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RCCB named Residual Current Circuit Breaker. When there is human electricity shock or if the leakage current of the line exceeds the prescribed value, Residual current circuit breaker/RCCB(without over-current protection) will cut off the power rapidly to protect human safety and prevent the accident due to the current leakage. The rccb switch which made from Korlen electric can be used as infrequent changeover of the line in normal situation.
Korlen electric ---- the rccb switch manufacturer,produces types of Residual Current Circuit Breaker. It is applicable to industrial site, commercial site, tall building and civil house.
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The fractional frequency synthesizer must be connected to a loop filter circuit and a voltage controlled oscillator to form a complete phase-locked loop circuit. The design of the loop filter in its peripheral circuit will directly affect the performance test of the chip. Taking the ADF4153 fractional frequency synthesizer as an example, the design method of its peripheral loop filter is studied. The loop filter design flow based on chip test is given and verified. The test results show that the filter can meet the needs of the fractional frequency synthesizer chip test.
In the chip test of the fractional frequency synthesizer, the digital part can be realized by the conventional digital test method; and the phase noise and spurious noise of the output RF signal require the chip to work under the normal output state to be tested. The fractional frequency synthesizer chip needs to be connected with an external loop filter (LF) and a voltage controlled oscillator (VCO) to form a complete phase-locked loop, which can be realized under the premise of normal chip function. Test under phase noise and spurious noise.
In general, voltage-controlled oscillators use off-the-shelf devices. When selecting devices, pay attention to the matching of performance indicators. Only loop filters need to be calculated and designed. The loop filter is mainly used as a low-pass filter in the whole circuit. It performs low-pass filtering on the pulse signal output from the chip phase detector to filter out high-frequency components, and finally obtains a relatively smooth DC voltage signal to control the VCO. Work to get a stable frequency output. The performance of the loop filter will directly affect the performance of the fractional-frequency synthesizer chip.
Taking the ADF 4153 fractional frequency synthesizer as an example, the design method of the third-order loop filter which is easy to implement is given, which can meet the needs of actual chip testing.
1 The design loop filter of the external loop filter is an important part of the charge pump phase-locked loop circuit, which is connected between the charge pump and the voltage controlled oscillator. The fundamental frequency characteristics of the phase-locked loop are determined by the loop filter. In fact, it is because of the loop filter that the phase-locked loop can choose to operate in any center frequency and bandwidth. There are many types of loop filters, which are roughly divided into active filter and passive filter. Compared with active filters, passive filters have the advantages of simple structure, low noise and high stability. Degree and easy to achieve.
The most common passive filter is the third-order filter shown in Figure 1. In general, the bandwidth of the loop filter should be 1/10 of the PFD frequency (channel spacing). Increasing the loop bandwidth reduces the lock time. However, excessive loop bandwidth greatly increases the instability, resulting in a state in which the phase locked loop cannot be locked. 
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