JPH07154286A - Pll integrated circuit - Google Patents

Abstract

PURPOSE:To form the PLL circuit for an AM/FM radio receiver usable irrespec tive of the system of its AM reception circuit, either it is of the double conver sion system or of the single conversion system. CONSTITUTION:The integrated circuit is provided with a 1st amplifier 17, a 2nd amplifier 18, a 1st changeover circuit 19 selecting an output of the 1st and 2nd amplifiers 17, 18, a programmable divider 20 frequency-dividing an output of the 1st changeover circuit 19, a reference divider 23 generating a reference signal, a 2nd changeover circuit 25 sending an output of the divider 23 and the 2nd amplifier 18 to the 1st changeover circuit 19 or the divider 23, a 1st detection means 31 detecting the conversion system of the AM reception circuit to control the 2nd changeover circuit 25, a 2nd detection means detecting the reception band and a decode means 33 decoding the output of the 1st and 2nd detection means 31, 32 to control the 1st and 2nd changeover circuits 19, 25.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PLL integrated circuit suitable for use in an AM / FM radio receiver, and particularly when the AM radio receiver circuit is used as a double conversion system or a single conversion system. However, it also relates to a PLL integrated circuit that can be used.

[0002]

2. Description of the Related Art Generally, a double conversion type A
An AM / FM radio receiver including an M radio receiving circuit and an FM radio receiving circuit includes a PLL circuit that generates a local oscillator signal for FM and a first and a second local oscillator signal for AM. It is provided with a plurality of PLL circuits and is configured as shown in FIG.

In FIG. 3, an FM reception RF signal received by an antenna during FM reception is amplified by an FM RF amplifier (1) and applied to an FM mixer (2). In the FM mixer (2), the FM received RF signal and the FM local oscillator signal generated from the FMPLL circuit (3) are mixed to generate an FMI.
An F signal is generated. After that, the FMIF signal is amplified by the FMIF amplifier (4) and then applied to the FM detector (5) for detection.

Further, during AM reception, the AM reception RF signal received by the antenna is amplified by the AMRF amplifier (6) and then generated from the AM first PLL circuit (8) in the AM first mixer (7). AM No. 1 by AM No. 1 originating signal
It is converted into an IF signal. The AM first IF signal is the AM first
The AM second mixer (10) is amplified by the IF amplifier (9).
AM generated from the AM second PLL circuit (11) at
It is converted into an AM second IF signal by the second local oscillator signal. After that, the second IF signal is amplified by the second IF amplifier (12) and then applied to the AM detector (13) to be detected.

[0005]

However, in the circuit of FIG. 3, three PLL circuits that generate local signals are used, and if these PLL circuits are simply integrated, there is a problem that the chip area increases. there were.

[0006]

The present invention has been made in view of the above points, and has at least a first VCO for generating a first station-originated signal and a second VCO for generating a second station-originated signal. In a PLL integrated circuit, a first amplifier having a first input terminal, a second amplifier having a second input terminal,
First detecting means for detecting that the AM receiving circuit is a single conversion system or a double conversion system and generating an output according to the detection result, and detecting that the receiving band is an AM band or an FM band, and Second detection means for generating an output according to the detection result; and the first detection means.
Decoding means for generating an output in accordance with the output of the second detecting means, a first switching circuit that is switched according to the output of the decoding means, and a variable frequency division ratio, and the output of the first switching circuit. , A second switching circuit that is switched according to the output of the decoding means, a divider that divides the output of the second switching circuit, a reference divider that generates a reference signal, and the programmable divider. A second phase comparator for comparing the output of the divider and the reference signal, and a second phase comparator for comparing the output of the divider and the reference signal.

[0007]

According to the present invention, the decoding means generates an output in response to the outputs of the first and second detecting means, and the output of the first amplifier is programmable via the first switching circuit according to the output of the decoding means. The output of the second amplifier is applied to the divider, and the output of the second amplifier is applied to the programmable divider or the divider via the second switching circuit according to the decoding means. The output of the programmable divider is compared with the reference signal of the reference divider in the first phase comparator, and the output of the fixed divider is compared with the reference signal in the second phase comparator.

