A low-loss tuned matching network

Abstract

The present invention belongs to the technical field of shortwave communication systems and discloses a low-loss tuning and matching network, comprising an adjustable inductor and a second adjustable capacitor connected in series between a first node and a second node, the first node being electrically connected to a radio frequency input terminal, and the second node being electrically connected to an antenna; a first adjustable capacitor being provided between the first node and ground; and a third adjustable capacitor being provided between the second node and ground. The adjustable inductor comprises a plurality of inductors connected in series, each inductor being connected in parallel with a relay to control whether the corresponding inductor is included in the tuning and matching network; an isolable inductor group is formed by a plurality of inductors with inductance values in the first m digits, and single-pole double-throw relays are provided at both ends of the inductor group; when the isolable inductor group is not in use, the single-pole double-throw relay is directly turned on. The present invention uses an isolation relay to completely separate unused larger inductor coils from the radio frequency path at medium and high frequencies, eliminating their impact on the impedance of the antenna feed system.

Description

Technical Field

[0001] The present invention belongs to the technical field of shortwave communication systems, and in particular relates to a low-loss tuning and matching network suitable for realizing an impedance matching system between a shortwave transceiver and a shortwave antenna using an antenna tuner. Background Art

[0002] A shortwave communication system consists of a shortwave transceiver, an antenna tuner, and a shortwave antenna (hereinafter referred to as the antenna). The antenna tuner and antenna are collectively referred to as the antenna feed system. Shortwave antennas are typically narrowband antennas, and their input impedance varies with frequency, representing a complex impedance. The output impedance of a typical shortwave transceiver is 50Ω, so an antenna tuner is required between the shortwave transceiver and the antenna to achieve impedance matching. This ensures that the transceiver's power is transmitted to the antenna and radiated outwards to the antenna to the maximum extent possible.

[0003] Antenna tuners achieve antenna matching by changing the connection state of matching components (such as capacitors and inductors) in the tuning network. The RF signal from the transceiver is transmitted to the shortwave antenna through the tuning network. This process can produce varying degrees of loss depending on factors such as the tuning network configuration, component layout, and connections.

[0004] The traditional π-type inductor network isolation method is: when an inductor coil is in use, the corresponding relay is in an open-circuit state; when the inductor coil is not in use, the corresponding relay is in a short-circuit state. However, this method does not completely isolate the unused inductor coil from the RF path; the short-circuited inductor coil still affects the antenna impedance, reducing the real part of the impedance in some frequency bands, resulting in the use of more inductance and capacitance during tuning, and increasing losses when the RF passes through. Through testing, it was found that the greater the inductance of the short-circuited inductor coil, the greater the impact on the antenna impedance. Summary of the Invention

[0005] In order to solve the above problems, the purpose of the present invention is to propose a low-loss tuning and matching network. Based on the relationship between frequency and inductance value, the larger inductor coil that is not used at medium and high frequencies is completely separated from the RF path by an isolation relay, eliminating its impact on the impedance of the antenna feed system, thereby reducing the values of the inductor and capacitor used during tuning, thereby reducing the loss of the RF signal when passing through the antenna tuning network, and thus improving the signal strength transmitted to the antenna, thereby enhancing the communication capability of the shortwave communication system.

[0006] In order to achieve the above purpose, the present invention adopts the following technical solutions to solve it.

[0007] A low-loss tuned matching network comprises: an adjustable inductor and a second adjustable capacitor connected in series between a first node and a second node, wherein the first node is electrically connected to a radio frequency input terminal, and the second node is electrically connected to an antenna;

[0008] A first adjustable capacitor is provided between the first node and the ground;

[0009] A third adjustable capacitor is provided between the second node and the ground;

[0010] The adjustable inductor is composed of a plurality of inductors connected in series, and each inductor is connected in parallel with a relay to control whether the corresponding inductor is added to the tuning matching network;

[0011] The inductance values of the multiple inductors decrease in sequence, and an isolable inductor group is composed of a number of inductors whose inductance values are in the first m digits. Single-pole double-throw relays are respectively provided at both ends of the isolable inductor group. When the isolable inductor group is not in use, the single-pole double-throw relays at both ends are directly turned on to isolate the isolable inductor group. m is a positive integer.

[0012] Furthermore, the maximum inductance of the inductor is 32 μH or 16 μH, and the inductances of the plurality of inductors decrease in sequence with a scaling factor of 1 / 2.

[0013] Furthermore, the minimum inductance of the inductor is 0.022 μH.

[0014] Furthermore, the minimum inductance of the inductors in the isolable inductor group is 4 μH.

