JP2001274711A - Broadcast receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of the conventional broadcast receiver that has needed mush trouble for adjustment to prevent detuning of a tuning circuit. SOLUTION: The broadcast receiver is provided with a 1st tuning circuit 11 (2nd tuning circuit 13), that controls the resonance frequency on the basis of a tuning voltage from a PLL circuit 20 to tune to a DAB broadcast signal, a 1st mixer 31 (2nd mixer 41) that generates a 1st level difference voltage corresponding to a level difference, when detecting the level difference between an input signal and an output signal of the 1st tuning circuit 11 (2nd tuning circuit 13), a 1st voltage comparator 33 (2nd voltage comparator 43) that compares a 1st reference voltage (2nd reference voltage) from a 1st reference voltage source 32 (2nd reference voltage source 42) with the 1st level difference voltage and detects the level difference as a 2nd level difference voltage, when detecting the level difference between the 1st level difference voltage and the 1st reference voltage (2nd reference voltage), and a 1st adder 34 (2nd adder 44) that corrects the tuning voltage on the basis of the 2nd level difference voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital audio broadcasting system having a tuning circuit for controlling a resonance frequency based on a tuning voltage to tune a broadcast signal of, for example, digital audio broadcasting (hereinafter, simply referred to as DAB) broadcast.
The present invention relates to a broadcast receiving device such as an AB receiver.

[0002]

2. Description of the Related Art Conventionally, there is a DAB receiver having the following front end. FIG. 2 is a block diagram showing a schematic configuration inside a front end in a conventional DAB receiver.

[0003] A front end 100 of a DAB receiver shown in FIG. 2 includes a first tuning circuit 101 for performing a first tuning process on a DAB broadcast signal received from a receiving antenna (not shown). 1 DA with synchronization processing
An AGC amplifier 102 for adjusting the gain of the B broadcast signal;
A second tuning circuit 103 that performs a second tuning process on the DAB broadcast signal whose gain has been adjusted by the AGC amplifier 102, and a DA that has been subjected to the second tuning process by the second tuning circuit 103.
A mixer 104 that converts the DAB broadcast signal into an intermediate frequency signal by mixing the B broadcast signal with a local oscillation frequency from a PLL circuit 110 described later, and outputs the intermediate frequency signal to a stage subsequent to the front end. AGC control circuit 10 that generates an AGC control voltage for controlling AGC amplifier 102 by DC-converting the intermediate frequency signal
5 and a PLL circuit 110 that generates a tuning voltage and a local oscillation frequency to the mixer 105 necessary for the first tuning process of the first tuning circuit 101 and the second tuning process of the second tuning circuit 103.

A PLL circuit 110 includes a reference oscillator (hereinafter simply referred to as OSC) 111 for generating a reference signal, a first frequency divider 112 for dividing the reference signal based on a fixed frequency division ratio, and a tuning circuit. A local oscillator (hereinafter, simply referred to as a VCO) 11 that generates a local oscillation frequency based on a voltage
3, a second divider 114 for dividing the local oscillation frequency based on a division ratio set by a microcomputer (not shown), an output signal of the first divider 112 and an output signal of the second divider 114 , And outputs a phase difference signal of these output signals, and an LPF 116 that generates a tuning voltage based on the phase difference signal.

[0005] The first tuning circuit 101 employs the following circuit configuration. FIG. 3 is an explanatory diagram showing a circuit configuration inside the first tuning circuit 101.

A first tuning circuit 101 shown in FIG. 3 includes a tuning coil (L) 101a, a variable capacitance diode (VD) 1
01b and a capacitor (C) 101c.

The first tuning circuit 101 is a PLL circuit 1
By changing the combined capacitance of the variable capacitance diode (VD) 101b and the capacitor (C) 101c in accordance with the tuning voltage from 10, the tuning coil (L) 10
1a through the tuning frequency (f = 1 / (2π√ (L
C))).

The first tuning circuit 101 includes a PLL circuit 1
A tuning frequency is generated based on the tuning voltage from 10, and a DAB broadcast signal received from a receiving antenna (not shown) is tuned based on the tuning frequency.

The second tuning circuit 103 also employs the same circuit configuration as the first tuning circuit 101 shown in FIG.

The second tuning circuit 103 includes a PLL circuit 1
A tuning frequency is generated based on the tuning voltage from 10, and the DAB broadcast signal whose gain has been adjusted by the AGC amplifier 102 is tuned based on the tuning frequency.

