US2273640A - Superheterodyne receiver - Google Patents

Description

Feb. 17,'1942. J. HAANTJEs ErAL SUPERHETERODYNE RECEIVER Filed June 1-4, 1940 NETWORK To 1. F.

LOCAL osc/LLATOR INVENTRS JOHA HAANTJES Alva mssfs ENT/RE rum/v6 A/vo gERN RD?? DJ'LTELLEGEN ATTORNEY.

UNTTED STATE Patented Feb. 17, 1.942

. SUPERHETERODYNE RECEIVER t Johan Haantjes and Bernardus D. H. Tellegen,`

Eindhoven, Netherlands, yassignors to Radio Corporation of America, a corporation of Delaware Application June 14, 1940, Serial No. 340,500 In the Netherlands September 8, 1939 (Cl. 250m-20) 7 Claims.

,This invention relates to-superheterodyne receivers, particularly to those in which at any one time the entire band of the oscillations tombe ,received is admitted to the mixing Valve, as is the case for example with so-called infradyne sets. Thus, with these sets it is possible to use only a single tuning "circuit for the oscillator by making the intermediate frequency sufficiently high that is to say, beyond .the highest; incoming frequency.

The present invention consists in that with such a receiver adiode is used as a mixing valve, and is based on `recognition of the fact that the use `of a diodek circuit for this purpose involves the use ofY automatic preliminary selectivity with the result that the signals which are instantaneously undesired yield a comparatively small voltage on'the dio'de so that cross modulation and howling noises are not troublesome.

In order that the invention may bey clearly lunderstood and readily carried into effect it will now be described more fully with reference to the accompanying drawing whereinlig. 1 shows a schematic of the invention, Fig.,2 shows the frequency scale ofthe system, Fig. 3 illustrates a -l receiver embodying the circuit of Fig. 1.

Fig. 1 is a well known mixing circuit in which lation's, an intermediate frequency (I. F.) circuit If wi is` and a source of incoming oscillations. the frequency of the instantaneously desired station and wm the frequency to which the intermediate frequency ,circuit is tuned, the frequency wp of the oscillator must be chosen so that Now, the impedance of such a circuit for frequencies adjacent wi is equal to that of the parallel combination of a resistance R and a circuit tuned to wi whose `impedance and absolute width are equal to those of the intermediate frequency circuit. If the resistance R of Fig. 1 is shunted by the condenser C only in part, this substitution circuit is slightly altered but the tuned circuit remains.

If, therefore, in tuning the oscillator to wp a wide band of frequencies on either side of w1 is impressed on the circuit, the l-atter will have a much greater impedance for the desired frequency wr than for the higher or lower frequencies so that automatic preliminary selection results.-

This latter fact is of considerable importance with the infradyne circuit.

t Fig. 2 shows a frequency dial scale of such an infradyne set. .The frequency range I comprised between wo and wg is that of the incoming oscillations. wm is the intermediate frequency. The range O comprised between wm-i-wo and em-l-wg is that of the oscillator. The range S comprised between Zwmi-wu-and 2wm+wg is that of the mirror frequencies which have to be suppressed. With the infradyne this suppression is generally effected by a low-pass lter. y

Fig. 3 shows` oneform of construction 'of an infradyne circuit according to the invention. The signal 4oscillations in an antenna A are supplied to the input terminals of a low pass filter F. Between the output terminals of 'this filter are connected in series the primary of an intermediate frequency transformer M, a diode D, a resistance R shunted by a smoothing condenser C and an oscillator O. The lter F suppresses the mirror frequencies, and the automatic preliminary selective nature of the remaining part of the circuit insures that cross modulation and howling noises due to the stations undesired at that instant do not become troublesome. This latter effect may be assisted by selection of a higher oscillator Voltage, and also by an improve- .oscillator provided with means for tuning the `oscillator over a range of frequencies differing from said carrier frequencies by an intermediate frequency, said intermediate frequency exceeding the highest carrier frequency of said range, and an intermediate frequency circuit, said filter, os-

` cillator and intermediate circuit being connected in a closed series circuit with the electrodes of said mixer tube.

2. In combination with a diode mixer, a low pass wave input circuit constructed to pass without selection all modulated carrier waves comprised in a wide range, means impressing the waves passed by said input circuit upon said mixer, a local oscillator including means for tuning it to different desired frequencies comprised in a frequency range different from the carrier frequencies by a predetermined intermediate frequency, said intermediate frequency being chosen substantially higher than the highest carrier frequency of said input range, means comprising a resistor shunted by a condenser applying the oscillator output upon said mixer device, and an output circuit connected to said mixer device tuned to said intermediate frequency.

3. In combination with a mixer device .of the electron discharge type, a Wave input circuit con,- structed toy pass withoutV selection all modulated carrier waves comprised in a wide range, means impressing the Waves passed by said input circuit upon said mixer, a local oscillator including means for tuning it to diierent desired frequencies comprised in a frequency range differing from the carrier frequencies byV a predetermined intermediate frequency, said intermediate fre-- quency being chosen substantially higher than the highest carrier frequency of said input range, means applying the oscillator output upon said mixer device, and an output circuit connected to said mixer device tuned to said intermediate frequency, said mixer' device being a diode, and said input circuit being a low pass l-ter adapted to attenuate all frequencies in excess ef said .highest carrier frequency. v

4. In combination with a mixer device of the electron discharge type, a wave input circuit constructed to pass without selection all modulated carrier waves comprised in a wide range, means impressingv the waves passed by said input circuit upon saidmixer, a local oscillator including means for tuning it to different desired frequencies comprised in a frequency range differing from. the carrier frequencies by a predetermined intermediate frequency, said intermediate frequency being chosen substantially higher than the-highestcarrier frequency of said input range, means applying the oscillator output. upon said mixer dev-ice,l and an output circuit connected to saidmixer device. tuned to said intermedia-te fre- 5. In a superheterodyne receiver, an aperiodic signal input network adapted to transmit solely the signal energy comprised in a wide band of signal carrier frequencies, a diode mixer tube, means applying signal energy passed by said net- Work to said diode, a local oscillator connected to said diode, means for tuning the oscillator over a range of frequencies substantially higher than the highest carrier of said band, and an output circuit connected to said diode which is tuned to a. frequency equal to the difference between the highest carrier of said band and the frequency of said oscillator range.

6. In a superheterodyne receiver, an aperiodic signal input network adapted to transmit solely the signal energy comprised in a wide band of signal carrier frequencies, a diode mixer tube, meansy applying signal energy passed by said net- Work to said diode, a local oscillator connected to said diode, means for tuning the oscillator over arrange of frequencies substantially higher than the highest carrier of saidv band, a resistor in series With the space current path of the diode, a condenser in shunt with the resistor, and an output circuit connected to said diode which is tuned to a frequency equal to the diierence between the highest carrier of said band and the frequency of said oscillator range.

7. Ina superheterodyne receiver, an aperiodic signal input network adapted to transmit solely the signal energy comprised in a wide band of signal carrier frequencies, a diode mixer tube, means applying signal energy passed by said net- Work to said diode, a local oscillator connected to-said diode, means for tuning the oscillator over a range. of frequencies substantially higher than the highest carrier of said band, and an output circuit connected to said diode which is tuned to a frequency equal to the difference betweenv the highest carrier of said band and the frequency of said oscillator range, said aperiodic network, output circuit and oscillator. all being in series relation with said diode.

JOHAN HAANTJES. BERNARDUS D. H. TELLEGEN.

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