[0015] A tuning method for a low-loss tuned matching network comprises the following steps:

[0016] Step 1: Determine the impedance region of the antenna tuner when it enters the adjustable inductance process in the antenna impedance original diagram, and determine the target impedance conductance value B;

[0017] Step 2: determining the relationship between the tuning frequency and the maximum inductance value required for the adjustable inductor based on the impedance region corresponding to the adjustable inductor and the target impedance conductance value;

[0018] Step 3: determine whether the current tuning frequency is greater than a frequency threshold; if so, isolate the isolable inductor group; otherwise, turn on the isolable inductor group.

[0019] Furthermore, the relationship between the tuning frequency and the maximum inductance value required for the adjustable inductor is determined based on the impedance region corresponding to the adjustable inductor and the target impedance conductance value, specifically:

[0020] First, determine the impedance Z after adding the adjustable inductor:

[0021] Z=R L +jX L +jωL1,

[0022] ω=2πf;

[0023] Among them, RL is the antenna resistance, X L is the antenna reactance, j is the imaginary unit, L1 is the inductance value of the adjustable inductor, and f is the current tuning frequency, which ranges from 2MHz to 30MHz;

[0024] Secondly, determine the conductance value after adding the adjustable inductor

[0025] Finally, the maximum inductance required for each tuning frequency is determined based on the target conductance value and the impedance region corresponding to the adjustable inductor.

[0026] Furthermore, the frequency threshold is 10 MHz.

[0027] Furthermore, the target impedance conductance value is 0.02S.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] Based on the relationship between frequency and inductance value, the present invention uses a single-pole double-throw relay to completely separate the larger inductor coil that is not used at medium and high frequencies from the RF path, eliminating its impact on the impedance of the antenna feed system. This reduces the values of the inductor and capacitor used during tuning, thereby reducing the loss of the RF signal when passing through the antenna tuner network, thereby increasing the signal strength transmitted to the antenna and improving the communication capability of the shortwave communication system. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] Figure 1 is a connection diagram of the inductor network of the present invention;

[0032] Figure 2 The figure is an internal connection diagram of an adjustable inductor in the prior art;

[0033] Figure 3 The original diagram of antenna impedance and the impedance region diagram of the adjustable inductor in an embodiment of the present invention are shown;

[0034] Figure 4 An internal connection diagram of an adjustable inductor in a low-loss tuned matching network of the present invention;

[0035] In the above figure, 1 is the first adjustable capacitor; 2 is the adjustable inductor; 3 is the second adjustable capacitor; 4 is the third adjustable capacitor; 5 is the relay; 6 is the inductor; 61 is the isolable inductor group; 62 is the single-pole double-throw relay. DETAILED DESCRIPTION

[0036] The embodiments and effects of the present invention are described in further detail below with reference to the accompanying drawings.

[0037] Example 1

[0038] refer to Figure 1 and Figure 4 The present invention proposes a low-loss tuning and matching network, comprising: an adjustable inductor 2 (L1) and a second adjustable capacitor 3 (C2) connected in series between a first node and a second node, the first node being electrically connected to a radio frequency input terminal, and the second node being electrically connected to an antenna; a first adjustable capacitor 1 (C1) being provided between the first node and ground; and a third adjustable capacitor 4 (C3) being provided between the second node and ground; the adjustable inductor 2 (L1) being composed of a plurality of inductors 6 connected in series, each inductor 6 being connected in parallel to a relay 5 to control whether the corresponding inductor 6 is included in the tuning and matching network; the inductance values of the plurality of inductors 6 being successively decreased, and an isolable inductor group 61 being composed of a plurality of inductors 6 with inductance values in the first m positions, and single-pole double-throw relays 62 being provided at both ends of the isolable inductor group 61; when the isolable inductor group 61 is not in use, the single-pole double-throw relays 62 at both ends are directly turned on to isolate the isolable inductor group 61; and m is a positive integer.

[0039] Specifically, to balance high- and low-end tuning capabilities and tuning accuracy, the tunable inductor 2 (L1) typically consists of 11 or 12 inductors. For example, a certain antenna tuner uses 11 tunable inductors 2 in its tuning network, with inductance values ranging from 22nH, 42nH, 79nH, 125nH, 250nH, 500nH, 1μH, 2μH, 4μH, 8μH, and 16μH, respectively.

[0040] Since the value of adjustable inductor 2 is inversely proportional to the tuning frequency, calculation shows that when the tuning frequency is 2 MHz, the maximum inductance value of adjustable inductor 2 (L1) needs to be 16.7 μH; when the frequency is 10 MHz, the maximum inductance value of adjustable inductor 2 (L1) needs to be 3.34 μH; when the frequency is 30 MHz, the maximum inductance value of adjustable inductor 2 (L1) needs to be 1.11 μH.

