Switch filter circuit based on PIN tube

Abstract

The switch filter circuit based on the PIN tubes comprises a blocking capacitor C1, a filter capacitor C2, a feed network B1, a feed network B2, a PIN tube D1, a PIN tube D2, a PIN tube D3, N low-pass LC filter units and M high-pass LC filter units, N is larger than or equal to 1, and M is larger than or equal to 1. One end of the C1 is connected with a low-frequency input connector J1, a positive electrode of the D1 is connected with a control voltage VDD1 through the B1, a negative electrode of the D1 is connected with a positive electrode of the D2, and a negative electrode of the D2 is grounded; one end of the C2 is connected with an output connector J3, the negative electrode of the D3 is grounded, and the positive electrode of the D3 is connected with a control voltage VDD2 through the B2; the first low-pass LC filtering unit and the first high-pass LC filtering unit share the same filtering inductor L2 and the same filtering capacitor C5, one end of the L2 is connected with the positive electrode of the D2, the other end of the L2 is connected with the other end of the C2, one end of the C5 is connected with the positive electrode, and the other end of the C5 is connected with the output connector J3; filtering and switching integration is achieved, low-frequency and high-frequency gating is conducted through a PIN tube, and the circuit is simple and easy to miniaturize.

Description

Technical Field

[0001] This application relates to the field of radio frequency switching and filtering technology, specifically to a switching and filtering circuit based on a PIN diode. Background Technology

[0002] Radio frequency switches and filters are among the most common components in various systems within the modern radio frequency and microwave field. They come in many varieties, but are generally presented as independent devices, such as... Figure 1 The traditional switching filter circuit shown consists of separate switching devices and filters. J1 is the low-frequency input port, J2 is the high-frequency input port, J3 is the output port, F1 is the low-frequency filter, F2 is the high-frequency filter, and SW is a single-pole double-throw switch. F1 and F2 can filter out stray signals other than the desired signal. When a low-frequency signal is needed, switch SW switches to the low-frequency branch; when a high-frequency signal is needed, switch SW switches to the high-frequency branch. Due to the complex structure, high cost, and large size of this system, it is necessary to improve it. Summary of the Invention

[0003] To address the shortcomings of the aforementioned prior art, this application provides a PIN diode-based switching filter circuit that integrates filtering and switching, using the PIN diode as a switch to select low-frequency and high-frequency signals, and simplifies the circuit structure for easy miniaturization.

[0004] To achieve the above objectives, the present invention employs the following techniques: A PIN diode-based switching filter circuit includes a DC blocking capacitor C1, a filter capacitor C2, a power supply network B1, a power supply network B2, PIN diodes D1, D2, and D3, N low-pass LC filter units and M high-pass LC filter units, where N≥1 and M≥1. One end of the DC blocking capacitor C1 is connected to the low-frequency input connector J1, and the positive terminal of the PIN diode D1 is connected to the control voltage through the power supply network B1. V DD1 The negative terminal of PIN diode D1 is connected to the positive terminal of PIN diode D2, and the negative terminal of PIN diode D2 is connected to ground. One end of the filter capacitor C2 is connected to the output connector J3, the negative terminal of the PIN diode D3 is grounded, and the positive terminal of the PIN diode D3 is connected to the control voltage through the feed network B2. V DD2 ; The first low-pass LC filter unit and the first high-pass LC filter unit share the same filter inductor L2 and the same filter capacitor C5. One end of the filter inductor L2 is connected to the positive terminal of the PIN diode D2, and the other end is connected to the other end of the filter capacitor C2. One end of the filter capacitor C5 is connected to the positive terminal of the PIN diode D3, and the other end is connected to the output connector J3. When N=1, the other end of the DC blocking capacitor C1 is connected to the positive terminal of the PIN diode D2; when N≥2, the remaining low-pass LC filter units are connected in series and connected between the other end of the DC blocking capacitor C1 and the positive terminal of the PIN diode D2. The remaining low-pass LC filter units all include a filter inductor L1 connected in series and a filter capacitor C3 with one end connected to the filter inductor L1 and the other end grounded. When M=1, the positive terminal of PIN diode D3 is connected to the high-frequency input connector J2; when M=2, the second high-pass LC filter unit includes a filter capacitor C4 connected in series between the high-frequency input connector J2 and the positive terminal of PIN diode D3, and the power supply network B2; when M≥3, there are other high-pass LC filter units in addition to those in M=2. These other high-pass LC filter units are connected in series and parallel between the high-frequency input connector J2 and the filter capacitor C4. Each of these other high-pass LC filter units includes a filter capacitor C6 connected in series and a filter inductor L3 with one end connected to the filter capacitor C6 and the other end grounded.

[0005] Feeder network B2 is used for control voltage V DD2 The DC voltage supplied to PIN diode D3 is filtered and used as a filter inductor and filter capacitor C4 in the high-frequency branch with M≥2 to form the second high-pass LC filter unit.

[0006] Furthermore, the switching filter circuit simultaneously forms a low-frequency branch and a high-frequency branch, which are respectively an N-order LC low-pass filter and an M-order LC high-pass filter. The low-frequency branch includes a low-frequency input connector J1, a DC blocking capacitor C1, N low-pass LC filter units, a filter capacitor C2, a PIN diode D3, and an output connector J3; The high-frequency branch includes a high-frequency input connector J2, M high-pass LC filter units, filter capacitor C2, PIN diode D2, and output connector J3.

[0007] Furthermore, by changing the control voltage V DD1 and control voltage V DD2 To enable selection between low-frequency and high-frequency branches: When control voltage V DD1 The first positive voltage, control voltage V DD2 When the voltage is the first negative voltage, PIN diodes D1 and D2 are turned on, PIN diode D3 is turned off, the high-frequency branch is turned on, the low-frequency branch is turned off, and the output connector J3 outputs a high-frequency signal. When control voltage V DD1 The second negative voltage, control voltage V DD2When the voltage is the second positive voltage, PIN diodes D1 and D2 are cut off, PIN diode D3 is turned on, the high-frequency branch is cut off, the low-frequency branch is turned on, and the output connector J3 outputs a low-frequency signal.

[0008] Furthermore, the first positive voltage can be equal to the second positive voltage, and the first negative voltage can be equal to the second negative voltage.

[0009] Furthermore, the linearity of the circuit can be adjusted by adjusting one or more of the first positive voltage, the first negative voltage, the second positive voltage, and the second negative voltage, with the adjustment range determined so that the voltage applied to both ends of each PIN diode does not exceed the reverse breakdown voltage.

[0010] Furthermore, by adjusting the values ​​of the corresponding filter capacitor and / or the corresponding filter inductor, the cutoff frequency of the LC low-pass filter and / or the LC high-pass filter can be adjusted.

[0011] Furthermore, by setting N and M respectively to adjust the order of the LC low-pass filter and the LC high-pass filter, the out-of-band suppression can be adjusted.

[0012] The beneficial effects of this invention are as follows: 1. The integrated design of the filter circuit and the switching circuit makes the circuit structure simpler and easier to miniaturize; and by using a PIN diode as a switch, the linearity of the circuit is greatly improved. 2. Filter capacitors C2 and C5, and filter inductor L2 participate in both the low-frequency and high-frequency branches, simplifying the circuit structure; the power supply network B2 is used not only for the control voltage V DD2 The DC voltage supplied to PIN diode D3 is filtered, and it also acts as a filter inductor in high-frequency branches of second order and above, further simplifying the circuit structure. 3. The frequency is adjustable. By adjusting the filter capacitor and filter inductor in the circuit, the cutoff frequency of the low-pass and high-pass branches can be achieved. 4. The out-of-band rejection is adjustable. By adjusting the order of the LC filter circuit, filters with different out-of-band rejection requirements can be achieved. Attached Figure Description

[0013] Figure 1 It is a schematic diagram of a traditional switching filter circuit.

[0014] Figure 2 This is a circuit example of a switching filter circuit in this application where the low-frequency branch is first-order.

[0015] Figure 3 This is a circuit example of a switching filter circuit in this application where the high-frequency branch is first-order.

[0016] Figure 4This is a circuit example of a switching filter circuit in this application where the low-frequency branch is second-order.

[0017] Figure 5 This is a circuit example of a switching filter circuit in this application where the high-frequency branch is second-order.

[0018] Figure 6 This is a circuit example of a switching filter circuit in this application where the low-frequency branch is third-order.

