JPS63311813A - Synthesizer receiver - Google Patents

Abstract

PURPOSE:To detect the presence or absence of a broadcast signal surely without the effect of a disturbing wave or the like by selecting a step frequency of a PLL circuit as a narrow frequency interval more than that of a channel step frequency, detecting the signal level of an intermediate frequency amplifier circuit so as to judge the presence or absence of the broadcast signal. CONSTITUTION:A PLL circuit 3 swept by the step frequency, a front end circuit 2 receiving the output signal of the circuit 3, receiving the broadcast signal and converting the broadcast signal into the intermediate frequency signal, and the intermediate frequency amplifier circuit 5 receiving the intermediate frequency signal outputted from the circuit 2, are provided. The PLL circuit 3 is controlled by the signal level obtained at the circuit 5 to select the step frequency of the PLL circuit 3 as the narrower frequency interval than that of the channel step frequency, the signal level of the intermediate amplification circuit 5 is detected to judge the presence or absence of the broadcast signal. Thus, the degree of modulation of a carrier of the broadcast signal is measured and whether or not the signal detected is the broadcast signal is judged depending on the degree of modulation to detect the broadcast signal surely.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a synthesizer receiver suitable for use in an FM receiver.

[Summary of the invention]

The present invention is a synthesizer receiver suitable for use in an FM receiver, which includes a PLL circuit that is swept at a step frequency, an output signal of the PLL circuit, and a broadcast signal. It has a front end circuit that converts it into an intermediate frequency signal, and an intermediate frequency amplification circuit to which the intermediate frequency signal output from this front end circuit is supplied, and controls the PLL circuit depending on the signal level obtained from this intermediate frequency amplification circuit. In this synthesizer receiver, the step frequency of the PLL circuit is set at a narrower frequency interval than the channel step frequency, and the presence or absence of a broadcast signal is determined by detecting the signal level of the intermediate frequency amplification circuit. , the presence or absence of a broadcast signal can be reliably detected without being affected by harmful waves or the like.

[Conventional technology]

Conventionally, when receiving FM broadcasts with an FM receiver, instead of receiving a broadcast signal of a preset frequency as a channel selection operation, the reception frequency is changed by operating the reception frequency up or down key of the receiver. There have been cases in which the frequency is raised or lowered in sequence, and the rising or lowering is automatically stopped at a frequency at which a broadcast signal can be obtained, and the broadcast signal of this frequency is received. When performing such channel selection, the frequency of the local excavation signal supplied to the front-end circuit is changed every 100 KHz, which is the channel step frequency of the FM broadcast signal, and then converted into an intermediate frequency signal by an intermediate frequency amplifier circuit. When a signal of a predetermined level or higher corresponding to the carrier wave of a broadcast signal is detected, the local excavation signal stops changing, and a broadcast signal of a frequency that is converted into an intermediate frequency signal by this local oscillation signal is received.

[Problem to be solved by the invention] However, when selecting stations in this way, the intermediate frequency amplification circuit detects interference waves from adjacent stations by mistake as carrier waves of broadcast signals, and I often ended up using a receiver on a frequency where there was no broadcast signal available.

In view of the above, an object of the present invention is to provide a synthesizer receiver that can reliably detect only broadcast signals without being affected by interference waves or the like.

[Means for solving problems]

The synthesizer receiver of the present invention includes, for example, as shown in FIG. 1, a PLL circuit (3) that is swept at a step frequency;
A front-end circuit (2) is supplied with the output signal of the PLL circuit (3) and is also supplied with a broadcast signal and converts the broadcast signal into an intermediate frequency signal, and an intermediate frequency signal outputted from the front-end circuit (2). an intermediate frequency amplification circuit (51) to which an intermediate frequency amplification circuit (51) is supplied.
In a synthesizer receiver that controls the PLL circuit (3) depending on the signal level obtained from the PLL circuit (3),
The step frequency of 3) is set at a narrower frequency interval than the channel step frequency, and the presence or absence of a broadcast signal is determined by detecting the signal level of the intermediate frequency amplification circuit (5).

[Effect]

According to the synthesizer receiver of the present invention, the step frequency of the output signal is set to 20 KHz, which is narrower than the channel step frequency of a broadcast signal of 100 KHz, for example.
The degree of modulation of the carrier wave of a broadcast signal can be measured, and based on this degree of modulation, it can be determined whether the detected signal is a broadcast signal, and the broadcast signal can be reliably detected.

