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Hub AI
Frequency synthesizer AI simulator
(@Frequency synthesizer_simulator)
Hub AI
Frequency synthesizer AI simulator
(@Frequency synthesizer_simulator)
Frequency synthesizer
A frequency synthesizer is an electronic circuit that generates a range of frequencies from a single reference frequency. Frequency synthesizers are used in devices such as radio receivers, televisions, mobile telephones, radiotelephones, walkie-talkies, CB radios, cable television converter boxes, satellite receivers, and GPS systems. A frequency synthesizer may use the techniques of frequency multiplication, frequency division, direct digital synthesis, frequency mixing, and phase-locked loops to generate its frequencies. The stability and accuracy of the frequency synthesizer's output are related to the stability and accuracy of its reference frequency input. Consequently, synthesizers use stable and accurate reference frequencies, such as those provided by a crystal oscillator.
Three types of synthesizer can be distinguished. The first and second type are routinely found as stand-alone architecture: direct analog synthesis (also called a mix-filter-divide architecture as found in the 1960s e.g., HP 5100A and the more modern direct digital synthesizer (DDS) (table lookup). The third type are routinely used as communication system IC building blocks: indirect digital (PLL) synthesizers, including integer-N and fractional-N. The recently emerged TAF-DPS is also a direct approach. It directly constructs the waveform of each pulse in the clock pulse train.
A digiphase synthesizer is in some ways similar to a DDS, but it has architectural differences. One of its advantages is to allow a much finer resolution than other types of synthesizers with a given reference frequency.
Time-Average-Frequency Direct Period Synthesis (TAF-DPS) focuses on frequency generation for clock signals driving integrated circuits. Different from all other techniques, it uses a novel concept of time average frequency. Its aim is to address the two long-standing problems in the field of on-chip clock signal generation: arbitrary frequency generation and instantaneous frequency switching.
Starting from a base time unit, TAF-DPS first creates two types of cycles TA and TB. These two types of cycles are then used in an interleaved fashion to produce the clock pulse train. As a result, TAF-DPS can address the problems of arbitrary-frequency generation and instantaneous-frequency switching effectively. The first circuit technology utilizing the TAF concept was the flying-adder or flying-adder PLL, which was developed in late 1990s.[citation needed]
Prior to widespread use of synthesizers, in order to pick up stations on different frequencies, radio and television superheterodyne receivers relied on manual tuning of a local oscillator, which used a resonant circuit to produce the frequency. The receiver was adjusted to different frequencies by either a variable capacitor or a switch that chose the proper tuned circuit for the desired channel, such as with the turret tuner commonly used in television receivers prior to the 1980s. However, the resonant frequency of a tuned circuit is not very stable; variations in temperature and aging of components caused frequency drift and the receiver drifted off the station frequency. Automatic frequency control (AFC) solves some of the drift problem, but manual retuning was often necessary. Since transmitter frequencies are stabilized, an accurate source of fixed, stable frequencies in the receiver is desirable.
Quartz crystal resonators are many orders of magnitude more stable than LC circuits and, when used to control the frequency of the local oscillator, offer adequate stability to keep a receiver in tune. However, the resonant frequency of a crystal is determined by its dimensions and cannot be varied to tune the receiver to different frequencies. One solution is to employ many crystals, one for each frequency desired, and switch the correct one into the circuit. This technique is practical when only a handful of frequencies are required but quickly becomes costly and impractical in many applications. For example, the FM radio band in many countries supports 100 individual channel frequencies from about 88 to 108 MHz; the ability to tune in each channel would require 100 crystals. Cable television can support even more channels over a much wider band. A large number of crystals increases cost and requires additional space.
The solution to this was the development of circuits that could generate multiple frequencies from a reference frequency produced by a crystal oscillator. This is called a frequency synthesizer. The new synthesized frequencies have the same frequency stability of the master crystal oscillator since they are derived from it.
Frequency synthesizer
A frequency synthesizer is an electronic circuit that generates a range of frequencies from a single reference frequency. Frequency synthesizers are used in devices such as radio receivers, televisions, mobile telephones, radiotelephones, walkie-talkies, CB radios, cable television converter boxes, satellite receivers, and GPS systems. A frequency synthesizer may use the techniques of frequency multiplication, frequency division, direct digital synthesis, frequency mixing, and phase-locked loops to generate its frequencies. The stability and accuracy of the frequency synthesizer's output are related to the stability and accuracy of its reference frequency input. Consequently, synthesizers use stable and accurate reference frequencies, such as those provided by a crystal oscillator.
Three types of synthesizer can be distinguished. The first and second type are routinely found as stand-alone architecture: direct analog synthesis (also called a mix-filter-divide architecture as found in the 1960s e.g., HP 5100A and the more modern direct digital synthesizer (DDS) (table lookup). The third type are routinely used as communication system IC building blocks: indirect digital (PLL) synthesizers, including integer-N and fractional-N. The recently emerged TAF-DPS is also a direct approach. It directly constructs the waveform of each pulse in the clock pulse train.
A digiphase synthesizer is in some ways similar to a DDS, but it has architectural differences. One of its advantages is to allow a much finer resolution than other types of synthesizers with a given reference frequency.
Time-Average-Frequency Direct Period Synthesis (TAF-DPS) focuses on frequency generation for clock signals driving integrated circuits. Different from all other techniques, it uses a novel concept of time average frequency. Its aim is to address the two long-standing problems in the field of on-chip clock signal generation: arbitrary frequency generation and instantaneous frequency switching.
Starting from a base time unit, TAF-DPS first creates two types of cycles TA and TB. These two types of cycles are then used in an interleaved fashion to produce the clock pulse train. As a result, TAF-DPS can address the problems of arbitrary-frequency generation and instantaneous-frequency switching effectively. The first circuit technology utilizing the TAF concept was the flying-adder or flying-adder PLL, which was developed in late 1990s.[citation needed]
Prior to widespread use of synthesizers, in order to pick up stations on different frequencies, radio and television superheterodyne receivers relied on manual tuning of a local oscillator, which used a resonant circuit to produce the frequency. The receiver was adjusted to different frequencies by either a variable capacitor or a switch that chose the proper tuned circuit for the desired channel, such as with the turret tuner commonly used in television receivers prior to the 1980s. However, the resonant frequency of a tuned circuit is not very stable; variations in temperature and aging of components caused frequency drift and the receiver drifted off the station frequency. Automatic frequency control (AFC) solves some of the drift problem, but manual retuning was often necessary. Since transmitter frequencies are stabilized, an accurate source of fixed, stable frequencies in the receiver is desirable.
Quartz crystal resonators are many orders of magnitude more stable than LC circuits and, when used to control the frequency of the local oscillator, offer adequate stability to keep a receiver in tune. However, the resonant frequency of a crystal is determined by its dimensions and cannot be varied to tune the receiver to different frequencies. One solution is to employ many crystals, one for each frequency desired, and switch the correct one into the circuit. This technique is practical when only a handful of frequencies are required but quickly becomes costly and impractical in many applications. For example, the FM radio band in many countries supports 100 individual channel frequencies from about 88 to 108 MHz; the ability to tune in each channel would require 100 crystals. Cable television can support even more channels over a much wider band. A large number of crystals increases cost and requires additional space.
The solution to this was the development of circuits that could generate multiple frequencies from a reference frequency produced by a crystal oscillator. This is called a frequency synthesizer. The new synthesized frequencies have the same frequency stability of the master crystal oscillator since they are derived from it.