RU2626383C1 - Selective device for protection at opposite rods with suppression of higher harmonics - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: device contains input and output communication lines, three strip (core) resonators with parallel electromagnetic coupling and a length close to the quarter of the wavelength at the average frequency of the operating range. The resonators, which are short-circuited at one end and open on the other one, are turned on in turn, forming a capacitive coupling with the housing. The extreme resonators are connected to the input and output of the device by means of conductive communication lines (CCL) through high-frequency coaxial connectors located on the closed housing equipped with trim screws. In the input leftmost resonator, two ultra-high-frequency (microwave) confining diodes are connected relative to the housing, symmetrically with respect to the point of the CCL attachment in close proximity. One microwave diode is connected to the output rightmost resonator from the side of its open end. On the middle resonator, a microwave diode is connected to it from the short-circuited end of the cavity at a distance equal to the length from the point, where the resonant cavities are connected to the point of their grounding. The output rightmost resonator is connected to the design capacitance, the value of which is equal to the capacitance of the microwave diode located with it in pairs and symmetrically with respect to the point of the CCL attachment. Two strip lines with a wave resistance Z₀ are connected at the input and the output of the device. Two structural tanks are located on the strip lines in the form of metal washers with a thickness of 4-5 mm and have a gap with the device housing. The wave resistance of the strip lines Z₀ is less than the wave resistance of the CCL. An open strip line close to a quarter of the wavelength at the midpoint of the operating frequency range, with a wave resistance equal to the CCL wave resistance, is included between the first (input) and the middle resonators.

EFFECT: increasing noise immunity while maintaining the previous overall dimensions, combining the functions of a bandpass filter and a low-pass filter in one housing, reducing the standing wave voltage factor.

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Description

The proposed device relates to techniques for microwave frequencies and can be used in electronic equipment to protect against breakdown of the cascades of the receiving path as a diode limiter of a high power level with frequency selection of the input signal, providing high attenuation at the input of the receiving device in high power mode and in reception mode outside the passband taking into account the 2nd, 3rd and 5th harmonics.

Known microstrip protective device "Diode power limiter microwave" [1], containing the input and output transmission lines, between which are cascade-connected systems of microstrip lines (MPL), shunted by the limiting diodes. MPL systems are implemented as a resonator on coupled MPLs, with each line being shunted by at least one limiting diode installed at a distance close to a quarter of the wavelength from one of the ends of the resonator. Limit diodes go into transmission mode at a high input power level, regardless of the source of the control signal. Thus, an increase in the level of maximum allowable power is achieved by constructing the input stage based on a through cavity on several coupled MPLs.

The disadvantages of such a device are:

- weak selective properties of a structure consisting of only one resonator;

- lack of adjustment of the resonant circuit in frequency and standing wave voltage coefficient (VSWR);

- high sensitivity of electrical parameters to technological tolerances for the width of the MPL and the length of the resonator.

- The maximum allowable input power is limited.

The closest technical solution to the claimed protection device is "Selective protection device on the oncoming rods" [2], made on the basis of a band-pass filter (PPF) on the oncoming rods and designed according to the method [3], contains input and output communication lines, three strip (rod) resonators with parallel electromagnetic coupling, included in the opposite direction, short-circuited at one end and open at the other, forming a capacitive coupling of the resonators with the device case. The extreme resonators are connected to the input and output of the device using conductive lines through the RF coaxial connectors located on the housing equipped with trimming screws. In the leftmost input resonator relative to the housing, limit microwave diodes are included, arranged in pairs and symmetrically with respect to the point of attachment of the constructive communication line to the resonators. A microwave limiting diode and structural capacitance, the value of which is equal to the capacitance of a microwave diode, is installed at the output extreme right cavity; moreover, the microwave diode and constructive capacitance are located symmetrically with respect to the point of connection of the conductive communication line in close proximity to each other. The microwave limit diode is connected to the middle resonator from the side of its short-circuited end at a distance equal to the length from the point of connection of the conductive communication line of the resonators to the point of their grounding. The limiting diodes in the large input signal mode completely by all three resonators short-circuited on the housing block the input of the protection device and give the maximum signal attenuation level. In reception mode, the device works like a regular bandpass filter with small losses at the fundamental frequency without suppressing higher harmonics: 3rd, 5th or more higher.

