Adjustable MMIC band-pass filter based on tap inductance technology

Abstract

The invention discloses an adjustable MMIC band-pass filter based on a tap inductance technology. The adjustable MMIC band-pass filter comprises a radio frequency input end, a radio frequency output end, a low-pass filter circuit and an adjustable band-pass filter circuit, wherein the low-pass filter circuit and the adjustable band-pass filter circuit are connected between the radio frequency input end and the radio frequency output end in series; the low-pass filter circuit comprises first to third capacitors and an inductor; the adjustable band-pass filter circuit comprises a first network, a second network, a third network, a fourth network, a fifth adjustable capacitor and a sixth adjustable capacitor; one end of the inductor is connected with the radio frequency input end, and the other end of the inductor is coupled with the first network; the first network and the second network are coupled through a fifth adjustable capacitor, the second network and the third network are coupled through a tap inductor, the third network and the fourth network are coupled through a sixth adjustable capacitor, and the fourth network is connected with a radio frequency output end. Compact magnetic coupling is achieved through the tap inductance technology, insertion loss and the chip area are remarkably reduced, and meanwhile the wide tuning range and high harmonic suppression are achieved.

Description

Technical Field

[0001] This invention relates to the field of bandpass filter design technology, and specifically to an adjustable MMIC bandpass filter based on tapped inductor technology. Background Technology

[0002] With the rapid evolution of applications such as 5G / 6G multi-band communication, software-defined radio, and broadband electronic warfare, RF front-ends are placing more stringent demands on bandpass filters that are "small in size, single-voltage, and continuously adjustable." Traditional implementation schemes mainly fall into four categories: 1. Switched-capacitor arrays—using CMOS / SOI switches to switch discrete capacitors to achieve frequency transitions; its disadvantages include complex control and low Q-value. 2. Q-enhanced active filters—using negative resistance transistors to offset passive component losses and obtain adjustable bandwidth; its disadvantages include introducing active noise and degrading linearity. 3. N-path filters—using the baseband-switching time-varying resistor shifting principle to achieve LO tracking filtering; its disadvantages include reliance on multiphase high-frequency clocks and poor out-of-band rejection in the high-frequency band. 4. Pure varactor direct tuning—continuously changing the reverse-biased junction capacitance with a single voltage, resulting in a simple structure; its disadvantages include the need for a large area of ​​inductor / transformer for resonator coupling, limiting integration density. The above solutions are difficult to achieve simultaneously with features such as small chip area, low control complexity, low insertion loss, and high out-of-band rejection, making it difficult to meet the requirements of higher-performance tunable filters.

[0003] Furthermore, as wireless communication systems develop towards multi-band and high-integration directions, traditional MMIC (Monolithic Microwave Integrated Circuit) filter structures face the following problems: 1. Multi-band coverage requires multiple filters, resulting in large area and complex control; 2. Adjustable filters often employ multi-voltage control, increasing system complexity; 3. Poor high-order harmonic suppression capability, making it difficult to meet the broadband suppression requirements of modern communication systems; 4. Traditional magnetic coupling structures (such as transformers and coupled inductors) have large area and high losses, which are not conducive to integration. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an adjustable MMIC bandpass filter based on tapped inductor technology to overcome the shortcomings of the prior art. This adjustable filter has the characteristics of smaller chip area, lower control complexity, lower insertion loss, and higher out-of-band rejection.

[0005] To solve the above technical problems, the present invention adopts the following technical solution:

[0006] An adjustable MMIC bandpass filter based on tapped inductor technology includes an RF input terminal, an RF output terminal, and a low-pass filter circuit and an adjustable bandpass filter circuit connected in series between the RF input terminal and the RF output terminal.

[0007] The low-pass filter circuit includes first to third capacitors and an inductor; the adjustable band-pass filter circuit includes a first network, a second network, a third network, a fourth network, a fifth adjustable capacitor, and a sixth adjustable capacitor.

[0008] One end of the inductor is connected to the RF input terminal, and the other end of the inductor is coupled to the first network.

[0009] The first and second networks are coupled through a fifth adjustable capacitor, the second and third networks are coupled through a tapped inductor, the third and fourth networks are coupled through a sixth adjustable capacitor, and the fourth network is connected to the RF output terminal.

[0010] Furthermore, one end of the inductor is connected to one end of the first capacitor, one end of the third capacitor, and the RF input terminal, respectively. The other end of the inductor is connected to one end of the second capacitor, the other end of the third capacitor, and the first network, respectively. The other end of the first capacitor is connected to the other end of the second capacitor and grounded.

[0011] Furthermore, the first network includes a first adjustable capacitor and a first tap inductor, the second network includes a third adjustable capacitor and a third tap inductor, the third network includes a fourth adjustable capacitor and a fourth tap inductor, and the fourth network includes a second adjustable capacitor and a second tap inductor.

[0012] One end of the first adjustable capacitor is connected to one end of the second, third, and fourth adjustable capacitors and grounded. The other end of the first adjustable capacitor is connected to one end of the first tapped inductor and one end of the fifth adjustable capacitor. The other end of the third adjustable capacitor is connected to one end of the third tapped inductor and one end of the fifth adjustable capacitor. The other end of the fourth adjustable capacitor is connected to one end of the fourth tapped inductor and one end of the sixth adjustable capacitor. The other end of the second adjustable capacitor is connected to one end of the second tapped inductor and one end of the sixth adjustable capacitor. The other end of the first tapped inductor is connected to the other ends of the second, third, and fourth tapped inductors and grounded. The tap of the third tapped inductor is connected to the tap of the fourth tapped inductor.

[0013] Furthermore, the other end of the inductor is connected to the tap of the first tap inductor.

[0014] Furthermore, the tap of the second tap inductor is connected to the RF output terminal.

[0015] Furthermore, the adjustable capacitor includes a first varactor diode, a second varactor diode, a first resistor, and a voltage control port;

[0016] The positive terminal of the first varactor diode is used as one end of the adjustable capacitor. The negative terminal of the first varactor diode is connected to the negative terminal of the second varactor diode. The positive terminal of the second varactor diode is used as the other end of the adjustable capacitor. One end of the first resistor is connected to the negative terminal of the first varactor diode. The other end of the first resistor is connected to the voltage control port.

[0017] The voltage control ports of the first to sixth adjustable capacitors are connected to the same control voltage.

[0018] Furthermore, the first tap inductor L1 is coupled to the third tap inductor L3, and the second tap inductor L2 is coupled to the fourth tap inductor L4. The coupling coefficients at the two locations may be the same or different, and the coupling coefficients can be 0. By adjusting the coupling coefficients at the two locations, better impedance matching and circuit performance can be achieved.

[0019] Compared with the prior art, the present invention, employing the above technical solution, has the following technical effects:

[0020] 1. This invention achieves magnetic coupling between resonators through tapped inductor technology, reducing area and loss.

[0021] 2. This invention adopts an architecture that combines a low-pass filter and an adjustable filter, which meets the requirements for high-order harmonic suppression.

[0022] 3. This invention has a wide tuning range, uses only a single power supply for control, and achieves zero-power tuning, making it suitable for low-power systems. Attached Figure Description

[0023] Figure 1 This is an overall structural diagram of the present invention.

[0024] Figure 2 This is the internal circuit diagram of the adjustable capacitor in this invention.

[0025] Figure 3 This is a symmetrical split circuit diagram and an equivalent circuit diagram of the second and third networks in this invention.

[0026] Figure 4 This is the layout of the tapped inductor in this invention.

[0027] Figure 5 This is a graph showing the bandwidth response test results in an embodiment of the present invention.

[0028] Figure 6 This is a graph showing the out-of-band suppression test results in an embodiment of the present invention. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0030] To achieve the above objectives, this invention proposes an adjustable MMIC bandpass filter based on tapped inductor technology, such as... Figure 1 As shown, the details are as follows:

[0031] It includes an RF input terminal, an RF output terminal, and a low-pass filter circuit and an adjustable band-pass filter circuit connected in series between the RF input terminal and the RF output terminal.

[0032] The low-pass filter circuit includes the first to third capacitors C. L1 ~C L3 and inductor L L1 Inductance L L1 One end is connected to the first capacitor C L1 One end, the third capacitor C L3 One end, RF input terminal in Connection, inductor L L1 The other end is connected to the second capacitor C. L2 One end, the third capacitor C L3 The other end is connected to an adjustable bandpass filter circuit, with the first capacitor C L1 The other end is connected to the second capacitor C L2 The other end is connected to and grounded; the low-pass filter circuit described above can provide better high-frequency suppression and impedance matching, and improve out-of-band suppression performance and return loss.

[0033] The adjustable bandpass filter circuit includes a first network, a second network, a third network, a fourth network, a fifth adjustable capacitor C5, and a sixth adjustable capacitor C6. The first and second networks are coupled through the fifth adjustable capacitor C5, the second and third networks are coupled through a tapped inductor, and the third and fourth networks are coupled through the sixth adjustable capacitor C6. The fourth network is connected to the RF output terminal. out Connection; different networks are coupled alternately by capacitor-inductor-capacitor, which can achieve high out-of-band rejection at frequencies outside the filter passband.

[0034] The first network includes a first adjustable capacitor C1 and a first tap inductor L1; the second network includes a third adjustable capacitor C3 and a third tap inductor L3; the third network includes a fourth adjustable capacitor C4 and a fourth tap inductor L4; and the fourth network includes a second adjustable capacitor C2 and a second tap inductor L2.

[0035] One end of the first adjustable capacitor C1 is connected to one end of the second adjustable capacitor C2, one end of the third adjustable capacitor C3, and one end of the fourth adjustable capacitor C4, and grounded. The other end of the first adjustable capacitor C1 is connected to one end of the first tapped inductor L1 and one end of the fifth adjustable capacitor C5. The other end of the third adjustable capacitor C3 is connected to one end of the third tapped inductor L3 and the other end of the fifth adjustable capacitor C5. The other end of the fourth adjustable capacitor C4 is connected to one end of the fourth tapped inductor L4 and one end of the sixth adjustable capacitor C6. The other end of the second adjustable capacitor C2 is connected to one end of the second tapped inductor L2 and the other end of the sixth adjustable capacitor C6. The other end of the first tapped inductor L1 is connected to the other ends of the second tapped inductor L2, the third tapped inductor L3, and the fourth tapped inductor L4, and grounded. In the fourth network, the tapped end of the second tapped inductor L2 is connected to the RF output terminal RF. out The third tap inductor L3 is connected to the fourth tap inductor L4.

[0036] Inductor L L1 The other end is connected to the tap end of the first tap inductor L1 of the first network in the adjustable bandpass filter circuit.

[0037] The first tap inductor L1 is coupled to the third tap inductor L3, and the second tap inductor L2 is coupled to the fourth tap inductor L4. The coupling coefficients at the two points may be the same or different, and the coupling coefficients can be 0. By adjusting the coupling coefficients at the two points, better impedance matching and circuit performance can be achieved.

[0038] Figure 2 This is the internal circuit diagram of an adjustable capacitor, which includes a first varactor diode C. v1 Second varactor diode C v2 The first resistor R1 and the voltage control port V con First varactor diode C v1 The positive terminal is used as one end of the adjustable capacitor, and the first varactor diode C v1 The negative terminal and the second varactor diode C v2 The negative terminal is connected to the second varactor diode C. v2 The positive terminal is used as the other end of the adjustable capacitor, and one end of the first resistor R1 is connected to the first varactor diode C. v1 The negative terminal is connected, and the other end of the first resistor R1 is connected to the voltage control port V. con Connection; Voltage control port V of the first to sixth adjustable capacitors C1 to C6 con By connecting to the same control voltage, all varactor diodes are controlled simultaneously and all varactor diodes are reverse biased, thus achieving the tuning of the filter passband.

[0039] Figure 3This is the symmetrical split circuit diagram and equivalent circuit diagram of the second and third networks. The symmetrical split circuit diagram includes the first split inductor L. t1 Second split inductor L t2 First split capacitor C t and tap input port Z in_t First split capacitor C t One end of the capacitor is grounded, and the first split capacitor C t The other end is connected to the first split inductor L t1 One end is connected to the first split inductor L t1 The other end is connected to the second split inductor L t2 One end is connected and used as an inductor tap to the tap input port, the second split inductor L t2 The other end is grounded.

[0040] The symmetrically split circuit is equivalently converted into an equivalent circuit through parity mode analysis and circuit transformation. The equivalent circuit includes the first equivalent inductance L. e1 Second equivalent inductance L e2 First equivalent capacitance C e and equivalent input port Z in_e First equivalent capacitance C e One end is grounded, and the first equivalent capacitance C e The other end is connected to the first equivalent inductance L. e1 One end, the second equivalent inductance L e2 One end is connected, the second equivalent inductance L e2 The other end is grounded, and the first equivalent inductance L e1 The other end is connected to the equivalent input port. The equivalent formulas for the equivalent inductance and equivalent capacitance are:

[0041] C e =C t (L t1 +L t2 ) 2 / L t2 ;

[0042] L e1 =L t1 +L t1 2 / L t2 ;

[0043] L e2 =L t2 2 / (L t1 +L t2 ).

[0044] As can be seen from the equivalent formula, magnetic coupling between resonant units can be achieved using tapped inductor technology. By selecting appropriate inductance values ​​and tap positions, coupling between resonant networks can be achieved using only one inductor, eliminating the need for traditional transformers or inductor coupling structures (such as the first equivalent inductance L). e1 This reduces chip area and losses, resulting in better chip performance.

[0045] Figure 4 The layout of the tapped inductor shows that the main body of the tapped inductor consists of a spiral wound coil. One end of the coil is connected to the layout ground, and the other end is connected to the circuit. The tap is connected to the bottom metal layer (the coil portion can be considered as the top metal layer) through a metal via, and then outputs through the bottom metal layer as the tap terminal connected to the circuit. This design of the tapped inductor eliminates the need for additional coupling inductors or transformers while achieving coupling between different resonant networks, which is beneficial for reducing chip area and chip losses.

[0046] Figure 5 The graph shows the bandwidth response test results of the tunable MMIC bandpass filter proposed in this invention. Figure 5 As can be seen from the present invention, the adjustable MMIC bandpass filter can achieve tuning of the filter passband. Within the tuning voltage range, the tuning range of the center frequency of the filter passband can reach more than 60%, the total coverage bandwidth is close to 100%, and the in-band insertion loss is as low as about 5dB.

[0047] Figure 6 The graph shows the out-of-band rejection test results of the tunable MMIC bandpass filter proposed in this invention. Figure 6 As can be seen from the present invention, the adjustable MMIC bandpass filter can achieve harmonic suppression of >45 dB at high frequencies, and the suppression bandwidth is >17 times the center frequency, which meets the requirements for high-order harmonic suppression.

[0048] This invention employs an architecture that cascades a low-pass filter with a tapped inductor-based tunable filter. However, this is not necessary. To achieve specific performance targets, the tapped inductor-based tunable filter can be configured as a standalone circuit or cascaded with a low-pass filter, a high-pass filter, a band-pass filter, or a combination thereof.

[0049] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An adjustable MMIC bandpass filter based on tapped inductor technology, characterized in that, It includes an RF input terminal, an RF output terminal, and a low-pass filter circuit and an adjustable band-pass filter circuit connected in series between the RF input terminal and the RF output terminal; The low-pass filter circuit includes the first to third capacitors C. L1 ~C L3 and inductor L L1 The adjustable bandpass filter circuit includes a first network, a second network, a third network, a fourth network, a fifth adjustable capacitor C5, and a sixth adjustable capacitor C6. Inductor L L1 One end is connected to the RF input terminal, and the inductor L L1 The other end is coupled to the first network; The first and second networks are coupled through the fifth adjustable capacitor C5, the second and third networks are coupled through a tapped inductor, the third and fourth networks are coupled through the sixth adjustable capacitor C6, and the fourth network is connected to the RF output terminal.

2. The adjustable MMIC bandpass filter based on tapped inductor technology according to claim 1, characterized in that, Inductor L L1 One end is connected to the first capacitor C L1 One end, the third capacitor C L3 One end is connected to the RF input terminal, and the inductor L L1 The other end is connected to the second capacitor C. L2 One end, the third capacitor C L3 The other end, the first network connection, the first capacitor C L1 The other end is connected to the second capacitor C L2 The other end is connected to and grounded.

3. The adjustable MMIC bandpass filter based on tapped inductor technology according to claim 1, characterized in that, The first network includes a first adjustable capacitor C1 and a first tap inductor L1; the second network includes a third adjustable capacitor C3 and a third tap inductor L3; the third network includes a fourth adjustable capacitor C4 and a fourth tap inductor L4; and the fourth network includes a second adjustable capacitor C2 and a second tap inductor L2. One end of the first adjustable capacitor C1 is connected to one end of the second adjustable capacitor C2, one end of the third adjustable capacitor C3, and one end of the fourth adjustable capacitor C4, and grounded. The other end of the first adjustable capacitor C1 is connected to one end of the first tap inductor L1 and one end of the fifth adjustable capacitor C5, respectively. The other end of the third adjustable capacitor C3 is connected to one end of the third tap inductor L3 and the other end of the fifth adjustable capacitor C5, respectively. The other end of the fourth adjustable capacitor C4 is connected to one end of the fourth tap inductor L4 and one end of the sixth adjustable capacitor C6, respectively. The other end of the second adjustable capacitor C2 is connected to one end of the second tap inductor L2 and the other end of the sixth adjustable capacitor C6, respectively. The other end of the first tap inductor L1 is connected to the other ends of the second tap inductor L2, the third tap inductor L3, and the fourth tap inductor L4, and grounded. The tap of the third tap inductor L3 is connected to the tap of the fourth tap inductor L4.

4. The adjustable MMIC bandpass filter based on tapped inductor technology according to claim 3, characterized in that, Inductor L L1 The other end is connected to the tap end of the first tap inductor L1.

5. The adjustable MMIC bandpass filter based on tapped inductor technology according to claim 3, characterized in that, The tap of the second tap inductor L2 is connected to the RF output terminal.

6. The adjustable MMIC bandpass filter based on tapped inductor technology according to claim 3, characterized in that, The adjustable capacitor includes a first varactor diode C. v1 Second varactor diode C v2 The first resistor R1 and the voltage control port V con ; First varactor diode C v1 The positive terminal is used as one end of the adjustable capacitor, and the first varactor diode C v1 The negative terminal and the second varactor diode C v2 The negative terminal is connected to the second varactor diode C. v2 The positive terminal is used as the other end of the adjustable capacitor, and one end of the first resistor R1 is connected to the first varactor diode C. v1 The negative terminal is connected, and the other end of the first resistor R1 is connected to the voltage control port V. con connect; The voltage control port V of the first to sixth adjustable capacitors C1 to C6 con Connected to the same control voltage.

7. The adjustable MMIC bandpass filter based on tapped inductor technology according to claim 3, characterized in that, The first tap inductor L1 is coupled to the third tap inductor L3, and the second tap inductor L2 is coupled to the fourth tap inductor L4. The coupling coefficients at the two taps may be the same or different, and the coupling coefficients can be 0.

Images