As described above, according to the front end 100 of the conventional DAB receiver, the tuning frequencies in the first tuning circuit 101 and the second tuning circuit 103 are generated based on the tuning voltage from the PLL circuit 110, and this tuning is performed. The DAB broadcast signal is tuned based on the frequency, and the DAB broadcast signal tuned by the second tuning circuit 103 and the PLL circuit 11 are tuned.
The intermediate frequency signal is generated by mixing the local oscillation frequency from zero.

At this time, if the tuning of the first tuning circuit 101 (the second tuning circuit 103) is correctly performed, the tuning frequency of the first tuning circuit 101 (the second tuning circuit 103) becomes
As shown by the solid line A, the frequency coincides with the desired frequency of the DAB broadcast signal.

However, the first tuning circuit 101 (second
When the tuning of the tuning circuit 103) is shifted, the tuning frequency of the first tuning circuit 101 (the second tuning circuit 103) is shifted from the desired frequency of the DAB broadcast signal as shown by a broken line B in FIG. If the output level decreases and an interference signal is generated in the vicinity of the output level, the signal is easily affected by the interference signal.

Therefore, in order to cope with such a situation, in the manufacturing process of the DAB receiver, the tuning coil (L) 101a is manually operated so as to obtain the same selection characteristic at each reception frequency in each frequency band. The adjustment prevents the first tuning circuit 101 (the second tuning circuit 103) from causing a tuning deviation.

[0015]

However, according to the conventional DAB receiver, the first tuning circuit 101 (second
The tuning coil (L) 101a is manually adjusted so that the tuning deviation of the tuning circuit 103) does not occur. However, since this adjusting operation requires frequency adjustment of several points, it is a very complicated operation. In addition, there is a problem in that the adjustment is manually performed, so that the adjustment varies.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a broadcast receiving apparatus capable of reliably preventing a tuning deviation of a tuning circuit without requiring an adjusting operation. To provide.

[0017]

According to the present invention, there is provided a broadcast receiving apparatus having a tuning circuit for controlling a resonance frequency based on a tuning voltage and tuning to a broadcast signal. Comparing the input signal of the tuning circuit with the output signal of the tuning circuit, and detecting a level difference between the input signal and the output signal to generate a first level difference voltage corresponding to the level difference. Level monitoring means, a second level monitoring means for comparing the first level difference voltage with a reference voltage, and detecting a level difference between the first level difference voltage and the reference voltage as a second level difference voltage; Correction means for correcting the tuning voltage based on the two-level difference voltage.

Therefore, according to the broadcast receiving apparatus of the present invention,
A first level difference voltage corresponding to a level difference between an input signal and an output signal of the tuning circuit is compared with, for example, a reference voltage in a state where there is no tuning deviation, and the level difference between the first level difference voltage and the reference voltage is determined. Since the tuning voltage is corrected based on the second level difference voltage by detecting it as the second level difference voltage, the adjustment operation is automated without the need for manual adjustment work as in the related art. As a result, it is possible to reliably prevent the tuning deviation of the tuning circuit.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a DAB receiver showing an embodiment in a broadcast receiving apparatus of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a front end in the DAB receiver shown in the present embodiment.

A front end 10 of the DAB receiver shown in FIG. 1 includes a first tuning circuit 11 for performing a first tuning process on a DAB broadcast signal received from a receiving antenna (not shown). (1) an AGC amplifier 12 for adjusting the gain of the DAB broadcast signal subjected to the tuning process,
A second tuning circuit 13 that performs a second tuning process on the DAB broadcast signal whose gain has been adjusted by the C amplifier 12, a DAB broadcast signal that has been subjected to the second tuning process by the second tuning circuit 13, and a PLL circuit to be described later. The mixer 14 converts the DAB broadcast signal into an intermediate frequency signal by mixing it with the local oscillation frequency from the mixer 20, and outputs the intermediate frequency signal to the subsequent stage of the front end. An AGC control circuit 15 for generating an AGC control voltage for controlling the AGC amplifier 12 and a first tuning circuit 11
And a PLL circuit 20 for generating a tuning voltage and a local oscillation frequency to the mixer 14 necessary for the first tuning process and the second tuning process of the second tuning circuit 13.

The PLL circuit 20 generates an O signal for generating a reference signal.
SC21, a first frequency divider 22 for dividing the reference signal based on a fixed frequency division ratio, a VCO 23 for generating a local oscillation frequency based on a tuning voltage, and a frequency division ratio set by a microcomputer (not shown) , The phase of the output signal of the first frequency divider 22 and the phase of the output signal of the second frequency divider 24 are compared, and the phase difference signal of these output signals is compared. And an LPF for generating a tuning voltage based on the phase difference signal
26.

The front end 10 receives a DAB broadcast signal which is an input signal of the first tuning circuit 11 and a tuned DAB broadcast signal which is an output signal of the first tuning circuit 11, and receives these input signal and output signal. A first mixer 31 that detects a difference in amplitude level between the two and generates a first level difference voltage corresponding to the difference in amplitude level, a first reference voltage source 32 that generates a first reference voltage described later, and a first mixer The first level difference voltage from the first reference voltage source 31 and the first reference voltage from the first reference voltage source 32 are compared, and the level difference between the first level difference voltage and the first reference voltage is detected as a second level difference voltage. 1
It has a voltage comparator 33 and a first adder 34 that adds the second level difference voltage detected by the first voltage comparator 33 to the tuning voltage from the PLL circuit 20.

The first mixer 31 detects an amplitude level difference between the input signal and the output signal by performing a multiplication process on the input signal and the output signal having the same frequency.

The first reference voltage source 32 is connected to the first tuning circuit 11
A voltage corresponding to a level difference between an input signal and an output signal of the first tuning circuit 11 in a state where there is no tuning deviation in the above, and this voltage value is stored as a value of a first reference voltage. And

The front end 10 also includes a DAB broadcast signal whose gain is adjusted by the AGC amplifier 12 as an input signal of the second tuning circuit 13 and a tuned DAB broadcast signal which is an output signal of the second tuning circuit 13. To detect the amplitude level difference between the input signal and the output signal, and to generate a first level difference voltage corresponding to the amplitude level difference.
The mixer 41, a second reference voltage source 42 that generates a second reference voltage described later, and a first level difference voltage from the second mixer 41 and a second reference voltage from the second reference voltage source 42 are compared. A second voltage comparator 43 for detecting a level difference between the first level difference voltage and the second reference voltage as a second level difference voltage, and a second level difference voltage detected by the second voltage comparator 43 as a PLL. And a second adder 44 for adding to the tuning voltage from the circuit 20.

The second mixer 41 detects an amplitude level difference between the input signal and the output signal by multiplying the input signal and the output signal having the same frequency.

The second reference voltage source 42 is connected to the second tuning circuit 13
A voltage corresponding to a level difference between an input signal and an output signal of the second tuning circuit 13 in a state where there is no tuning deviation in the above is measured in advance, and this voltage value is stored as a value of a second reference voltage. And

Next, the operation of the DAB receiver shown in this embodiment will be described.

When turning on the power of the DAB receiver and receiving a DAB broadcast signal, the first tuning circuit 12 generates a tuning frequency corresponding to a desired frequency based on the tuning voltage from the PLL circuit 20, and generates the tuning frequency. The DAB broadcast signal received from the receiving antenna is tuned based on the frequency, and the tuned DAB broadcast signal is transmitted to the AGC amplifier 12.

The first mixer 31 receives an input signal and an output signal of the first tuning circuit 11, and multiplies the input signal and the output signal to detect an amplitude level difference between the input signal and the output signal. Then, a first level difference voltage corresponding to the amplitude level difference is generated, and the first level difference voltage is input to the first voltage comparator 33.

The first voltage comparator 33 includes a first reference voltage source 3
Comparing the first reference voltage and the first level difference voltage from
When it is determined that there is a level difference between the first reference voltage and the first level difference voltage, the level difference is determined by the first tuning circuit 1.
The level difference is determined as the tuning deviation at 1, and this level difference is transmitted to the first adder 34 as a second level difference voltage.

The first adder 34 generates a first correction tuning voltage by adding a second level difference voltage for correcting a tuning shift in the first tuning circuit 11 to a tuning voltage from the PLL circuit 20. The first correction tuning voltage is transmitted to the first tuning circuit 11.

The first tuning circuit 11 generates a tuning frequency based on the first correction tuning voltage, tunes the DAB broadcast signal received from the receiving antenna based on the tuning frequency, and adjusts the tuned DAB broadcast signal. AG
The signal is transmitted to the C amplifier 12. The AGC amplifier 12 adjusts the gain of the tuned DAB broadcast signal, and transmits the gain-adjusted DAB broadcast signal to the second tuning circuit 13.

The second tuning circuit 13 includes a PLL circuit 20
A tuning frequency corresponding to a desired frequency is generated based on the tuning voltage from
A second tuning process is performed on the DAB broadcast signal whose gain has been adjusted by the C amplifier 12, and the tuned DAB broadcast signal is transmitted to the mixer 14.