The disadvantage of the prototype is the insufficiently high level of technical characteristics, namely: low noise immunity due to the small suppression of odd harmonics - the 3rd and 5th, only 2-3 dB, which means there is a need to use two devices: PPF and a lower filter frequencies (low-pass filter), as a result - an undesirable increase in mass and dimensions, high VSWR.

The technical result of the proposed device is to improve the technical characteristics of the product, namely: increasing noise immunity by suppressing the 3rd and 5th harmonics to 40 dB without increasing the level of losses in the reception mode and maintaining the previous overall dimensions, combining the functions of the PPF and low-pass filter in one case, in addition, the reduction of VSWR to values not exceeding 1.25.

The specified technical result is achieved due to the fact that in the known device containing the input and output communication lines, three strip (rod) resonators with parallel electromagnetic coupling and a length close to a quarter of the wavelength at the middle frequency of the operating range, and the resonators are turned on, short-circuited at one end and open at the other, forming a capacitive coupling with the housing, while the extreme resonators are connected to the input and output of the device using conductive communication lines through high-frequency e coaxial connectors located on a closed housing equipped with trimming screws, in addition, two microwave limit diodes are symmetrically connected to the connection point of the conductive communication line in close proximity to each other in the input extreme left cavity and one microwave diode is connected to the output rightmost to the resonator from the side of its open end, a microwave diode is installed on the middle resonator, connected to it from the side of its short-circuited end at a distance equal to the length from the point of connecting the conductive communication line of the resonators to the point of their grounding, and a constructive capacitance is connected to the output extreme right resonator, the value of which is equal to the capacity of the microwave diode located pairwise and symmetrically with respect to the point of connection of the conductive communication line, additionally connected at the input and output device two strip lines with characteristic impedance Z _0, and two structural capacity to them in the form of metal washers 4-5 mm thick, having a gap from the device housing, etc. When in use, the wave impedance striplines Z ₀ is smaller than the wave resistance conductive link, and introduced open loop strip line close to a quarter wavelength at the midpoint of the operating band, with impedance equal to the characteristic impedance of the conductive link connected between the first ( input) and middle resonators.

In FIG. 1 shows a General view of the design of the claimed protection device. The protection device contains three strip (rod) resonators 1 with parallel electromagnetic coupling, included in the opposite direction, shorted at one end and open at the other, forming a capacitive coupling of the resonators 1 with the housing 4. The extreme resonators 1 are connected to the input and output of the device using a conductive communication line 2 and segments of strip lines 8 connected in series with the RF connectors 5.

In the extreme input and output resonators 1, microwave limiting diodes 3 are connected with respect to the housing 4. Two microwave diodes 3 are located symmetrically with respect to the connection point of the conductive communication line 2 in the input extreme left resonator 1. Since the dimensions of the housing allow placing a larger number of diodes 3, In order to increase the power of the input signal, their number can be increased to 4 or 6. At the output extreme right resonator, a microwave limiting diode 3 and a structural capacitance 7, made in the form of a metal pin, are installed Connected, for example, M8 threaded to the housing 4, forming capacitive coupling between the casing and the resonator. Resonators 1, conductive communication lines 2 and segments of strip lines 8 are placed in a grounded housing 4, equipped with high-frequency coaxial connectors 5 and trimming screws 6 with a threaded connection, for example M8. The microwave limit diode 3 is connected to the middle resonator from the side of its short-circuited end at a distance equal to the length from the point of connection of the conductive communication line 2 to the housing 4.

At the input and output segments of the strip line 8, there are structural containers 9, each of which is a metal disk 4-5 mm thick and with a diameter smaller than the internal height of the housing, in order to create capacitive coupling between the inner conductor of the strip line 8 and the housing devices.

Between the input and middle resonators there is an open strip line 10 with a length close to a quarter of the wavelength at the midpoint of the operating frequency range, and with a wave impedance equal to the wave impedance of the communication line. This line by moving between the resonators plays the role of adjustment for VSWR at the midpoint of the operating frequency range. In addition, two structural capacitance 9, located on the segments of the strip lines 8 at the input and output of the device, and the strip open line 10 form the capacitance for the five-link low-pass filter. The inductances of this filter are conductive communication lines 2 located at the input and output of the device. In FIG. Figure 2 shows the equivalent circuit of the low-pass filter located in a common housing, where the structural capacitances 9 are designated as C1 and C5, the strip open line 10 is designated as C3, and the conductive communication lines 2 are indicated as L2 and L4. Moreover, for the filter, the following conditions must be met: C1 = C5, L2 = L4, C3 = 4C1. The sizes and ratings of the elements of the device were calculated using [4].

