JPH07264087A - Carrier wave detector - Google Patents

Abstract

PURPOSE:To facilitate the adjustment operation of a threshold value by supplying the carrier waves of electric field strength to be the judgement reference of the presence/absence of the carrier waves to a detection means and setting a value corresponding to the electric field strength as the threshold value. CONSTITUTION:To a computer 20 for broadcasting station reception, a reception broadcasting station display device 21 for extracting a broadcasting station name and a network name during reception from the decoded signals of digital data included in the received carrier waves and displaying them is connected as well. Also, an RDS receiver is provided with a setting key 30 for setting the threshold value and signals outputted from the setting key 30 are inputted to the input/output circuit 201 of the computer 20 for the broadcasting station reception. It is possible to use an existing button such as a preset button or the like also as the setting key 30. Then, when the setting key 30 is operated, the value of electric field strength signals from the detection means for indicating the electric field strength of the carrier waves in a reception state at the time is set as the threshold value by a threshold value setting means and is used for the judgement of carrier wave detection.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carrier wave detector used in a radio receiver or the like, and more particularly to a carrier wave detector which judges the presence or absence of a carrier wave based on the electric field strength of the carrier wave.

[0002]

2. Description of the Related Art A conventional carrier wave detecting apparatus is provided with an automatic search and tuning function for automatically searching and tuning for a broadcasting station that can be favorably received when searching for a broadcasting station. When operating this function, the electric field strength of the carrier is used to determine whether or not the desired broadcast station can receive. For example, when it is desired to set a criterion that a broadcasting station can receive well when it is receivable, the electric field strength signal output from a predetermined circuit of the receiver at the minimum electric field strength that the broadcasting station can receive well. It is generally known that the same value is set as a threshold value and the threshold value is compared with the electric field strength signal output according to the carrier wave of the broadcasting station currently being received to determine whether or not reception is possible.

However, normally, between the carrier detection devices,
Even if the carrier wave has the same electric field strength, the value of the detected electric field strength signal differs depending on the error of each circuit element, and the judgment of the presence or absence of the carrier wave also differs. For example, the electric field strength of FIG. 4 is the actual carrier wave inputted from the antenna and the electric field strength signal (the carrier wave detected by the carrier wave detection apparatus x, y, z in the carrier wave detection apparatus x, y, z). Is a graph showing the relationship between the detection rectification output voltage and the like). When the electric field strength signal Vz is set as the criterion for determining whether or not reception is possible, the electric field strengths determined to be receivable in the carrier wave detectors x, y, z are Ex, Ey, Ez.
Becomes Therefore, in each carrier wave detector x, y, z, since the electric field strength of the carrier wave from which the predetermined electric field strength signal is output is different, it is desirable to judge whether or not all carrier wave detectors can receive. Difficult to do. For this reason, there is generally known a carrier wave detection device provided with an adjustment circuit for adjusting so that the same electric field strength signal is output in the case of the same electric field strength carrier wave.

FIG. 5 is a circuit diagram showing a carrier wave detecting device having a conventional adjusting circuit. The conventional carrier wave detection device is
Comparator 40 that outputs a signal indicating the presence or absence of a carrier wave
And fixed resistors R1 and R2 for dividing the power supply voltage Vcc and applying it to the inverting input terminal of the comparator 40, and fixed resistors R3 and R3 for dividing the electric field strength signal from the receiving circuit and applying it to the non-inverting input terminal of the comparator 40. It is composed of R4.

Next, the operation of the conventional carrier detecting device will be described. A threshold voltage Vz obtained by dividing the power supply voltage Vcc by the fixed resistors R1 and R2 is applied to the inverting input terminal of the comparator 40 of the carrier wave detecting device. A voltage Vs obtained by dividing the electric field strength signal by the fixed resistor R3 and the variable resistor R4 is applied to the non-inverting input terminal of the comparator 40. Therefore, when the divided voltage Vs of the electric field strength signal exceeds the threshold voltage Vz, that is, when the carrier has a field strength equal to or higher than the threshold voltage Vz, the comparator 40 outputs a signal (high potential) indicating that the carrier exists. To be done.

Next, a conventional method for adjusting the carrier wave detecting device will be described. First, the variable resistor R4 is adjusted to the lowest resistance value. Next, a signal generator is used to input a carrier wave having a minimum electric field strength that can be well received. Then, the resistance value of the variable resistor R4 is increased until the output of the comparator 40 is inverted. By performing such an adjustment, the output of the comparator 40 is inverted by the minimum value at which the electric field strength of the carrier wave can be satisfactorily received in all the adjusted carrier wave detection devices.

[0007]

However, in the carrier wave detecting device as described above, since the adjusting circuit is required, the structure is complicated and the cost is high, and the resistance value of the variable resistor R4 is delicate in the adjusting work. There is a problem that it takes a lot of time to adjust it. Therefore, in view of the above problems, an object of the present invention is to provide a carrier wave detection device that can be easily adjusted.