〔Example〕

Hereinafter, one embodiment of the synthesizer receiver of the present invention will be described with reference to the accompanying drawings.

The receiver of this example is a synthesizer receiver for FM broadcast reception using a PLL circuit, and is configured as shown in FIG.

In this Figure 1, (11 indicates an antenna, and the front end circuit (
2). Also, this front end circuit (2)
is a microcomputer (hereinafter referred to as CPU) (
4) is connected to a PLL circuit (3) in which the oscillation frequency of the output signal is controlled by the front end circuit (2).
), the frequency signal supplied from the PLL circuit (3) is superimposed on the signal supplied from the antenna (1), and the FM broadcast signal of a predetermined frequency is converted into an intermediate frequency signal of 1O11017. At this time, in this example, the step frequency of the oscillation signal output from the PLL circuit (3) is 20KH2,
This allows the reception frequency of broadcast signals to be changed for each KHz. The intermediate frequency signal output from this front end circuit (2) is then supplied to an intermediate frequency amplification circuit (5). This intermediate frequency amplification circuit (5) is a circuit that amplifies an intermediate frequency signal, detects a carrier wave, etc., and the intermediate frequency signal outputted from this intermediate frequency amplification circuit (5) is sent to an FM detector (6).
The FM detector (6) performs FM demodulation. Then, this FM demodulated received signal is supplied to an FM stereo demodulator (7), which separates it into a left audio signal and a right audio signal, and converts each separated signal into a left audio signal. Output terminal (8L) and right audio signal output terminal (
8R).

Also, the intermediate frequency amplification circuit (5) supplies the CPU (4) with a detection signal of the carrier wave of the received FM broadcast signal.
P tJ (41 determines the detection state of this carrier wave and controls the receiving operations of the PLL circuit (3), intermediate frequency amplification circuit (5), FM detector (6), etc. to ensure good FM broadcast reception. I try to do it.

Next, the operation of receiving data using the synthesizer receiver of this example will be explained with reference to FIGS. It is necessary to conduct a station.

In this example, this channel selection is performed by operating a receiving frequency amplifier key or a receiving frequency down key (not shown) provided in the receiver. That is, for example, when the reception frequency up key is operated, the CP Ll 14) changes to the PLL circuit (
By controlling the output oscillation signal of 3), the front end circuit (
2) Increase the receiving frequency.

At this time, the reception frequency is increased every 20 KHz, which is the step frequency of the PLL circuit (3), and the state of the carrier detection signal output by the intermediate frequency amplification circuit (5) at each reception frequency is set to a predetermined value by the CPU 14). Detected 10 times at intervals. Then, the detection state of carrier waves at intervals of 20 Hz is determined every 100 KHz, and it is determined whether reception is to be performed at this frequency.

For example, as shown in Figure 2, 80.00 MHl (A1
point), from this point A1 to point 2.
80.02 MHz at 0 KHz intervals (A 2 points),
80.04 MHz (A 3 points), 80.06
MHL (A4 points), 80.08 Mllz (A
s point) and the next broadcast may be taking place.80.
10M) Reception is performed until just before lz.

Then, the CPU (41) judges whether or not there is a carrier wave 10 times based on the carrier wave detection signal at each reception frequency from the AL point to the A5 point, as shown in the flowchart of FIG. (It is stored in the memory in 41. At this time, when it is detected that there is a carrier wave more than 8 times out of 10 at point A1, the above-mentioned points A2 and A3 adjacent to this point A1 and points before A1 79.98MHz
(Xs point) , 79.96 MHL (X4 points)
Based on the detection state of the carrier wave when receiving the frequency, it is determined whether the detected signal is a normal broadcast signal.

That is, at A2 point and X5 point before and after A1 point, 80.0
When it is detected that the carrier wave of 0 Mllz is shifted due to modulation and is carried 3 or more times out of 10 times, it is judged that there is a normal broadcast signal, and then the A3 point and X4 point adjacent to this A2 point and X5 point are detected. Then, similarly, 80.00 MHz
The carrier wave of is shifted by modulation and 2 out of 10 times I
When detecting the B transmission, it is determined that there is a normal broadcast signal. In this way, the carrier wave is detected at point A1.
8 out of 0 times, 3 out of 10 times with A2 and X5, 2 out of 10 times with A3 points and
It is determined that normal FM broadcasting is being performed on
This 80.00 Mll is controlled by CPU (4).
z to receive FM broadcasts.

