JPS6198001A - Local oscillation device - Google Patents

Abstract

PURPOSE:To make the variation range of an oscillation frequency wider by switching base voltages of a transistor (TR) for amplification according to the on-off state of a switch diode, and increasing or decreasing the base current. CONSTITUTION:Resonance capacity is the serial sum of the capacity of a tuning diode D1, the capacity of the switch diode D2, the input capacity C0b of the TRQ, and stray capacity applied to them in parallel. When the switch diode D2 is on, the base bias of the TRQ is raised through a resistance R8 and the switch diode D3 to flow a more current, and consequently the collector-base voltage VCB of the TRQ is lowered, the input capacity C0b is increased, and the equivalent capacity of a resonance circuit is increased to make the frequency at which the quantity of oscillation is small, thereby widening the frequency variation range.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention is applicable to television tuners, SHF down,
This invention relates to a wideband local oscillation device using a heterodyne method used in converters and the like.

Conventional configuration and problems The line impedance Zin in the distributed constant circuit is as follows: Zoo is the characteristic impedance, ZR is the terminal impedance of the line, and l is the line length.

However, β [cor (λ: wavelength)...■ When zR-0 in the above first equation.

Zin = jZo tan% -...
A resonant circuit can be constructed by using the gap (2) and adding a capacitance to it. Conventionally, a reflection type oscillator is constructed by connecting this resonant circuit to an amplifier.

Figure 5 shows an example, where (A) is the resonator section, ■
is the amplification section. (Ll) is a resonant line, (C1) (C
2) (Cal)' is a large capacity for coupling. The resonant circuit is composed of a resonant line L1, a total capacitance of a varactor diode (Dl) JiCvD, and a stray capacitance Cr of the circuit. If this total capacitance is C6, then at the resonance point.

There is a relationship as follows, and the circuit shown in FIG. 5 oscillates at this ω0.

The variable capacitance range of varactor diodes (Dl) is currently available, for example 0.7 (pF) to 6.0 (pF).
F: l. The maximum oscillation frequency when an oscillator is configured using the varactor diode CDI)' and the resonant line (Ll) is determined by the total capacitance Co and the line length e of the resonant line L1. Line length a is from equation 4 above.

becomes. Also, the current total capacitance Co is 0.5 (pF)
+0.7 CpF] = 1.2 (pF), so if the maximum oscillation frequency is 1750 LMHz) and Zo is 60 [Ω], it becomes /-0,027 (m). However, when the substrate is glass epoxy or alumina, multiply by the wavelength shortening rate.

When using glass epoxy, #-0.027 x O, 49 = 18.1 (when using mml alumina, it becomes 0.027 x 0.88 depth 8.9 (mm). Therefore, a local oscillator was constructed using this line length. Then, the total capacitance required to vary the frequency fo is from the above equation 4.

becomes. Therefore, fo was changed from 8oo [MHz] to 1900.
(The total capacitance co required to change up to MHz:l is calculated as shown in the quadratic table.

[Margin below] Table> In this table, X indicates the capacitance change range.

0.7 (pF) ~ 6 (pF)...
When using the varactor diode (2), a stray capacitance of 0.5 (pF) is added to the total capacitance.

1.2 (pF] ~ 6.5 CpF) =
・It has a variable width of ■, and at this time the frequency fo is 900
(MHz:] to 1750 (MHz).

The calculation results in the table above are based on the characteristic impedance of the resonant line (L,) Zo'' 50 LΩ, the required maximum oscillation frequency fz = 1750 (MHz), and the stray capacitance Ct existing on the resonant line (Ll). −0,5(p
F:], Minimum capacitance CV of varactor diode (Dl)
Dm1n -7 (pF), the above C(t CvIl, m
The line length e necessary to obtain fx at the value of s n
-26,9468 (mm).

In a television tuner circuit, to cover the entire world frequency range, the first ferrous intermediate frequency should be set at 900 (
MHz) band, 1000 LMHz:l is required as one width considering the design margin.

However, this variation range cannot be achieved within the range of the ninth equation. Therefore, conventionally, as shown in FIG. 5, the resonant line (Ll) of the resonator section (2) is divided into e and C2,
A switch diode (Dl) between the dividing point and ground
A heavy pressure is applied through the high resistance (R3) (or choke coil) to the 1st division point, and 6 switch diodes (
By turning on and off the resonant line (Ll)
) is used by changing the length.

However, the switch diode (Dl) has a capacitance CfD (1 (pF) to 2 (pF) in the case of a plastic package) consisting of the reverse bias capacitance and the package stray capacitance.
) exists, so in the region where one frequency is high.

Due to the capacitance D, the resonant line (Ll) is always 7'
Since the resonant line (Ll) is in an alternating current shorted state with a length of l, the resonant line (Ll) always becomes el, and the length of (L + g2) cannot be obtained even when the switch diode (Dl) is non-conducting. The configuration is such that the variable range cannot be expanded in high frequency bands.

