DE3836143C2 - Mixer for high frequency transmit and receive arrangements - Google Patents

Description

The invention relates to a mixer for high-frequency Transmitting and receiving arrangements according to the preamble of Claim 1.

Such mixers go from DE 32 16 776 A1 and US 4 112 373.

Such mixers are used, for example, in the case of antennas Mixing up the frequencies of received or to be transmitted Signals used. They are also called mixer stages Tuners used for television systems. The mixer can Frequencies of two supplied signals in any one Wise by adding, subtracting, or multiplying into one Output signal can be implemented with an intermediate frequency. The mixers are used in a known technique next to one High frequency (RF) signal (input signal) as a second signal an oscillator signal coming from an external oscillator given up. As a result, they are controlled externally.

Externally controlled mixers are both passive and as active mixers known. A passive mixer is for example a diode mixer, which because of the as Resistor elements acting diodes significant losses can generate. Active mixers are for example Tube mixers and transistor mixers. With these mixers RF signal and oscillator signal are fed together. she are not decoupled at the inlet of the mixer and influence therefore also upstream parts and circuits, so that a Part of the oscillator power can be lost.  

From DE 32 16 776 A1 and US 4 112 373 externally controlled, active mixers with special transistors become known that have two inputs through which the RF signal and the oscillator signal are supplied separately can. The transistors used are Field effect transistors (FET) with two control electrodes, so-called dual gate FETs (DGF). Such a mixer has one good noise behavior and the oscillator performance can small compared to the mixers described above being held. Especially for applications in microwave technology is such a DGF but only a complex one producible and therefore expensive component.

Mixers have also been built for price reasons instead of an expensive DGF, two cheaper FETs in a row are switched. This also allows a mixer with two Establish decoupled inputs. Opposite a mixer with a DGF will have a higher performance than that Oscillator signal supplying oscillator needed. Such a Mixer also has a lower profit and one worse noise behavior. In addition, the corresponding tends Circuit for self-excitation rather than a mixer with one DGF. For these reasons, it is rarely used in practice.

The invention has for its object the to further develop the mixer described so that it is inexpensive, has a good noise behavior and a stable output signal delivers.

This task is carried out according to the characteristic features of the Claim 1 solved.

With this mixer, the "simple" Mixers disruptive tendency to self-excitation advantageous exploited by the internal resonator in the mixer Oscillator is created that becomes a self-oscillating Mixer leads. The mixer is made up of two inexpensive FETs  Cascade circuit built. He has a good one Noise behavior. An external oscillator is no longer needed. This results in another one for the mixer Discount.

As a result, the output signal of the mixer can continue be stabilized that the first FET 'that also Input signal is supplied, in addition the signal of a quartz-stable mother oscillator is given to the to achieve the well-known "injection locking" effect. These Possibility, for example, with an antenna array at least two emitters can be used. All spotlights Such an array can be equipped with a mixer be as described above. Because all mixers are independent swing from each other, they can have different phases to have. If all mixers on the same quartz stable Mother oscillator are connected, the signal of each is given to the same entrance, then all swing Mixer or their internal oscillators are phase locked. Your Output signals have the same stable phase position, so that they can be added vectorially. The signal of the  The mother oscillator can be used in both the fundamental frequency and can also be supplied as a subharmonic.

The level of the signal of the mother oscillator can much lower than that described above External control of mixers, since the first FET, to which the signal is fed, as an amplifier works. The level required by the mother oscillator can be up to decrease to 1/100 of the level required for external control depending on the stability requirements of the self-oscillating Mixer. This is also noticeable when the radiators of an antenna array with a phase shifter are equipped. A phase shifter does not produce insignificant losses. But there at the entrance to the mixer only a low level is required, the Phase shifters are particularly favorable between each Mother oscillator and mixer are switched on.

The phase-locked coupling of the mixer to one quartz-stable mother oscillator is also advantageous applicable when the signals of two or more Parabolic antennas fed to a common receiver should be. Here are the signals to be added also phase stable from the same phase each mixer passed on as an output signal, see above that also here vectorial addition of the output signals is possible.

Embodiments of the subject matter of the invention are in shown the drawings.

Show it:

Fig. 1 shows a mixer in a schematic representation.

Fig. 2 shows the use of a mixer in an antenna array.

Fig. 3 a section of a modification of the arrangement of FIG. 2.

Fig. 4 shows the use of the mixer in parabolic antennas.

The mixer M shown in Fig. 1 is surrounded by a dash-dotted line. It consists of two field effect transistors 1 and 2 - hereinafter referred to as "FET" for short - each having three electrodes. These are the gate electrode (gate), the source electrode (source) and the drain electrode (drain). The respective electrodes are indicated for the FET 1 with G1, S1 and D1 as well as for the FET 2 with G2, S2, and D2. The two FETs 1 and 2 are electrically connected in series and are connected to one another via their electrodes D1 and S2. A resonator R is connected between G2 and D2 of the FET 2 and, in cooperation with the FET 2, forms an internal oscillator of the mixer M. The natural frequency of the resonator R is chosen so that it corresponds to an oscillator frequency which is suitable for mixing an output signal Zf to be tapped at D2.

