In modern cell phone communications, and often require the system to provide adequate channel, the cell phone station can also take control of the system change their operating frequency. This need to provide multiple channels of frequency signals, the use of multiple oscillators is unrealistic. In the actual circuit, usually using frequency synthesizer to provide sufficient accuracy and good stability frequency. The company would like to select a subcontractor of  cell  phone jammer.
One or more of the reference frequency signal is transformed into one or more of the desired signal frequency is the frequency synthesizer technology, otherwise known as frequency synthesis technology. Commonly used as a cell phone with a PLL frequency synthesizer. Each frequency synthesis loop includes five basic functional circuits: reference clock oscillator, phase detector, low-pass filter, VCO and divider. Shown in Figure 4-22. Reference oscillation signal is set f1, set the VCO output signal is f2. Divider output signal is f2 / N. Purpose of the control loop is to make f1 = f2 / N. Phone reference clock oscillation circuit is a very important phone circuit, resulting in the 13MHz clock, while the logic circuit for the handsets provided the necessary conditions, on the other and provide the basis for the frequency synthesizer circuit clock. It is very important for the  Cellular Phone Jammer   company to choose a good subcontractor.
Phone 13MHz reference clock circuit, there are two circuits: one dedicated 13MHzVCO components, VCO components generally have four side El: output, power supply side, AFC control terminal and ground. The other is by a 13MHz (26MHz, 19.5MHz) quartz crystal, integrated circuit and external components, the crystal oscillator circuit. Figure 4-25 is the Ericsson T28 cell phone 13MHz crystal oscillator circuit. By the N234 and 13MHz crystal B320, varactor diode V322, V321, etc., the circuit 13MHz signal, processed by the N234 module output two-way: the way through capacitor C300, C302 to D300 module 15 feet, to the frequency synthesizer circuit to provide reference signal; the other way 52 feet from the N234 output logic to the logic circuit provides the clock signal; 13MHz circuit module control signal VCXOCONT from the N800. Figure 4-26 is the Motorola V998 cell phone 26MHz oscillator circuit. The subcontractor of   cell phone jammer  has to provide the good product.
From the 26MHz quartz crystal Y230, varactors CR230 and IF module U913's internal oscillator circuit is composed. Circuit, Y230 crystal is 4 feet, of which three feet are linked to a ground terminal, while the other foot is as output, AFC automatic frequency control voltage output from the U913 side of J7, U913 in J8 pin power supply side, U913 13MHz reference frequency oscillator generates a reference frequency signal source all the way to synthesize a variety of carrier frequency, the other side all the way from the J6 output of U913 to the central processor, the logic of the clock as a cell phone. The subcontractor of   cell  phone jammer  takes great responsibility.
U101 and Y101 by the quartz crystal and other components, the resonant frequency of quartz crystal Y101 (reference frequency) is 19.5MHz, the U101 module for 1.5 times the frequency processing to get the reference signal and the frequency synthesizer logic of 13MHz clock signal. Frequency synthesizer reference signal output from the foot of C10 U101; logic clock signal output from U101 feet of H7. U101 pin power supply side of the D10. VCO components or whether the composition of the crystal oscillator circuit, the control signal needs to AFC, AFC signal from the logic circuit in the DSP (Digital Voice Processor) output. As the GSM cell phone with time division multiple access (TDMA) technology to different time periods (time slot) taken between user, system, time synchronization with cell phones is very important. Such as cell phones clock with the system clock is not synchronized, it will cause the phone can not communicate with the system to normal. The  mobile phone jammer  company has two subcontractor.
In the GSM system, public broadcast control channel (BCCH) information including frequency correction and synchronization information. Phone a boot, would the logic circuit under the control of scanning the channels from which to obtain synchronization and frequency correction information. If the system detects a cell phone with the system clock is not synchronized, the phone will output logic AFC signal. AFC signal to change the 13MHz VCO circuit at both ends of the anti-bias, so that the VCO output frequency of the circuit changes. To ensure cell phones and system synchronization. The product provided by these two subcontractors of   cell  phone jammer  are both good in the quality.
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