JPS62166625A - Pll circuit - Google Patents

Abstract

PURPOSE:To stop the oscillation of the oscillator circuit of an unnecessary band to reduce unnecessary radiation, by interrupting and conducting the supply voltages of voltage-controlled oscillator circuits for each band in a PLL circuit in corresponding with band selection. CONSTITUTION:Voltage-controlled oscillation circuits 7 and 7' are respectively provided with switching circuits 30 and 31 which are use for interrupting and conducting the application of supply voltages to band switching S1 and S2. Since a transistor 28 is under a conducted state and another transistor 23 is set to a conducted state when a band switching signal S1 is high and another band switching signal S2 is low, and then, the 1st band is selected, a supply voltage is supplied to the voltage-controlled oscillator circuit 7 and the circuit 7 makes oscillating operations. Moreover, transistors 29 and 24 are cut off since the band switching signal S2 is low and, accordingly, no supply voltage is applied across the voltage-controlled oscillator circuit 7'. As a result, the voltage-controlled oscillator circuit 7' is set to a nonoperating state and unnecessary radiation is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to control means for voltage controlled oscillation circuits used in channel selection devices for radio receivers and television receivers. The present invention relates to a PLL circuit used in a multiband synthesizer receiver configured with a phase-locked loop (phase-locked loop).

2. Prior Art FIG. 2 shows an example of a conventional synthesizer receiver in which the local oscillation circuit 6 is constructed from a PLL circuit.

In this circuit, broadcast radio waves are taken in from antenna 1, and R
A mixer 3 extracts the frequency difference from the local rooting circuit 6 via the F amplification section 2, and a desired signal is obtained via the IF amplification section 4 and the detection circuit section 6.

Here, the local oscillation circuit 6 includes a reference oscillation circuit 11, a voltage controlled oscillation circuit 7, a variable frequency divider 9 whose output can be set to an arbitrary frequency division ratio, and an output of the variable frequency divider 9 and a reference It is equipped with a phase comparator 1o for comparing the output of the oscillation circuit 11, and the output of the phase comparator 1° is added to the voltage controlled oscillation circuit 7 via a low-pass filter 8 to control it and oscillate at a predetermined frequency. I'm trying to get the output.

Since this variable frequency divider 9 performs digital signal processing,
The output of the voltage controlled oscillation circuit 7 must be amplified to a logic level by providing an amplifier.

Here, FIG. 3 shows a switching section of a conventional amplification circuit and a multiband voltage controlled oscillation circuit. The outputs of the voltage controlled oscillator circuits 7, 7' are amplified by analog amplifying sections 13, 14, and band switching signals S1. In S2, the signal is selected via the gate circuits 19, 20, and 21 and applied to the variable frequency dividing circuit section 22. here,
Band switching signal S1. The signal S2 is applied to switching elements 17 and 18, which operate to ground unnecessary outputs of the voltage controlled oscillation circuits 7 and 7', thereby reducing unnecessary radiation.

Problems to be Solved by the Invention As mentioned above, in the conventional example shown in FIG. 2, the switching elements 17 and 18 are configured to ground unnecessary voltage-controlled oscillation circuit outputs to reduce unnecessary radiation. However, both voltage controlled oscillation circuits 7 and 7' are in an oscillating state, and are not configured to block unnecessary radiation emitted from them. Therefore, there has been a problem in that interference is often caused by unnecessary radiated signals.

Therefore, an object of the present invention is to provide a PLL circuit that prevents unnecessary radiation from the voltage controlled oscillation circuit.

Means for Solving the Problems In the present invention, the application of power supply voltages other than those corresponding to the selected band among the plurality of voltage controlled oscillation circuits is selectively cut off by using a band switching signal or the like. At the same time, the outputs of these voltage controlled oscillation circuits are selectively taken out and supplied to a programmable frequency divider.

Function In this way, by selectively cutting off or conducting the application of the power supply voltage to the voltage controlled oscillation circuit using a band switching signal, etc., and selectively taking out the output, only the necessary voltage controlled oscillation circuit can be operated. Since other unused voltage controlled oscillation circuits can be made inoperable, unnecessary radiation can be greatly reduced.

Embodiment Hereinafter, a PLL circuit according to an embodiment of the present invention will be explained with reference to the drawing of FIG.

The part corresponding to the variable frequency divider 9 in FIG. 1 is 12 in FIG. One band switching signal S1.
The signal selected by S2 is guided to the variable frequency divider circuit 22.

Here, the voltage controlled oscillation circuits 7 and 7' are band switching circuits S
1. Switching circuits 30 and 31 are provided to cut off and conduct the application of the power supply voltage at S2. 23°24 is PNP
) transistor, which is pull-amplified through a resistor 24.25, and connected to the collector of an NPN transistor (NPN) transistor 28.29 through a base resistor 26.27. The emitters of the transistors 28 and 29 are grounded, and the band switching signals S1 . S
2 is applied.

Here, the band switching signal S is s Hw and S2 is IL1
When the first band is selected in , transistor 28 is conductive, which causes transistor 23
becomes conductive, so the power supply voltage is supplied to the voltage controlled oscillator circuit, causing it to oscillate. Also, the band switching signal S
2 is "L", the transistor 29 is off, and the transistor 24 is also off, so no power supply voltage is applied to the voltage controlled oscillation circuit 7'.

Therefore, the power supply voltage controlled oscillation circuit 7' becomes inoperative. This prevents unnecessary radiation.

At the same time, the input of the gates 19 and 20 is also the band switching signal S1.
．． It is switched in S2. That is, the band switching signal S1 is “H”.
1, the output of the gate 19 is transmitted to the OR gate 21, and the output of the analog amplifier 14 is cut off by the gate 2o. This is because although the voltage controlled oscillation circuit 7' is not operating, the analog amplifier 14 has a high amplification gain, so the gate 20 is provided to prevent any output signal from being output and causing any adverse effects.

When the band switching signal S is "L" and 82 is 1) (if it is 1, the operation is the opposite).

Effects of the Invention As described above, according to the present invention, the PL
By cutting off and conducting the power supply voltage of the voltage controlled oscillation circuit for each band in the L circuit, oscillation of the oscillation circuit of unnecessary bands can be stopped and unnecessary radiation can be reduced.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a PLL circuit according to an embodiment of the present invention, Fig. 2 is a block diagram showing the configuration of a general PLL synthesizer receiver, and Fig. 3 is a diagram showing the conventional main parts in Fig. 2. ′−°... 2...RF amplification section, 3...Mixer, 4
...Intermediate frequency amplification section, 5...Detection circuit, 6...Local oscillation circuit, 7, 7'...
Voltage controlled oscillation circuit, 8...Low pass filter %9...Variable frequency divider circuit, 1o...Phase comparison circuit, 11...Reference frequency oscillation circuit, 30
゜31...Switching circuit for power supply voltage supply. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 3
figure

Claims (1)

[Claims] A plurality of voltage controlled oscillators corresponding to each band of a multi-band receiver, a plurality of analog amplifiers that amplify the output of each voltage controlled oscillator and guide it to a programmable frequency divider, and the above voltage control in response to band selection. means for controlling the output of the analog amplifier to selectively route the output of the oscillator to the programmable frequency divider; and means for controlling the output of the voltage controlled oscillator corresponding to the analog amplifiers not selected in response to band selection A PLL circuit comprising switching means for cutting off the power supply voltage and applying only the power supply voltage of the selected voltage controlled oscillator.