The second mixer 41 receives an input signal and an output signal of the second tuning circuit 13 and multiplies the input signal and the output signal, thereby detecting an amplitude level difference between the input signal and the output signal. Then, a first level difference voltage corresponding to the amplitude level difference is generated, and the first level difference voltage is input to the second voltage comparator 43.

The second voltage comparator 43 includes a second reference voltage source 4
Comparing the second reference voltage and the first level difference voltage from
When it is determined that there is a level difference between the second reference voltage and the first level difference voltage, the level difference is determined by the second tuning circuit 1.
3 is determined, and this level difference is transmitted to the second adder 44 as a second level difference voltage.

The second adder 44 generates a second correction tuning voltage by adding a second level difference voltage for correcting a tuning deviation in the second tuning circuit 13 to a tuning voltage from the PLL circuit 20. The second correction tuning voltage is transmitted to the second tuning circuit 13.

The second tuning circuit 13 generates a tuning frequency based on the second correction tuning voltage, and tunes the DAB broadcast signal whose gain has been adjusted by the AGC amplifier 12 based on the tuning frequency.

According to the present embodiment, the first tuning circuit 11
A first level difference voltage is generated based on a level difference between an input signal and an output signal of the (second tuning circuit 13), and the first level difference voltage is compared with a first reference voltage (second reference voltage). If it is determined that there is a level difference between the first level difference voltage and the first reference voltage (second reference voltage), this level difference is used as the tuning deviation in the first tuning circuit 11 (second tuning circuit 13). Judge,
This level difference is used as a second level difference voltage, and the PLL circuit 20
The first correction tuning voltage (second correction tuning voltage) is generated by adding the second level difference voltage for correcting the tuning deviation of the first tuning circuit 11 (second tuning circuit 13) to the tuning voltage from. This first correction tuning voltage (second correction tuning voltage) is supplied to the first tuning circuit 11.
(Second tuning circuit 13), so that the adjustment work can be automated without the need for manual adjustment work as in the prior art, and the first tuning circuit 11 (second tuning circuit 13) can be adjusted. Synchronization deviation can be reliably prevented.

[0040]

According to the broadcast receiving apparatus of the present invention configured as described above, the first level difference voltage corresponding to the level difference between the input signal and the output signal of the tuning circuit, for example, a state in which there is no tuning shift To the reference voltage at
Since the level difference between the level difference voltage and the reference voltage is detected as the second level difference voltage, the tuning voltage is corrected based on the second level difference voltage.
By automating the adjustment work without requiring the manual adjustment work as in the related art, it is possible to reliably prevent the tuning shift of the tuning circuit.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration inside a front end in a DAB receiver showing an embodiment in a broadcast receiving apparatus of the present invention.

FIG. 2 is a block diagram showing a schematic configuration inside a front end in a conventional DAB receiver.

FIG. 3 is an explanatory diagram showing a circuit configuration inside a general tuning circuit.

FIG. 4 is an explanatory diagram showing tuning characteristics of a general tuning circuit.

[Explanation of symbols]

 11 first tuning circuit (tuning circuit) 13 second tuning circuit (tuning circuit) 31 first mixer (first level monitoring means) 32 first reference voltage source (second level monitoring means) 33 first voltage comparator (first 2 level monitoring means) 34 1st adder (correction means) 41 2nd mixer (1st level monitoring means) 42 2nd reference voltage source (2nd level monitoring means) 43 2nd voltage comparator (2nd level monitoring means) ) 44 Second adder (correction means)

Continued on the front page F-term (reference) 5K020 DD22 EE01 FF00 GG04 HH02 HH11 JJ01 LL01 LL06 5K058 AA10 AA12 BA08 CA02 CA04 CA05 CA15 DA01 DA14 EA08 EA17 GA01 GA04 GA08 GA11 GA13 5K061 AA08 BB01 BB06 CC12 AB05 AC02 AC07 AD08 AD09 BB06 BB10 BB13 BC02 BC08 BC11 BE08

Claims (1)

[Claims] 1. A broadcast receiving apparatus having a tuning circuit for controlling a resonance frequency based on a tuning voltage and tuning to a broadcast signal, comprising comparing an input signal of the tuning circuit with an output signal of the tuning circuit. Detecting a level difference between the input signal and the output signal, a first level monitoring unit that generates a first level difference voltage corresponding to the level difference, and compares the first level difference voltage with a reference voltage; A second level monitoring unit that detects a level difference between the first level difference voltage and the reference voltage as a second level difference voltage; and a correction unit that corrects the tuning voltage based on the second level difference voltage. A broadcast receiving apparatus characterized by the above-mentioned.