JPH0229008A - Voltage controlled oscillator - Google Patents

Abstract

PURPOSE:To stop the undersired oscillation of the oscillator by constituting the title oscillator that plural oscillation circuits are switching by a switching voltage and controlling the resonance frequency band of the resonator to the outside of a negative resistance by the switching voltage. CONSTITUTION:Since frequency bands a1, a2 are both in the negative resistance band, the oscillating condition is satisfied the switching voltage V1, V2 are zero and the oscillation circuits are oscillated in the respective resonance band. If a circuit voltage VC is changed, the plural oscillators are switched by not a power supply by a control voltage. Since the DC bias is always applied, no problem of a drift just after the switching is not caused alike a conventional oscillator. Thus, high speed switching is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Object of the Invention [Field of Industrial Application] The present invention relates to an improvement in the switching method of a plurality of voltage controlled oscillation circuits for generating high frequency signals.

[Conventional technology]

Conventionally, voltage controlled oscillators (Volt
age Controlled 0scillator
(hereinafter referred to as VCO), when a single VCO cannot sweep a required frequency band, a plurality of voltage controlled oscillation circuits with shifted bands are used to widen the overall bandwidth. FIG. 3 is a configuration block diagram showing a conventional vCO using a plurality of voltage controlled oscillation circuits.

A first oscillation circuit including a resonant circuit 12 and a negative resistance circuit 13 and a second oscillation circuit including a resonant circuit 22 and a negative resistance circuit 23 are switched by switches 14 and 24 connected to the power supply voltage VCC. This is how it was done. When the switch 14 is on and the switch 24 is off, the first oscillation circuit operates, and when the switch 24 is on and the switch 14 is off, the second oscillation circuit operates and its output is output from the terminal 2. The resonant circuit 12 is configured as a circuit consisting of a capacitor C12 and a diode I) connected in series, and an inductance L+2 connected in parallel. Control voltage Vc
is the capacitor Cot inductance. When added to the connection point between the resonant inductance C12 and the diode D1 through an AC insulation filter consisting of the diode I)
As the reverse bias voltage of 1 changes, its capacitance changes and the resonance band changes. When the switch 14 is on, oscillation occurs in this resonance band with the grounded base negative resistance circuit 13, and is output from the terminal 2 via the high frequency coupling capacitor C13.

When the switch 24 is on, the second voltage controlled oscillation circuit performs the same operation in a different oscillation band.

[Problem that the invention seeks to solve]

However, the above vCO is
Immediately after the switch 4 is turned on, when the DC bias changes from 0 to a predetermined value, an amplitude change occurs due to temperature drift, etc., so it is necessary to wait until the operation becomes stable. Therefore, there is a problem that the plurality of voltage controlled oscillation circuits cannot be switched at high speed.

The present invention was made to solve the above problems,
It is an object of the present invention to realize a VCO capable of high-speed switching of a plurality of voltage controlled oscillation circuits with a simple configuration.

``Structure of the Invention'' [Means for Solving the Problems] The present invention relates to a voltage controlled oscillator that outputs a signal with a frequency corresponding to a control voltage, and its characteristics are as follows.
The oscillation frequency band is different, and includes an adding means for adding the switching voltage to the control voltage, a resonant circuit whose resonant frequency band is controlled based on the output of the adding means, and a negative resistance circuit to which the output of the resonant circuit is connected. The present invention is configured to include a plurality of sets of oscillation circuits and an output terminal to which the outputs of the plurality of sets of oscillation circuits are connected, and to switch between the plurality of sets of oscillation circuits using a switching voltage.

[Effect]

By controlling the resonant frequency band of the resonator to be outside the negative resistance band of the negative resistance circuit using the switching voltage, unnecessary oscillation of the oscillator can be stopped.

〔Example〕

Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a block diagram showing an embodiment of a voltage controlled oscillator according to the present invention. The same parts as in FIG. 3 are given the same symbols. 1 is an input terminal to which the control voltage Vc is applied, and 11.12 is an adder that adds switching voltages V, V2 to the control voltage VC from the input terminal 1, respectively. Capacitance C++ and inductance I7,1 are added to adder 11
The first low-pass filter for AC isolation connected to the output of the adder 21, the capacitance C2, and the inductance l, 21 constitute a similar second low-pass filter connected to the output of the adder 21. 12.22 is the 1st. the first . This is a second resonant circuit. The first resonant circuit is connected to a capacitor C12 (usually of variable capacitance type).
An LC resonant circuit is constituted by a circuit consisting of a series connection of a diode D1 and a parallel connection of an inductance L12.

