| 摘要 |
In a receiver a settable frequency divider (6,7) divides the frequency of a voltage-controlled oscillator (3). The resultant frequency is compared in a phase comparison circuit (8) with a constant reference frequency an error voltage proportional to the phase deviation controls the oscillator (3). The oscillator frequency is furthermore additively mixed with the received frequency in a mixer circuit (2), which is followed by an intermediate frequency amplifier (4). A regulating circuit (5) including a frequency discriminator with a capacitance diode is provided for the purpose of automatic retuning and additional subjective detuning. It generates, in dependence on the deviation of the received frequency from the oscillator frequency as well as also through application of a voltage to the capacitance diode, a regulating voltage which after analog-digital conversion at 11 proportionally varies the set dividing ratio of the frequency divider (6,7). Retuning and search for a different station is facilitated by control keys 13, 14, a coder 15, a switch 12, a D/A converter 16 and a logic circuit 17 which shifts the frequency discriminator characteristics as well as vary the division ratio of 7 until the desired station is obtained. <IMAGE> |