When the AM receiving circuit is of the double conversion system, the output of the first amplifier is applied to the programmable divider and the output of the second amplifier is applied to the divider regardless of whether the AM band or the FM band is received. Applied to. When the AM receiving circuit is of the single conversion type, the output of the second amplifier is applied to the programmable divider during AM reception, and the output of the first amplifier is applied to the programmable divider during FM reception.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention, in which an AM receiving circuit is a double conversion system. In FIG. 1, (14) is a first VCO that generates an FM local signal.
(Voltage Controlled Oscillator), (15) is a second VCO for generating an AM first local oscillator signal, (16) is a third VCO for generating an AM second local oscillator signal, and (17) is a first and second VCO (1
4) and a first amplifier for amplifying the outputs of (15), (1
8) is a second amplifier for amplifying the output of the third VCO (16), (19) is a first switching circuit, (20) is a programmable divider, (21) is a reference divider,
(22) is a first phase comparator, (23) is a divider having a fixed frequency division ratio, (24) is a second phase comparator, (25)
Is a second switching circuit, (26) is a first LPF (low-pass filter), (27) is a second LPF, and (28) is a third LPF.
F, (29) is an oscillator, (30) is a third switching circuit, (3
1) is a first detecting means for detecting that the AM receiving circuit is a single conversion method or a double conversion method, (32) is a second detecting means for detecting that the reception band is FM or AM band, and (33) is Decoding means for decoding the outputs of the first and second detecting means (31) and (32), and (17) to (25) are integrated on the same substrate. The same circuits as those of the related art will be denoted by the same reference numerals as those of the related art and will not be described.

In FIG. 1, the first detecting means (31) is A
When the M receiving circuit detects that it is a double conversion system, whether the second detecting means (32) detects that the receiving band is the AM band or the FM band Second switching circuits (19) and (2
5) is switched to the illustrated state. Further, when the first detecting means (31) detects that the AM receiving circuit is of the single conversion system, the second switching circuit (25) switches to a state opposite to that shown in the drawing, but the first switching circuit (19).
When the second detection circuit (32) detects that the reception band is the FM band, it switches to the state shown in the figure, and when it detects that it is the AM band, it switches to the state opposite to that shown.

In FIG. 1, the first detection circuit (31) detects that the AM reception circuit is of the double conversion system by the control signal from the microcomputer, and the second switching circuit (25) switches to the illustrated state. . During FM reception, the FM reception RF signal received by the antenna is amplified by the FM RF amplifier (1) and then by the FM mixer (2).
The FM local signal generated from (14) is converted into an FMIF signal. The FMIF signal is an FMIF amplifier (4)
It is amplified by and is detected by the FM detector (5).

During FM reception, the second detection circuit (32) detects that the reception band is the FM band by the control signal from the microcomputer, and the third switching circuit (30) switches to the state shown in the figure. Therefore, the output of the first VCO (14) is applied to the first amplifier (17) via the third switching circuit (30) and amplified. The output of the first amplifier (17) is the first
The voltage is applied to the programmable divider (20) via the switching circuit (19), divided, and then applied to the first phase comparator (22). The output of the oscillator (29) is applied to the reference divider (21) and, after being divided, the reference signal is applied from the reference divider (21) to the first phase comparator (22). In the first phase comparator (22), the programmable divider (20)
Is compared with the phase of the reference signal, and a phase error output is generated. The error output is smoothed by the first LPF (26) and applied to the first VCO (14) as a control signal. Then, the first VCO (14) generates a first local oscillator signal having a frequency corresponding to the control signal.

Further, in the case of the double conversion system during AM reception, the AM reception RF signal received by the antenna is amplified by the AMRF amplifier (6), and then is amplified from the second VCO (15) in the AM first mixer (7). The generated AM second local signal is converted into an AM first IF signal. AM
The first IF signal is amplified by the AM first IF amplifier (9), and is amplified by the AM second mixer (10) at the third VCO (1
6) The AM second IF signal of 6) is converted. Further, the AM second IF signal is amplified by the AM second amplifier (12) and then detected by the AM detector (13).