Then, when the carrier wave is not detected more than 8 times out of 10 at the A4 point, or even if the carrier wave is detected more than 8 times at the A1 point, this A
When it is determined that there is no broadcast signal that satisfies the above conditions at any of the points X4, XS, A2, and A3 adjacent to one point, the
8 of 1 iJ possible frequency) where the broadcast signal is next to the point
Receive at 0.10 MHz (Bt point).

At this time, as in the case of 80.00M) Iz mentioned above, 80.12 Mllz (82 points), 80.14
Reception is also performed at MH2 (83 points), 80.16 MHl (84 points), and 80.18 MHz (Bs point), and when a carrier wave is detected 10 times or more at 81 points, A4 point adjacent to this B1 point , detecting carrier waves at points A5, 82, and 83 determines whether or not normal FM broadcasting is being performed under the same conditions as in the case of frequencies adjacent to point A1 described above. When it is determined that 81 points (
80, 10MHz) to receive FM broadcasts.

If normal FM broadcasting cannot be received even with this 80.10 MHz, the H
Reception is performed at 80.20 MHl (point C1) on z, and 80.22 MHz (point C1) adjacent to this point
C2 points), 80.24 M)! 2 (C3 points) and 8
A1 point, B1 point depending on the carrier wave detection state at 4 points and 85 points
In the same way as above, it determines whether normal FM broadcasting can be received or not, and if it determines that FM broadcasting is being performed, it receives it, and if it determines that FM broadcasting is not being performed, it receives a higher frequency. Do the following.

In this way, when the reception frequency up key is not operated, the reception frequency is increased until it is determined that normal FM broadcasting is being performed, and when a frequency where FM broadcasting is detected, this detected frequency is used. Perform reception.

Also, when the reception frequency down key is operated, the reception frequency is lowered in order, contrary to the above example, until it reaches 20KHz.
The reception frequency is lowered until it is determined that normal FM broadcasting is being performed by detecting each carrier wave.

As described above, according to the synthesizer receiver according to this example, F
100, which is the channel step frequency of the M broadcast signal.
K)! Reception is performed every 2 (lKIlz) narrower than z,
Since the degree of carrier wave modulation is detected from the reception status of adjacent frequencies, it is possible to reliably determine whether the signal is a normal FM broadcast signal or a signal other than a broadcast signal such as an interference wave, and the broadcast signal can be received normally. There is an advantage to being able to ensure that you only receive the following.

In the above embodiment, the synthesizer receiver is used for receiving FM broadcasts, but it goes without saying that the present invention can also be applied to synthesizer receivers that receive other broadcast signals such as AM broadcasts. For example, in the case of an AM receiver, reception is performed every I KHz, which is narrower than the frequency interval of 9 KHz for AM broadcast signals, and the degree of modulation of the carrier wave is determined from the detection state of the carrier wave at each receiving frequency. It is possible to detect whether there is a normal AM broadcast signal. Furthermore, it goes without saying that the present invention is not limited to the above-mentioned embodiments, and can take various other configurations without departing from the gist of the present invention.

〔Effect of the invention〕

According to the synthesizer receiver of the present invention, it is possible to reliably detect broadcast signals without being affected by interference waves, etc., and there is an advantage that good tuning can be performed.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the synthesizer receiver of the present invention, and FIGS. 2 and 3 are diagrams for explaining the example in FIG. 1, respectively. (2) is the front end circuit, (3) is the PLL circuit, (
4 is a microcomputer, and (5) is an intermediate frequency amplification circuit.

Claims (1)

[Scope of Claims] A PLL circuit that is swept at a step frequency, a front-end circuit to which an output signal of the PLL circuit is supplied as well as a broadcast signal and converts the broadcast signal into an intermediate frequency signal, and the front-end circuit. In the synthesizer receiver, the synthesizer receiver has an intermediate frequency amplification circuit to which an intermediate frequency signal outputted by the circuit is supplied, and the PLL circuit is controlled depending on the signal level obtained in the intermediate frequency amplification circuit, the PLL circuit being controlled by the PLL circuit. A synthesizer receiver characterized in that the step frequency of the circuit is set at a narrower frequency interval than the channel step frequency, and the presence or absence of a broadcast signal is determined by detecting the signal level of the intermediate frequency amplification circuit.