[0008]

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned problems, and a detecting means for detecting the electric field strength of a carrier wave and a threshold value of an electric field strength signal indicating the electric field strength of the carrier wave outputted from the detecting means. In the carrier wave detecting device including a comparing means for comparing with, a threshold setting means for setting the electric field strength signal as a threshold and a starting means for activating the threshold setting means when a setting switch is operated. It is a thing.

[0009]

According to the present invention, when the setting switch is operated, the value of the electric field strength signal from the detecting means indicating the electric field strength of the carrier wave in the receiving state at that time is set as the threshold value by the threshold value setting means. Then, after that, the set threshold value is used for determining the carrier wave detection.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An RDS of an embodiment of the present invention will be described below with reference to the drawings.
An RDS receiving device capable of receiving broadcast will be described in detail. R
DS broadcasting is a method of scanning reception by a receiver having a digital data demodulating function by transmitting digital data from a broadcasting station by duplicating digital data in a conventional FM broadcasting [while receiving a broadcasting station of a certain affiliated series in a vehicle, When the car moves to another area, the function to automatically search and receive the broadcasting stations of the same affiliated series (same program) in that area. ], Learning reception [alternative program (affiliated affiliated station)
A function that can scan the corresponding frequency band in the data reception mode even when the power is off in the radio receiver that can store the. ], Simultaneous reception with affiliated affiliated stations [In a receiver equipped with two front ends (tuning circuits), when one front end is outputting audio, the other front end broadcasts the same program. Ability to search for other affiliated affiliated stations. ]
It is to enable.

In order to realize these functions, R
For example, an identification code P such as an area code is included in the DS broadcast radio wave
I, alternative commercial frequency code AF, broadcasting station name code PS,
Data signals such as another network code ON, traffic information receiving station identification code TP, and traffic information broadcast identification code TA are superimposed. FIG. 1 shows an RD which is an embodiment of the present invention.
It is a block diagram which shows an S receiver. The carrier wave from the broadcasting station received by the antenna 11 is amplified by the amplifier 12, tuned by the front end 13, converted into an intermediate frequency, and demodulated into an audio signal by the FM detection / demodulation circuit 14, The sound quality of the volume is adjusted by the circuit 15. Then, the audio signal whose volume sound quality is adjusted is amplified by the amplifier 16 and output from the speaker 17.

Reference numeral 20 denotes a broadcasting station receiving computer,
A signal fed back from the front end 13,
For example, the front end 13 is tuned and adjusted by an electric field strength signal whose level changes according to the received carrier, or a signal instructing the reception frequency is output to the front end 13 to change the reception frequency. The broadcasting station receiving computer 20 is generally configured by using a microcomputer, and stores an input / output circuit 201, a central processing unit (CPU) 202, a processing program, and the like.
RAM 20 for storing various information such as OM 203 and frequency
4. Erasable / writable E for storing electric field strength signal
A PROM 205 and a bus 206 connecting them are provided. Further, the input / output circuit 201 has a built-in A / D converter 207 which converts an electric field intensity signal or the like into digital data.

In addition to the basic configuration of the tuner described above,
The RDS receiver is provided with an RDS signal decoder 19 which is connected to the FM detection / demodulation circuit 14 and decodes the digital data contained in the tuned carrier wave and gives it to the broadcast station receiving computer 20. A program that implements the method is stored in the ROM 203.

Also, the broadcasting station receiving computer 20
Also connected to is a reception broadcast station display 21 for extracting the broadcast station name and the network name being received from the decoded signal of the digital data included in the received carrier wave and displaying them. Further, the RDS receiver is provided with a setting key 30 for threshold setting, and the signal output from the setting key 30 is input to the input / output circuit 201 of the broadcast station receiving computer 20. . The setting key 30 for setting the threshold value can also be used as an existing button such as a preset button already provided in the RDS receiver.

Next, in the RDS receiver, the operation in which the threshold setting means sets the threshold when the switching means selects the threshold setting will be described with reference to the flowchart shown in FIG. FIG. 2 shows a process of setting a threshold value of the electric field strength for judging the presence or absence of a carrier wave performed by the broadcasting station receiving computer 20, which is executed when the power of the RDS receiver is turned on. In step S1, it is determined whether the setting key 30 for activating the threshold value setting operation has been operated. Then, when the setting key 30 is operated, the process proceeds to step S2, and when the setting key 30 is not operated, the threshold value setting process is ended. In step S2, a reception frequency instruction signal is output to the front end 13 so that the reception frequency of the RDS receiver becomes a predetermined frequency, and the process proceeds to step S3. It should be noted that this predetermined frequency coincides with the frequency of a carrier having a predetermined electric field strength given to the RDS receiver by using a signal generator for setting a threshold value. In step S3, the value of the electric field strength of the carrier wave in the receiving state, that is, the A / D converted value of the electric field strength signal from the front end 13 is read from the A / D converter 207. In step S4, the A / D conversion value of the electric field strength signal read from the A / D converter 207 is set to E.
The PROM 205 is written, the threshold value is set, and the process is completed.

