Radio frequency front-end transmitting circuit, radio frequency front-end receiving circuit and radio frequency front-end circuit

Abstract

The embodiment of the invention provides a radio frequency front-end transmitting circuit, a radio frequency front-end receiving circuit and a radio frequency front-end circuit. The circuit includes:a power amplifier; a first capacitor C1; a balun, wherein the input inductor of the balun and the first capacitor C1 form a resonance network, the resonance network is connected with the output of thepower amplifier, one end of the output of the balun is grounded, and the other end of the output of the balun is connected with a first inductor L1 and an antenna in parallel, the first inductor L1 is connected with the first circuit, the second circuit and the third circuit in parallel, the first circuit comprises a second capacitor C2 and a first switch S1 which are connected in series, and thefirst switch S1 is grounded; the second circuit comprises a third capacitor C3 and a second switch S2 which are connected in series, and the second switch S2 is grounded; and the third circuit comprises a fourth capacitor C4 and a low-noise amplifier which are connected in series, and the fourth capacitor C4 is connected with the input of the low-noise amplifier. The circuit can suppress local oscillator traction and improve the performance of a transmitter.

Description

technical field [0001] The present disclosure relates to the technical field of the Internet of Things, and in particular to a radio frequency front-end transmitting circuit, a radio frequency front-end receiving circuit and a radio frequency front-end circuit applied to NB-IOT chips to suppress local oscillator traction. Background technique [0002] With the increasing demand of the Internet of Things (IoT), NB-IoT (Narrowband Internet of Things) technology has become an important branch of the Internet of Everything. NB-IoT is built on a cellular network and only consumes about 180kHz of bandwidth. It can be directly deployed on a GSM network, UMTS network or LTE network to reduce deployment costs and achieve smooth upgrades. Many companies predict that the number of global IoT connections will be hundreds of billions in the future. A large number of things have been connected, and most of these connections are carried by short-range communication technologies such as Bl...

AI Technical Summary

Problems solved by technology

[0004] Even if the VCO frequency is the carrier frequency (f LO ), but the high-order harmonics generated by the nonlinearity of the power amplifier will also cause local oscillator traction. Not only that, this interference will also affect the division of 2 circuits in the circuit or the inductive devices in the mixer

Excessive LO pulling will deteriorate the EVM and output spectrum of the transmitter, and severe LO pulling can cause the transmitter to fail to work normally

[0005] At present, there are not many ways to suppress the pulling of the local oscillator. By reducing the sensitivity of the voltage-controlled oscillator to the power supply, reducing the power of the transmitter or improving the linearity of the power amplifier, the pulling of the local oscillator can be reduced to a certain extent, but at the expense of the transmitter performance or increased power at the expense of

In practical applications, adding a shield to the off-chip power amplifier can also reduce its radiation, but it will increase the cost of the chip

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