The principle of a conversion superheterodyne receiver
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Users questions:Mobile specific principle of the circuit, such as the antenna circuit, a frequency synthesizer circuit
Experts answer:, receive a basic component circuit is often used mobile communications devices superheterodyne conversion receiver. This is because the antenna sensing the received signal is very weak, while the frequency detector input signal level requirements of high and stable.The total gain of the amplifier usually takes over at 120dB. Put such a big volume, use the multi-stage tuned amplifier and should be stable, in fact very difficult to do. Another high-frequency selective frequency amplifier passband width is too wide, when the frequency changes, the multi-stage amplifier circuit have followed all the tuning changes, and to doUnified tuning, this is hard to do. Superheterodyne receivers do not have this problem, it will receive the RF signals into a fixed intermediate frequency, the main gain from the IF amplifier stability. There are three basic cell phone receiver frame structure: one is a conversion superheterodyne receiver, a is the superheterodyneDouble-conversion receiver, the third is the direct conversion of linear receivers. Superheterodyne conversion receiver is the mixer core circuit, receiver circuit according to phone number in the mixer to determine the receiver's circuit. 1. Superheterodyne receiver first conversion receiver RF mixer circuit is only one, Called a conversion superheterodyne receiver. Superheterodyne principle of a conversion receiver block diagram shown in Figure 4-1. It includes the antenna circuit (ANT), low-noise amplifier (LNA), mixer (Mixer), intermediate frequency amplifiers (IFAmplifier) and demodulation circuit (Demodulator) and so on. Motorola mobile phones are used to receive the circuit is basically over circuit. Working process of a conversion superheterodyne receiver are: induction into the wireless cellular antenna signal (GSM900 band 935, ** 960MHz or DCSl800 band 1805 **- 1880MHz) continuously variable frequency, the circuit through the antenna and RF filter into the receiver circuit. First, the received signal amplified by low noise amplifiers, amplified signal via radio frequency filter, was sent to the mixer. In the mixer, the VCO RF signal and receiving signal mixing, be received inFrequency signal. IF signal amplified by the IF, the IF processing module for RXI / Q demodulation, the demodulation reference signal from the receiver using IF VCO. The first intermediate frequency signal processing circuit is frequency, and then mixing with the received intermediate frequency signal obtained 67.707kHz of RXI / QSignal. 2. Superheterodyne double-conversion RF receiver if the receiver has two mixer circuit, the machine is double-conversion superheterodyne receiver. Second conversion superheterodyne receiver block diagram: Figure 4-2. Compared with the first conversion receiver, double conversion receivers have one mixer, and a VCO, the VCO circuit has been called in some IFVCO or VHFVCO. Nokia, Ericsson phones, Samsung, Panasonic and Siemens mobile phones to receive circuit is that the majority of circuit. In Figure 4-1 and Figure 4-2, the demodulation circuit part has VCO, should be noted thatWhere the VCO signal is used for demodulation, a reference signal and the VCO signal usually comes from two ways: First, the signal from the reference frequency 13MHz, another special from IF VCO. Second conversion superheterodyne receiver working process is: induction into the wireless cellular antenna signal (GSM900 or DCSl800 band 935 ~ 960MHz frequency band 1805-1880MHz) by the antenna into the receiver circuit and RF filter circuit. First, the received signal amplified by low noise amplifier amplified the signal sent via radio frequency filter after the first mixer. In the first mixedFrequency, the radio frequency signal receiving VCO signal mixing, are receiving the first IF signal. The first IF signal and receiving the second local oscillation signal mixing, by receiving the second IF. Receiving the second local oscillation circuit from VHFVCO. Receiving the second IF signal amplified by the second IF, the IF processingModule for RXI / Q demodulation, demodulation reference signal used to receive from the IF VCO. The first intermediate frequency signal processing circuit is frequency, and then mixing with the received intermediate frequency signal obtained 67.707kHz of RXI / Q signal. 3. Direct conversion receiver with the new mobile linearThe advent of some new phone using the direct conversion of linear receiver circuit. Such as Nokia 8210,8250,3310 phones. The receiver of the circuit shown in Figure 4-3. A conversion from in front of the receiver and the secondary conversion receiver block diagram can be seen, RXI / Q signal
