DE1172324B - Transistor mixer circuit - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school Class: H03d

German class: 21 a4- 24/01

Number:
File number:
Registration date:
Display day:

N19368 IXd / 21 a4
December 27, 1960
June 18, 1964

The invention relates to a transistor mixer circuit for two relatively far apart frequency ranges, e.g. B. 41 to 68 MHz and 174 to 216 MHz, at which the intermediate frequency is only slightly lower than the lowest receiving frequency is, a high-frequency circuit is connected between two electrodes of the transistor and the high frequency signals and the oscillator vibrations of the same electrode (e.g. the base) of the transistor are supplied. Such conditions exist especially when receiving frequency ranges more than an octave apart in television receivers that use both for band I (41 to 68 MHz) as well as for band III (174 to 216 MHz).

In the case of mixer circuits, it is known to be parallel to the input circuit of the mixer transistor and thus in parallel to the circuit that is tuned to the high-frequency signals to be received and to which the local oscillator signals are supplied to switch a so-called suction circuit ■ which is dimensioned so that for the intermediate frequency signals result in series resonance. In the device according to the invention this has Suction circuit, a series connection of a coil and a capacitor, serve a dual purpose. First it is necessary to increase the mixing slope of the transistor. The coupling capacitor that into the input circuit between a parallel circuit made up of a coil and a capacitor and the mixer transistor is switched on, has tuned for the frequency to which the intermediate frequency circuit is a relatively large impedance. Without a suction circuit, the intermediate frequency component would of the current flowing through the input circuit, which is created by superimposing the local oscillator current and the high frequency signal current results in a relatively large resistance in this input circuit learn the intermediate frequency signal voltage between the input electrodes of the Mixing transistor and, as a result, the mixing steepness would be relatively small.

Second, the suction circuit is required to make the intermediate frequency transmission curve independent of the To make retroactive effect, because the signals in the intermediate frequency output circuit of the mixer transistor generate by reaction via a parasitic transistor capacitance in the absence of a suction circuit an intermediate frequency voltage between the input electrodes of the mixer transistor, which in turn generates an additional signal in the output circuit, which affects the shape of the intermediate frequency transmission curve.

Transistor mixer circuit

Applicant:

N.V. Philips' Gloeilampenfabrieken, Eindhoven

(Netherlands)

Representative:

Dipl.-Ing. E. E. Walther, patent attorney,

Hamburg 1, Mönckebergstr. 7th

Named as inventor:

Pieter Bikker,

Adalbertus Hermanus Jacobus

Nieveen van Dijkum, Nijmegen (Netherlands) - -

However, the attachment of a suction circuit is associated with some disadvantages. Has a suction circuit namely a narrow bandwidth, whereby the above-mentioned retroactive effect only in a proportionate way narrow frequency range does not affect the shape of the intermediate frequency transmission curve exercises. In addition, the suction circuit forms one together with the input capacitance of the mixer transistor Parallel circuit, the signals with frequencies that belong to the lowest channels in band I, nevertheless can give a significant boost, whereby the high frequency transmission curve changes undesirably.

In a transistor mixer circuit of the type mentioned at the outset, these disadvantages are avoided, if according to the invention a resistance of relatively low value of the coil one in on in a known manner to the electrode (z. B. the base) of the mixer transistor connected intermediate frequency suction circuit is connected in parallel.

These results are not achieved if the resistor is in parallel with the capacitor of the suction circuit is switched because the impedance of the damped suction circuit for the middle frequency, to which the intermediate frequency output circuit is tuned has the same value as when this one Resistor would be connected in parallel to the coil. However, this impedance increases significantly at higher frequencies to, so that the suction circuit for the lowest channels in band I means hardly any attenuation.

409 600/273

Claims (1)

3 4 In the frequency range of band III, the suction disadvantages are less disturbing, because not only the parking price due to the resistance parallel to the coil in the allele circuit 6, 7, 12 a negligible impedance Suction circuit is attenuated much less than in frequency, but also because the input impedance is now range of band I. The input impedance of the transistor 1 is much smaller than for frequencies Mixing transistor is in this area, however, so 5 in band I. Switching the oscillator frequency from low that the high-frequency transmission curve is still one band on top of the other and from one channel is not affected. the other is done by replacing the coil 17. The invention is described below with reference to the For the switching elements z. B. the following Basic circuit diagram according to FIG. 1 and the incoming values chosen: Executed embodiment according to Fig. 2 io capacitor 4 0.5 to 2pF explained in more detail. _v '"" In Fig. 1 are made up of a coil 3 and capacitor 5 4.7 pF a capacitor 4 built high frequency capacitor 7 47 pF parallel circuit 2, whose capacitor is not connected to earth 9 1 pF End via a coupling capacitor 5 to the base 15 capacitor 18 0.5 to 2 pF of the mixing transistor 1 is connected, high-frequency capacitor 21 18 pF signals from the source 13 supplied. Switchover _{c 1U} ..,, .., _n .. _TT from one channel to the other and from a self-induction 6 0.44 _μ Η Tape to the other is done by exchanging the self-adhesive 19 0.25 μΡ Coil 3. The result of a local oscillator 10 - 20 resistance 8 470 ohms The signals are connected to the input electrodes of the mixer via a very small capacitor 9. The transistors are of the type in which the transistor 1 is coupled. Between the emitter and the grounded emitter circuit, the input resistance at the base of the transistor 1 is a series circuit 60 MHz about 300 ohms and at 200 MHz about a coil 6 and a capacitor 7 is 25 30 ohms, while the input capacitance when standing Suction circuit attached. According to the invention, these frequencies are approximately 30 and approximately 10 pF, respectively.
tion is the coil 6 by a relatively _p ,
small resistor 8 bridged. The resistance claim:
attenuates the suction circuit 6, 7 to such an extent that transistor mixing circuit for two relatively B. 41 to 68 MHz and 174 to sistor 1 to the high frequency circuit 2 a negligible- 216 MHz, at which the intermediate frequency is only Bares intermediate frequency signal between the emitter and a little lower than the lowest frequency base of the transistor 1 in a relatively quenz, between two electrodes of the wide frequency range generated, whereby the transistor 35 sistor is turned on a high-frequency circuit laßkurve of the intermediate frequency circuit 11 of suction and the high-frequency signals and the oscillator circuit 6, 7 is not deformed. In addition, the vibrations of the same electrode (e.g. the resistor 8 ensure that the transistor from the suction circuit 6, 7 base) are fed, and the input stray capacitance 12 of the transistor 1 characterized in that a resisting parallel circuit, the In the frequency range of 40 there was a relatively low value of the coil band I (41 to 68 MHz) still a relatively one in a manner known per se to this electrode has an impedance and the transmission curve of the trode (base) of the mixer transistor switched high-frequency circuit 2, if this is on a Channel intermediate frequency suction circuit connected in parallel is coordinated in Volume I, adversely affected, is ered. is significantly attenuated, whereby the transmission curve 45 the desired form of the high-frequency circuit. retains. German Patent No. 712 805; For the channels in band III, this attenuation is USA patents No. 1703 079, 1724 915, much less, but here are the 2166274 mentioned. 1 sheet of drawings 409 600/273 6.64 © Bundesdruckerei Berlin