CN201854267U

CN201854267U - Local oscillation frequency synthesizer

Info

Publication number: CN201854267U
Application number: CN2010206201533U
Authority: CN
Inventors: 胡玉忠
Original assignee: JIANGSU RIGHT ELECTRONICS EQUIPMENT CO Ltd
Current assignee: JIANGSU RIGHT ELECTRONICS EQUIPMENT CO Ltd
Priority date: 2010-11-23
Filing date: 2010-11-23
Publication date: 2011-06-01
Anticipated expiration: 2020-11-23

Abstract

The utility model discloses a local oscillation frequency synthesizer. The circuit of the local oscillation frequency synthesizer comprises a U6 part, a U7 part and a phase locking part, wherein the U6 part takes 74HC4046 as the main body and generates VCO (voltage controlled oscillator), and the U7 part takes MC145151 as the main body and is mainly variable frequency division, phase discrimination and parametric frequency division. In the utility model, the integrated block MC 145151-2 and the integrated block 74HC4046 are adopted to form a simple circuit, the local oscillation frequency is synthesized by a digital phase-locked loop method, and then stable local oscillation signal required can be generated.

Description

A kind of local frequency synthesizer

Technical field

The utility model relates to frequency synthesizer, is specifically related to a kind of local frequency synthesizer.

Background technology

Local frequency is synthetic to be bonded into the frequency reducing of system division between being, is a kind of frequency synthesis mode that extensively adopts in mobile station.

The frequency synthesis theory begins to form about middle 1930s greatly, be to utilize the crystal oscillator of single or multiple different frequencies at that time as reference signal source, directly produce the output signal of many discrete frequencies through approach such as frequency multiplication, frequency division, mixing, the frequency synthesizer that Here it is uses the earliest is referred to as direct frequency synthesizer.Subsequently, phase feedback theory and Phase Lock Technique are applied to the frequency synthesis field, have produced indirect frequency synthesizer.So-called indirect type is meant that the output signal of synthesizer is not directly to get through conversion from reference source, but produces needed frequency output indirectly by the voltage controlled oscillator of phase-locked loop, so indirect frequency synthesizer is called frequency synthesizer of phase locking again.Because phase-locked loop has good narrow-band filtering characteristic, so its quality of output signals is significantly improved than direct synthesizer.The successful Application of Phase Lock Technique in frequency synthesis makes the frequency synthesizer technology obtain breakthrough.The spectral purity height of simple in structure, the output frequency composition of frequency synthesizer of phase locking, and be easy to obtain the very big concern that a large amount of advantages such as discrete frequency have caused people is for the extensive use of frequency synthesizer lays the foundation.In current FM broadcasting transmission technology, in order to adapt to strict demand to transmitter output frequency stability and frequency accuracy, and the needs that are convenient for changing transmitter frequency, generally used Phase Lock Technique and frequency synthesis technique in the solid state q-switched channel transmitter, phase-locked loop frequency synthesizer becomes the important part of solid state q-switched channel transmitter.

The advantage of phase-locked loop frequency synthesizer is that it can provide frequency stability very high output signal, can suppress parasitic component well, avoids using in a large number filter, thereby helps integrated and miniaturization.And the frequency dividing ratio of the program divider in the frequency synthesizer can use microcomputer to control, and is easy to realize the replacing of transmitter frequency and the program control and remote control that frequency shows thereof, promotes the digitlization of all solid state frequency modulated transmitter, integrated and system controlled by computerization.

Frequency synthesizer is the standard reference frequency with a high accuracy and high stability, through mixing, frequency multiplication and frequency division etc. to it add, subtract, the arithmetic of multiplication and division, finally produce a large amount of frequency sources with same accuracy and stability.Usually require the frequency of high accuracy and high stability in the modern electronic technology, generally all use crystal oscillator, but the frequency of crystal oscillator is single, can only in minimum scope, finely tune.Yet many radio communication equipments all require to provide a large amount of Frequency points in a very wide frequency range, the frequency synthesizer in the frequency modulation communication for example, and this just needs to adopt the horizontal one-tenth technology of frequency.