[0041] From the above results, it can be seen that when the local tuner is tuning in the low frequency band, the inductor coils of 16μH and below are used; in the medium and high frequency bands (greater than 10MHz), the 4μH, 8μH, and 16μH inductor coils are not used.

[0042] The traditional adjustable inductor 2 connection method is as follows Figure 2As shown, when an inductor is in use, the corresponding relay 5 is in an open-circuit state; when the inductor is not in use, the corresponding relay 5 is in a short-circuit state. This approach cannot completely isolate the unused inductor from the RF path, affecting the antenna impedance, reducing the real part of the impedance in some frequency bands. This results in more inductance and capacitance being used during tuning, resulting in greater losses when RF passes through. Testing has found that the larger the value of the unused inductor, the greater the impact on the antenna impedance.

[0043] The low-loss tuning and matching network of the embodiment of the present invention comprehensively considers factors such as component utilization, spatial layout, and the impact on other devices, and is designed for low-loss tuning and matching networks in the mid- and high-frequency bands. When tuning the mid- and high-frequency bands, the three unused and largest inductor coils, namely m=3 (4μH, 8μH, 16μH), form an isolable inductor group 61, which is completely isolated. The tuning network connection method is as follows: Figure 4 The connection method of the 22nH, 42nH, 79nH, 125nH, 250nH, 500nH, 1μH, and 2μH inductors remains unchanged, and a single-pole double-throw relay 62 is added at each end of the 4μH, 8μH, and 16μH inductors, as shown in FIG. Figure 4 K27 and K28 in the β-catenin form a straight path ( Figure 4 The state shown is the through state) to completely isolate it. This can eliminate the adverse effects caused by the three large inductors connected in the RF path. When isolation is not required, the single-pole double-throw relay 62 is Figure 4 Pins 1 and 3 of K27 and K28 are connected, and the device is used with a large inductance value.

[0044] Example 2

[0045] A tuning method for a low-loss tuned matching network comprises the following steps:

[0046] Step 1: Determine the impedance region of the antenna tuner when it enters the adjustable inductance process in the antenna impedance original diagram, and determine the target impedance conductance value B;

[0047] In the embodiment of the present invention, the impedance region when entering the adjustable inductance process is as follows Figure 3 As shown in the shaded area in the figure. Figure 3 After the shaded area, or after adjusting the antenna impedance to the shaded area by adding other network components, the antenna tuner adds an adjustable inductor according to the tuning process, adjusts the impedance to conductance B = 0.02S, and then adds the front-end parallel capacitor C1.

[0048] Step 2: determining the relationship between the tuning frequency and the maximum inductance value required for the adjustable inductor based on the impedance region corresponding to the adjustable inductor and the target impedance conductance value;

[0049] First, determine the impedance Z after adding the adjustable inductor:

[0050] Z=R L +jX L +jωL1 (1)

[0051] ω=2πf; (2)

[0052] Among them, R L is the antenna resistance, X L is the antenna reactance, j is the imaginary unit, L1 is the inductance value of the adjustable inductor, and f is the current tuning frequency, which ranges from 2MHz to 30MHz;

[0053] Secondly, determine the conductance value after adding the adjustable inductor

[0054] Finally, the maximum inductance required for each tuning frequency is determined based on the target conductance value and the impedance region corresponding to the adjustable inductor.

[0055] In practice, each point on the Smith chart corresponds to an antenna resistance and reactance value. Based on the target impedance and conductance values, multiple right-edge points are selected within the impedance region when entering the adjustable inductance process (the corresponding resistance and reactance are known from the chart after the points are determined). The required maximum inductance value is then calculated using formula (3). The maximum value of ωL1 required is approximately 210Ω. This allows us to determine the maximum inductance required for different frequencies. In this embodiment, when the tuning frequency is 2 MHz, the maximum inductance required for the adjustable inductor is 16.7 μH; when the frequency is 10 MHz, the maximum inductance required for the adjustable inductor is 3.34 μH; and when the frequency is 30 MHz, the maximum inductance required for the adjustable inductor is 1.11 μH.

[0056] The above calculations show that when tuning in the low-frequency band (below 10MHz), an inductor of 16μH or less is used. However, in the mid- to high-frequency band (above 10MHz), inductors of 4μH, 8μH, and 16μH are no longer used. Therefore, 10MHz can be used as a frequency threshold for selecting the tuning method.

[0057] Step 3: determine whether the current tuning frequency is greater than a frequency threshold; if so, isolate the isolable inductor group; otherwise, turn on the isolable inductor group.

