DE3023773A1 - DEMODULATOR - Google Patents

Description

- 3 patent attorneys

Dlpl.-ing. Dipl.-Chem. Dipl.-Ing.

E. Prince - Dr. G. Hauser - G. Leiser 3 023773

Ernsbergerstrasse 19

8 Munich 60

June 24, 1980

PLESSEY HANDEL UND INVESTMENTS AG
Gartenstrasse 2
6300 Zug / Switzerland

Our reference: P 2430

Demodulator

The invention relates to demodulators and, more particularly, to those which receive two signals which are 90 ° out of phase and which in combination carry data to be demodulated.

The invention is particularly, although not exclusively, applicable to an FM co-channel duplex receiver such as it is described in DE-OS 27 11 476, or on one AM co-channel duplex receiver according to the British patent application 79 22701 of June 29, 1979.

According to the invention, a demodulator which receives two signals phase-shifted by 90 ° (phase quadrature-related) is which in combination carry data to be demodulated, characterized by two multiplicative mixers, each with one the 90 ° phase-shifted signals are fed, a 90 "phase shifter, a local oscillator, which over

^{Ka / Ma} 030063/0854

the 90 ° phase shifter the mixers superposition oscillator signals supplies, such that the local oscillator signals received from the respective mixers are out of phase, by a combining device to which the output signals from the mixers are fed, and by a detector device fed by the combining device and an output signal accordingly the modulation carried by the signals out of phase by 90 °.

The type of detector device to be used is selected according to the type of modulation, which of the 90 ° out of phase signals is carried.

According to an embodiment of the invention for the demodulation an amplitude-modulated signal, which is carried by the signals phase-shifted by 90 ° the detector device consists of an envelope detector or rectifier, which in the simplest case is a diode rectifier can be.

According to another embodiment of the invention for the demodulation of frequency modulation, which of the is carried signals phase-shifted by 90 °, the detector device consists of an FM discriminator or ratio detector, which is suitable for demodulating frequency modulation which is around one of the frequency of said oscillator corresponding center frequency fluctuates.

According to said one embodiment of the invention the demodulator can be part of a co-channel duplex receiver suitable for AM reception, as it is in the above British Patent Application No. 79 22701 filed June 29, 1979.

030Q63 / G854

According to the other embodiment of the invention can

the demodulator part of a suitable for FM reception

Be co-channel duplex receiver, as it is in the DE-OS 27 11 476 is described.

Some embodiments of the invention will now be described with reference to the drawing, which is a schematic Represents a block diagram of a co-channel duplex receiver which contains a demodulator.

According to the drawing, the receiver has a receiving antenna 1, from which signals via a duplexer 2 to two multiplicative mixers 3 and 4 are directed. The mixers receive a local oscillator signal from a Oscillator 5 is supplied, the mixer 3 receiving signals from the local oscillator via a 90 "phase shifter 6 is fed so that the local oscillator signals fed to the mixers 3 and 4 are phase-shifted by 90 °. Output signals for transmission are fed from the oscillator to a modulator 7, the modulation signals Line 8 receives and output signals for transmission an antenna 9 emits. Output signals from the mixer 3 are passed through a low-pass filter 10 and an amplifier 11 a terminal 12 of a demodulator shown within the dashed lines. Output signals from the Mixers 4 run through a low-pass filter 14 and an amplifier 15 to the other terminal 16 of the demodulator shown within the dashed line 13. The demodulator consists of two multiplicative mixers 17 and 18, which send signals out of phase by 90 ° from the input terminals or 16 received and those local oscillator signals phase-shifted by 90 ° from a local oscillator 19 and a phase shifter 20 are supplied. Output signals of the mixers 17 and 18 are an additive

030063 / 085A

Combining stage 21 supplied, the output signals of which are applied to a detector 22, which is on an output line 23 emits a signal corresponding to the modulation / which is carried by the signals received at the antenna 1 will.

The type of detector 22 is selected depending on the type of modulation received at the antenna 1. So can for FM reception a discriminator, such as a Foster-Seeley discriminator, or alternatively a ratio detector can be used. To receive amplitude modulation, the Detector 22 can take the form of any envelope detector, such as a simple diode detector. Such AM and FM detectors are known and will not be further described here.

It should be noted that the present invention is particularly concerned with providing a demodulator is so that the operation of the main part of the co-channel duplex receiver is not shown in detail nor is it described. However, this is based on the DE-OS 27 11 476 referenced / in the AM and FM co-channel duplex receivers are explained in detail. A demodulator according to the object of the present invention is used to to form a carrier frequency for the signals which are phase-shifted by 90 ° / are applied to the input terminals 12 and 16, or to synthesize, which is an image of the antenna 1 received signal in all respects, but which for FM signals around the frequency of the local oscillator 19 fluctuates (or deviates by this) .. In one embodiment, the frequency of the oscillator 5 can be 100 MHz, while the frequency of the local oscillator can be 0/5 MHz. When receiving frequency modulated Signals move at 12 when the input frequency changes

030063/0854

and 16 the sidebands present in the combining stage 21 with respect to a center frequency corresponding to the frequency of the local oscillator 19. In contrast, if the frequency of the local oscillator 19 changes, the sidebands can be shown to vary with respect to one of the frequency of the local oscillator 19 move corresponding center frequency to each other.

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Claims (5)

Patent attorneys Dipl.-Ing. ser3 0237 Dipl -Ing. Dipl.-Chem. G. Lei E. Prince Dr. G. Hauser Ernsbergerstrasse 19 June 1980 8 Munich 60 24. PLESSEY HANDEL UND INVESTMENTS AG Gartenstrasse 2 300 Zug / Switzerland Our reference: P 2430 Claims (j y Demodulator that receives two signals shifted by 90 °, which in combination carry data to be demodulated, characterized by two multiplicative mixers, each of which is fed one of the signals shifted by 90 °, a 90 ° phase shifter, a local oscillator, the feeds superposition oscillator signals to the mixers via the 90 "phase shifter, in such a way that the local oscillator signals received from the respective mixers are phase-shifted by 90 °, by a combining device to which the output signals from the mixers are fed, and by a detector device which is fed by the combining device and emits an output signal corresponding to the modulation carried by the signals shifted by 90 °. 2. Demodulator according to claim 1, characterized in that the detector device is an envelope detector for demodulation of amplitude modulated signals carried by the 90 ° phase shifted signals. 030063/0854 3. Demodulator according to claim 1, characterized in that the detector device consists of an FM discriminator or ratio detector which demodulates frequency modulation, which fluctuates around a center frequency corresponding to the frequency of said oscillator. 4. Demodulator according to one of the preceding claims, characterized by its use in a co-channel duplex receiver for the reception of amplitude-modulated Signals. 5. Demodulator according to one of claims 1 to 4, characterized through its use in a co-channel duplex receiver for the reception of frequency-modulated Signals. 030063/085 *