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Phase detector referred to as PD, PH, or PHD (PhaseDetector). A phase comparator, which changes the phase of VCO oscillating signal is transformed into voltage changes, the phase detector output is a pulsating DC signal, the pulse DC signal low-pass filter (LPF) to filter out high frequency components after control the VCO circuit. The production of  china cell phone jammer will be outsourced.
Phase detector is a phase comparator, its input reference signal generated by the VCO phase comparison signal input, two output reflects the phase error signal error voltage. Phase detector is varied, with numbers, but also simulated. Such as dual-port phase detector, PFD, etc.. When using digital phase detector, because of its dual-port output output: In connection with the loop filter on a problem. Usually added in between a double-ended input single-ended output, and can phase detector output phase error signals correctly reflected in the circuit, this circuit is known as the charge pump or the pump circuit. Motorola's GSM cell phone, its transmitter frequency synthesizer basically uses the pump circuit. In the frequency synthesizer, in order to make accurate phase comparison, the phase detector is working in a low state. The company will sign the outsourcing agreement concerning about the manufacture of cell phone jammer.
In the cell phone circuit, the phase detector is usually integrated with the divider is a dedicated chip, the chip is often referred to as PLL (phase locked loop), or integrated in a complex chip (the chip that contains a variety of function of the circuit). Low-pass filter referred to as LPF (LowPassFilter). Low-pass filter in the frequency synthesis loop, also known as the loop filter. It is an RC circuit. In the phase detector and VCO circuit between the basic form of low-pass filter circuit shown in Figure 4-28. Low-pass filter capacitor through the resistor to set the appropriate parameters, so that high frequency components are filtered out. As the phase detector PD output contains not only the DC control signal, and some high-frequency harmonics. These harmonics will affect the VCO circuit. Low-pass filter is necessary to filter out these high frequency components in order to prevent disruption of the VCO circuit. The outsourcing of  cell phone jammer is an important link.
Voltage-controlled oscillator referred to as VCO (VoltageControlOscillator). VCO is a "voltage - frequency" converter. It will phase detector PD output voltage difference between signal changes into frequency changes. As the name suggests, VCO circuit is a voltage control circuit. Voltage control is to be completed by a special device to complete, this device is the varactor. The difference between the phase detector output voltage is actually added to the ends of the varactor. When the phase detector output changes, the varactor reverse bias across the diode changes, leading to varactor diode junction capacitance change, VCO oscillation circuit change, VCO output frequency is also changed. In practice, the varactor diode is reverse biased with its linear, controllable range. Details of outsourcing of  cell phone jammer needs to be discussed further.