The protection device operates as follows. With a large level of power at the input of the protection device, microwave diodes on all three resonators open (transmission mode) and their small resistance (r_etc≤1 Ω) short-circuit the input of the device to the housing, reflecting the incident power back to the transmitter. The level of leaking power at the input of the receiver is not more than 2-3 mW. The upper limit of the input continuous power is 240-250 watts. When the input power of a low level (reception mode) arriving at the input of the device, the diodes are closed and the device operates as a normal PPF on the oncoming rods with losses of less than 1.5 dB with VSWR ≤1.25. The structural capacities included at the input and output of the device, together with the open-line capacitance connected between the first and second resonators, allow you to realize the properties of the low-pass filter, which improves the matching at the input of the device at low frequencies and increases the attenuation of the signal at high frequencies, i.e. suppresses the higher harmonics of the frequency range from 40 dB to 60 dB.

In FIG. Figure 3 shows the result of an experiment on measuring attenuation as a function of frequency. It can be seen from the results that the second harmonic located between the 3rd and 4th points experiences an attenuation of approximately 40 dB caused by the presence of PPF. The third harmonic, located between the 5th and 6th points, is attenuated to 40 dB due to the addition of a low-pass filter, it can also be observed that the total losses of the combined device do not exceed 1.5 dB.

Thus, due to the inclusion of constructive containers in the form of metal washers, as well as an open strip line close to a quarter of the wavelength at the midpoint of the operating frequency range, and with a wave impedance equal to the wave impedance of the conductive communication line, the technical characteristics of the product improved, and namely: increased noise immunity due to suppression of the 3rd and 5th harmonics to 40 dB instead of 2-3 dB for the prototype, losses in the reception mode remained at the same level while maintaining the same overall dimensions trench devices and functions PPF were combined, and the LPF in the same housing, furthermore, decreased to values of VSWR not exceeding 1.25.

Information sources

1. Patent No. 2258278, filed. No. 2003125468/09 dated June 24, 2009. Shapovalova V.V., Ilyichev N.V. Microwave diode power limiter.

2. Utility Model Patent No. 156173 by Application No. 2014445365 of June 7, 2011. Kustov OV, Pigarev V.G. Selective protection device on oncoming rods. H01P 1/22.

3. Matthew D.L. Young L., Jones E.M.T. Microwave filters, matching circuits and communication circuits. Edited by L.V. Alekseeva. M .: Communication. 1972, part 2, pp. 97-102.

4. Khalyapin B.D. Coaxial and strip microwave filters. M .: Communication. 1969

Claims (1)

A selective protection device on oncoming rods containing input and output communication lines, three strip (rod) resonators with parallel electromagnetic coupling, close to a quarter of the wavelength at the middle frequency of the operating range, the resonators being turned on, short-circuited at one end and open at the other forming a capacitive coupling with the housing, while the extreme resonators are connected to the input and output of the device using conductive communication lines through high-frequency coaxial connectors, located In addition, in the input leftmost cavity, two microwave frequency limiting diodes are symmetrically connected to the connection point of the conductive communication line in close proximity to each other and one microwave diode is connected to the output extreme right resonator from the side of its open end, a microwave diode is installed on the middle resonator connected to it from the side of its short-circuited end at a distance equal to the length of connection points of the conductive communication line of the resonators to the point of their grounding, and a structural capacitance is connected to the output extreme right resonator, the value of which is equal to the capacity of the microwave diode located pairwise and symmetrically with respect to the connection point of the conductive communication line, characterized in that at the input and output the device includes segments of a strip line with a wave impedance Z ₀ with connected capacities in the form of metal washers having a gap with the device’s body, and the wave impedance Z _{0 is} less than the wave impedance of the conductive communication line, in addition, between the first (input) and middle resonators an open strip line is included, its length being close to a quarter of the wavelength at the midpoint of the operating frequency range, and with a wave impedance equal to the wave impedance of the line communication.

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