Antenna
Switches are used in Mobile Phones extensively at the very first stage of the point of entry of the signal (called the received signal Rx)into the mobile phone which also eventually becomes the point of exit for the outgoing signal or the transmitted signal Tx.
ANTENNA SWITCH ….. FILTERS ….WHAT ARE THEY?
ANTENNA SWITCHES OR DIPLEXERS ARE DEVICES WHICH transmit and receive on the same antenna at the same time, reject unwanted signals and feed two different signals to the same antenna.
(ANTENNA SWITCH IS ALSO KNOWN AS A DIPLEXER ! )
The common application for a diplexer is to connect a dual band mobile radio's two antenna connections to a common feed line and antenna. A diplexer is a simple high and low pass filter connected together. The filters are explained in detail below.
Diplexers are three-terminal frequency-dependent devices that can be used as a separator or a combiner of signals. It can have more than three terminals also. The device consists of two fixed tuned bandpass filters sharing a common port. The common port and the output of the two filters (RX and TX) form the three terminals of the diplexer. Signals applied to common port are separated in accordance with their passband frequencies of the filters. Signals applied to either uncommon port are isolated from the other uncommon port and are combined at the common port.
Picture of a DIPLEXER
If u can't find the PICTURE HERE, please download the attached file for viewing it. As is common knowledge, a FILTER is a device which removes unwanted items from a mix and provides us with a finished product which is a pure final product of our requirement.
Electronic filters are electronic circuits which carry out the signal processing functions, specifically intended to enhance wanted signal components and/or remove unwanted ones.
SAW (surface acoustic wave) filters are electromechanical devices commonly used in radio frequency applications. Electrical signals are converted to a mechanical wave in a piezoelectric crystal; this wave is delayed as it propagates across the crystal, before being converted back to an electrical signal by further electrodes. The delayed outputs are recombined to produce a direct analog implementation of a finite impulse response filter. This hybrid filtering technique is also found in an analog sampled filter.
Passive filters :The simplest electronic linear filters are based on combinations of resistors, inductors and capacitors. These filters exist in so-called RC,LC,RL, and RLC varieties. All these types are collectively known as passive filters, because they do not depend upon an external power supply. Inductors block high-frequency signals and conduct low-frequency signals, while capacitors do the reverse. A filter in which the signal passes through an inductor, or in which a capacitor provides a path to earth, therefore presents less attenuation to low-frequency signals than high-frequency signals and is a low-pass filter.
Switches are used in Mobile Phones extensively at the very first stage of the point of entry of the signal (called the received signal Rx)into the mobile phone which also eventually becomes the point of exit for the outgoing signal or the transmitted signal Tx.
ANTENNA SWITCH ….. FILTERS ….WHAT ARE THEY?
ANTENNA SWITCHES OR DIPLEXERS ARE DEVICES WHICH transmit and receive on the same antenna at the same time, reject unwanted signals and feed two different signals to the same antenna.
(ANTENNA SWITCH IS ALSO KNOWN AS A DIPLEXER ! )
The common application for a diplexer is to connect a dual band mobile radio's two antenna connections to a common feed line and antenna. A diplexer is a simple high and low pass filter connected together. The filters are explained in detail below.
Diplexers are three-terminal frequency-dependent devices that can be used as a separator or a combiner of signals. It can have more than three terminals also. The device consists of two fixed tuned bandpass filters sharing a common port. The common port and the output of the two filters (RX and TX) form the three terminals of the diplexer. Signals applied to common port are separated in accordance with their passband frequencies of the filters. Signals applied to either uncommon port are isolated from the other uncommon port and are combined at the common port.
Picture of a DIPLEXER
If u can't find the PICTURE HERE, please download the attached file for viewing it. As is common knowledge, a FILTER is a device which removes unwanted items from a mix and provides us with a finished product which is a pure final product of our requirement.
Electronic filters are electronic circuits which carry out the signal processing functions, specifically intended to enhance wanted signal components and/or remove unwanted ones.
SAW (surface acoustic wave) filters are electromechanical devices commonly used in radio frequency applications. Electrical signals are converted to a mechanical wave in a piezoelectric crystal; this wave is delayed as it propagates across the crystal, before being converted back to an electrical signal by further electrodes. The delayed outputs are recombined to produce a direct analog implementation of a finite impulse response filter. This hybrid filtering technique is also found in an analog sampled filter.
Passive filters :The simplest electronic linear filters are based on combinations of resistors, inductors and capacitors. These filters exist in so-called RC,LC,RL, and RLC varieties. All these types are collectively known as passive filters, because they do not depend upon an external power supply. Inductors block high-frequency signals and conduct low-frequency signals, while capacitors do the reverse. A filter in which the signal passes through an inductor, or in which a capacitor provides a path to earth, therefore presents less attenuation to low-frequency signals than high-frequency signals and is a low-pass filter.
If the signal passes through a capacitor, or has a path to ground through an inductor, then the filter presents less attenuation to high-frequency signals than low-frequency signals and is a high-pass filter. Resistors on their own have no frequency-selective properties, but are added to inductors and capacitors to determine the time-constants of the circuit, and therefore the frequencies to which it responds.
At very high frequencies (above about 100 megahertz or megacycles.), sometimes the inductors consist of single loops or strips of sheet metal, and the capacitors consist of adjacent strips of metal.
These are called stubs.
Active filters: Active filters are made up by using a combination of passive and active (amplifying) components. Amplifiers are frequently used in active filter designs. These can have high selectivity, and achieve the desired selectivity without the use of inductors. However, their upper frequency limit is limited by the bandwidth of the amplifiers used. Generally, each family of filters can be assigned a particular order. The higher the order, the more the filter will approach the "perfect" filter of complete transmission in the pass band, and complete attenuation in the stop band. Each family can be used to specify a particular pass band in which frequencies are transmitted, while frequencies outside the pass band are more or less attenuated.
• Low-pass filter - Low frequencies are passed, high frequencies are attenuated.
• High-pass filter - High frequencies are passed, Low frequencies are attenuated.
• Band-pass filter- Only frequencies in a frequency band are passed.
• Band-stop filter - Only frequencies in a frequency band are attenuated.
• All-pass filter - All frequencies are passed, but the phase of the output is modified.
•An analogue filter handles analogue signals or continuous-time signals,
Active filters: Active filters are made up by using a combination of passive and active (amplifying) components. Amplifiers are frequently used in active filter designs. These can have high selectivity, and achieve the desired selectivity without the use of inductors. However, their upper frequency limit is limited by the bandwidth of the amplifiers used. Generally, each family of filters can be assigned a particular order. The higher the order, the more the filter will approach the "perfect" filter of complete transmission in the pass band, and complete attenuation in the stop band. Each family can be used to specify a particular pass band in which frequencies are transmitted, while frequencies outside the pass band are more or less attenuated.
• Low-pass filter - Low frequencies are passed, high frequencies are attenuated.
• High-pass filter - High frequencies are passed, Low frequencies are attenuated.
• Band-pass filter- Only frequencies in a frequency band are passed.
• Band-stop filter - Only frequencies in a frequency band are attenuated.
• All-pass filter - All frequencies are passed, but the phase of the output is modified.
•An analogue filter handles analogue signals or continuous-time signals,
whether electric potential, sound waves, or mechanical motion directly. This is opposed to a digital filter that operates on discrete-time signals. Older analog filters (newer filters are digital filters) work
entirely in the analog realm and must rely on physical networks of electronic components (such as resistors, capacitors, transistors, etc.) to achieve a desired filtering effect.
entirely in the analog realm and must rely on physical networks of electronic components (such as resistors, capacitors, transistors, etc.) to achieve a desired filtering effect.
Passive filter: A
passive component is an electronic component that does not require a source of energy to perform its intended function. Examples of passive components include resistors, capacitors, and inductors. A passive filter is an electronic filter made entirely from passive components.
passive component is an electronic component that does not require a source of energy to perform its intended function. Examples of passive components include resistors, capacitors, and inductors. A passive filter is an electronic filter made entirely from passive components.
Activefilter:
An Active filter is the one which involves active component that make use of a semi-conductor device like a transistor, an electronic device that requires a source of energy to perform its
intended function. A active component is one that can be used to provide gain or an amolification of the signal in an electronic circuit. It contains mainly semiconductor devices like diodes and
transistors.
Digital filter :
intended function. A active component is one that can be used to provide gain or an amolification of the signal in an electronic circuit. It contains mainly semiconductor devices like diodes and
transistors.
Digital filter :
A digital filter is any electronic filter that works by performing digital math operations on an
intermediate form of a signal. Digital filters can easily achieve performance metrics far beyond what is (even theoretically) possible with analog filters. It is not particularly difficult, for example, to create a 1000Hz low-pass filter which can achieve near-perfect transmission of a 999Hz input while entirely blocking a 1001Hz signal.
Analog filters cannot split apart such closely spaced signals.
Also, for complex multi-stage filtering operations, digital filters have the potential to attain much better signal to noise ratios (more of desired signal in comparision to unwanted signals) than analog filters. This is because whereas at each intermediate stage the analog filter adds more noise to the signal, the digital filter performs noiseless math operations at each intermediate step in the transform.
intermediate form of a signal. Digital filters can easily achieve performance metrics far beyond what is (even theoretically) possible with analog filters. It is not particularly difficult, for example, to create a 1000Hz low-pass filter which can achieve near-perfect transmission of a 999Hz input while entirely blocking a 1001Hz signal.
Analog filters cannot split apart such closely spaced signals.
Also, for complex multi-stage filtering operations, digital filters have the potential to attain much better signal to noise ratios (more of desired signal in comparision to unwanted signals) than analog filters. This is because whereas at each intermediate stage the analog filter adds more noise to the signal, the digital filter performs noiseless math operations at each intermediate step in the transform.
The primary source of noise in a digital filter is found in the initial analog to digital conversion step, where in addition to any circuit noise introduced, the signal is subject to an unavoidable selectivity error due to the finite resolution of the digital representation of the signal.
Digital filters can achieve virtually any filtering effect that can be expressed as a mathematical algorithm. The two primary limitations of digital filters are their speed (the filter can't operate any faster than the computer at the heart of the filter), and their cost. However as the cost of integrated circuits have continued to drop over time, digital filters have become increasingly commonplace and are now an essential element of many everyday objects such as radios, cellphones, and stereo receivers. Digital filters can easily achieve performance levels far more than what is (even theoretically) possible with analog filters. It is not particularly difficult, for example, to create a 1KHz low-pass filter which can achieve near-perfect transmission of a 0.999KHz input while entirely blocking a 1.001KHz signal. Analog filters cannot split apart such closely spaced signals.
Mobile Phones make use of Filters called Dual Band-pass filters because they need to allow two frequencies of signals most commonly 900MHz and 1800MHz in the dual band mobile phones. Also Antenna Switches are used in Mobile Phones expensively at the very first stage of the point of entry of the signal (called the received signal Rx) into the mobile phone which also eventually becomes the point of exit for the outgoing signal or the transmitted signal Tx. The newer models of the Mobile Phones like a Nokia 6600 makes use of an active Antenna Switch which also has a built-in amplifier circuit inside it to immediately boost the Rx signal.
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