JPH033454A - Method for quick reception rise - Google Patents

Abstract

PURPOSE:To shorten the reception rise time by switching the time constant of AC coupling between a frequency discriminator and a base band part by an analog switch to faithfully discriminate continuous data of the same code. CONSTITUTION:At the time of reception rise, the time constant of AC coupling is determined by only a resistor 4 and a coupling capacitor 3 because an analog switch 6 is turned on, and the coupling capacitor 3 is quickly charged. When zerocrossing is detected in the output of a comparator 8 by a zero-crossing detector 10, the time constant of AC coupling is determined by the series value of resistors 4 and 5 and the coupling capacitor 3 because the analog switch 6 is turned off. Consequently, the cut-off frequency of a high-pass filter consisting of resistors 4 and 5 and the coupling capacitor 3 can be set to a sufficiently low value. Thus, the reception rise time is shortened because the time constant of AC coupling can be reduced at the time of rise, and even continuous data of the same code is satisfactorily discriminated because the low cut-off frequency is sufficiently reduced in the steady reception state.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a radio receiving device used in a digital radio system or the like.

(Prior art) Figure 2 shows the conventional FSK (Frequency S
FIG. 2 is a diagram showing the configuration of a baseband section of a wireless receiver (hiftKeying). In the figure, 21 is a frequency discriminator, which is connected to a low-pass filter 22.

23 is a coupling capacitor, 24 is an amplifier, and 25 is a comparator. A Qit pressure generator 26 is connected.

Next, the operation will be explained. In FIG. 2, when an FSX modulated signal is input, it is demodulated by a 1-frequency discriminator 21 and a low-pass filter 22, and is demodulated by a coupling capacitor 23.
It is AC-coupled with the amplifier 24, compared with the voltage of the reference voltage generator 26 by the comparator 25, and outputs the received data as a digital signal. In this way, even in the conventional FSX radio receiving device, if the coupling capacitor 23 is sufficiently charged, it is possible to output received data when an FSK modulated signal is input.

(Problems to be Solved by the Invention) In the conventional FSK radio receiving device described above, when the potential difference between the DC value of the frequency discriminator output and the reference voltage is large, faithful data judgment is performed until sufficient charge is stored in the coupling capacitor. Moreover, if the time constant of AC coupling is made small, the cutoff frequency of the bypass filter becomes high, and continuous data of the same sign cannot be determined faithfully.

SUMMARY OF THE INVENTION An object of the present invention is to provide an excellent FSX radio receiving device that eliminates the conventional drawbacks and has a faster reception rise time.

(Means for Solving the Problems) The reception fast rise method of the present invention detects a zero cross signal between the output voltage of a frequency discriminator and a reference voltage, and uses an analog switch to detect an alternating current between the frequency discriminator and the baseband section. The time constant of the coupling is changed.

(Function) According to the present invention, the DC potential of the FSX demodulated output can be quickly brought to the same potential as the reference voltage by reducing the time constant of AC coupling with the baseband section at the start of reception, and the zero-cross signal is detected, by switching the time constant to a sufficiently large value using an analog switch.

It is possible to perform comprehensive data judgment.

(Example) An embodiment of the present invention will be described based on FIG.

FIG. 1 is a schematic block diagram of an FSK radio receiving apparatus according to the present invention. In the figure, 1 is a frequency discriminator, 2 is a low-pass filter, 3 is a coupling capacitor, 4°5 is a resistor, and 6
is an analog switch, and 7 is an amplifier.

8 is a comparator, a reference voltage generator 9 and an amplifier 7
is connected. The output of the comparator 8 is output as received data and is connected to the zero cross detector IO,
The analog switch control circuit 11 is connected to the analog switch 6.

Next, the operation will be explained. When an FSX modulated signal is input, it is demodulated by a frequency discriminator 1 and a low-pass filter 2. AC-coupled with amplifier 7 by coupling capacitor 3,
After being amplified by an amplifier 7, it is compared with the output of a reference voltage generator 9 by a comparator 8. This output is a digital signal, which is output as received data and is also input to the zero cross detector 10, which detects both rising and falling etch and outputs a pulse to the analog switch control circuit 11. When the analog switch control circuit 11 counts this pulse a predetermined number of times within a certain period of time, the analog switch 6, which was initially in the ON state, is turned OFF. Resistors 4 and 5 together with coupling capacitor 3 determine the time constant of the AC coupling between low-pass filter 2 and amplifier 7 .

In this way, according to this embodiment, since the analog switch 6 is in the ON state at the time of reception rising, the time constant of AC coupling is determined only by the resistor 4 and the coupling capacitor 3.
The coupling capacitor 3 can be charged rapidly. Further, when a zero cross is detected by the zero cross detector 10 from the output of the comparator 8, the analog switch 6 is turned OFF.
Since it becomes an FF state, the time constant of AC coupling is set by resistors 4 and 5.
is determined by the series value of and the coupling capacitor 3. Therefore, resistors 4, 5. The cutoff frequency of the bypass filter constituted by the coupling capacitor 3 can be set to a sufficiently low value.

(Effects of the Invention) According to the present invention, since the time constant of AC coupling can be made small at the time of rise, the reception rise time can be sped up, and in the steady reception state, the low cutoff frequency can be made sufficiently low. Continuous data with the same code can also be determined efficiently, and its practical effects are great.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram of an FSK radio receiver according to an embodiment of the present invention, and FIG. 2 is a schematic block diagram of a conventional FSK radio receiver. 1...Frequency discriminator, 2...Low pass filter, 3...Coupling capacitor, 4゜5...Resistor, 6...Analog switch, 7...Amplifier,
8...Comparator, 9...Reference voltage generator, 1
0... Zero cross detector, 11... Analog switch control circuit.

Claims (1)

[Claims] A fast reception riser characterized in that a zero cross signal between the output voltage of a frequency discriminator and a reference voltage is detected, and a time constant of AC coupling between the frequency discriminator and a baseband section is switched by an analog switch. Method.