The principle, characteristics and application circuit design of radio receiver chip based on TH71101

TH71101 is a radio receiver chip with a dual superheterodyne structure. It works in the 300-450MHz ISM frequency band. It can be matched with TH7107 and other chips to realize wireless analog and digital signal transmission in the ISM frequency band. It contains a low noise Amplifier, dual mixer, voltage controlled oscillator, PLL synthesizer, crystal oscillator and other circuits. Can receive analog and digital FSK/FM/ASK signals.

Authors: Tang Dong, Huang Zhiwei, Lu Mingxia

1 Overview

TH71101 is a radio receiver chip with a dual superheterodyne structure. It works in the 300-450MHz ISM frequency band. It can be matched with TH7107 and other chips to realize wireless analog and digital signal transmission in the ISM frequency band. It contains a low noise amplifier, dual mixer, Voltage controlled oscillator, PLL synthesizer, crystal oscillator and other circuits. Can receive analog and digital FSK/FM/ASK signals. FSK data rate can reach 40kb/s, ASK data rate can reach 80kb/s, FM bandwidth 15kHz; sensitivity 111dBm. The power supply voltage is 2.5~5.5V, the working current is 8.2mA, and the standby current is <100nA. It is suitable for various applications within the frequency range of ISM (industrial, scientific and medical), such as data communication systems, keyless entry systems, remote control telemetry systems, security systems, etc. 2 Chip packaging and pin functions

TH71101 is packaged in LQFP32, and the functions of each pin are listed in Table 1.

Table 1 TH71101 pin functions
The principle, characteristics and application circuit design of radio receiver chip based on TH71101

3 The internal structure and working principle of the chip

The internal structure block diagram of TH71101 is shown as in Fig. 1. The chip includes a low noise amplifier (LNA), two-stage mixers (MIX1, MIX2), a phase-locked loop synthesizer (PLL Synthesizer), a reference crystal oscillator (RO), a charge pump (CP), and an intermediate frequency amplifier (IFA) , Phase frequency detector (PFD) and other circuits.

The principle, characteristics and application circuit design of radio receiver chip based on TH71101

LNA is a common-transmit, common-base amplifier that receives radio frequency signals with high sensitivity. Mixer 1 (MIX1) down-converts the radio frequency signal to intermediate frequency 1 (IF1), mixer 2 (MIX2) down-converts the intermediate frequency signal 1 to interrupt signal 2 (IF2), and the intermediate frequency amplifier (IFA) amplifies the intermediate frequency signal 2 and Limit the IF signal and generate RSSI signal. The phase coincidence demodulator and mixer 3 demodulate the intermediate frequency signal. Operational amplifier (OA) performs data limiting, filtering and ASK detection. The phase-locked loop synthesizer is composed of voltage controlled oscillator (VCO1), feedback frequency divider (DIV16 and DIV2), reference crystal oscillator (RO), phase frequency detector (PFD), charge pump (CP) and other circuits, Generate the first and second level local oscillator signals LO1 and LO2.

The TH71101 receiver chip can be used to form different circuit structures to meet different needs. For FSK/FM reception, an IF resonant circuit is used in the phase coincidence demodulator. The resonant circuit can be composed of a ceramic resonator or an LC resonant circuit. For the ASK structure, the RSSI signal is fed to the ASK detector, which is composed of OA.

TH71101 adopts two-stage down-conversion. MIX1 and MIX2 are driven by the local oscillator signals LO1 and LO2 inside the chip, and together with the RF front-end filter to achieve a high image rejection, as listed in Table 2 and Table 3. Effective RF front-end filtering is to use SAW, ceramic or LC filters at the front end of the LNA and LC filters at the output of the LNA.

The principle, characteristics and application circuit design of radio receiver chip based on TH71101

4 Application circuit design

The FSK and ASK application circuits based ON TH71101 are shown in Figure 2 and 3.

The principle, characteristics and application circuit design of radio receiver chip based on TH71101

The principle, characteristics and application circuit design of radio receiver chip based on TH71101

The interface circuit of TH71101 and the one-chip computer is shown as in Fig. 4.

