JPS6235742A - Pulse counter type fm demodulator of tdma system receiver - Google Patents

Abstract

PURPOSE:To prevent at DC drift generated by the demodulator of a TDMA receiver from being amplified by a base band amplifier as it is by generating the reference voltage of the base band amplifier by utilizing the output of a monostable multivibrator on the same chip. CONSTITUTION:A modulated IF signal is amplified by an IF amplifier 1 and inputted to the monostable multivibrator 2. The monostable multivibrator 2 generates pulses whose number corresponds to the input frequency and the signal is passed through a low-pass filter 4, amplified by the base band amplifier 5, and inputted to a comparator 6. At this time, the DC drift generated by the monostable multivibrator 3 owing to temperature variation is canceled by the base band amplifier 5 with a DC drift generated by the monostable multivibrator 3 of a reference voltage circuit 3' similarly, so its influence never appears at the output of the base band amplifier 5.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a pulse counter type FM demodulator in a TDMA (time division multiple access) communication system receiver, and more specifically, to improving the temperature characteristics of DC drift. This invention relates to a pulse counter type FM retrieval device that takes into consideration the following.

(Prior Art) FIG. 2 shows the configuration of a pulse counter type FM repeater in a conventional TDMA communication system receiver.

In the figure, IFIN is a modulated IF multiplied signal input terminal. The conventional circuit has an IF amplifier that amplifies the IF signal from this input terminal, and a mono multivibrator 1 that functions as a demodulator and generates a number of pulses corresponding to the frequency.
2, a low-pass filter 4 that removes high-frequency components from its output, a reference voltage generation circuit 13, a baseband amplifier 5 that amplifies the differential between the low-pass filter 4 and the reference voltage generation circuit 13, and a baseband amplifier 5. A comparator 6 that converts the output of @1# and @0'', a flip-flop 7 for outputting the output data of the comparator 6, a doubling circuit 8 for reading out the flip-flop 7, and a bandpass filter. 9 and a clock generation circuit consisting of a comparator IO.

(Problems to be Solved by the Invention) In the above pulse counter type FM demodulator, the baseband amplifier 5 is used to amplify the DC voltage difference between the DC component generated from the mono multivibrator 12 and the reference voltage generation circuit 13. Due to variations in the 10Vcc (power supply voltage) in Figure 2 or variations in the temperature characteristics of the mono-multivibrator, the DC voltage of the baseband amplifier output fluctuates along with ambient temperature fluctuations, and the data error rate deteriorates. There was a drawback.

SUMMARY OF THE INVENTION An object of the present invention is to provide a pulse counter type FM demodulator which can overcome the above-mentioned drawbacks.

(Means for Solving the Problems) In order to achieve the above object, a pulse counter type FM demodulator of a TDMA receiver according to the present invention includes an IF amplifier that amplifies a modulated IF flaw signal, and a frequency of the output of the IF amplifier. a mono-multivibrator that generates a number of pulses according to the number of pulses; a low-pass filter that receives the mono-multivibrator output as input; a reference voltage generation circuit; In a pulse counter type FM demodulator for a TDMA receiver, the pulse counter type FM demodulator of a TDMA system receiver comprises a baseband amplifier inputted to each terminal, and a comparator that converts the output of the baseband amplifier into @1" and "O# data. One mono multivibrator in the same chip is used as the mono multivibrator, and a reference voltage circuit created from the Q and Q outputs of the other mono multivibrator in the same chip is used as the reference voltage generation circuit, The demodulator is configured to reduce temperature characteristics of DC drift.

According to the above configuration, a DC drift of the same level as that generated in a mono-multivibrator functioning as a demodulator occurs in the reference voltage generation circuit, so it is not amplified by the baseband amplifier, and the DC voltage is not amplified due to temperature fluctuation. Drift is improved and deterioration of data error rate can be prevented.

(Example) Hereinafter, the present invention will be explained in more detail with reference to the drawings.

FIG. 1 is a circuit block diagram showing an embodiment of a TDMADMA type 46 counter type F'M demodulator according to the present invention.

In the figure, circuit sections with the same reference numerals as in FIG. 2 are circuit sections that perform the same functions. The difference from the conventional example is that a multivibrator in the same chip is used for the monomultivibrator 2 and the reference voltage circuit 3'.

The reference voltage circuit 3' connects the Q output of the multivibrator 3 and the Q
A variable resistor is connected between the output and the output, and the reference voltage is obtained from the tap terminal of the variable resistor.

The modulated IF flaw signal is amplified by an IF amplifier 1 and input to a mono multivibrator 2 .

The monomultivibrator 2 generates a number of pulses depending on the input frequency, and the signal is amplified by a baseband amplifier 5 through a low-pass filter 4 and input to a comparator 6.

At this time, the DC drift that occurs in the mono multivibrator 2 due to temperature fluctuations is removed by the space band amplifier 5 due to the DC drift of the multivibrator 3 of the reference voltage circuit 3' that also occurs. This effect does not appear on the output of the baseband amplifier 5.

In this way, a demodulated output of the baseband amplifier that does not include DC drift is obtained, which is converted by the comparator 6 into @12 and @0# data, and outputted from the flip-flop 7 as received data.

(Effects of the Invention) As described in detail above, according to the present invention, the reference voltage of the baseband amplifier of the TDMA pulse counter type FM demodulator is created by using the mono-multivibrator output in the same chip. Furthermore, the DC drift generated in the demodulator is prevented from being amplified by the baseband amplifier.

Therefore, it is possible to improve the deterioration of data error rate due to DC voltage drift due to ambient temperature fluctuations.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a pulse counter type FM demodulator according to the present invention, and FIG. 2 is a circuit diagram showing a conventional pulse counter type FM demodulator.
FIG. 3 is a circuit diagram of an M demodulator. 1... IF amplifier 2... Mono multivibrator 3... Reference voltage generation circuit using mono multivibrator chip 4... Low pass filter 5... Baseband amplifier 6... Comparator 7...
・Flip-flop 8...2 multiplier circuit 9...Band pass filter 1o...Comparator 12...Mono multivibrator 13...Reference voltage generation circuit

Claims (1)

[Claims] an IF amplifier that amplifies the modulated IF signal;
a mono-multivibrator that generates a number of pulses according to the frequency of the amplifier output; a low-pass filter that receives the output of the mono-multivibrator; a reference voltage generation circuit; and a reference voltage between the output of the low-pass filter and the reference voltage generation circuit. A baseband amplifier having positive and inverting input terminals as inputs, and a comparator that converts the output of the baseband amplifier into data of "1" and "0".
In a pulse counter type FM demodulator of a DMA receiver, one mono multivibrator in the same chip is used as the mono multivibrator, and the Q of the other mono multivibrator in the same chip is used as the reference voltage generating circuit. A pulse counter type FM demodulator for a TDMA receiver, characterized in that it uses a reference voltage circuit created from @Q@ outputs and is configured to reduce the temperature characteristics of DC drift of the demodulator.