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Radio signal reception with a PLL frequency controlled for an IF signal depending on coexistence of a spurious signal with the radio signal
Radio signal reception with a PLL frequency controlled for an IF signal depending on coexistence of a spurious signal with the radio signal
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机译:取决于杂散信号和无线电信号的共存,针对IF信号控制PLL频率的无线电信号接收
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摘要
In a radio receiver a PLL oscillator generates a phase locked oscillation signal with a controllable frequency and a frequency multiplier multiplies the controllable frequency with a controllable factor into a local oscillation frequency to provide a local oscillation signal for mixing into an IF signal with a radio signal reaching the receiver, the IF signal is monitored to raise the controllable frequency and to reduce the controllable factor when a spurious signal coexists with the radio signal. This coexistence is detected by monitoring a level difference between the IF signal and an output signal of an IF filter. Preferably, the oscillator comprises in a PLL two VCO's for generating phase locked oscillation signals of higher and lower oscillation frequencies, such as 260 and 65 MHz, and a controllable prescaler supplied with high and low voltage signals when the VCO's are put in operation at the higher and the lower oscillation frequencies. Concurrently, the controllable factor is controlled to factors of unity and four.
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