[0058] In this embodiment, inductors corresponding to 4μH, 8μH, and 16μH form an isolable inductor group, and single-pole double-throw relays are used at both ends to switch the RF signal between direct passthrough and three inductors in series. When direct passthrough is used, the isolated inductor group composed of the three inductors is completely isolated, which can eliminate the adverse effects caused by the connection of three large inductors in the RF path.

[0059] In this embodiment, the low-loss adjustable inductor is connected to three low-usage, high-inductance coils with a single-pole, double-throw relay at each end. When the three high-inductance coils are not in use at medium or high frequencies, the single-pole, double-throw relays are switched to a through state, completely isolating them from the RF network.

[0060] Effect verification

[0061] A conventional π-type inductor network and the low-loss tuning and matching network of the present invention were applied to a certain model of airborne antenna tuner. The proposed network demonstrated excellent matching performance across the entire frequency band. The temperatures of the inductor coils in both networks were measured using a thermometer. The results are shown in Table 1.

[0062] Table 1 Comparison of inductor coil temperature between the present invention and the traditional network

[0063]

[0064] As can be seen from Table 1, in the medium and high frequency bands, the heat generation of the antenna tuner inductor coil of the present invention is significantly reduced, reducing the loss of the antenna tuner itself; the reduction in the heat generation of the antenna tuner itself improves the reliability of the antenna tuner network inductor coil and can effectively improve the long-term working ability of the antenna tuner.

[0065] The voltage output from the two networks to the antenna was measured using a Rogowski coil at the RF output of the antenna tuner. The results are shown in Table 2.

[0066] Table 2 Comparison of antenna input voltage between the present invention and the traditional network

[0067]

[0068]

[0069]

[0070] As can be seen from Table 2, in the mid- and high-frequency bands above 7 MHz, the voltage transmitted to the antenna by the antenna tuner network of the present invention is improved. When the antenna is the same, the energy transmitted to the antenna is greater, ensuring that the RF power of the transmitter is effectively transmitted to the antenna, thereby improving the radiation efficiency of the antenna feed system.

[0071] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A tuning method for a low-loss tuned matching network, characterized in that: A low-loss tuned matching network is applied, the low-loss tuned matching network comprising: an adjustable inductor and a second adjustable capacitor connected in series between a first node and a second node, the first node being electrically connected to a radio frequency input terminal, and the second node being electrically connected to an antenna; A first adjustable capacitor is provided between the first node and the ground; A third adjustable capacitor is provided between the second node and the ground; The adjustable inductor is composed of a plurality of inductors connected in series, and each inductor is connected in parallel with a relay to control whether the corresponding inductor is added to the tuning matching network; The inductance values of the multiple inductors decrease in sequence, and the inductors with inductance values in the first m positions form an isolable inductor group. Single-pole double-throw relays are respectively provided at both ends of the isolable inductor group. When the isolable inductor group is not in use, the single-pole double-throw relays at both ends are directly turned on to isolate the isolable inductor group. m is a positive integer. The maximum inductance of the inductor is 32 μH or 16 μH, and the inductances of the multiple inductors decrease in sequence with a scaling factor of 1 / 2; The minimum inductance value of the inductor is 0.022 μH; The minimum inductance of the inductor in the isolable inductor group is 4 μH; The tuning method comprises the following steps: Step 1: Determine the impedance region of the antenna tuner when it enters the adjustable inductance process in the antenna impedance original diagram, and determine the target impedance conductance value B; Step 2: determining the relationship between the tuning frequency and the maximum inductance value required for the adjustable inductor based on the impedance region corresponding to the adjustable inductor and the target impedance conductance value; Step 3: determine whether the current tuning frequency is greater than a frequency threshold; if so, isolate the isolable inductor group; otherwise, turn on the isolable inductor group.

2. The tuning method of the low-loss tuned matching network according to claim 1, characterized in that: The relationship between the tuning frequency and the maximum inductance required for the adjustable inductor is determined based on the impedance region corresponding to the adjustable inductor and the target impedance conductance value, specifically: First, determine the impedance Z after adding the adjustable inductor: Z=R L +jX L +jωL1, ω=2πf; Among them, R L is the antenna resistance, X L is the antenna reactance, j is the imaginary unit, L1 is the inductance value of the adjustable inductor, and f is the current tuning frequency, which ranges from 2MHz to 30MHz; Secondly, determine the conductance value after adding the adjustable inductor Finally, the maximum inductance required for each tuning frequency is determined based on the target conductance value and the impedance region corresponding to the adjustable inductor.

3. The tuning method of the low-loss tuned matching network according to claim 2, characterized in that: The frequency threshold is 10 MHz.

4. The tuning method of a low-loss tuned matching network according to claim 1, wherein: The target impedance conductance value is 0.02S.

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