The principle, characteristics and application circuit design of radio receiver chip based on TH71101

When ENRX=”0″, the receiving module enters the standby state, and when ENRX=”1″, the receiving module enters the receiving state. The demodulated output data of TH71101 enters the single-chip microcomputer through RXD, and the data format and data rate are determined by the user according to their needs. It should be noted that the FSK data rate cannot exceed 40kb/s, and the ASK data rate cannot exceed 80kb/s.

Authors: Tang Dong, Huang Zhiwei, Lu Mingxia

1 Overview

TH71101 is a radio receiver chip with a dual superheterodyne structure. It works in the 300-450MHz ISM frequency band. It can be matched with TH7107 and other chips to realize wireless analog and digital signal transmission in the ISM frequency band. It contains a low noise amplifier, dual mixer, Voltage controlled oscillator, PLL synthesizer, crystal oscillator and other circuits. Can receive analog and digital FSK/FM/ASK signals. FSK data rate can reach 40kb/s, ASK data rate can reach 80kb/s, FM bandwidth 15kHz; sensitivity 111dBm. The power supply voltage is 2.5~5.5V, the working current is 8.2mA, and the standby current is <100nA. It is suitable for various applications within the frequency range of ISM (industrial, scientific and medical), such as data communication systems, keyless entry systems, remote control telemetry systems, security systems, etc. 2 Chip packaging and pin functions

TH71101 is packaged in LQFP32, and the functions of each pin are listed in Table 1.

Table 1 TH71101 pin functions
The principle, characteristics and application circuit design of radio receiver chip based on TH71101

3 The internal structure and working principle of the chip

The internal structure block diagram of TH71101 is shown as in Fig. 1. The chip includes a low noise amplifier (LNA), two-stage mixers (MIX1, MIX2), a phase-locked loop synthesizer (PLL Synthesizer), a reference crystal oscillator (RO), a charge pump (CP), and an intermediate frequency amplifier (IFA) , Phase frequency detector (PFD) and other circuits.

The principle, characteristics and application circuit design of radio receiver chip based on TH71101

LNA is a common-transmit, common-base amplifier that receives radio frequency signals with high sensitivity. Mixer 1 (MIX1) down-converts the radio frequency signal to intermediate frequency 1 (IF1), mixer 2 (MIX2) down-converts the intermediate frequency signal 1 to interrupt signal 2 (IF2), and the intermediate frequency amplifier (IFA) amplifies the intermediate frequency signal 2 and Limit the IF signal and generate RSSI signal. The phase coincidence demodulator and mixer 3 demodulate the intermediate frequency signal. Operational amplifier (OA) performs data limiting, filtering and ASK detection. The phase-locked loop synthesizer is composed of voltage controlled oscillator (VCO1), feedback frequency divider (DIV16 and DIV2), reference crystal oscillator (RO), phase frequency detector (PFD), charge pump (CP) and other circuits, Generate the first and second level local oscillator signals LO1 and LO2.

The TH71101 receiver chip can be used to form different circuit structures to meet different needs. For FSK/FM reception, an IF resonant circuit is used in the phase coincidence demodulator. The resonant circuit can be composed of a ceramic resonator or an LC resonant circuit. For the ASK structure, the RSSI signal is fed to the ASK detector, which is composed of OA.

TH71101 adopts two-stage down-conversion. MIX1 and MIX2 are driven by the local oscillator signals LO1 and LO2 inside the chip, and together with the RF front-end filter to achieve a high image rejection, as listed in Table 2 and Table 3. Effective RF front-end filtering is to use SAW, ceramic or LC filters at the front end of the LNA and LC filters at the output of the LNA.

The principle, characteristics and application circuit design of radio receiver chip based on TH71101

4 Application circuit design

The FSK and ASK application circuits based on TH71101 are shown in Figure 2 and 3.

The principle, characteristics and application circuit design of radio receiver chip based on TH71101

The principle, characteristics and application circuit design of radio receiver chip based on TH71101

The interface circuit of TH71101 and the one-chip computer is shown as in Fig. 4.

The principle, characteristics and application circuit design of radio receiver chip based on TH71101

When ENRX=”0″, the receiving module enters the standby state, and when ENRX=”1″, the receiving module enters the receiving state. The demodulated output data of TH71101 enters the single-chip microcomputer through RXD, and the data format and data rate are determined by the user according to their needs. It should be noted that the FSK data rate cannot exceed 40kb/s, and the ASK data rate cannot exceed 80kb/s.

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