CN111224907A

CN111224907A - Large-bandwidth broadband variable frequency link amplitude equalization method

Info

Publication number: CN111224907A
Application number: CN201911146578.7A
Authority: CN
Inventors: 高朋; 张枢; 张博; 仇成强; 徐从玉; 张柯
Original assignee: China Electronics Technology Instruments Co Ltd CETI
Current assignee: China Electronics Technology Instruments Co Ltd CETI
Priority date: 2019-11-21
Filing date: 2019-11-21
Publication date: 2020-06-02

Abstract

The invention belongs to the technical field of electric communication, and relates to an amplitude equalization method of a frequency conversion link, in particular to an amplitude equalization method of a large-bandwidth broadband frequency conversion link.

Description

Large-bandwidth broadband variable frequency link amplitude equalization method

Technical Field

The invention belongs to the technical field of electric communication, and relates to an amplitude equalization method of a variable frequency link.

Background

With the rapid development of modern scientific and technical information technology, the data transmission amount is increased rapidly, the contradiction between the data amount and the transmission capacity is increasingly prominent, the signal bandwidth is increased continuously, the transmission frequency is increased continuously, higher technical requirements are provided for information transmission links, test equipment and the like, and up-down frequency conversion devices with large bandwidth and wide frequency band are produced. The large-bandwidth broadband up-down conversion device is used for realizing low-distortion conversion between broadband microwave millimeter wave signals and large-bandwidth intermediate frequency signals, and is widely applied to the fields of broadband high-speed satellite communication, electromagnetic spectrum signal monitoring, electronic countermeasure, inter-satellite communication simulation test and the like. In order to meet the requirements of indexes such as frequency conversion gain, image frequency rejection, in-band spurious emission and the like, the up-down frequency conversion device usually adopts a mode of multiple frequency conversion and multi-stage amplification, which needs devices such as a multi-stage mixer, an amplifier, a filter and the like, and after the multi-stage devices are cascaded, the gain flatness of the whole frequency conversion link is inevitably rapidly deteriorated.

The flatness in the up-down frequency conversion device usually comprises flatness in a frequency band (radio frequency band) and flatness in a channel (modulation signal), wherein the flatness in the frequency band can be calibrated through a variable attenuator or a variable gain amplifier, and the flatness in the channel is usually realized only by selecting preferred devices and increasing attenuators to improve link matching, so that the requirement on the indexes of the amplitude flatness of the devices is high, and the limitation is large. However, with the development of large bandwidth and wide frequency band, it is difficult to satisfy the requirements of large signal bandwidth and wide frequency band.

Disclosure of Invention

The invention aims to improve the flatness index in the channel of an up-down frequency conversion device so as to meet the frequency conversion requirement of a large-bandwidth signal in a wide frequency band range.

The technical scheme adopted by the invention for realizing the purpose is as follows: a large-bandwidth broadband variable frequency link amplitude equalization method comprises the following steps: selecting a horizontal curve path of the amplitude equalizer through a switch, and testing to obtain a radio frequency response curve of the whole variable frequency link;

finding out a frequency band which does not meet the index requirement in any △ f bandwidth in the radio frequency response curve;

aiming at the frequency band of which the frequency response curve does not meet the index requirement, a compensation circuit is connected to the intermediate frequency end;

and a path in the amplitude equalizer is selected through the switch to be communicated with the compensation circuit, and a corresponding compensation curve is selected to carry out amplitude equalization.

As a further improvement of the invention, the compensation circuit is formed by adding attenuators to the multi-stage parallel RLC resonant branches.

As a further improvement of the invention, the RLC resonant branch is a series resonant circuit formed by R, L, C or a resonant circuit formed by L, C connected in parallel and then connected in series with R.

As a further improvement of the invention, the attenuator is pi-shaped, T-shaped or bridge T-shaped.

As a further improvement of the present invention, the compensation curve is a curve opposite to the frequency response curve.

As a further improvement of the present invention, the compensation curve comprises 5 expressions of positive slope, negative slope, horizontal curve, upper parabola and lower parabola and any combination thereof.

As a further improvement of the present invention, the intermediate frequency end is a frequency low end of the frequency conversion link.

