JPH08340266A - Radio reception circuit - Google Patents

Abstract

PURPOSE: To provide a radio receiver for eliminating noise due to digital data while transferring the digital data. CONSTITUTION: When digital data for setting the reference value of RF-AGC and a tuning frequency are impressed to an input circuit 25, this radio receiver is set to an optimum reception state corresponding to the digital data. When the digital data are impressed to the input circuit 25, it is detected that the digital data are impressed in a detection circuit 27 by chip enable signals and muting signals are generated from a muting generation circuit 28 corresponding to the output signals of the detection circuit 27. A muting circuit 19 performs a muting operation corresponding to the muting signals and the output signals of the detection circuit 27 are muted. Thus, while transferring the digital data, the generation of the noise due to the digital data is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio receiving circuit which reduces the influence of noise caused by digital data.

[0002]

2. Description of the Related Art Conventionally, there is known a radio receiver which has a control circuit composed of a microcomputer for generating digital data and which obtains the best reception state by changing the digital data. In such a radio receiver, FIG. 2 generates frequency-divided digital data for setting the frequency of a local oscillation signal, and changes the gain of an RF amplifier circuit according to a predetermined received electric field strength. It is an example of an AM radio receiver.

In FIG. 2, a received RF signal is amplified by an RF amplifier circuit (1) and then frequency-selected by an RF tuning circuit (2). The output signal of the RF tuning circuit (2) is converted into an IF signal of 450 KHz by the local oscillation signal generated from the local oscillation circuit (4) in the mixing circuit (3), and the IF signal is further amplified by the IF amplification circuit (5). After being amplified by, it is detected by the detection circuit (5).

When the AM radio receiver shown in FIG. 1 is about to receive a desired broadcasting station, the control circuit (7) outputs a PLL signal.
The frequency division data is applied to the control circuit (8), a predetermined control signal of the PLL control circuit (8) is applied to the local oscillation circuit (4), and the predetermined frequency is output from the local oscillation circuit (4) according to the frequency division data. A local oscillator signal having a frequency is generated. The local oscillation signal is applied to the PLL control circuit (8), and the PLL loop including the local oscillation circuit (4) and the PLL control circuit (8) locks at the predetermined frequency. Further, the local oscillation signal is also applied to the mixing circuit (3), and the RF signal of the desired broadcasting station is received.
The signal is selected.

On the other hand, in the electric field strength detection circuit (9),
The electric field strength of the received signal is detected according to the output signal of the IF amplifier circuit (5). The electric field strength detection circuit (9) is smoothed by the smoothing circuit (10) and then the RF-AGC circuit (1).
1) is applied. In the RF-AGC circuit (11), the output signal of the smoothing circuit (10) is applied to the RF-AGC circuit (11) and compared with a reference value. The reference value is set according to the digital data generated from the control circuit (7). When the output signal of the smoothing circuit (10) is higher than the reference value, the output signal is generated from the RF-AGC circuit (11), the gain of the RF amplifier circuit (2) is reduced, and the RF signal of an excessive level is mixed ( Do not apply to 3).
If the output signal of the smoothing circuit (10) is smaller than the threshold value, the gain of the RF amplifier circuit (2) is not controlled.

[0006]

However, in the circuit of FIG. 2, digital data is transferred from the control circuit (7) to P
When transmitted to the LL control circuit (8) and the RF-AGC circuit (11), "1" of digital data or clock signal
And a change of "0" causes a harmonic component. Therefore, there is a problem that the harmonic component is superimposed on the tuning line and the detection line of the radio receiver, and the S / N of the detection output signal is deteriorated.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and at least in a radio receiving circuit in which a detection circuit is integrated on an IC substrate, the reception of the radio receiving integrated circuit is performed. An input terminal to which digital data for setting a state is applied, a detection circuit for detecting that the digital data is applied, and signal processing to an output signal of the detection circuit according to an output signal of the detection circuit. And a signal processing circuit for performing the above.