If, for example, a frequency band as the input signal fs of 11-12 GHz is fed to mixer M at G1 and an output signal Zf of 1-2 GHz is then desired the natural frequency of the resonator R is chosen so that if the input and output signals are the same Oscillator frequency of 10 GHz results. In reverse position the oscillator frequency 13 GHz. In this case Input signal fs supplied via G1 is therefore mixed.

The mixer M could also be used to mix up a via G1 supplied input signal with a frequency band of 1-2 GHz are used. To achieve an output signal from 11-12 GHz on D2 the same resonators could then be used R can be used as described above.  

In operation of the mixer M of FIG. 1 for mixing is supplied to the same fs, an input signal on G1. An intermediate frequency Zf can then be tapped at D2 as the output signal. The mixer M is formed by the resonator R as a self-oscillating mixer, which delivers a stable output signal Zf. To further stabilize the output signal Zf, it can additionally be connected to a quartz-stable mother oscillator, the signal IL of which is also fed via G1, as is the input signal fs. The level of the IL signal can be very low.

A mixer according to FIG. 1 can be used particularly advantageously in an antenna array A, which is shown in detail in FIG. 2. A large number of radiators 3 (at least two) are arranged in such an array A, all of which can be connected to a mixer M each. According to FIG. 2, however, several radiators 3 can also be combined to form a group, which are then connected together with a mixer M. All mixers M vibrate independently of one another as self-oscillating mixers, so that their output signals can have different phase positions. With the mixer M according to FIG. 1, this disadvantage can be avoided in a simple manner if all mixers M are connected to a common quartz-stable mother oscillator. All mixers M are supplied with the same signal IL from the mother oscillator and thus rigidly connected to the mother oscillator. The properties of the mother oscillator with regard to phase noise, phase position and frequency stability are impressed on the self-oscillating mixers M. As a result, your output signals have the same phase position. They can be added in phase without interference.

The advantage of connecting the mixer M to a quartz-stable mother oscillator is also noticeable when each radiator 3 is equipped with a phase shifter 4 for pivoting the radiation lobe of the array A. Since only a low level is required for the phase-locked coupling of the mixer M to the mother oscillator, the phase shifters 4 according to FIG. 3 can each be connected between the mother oscillator and the mixer M. Losses generated by the phase shifters 4 do not have a disturbing effect.

The mixer M according to FIG. 1 can also be used to advantage if the signals from at least two parabolic antennas 5 and 6 are to be fed together as an output signal Zf to a receiver. This is carried out, for example, if the gain of an individual antenna is too small, but the diameter of the reflector should not or cannot be increased. A corresponding arrangement is shown in FIG. 4. Here, too, the output signals of the mixer M are delivered as phase-locked signals by connection to a quartz-stable mother oscillator, which can be combined to form an improved output signal Zf without any problems. This circuitry measure increases the resulting antenna gain without increasing the reflector diameter of an individual antenna.

Claims (3)

1. Mixer for high-frequency transmission and reception arrangements, consisting of a field effect transistor circuit with two gate electrodes and an oscillator formed between one of the gate electrodes and a drain electrode, characterized in that

• - That the transistor circuit consists of two field effect transistors ( 1 , 2 ) connected in series,
• - That the drain electrode (D1) of the first with the source electrode (S2) of the second field effect transistor is connected,
• - That at the gate electrode (G1) of the first field effect transistor ( 1 ) an input signal (fs) can be applied and on the drain electrode (D2) of the second field effect transistor ( 2 ) an output signal (Zf) can be tapped and
• - That between the gate electrode (G2) and the drain electrode (D2) of the second field effect transistor ( 2 ), a resonator (R) is connected, which forms the oscillator with the second field effect transistor ( 2 ) and whose natural frequency is chosen so that the thereby determined Frequency of the oscillator leads to the predetermined mixing or mixing of the input signal (fs).

2. Use of a mixer according to claim 1 for operating an antenna array with at least two radiators, characterized in that

• - That a mixer (M) is connected to each radiator ( 3 ) or to a group of radiators ( 3 ),
• - That all mixers (M) the same signal (IL) of a quartz-stable mother oscillator is supplied and
• - That the output signals of all mixers (M) are combined to form a resulting output signal (IF).

3. Use of a mixer according to claim 1 for operating an antenna unit consisting of at least two parabolic mirrors, characterized in that

• - that a mixer (M) is connected to each parabolic mirror ( 5, 6 ),
• - That all mixers (M) the same signal (IL) of a quartz-stable mother oscillator is supplied and
• - That the output signals of all mixers (M) are combined to form a resulting output signal (IF).