RF front-end transmitting circuit, RF front-end receiving circuit and RF front-end circuit

Abstract

Embodiments of the present disclosure provide 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, the input inductance of the balun and the first capacitor C1 constitute a resonant network, the resonant network is connected to the output of the power amplifier, and the balun One end of the output is grounded, and the other end is connected in parallel with the first inductance L1 and the antenna; wherein the first inductance L1 is connected in parallel with the first circuit, the second circuit and the third circuit; the first circuit includes a second capacitor connected in series C2 and a first switch S1, the first switch S1 is grounded; the second circuit includes a third capacitor C3 connected in series and a second switch S2, and the second switch S2 is grounded; the third circuit includes a series connection The fourth capacitor C4 and the low noise amplifier, the fourth capacitor C4 is connected to the input of the low noise amplifier. This circuit can suppress the pulling of the local oscillator and improve the performance of the 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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