The signal processing circuit mutes a muting signal generating circuit for generating a muting signal in response to the output signal of the detection circuit and a muting signal for the muting signal in response to the muting signal. And a muting circuit for starting the operation. Furthermore, the signal processing circuit includes a noise removal circuit that removes a noise component in the output signal of the detection circuit, and a removal operation control circuit that causes the noise removal circuit to perform a removal operation according to the output signal of the detection circuit. It is characterized by being configured.

[0009]

According to the present invention, when digital data for setting the receiving state of the radio receiving circuit is applied to the input terminal of the radio receiving circuit, the radio receiving circuit is set to the optimum receiving state according to the digital data. To be done. When the digital data is applied to the input terminal, the detection circuit detects that the digital data is applied, and the muting generation circuit generates a muting signal according to the output signal of the detection circuit. The muting circuit performs a muting operation according to the muting signal, and the output signal of the detection circuit is muted. Therefore, it is possible to prevent the generation of noise due to the digital data during the transfer of the digital data.

Further, the removal operation control circuit operates according to the output signal of the detection circuit, the noise removal circuit operates according to the output signal of the removal operation control circuit, and the detection output superposed due to the digital data. Since noise in the signal is removed, deterioration of S / N during detection output can be prevented.

[0011]

FIG. 1 is a diagram showing an embodiment of the present invention,
(12) is an RF amplifier circuit for amplifying the received RF signal, (1
3) is an RF tuning circuit that selectively tunes the output signal of the RF amplifier circuit (12), (14) is a local oscillation circuit that generates a local oscillation signal, and (15) is a PLL control signal that controls the frequency of the local oscillation signal. A generated PLL control circuit, (16) a mixing circuit for converting the output signal of the RF tuning circuit (13) into an IF signal by a local oscillation signal, (17) an IF amplification circuit for amplifying the IF signal, and (18) a An AM detection circuit for performing AM detection on the output signal of the IF amplification circuit (17), (1
9) is a muting circuit for muting the output signal of the AM detection circuit (19), (20) is an audio amplifier for the output signal of the muting circuit (19), (21)
Is a field strength detection circuit that detects the received field strength according to the output signal of the IF amplifier circuit (17), (22) is a smoothing circuit that smoothes the output signal of the IF amplifier circuit (17), and (23) is a smoothing circuit ( 22) according to the output signal of the RF amplifier circuit (1
RF-AGC circuit for changing the gain of 2), (24) a D / A conversion circuit for generating a reference value of the RF-AGC circuit (23) according to digital data, (25) an input circuit for receiving digital data , (26) are frequency division data and R
A control circuit for generating data for setting the reference value of the F-AGC circuit (23), (27) a detection circuit for detecting that data is applied to the input circuit (26), and (28) a detection circuit. It is a muting signal generation circuit for generating a muting signal according to the output signal of (26). still,
Circuits other than the control circuit (26) are integrated into an IC on the same substrate.

Further, in FIG. 1, since the receiving operation is the same as the conventional one, the description of the receiving operation is omitted. Next, the RF-AGC operation will be described. The received electric field strength is detected by the electric field strength detection circuit (21) according to the output signal of the IF amplifier circuit (17). Electric field strength detection circuit (2
The output signal of 1) is applied to the smoothing circuit (22) and smoothed. The output signal of the smoothing circuit (22) is applied to the RF-AGC circuit (23) and compared with the reference value from the D / A conversion circuit (24). When the output signal of the smoothing circuit (22) is larger than the reference value, an output signal is generated from the RF-AGC circuit (26) to reduce the gain of the RF amplifier circuit (12), and the gain is the smoothing circuit ( It becomes a value according to the difference between the output signal of 22) and the reference value. Therefore, an excessive level of R
The F signal is prevented from being applied to the mixing circuit (16). If the output signal of the smoothing circuit (25) is smaller than the reference value, the gain of the RF amplifier circuit (12) is not controlled.

