JPH03190306A - Local oscillator - Google Patents

Abstract

PURPOSE:To attain frequency changeover with simple constitution by applying switching control to a frequency at which a negative resistance of a negative resistive element is maximized so as to be made correspondent with each resonance frequency of 1st and 2nd dielectric resonators. CONSTITUTION:A prescribed DC bias voltage is applied to a gate G and a source S of a field effect transistor (TR) (FET) 30 via 1st and 2nd DC bias voltage terminals 40, 42. Then a control voltage is applied to a varactor diode 46 connecting to a source S of the FET 30 with a control voltage terminal 47. With the control voltage applied to the FET 30, frequencies causing a maximum negative resistance system return gain A correspond to resonance frequencies of 1st or 2nd dielectric resonator 34 or 35 when the negative resistance system is viewed from the gate G of the FET 30. For example, the frequency is subject to switching control to be 10GHz or 10.75GHz. Thus, the frequency is switched with simple constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to, for example, satellite broadcasting and satellite communication systems, and particularly relates to a local oscillator used in a frequency switching type low noise converter thereof.

(Prior Art) In recent years, in the field of broadcasting and communication technology, communication satellites and broadcasting and communication systems using broadcasting satellites have been established. For example, as shown in FIG. 4, a receiving system that receives the services of such a system includes an antenna 1 that receives a signal, a low-noise converter 2 that converts the frequency of the received signal, and
It is composed of a tuner 3 and a display 4. In this receiving system, the low-noise converter 2 is applied to multiple frequency bands so that the frequency bands differ depending on the broadcasting and communication system receiving the service, so that the services of multiple systems can be received. It is configured to be frequency switchable.

FIG. 5 shows such a conventional low-noise converter, in which the input waveguide 10 is connected to the input waveguide 10 via the antenna 1.
A radio frequency (RF) signal of 2.5 GHz) is input.

After this RF multiplied signal is guided to a wideband low noise amplifier (LNA) 11 and amplified, it is passed through a band pass filter (BPF) 1.
2a.

12b, each band is divided into each band, and each band is connected to a mixer (MIX
ER) 13a, 13b, local oscillators 14a, 1
Intermediate frequency (IF) according to the local oscillator (LO) frequency of 4b
The frequency is converted into a signal.

This IF multiplied signal intermediate frequency amplifier (IF AMP) 1
5, and its output signal is output from the output terminal 17 via the capacitor 16.

Further, a D/C voltage (for example, 14/18V) is superimposed on the output signal, separated by a coil 18, and then guided to a comparator 19, a power supply 20, and a level shift circuit 21. Of these, the comparator 19 generates a switching control signal according to the manually applied DC voltage, and outputs it to the control signal input terminal of the switch 22 to control the switching of the switch 22. At the same time, the level shift circuit 2] outputs a bias voltage to one of the selected local oscillators 14a and 14b via the switch 22.

Further, the power supply 20 outputs a bias voltage for operating the low noise amplifier 11 and the intermediate frequency amplifier 15.

However, in the above-mentioned low noise converter, local oscillators 14a, 14b are provided as local oscillator means, the number of which corresponds to the band of the signal to be received.
By configuring oscillator b to be controlled in a switching manner according to the frequency, a plurality of local oscillators 1 can be operated according to the frequency.
4a and 14b, the circuit configuration becomes large and expensive.

(Problems to be Solved by the Invention) As described above, the local oscillation means used in conventional frequency switching type low noise converters has the problem that the circuit configuration is large and expensive. Was.

This invention was made in view of the above circumstances, and an object of the present invention is to provide a local oscillation device that has a commercially available structure, is capable of frequency switching, is inexpensive, and can promote miniaturization. shall be.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides first and second dielectric resonators having different resonant frequencies coupled to a negative resistance element, and a negative resistance of the negative resistance element. negative resistance control means for obtaining first and second oscillation outputs by controlling switching of a frequency at which the resistance is maximum to correspond to each resonance frequency of the first and second dielectric resonators; This is a local oscillator.

(Function) According to the above configuration, the frequency at which the negative resistance of the negative resistance element is maximum is controlled to be switched to the frequency corresponding to the resonance frequency of the first and second dielectric resonators, respectively. It oscillates and outputs first and second oscillation outputs. Therefore, with only one local oscillator, the first and second oscillation outputs can be obtained in a switchable manner, simplifying the circuit configuration and promoting miniaturization as much as possible.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a local oscillation device according to an embodiment of the present invention, in which a field effect transistor (FET) 30, for example, is provided as a negative resistance element.