The method of frequency synthesizer mainly contains 3 kinds.Synthetic method the earliest is called as direct frequency synthesis, it is to utilize mixing, frequency multiplication, frequency division and band pass filter are finished the arithmetic to frequency, direct synthesizer can be realized the fast frequency conversion, comprise high frequency resolution arbitrarily, low phase noise and very high output frequency, but direct synthesizer uses much more hardware device than other two kinds of methods, thereby volume is big, the cost height, its another shortcoming is that useless parasitic frequency can appear in output, and this is because band pass filter can't totally cause the unwanted frequency filtering of frequency mixer.

What use was maximum at present is exactly the PLL frequency synthesizer.At some special occasions, for example require high operating frequency, very high frequency resolution or conversion performance etc. fast, the PLL frequency synthesizer is difficult to realize these performances, can adopt two kinds of synthetic methods, also these 3 kinds of synthetic methods can be used in combination, constitute hybrid-type frequency synthesizer.

Summary of the invention

The purpose of this utility model is: a kind of local frequency synthesizer is provided, and this synthesizer adopts the synthetic local frequency of DPLL digital phase-locked loop method, and circuit is simple, produces stable required local oscillation signal.

Technical solution of the present utility model is: the circuit of this synthesizer comprises U6 part and U7 part, and the U6 part produces VCO mainly based on 74HC4046, phase-locked part, and U7 is partly mainly based on MC145151, is variable division, phase demodulation, with reference to frequency division; Physical circuit connects as follows:

U6 part (74HC4046):74HC4046 the 4th pin links to each other with the pin of VR14 and the pin of C80, other two terminal shortcircuits of face VR14, directly export stable local oscillation signal, the other end of C80 electric capacity is connected on the 1st pin of MC14515, and the 7th pin of 74HC4046 connects a pin of C79 electric capacity, and an other pin of C79 electric capacity connects the 6th pin of 74HC4046, the direct ground connection of the 5th pin of 74HC4046, the 9th pin of 74HC4046 connects a pin of C88 electric capacity, and links to each other with the 4th pin of MC14515, and capacitor C 88 another pin link to each other with the pin of VR20, and link to each other with a pin of capacitor C 87, the VR20 centre cap links to each other with another pin short circuit and with ground, and the other pin of C87 links to each other with ground, and 11 pin of 74HC4046 link to each other with the pin of potentiometer VR20, the centre cap of VR20 links to each other with the other end and connects, the 1st pin of 74HC4046, the 2nd pin, the 3rd pin, the 10th pin, the 13rd pin, the 14th pin, the 15th pin is all unsettled;

U7 part (MC145151-2):MC145151-2 the 1st pin and C80 join, the 4th pin of MC145151-2 is connected with C88, the direct ground connection of the 6th pin of MC145151-2, MC145151-2 the 26th pin is connected with the pin of crystal oscillator X4 and is connected with a pin of capacitor C 78, another pin of crystal oscillator X4 is connected with the 27th pin of MC145151-2, MC145151-2 the 27th pin is connected with the pin of tunable capacitor CT5, another pin of tunable capacitor CT5 links to each other with another pin of capacitor C 78, the 11st pin of MC145151-2 is connected with the 1st pin of toggle switch S10, the 12nd pin of MC145151-2 is connected with the 2nd pin of toggle switch S10, the 13rd pin of MC145151-2 is connected with the 3rd pin of toggle switch S10, the 14th pin of MC145151-2 is connected with the 4th pin of toggle switch S10, the 15th pin of MC145151-2 is connected with the 5th pin of toggle switch S10, the 16th pin of MC145151-2 is connected with the 6th pin of toggle switch S10, the 17th pin of MC145151-2 is connected with the 7th pin of toggle switch S10, the 18th pin of MC145151-2 is connected with the 8th pin of toggle switch S10, the 9th pin of S10, the 10th pin, the 11st pin, the 12nd pin, the 13rd pin, the 14th pin, the 15th pin, the 16th pin is connected to each other and is connected with ground, the 19th pin of MC145151-2 is connected with the 1st pin of toggle switch S11, the 20th pin of MC145151-2 is connected with the 2nd pin of toggle switch S11, the 24th pin of MC145151-2 is connected with the 3rd pin of toggle switch S11, the 25th pin of MC145151-2 is connected with the 4th pin of toggle switch S11, the 22nd pin of MC145151-2 is connected with the 5th pin of toggle switch S11, the 23rd pin of MC145151-2 is connected with the 6th pin of toggle switch S11, the 9th pin of S11, the 10th pin, the 11st pin, the 12nd pin, the 13rd pin, the 14th pin, the 15th pin, the 16th pin is connected to each other and links to each other with ground, the 5th pin of MC145151-2, the 6th pin, the 7th pin, the 8th pin, the 9th pin, the 10th pin, the 28th pin is all unsettled.

