JPH0595518A - Receiver - Google Patents

Abstract

PURPOSE:To obtain the base band output of a constant amplitude value to input signals with different modulation degree in a satellite broadcasting receiver. CONSTITUTION:A high frequency signal inputted from an input terminal 1 is converted into an intermediate frequency signal by a tuner part 4. After the band is limited by a filter part 5, it is inputted to a demodulation part 6. The inputted signal is converted into a base band signal(for example FM modulation), amplified and inputted to a gain control amplification part 7, and outputted from an output terminal 2. In this case, the gain of the gain control amplification part 7 arranged on the output stage of the base band signal is controlled by the control signal inputted from the outside to a control signal input terminal 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency receiver including a satellite broadcasting front end.

[0002]

2. Description of the Related Art As an example of a conventional satellite broadcasting front end, a technical report Vol. 14, No.
6 (January 25, 1990, pp. 53-58), there is a small IC front end for satellite broadcasting tuner. The front end is equipped with an amplifier at the output stage of the baseband signal of the demodulation circuit.

[0003]

In the above-mentioned conventional front end, when signals having different modulation factors are input to the input signal, the baseband output signal of the front end has an output amplitude proportional to the input modulation factor. Therefore, when a signal with a different degree of modulation is input to the circuit connected to the latter stage of the front end, the baseband output amplitude of the front end changes, so that the circuit gain corresponding to the output amplitude changes each time the input signal changes. It is necessary to set.

[0004]

The above-mentioned problem is that a gain control circuit for controlling the output level of the baseband signal is provided at the output stage of the baseband signal of the demodulation circuit, and the gain of the gain control circuit is externally adjusted. The problem can be solved by controlling with an input control signal.

[0005]

The gain control amplifier circuit is arranged in the output stage, and the modulation is performed by changing the gain control amount of the gain control circuit provided in the output stage of the baseband signal of the demodulation circuit in accordance with an external control signal such as a keyed pulse. A constant output amplitude is always obtained for input signals with different degrees, the circuit connected to the latter stage of the front end can be simplified, and the degree of freedom in design is increased.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a block diagram showing an embodiment of a receiver using the present invention. In FIG. 1, 1 is a high frequency signal input terminal, 2 is a baseband signal output terminal, 3 is a control signal input terminal, and 4 is a tuner section for selecting a high frequency input signal input from a signal input terminal and converting it to an intermediate frequency signal. Reference numeral 5 denotes a bandpass filter unit that limits the signal bandwidth of the converted intermediate frequency signal, 6 a demodulation unit that demodulates the intermediate frequency signal into a baseband signal, and 7 controls the amplitude value of the demodulated baseband signal. It is a gain control amplifier. The operation of the receiver of FIG. 1 will be described. The high frequency signal input from the input terminal 1 is converted into an intermediate frequency signal by the tuner unit 4, band-limited by the filter unit 5, and then demodulated by the demodulation unit 6.
Entered in. The input signal is converted into a baseband signal (for example, FM demodulation), and then the gain control amplifier 7
Is input, amplified, and output from the output terminal 2.
Here, the gain of the gain control amplification unit 7 arranged at the output stage of the baseband signal is controlled by the control signal externally input to the control signal input terminal 3. That is, the fluctuation of the output amplitude value due to the change of the modulation degree of the input signal can be always tracked and corrected by the gain control amplification section 7 arranged at the output, so that the modulation degree of the input signal can be corrected. Regardless of the above, a constant output amplitude can be maintained. For example, when two signals with different modulation degrees are received, the gain control amplification unit 7 changes the baseband output depending on the reception state (modulation degree) by switching the control amount set in advance by the control signal. By controlling the gain, a constant output amplitude can be obtained.

Next, another embodiment of the present invention will be described with reference to FIG. FIG. 2 is a block diagram showing an embodiment of a receiver using the present invention. Reference numeral 9 is a keyed pulse input terminal.
FIG. 2 shows an embodiment in which a keyed pulse is used as the external control signal in the embodiment of FIG. The operation of the receiver shown in FIG. 2 will be described. The high frequency signal input from the input terminal 1 is converted into an intermediate frequency signal by the tuner unit 4,
After being band-limited by the filter unit 5, it is input to the demodulation unit 6. The input signal is FM-demodulated into a baseband signal, input to the gain control amplification unit 7, amplified, and output from the baseband output terminal 2. Here, the gain of the gain control amplification unit 7 arranged at the output stage of the baseband signal is controlled by the keyed pulse signal externally input to the keyed pulse input terminal 9. That is, when the same receiver receives signals of different modulation levels of the NTSC system and the MUSE system, the reception is performed by switching the control amount preset in the gain control amplification unit 7 arranged in the output stage by the keyed pulse. A constant output amplitude can always be obtained by eliminating the change in the baseband output due to the state (modulation degree).