Similarly, the second resonant circuit constitutes an LC resonant circuit by connecting a capacitor C22 in parallel with an inductance 1722 and a circuit consisting of a series connection of a diode D2 similar to the above. The cathode side of the diodes D, D2 is connected to the capacitor C.
I 2 and C22 respectively, and the anode side is connected to common. 13.23 are the resonant circuits 12.
22, that is, the capacitors C, 2, C22 and the inductance L12. This is a negative resistance circuit with a grounded base in which the emitter terminal of the transistor is connected to each connection point with L22. The resonant circuit 13.23 consists of a transistor "'T, +'i'2" and an inductance I,13+L2 connected between the respective base and common.
S is made up of 3 and 3. R1 and R2 are the outputs of the negative resistance circuits 13 and 23, that is, the transistors 1trl, respectively.
DC bias resistors C1, C23 connected between the collector terminal of + 'rt-2 and the power supply voltage VcC are connected between the collector terminals of transistors 'rr, 'r''r2 and output terminal 2, respectively. This is an AC coupling capacitor to be connected.

The operation of the voltage controlled oscillator configured as above will be explained next. FIG. 2(A) is a diagram showing the frequency characteristics of the negative resistance port #tl 3°23, where the negative resistance band is between frequencies fa and fb. FIGS. 2(B) and 2(C) show the resonant circuit 12.
22, in which al and C3 are the switching voltage V
, , 0 frequency bands al and a2, which indicate adjacent resonance frequency bands when V2 is 0, are both within the negative resistance band, so when V, , V2 is 0, the oscillation condition is satisfied, and each resonance oscillates in the band. Therefore, the control voltage V
By changing C, any frequency output within this oscillation band can be obtained from terminal 2. bl, b2 are switching voltages V
, , V2 is a predetermined force negative switching voltage V,-, V2-, respectively.
The switching voltage V,−,V2 indicates the resonant frequency band when
- is a voltage such that the outputs S, , S2 of the adders 11, 12 become negative and the diodes D, , D2 are turned on, and at this time, the resonant frequencies of the resonant circuits 12, 22 are C12, respectively, and 2 + It is determined by C22 and L2□.

This resonance frequency is because the capacitances of diodes D, D2 are very small compared to CI 2 and C2□, respectively.
(1) The value is much lower than that in normal operation when 1 + V 2 is 0, and is lower than the lower limit frequency fa of the negative resistance band. Therefore, in this state, the oscillation conditions are not satisfied, so
The oscillation circuit does not oscillate, C1 and C2 are switching voltages V, , V
When the switching voltages V, +, V2+ are applied to the adder 11.12, where 2 represents the resonant frequency band at a predetermined positive switching voltage Vj+, V2+, respectively, the output S of the adder 11.12
S2 becomes a very high positive voltage, and this high reverse bias voltage causes the capacitance of the diode DID2 to become a very small value, so that the oscillation frequency becomes higher than the upper limit frequency fb of the negative resistance band. In this case as well, since the oscillation conditions are not satisfied, no oscillation output appears at terminal 2.

That is, in the circuit of Fig. 1, V+-0, V2 = ■2
- or V + = O, V 2 - V 2+,
Only the oscillation output in the a1 band can be obtained from the first oscillation circuit, and V+ = V+-, V2 = 0'& or V+
``If V+ +, V2 = O, only the oscillation output in the a2 band can be obtained from the second oscillation circuit.

According to a voltage controlled oscillator with such a configuration, switching between multiple oscillators is performed not by a power supply but by a control voltage,
Since the DC bias is always applied, problems such as drift immediately after switching do not occur as in the conventional case. Therefore, high-speed switching is possible.

In the above embodiment, a grounded transistor type negative resistance circuit is used, but the present invention is not limited to this, and any other circuit having negative resistance characteristics can be used.

Further, the resonant circuit is not limited to the above-mentioned LC type resonant circuit.

Further, in the above embodiment, two sets of oscillation circuits are switched to perform C, but any plurality of oscillation circuits can be switched by a switching voltage.

C. "Effects of the Invention" As is clear from the above description, according to the present invention, a voltage controlled oscillator capable of high-speed switching of a plurality of oscillation circuits can be realized with a simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the voltage controlled oscillator according to the present invention, FIG. 2 is a diagram showing the frequency characteristics of the resonant circuit and negative resistance circuit of FIG. 1, and FIG. FIG. 2 is a configuration block diagram showing an example of a controlled oscillator.

Claims (1)

[Claims] A voltage controlled oscillator that outputs a signal with a frequency corresponding to a control voltage, comprising: an addition means for adding a switching voltage to the control voltage; and a resonance device whose resonant frequency band is controlled based on the output of the addition means. a plurality of sets of oscillation circuits having different oscillation frequency bands each including a circuit and a negative resistance circuit to which the outputs of the resonant circuits are connected; and an output terminal to which the outputs of the plurality of sets of oscillation circuits are connected; A voltage controlled oscillator characterized in that the oscillation circuit is selected depending on the voltage.