When the AM radio receiver of FIG. 1 is about to receive a desired broadcast station, frequency division data corresponding to the frequency of the desired broadcast station is input from the control circuit (26) to the input circuit (25).
Is applied to the PLL control circuit (8) via. A predetermined control signal of a PLL control circuit (7) is applied to a local oscillation circuit (4) according to the divided data, and a local oscillation signal having a predetermined frequency is output from the local oscillation circuit (4) according to the divided data. Occurs. The local oscillation signal is applied to the PLL control circuit (7), and the PLL loop including the local oscillation circuit (4) and the PLL control circuit (7) locks at the predetermined frequency. Further, the local oscillation signal is also applied to the mixing circuit (3), and the RF signal and the local oscillation signal are mixed, so that the frequency of the output signal of the mixing circuit (3) is, for example,
The RF signal at 450 KHz is selected.

Now, the operation when the data for determining the reference value of the RF-AGC circuit (23) and the divided data are transferred from the control circuit (26) to the input circuit (25) will be described. The digital data includes a data signal, a clock signal, and a chip enable signal as shown in FIG. 4, the data signal includes digital data for determining the reference value, and the chip enable signal is "when the data signal is present. It is a signal that rises to 1 ”. During data transfer, the chip enable signal changes from "0" to "1",
The data signal is transferred to the input circuit (25) via the input terminal in synchronization with the clock signal. In addition, the detection circuit (2
7) is a circuit for detecting rising or falling of the chip enable signal, which detects that the chip enable signal has changed from "0" to "1" during data transfer,
Generate an output signal. Then, a muting signal is generated from the muting signal generation circuit (28) according to the output signal of the detection circuit (27), and the AM detection circuit (18) is generated.
The output signal of is muted by the muting circuit.

On the other hand, the data transferred to the input circuit (25) are applied to the PLL control circuit (15) and the D / A conversion circuit (24), respectively, and the PLL control circuit (15) responds to the divided data. A control signal is generated, and the D / A conversion circuit (24) generates a reference value for the RF-AGC circuit (23). When the data transfer is completed, the chip enable signal falls from "1" to "0", and the detection circuit that detects this causes the generation of the output signal to be stopped. Therefore, the generation of the muting signal is stopped and the muting is released. Therefore, it is possible to prevent generation of noise due to data transfer during data transfer. The RF-AGC circuit (2
The reference value of 3) is set so that the optimum reception state can be obtained according to the destination of the radio receiver. Therefore, the threshold value can be easily changed by changing the digital data.

FIG. 3 is a diagram showing another embodiment of the present invention, in which (30) is an RF for amplifying an FM-modulated RF signal.
An amplifier circuit, (31) a local oscillator circuit for generating a local oscillator signal, (32) a mixer circuit for converting the output signal of the RF amplifier circuit (30) into an IF signal by the local oscillator signal,
(33) is an IF amplifier circuit for amplifying the IF signal, (3
4) is an FM detection circuit for performing FM detection on the output signal of the IF amplification circuit (33), (35) is an electric field strength detection circuit for detecting electric field strength according to the output signal of the IF amplification circuit (33),
(36) is a soft muting generation circuit for generating a soft muting signal according to the electric field strength, (3)
7) is a soft muting circuit for soft muting the output signal of the FM detection circuit (33), (38) is a delay circuit (39), a noise detection circuit (40), a gate signal generation circuit (41), A noise removal circuit including a gate circuit (42), a subtraction circuit (43) and a capacitor (44), (45) a multiplex circuit for multiplexing the output signal of the noise removal circuit (38), (4
6) is a D / A conversion circuit that determines the reference value of the soft muting signal generation circuit (36), (47) is a control circuit that transfers data to the D / A conversion circuit (46), and (48) is data application This is a detection circuit that detects that the operation has been performed. still,
Circuits other than the control circuit (47) are integrated on the same substrate.

