Filter amplifier

Abstract

A filter amplifier is composed of a first mixer, a first surface acoustic wave filter, an amplifier with a gain controllable, a second surface acoustic wave filter and a second mixer, wherein the first mixer, the first surface acoustic wave filter, the amplifier with the gain controllable, the second surface acoustic wave filter and the second mixer are sequentially connected. The first mixer is used for receiving an input signal and a first local oscillator signal and down-converting the input signal into an intermediate-frequency signal. The intermediate-frequency signal is filtered through the first surface acoustic wave filter and then is output to the amplifier with the gain controllable to be amplified. The amplified signal is input again to the second surface acoustic wave filter and filtered again. The signal filtered again is up-converted to a frequency through the second mixer and then output, wherein the frequency is wherein the input signal is originally located. A first local oscillator circuit is in connection with the first mixer so that the stable first local oscillator signal can be supplied to down-conversion of the first local oscillator circuit. The frequency of the first local oscillator signal changes following the change of the input signal, and the intermediate-frequency signal can be a fixed value from beginning to end. A second local oscillator circuit is in connection with the second mixer. According to the filter amplifier, data timing transfer (DTT) signal transmission can be perfectly compatible with a 4G long term evolution (LTE) signal.

Description

technical field [0001] The invention belongs to the technical field of radio frequency signal processing, and in particular relates to a filter amplifier. The filter amplifier adopts a SAW filter (saw filter) to realize compatibility between a 4G LTE (fourth generation mobile communication technology) network and a digital terrestrial television (DTT). Background technique [0002] The 4G LTE (Long Term Evolution, long-term evolution) project is an evolution of 3G, which started at the 3GPP meeting in Toronto in 2004. 4G LTE improves and enhances the air access technology of 3G, and adopts OFDM and MIMO as the only standard for its wireless network evolution. [0003] The 4G LTE standard puts forward higher requirements for DTT (Digital Terrestrial TV, digital terrestrial television). The rapid introduction of the fourth generation (4G LTE) mobile network services in the world has seriously affected the frequency in 790-862MHz (61-69 channel ) DDT transmission, even if t...

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Problems solved by technology

[0003] The 4G LTE standard puts forward higher requirements for DTT (Digital Terrestrial TV, digital terrestrial television). The rapid introduction of the fourth generation (4G LTE) mobile network services in the world has seriously affected the frequency in 790-862MHz (61-69 channel ) DDT transmission, even if the transmission channel upper limit of the DTT signal in the future is reduced to 60 channels (790MHz) and the 1MHz bandwidth of 790-791MHz is defined as a "buffer" to divide the DTT signal and the 4G LTE network signal, the current equipment proposes The requirements of DTT are also very strict. The "defense frequency ban

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