Extremely narrow band frequency selection assembly and impedance matcher setting method

Abstract

The invention discloses an ultra-narrow-band frequency selection assembly and an impedance matcher setting method. The ultra-narrow-band frequency selection assembly comprises a radio frequency connector, a rectangular socket, a metal shell, a printed board, a radio frequency switch, a plurality of middle impedance matchers and a plurality of ultra-narrow-band filters. The middle impedance matcher comprises an inner parallel inductor, a series inductor, an outer parallel inductor and a resistor; the series inductor is connected between the ultra-narrow-band filter and the radio frequency switch, one end of the internal parallel inductor is grounded, and the other end of the internal parallel inductor is connected between the series inductor and the corresponding ultra-narrow-band filter; one end of the external parallel inductor is grounded, and the other end is connected between the series inductor and the corresponding radio frequency switch; and one end of the resistor is grounded, and the other end of the resistor is connected between the series inductor and the corresponding radio frequency switch and is opposite to the outside, and the inductor is far away from the corresponding ultra-narrow-band filter. The narrow-band SAW filter can play roles in impedance matching and amplitude balancing, the loss and passband ripples of the narrow-band SAW filter are improved, and the amplitude consistency of the ultra-narrow-band frequency selection assembly is adjusted.

Description

Technical Field

[0001] The invention relates to an extremely narrowband frequency selection component and an impedance matching device setting method, belonging to the technical field of radio frequency communication. Background Art

[0002] The frequency selection component is used in radar receivers and has excellent frequency selection and anti-interference performance. This component is used to complete the functions of radar receiving frequency selection, clutter and harmonic suppression, etc. With the development of communication technology, the electromagnetic environment is becoming more and more complex, and the performance requirements of wireless communication systems are also constantly improving. There is an urgent need for an extremely narrowband frequency selection component to filter out various interference signals. In order to improve the communication quality of the communication system, it is required that the channels have good amplitude consistency.

[0003] There are two problems with narrowband frequency-selective components based on surface acoustic wave (SAW) technology: 1. To achieve smaller insertion loss and passband ripple, it is necessary to design matching networks at the input and output ports for port impedance matching, such as Figure 1 As shown; 2. Narrowband filters are more sensitive to the process and have poor amplitude consistency, making it difficult to meet user requirements. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide an extremely narrowband frequency selection component and an impedance matching device setting method, which can play the role of impedance matching and amplitude balance, improve the loss and passband ripple of the narrowband SAW filter, and adjust the amplitude consistency of the extremely narrowband frequency selection component.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows: An extremely narrowband frequency selection component includes an RF connector, a rectangular socket, a metal housing, a printed circuit board, an RF switch I, an RF switch II, a plurality of intermediate impedance matchers and a plurality of extremely narrowband filters; the two ends of each extremely narrowband filter are respectively connected to the intermediate impedance matcher, all the intermediate impedance matchers located on the same side of the extremely narrowband filter are connected to the RF switch I, and all the intermediate impedance matchers located on the other same side of the extremely narrowband filter are connected to the RF switch II. The intermediate impedance matcher includes an internal parallel inductor Z1, a series inductor Z2 and an external parallel inductor Z3; the two ends of the series inductor Z2 are respectively connected to the corresponding extremely narrowband filter and the RF switch, one end of the internal parallel inductor Z1 is grounded, and the other end is connected between the series inductor Z2 and the corresponding extremely narrowband filter; one end of the external parallel inductor Z3 is grounded, and the other end is connected between the series inductor Z2 and the corresponding RF switch, so that the three inductors form a π-type impedance matching network to achieve mutual matching between any impedances.

[0006] Furthermore, the intermediate impedance matcher also includes a resistor Z4, one end of which is grounded, and the other end of which is connected between the series inductor Z2 and the corresponding radio frequency switch and is far away from the corresponding extremely narrowband filter relative to the external parallel inductor Z3.

[0007] Furthermore, the inductance value of the internal parallel inductor Z1 is less than or equal to the inductance value of the series inductor Z2; and the inductance value of the external parallel inductor Z3 is between the inductance value of the internal parallel inductor Z1 and the inductance value of the series inductor Z2.

[0008] The present invention also provides a method for setting the intermediate impedance matcher of the above-mentioned ultra-narrow band frequency selection component, and the specific steps are as follows: 1) Set up the network analyzer, set the start and end frequencies, and display at least three curves on the network analyzer; one of the curves has a transmission mode of S 21 , the format is logarithmic amplitude mode; a curve transmission mode is S 11 , the format is standing wave mode; a curve transmission mode is S 22 , the format is standing wave mode; 2) First connect the internal parallel inductor and the series inductor. The inductance value of the internal parallel inductor is less than or equal to the inductance value of the series inductor. 3) Adjust the inductance of the internal parallel inductor and the series inductor; if the minimum value of the overall trend of the standing wave curve on the network analyzer is on the right side of the filter passband, increase the inductance of the internal parallel inductor or the series inductor until the minimum value of the overall trend of the standing wave curve falls within the filter passband; if the minimum value of the overall trend of the standing wave curve is on the left side of the filter passband, reduce the inductance of the internal parallel inductor or the series inductor until the minimum value of the overall trend of the standing wave curve falls within the filter passband; 4) Connect an external parallel inductor whose inductance value is between the internal parallel inductor and the series inductor; 5) Solder resistor Z4 to adjust the insertion loss between channels; the resistance value of resistor Z4 is determined according to the insertion loss value of all channels, and the general resistance value is between 100Ω and 1000Ω.

