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Band reject filters

A filter and frequency band technology, applied in the input stage field of low noise amplifiers, which can solve problems such as differential notch form factor and insertion loss

Inactive Publication Date: 2009-09-30
APPLE INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In the reported literature, rather poor notch form factor and insertion loss have been obtained

Method used

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  • Band reject filters
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Examples

Experimental program
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Embodiment Construction

[0031] refer to figure 1 , two series resonators SR2 and SR4 are connected in series with an input port 6 and an output port 8. Two parallel resonators PR10 and PR12 are connected in a ladder configuration between two series resonators SR2 and SR4 and a ground terminal 14 .

[0032] The resonator may be a surface acoustic wave resonator or a thin film bulk acoustic wave resonator.

[0033] The two series resonators SR2 and SR4 are designed to present high impedance across the stopband of interest. This is achieved by designing the filter to be anti-resonant at the stopband frequency. The shunt or parallel resonators PR10 and PR12 are designed to provide low impedance in the stop band. This is achieved by designing these filters to resonate at or near resonance in the stop band.

[0034] Therefore, the overall effect of the filter is to provide a high impedance for the signal present between inputs 6 and 14 in the stopband band.

[0035] In the application project which wi...

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Abstract

The present invention provides a radio frequency band-stop filter, which has a band-stop frequency band and pass-band bands on both sides of the band-stop band, the radio-frequency band-stop filter includes an input port connected in series to the radio-frequency band-stop filter and A series acoustic resonator between the output ports and a shunt acoustic resonator connected in parallel between the input port and the output port, the shunt acoustic resonator is arranged to resonate on the stopband frequency band, and the series acoustic resonator is arranged to anti-resonate at the stopband frequency band. Such a filter overcomes the insertion loss and power-handling limitations of conventional bandpass architectures, and can lend itself to power amplifier as well as duplexer applications.

Description

technical field [0001] The present invention relates to a radio frequency band-stop filter, a base station power amplifier for cellular wireless networks, a duplexer for mobile phone handsets, and an input stage for a low noise amplifier (LNA). Background technique [0002] Since the mid-1960s, surface acoustic wave (SAW) devices have been studied and gradually commercialized. Such devices typically have electrodes in the form of interlocking "fingers" (so-called interdigitated electrodes) formed over a piezoelectric substrate. When a high frequency signal is applied to the input electrodes, mechanical oscillations in the form of acoustic traveling waves are generated on the piezoelectric substrate, which are detected by the output electrodes. Generally, when the wavelength of the surface acoustic waves and the period of the electrode "finger" are the same, the amplitudes of the surface acoustic waves are at their maximum, and the device has a low electrical impedance. At ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H03H9/64H03H9/145H03H9/58H03H9/60
CPCH03H9/6463H03H9/605H03H9/547H03H9/6476H03H9/6483H03H9/6409H03H9/64
Inventor 史蒂夫·A·博丁萨姆塞克·西查勒恩简春云
Owner APPLE INC