In this utility model circuit, the frequency of sending in the phase discriminator is 5kHz, and it carries out 2048 frequency divisions by MC145151-2 to outside 10.240MHz crystal oscillator and obtains, and synthetic 16.455MHz local frequency then N should get 3291; Variable division, phase demodulation, all be integrated in the MC145151-2 the inside with reference to frequency division, VCO is on 74HC4046, stir S10, S11 toggle switch everybody can change frequency dividing ratio, frequency dividing ratio N is shown by 14 2 system numerical tables, ' 1 ' of S10 is a lowest order, ' 6 ' of S11 is a highest order, 14 bits of N=3291 correspondence are 00110011011011, the output frequency of VCO equals N and multiply by 5kHz, stir toggle switch everybody just changed frequency dividing ratio N, also just changed the local frequency of VCO output; VR18 has determined the highest output frequency of VCO, make the VCO output frequency can reach 16.455MHz, and VR18 should be enough little, that is to say that N reserves after, regulate VR18 clockwise and can heighten output frequency; VR20 is the crucial resistance of phase-shift network, and when the local oscillator waveform of VCO output was unintelligible, the big I of regulating the VR20 resistance made waveform clear and do not have overlapping and shake; VR21 is the local oscillator voltage swing that control VCO outputs to next stage, regulates VR21 counterclockwise and can reduce to export local oscillator voltage, thereby produce a stable local oscillation signal.

The utlity model has following advantage: 1, with the standard reference frequency of a high accuracy and high stability, through mixing, frequency multiplication and frequency division etc. to it add, subtract, the arithmetic of multiplication and division, produce a large amount of frequency sources with same accuracy and stability, the Applied Digital logical circuit is reduced to VCO frequency one or many on the phase discriminator frequency, compare in phase discriminator with reference frequency again, the error signal that is produced is used for controlling the frequency of VCO, make it to fix on the stability of reference frequency, produce stable local oscillation signal; 2, adopt integrated package MC145151-2 and integrated package 74HC4046 to form easy circuit,, produce stable required local oscillation signal by the synthetic local frequency of DPLL digital phase-locked loop method.

Description of drawings

Fig. 1 is circuit theory diagrams of the present utility model.

Embodiment

Further specify technical solution of the present utility model below in conjunction with accompanying drawing.

As shown in Figure 1, the circuit of this synthesizer comprises U6 part and U7 part, and the U6 part produces VCO mainly based on 74HC4046, phase-locked part, and U7 is partly mainly based on MC145151, is variable division, phase demodulation, with reference to frequency division; Physical circuit connects as follows:

Claims

1. local frequency synthesizer is characterized in that: the circuit of this synthesizer comprises U6 part and U7 part, and U6 is partly mainly based on 74HC4046, produce VCO, phase-locked part, U7 part be mainly based on MC145151, mainly is variable division, phase demodulation, with reference to frequency division; Physical circuit connects as follows: