Radio frequency communication filter based on voltage tuning

Abstract

A radio frequency communication filter based on voltage tuning comprises an LC low-pass filter composed of a first set of parallel variable capacitance diode units, a second set of parallel variable capacitance diode units and an inductor L2, and an RC high-pass filter which is adjusted along with a tuning voltage control end VT and composed of a capacitor C2, a variable capacitance diode V17, a variable capacitance diode V18, a capacitor C4 and a resistor R2. A third group of parallel variable capacitance diode units, a fourth group of parallel variable capacitance diode units and an inductor L3 form an LC low-pass filter, and a capacitor C3, a variable capacitance diode V20, a variable capacitance diode V19, a capacitor C5 and a resistor R2 form another RC high-pass filter which is adjusted along with a tuning voltage control end VT. And the two band-pass filters are connected to form a high-selectivity and low-insertion-loss adjustable band-pass filter driven by the same controllable tuning voltage control end.

Description

Technical Field

[0001] The utility model relates to the technical field of filters, in particular to a radio frequency communication filter based on voltage tuning. Background Art

[0002] A filter is a key component for signal processing, used for signal separation and selection. However, traditional filters show insufficient flexibility in multi-band applications, especially in the frequency band of 30 MHz to 88 MHz, which covers multiple important communication and broadcast standards. Therefore, it is necessary to design a radio frequency communication filter that can achieve dynamic frequency adjustment. Summary of the Utility Model

[0003] In response to the requirements in the prior art, the utility model provides a radio frequency communication filter based on voltage tuning, aiming to achieve high selectivity of the input radio frequency signal.

[0004] The radio frequency communication filter based on voltage tuning includes a first radio frequency signal transmission end, a second radio frequency signal transmission end, and a tuning voltage control end. The first radio frequency signal transmission end is grounded successively through an inductor L2, a first group of parallel varactor diode units, and a second group of parallel varactor diode units. The negative electrodes of the first group of parallel varactor diode units and the second group of parallel varactor diode units are connected and then connected to the tuning voltage control end through a resistor R4; the common end of the inductor L2 and the first parallel varactor diode unit is grounded successively through a varactor diode V17, a varactor diode V18, and a resistor R2. A capacitor C2 and a capacitor C4 are respectively connected in parallel on the varactor diode V17 and the varactor diode V18. The common end of the varactor diode V17 and the varactor diode V18 is connected to the tuning voltage control end through a resistor R1.

[0005] The second radio frequency signal transmission end is grounded successively through an inductor L3, a third group of parallel varactor diode units, and a fourth group of parallel varactor diode units. The negative electrodes of the third group of parallel varactor diode units and the fourth group of parallel varactor diode units are connected and then connected to the tuning voltage control end through a resistor R5; the common end of the inductor L3 and the third group of parallel varactor diode units is connected to the common end of the resistor R2 and the varactor diode V18 successively through a varactor diode V20 and a varactor diode V19. A capacitor C3 and a capacitor C5 are respectively connected in parallel on the varactor diode V20 and the varactor diode V19. The common end of the varactor diode V20 and the varactor diode V19 is connected to the tuning voltage control end through a resistor R3.

[0006] Furthermore, an adjustable capacitor C6 is connected in parallel on the first group of parallel varactor diode units, and an adjustable capacitor C7 is connected in parallel on the third group of parallel varactor diode units. The adjustable capacitor C6 and the adjustable capacitor C7 are 0.1 PF to 2 PF, used to improve the matching characteristics of the LC low-pass filter and compensate the frequency bandwidth in the high-frequency band.

[0007] Furthermore, inductors L2 and L3 are both adjustable inductors.

[0008] Furthermore, the adjustment terminal of inductor L2 is connected to the first radio frequency signal transmission terminal successively through coupling inductor L1 and capacitor C1, and the adjustment terminal of inductor L3 is connected to the second radio frequency signal transmission terminal successively through coupling inductor L4 and capacitor C10.

[0009] Furthermore, the common terminal of resistor R4 and the tuning voltage control terminal is grounded through capacitor C8, and the common terminal of resistor R5 and the tuning voltage control terminal is grounded through capacitor C9.

[0010] The beneficial effects of the present utility model are as follows: By providing an RC high-pass filter and an LC low-pass filter with adjustable cut-off frequencies to form a band-pass filter, and connecting two band-pass filters to constitute an adjustable band-pass filter with high selectivity and low insertion loss driven by the same tuning voltage control terminal with controllable following. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is the circuit diagram of the present utility model;

[0012] Figure 2 is the circuit block diagram when the present utility model is in use. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0013] The following will describe the present utility model in detail with reference to the drawings. The embodiments of the present utility model will be described in detail below. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals indicate the same or similar elements or elements with the same or similar functions from beginning to end. The embodiments described below by referring to the drawings are exemplary and are only used to explain the present utility model, and should not be construed as limiting the present utility model. The orientation terms such as left, middle, right, up, and down in the embodiments of the present utility model are only relative concepts to each other or are referenced based on the normal use state of the product, and should not be considered as restrictive.

[0014] A radio frequency communication filter based on voltage tuning, such as Figure 1As shown, it includes a first radio frequency signal transmission terminal, a second radio frequency signal transmission terminal, and a tuning voltage control terminal VT. The first radio frequency signal transmission terminal is grounded successively through an inductor L2, a first group of parallel varactor diode units, and a second group of parallel varactor diode units. The cathodes of the first group of parallel varactor diode units and the second group of parallel varactor diode units are connected together and connected to the tuning voltage control terminal VT through a resistor R4. The anode of the first group of parallel varactor diode units is connected to the inductor L2, and the anode of the second group of parallel varactor diode units is grounded. The first group of parallel varactor diode units consists of parallel-connected BB639 varactor diodes V1 to V8, and the second group of parallel varactor diode units consists of parallel-connected BB639 varactor diodes V9 to V16. The first group of parallel varactor diode units, the second group of parallel varactor diode units, and the inductor L2 form an LC low-pass filter. An adjustable capacitor C6 is connected in parallel with the first group of parallel varactor diode units, and the adjustable capacitor C6 is 0.1 PF to 2 PF.

[0015] The common terminal of the inductor L2 and the first parallel varactor diode unit is grounded successively through a varactor diode V17, a varactor diode V18, and a resistor R2. A capacitor C2 and a capacitor C4 are respectively connected in parallel with the varactor diode V17 and the varactor diode V18. The common terminal of the varactor diode V17 and the varactor diode V18 is connected to the tuning voltage control terminal VT through a resistor R1. The capacitor C2, the varactor diode V17, the varactor diode V18, the capacitor C4, and the resistor R2 form an RC high-pass filter that is adjusted with the tuning voltage control terminal VT.

[0016] The second radio frequency signal transmission terminal is grounded successively through an inductor L3, a third group of parallel varactor diode units, and a fourth group of parallel varactor diode units. The cathodes of the third group of parallel varactor diode units and the fourth group of parallel varactor diode units are connected together and connected to the tuning voltage control terminal VT through a resistor R5. The anode of the third group of parallel varactor diode units is connected to the inductor L3, and the anode of the fourth group of parallel varactor diode units is grounded. The third group of parallel varactor diode units consists of parallel-connected BB639 varactor diodes V21 to V28, and the fourth group of parallel varactor diode units consists of parallel-connected BB639 varactor diodes V29 to V36. The third group of parallel varactor diode units, the fourth group of parallel varactor diode units, and the inductor L3 form an LC low-pass filter. An adjustable capacitor C7 is connected in parallel with the third group of parallel varactor diode units, and the adjustable capacitor C7 is 0.1 PF to 2 PF. Both the adjustable capacitor C6 and the adjustable capacitor C7 are used to improve the matching characteristics of the LC low-pass filter and compensate the frequency bandwidth in the high-frequency band.

[0017] The common terminal of the inductor L3 and the third group of parallel varactor diode units is sequentially connected to the common terminal of the resistor R2 and the varactor diode V18 after passing through the varactor diode V20 and the varactor diode V19. A capacitor C3 and a capacitor C5 are respectively connected in parallel to the varactor diode V20 and the varactor diode V19. The common terminal of the varactor diode V20 and the varactor diode V19 is connected to the tuning voltage control terminal VT after passing through the resistor R3; the capacitor C3, the varactor diode V20, the varactor diode V19, the capacitor C5 and the resistor R2 form another RC high-pass filter that is adjusted with the tuning voltage control terminal VT;

[0018] The RC high-pass filter and the LC low-pass filter form a band-pass filter, and the two band-pass filters are connected to form an adjustable band-pass filter driven by the same tuning voltage control terminal VT that follows and is controllable.