Experts answer:, receive a basic component circuit is often used mobile communications devices superheterodyne conversion receiver. This is because the antenna sensing the received signal is very weak, while the frequency detector input signal level requirements of high and stable.The total gain of the amplifier usually takes over at 120dB. Put such a big volume, use the multi-stage tuned amplifier and should be stable, in fact very difficult to do. Another high-frequency selective frequency amplifier passband width is too wide, when the frequency changes, the multi-stage amplifier circuit have followed all the tuning changes, and to doUnified tuning, this is hard to do. Superheterodyne receivers do not have this problem, it will receive the RF signals into a fixed intermediate frequency, the main gain from the IF amplifier stability. There are three basic cell phone receiver frame structure: one is a conversion superheterodyne receiver, a is the superheterodyneDouble-conversion receiver, the third is the direct conversion of linear receivers. Superheterodyne conversion receiver is the mixer core circuit, receiver circuit according to phone number in the mixer to determine the receiver's circuit. 1. Superheterodyne receiver first conversion receiver RF mixer circuit is only one, Called a conversion superheterodyne receiver. Superheterodyne principle of a conversion receiver block diagram shown in Figure 4-1. It includes the antenna circuit (ANT), low-noise amplifier (LNA), mixer (Mixer), intermediate frequency amplifiers (IFAmplifier) and demodulation circuit (Demodulator) and so on. Motorola mobile phones are used to receive the circuit is basically over circuit. Working process of a conversion superheterodyne receiver are: induction into the wireless cellular antenna signal (GSM900 band 935, ** 960MHz or DCSl800 band 1805 **- 1880MHz) continuously variable frequency, the circuit through the antenna and RF filter into the receiver circuit. First, the received signal amplified by low noise amplifiers, amplified signal via radio frequency filter, was sent to the mixer. In the mixer, the VCO RF signal and receiving signal mixing, be received inFrequency signal. IF signal amplified by the IF, the IF processing module for RXI / Q demodulation, the demodulation reference signal from the receiver using IF VCO. The first intermediate frequency signal processing circuit is frequency, and then mixing with the received intermediate frequency signal obtained 67.707kHz of RXI / QSignal. 2. Superheterodyne double-conversion RF receiver if the receiver has two mixer circuit, the machine is double-conversion superheterodyne receiver. Second conversion superheterodyne receiver block diagram: Figure 4-2. Compared with the first conversion receiver, double conversion receivers have one mixer, and a VCO, the VCO circuit has been called in some IFVCO or VHFVCO. Nokia, Ericsson phones, Samsung, Panasonic and Siemens mobile phones to receive circuit is that the majority of circuit. In Figure 4-1 and Figure 4-2, the demodulation circuit part has VCO, should be noted thatWhere the VCO signal is used for demodulation, a reference signal and the VCO signal usually comes from two ways: First, the signal from the reference frequency 13MHz, another special from IF VCO. Second conversion superheterodyne receiver working process is: induction into the wireless cellular antenna signal (GSM900 or DCSl800 band 935 ~ 960MHz frequency band 1805-1880MHz) by the antenna into the receiver circuit and RF filter circuit. First, the received signal amplified by low noise amplifier amplified the signal sent via radio frequency filter after the first mixer. In the first mixedFrequency, the radio frequency signal receiving VCO signal mixing, are receiving the first IF signal. The first IF signal and receiving the second local oscillation signal mixing, by receiving the second IF. Receiving the second local oscillation circuit from VHFVCO. Receiving the second IF signal amplified by the second IF, the IF processingModule for RXI / Q demodulation, demodulation reference signal used to receive from the IF VCO. The first intermediate frequency signal processing circuit is frequency, and then mixing with the received intermediate frequency signal obtained 67.707kHz of RXI / Q signal. 3. Direct conversion receiver with the new mobile linearThe advent of some new phone using the direct conversion of linear receiver circuit. Such as Nokia 8210,8250,3310 phones. The receiver of the circuit shown in Figure 4-3. A conversion from in front of the receiver and the secondary conversion receiver block diagram can be seen, RXI / Q signal
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