At the time of AM reception, the second detection means (32) detects that the reception band is the AM band by the control signal from the microcomputer, and the third switching circuit (30) switches to a state opposite to that shown in the figure. In this state, the second VCO (1
The output of 5) is applied to the first amplifier (17) via the third switching circuit (30) and amplified. First amplifier (1
The output of 7) is applied to the programmable divider (20) via the first switching circuit (19) and divided.
Then, in the first phase comparator (22), the output of the programmable divider (20) is compared with the reference signal, and the error output thereof is applied to the second LPF (27).
Then, the second local oscillator signal having a frequency corresponding to the control signal from the second LPF (27) is generated from the second VCO (15). On the other hand, the output of the third VCO (16) is applied to the second amplifier (18) and amplified. Second amplifier (18)
The output of is applied to the divider (23) via the second switching circuit (25) and is divided in frequency. Then, in the second phase comparator (24), the output of the divider (23) is compared with the reference signal, and its error output is generated. The error output is smoothed by the third LPF (28) and then applied to the third VCO (16) as a control signal. Then, an AM second local oscillator signal having a frequency corresponding to the control signal is generated.

FIG. 2 is a diagram showing another embodiment of the present invention, in which the AM receiving circuit includes an AMRF amplifier (34), an AM mixer (35), an AMIF amplifier (36) and an AM detector (37). In this example, the single conversion method is used. Based on the control signal from the microcomputer, the first detecting means (31) detects that the AM receiving circuit is of the single conversion system, and the second switching circuit (25).
Switches to the illustrated state. In addition, the second detection means (3
When 2) detects that the reception band is the FM band by the control signal from the microcomputer, the first switching circuit (1
9) switches to the state shown in the figure, and when it is detected that the band is the AM band, the first switching circuit (19) switches to the state opposite to that shown in the figure.

In FIG. 2, since the same operation as the FM receiving operation of the embodiment of FIG. 1 is performed at the time of FM reception, the description will be omitted. Also, when AM is received, the AM received by the antenna
The received RF signal is amplified by the AMRF amplifier (34) and
The M mixer (35) converts the AM local oscillator signal of the second VCO (15) into an AMIF signal. The AMIF signal is
After being amplified by the AMIF amplifier (36), it is detected by the AM detector (37).

The output of the second VCO (15) is applied to the second amplifier (18) and amplified. Second amplifier (18)
Of the second switching circuit (25) and the first switching circuit (1
It is applied to the programmable divider (20) via 9) and divided. In the first phase comparator (22), the output of the programmable divider (20) is compared with the reference signal, and its error output is generated. The error output is smoothed by the second LPF (27) and applied to the second VCO (15) as a control signal. And the second V
The CO (15) generates an AM local signal having a frequency according to the control signal.

[0018]

Therefore, according to the present invention, the switching circuit is provided between the amplifier and the frequency divider, and the switching circuit is controlled according to the conversion system and the reception band of the AM receiving circuit. It is possible to reduce the number of circuits, etc., and to reduce the chip area when integrated.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing another embodiment of the present invention.

FIG. 3 is a block diagram showing a conventional example.

[Explanation of symbols]

 17 1st amplifier 18 2nd amplifier 19 1st switching circuit 20 Programmable divider 21 Reference divider 22 1st phase comparator 23 Divider 24 2nd phase comparator 25 2nd switching circuit 31 1st detection means 32 2nd detection means 33 Decoding means

Claims (1)

[Claims] 1. A first for generating at least a first local oscillator signal
A PLL integrated circuit having a VCO and a second VCO for generating a second local oscillation signal, wherein a first amplifier having a first input terminal, a second amplifier having a second input terminal, and an AM receiving circuit are a single conversion system. Alternatively, the first detection means that detects the double conversion method and generates an output according to the detection result, and detects that the reception band is the AM band or the FM band and outputs the output according to the detection result. A second detection unit that is generated, a decoding unit that generates an output according to the outputs of the first and second detection units, a first switching circuit that is switched according to the output of the decoding unit, and a variable frequency division ratio A programmable divider that divides the output of the first switching circuit, a second switching circuit that is switched according to the output of the decoding means, and the second switching circuit. A fixed divider that divides the output of the conversion circuit, a reference divider that generates a reference signal, a first phase comparator that compares the output of the programmable divider and a reference signal, and a comparison of the output of the divider and the reference signal And a second phase comparator that: