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Tunable bandpass filter

A filter and band tuning technology, which is applied in the field of filters, can solve the problems of large loss, inability to adjust the center frequency and bandwidth of the passband at the same time, and low Q value of the varactor.

Inactive Publication Date: 2009-10-28
INST OF MICROELECTRONICS CHINESE ACAD OF SCI
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Problems solved by technology

However, due to the low Q value of the varactor, the loss in the passband of the tunable BPFs is large
[0004] The basic requirement of the existing adjustable BPFs design is to fix the shape of the filter response curve and the passband width, and adjust the center frequency under this premise, but the center frequency and frequency bandwidth of the passband cannot be adjusted at the same time

Method used

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Embodiment Construction

[0021] In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0022] At present, the method of forming a left-handed material by a transmission line with periodic load series capacitance and parallel inductance has been proposed. Because the electric field strength E, magnetic field strength H and wave vector k form a left-handed law, it is called a left-handed material nonlinear transmission line (LH_NLTL). , H, and k form a right-handed material nonlinear transmission line (RH_NLTL).

[0023] like figure 1 As shown, two series inductors and a parallel varactor form a right-hand nonlinear transmission line (RH_NLTL). It exhibits low-pass filter characteristics such as figure 2 shown. image 3 is a schematic diagram of a left-hand nonlinear transmission line (LH_NLTL), which con...

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Abstract

The invention discloses a tunable bandpass filter, which adopts a method of the combination of left-handed and right-handed non-linear transmission lines, wherein the left-handed non-linear transmission line consists of a series varactor and a shunt inductor, and has high-pass characteristic; and the right-handed non-linear transmission line consists of a series inductor and parallel varactor, and has low-pass characteristic. The capacitances of the varactors are changed by controlling the bias voltages of the varactors of the left-handed and right-handed non-linear transmission lines so as to adjust lower and upper side frequencies of the bandpass filter respectively.

Description

technical field [0001] The invention relates to the filter field, in particular to an adjustable band-pass filter. Background technique [0002] In modern multimode multiband communication systems, tunable bandpass filters (BPFs) are key components. Most tunable filters are classified according to mechanical tunable, magnetically tuned, and electric tuned. The electrically adjustable bandpass filter is more popular than the other two because of its fast adjustment speed, wide adjustable range, and compact size. [0003] Most ESC BPFs use passive circuits in which a voltage-controlled capacitor acts as the regulating element. Two types of capacitors are generally used, one is a traditional varactor and the other is a MEMS bridge. BPFs using MEMS technology have low losses. However, in order to control the height of the MEMS bridge, a large DC bias voltage must be used, making the regulation slow. Furthermore, MEMS are expensive to fabricate and package. Therefore, BPFs ...

Claims

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Application Information

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IPC IPC(8): H03H7/12
Inventor 吴茹菲张海英尹军舰
Owner INST OF MICROELECTRONICS CHINESE ACAD OF SCI
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