CN215990763U

CN215990763U - Device for improving stability of two local oscillator frequencies

Info

Publication number: CN215990763U
Application number: CN202122262787.7U
Authority: CN
Inventors: 李安涛; 李健光
Original assignee: Shenzhen Pufang Technology Co ltd
Current assignee: Shenzhen Pufang Technology Co ltd
Priority date: 2021-09-17
Filing date: 2021-09-17
Publication date: 2022-03-08
Anticipated expiration: 2031-09-17

Abstract

The utility model provides a device for improving the stability of a two-local-oscillator frequency, which comprises a temperature compensation frequency reference source, a frequency multiplier, a frequency selection network, a second frequency mixer and two intermediate-frequency filters, wherein the temperature compensation frequency reference source, the frequency multiplier, the frequency selection network, the second frequency mixer and the two intermediate-frequency filters are sequentially connected. In this application, set up the frequency multiplier and cooperate with the frequency selection network and obtain two local oscillators, two local oscillators obtain two intermediate frequency signals with an intermediate frequency mixing, be ceramic filter (only this two kinds of frequencies of 455KHz and 450KHz on the market) to the device of two intermediate frequency filtering, just also need not specially go to customize, solved the source problem of this device, improved the frequency stability of two local oscillators simultaneously again.

Description

Device for improving stability of two local oscillator frequencies

Technical Field

The utility model relates to a device for improving the stability of a two-local-oscillator frequency.

Background

A receiving channel of a data transmission radio station generally adopts superheterodyne receiving of twice frequency conversion, signals related in the receiving channel comprise input signals, a local oscillator, an intermediate frequency, a second local oscillator and a second intermediate frequency, the five signals respectively correspond to five frequencies, and deviation of each frequency affects performance of a receiver; the frequency deviation of the input signal is determined by the frequency deviation of the opposite transmitting terminal; the frequency deviation of the local oscillator signal depends on the frequency deviation of the local device. The superheterodyne receiver is subjected to frequency conversion twice, and any frequency conversion with frequency deviation can cause the increase of the receiving error rate.

The frequency deviation includes frequency deviation at normal temperature and frequency drift under temperature change. The frequency deviation at normal temperature is adjusted to be within the allowable deviation range before the device is shipped, and the frequency drift caused by temperature change needs to be compensated by taking measures.

The device for generating a local oscillator generally adopts a temperature compensated crystal oscillator as a frequency reference source, and the frequency stability of the device is 1-2ppm and is relatively high. The device for generating two local oscillators usually adopts a common crystal, the frequency stability of the crystal is only 30-50ppm, and the stability of the crystal is dozens of times different from the temperature compensation frequency source of one local oscillator. The lower the stability of the two local oscillators is, the greater the deviation of the received frequency along with the temperature change is, and the more serious the receiving performance is reduced due to the influence on the signal reception.

SUMMERY OF THE UTILITY MODEL

In view of the shortcomings in the prior art, the present invention provides a device for improving the stability of two local oscillator frequencies, so as to solve the problems in the background art.

In order to achieve the purpose, the utility model is realized by the following technical scheme:

a device for improving the stability of a second local oscillator frequency comprises a temperature compensation frequency reference source, a frequency multiplier, a frequency selection network, a second frequency mixer and a second intermediate frequency filter, wherein the temperature compensation frequency reference source, the frequency multiplier, the frequency selection network, the second frequency mixer and the second intermediate frequency filter are sequentially connected through a circuit.

The device for improving the stability of the two local oscillation frequencies further comprises a frequency synthesizer, a first frequency mixer and an intermediate frequency filter, wherein the temperature compensation frequency reference source is connected with the frequency synthesizer, and the frequency synthesizer, the first frequency mixer and the intermediate frequency filter are sequentially connected.

A frequency selective network is a device that passes signals at a particular frequency, producing sufficient attenuation for the remaining frequencies.

The frequency selection network consists of a resonant loop and has the function of selecting a signal of a certain frequency component as required and filtering other frequency components.

The frequency selective network may be a low pass filter or a band pass filter.

When a signal of a certain frequency passes through the semiconductor device, fundamental waves, second harmonics and higher harmonics are generated, and the frequency selection network can allow a required frequency component to pass through as required while preventing other frequency components from passing through. The fundamental wave is selected to form an amplifier, the second harmonic is selected to form a frequency doubler, and the third harmonic is selected to form a frequency tripler.

The working process is as follows:

and generating a local oscillator through frequency synthesis on the basis of the temperature compensation frequency reference source. The received high-frequency signal and a local oscillator signal are mixed by a first mixer to obtain an intermediate-frequency signal with fixed frequency, and the intermediate-frequency signal is filtered by an intermediate-frequency filter.

Taking a certain frequency multiplication of a frequency reference source of a local oscillator as the frequency of a second local oscillator: the frequency reference source of a local oscillator generates second harmonic and higher harmonic through a frequency multiplier formed by a nonlinear device, one of the higher harmonic is selected through a frequency selection network to serve as a second local oscillator signal, the first intermediate frequency signal and the second local oscillator signal are mixed through a second frequency mixer to obtain a second intermediate frequency signal, the second intermediate frequency signal is filtered through a second intermediate frequency filter, and then frequency discrimination is carried out to obtain a baseband signal.

Advantageous effects

The frequency multiplier is arranged to be matched with the frequency selection network to obtain two local oscillators, the two local oscillators and an intermediate frequency are mixed to obtain two intermediate frequency signals, the device aiming at the two intermediate frequency filtering is a ceramic filter (only two frequencies of 455KHz and 450KHz are available on the market), the device is not specially customized, the source problem of the device is solved, and the frequency stability of the two local oscillators is improved.

Drawings

Other features, objects and advantages of the utility model will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:

FIG. 1 is a schematic structural diagram of the present invention.

Fig. 2 is a diagram showing a structure implementation method of the present invention.

Detailed Description

In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the utility model easy to understand, the utility model is further described with the specific embodiments.

Referring to fig. 1-2, the present invention provides a technical solution: a device for improving the stability of two local oscillation frequencies comprises a temperature compensation frequency reference source 1, a frequency multiplier 2, a frequency selection network 3, a second frequency mixer 4 and two intermediate frequency filters 5, wherein the temperature compensation frequency reference source, the frequency multiplier, the frequency selection network, the second frequency mixer and the two intermediate frequency filters are sequentially connected.

The frequency selective network may be a low pass filter or a band pass filter.

The working process is as follows:

Taking a certain frequency multiplication of a frequency reference source of a local oscillator as the frequency of a second local oscillator: the frequency reference source of a local oscillator generates second and higher harmonics through a frequency multiplier formed by a nonlinear device, one of the higher harmonics is selected through a frequency selection network to serve as a second local oscillator signal, the first intermediate frequency signal and the second local oscillator signal are mixed through a second frequency mixer to obtain a second intermediate frequency signal, the second intermediate frequency signal is filtered through a second intermediate frequency filter, and a baseband signal is obtained through frequency discrimination

In the embodiment, the frequency reference source of a local oscillator is multiplied by three, and the frequency reference source is amplified and then used as a second local oscillator. For example, a local oscillator frequency reference source is 12.8MHz, its frequency tripled is 38.4MHz, and the frequency of an intermediate frequency is designed to be 37.95MHz, so that after the second frequency conversion, a 450KHz second intermediate frequency signal is obtained, which is exactly one of the two commonly used second intermediate frequencies (the two intermediate frequency filters on the market have only two frequencies, 455KHz and 450 KHz).

While there have been shown and described what are at present considered the fundamental principles of the utility model, its essential features and advantages, it will be apparent to those skilled in the art that the utility model is not limited to the details of the foregoing exemplary embodiments, but is capable of other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the utility model being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.

Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.

Claims

1. The utility model provides an improve two local oscillator frequency stability's device which characterized in that: the temperature compensation frequency reference source, the frequency multiplier, the frequency selection network, the second frequency mixer and the two intermediate frequency filters are connected in sequence.

2. The apparatus according to claim 1, wherein the apparatus for improving the stability of the second local oscillator frequency is characterized in that: the device for improving the stability of the two local oscillation frequencies further comprises a frequency synthesizer, a first frequency mixer and an intermediate frequency filter, wherein the temperature compensation frequency reference source is connected with the frequency synthesizer, and the frequency synthesizer, the first frequency mixer and the intermediate frequency filter are sequentially connected.

3. The apparatus according to claim 1, wherein the apparatus for improving the stability of the second local oscillator frequency is characterized in that: a frequency selective network is a device that passes signals at a particular frequency, producing sufficient attenuation for the remaining frequencies.

4. The apparatus according to claim 1, wherein the apparatus for improving the stability of the second local oscillator frequency is characterized in that: the frequency selection network consists of a resonant loop and has the function of selecting a signal of a certain frequency component as required and filtering other frequency components.

5. The apparatus according to claim 1, wherein the apparatus for improving the stability of the second local oscillator frequency is characterized in that: the frequency selective network may be a low pass filter or a band pass filter.