[0009] Compared with the prior art, the present invention has the following beneficial effects: The present invention can play the role of impedance matching and amplitude balancing, improve the loss and passband ripple of the narrowband SAW filter, and adjust the amplitude consistency of the extremely narrowband frequency selection component. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 -Schematic diagram of the existing SAW filter matching network structure.

[0011] Figure 2 - Principle block diagram of the frequency selection component of the present invention.

[0012] Figure 3 -The circuit structure diagram of the impedance matcher Dnm of the present invention.

[0013] Figure 4 -Test curve diagram of the matching process of the matching device of the present invention; wherein, (a) the amplitude-frequency curve is not matched; (b) only the internal parallel and series inductors are welded; (c) the internal parallel and series inductors are adjusted; (d) the external parallel inductors are increased; (e) the resistance is increased.

[0014] Figure 5 -Typical test curve diagram of the frequency selection component of the present invention; wherein (a) no resistance is added; (b) resistance is added. DETAILED DESCRIPTION

[0015] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0016] The present invention discloses an extremely narrowband frequency selection component, including an RF connector, a rectangular socket, a metal housing, a printed circuit board, an RF switch I, an RF switch II, a plurality of intermediate impedance matchers, and a plurality of extremely narrowband filters; the two ends of each extremely narrowband filter are respectively connected to the intermediate impedance matcher, all the intermediate impedance matchers on the same side of the extremely narrowband filter are connected to the RF switch I, and all the intermediate impedance matchers on the other same side of the extremely narrowband filter are connected to the RF switch II, and the outer sides of the RF switch I and the RF switch II are respectively connected to the end impedance matchers. The overall principle block diagram of the present invention is shown as follows: Figure 2 shown.

[0017] The circuit structure of the intermediate impedance matching device of the present invention is as follows: Figure 3 As shown, from Figure 3 It can be seen that the improved intermediate impedance matching device includes an inductor L (Z1, Z2 and Z3) and resistors R (Z4), where Z1 is an internal parallel inductor, Z2 is a series inductor, and Z3 is an external parallel inductor. The two ends of the series inductor Z2 are respectively connected to the corresponding extremely narrowband filter and the RF switch, one end of the internal parallel inductor Z1 is grounded, and the other end is connected between the series inductor Z2 and the corresponding extremely narrowband filter; one end of the external parallel inductor Z3 is grounded, and the other end is connected between the series inductor Z2 and the corresponding RF switch. One end of the resistor Z4 is grounded, and the other end is connected between the series inductor Z2 and the corresponding RF switch and is far away from the corresponding extremely narrowband filter relative to the external parallel inductor Z3.

[0018] The inductance value of the internal parallel inductor Z1 is less than or equal to the inductance value of the series inductor Z2; the inductance value of the external parallel inductor Z3 is between the inductance value of the internal parallel inductor Z1 and the inductance value of the series inductor Z2.

[0019] The impedance of the circuit and the frequency of the filter can be adjusted by the inductor, and the circuit balance can be adjusted and the consistency between channels can be improved by optimizing the impedance through the resistor.

[0020] The three inductors form a π-type impedance matching network, which can achieve mutual matching between arbitrary impedances, thereby improving filter loss and reducing passband ripple; the resistor can adjust the channel amplitude, thereby achieving amplitude balance between multiple channels of the frequency selection component.

[0021] The intermediate impedance matcher of the ultra-narrowband frequency selection component of the present invention is set as follows: Set the network analyzer, set the start and end frequencies, set the number of points to 1601, and display at least three curves. The transmission mode of one of the curves is S 21 , the format is logarithmic amplitude mode; a curve transmission mode is S 11 , the format is standing wave mode; a curve transmission mode is S 22 , the format is standing wave mode. After setting, calibrate the instrument.

[0022] Prioritize welding the internal parallel inductor Z1 and the series inductor Z2. Generally, the inductance value of the internal parallel inductor is not greater than the series inductor. The test curve is as follows: Figure 4 (b). Figure 4 (a) is the amplitude-frequency curve when there is no matching.

[0023] If the standing wave curve appears like S 11 As shown, that is, the minimum value of the overall trend of the standing wave curve on the network analyzer is on the right side of the filter passband, then the inductance value of the internal parallel inductor or the series inductor needs to be increased, and the inductance value of the series inductor is increased first; until the minimum value of the overall trend of the standing wave curve falls within the filter passband; if the standing wave curve appears as shown S 22 As shown, the minimum value of the overall trend of the standing wave curve is on the left side of the filter passband. It is necessary to reduce the inductance of the internal parallel inductor or the series inductor, and give priority to reducing the inductance of the series inductor until the minimum value of the overall trend of the standing wave curve falls within the filter passband. The test curve after adjusting the matching circuit is as follows: Figure 4 (c) as shown.

