Transmission filter circuit and composite filter device
A transmission filter and circuit technology, applied in the direction of electrical components, impedance network, antenna grounding switch structure connection, etc., can solve the problems of noise, reception sensitivity degradation, third-order intermodulation distortion not considered, etc., to achieve the suppression of third-order intermodulation distortion effect
Pending Publication Date: 2021-01-12
MURATA MFG CO LTD
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Problems solved by technology
[0006] In the resonator, for example, an interference wave having a frequency relatively close to the frequency of the transmission signal is mixed into the transmission signal, and third-order intermodulation distortion may be generated based on the transmission signal and the interference wave.
For example, when the reception frequency band is higher than the transmission frequency band, the third-order intermodulation distortion appears in the reception frequency band, and thus the third-order intermodulation distortion becomes noise in the reception frequency band, which may lead to deterioration of reception sensitivity.
[0007] Regarding this point, for example, in the ladder filter circuit disclosed in the above-mentioned Patent Document 1, the third-order intermodulation distortion is not considered
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[0034] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same code|symbol is attached|subjected to the same element, and overlapping description is abbreviate|omitted.
[0035] figure 1 It is a diagram showing a configuration example of a front-end circuit including the transmission filter circuit according to the first embodiment of the present invention. The front-end circuit 100 according to this embodiment is used, for example, in a mobile communication device such as a mobile phone.
[0036] Such as figure 1 As shown, the front-end circuit 100 includes, for example, a transmission filter circuit 10, a reception filter circuit 20, input terminals T1, T2, and output terminals T3, T4. The front-end circuit 100 is connected to the antenna 30 via the antenna terminal T5.
[0037] When a mobile communication device transmits and receives a radio frequency (RF: Radio Frequency) signal via one antenn...
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The invention provides a transmission filter circuit and a composite filter device capable of suppressing third-order intermodulation distortion. The transmission filter circuit includes an input terminal, an output terminal, plural series arm resonators, and a parallel arm resonator. The input terminal receives a transmit signal. The output terminal is electrically connected to an antenna. The plural series arm resonators are electrically connected in series with each other on a line between the input and output terminals. The plural series arm resonators include first and second series arm resonators. The first series arm resonator is closest to the output terminal. The second series arm resonator is second closest to the output terminal. A first end of the parallel arm resonator is electrically connected to a node between the first and second series arm resonators. A reference potential is provided to a second end of the parallel arm resonator. The resonant frequency of the first series arm resonator is higher than that of the second series arm resonator.
Description
technical field [0001] The present invention relates to a transmission filter circuit and a composite filter device. Background technique [0002] In a mobile communication device such as a mobile phone, a common antenna may be used for transmitting a transmission signal and receiving a reception signal in order to reduce the size of the terminal. A duplexer that separates the transmitted and received signals is connected to such an antenna. As an example of a duplexer, for example, the following patent document 1 discloses a ladder-type filter circuit in which a plurality of resonators having a natural resonance frequency and an anti-resonance frequency are connected in a ladder type so that Signals of a given frequency band are passed and signals of other frequency bands are attenuated. [0003] prior art literature [0004] patent documents [0005] Patent Document 1: International Publication No. 2016 / 088680 [0006] In a resonator, for example, an interference wave...
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IPC IPC(8): H03H9/58H03H9/54H03H9/64H03H9/00
CPCH03H9/58H03H9/547H03H9/582H03H9/64H03H9/0009H03H9/0014H03H9/0004H03H9/725H03H9/706H03H9/6483H03H9/605H03H9/568H03H9/54H01Q1/50
Inventor 龟冈义宣
Owner MURATA MFG CO LTD