm is selected as transmitter and an analog PD as optical signal receiver.

The optical module for the repeater includes a linear analog PD with high sensitivity and a high power DFB laser, a low noise, linear RF amplifier, as well as built-in Bi-Di components and FSK monitor. 9.6 and 19.2kbit/s data rates are provided for selection. In the slave, a laser with a wavelength of 1.5µm is selected as transmitter and an analog PD as optical signal receiver.

Efficiency and make of a RF amplifier determines the class it belongs to. Class E amplifiers are considered to be the best as they deliver significantly higher quality signals as compared to other class amplifiers. Transistor in Class E amplifiers works as a switch with a similar on/off function. Load network mechanism molds the current voltage and waveforms in a manner so as to avoid high voltage and current occurrences to limit power spread especially when the transistor switches on and off.

When the same transistor at the same frequency and output power is run in Class E, B and C amplifiers, Class E amplifier will operate more efficiently with power loss of less than 2.3 as compared to Class B and C amplifiers. They can be designed to handle frequency operations as large as 225-400 MHz during a fixed tune or narrow band operation. Class B and E amplifiers have same level of harmonic output. One big advantage of Class E amplifier is that they are “designable”, you can say customizable to make it simpler to understand. If you define the frequency variations and component effects in advance when designing Class E amplifiers then they will perform as expected.

To increase the efficiency of RF amplifiers it is important to reduce the power dissipation and still get the preset power output. Consider a RF amplifier and the greatest power dissipation in the entire system happens in the power transistor. Though the transistor has to be designed so as to be able to resist high power voltage and current, its power dissipation can be reduced by ensuring that both high voltage and current do not occur at the same point of time. If this can be attained through changes in the design then the efficiency of RF amplifiers can be increased substantially.

When “On” and the current is really high the transistor switch will work as a low resistance closed switch and the voltage will become zero. When “Off” and the voltage is high the transistor switch will work as an open switch and the current will become zero.

Similarly there are many different alternatives to increase the efficiency of Class E RF amplifier.

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.