[0024] Weld the external parallel inductor Z3. Generally, the inductance value of the external parallel inductor is between the inductance values ​​of the internal parallel inductor and the series inductor. The test curve is as follows: Figure 4 (d) as shown.

[0025] Weld resistor Z4 to adjust the insertion loss between channels. The value of resistor Z4 should be determined according to the insertion loss of all channels. The general resistance value is between 100Ω and 1000Ω. Figure 4(e) is the test curve after welding the resistor, and the insertion loss increased by about 0.6dB.

[0026] Figure 5 (a) is the test curve of the frequency-selective component without adding resistance (only three inductors) in the impedance matcher, and the amplitude consistency of each channel is about 1.2dB; Figure 5 (b) is the test curve of the frequency selection component after adding resistors to the impedance matcher to adjust the loss of each channel. The amplitude consistency of each channel is about 0.5dB. It can be seen that the present invention can adjust the circuit balance while optimizing the impedance through resistors, and improve the consistency between channels.

[0027] When the present invention is implemented, a narrowband surface acoustic wave filter is first designed according to the index requirements of the frequency selection component. Then, a suitable RF connector and rectangular socket are selected according to the structural requirements, and a specific metal shell is designed. The RF connector and the rectangular socket are fixed to the metal shell by screws; the terminals of the RF connector and the rectangular socket are welded on the printed circuit board; the RF switch, the extremely narrowband filter and the impedance matcher are evenly arranged on both sides of the printed circuit board.

[0028] The above embodiments of the present invention are merely examples for illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes and modifications can be made based on the above description. It is impossible to list all the embodiments here. Any obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. An extremely narrowband frequency selection component, comprising an RF connector, a rectangular socket, a metal housing, a printed circuit board, an RF switch I, an RF switch II, a plurality of intermediate impedance matchers and a plurality of extremely narrowband filters; the two ends of each extremely narrowband filter are respectively connected to the intermediate impedance matcher, all the intermediate impedance matchers located on the same side of the extremely narrowband filter are connected to the RF switch I, and all the intermediate impedance matchers located on the other same side of the extremely narrowband filter are connected to the RF switch II, characterized in that: The intermediate impedance matcher includes an internal parallel inductor Z1, a series inductor Z2 and an external parallel inductor Z3; the two ends of the series inductor Z2 are respectively connected to the corresponding extremely narrowband filter and the radio frequency switch, one end of the internal parallel inductor Z1 is grounded, and the other end is connected between the series inductor Z2 and the corresponding extremely narrowband filter; one end of the external parallel inductor Z3 is grounded, and the other end is connected between the series inductor Z2 and the corresponding radio frequency switch, so that the three inductors form a π-type impedance matching network to achieve mutual matching between arbitrary impedances.

2. The ultra-narrowband frequency selection component according to claim 1, characterized in that: The intermediate impedance matcher further includes a resistor Z4, one end of which is grounded, and the other end of which is connected between the series inductor Z2 and the corresponding radio frequency switch and is far away from the corresponding extremely narrowband filter relative to the external parallel inductor Z3.

3. The ultra-narrowband frequency selection component according to claim 1, characterized in that: The inductance value of the internal parallel inductor Z1 is less than or equal to the inductance value of the series inductor Z2; the inductance value of the external parallel inductor Z3 is between the inductance value of the internal parallel inductor Z1 and the inductance value of the series inductor Z2.

4. A method for setting an intermediate impedance matcher of an extremely narrowband frequency selective component according to any one of claims 1 to 3, characterized in that: The steps are as follows, 1) Set up the network analyzer, set the start and end frequencies, and display at least three curves on the network analyzer; one of the curves has a transmission mode of S 21 , the format is logarithmic amplitude mode; A curve transmission mode is S 11 , the format is standing wave mode; A curve transmission mode is S 22 , the format is standing wave mode; 2) First connect the internal parallel inductor and the series inductor. The inductance value of the internal parallel inductor is less than or equal to the inductance value of the series inductor. 3) Adjust the inductance of the internal parallel inductor and the series inductor; if the minimum value of the overall trend of the standing wave curve on the network analyzer is on the right side of the filter passband, increase the inductance of the internal parallel inductor or the series inductor until the minimum value of the overall trend of the standing wave curve falls within the filter passband; if the minimum value of the overall trend of the standing wave curve is on the left side of the filter passband, reduce the inductance of the internal parallel inductor or the series inductor until the minimum value of the overall trend of the standing wave curve falls within the filter passband; 4) Connect an external parallel inductor whose inductance value is between the internal parallel inductor and the series inductor.

5. The impedance matching device setting method of an ultra-narrowband frequency selection component according to claim 4, characterized in that: After step 4), the following steps are also included: 5) Solder resistor Z4 to adjust the insertion loss between channels; the resistance value of resistor Z4 is determined according to the insertion loss value of all channels.

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