[0019] Figure 7 This is a circuit example of a switching filter circuit in this application where the high-frequency branch is third-order. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the implementation methods of the present invention will be described in detail below with reference to the accompanying drawings. However, the embodiments described in this invention are only some embodiments of the present invention, and not all embodiments.

[0021] This application provides a PIN diode-based switching filter circuit, such as... Figures 2-7 As shown, the system includes a DC blocking capacitor C1, a filter capacitor C2, a power supply network B1, a power supply network B2, PIN diodes D1, D2, and D3, N low-pass LC filter units, and M high-pass LC filter units, where N ≥ 1 and M ≥ 1. One end of the DC blocking capacitor C1 is connected to the low-frequency input connector J1, and the positive terminal of the PIN diode D1 is connected to the control voltage through the power supply network B1. V DD1 The negative terminal of PIN diode D1 is connected to the positive terminal of PIN diode D2, and the negative terminal of PIN diode D2 is connected to ground; one end of filter capacitor C2 is connected to output connector J3, the negative terminal of PIN diode D3 is grounded, and the positive terminal of PIN diode D3 is connected to the control voltage through the feed network B2. V DD2 Feeder networks B1 and B2 are used to control the voltage. V DD1 and control voltage V DD2 Perform filtering.

[0022] The first low-pass LC filter unit and the first high-pass LC filter unit share the same filter inductor L2 and the same filter capacitor C5. One end of the filter inductor L2 is connected to the positive terminal of the PIN diode D2, and the other end is connected to the other end of the filter capacitor C2. One end of the filter capacitor C5 is connected to the positive terminal of the PIN diode D3, and the other end is connected to the output connector J3.

[0023] The switching filter circuit simultaneously forms a low-frequency branch and a high-frequency branch, which are an N-order LC low-pass filter and an M-order LC high-pass filter, respectively. The low-frequency branch includes a low-frequency input connector J1, a DC blocking capacitor C1, N low-pass LC filter units, a filter capacitor C2, a PIN diode D3, and an output connector J3. The high-frequency branch includes a high-frequency input connector J2, M high-pass LC filter units, a filter capacitor C2, a PIN diode D2, and an output connector J3.

[0024] By changing the control voltage V DD1 and control voltage V DD2 To achieve channel switching between low-frequency and high-frequency branches: when the control voltage... V DD1 The first positive voltage, such as +5V, and the control voltage V DD2 When the first negative voltage is -20V, PIN diodes D1 and D2 are turned on, PIN diode D3 is turned off, the high-frequency branch is turned on, the low-frequency branch is turned off, and the output connector J3 outputs a high-frequency signal; when the control voltage... V DD1 It is the second negative voltage, for example -20V, and the control voltage V DD2 When the second positive voltage is applied, such as +5V, PIN diodes D1 and D2 are cut off, PIN diode D3 is turned on, the high-frequency branch is cut off, the low-frequency branch is turned on, and the output connector J3 outputs a low-frequency signal.

[0025] Specifically, such as Figure 2 As shown, when N=1, the low-frequency branch is a first-order LC low-pass filter. The other end of the DC blocking capacitor C1 is connected to the positive terminal of the PIN diode D2. Here, the filter inductor L2 and the filter capacitor C5 (when the low-frequency branch is on, the filter capacitor C5 is grounded through the PIN diode D3) constitute the first low-pass LC filter unit.

[0026] like Figure 4 and Figure 6 As shown, when N≥2, in addition to the first low-pass LC filter unit, there are other low-pass LC filter units. These remaining low-pass LC filter units are connected in series and parallel between the other end of the DC blocking capacitor C1 and the positive terminal of the PIN diode D2. Each of these remaining low-pass LC filter units includes a filter inductor L1 connected in series and a filter capacitor C3 with one end connected to the filter inductor L1 and the other end grounded. Wherein, as... Figure 4 The diagram shows an example of a second-order LC low-pass filter in the low-frequency branch when N=2. In addition to the first-order filter when N=1, it also includes a filter inductor L1 and a filter capacitor C3. The filter inductor L1 is connected in series between the filter capacitor C1 and the positive terminal of the PIN diode D2. One end of the filter capacitor C3 is connected to the positive terminal of the PIN diode D2, and the other end is grounded. As shown... Figure 6 The diagram shows an example of a second-order LC low-pass filter in the low-frequency branch when N=3. In addition to the first-order filter (N=1), it includes two sets of filter inductors L1 and filter capacitors C3. The two filter inductors L1 are connected in series between the filter capacitor C1 and the positive terminal of the PIN diode D2. One end of one filter capacitor C3 is connected to the positive terminal of the PIN diode D2, and the other end is grounded. The other filter capacitor C3 is connected between the two filter inductors L1, and the other end is grounded. This process continues until N is greater than 3, at which point the number of filter inductors L1 and filter capacitors C3 is increased. Therefore, by setting different values ​​of N, the order of the LC low-pass filter can be adjusted, thereby achieving adjustment of out-of-band rejection.

