What Is the Regenerative Circuit?

In 1912, De Forrest, Armstrong, and Lanmore invented the regenerative circuit, which uses positive feedback technology to amplify the audio signal to a level that can be received. Ordinary regenerative circuits use positive feedback to strengthen the input signal, and the super regenerative circuit does use the input signal to affect the local oscillation signal, hence the name. The regenerative circuit is known as the "midwife of a radiotelephone".

L2 and C3 form a parallel resonant frequency selection, C2 is positive feedback, and the transmitting junction capacitances of R1, C4 and Q1 generate intermittent oscillations. C5 filters the high frequency and provides the AC channel output. I heard that when the antenna receives the signal of the resonant frequency, the local oscillator will be controlled by the received signal. After C5 filters the high frequency, there will be a low frequency output, but I do nt know. What is the principle, and how does intermittent oscillation occur. The principle is probably this: due to the addition of positive feedback, the RF signal will become stronger and stronger, and at the same time, due to the shoulder effect of the transmitting node, a low-frequency signal is generated. This low-frequency signal changes the static operating point of the three organs, and the transistor gradually enters The cut-off caused no further amplification of the radio frequency, and then the operating point returned to normal again when R1 was discharged, and the three organs were able to amplify again. In this cycle, intermittent mode operation occurred. The 4.7uF capacitor is used to short the base to ground. This is a common base circuit. The pole of the emitter is used to block high frequency and low frequency. The output capacitor has the same effect as the base 4.7u capacitor, but it short-circuits the radio frequency to ground and does not short-circuit at low frequencies. The super-regenerative radio remote control circuit is composed of a radio transmitter and a super-regenerative detection receiver. Radio transmitter: It is composed of a high-frequency carrier frequency oscillator (generally 30-450MHz) capable of generating equal amplitude oscillation and a low-frequency oscillator that generates low-frequency modulated signals. Circuits used to generate carrier frequency vibration and modulated oscillation generally include: multivibrators, complementary oscillators, and quartz crystal oscillators.

The low-frequency modulated wave generated by the low-frequency oscillator is generally a square wave with a certain width. For multi-channel control, you can use square waves with different widths or square waves with different frequencies to modulate high-frequency carriers to form a group of modulated waves, which are transmitted to the air as control signals to form a group. The modulated wave is transmitted to the air as a control signal. Super regenerative detection receiver: The super regenerative detection circuit is actually a high-frequency oscillator controlled by intermittent oscillation. This high-frequency oscillator uses a capacitive three-point oscillator. The oscillation frequency is consistent with the transmitter's transmission frequency. Intermittent oscillation (also known as quenched decorative oscillation) is generated during the oscillation process of high-frequency oscillation, which in turn controls the oscillation and intermittent of high-frequency oscillator. The frequency of the intermittent (quenching) oscillation is determined by the parameters of the circuit (generally 100 to several hundred kHz). If this frequency is selected lower, the circuit has better anti-interference performance, but the receiving sensitivity is lower: Conversely, if the frequency is selected higher, the receiving sensitivity is better, but the anti-interference performance is worse. Both should be considered according to the actual situation. The super regenerative detection circuit has a very high gain. When the control signal is not received, due to the interference of external stray signals and the thermal turbulence of the circuit itself, a unique noise is called super noise. The frequency range of this noise is It is between 0.3 ~ 5kHz, it sounds like a rustling sound like flowing water. When there is no signal, the super noise level is very high, and the noise voltage is output after filtering and amplification. This voltage is used as a state control signal of the circuit to make the relay actuate or open (depending on the state of the design). When a control signal arrives, the circuit resonates, super noise is suppressed, and the high-frequency oscillator starts to oscillate. The speed of the oscillation process and the length of the intermittent time are controlled by the amplitude of the received signal. When the amplitude of the received signal is large, the starting level is high, the oscillation process is set up quickly, the interval between each oscillation is also short, and the obtained control voltage is also high; otherwise, when the amplitude of the received signal is small, the obtained control voltage is also low. In this way, a low-frequency voltage consistent with the control signal is obtained on the load of the circuit, and this voltage is another control voltage of the circuit state. ^[3]