[0019] Among them, the inductors L2 and L3 are both adjustable inductors with a value of 183NH to 268NH, and both are main tuning inductors. The size of the inductance can be changed by adjusting the magnetic core inside the inductor, ensuring that the operating frequency of the present invention can cover the frequency band from 30MHz to 88MHz, and ensuring that the bandwidth, insertion loss and selectivity meet the requirements of radio frequency communication. One fixed terminal of the inductor L2 and one fixed terminal of the inductor L3 are grounded, and the adjustment terminals of the inductor L2 and the adjustment terminal of the inductor L3 are respectively connected to the first radio frequency signal transmission terminal and the second radio frequency signal transmission terminal. Specifically, the adjustment terminal of the inductor L2 is sequentially connected to the first radio frequency signal transmission terminal after passing through the coupling inductor L1 and the capacitor C1, and the adjustment terminal of the inductor L3 is sequentially connected to the second radio frequency signal transmission terminal after passing through the coupling inductor L4 and the capacitor C10; the coupling inductors L1 and L4 are used to adjust the impedance of the input and output terminals of the tuning filter to achieve stable and effective transmission of the input radio frequency signal; the capacitors C1 and C10 are used to block direct current and pass alternating current and match the front-end and rear-end low-noise amplifiers.

[0020] In addition, the common terminal of the resistor R4 and the tuning voltage control terminal VT is grounded after passing through the capacitor C8, and the common terminal of the resistor R5 and the tuning voltage control terminal VT is grounded after passing through the capacitor C9; the capacitors C8 and C9 are filter capacitors for the tuning voltage control terminal VT, which can reduce the influence of the 30MHz to 88MHz radio frequency signal on the tuning voltage control terminal VT and ensure the stability of the tuning voltage control terminal VT.

[0021] During operation, combined with Figure 2As shown, the first group of parallel varactor diode units, the second group of parallel varactor diode units, the third group of parallel varactor diode units, and the fourth group of parallel varactor diode units all form a varactor diode array; the digital control circuit receives the frequency command issued by the superior, reads the corresponding tuning voltage parameters in its internal memory chip, and outputs a voltage digital signal according to the timing of the analog-to-digital converter therein; the analog-to-digital converter of the tuning voltage driving circuit outputs a tuning voltage according to the voltage digital signal; after the tuning voltage control terminal VT of the present invention receives the tuning voltage, the frequency response of the filter changes.

[0022] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and the descriptions in the specification only illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A voltage-tuned radio frequency communication filter, characterized in that: It includes a first radio frequency signal transmission end, a second radio frequency signal transmission end and a tuning voltage control end. The first radio frequency signal transmission end is connected to ground via an inductor L2, a first group of parallel varactor diode units, and a second group of parallel varactor diode units in sequence. The cathodes of the first group of parallel varactor diode units and the second group of parallel varactor diode units are connected and connected to the tuning voltage control end via a resistor R4. The common end of the inductor L2 and the first parallel varactor diode unit is connected to ground via a varactor diode V17, a varactor diode V18, and a resistor R2 in sequence. Capacitors C2 and C4 are connected in parallel to the varactor diode V17 and the varactor diode V18, respectively. The common end of the varactor diode V17 and the varactor diode V18 is connected to the tuning voltage control end via a resistor R1. The second RF signal transmission end is grounded via the inductor L3, the third group of parallel varactor diode units, and the fourth group of parallel varactor diode units in sequence. The cathodes of the third group of parallel varactor diode units and the fourth group of parallel varactor diode units are connected and connected to the tuning voltage control end via the resistor R5; the common end of the inductor L3 and the third group of parallel varactor diode units is connected to the common end of the resistor R2 and the varactor diode V18 via the varactor diode V20 and the varactor diode V19 in sequence. The capacitor C3 and the capacitor C5 are connected in parallel to the varactor diode V20 and the varactor diode V19, respectively. The common end of the varactor diode V20 and the varactor diode V19 is connected to the tuning voltage control end via the resistor R3.

2. The voltage-tuned radio frequency communication filter according to claim 1, characterized in that: An adjustable capacitor C6 is connected in parallel to the first group of parallel varactor diode units, and an adjustable capacitor C7 is connected in parallel to the third group of parallel varactor diode units. The adjustable capacitors C6 and C7 are 0.1PF to 2PF and are used to improve the matching characteristics of the LC low-pass filter and compensate for the frequency bandwidth of the high frequency band.

3. The voltage-tuned radio frequency communication filter according to claim 1, characterized in that: The inductor L2 and the inductor L3 are both adjustable inductors.

4. The voltage-tuned radio frequency communication filter according to claim 3, characterized in that: The adjustment end of the inductor L2 is connected to the first RF signal transmission end through the coupling inductor L1 and the capacitor C1 in sequence, and the adjustment end of the inductor L3 is connected to the second RF signal transmission end through the coupling inductor L4 and the capacitor C10 in sequence.

5. The voltage-tuned radio frequency communication filter according to claim 1, characterized in that: The common end of the resistor R4 and the tuning voltage control end is grounded via the capacitor C8, and the common end of the resistor R5 and the tuning voltage control end is grounded via the capacitor C9.

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