DD274314A1 - METHOD AND CIRCUIT FOR THE QUICK FREQUENCY CHANGE OF A PHASE CONTROLLED OSCILLATOR - Google Patents

Abstract

The field of application of the invention are synthesizers for transmitters and receivers of telecommunications and high-frequency generators. The inventive method, the time for the coarse tuning of the oscillator is to be shortened. The value of the coarse tuning, which is generated automatically, is digitally stored for the necessary frequencies, and with rapid frequency change, the memory contents are given to a digital-to-analogue converter, which provides the coarse tuning for the oscillator. figure

Description

in the case of frequency inequality, the up-down counter 6 switches until the voltage converted in the digital-analog converter 7 has tuned the oscillator 1 to the desired frequency f ₀ = η · f. Depending on the size of the frequency step, a certain amount of time is required for this automatic tuning. In order to reduce this tuning time to a minimum, according to the invention the bit word of the up-down counter 6 is loaded into the memory 9. Upon re-selection of this frequency, the control logic 10 causes the memory contents of the memory 9 is switched via the switch 8 immediately to the inputs of the 'Jigital-analog converter 7 and the coarse tuning voltage is available for the oscillator 1 in a very short time. A program can be used to store the data and necessary frequencies.

Claims (2)

A method for fast frequency change of a phase-locked oscillator, which is controlled by a coarse and fine tuning voltage, wherein the coarse tuning voltage is supplied as a digital value via a digital-to-analog converter to the oscillator, characterized in that the value of the coarse tuning for the necessary frequencies is written in a digital memory (9) and with fast frequency change of the memory contents to the digital-to-analog converter (7) is performed. 2. Circuit for fast frequency change of a phase-controlled oscillator consists of a phase-locked loop and a frequency discriminator provides the value of the coarse tuning digital supplies and via a digital-to-analog converter to the oscillator, characterized in that when writing the value of the coarse tuning voltage control logic ( 10) connects a forward and backward counter (6) via a switch (8) with the digital-to-analog converter (7) and a memory (9) and the control logic (10) the fast forward frequency change the up-down counter (6) disconnects the switch (8). For this 1 page drawing Field of application of the invention The field of application of the invention are synthesizers for transmitters and receivers of telecommunications and high-frequency generators. Characteristic of the known state of the art Phase-controlled oscillators with a large frequency range require, in addition to the phase-dependent control voltage, a coarse tuning of the frequency. Such a coarse tuning is possible by switching reactances or by using voltage-dependent reactances, for example capacitance diodes, to which a corresponding DC voltage is supplied. This DC voltage can be automatically generated in a frequency discriminator that changes the DC voltage according to the difference of the two frequencies to be compared. At Frequenzgleichhcit the DC voltage has reached a certain value, which is then maintained. When changing the frequency, the DC voltage must be changed according to the Af. This requires a certain amount of time, which is too high for some applications. The tuning time can be shortened by using a tunable, switchable voltage divider for each frequency to be set. The disadvantage is the high effort, precise adjustment, temperature instability, aging and low reliability. Object of the invention The aim of the invention is to provide a method and a circuit for carrying out the method, which makes it possible to quickly and reliably make a frequency change in transmitters and receivers of telecommunications. Explanation of the essence of the invention The invention has for its object to provide a method and a circuit for carrying out the method, which makes it possible to shorten the time for the coarse tuning of the oscillator. The object is achieved in that contains in a phase locked loop, the phase and frequency comparison, the frequency comparison is designed so that a bit-word is formed, which via a digital-to-analog converter (DAC) the necessary coarse tuning voltage for the oscillator, : fert. In the control state, the input frequencies at the frequency discriminator are equal, and the bit word corresponding to the automatically tuned frequency is loaded in a memory (RAM). A program can successively store all the bit-words for the necessary frequencies. With fast frequency changes, the memory is fetched and switched to the DAC, so that the time for the automatic adjustment is eliminated. embodiment The invention will be explained in more detail below with reference to an embodiment. In the accompanying drawing, the solution according to the invention is shown. The frequency f _{0 of} the oscillator 1 is divided by the frequency divider 2 by η and fed to the phase discriminator 3. In addition, the phase discriminator 3 receives the reference frequency f ,. The phase-dependent voltage is supplied to the oscillator 1 via the Regeltiefpaß 1. Parallel to the phase discriminator of the frequency comparator 5 is connected, the