[0027] Specifically, such as Figure 3 As shown, when M=1, the high-frequency branch is a first-order LC high-pass filter. The positive terminal of PIN diode D3 is connected to the high-frequency input connector J2. Here, the filter capacitor C5 and the filter inductor L2 (when the high-frequency branch is on, the filter inductor L2 is grounded through PIN diode D2) constitute the first high-pass LC filter unit.

[0028] like Figure 5 The example shown is a second-order LC high-pass filter in the high-frequency branch when M=2. In addition to the first low-pass LC filter unit, there is a second high-pass LC filter unit. The second high-pass LC filter unit includes a filter capacitor C4 connected in series between the high-frequency input connector J2 and the positive terminal of the PIN tube D3 and the power supply network B2. At this time, the power supply network B2 is also used as a filter inductor.

[0029] refer to Figure 7 For example, when M≥3, in addition to the above when M=2, there are other high-pass LC filter units. These other high-pass LC filter units are connected in series and parallel between the high-frequency input connector J2 and the filter capacitor C4. Each of these other high-pass LC filter units includes a filter capacitor C6 connected in series and a filter inductor L3 with one end connected to the filter capacitor C6 and the other end grounded. Figure 7 The example shown is a third-order LC high-pass filter in the high-frequency branch when M=3. Filter capacitor C6 is connected between the high-frequency input connector J2 and filter capacitor C4. One end of filter inductor L3 is connected between filter capacitors C6 and C4, and the other end is grounded. Similarly, when M is greater than 3, additional series-connected high-pass LC filter units (i.e., additional filter capacitors C6 and L3) are added. By setting different values ​​for M, the order of the LC high-pass filter can be adjusted, thereby adjusting the out-of-band rejection.

[0030] In practice, the linearity of the circuit can be adjusted by changing the value of the control voltage, but it is necessary to ensure that the voltage applied to the two ends of the PIN diode does not exceed its reverse breakdown voltage.

[0031] In practice, the cutoff frequencies of the LC low-pass filter and the LC high-pass filter are adjusted by changing the values ​​of each filter capacitor and each filter inductor.

[0032] The switching filter circuit in this embodiment achieves a low-pass branch frequency of 9kHz~40MHz and a high-pass branch frequency of 40MHz~6GHz by controlling the voltage. V DD1 and control voltage V DD2 Controlling the on and off states of PIN diodes (D1, D2) and (D3) enables channel switching between low-pass and high-pass branches.

[0033] The switching filter circuit in this embodiment has a 1dB compression point > 30dBm, a switching time of 500ns, a frequency range of 9KHz~6GHz, and an insertion loss of < 1.2dB, with superior performance indicators.

[0034] The above description is only a preferred embodiment of this application and is not intended to limit this application. Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application.