Therefore, a local oscillator was proposed that could oscillate over a wide range of frequencies by switching the switch diode between conduction and non-conduction in the high frequency band.
A tuning diode whose capacitance can be varied by an external DC potential, a resonant line, and a switch diode whose conduction/non-conduction can be switched by a second external DC potential are connected in series in an AC manner, and this is connected to the base or collector of the amplification transistor. The common line is interposed between the common line and ground, and when the switch diode is non-conducting, one end of the common line is grounded in an alternating current manner via a capacitor in parallel with the switch diode.

An example of this will be explained below using FIG. 6. The resonator section and the amplifier section (■) are connected by a coupling capacitor (C1).

A high resistance (R
A tuning voltage BT, which is a first external direct current potential, is applied via the terminal (+). High resistance (R1) and coupling capacitance fi (C+)
A varactor diode (Dl), a resonant line (L+), and a switch diode (Dl) are connected in series between the intersection (I) [in AC terms, the amplification transistor (base of Q)] and ground. The connected item is interposed.

Specifically, the cathode of the varactor diode (D, ) is connected to the intersection (1), one end of the resonant line (Ll) is connected to the anode of the varactor diode (Dl), and the other end of the resonant line (Ll) is connected to the high It is grounded through a resistor (R2) and connected to the anode of the switch diode (Dl) through a coupling capacitance fi (Cz).
The cathode of Dl) is grounded. Further, a capacitor CfD is connected in parallel with the switch diode [Dl].

A switch voltage Bs, which is a second external DC potential, is appropriately applied to the intersection of the switch diode (Dl) and the coupling capacitor [(Cz) via a high resistance (Rj).

When the switch diode (Dl) is made conductive by the switch voltage BS in the resonator section, the resonant line (Ll
) is directly grounded via the coupling capacitor (C2), and almost no effect of the capacitance Cfo occurs. Therefore, the resonant capacitance is the sum of the tuning capacitance CvD of the varactor diode (Dl), the coupling capacitance (C+) (Cz), and the stray capacitance cf including ) of the amplifier section, but the coupling capacitance (C+
) Since (C2) uses a large value for the tuning capacity fJh Cvn, the actual total capacity C6 is.

Co #Cvp + Ct −@1.

By the way, when the switch diode (Dl) becomes non-conductive, the switch diode (Dl) is grounded via the capacitor ctD. Here, the capacitance CfD is the coupling capacitance [(C1)(C
2), so this capacitance CT cannot be ignored in series connection, and the total capacitance C0 is:

becomes. Here CB) = 1 (pF), C(-0
,5LpF:l.

Cvo -0.7LpF) to 6LpF:] Then, the variable range of the total capacitance C9 in the above equation 10 is 1.2
(pF) to 6.5LpF, and the frequency change width using the resonant line shown in the table above is 900% in the range of X in the table.
(MHz) to 1750 CMHz) can be obtained. In the case of the above equation 11, the change in the total capacitance Co is 0.91 LpF to 1.85 [pF], which is 2
Y(7) range of 1700 [MHz) to 1900 in the table
(h(Hz) can be obtained. That is, by configuring as shown in Figure 6 and applying the switch voltage BS appropriately, the variable range can be changed to the above Z
O) range, i.e. 900 [8, lz) to 1900
LMH2).

In addition, in the resonator part (2), a varactor diode (
Same for Dl), af! ! , the reverse bias voltage of voltage BT, and the switch diode (Dl) must be turned on and off by the switch voltage Bs, so the resonant line (L, both diodes CD+) (Dz) are inserted in series. The important point is that the direction of the diode (DI) (Dl) is not particularly important. In addition, a switch diode (Dl
As the capacitor ff1c-rn inserted in parallel with ), only the reverse bias capacitance of the switch diode (Dl) may be used, or another capacitor may be set.

The amplifier section ■ consists of a resonator section (2
) is connected, and the collector of the transistor (Q is connected to the large window
CC3). Resistor (RS) in the collector
Along with being biased through.

It is connected to the base via a resistor (R6) and is given a base potential. Regarding base bias.

It does not have to be a self-returning type. The emitter-collector capacitance fkcC4) of the transistor Q is the one that connects the shortest distance between the emitter and the ground to the AC ground.

The capacitance (C4) improves the stability of broadband oscillation. (R2) is a choke coil for extracting high power. (R7) is the emitter resistance, and the coupling capacitance 1
The oscillation output is taken out through (Cs), B=12
(V), about 10 (dB) when 'rl current is about 88 [mA]
m) The output of can be extracted. Note that there are various methods for extracting the oscillation output, including a method in which the capacitance (C3) is set to 10 [pF:] N degrees and the output is extracted from the collector, and a method in which the oscillation output is extracted through inductive coupling or capacitive coupling to the resonant line (Ll). method is also possible. Considering the power, it is best to take it out from the emitter.

There are many ways to extract the output or set the resonant line, but the important point in this example is that the resonant line, varactor diode, and switch diode are arranged in series. .