This FET 30 has its drain D grounded, and its gate G connected to one end of a coupled line 31. A capacitor 32 and a grounded resistor 33 are connected in this order to the other end of the coupled line 31. Further, first and second dielectric resonators 34 and 35 are respectively coupled to the coupled line 31,
These first and second dielectric resonators 34 and 35 have a first
and the second output terminals 36 and 37 are respectively output lines 38
It is connected via ゜39.

The FET 30 has a first DC bias voltage terminal 40 connected to its gate G via a coil 41, and a second DC bias voltage terminal 42 connected to its source S via a coil 43.
connected via. Further, the source S of the FET 30 is connected to one end of a varactor diode 46 via a stub 44 and a capacitor 45. varactor diode 46
is grounded at the other end, and the control voltage terminal 4 is connected to one end.
7 is connected via a coil 48.

In the above configuration, the FET 30 has first and second DC bias voltage terminals 40.4 at its gate G and source S.
A predetermined DC bias voltage is applied via 2. A control voltage is applied from a control voltage terminal 47 to a varactor diode 46 connected to the source S of the FET 30. This control voltage is applied to FET3 as shown in FIG.
The frequency at which the negative resistance system return gain A is maximum when looking at the negative resistance system from the gate G of 0 corresponds to the resonant frequency of the first or second dielectric resonator 34, 35, for example, 10 GHz or Switching control is performed so that the frequency becomes 10.75 GHz. At this time, the resonant system return loss when looking at the resonant system from the gate G of FET30 is 1 as shown by B in Figure 2.
It is minimum at 0 GHz and 10.75 GHz, and is smaller than the negative resistance return gain A. As a result, in conjunction with switching the control voltage, the first or second dielectric resonator 3
4.35 can be selectively excited to 10GHz or 10
．． The oscillation output of 75 GHz is transmitted to the first or second output terminal 36. through the output line 38.39. Output to 37.

Next, a low noise converter using the above local oscillation device as local oscillation means will be explained with reference to FIG. however,
In Figure 3, the same parts as in Figure 5 are indicated by 1.
, are given the same reference numerals and their explanations will be omitted.

That is, the local oscillator is 10GHz and 10.75G.
The control voltage terminal 47 is provided between the Hz mixers 13a and 13b, and the D/C voltage (for example, 14/18V) superimposed on the output signal amplified by the IF amplifier 15 is separated by a coil 16. , a predetermined control voltage is supplied via the comparator 19a. As mentioned above, this control voltage is determined when the negative resistance of the FET 30 is 10 GHz or 10.75 GHz.
By switching the control voltage to the maximum frequency of GHz,
The first or second dielectric resonator 3435 is selectively excited, and the oscillation output of 10 GHz or 10.75 GHz is sent to the mixer 13a from the first or second output terminal 36.37.
, 13b for operation. At this time, the power supply 2 is connected to the first and second DC bias voltage terminals 40 and 42.
A predetermined DC bias voltage is supplied from zero.

In this way, the local oscillator device includes first and second dielectric resonators 3 having different resonance frequencies coupled to the FET 30.
4.35, and by controlling the frequency at which the negative resistance of this FET 30 is maximum to correspond to each resonance frequency of the first and second dielectric resonators, different first dielectric resonators are provided.
and a second oscillation output. According to this, since different first and second oscillation outputs can be obtained with one local oscillator, the circuit configuration can be simplified, and therefore it is possible to promote miniaturization at low cost.

Note that this invention is not limited to the above embodiments, but also includes
It goes without saying that various modifications can be made without departing from the spirit of the invention.

[Effects of the Invention] As detailed above, according to the present invention, with a simple configuration,
It is possible to provide a local oscillation device that is capable of frequency switching, is inexpensive, and can be miniaturized.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram showing a local oscillation device according to an embodiment of the present invention, FIG. 2 is a diagram showing the frequency characteristics of FIG. 1, and FIG. FIG. 4 is a block diagram showing a satellite reception system, and FIG. 5 is a block diagram showing a conventional low-noise converter equipped with local oscillation means. 30...FET, 31...Coupled line, 32.45.
... Mindensor, 33... Resistor, 34.35... First and second dielectric resonator, 36.37... First and second output terminal, 38.39... Output line ,41,4
3゜48...Coil, 44...Stub, 46...
Varactor diode, 47...control voltage terminal.

Claims (1)

[Claims] First and second dielectric resonators having different resonance frequencies are coupled to a negative resistance element, and a frequency at which the negative resistance of the negative resistance element is maximum is set to the first and second dielectric resonators having different resonance frequencies. 1. A local oscillation device comprising: negative resistance control means for obtaining first and second oscillation outputs by performing switching control so as to correspond to each resonance frequency of two dielectric resonators.