Claims

1. A switching filter circuit based on a PIN diode, characterized in that, It includes a DC blocking capacitor C1, a filter capacitor C2, a power supply network B1, a power supply network B2, a PIN diode D1, a PIN diode D2, a PIN diode D3, N low-pass LC filter units and M high-pass LC filter units, where N≥1 and M≥1; One end of the DC blocking capacitor C1 is connected to the low-frequency input connector J1, and the positive terminal of the PIN diode D1 is connected to the control voltage through the power supply network B1. V DD1 The negative terminal of PIN diode D1 is connected to the positive terminal of PIN diode D2, and the negative terminal of PIN diode D2 is connected to ground. One end of the filter capacitor C2 is connected to the output connector J3, the negative terminal of the PIN diode D3 is grounded, and the positive terminal of the PIN diode D3 is connected to the control voltage through the feed network B2. V DD2 ; The first low-pass LC filter unit and the first high-pass LC filter unit share the same filter inductor L2 and the same filter capacitor C5. One end of the filter inductor L2 is connected to the positive terminal of the PIN diode D2, and the other end is connected to the other end of the filter capacitor C2. One end of the filter capacitor C5 is connected to the positive terminal of the PIN diode D3, and the other end is connected to the output connector J3. When N=1, the other end of the DC blocking capacitor C1 is connected to the positive terminal of the PIN diode D2; when N≥2, the remaining low-pass LC filter units are connected in series and connected between the other end of the DC blocking capacitor C1 and the positive terminal of the PIN diode D2. The remaining low-pass LC filter units all include a filter inductor L1 connected in series and a filter capacitor C3 with one end connected to the filter inductor L1 and the other end grounded. When M=1, the positive terminal of PIN diode D3 is connected to the high-frequency input connector J2; when M=2, the second high-pass LC filter unit includes a filter capacitor C4 connected in series between the high-frequency input connector J2 and the positive terminal of PIN diode D3, and the power supply network B2; when M≥3, there are other high-pass LC filter units in addition to those in M=2. These other high-pass LC filter units are connected in series and parallel between the high-frequency input connector J2 and the filter capacitor C4. Each of these other high-pass LC filter units includes a filter capacitor C6 connected in series and a filter inductor L3 with one end connected to the filter capacitor C6 and the other end grounded.

2. The PIN diode-based switching filter circuit according to claim 1, characterized in that, The switching filter circuit simultaneously forms a low-frequency branch and a high-frequency branch, which are respectively an N-order LC low-pass filter and an M-order LC high-pass filter. The low-frequency branch includes a low-frequency input connector J1, a DC blocking capacitor C1, N low-pass LC filter units, a filter capacitor C2, a PIN diode D3, and an output connector J3; The high-frequency branch includes a high-frequency input connector J2, M high-pass LC filter units, filter capacitor C2, PIN diode D2, and output connector J3.

3. The PIN diode-based switching filter circuit according to claim 2, characterized in that, By changing the control voltage V DD1 and control voltage V DD2 To enable selection between low-frequency and high-frequency branches: When control voltage V DD1 The first positive voltage, control voltage V DD2 When the voltage is the first negative voltage, PIN diodes D1 and D2 are turned on, PIN diode D3 is turned off, the high-frequency branch is turned on, the low-frequency branch is turned off, and the output connector J3 outputs a high-frequency signal. When control voltage V DD1 The second negative voltage, control voltage V DD2 When the voltage is the second positive voltage, PIN diodes D1 and D2 are cut off, PIN diode D3 is turned on, the high-frequency branch is cut off, the low-frequency branch is turned on, and the output connector J3 outputs a low-frequency signal.

4. The PIN diode-based switching filter circuit according to claim 3, characterized in that, The first positive voltage equals the second positive voltage, and the first negative voltage equals the second negative voltage.

5. The PIN diode-based switching filter circuit according to claim 3, characterized in that, The linearity of the circuit can be adjusted by adjusting one or more of the first positive voltage, the first negative voltage, the second positive voltage, and the second negative voltage. The adjustment range is based on the fact that the voltage applied to both ends of each PIN tube does not exceed the reverse breakdown voltage.

6. The PIN diode-based switching filter circuit according to claim 2, characterized in that, The cutoff frequency of the LC low-pass filter and / or LC high-pass filter can be adjusted by adjusting the values ​​of the corresponding filter capacitor and / or the corresponding filter inductor.

7. The PIN diode-based switching filter circuit according to claim 2, characterized in that, The out-of-band rejection can be adjusted by setting N and M to change the order of the LC low-pass filter and the LC high-pass filter, respectively.

8. The PIN diode-based switching filter circuit according to claim 2, characterized in that, Feeder network B2 is used for control voltage V DD2 The DC voltage supplied to PIN diode D3 is filtered and used as a filter inductor and filter capacitor C4 in the high-frequency branch with M≥2 to form the second high-pass LC filter unit.

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