JP2535921B2 - Prescaler - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a digital tuning system (hereinafter referred to as DTS).
It is used for a radio that can receive AM / FM / TV band using (abbreviation), and especially relates to a prescaler with frequency division function switching.

[Prior Art] Phase Locked Loop (hereinafter referred to as PLL) in DTS
Although the equipment that applies is used in many fields, AM
Also used for radio that can receive / FM / TV band.

There are ICs (hereinafter abbreviated as PLL + controller) that have the functions of PLL and controller as devices to which the above-mentioned PLL is applied, but the IC is generally input only for AM and FM + TV, and is input to the input for FM + TV. Depending on the difference between the FM band and TV band signal switching methods, the two methods shown in FIGS. 2 and 3 can be considered.

In Fig. 2, FM and TV signals are input from separate input terminals, and the TV signal passes through the input amplifier 12 and is further divided by 1/2.
3, passing through the output amplifier 14. Also, the FM signal is input amplifier 1
Pass only 1 through the TV signal and switch 16 to switch to P
Input to FM + TV input of LL + controller 15. on the other hand,
The AM band signal is directly input to the AM input of the PLL + controller 15.

In Fig. 3, the FM and TV input signals are first switched by the switch 17 and input to the common input amplifier 18, and the 1/2 divider 1
The function of directly outputting the output of the input amplifier 18 without dividing by switching the control terminal 21 added to 9 to the power supply voltage and the ground, or a 1/2 dividing function can be selected.
Furthermore, the output of the 1/2 frequency divider 19 is sent to the PLL via the output amplifier 20.
This is a method of inputting to the FM + TV input of the + controller 15. On the other hand, the AM signal is the same as in FIG.

 Blue, the dotted lines in FIGS. 2 and 3 show one IC.

[Problems to be solved by the invention]

In the conventional method shown in FIG. 2, the FM amplifier and the TV amplifier are used.
It requires two ICs with a 1/2 division prescaler, which has the drawback of requiring more area in the set.

Also, in FIG. 3, only one IC is required, but 1 / IC
A current must always flow through the divide-by-2 frequency divider, whether it is divided by 1/2 or not.

As described above, the conventional method has a drawback that it is not suitable for miniaturization and low power required in the market at present.

Also, in the conventional example shown in FIGS. 2 and 3, the switches 16 and 17 must be used to switch the high frequency signal, respectively. However, this must be configured by an electronic circuit or a high frequency relay must be used. In the case of, there was a drawback that it became expensive.

[Means for solving problems]

The FM / TV prescaler of the present invention can
, And the input terminal of TV and the input amplifier are provided separately,
It has a method of switching the signal of the TV band divided by 1/2 and the FM signal passed through the input amplifier by the control terminal and taking it out through the output amplifier.

Furthermore, the control terminal is controlled so that no current flows through the unused circuits.

〔Example〕

 The present invention will be described with reference to the drawings.

FIG. 1 is a prescaler according to an embodiment of the present invention. FM
When you want to take in the signals of + TV1 to 3 channels, apply a ground potential to the control terminal 21 from the outside to turn off switch 5, switch 6 to b, switch 7 to on,
A current flows in the input amplifier 1, the output amplifier 4, and the bias circuit 8. FM + TV 1 to 3 channel signal is 6
Since it is 0M to 130MHz, it is a low-power CM that is connected to the subsequent stage.
The OS-configured PLL + controller can be input in terms of frequency, but since it requires gain, it is amplified by the input amplifier 1 and input to the PLL + controller through the output amplifier 4.

On the other hand, when capturing the signals of TV channels _{4 to 12} , the control terminal 21 is set to the power supply voltage Vcc and the switch 5 is turned on.
The switch 6 is turned to the a side, and the switch 7 is turned off to allow a current to flow through the input amplifier 2, the 1/2 frequency divider 3, the bias circuits 8 and 9, and the output amplifier 4. The bias voltage of the input amplifier 2 and the 1/2 divider 3 is given by the bias circuit 9, and the bias voltage of the output amplifier 4 is given by the bias circuit 8. In this state, the input signal is 130 to 260MHz, and the CMOS configuration PLL + controller cannot operate at this frequency, so it is divided to 65 to 130MHz by the 1/2 divider 3 and input to the PLL + controller through the output amplifier 4. To be done.

The part surrounded by the dotted line is configured as one semiconductor integrated circuit.

〔The invention's effect〕

As described above, according to the present invention, FM with different frequency bands is used.
By separately providing the input of the signal of and TV, and controlling with the control terminal, the current is not made to flow into the unused circuit at all, and the 1/2 frequency dividing function and the amplifier function can be switched and used in the set. It has the effect of facilitating further miniaturization and low power consumption.

Further, the switching of the operation has an advantage that it can be controlled by a DC voltage.

[Brief description of drawings]

FIG. 1 is a block diagram of a prescaler according to an embodiment of the present invention, and FIGS. 2 and 3 are block diagrams on which the present invention is based. 1,2,11,12,18 …… Input amplifier, 3,13,19 …… 1/2 divider,
4,14,20 …… Output amplifier, 5,6,7,16,17 …… Switch, 8,
9 ... Bias circuit, 10 ... Ground, 15 ... IC with built-in PLL and controller, 21 ... Control terminal, 22 ...
… Power supply voltage line.

Claims (1)

(57) [Claims] 1. A first and second input amplifier and the second input amplifier.
Of the input amplifier, a first switch for switching between the outputs of the first input amplifier and the frequency divider, an output amplifier for receiving the output of the switch, and the second input A second switch provided between a power supply line and a power supply terminal of the amplifier and the frequency divider, a first bias circuit connected to the power supply terminal, an output of the first bias circuit, and the first bias circuit. A third switch provided between the first input amplifier and the bias input of the first input amplifier; a second bias circuit connected to the power supply line to apply a bias to the second input amplifier and the frequency divider; When the signal to the terminal and the control terminal is in the first state, the second and third switches are turned off and on, respectively, and the first switch is switched to the first input amplifier side. And a means for turning on and off the second and third switches, respectively, and switching the first switch to the frequency divider side when the signal is in the second state. The input amplifier is the third
Is activated by the bias from the first bias circuit depending on the ON state of the switch, the second input amplifier and the frequency divider are biased from the second bias circuit according to the ON state of the second switch. Prescaler activated by.