Next, another embodiment of the present invention will be described with reference to FIG. FIG. 3 is a block diagram showing an embodiment of a receiver using the present invention. Reference numeral 8 is a bandpass filter unit having a plurality of different bandwidths. The operation of the receiver of FIG. 3 will be described. The high frequency signal input from the input terminal 1 is converted into an intermediate frequency signal by the tuner unit 4, band-limited by the filter unit 5, and then input to the demodulation unit 6. The input signal is converted into a baseband signal (for example, FM demodulation), then amplified by the gain control amplifier 7 and output from the baseband output terminal 2. Here, the gain control amount of the gain control amplification unit 7 arranged at the output and the bandwidth selection operation of the band pass filter unit 8 operate in conjunction with a control signal externally input to the control signal input terminal 3. That is,
Similar to the embodiment of FIG. 1, with respect to an input signal having a different degree of modulation, the same effect as that of the embodiment of FIG. Since the bandwidth of the band pass filter unit 8 can be set to a value suitable for the modulation factor of the input signal, interference due to unnecessary signals due to improper filter band, output S / N (signal to noise ratio), etc. It is possible to prevent the deterioration of the characteristics. For example, by using a keyed pulse for the external control signal of this embodiment, even if a signal with a high degree of modulation such as a MUSE signal is input, demodulation can be performed without degrading the signal component or the suppression characteristic of the unnecessary signal. Further, the output amplitude can be kept constant by controlling the fluctuation of the amplitude value of the detection output due to the difference in the modulation degree in association with the gain of the gain control amplification unit 7 arranged at the output. In the present embodiment, the bandwidth of the bandpass filter unit 8 and the gain control amount of the gain control amplification unit 7 are changed in association with each other by the control signal (for example, the keyed pulse). Even if only is changed, it is possible to prevent interference due to an unnecessary signal due to an inappropriate filter band and characteristic deterioration such as output S / N (signal-to-noise ratio).

[0009]

According to the present invention, a constant output signal can be obtained regardless of the signal state of the input signal, so that the degree of freedom in the circuit design in the subsequent stage is increased.

[Brief description of drawings]

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

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

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... High frequency input terminal, 2 ... Baseband output terminal, 3 ... Control signal input terminal, 4 ... Tuner part, 5 ... Band pass filter part, 6 ... Demodulation part, 7 ... Gain control amplification part, 8 ... Multiple bandwidths Band pass filter section having: 9 ... Keyed pulse input terminal.

Claims (6)

[Claims] 1. A means for selecting and amplifying only a desired signal from a plurality of input signals, converting it to an intermediate frequency signal, a band limiting means for band limiting the intermediate frequency signal, and a band limited signal. A demodulation means for demodulating
A receiver having a gain control means capable of changing an amplitude value of the baseband signal, wherein the gain control means performs gain control of output by a control signal from the outside. 2. A means for selecting and amplifying only a desired signal from a plurality of input signals and converting it to an intermediate frequency signal, and a band limiting means for band limiting the intermediate frequency signal to a plurality of different bandwidths. In a receiver having demodulation means for demodulating a band-limited signal into a baseband signal and gain control means capable of varying the amplitude value of the baseband signal, the bandwidth of the band limiting means and the gain control A receiver characterized in that the gain of the means is controlled simultaneously by an external control signal. 3. The receiver according to claim 1, wherein a keyed pulse is used as a control signal from the outside. 4. The receiver according to claim 2, wherein a keyed pulse is used as a control signal from the outside. 5. Means for selecting and amplifying only a desired signal from a plurality of input signals and converting it to an intermediate frequency signal, and band limiting means for band limiting the intermediate frequency signal to a plurality of different bandwidths. A receiver having demodulating means for demodulating a band-limited signal into a baseband signal, wherein the bandwidth of the band-limiting means is selected by a keyed pulse signal. 6. The receiver according to claim 1, 2, 3, 4, or 5, in which all circuits are integrated.