The receiving operation and noise removing operation of the FM receiver shown in FIG. Next, the operation of the radio receiver shown in FIG. 3 when the electric field is weak will be described. When the electric field strength of the received signal decreases, the output signal of the electric field strength detection circuit (35) becomes lower than the reference value generated by the D / A conversion circuit (46), and the soft muting signal generation circuit (36) causes the soft muting. A signal is generated. The soft muting circuit (37) performs a muting operation in response to the soft muting signal, and mutes the output signal of the FM detection circuit (34) with a predetermined attenuation amount. Then, the attenuation amount changes according to the difference between the output signal of the electric field strength detection circuit (35) and the reference value. Therefore, by performing soft muting in a weak electric field, the noise level is also reduced so that the noise is not noticeable.

By the way, when the operation of the radio receiver is started, digital data as shown in FIG. 4 is transferred from the control circuit (47) to the D / A conversion circuit (46) through the input terminal. During data transfer, the chip enable signal changes from "0" to "1".
Since the level changes, the detection circuit (48) detects this change and the detection circuit (48) generates an output signal. Since the output signal of the detection circuit (48) applied to the gate signal generation circuit (41) of the noise removal circuit (38) is applied, a gate signal is generated during that time and the gate circuit (42) is opened. Therefore, the voltage across the capacitor (44) connected between the (+) and (−) terminals of the subtraction circuit (7) becomes the input level immediately before the gate circuit (42) is opened, so that the capacitor ( The noise generated at the output terminal of the subtraction circuit (44) is removed only from the output signal corresponding to the voltage across 44). When the data transfer is completed, the chip enable signal changes from "1" to "0" and the output signal from the detection circuit (48) stops. Therefore, the generation of the gate signal is stopped and the noise removal operation is stopped. Therefore, it is possible to prevent generation of noise due to data transfer during data transfer.

It should be noted that as shown in FIGS. 1 and 3, RF
The technique according to the present invention can be applied not only to a radio receiver that sets the tuning frequency of the AGC, the weak electric field muting and the radio receiver, but also to a radio receiver that sets other reception states with digital data. It is possible to remove noise caused by digital data.

[0020]

As described above, according to the present invention, the muting is performed during the data transfer period so that the audio output signal is not generated, so that the noise caused by the data transfer can be prevented. In addition, since the noise removal circuit is forcibly operated during the data transfer period, it is possible to remove the noise included in the audio output signal due to the data transfer and improve the S / N ratio.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a conventional example.

FIG. 3 is a block diagram showing another embodiment of the present invention.

FIG. 4 is a characteristic diagram for explaining the present invention.

[Explanation of symbols]

21, 35 Electric field intensity detection circuit 22 Smoothing circuit 23 RF-AGC circuit 24, 46 D / A conversion circuit 25 Input circuit 26, 47 Control circuit 27 Detection circuit 28 Muting signal generating circuit 36 Soft muting signal generating circuit 37 Soft mu Circuit 38, 48 Noise removal circuit

Claims (3)

[Claims] 1. A radio receiving circuit in which at least a detection circuit is integrated on an IC substrate, an input terminal to which digital data for applying a reception state of the radio receiving integrated circuit is applied, and the digital data is A radio receiving circuit comprising: a detection circuit for detecting that the voltage has been applied; and a signal processing circuit for performing signal processing on the output signal of the detection circuit according to the output signal of the detection circuit. 2. The signal processing circuit includes a muting signal generation circuit that generates a muting signal in response to an output signal of the detection circuit, and a muting signal output circuit of the detection circuit in response to the muting signal. 2. The radio receiving circuit according to claim 1, wherein the radio receiving circuit comprises a muting circuit for performing radio communication. 3. The signal processing circuit, a noise removing circuit for removing a noise component in the output signal of the detection circuit, and a removal operation control for causing the noise removal circuit to perform an operation of removal in accordance with the output signal of the detection circuit. The radio receiving circuit according to claim 1, wherein the radio receiving circuit is constituted by a circuit.