Passive filter circuit and transmitting circuit

Abstract

The invention discloses a passive filter circuit and a transmitting circuit. The passive filter circuit comprises a first selective circuit, a second selective circuit, a first capacitor and a first load. An input signal is connected into the input end of the first selective circuit, the first selective circuit comprises a plurality of first selective sub-circuits which are connected in parallel,and each first selective sub-circuit is suitable for being controlled to be switched on so as to transmit the input signal or being controlled to be switched off so as to stop transmitting the input signal. The input end of the second selective circuit is coupled with the output end of the first selective circuit, the second selective circuit comprises a plurality of second selective sub-circuitswhich are connected in parallel, and each second selective sub-circuit is suitable for being controlled to be switched on so as to transmit an output signal of the first selective circuit or being controlled to be switched off so as to stop transmitting the output signal of the first selective circuit. One end of the first capacitor is coupled with the output end of the first selective circuit. One end of the first load is coupled with the output end of the first selective circuit, and the other end of the first load is coupled with the other end of the first capacitor. According to the passive filter circuit and the transmitting circuit, gain control can be achieved in the passive filter circuit.

Description

technical field [0001] The invention relates to the technical field of integrated circuits, in particular to a passive filtering circuit and a transmitting circuit. Background technique [0002] In a wideband code division multiple access (W-CDMA) transmission (Transmit, TX) circuit, the total gain range is required to exceed 70dB. In order to achieve the required gain range, in the driver amplifier (DA), in addition to controlling the size of the main amplifier tube, current steering (current steering) and capacitive voltage divider (cap divider) technologies are also used to achieve a gain adjustment range of 78dB (Among them, the main amplifier tube can achieve 36dB, the current steering technology can achieve 24dB, and the remaining 18dB can be adjusted by capacitive voltage division technology). [0003] However, the gain control of the transmitting circuit in the prior art needs to be implemented using radio frequency (Radio Frequency, RF) technology. Then, the gain ...

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Problems solved by technology

[0003] However, the gain control of the transmitting circuit in the prior art needs to be realized by radio frequency (Radio Frequency, RF) technology

Then, the gain step of capacitive voltage division technology will change with the change of radio frequency, so that the gain range of different frequency bands is very different; in addition, from the perspective of layout design (layout), the coupling of radio frequency is stronger, There is coupling between the inductors and the wiring, and it is difficult to achieve a gain range of 78dB in practice

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