Next, the working method for setting the threshold value of the RDS receiving apparatus, and the state and operation of each part of the RDS receiving apparatus at that time will be described. First, using a signal generator, a carrier having a minimum electric field strength that can be properly received is input to the front end 13 of the RDS receiver. Next, the setting key 30 is operated. Then, the reception frequency of the RDS receiver becomes the threshold setting frequency. Then, at that time, the electric field strength signal output from the front end 13, that is, the electric field strength signal corresponding to the signal strength of the carrier wave output from the signal generator is built in the input / output circuit 201 of the broadcasting station receiving computer 20. The converted A / D converter 207 converts the digital data into digital data, and the digital data is stored in the EPROM 205 as a threshold value.

By performing the threshold setting operation as described above, in all the RDS receivers that have performed the threshold setting operation, the threshold stored in the EPROM 205 becomes a value corresponding to the minimum electric field strength that can be favorably received. Next, by selecting a network which broadcasts a program desired by the listener in a certain area, the broadcasting station in the case of performing an operation of receiving a well-received broadcasting station corresponding to the selected network in the area. The processing performed by the receiving computer 20 will be described with reference to the flowchart shown in FIG.

FIG. 3 shows a tuning routine of a receiving broadcast station, which is executed after the power of the RDS receiver is turned on. When the power is turned on, in step Q1, the threshold value stored in a predetermined location of the EPROM 205 is read out, and the process proceeds to step Q2 to determine whether or not the electric field strength signal of the broadcasting station currently being received is larger than the threshold value. When the received electric field strength signal is smaller than the threshold value, the process proceeds to step Q3, and when it is larger than the threshold value, the process returns to step Q1 to repeat the above procedure. Incidentally, in order to prevent the unnecessary change of the frequency due to the temporary decrease of the electric field strength, when the decrease of the electric field strength continues for a certain period of time, the process proceeds to step Q3.

In step Q3, the search for the broadcasting station is started (the reception frequency is increased by the inter-station frequency), and then in step Q4, it is determined whether or not the broadcasting station is received. This determination is performed by the electric field strength signal, and the threshold value for the determination may be the same value as the threshold value in step Q2, but in order to maintain a stable reception state, an offset value is added to the threshold value in step Q2. It is better to use a slightly stronger electric field strength as a criterion by using the added threshold value.

Then, steps Q3 and Q4 are repeated until the broadcasting station is received, and when the broadcasting station is received, it is judged at step Q5 whether or not the broadcasting station received is RDS broadcasting. This determination is made based on the digital data from the RDS signal decoder 19. If the received broadcasting station is not the RDS broadcasting, step Q3, step Q4 and step Q5 are repeated until the RDS broadcasting is received. If the received broadcasting station is the RDS broadcasting, the process proceeds to step Q6 and is included in the RDS broadcasting. From the digital data, it is determined whether or not it is the same broadcasting station as the broadcasting station currently being received. If they are not the same broadcasting station, step Q3, step Q4, step Q5 and step Q6 are repeated until the same broadcasting station is found. Only when the same broadcasting station is found, proceed to step Q7 and the received broadcasting station information (frequency etc.)
Is executed (used when setting the reception frequency when the power is turned on again after the power is turned off), and the program of the received broadcasting station is output from the speaker 17.

Before returning from step Q4, step Q5, and step Q6 to step Q3, a step (not shown) for determining whether or not all frequency bands have been searched may be added. When the search is completed, the reception frequency may be returned to the frequency of the broadcasting station before the start of the search, and the search may be completed. As described above, in this carrier wave detection device, a carrier wave having the minimum electric field strength required for good reception of a broadcasting station is actually given to the reception device, and the value itself of the electric field strength signal of the carrier wave is used to determine the presence or absence of the carrier wave. It is set as a threshold for judgment. Therefore, in the carrier wave detection device, the electric field strength serving as a criterion for determining the presence or absence of the carrier wave is the electric field strength of the carrier wave input to the reception device when the threshold value is set. The adjustment operation can be performed by a simple operation of inputting a carrier wave having a predetermined electric field strength to the receiving device and operating the setting key 30.

[0022]

As described above, in the carrier wave detecting device of the present invention, the carrier wave having the electric field strength to be used as the criterion for the presence or absence of the carrier wave is given to the detecting means, and the setting switch is operated to change the electric field strength. Since the corresponding value is set as the threshold value, the threshold value adjustment work becomes very easy.

[Brief description of drawings]

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

FIG. 2 is a flowchart showing processing performed by the broadcasting station computer 20.

FIG. 3 is a flowchart showing a process performed by the broadcasting station computer 20.

FIG. 4 is a graph showing a relationship between a carrier wave and an electric field strength signal.

FIG. 5 is a circuit diagram showing a conventional threshold adjustment circuit.

[Explanation of symbols]

 11 antenna 17 speaker

Claims (1)

[Claims] 1. A carrier wave detecting device comprising: a detecting means for detecting an electric field strength of a carrier wave; and a comparing means for comparing an electric field strength signal indicating the electric field strength of the carrier wave outputted from the detecting means with a threshold value. A carrier wave detecting device comprising: a threshold value setting means for setting the threshold value as a threshold value; and a starting means for activating the threshold value setting means when a setting switch is operated.