As a further improvement of the invention, the intermediate frequency end comprises an input or output intermediate frequency end, or a first intermediate frequency and a second intermediate frequency.

The amplitude equalization method of the down-conversion device on the large-bandwidth broadband is used for pre-compensating at the intermediate frequency end. The method is designed according to the frequency response curve of the whole variable frequency link, and the switch is adopted to select the equalizing circuit at the intermediate frequency end for amplitude equalization, so that the flatness in a channel can be effectively improved. The method is suitable for the working frequency bandwidth, and can realize the ultra-wideband frequency coverage from the radio frequency to the millimeter wave frequency; the design of the equalizing circuit is simple, easy to realize, easy to adjust, strong in expansibility and low in cost.

Drawings

FIG. 1 is a schematic diagram of a frequency response curve;

FIG. 2 is a schematic illustration of an equalization curve employed in the method of the present invention;

FIG. 3 is a schematic diagram of an equalization circuit according to one embodiment of the present invention;

FIG. 4 is a schematic block diagram of a method of amplitude equalization for an up-conversion device;

FIG. 5 is a schematic block diagram of a method for amplitude equalization in a down conversion apparatus;

fig. 6 amplitude equalization diagram.

Detailed Description

In order to facilitate an understanding of the invention, the invention is described in more detail below with reference to the accompanying drawings and specific examples. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

The embodiment provides an amplitude equalization method for a down-conversion device on a large-bandwidth broadband, which specifically includes the following steps:

firstly, a c path (a horizontal curve path) of the amplitude equalizer is selected through a switch, and a radio frequency response curve of the whole variable frequency link is obtained through testing. As shown in fig. 1, the general frequency response curve can be approximated by a combination of five expressions, i.e., a positive slope, a negative slope, a horizontal curve, an upper parabola and a lower parabola.

Secondly, finding out a frequency band which does not meet the index requirement in any △ f bandwidth (modulation signal bandwidth) in the radio frequency response curve;

and thirdly, designing a compensation circuit at the intermediate frequency end aiming at the frequency band of which the frequency response curve does not meet the index requirement. The principle of the up-conversion equalization method and the principle of the down-conversion equalization method are respectively shown in fig. 4 and 5.

The compensation circuit is a multi-stage parallel RLC resonance branch and an attenuator, and the RLC resonance branch can adopt a series resonance circuit formed by R, L, C or a resonance circuit formed by L, C in parallel and then connected with R in series. The attenuator may be of the pi type, T type or bridge T type. One exemplary circuit shown in fig. 3 is a three-stage parallel RLC resonant stub plus pi attenuator, where pi attenuators are used to adjust the amplitude uniformity of the equalization circuits.

And finally, selecting a certain path in the equalizer to be communicated with the compensation circuit through a switch, wherein each path in the amplitude equalizer corresponds to one type of compensation curve. Five compensation curves of a, b, c, d and e shown in fig. 2 are used for amplitude equalization, and the equalization effect is shown in fig. 6. The number of the resonance peaks in the two compensation curves of d and e is not limited to 2, and the resonance peaks can be adjusted as required and can be 1, 3 or more.

Claims

1. A large-bandwidth broadband frequency conversion link amplitude equalization method is characterized by comprising the following steps: selecting a horizontal curve path of the amplitude equalizer through a switch, and testing to obtain a radio frequency response curve of the whole variable frequency link;

2. The method as claimed in claim 1, wherein the compensation circuit is a multi-stage parallel RLC resonant branch with an attenuator.

3. The method as claimed in claim 2, wherein the RLC resonant stub is a series resonant circuit formed by R, L, C or a resonant circuit formed by L, C connected in parallel and connected in series with R.

4. The method as claimed in claim 2, wherein the attenuator is pi-type, T-type or bridge T-type.

5. The method as claimed in claim 1, wherein the compensation curve is a curve with a direction opposite to that of the frequency response curve.

6. The method as claimed in claim 5, wherein the compensation curve includes 5 expressions of positive slope, negative slope, horizontal curve, upper parabola and lower parabola and any combination thereof.

7. The method according to any of claims 1-6, wherein the intermediate frequency end is the low frequency end of the frequency conversion link.

8. The method as claimed in claim 8, wherein the if side comprises an input or output if side, or a first if and a second if.