A wireless transmitter and a band-stop filter

Abstract

The invention discloses a wireless transmitter and a band rejection filter. The wireless transmitter comprises an analog base band circuit, a passive RC band rejection filter, a passive mixer, a driving amplifier and a balanced-unbalanced converter. A band rejection frequency point of the passive RC band rejection filter is a far-end noise frequency point, and the filter is utilized for filtering out far-end noise of the analog base band circuit. The far-end noise contributed by the analog base band circuit is greatly reduced, in addition, a passive achieving manner is utilized by the band rejection filter so as to ensure that noise induced by the band rejection filter is very low and the characteristic of extremely low far-end noise of a whole wireless transmitter system is achieved.

Description

technical field [0001] The invention relates to a wireless transmission device, in particular to a wireless transmitter and a band rejection filter. Background technique [0002] In a wireless communication system, the far-end noise of a transmitter is a key indicator, and the 3rd Generation Partnership Project (The3rdGenerationPartnershipProject, 3GPP) has strict regulations on it. In frequency-division duplex (FDD) systems, far-end noise from the transmitter leaks into the receiver input, raising the receiver's noise floor and reducing sensitivity. Therefore, the output of the transmitter under the traditional technology needs an off-chip surface acoustic wave filter (SAW) to filter out the far-end noise, which increases the cost. Such as figure 1 As shown, the transmitter includes an analog baseband circuit, a mixer, a driving amplifier, and a balun, all of which are integrated in a radio frequency integrated circuit (RFIC), and the RFIC is connected to an off-chip surf...

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Problems solved by technology

[0005] However, since the transmitter structure of Document 2 uses a first-order passive RC low-pass filter for filtering, there are obvious deficiencies

Because the analog baseband circuit is generally implemented by operational amplifiers, resistors and capacitors, the noise itself is relatively large

The out-of-band attenuation of the first-order passive RC low-pass filter is slow, and the filtering effect on the far-end noise is limited. At this time, the noise of the analog baseband circuit is still the main noise source of the transmitter system, and it is difficult to achieve multi-mode Goals of Off-Chip Surface Acoustic Wave Filters (SAW)

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