Telecommunications – Receiver or analog modulated signal frequency converter – Local control of receiver operation
Patent
1987-10-23
1989-12-05
Griffin, Robert L.
Telecommunications
Receiver or analog modulated signal frequency converter
Local control of receiver operation
455258, 455307, H04B 110
Patent
active
048858013
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method and to a circuit arrangement for converting frequency modulated signals through at least one intermediate frequency into low frequency signals.
2. Description of the Prior Art
West German DE-OS No. 30 48 263 describes a radio receiver provided with a filter arrangement. The received signal is converted via one or more mixer stages into intermediate frequency signals, which are fed via intermediate frequency filters to a demodulator, in which they are converted into low frequency signals. In order to keep interference at a minimum level, the filters are constructed in a narrow-band manner. A control voltage, derived from the output voltage of the demodulator displaces the resonance frequency of the narrow-band intermediate frequency filter connected upstream of the demodulator in such a way that the particular instantaneous value of the intermediate frequency is always within the band pass range of the filter.
As the control voltage is generated after mixing and selection as a result of the reverse control, control delays occur which are essentially given by the envelope delays of the filter. This means that the control voltage for the filter and the intermediate frequency voltage are time-shifted and there is a relative movement between the filter frequency and the intermediate frequency. In the case of high frequencies, this delay leads to difficulties in the follow-up of the filter so that interference can occur.
The intent of this invention is to provide a method and a circuit arrangement for converting frequency modulated signals through at least one intermediate frequency into low frequency signals, while improving the follow-up characteristics of the filter.
SUMMARY OF THE INVENTION
According to this invention this problem is solved by driving the oscillator is such a way that in the high range of low frequencies a deflection reduction is brought about, such that the resonance frequency of the filters is only moved backwards and forwards to a limited extent in the high frequencies to improve the follow-up characteristics of the filters. The deflection reduction preferably takes place through a phase rotation of the low frequency signals used for driving the oscillator, said phase rotation being performed in simple manner by an inverter connected in the feedback path.
BRIEF DESCRIPTION OF THE DRAWING
An embodiment of the invention is shown in the drawing and is described in greater detail hereinafter. The single drawing shows the circuitry according to the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The drawing reference numeral 1 is the input terminal of the circuit arrangement, to which are applied the frequency modulated reception signals or the intermediate frequency output signals of an intermediate frequency stage. Reference numeral 2 designates a mixer stage connected to a voltage-controlled oscillator 3 and connected to a filter arrangement 4 comprising several filters 5. Filter arrangement 4 is connected to the input of a demodulator 6 at whose output appear the low frequency signals. A first feedback circuit is provided across a matching circuit 7 between the output of demodulator 6 and filter arrangement 4 and a second feedback circuit is provided between the output of the demodulator 6 and the oscillator 3. An inverter 8 and a low-pass filter 9 are connected in the second return or feedback circuit.
The modulated, high frequency reception signals or the intermediate frequency signals pass to the mixer stage 2, where they are mixed with the output signal of the oscillator 3 to generate intermediate frequency signals at the output of the mixer stage. In accordance with its pass band, the filter arrangement 4 filters out the intermediate frequency signals, which are demodulated to low frequency signals in the demodulator 6. The low frequency output voltage of the demodulator 6 is supplied to the filter arrangement 4 across matching circuit 7 in such a way that the center frequency of each
REFERENCES:
patent: 3150323 (1964-09-01), Stavis et al.
patent: 3626301 (1971-12-01), Develet, Jr.
patent: 3922609 (1975-11-01), Grohmann
patent: 3936753 (1976-02-01), Clark
patent: 4263675 (1981-04-01), Hongu et al.
patent: 4293818 (1981-10-01), Jarger
patent: 4569085 (1986-02-01), Nolde et al.
patent: 4653117 (1987-03-01), Heck
patent: 4658438 (1987-04-01), Kamata et al.
Griffin Robert L.
H.U.C. Elektronik Hansen & Co.
Kuntz Curtis
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