In the above example, a varactor diode CD+), a resonant line (Ll), and a switch diode (Dl) are interposed between the base of the amplification transistor and the ground, but this is because the configuration of the amplification section (B) is a Clapp type oscillation. A similar effect can be obtained when a resonant element is interposed between the collector of an amplifying transistor and the ground as in a circuit.

However, the varactor diode CDI) and the resonant line (
Ll) 1. In order to absorb the t' fluctuation, it is necessary to further expand the variable range by 100 (MHz) or more, especially in the minimum oscillation frequency part.On the other hand, the configuration shown in Figure @6 has the disadvantage that it is difficult to expand it any further. was there.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a local oscillation device that overcomes the above-mentioned conventional drawbacks and can further expand the variable range of one oscillation frequency.

Structure of the Invention In order to achieve the above object, a local oscillation device fist of the present invention is provided.
is a tuning diode whose capacitance is varied by a first external DC potential, a resonant line, and conduction by a second external DC potential.
A series circuit in which a switch diode that can be switched to non-conductivity is connected in series, this series circuit is connected to an amplification transistor in series to the base or collector, and the above-mentioned circuit is connected in series with a switch diode that can be switched to be non-conductive. The configuration includes a control means for increasing/decreasing the base current by switching the base voltage of the amplifying transistor.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below based on a drawing. Figure 1 is a circuit diagram of a local oscillator in an embodiment of the present invention, and the same components as shown in Figure 6 are used. Components are given the same reference numerals. In Figure 1, (4) is the resonator section, and ■ is the amplification section. The resonator part (2) is an amplification part (G)
A tuning voltage BT, which is a first external DC potential, is applied through a high resistance (R+). The cathode of a tuning diode [Dl] is connected to the connection point between the coupling capacitance (C1) and the same resistance (R1), one end of the resonant line (Ll) is connected to the anode, and the other end of the resonant line (Ll) is connected to the anode. is grounded through a high resistance (R2) and connected to a switch diode (Dl) through a coupling capacitance (C2). The connection point between the coupling capacitance 1 (Cz) and the switch diode (Dl) is.

Stray capacitance CF2 and specific capacitance [switch diode (
It is grounded by the capacitance of Dl) when it is conductive and when it is not conductive.

Further, a switch voltage BS, which is a second external DC potential, is applied to the connection point between the coupling capacitor (C2) and the switch diode (Dl) through a high resistance (R3).

The base of the transistor (Q is connected to the terminal (Bs) via the switch diode (D3) and the bias resistor (Rs). The collector of the transistor (Q is connected to the large window @CCs) It is grounded via a resistor (Ri), and is further connected to a base via a resistor (R6).The base potential is provided by the resistor (R6).

The base bias does not have to be of the self-feedback type, and the voltage applied to the base of the transistor' (Q) via the switching diode (D3) and bias resistor (Rs) is not necessarily from the terminal (Bs). Does not need to be supplied. The capacitance fEt (C4) between the emitter and collector of the transistor (Q) is to ground the shortest distance between the emitter and the ground in an alternating current manner, and this capacitance (C4)
This improves the stability of broadband oscillation. (R2)
is a choke coil for extracting high power.

(R7) is an emitter resistor that takes out the oscillation output through the capacitor (Cs), and can take out a power of about 10 [dBm] at a current of 88 (mA).

There are 3M methods for extracting the oscillation output.
It is not directly related to the present invention.

In this oscillation circuit, the resonant capacitance is a tuning diode (D
l) capacitance CVD, switch diode (Dl) capacitance @CVS (OFF) or cv5 (ON), transistor (Q's input capacitance C8b, and stray capacitance added in parallel to each of these.@ It is the column sum.CV(
Since OFF) < CV(ON), one oscillation frequency for the same resonant line (Ll) is C as shown in Figure @2.
ζ, D2=OFF and +Dl-ON■ change. In this case, the change in the above two oscillation frequencies is caused by the tuning voltage BT at the frequency given by D," OFF.
with a low area.

When Dl=ON, the frequency given by the tuning voltage BT becomes the same frequency as the high range, and the range of change is equivalently narrow in many cases. Therefore, in order to obtain the desired frequency range, in the practical example, when ON, as shown in Fig. 1, through the resistor (R8) and switch diode (D3),
By increasing the base bias of the transistor (Q) and allowing more current to flow, the collector-base voltage VCB of the transistor (Q) is lowered and the input capacitance C is increased as shown in Figure 8.
Increase the value of 8b, increase the equivalent capacitance of the resonant circuit, and decrease the minimum frequency of one oscillation.

We are trying to expand the variable range.

Regarding the switch diode (D3), only when the switch voltage BS is at a high potential, the base potential of the transistor (Q) is increased, and when the switch voltage BS is at a low potential, the base potential of the transistor (Q) is not changed compared to the conventional one. It is intended for this purpose.

In the absence of this, when the switch voltage Bs is at a low potential, the base potential of the transistor (Q) decreases, and the current of the transistor (Q) decreases.At this time, as shown in FIG.
Since the value of 8b decreases and the variable range of high frequencies can be expanded, it is not necessarily necessary to provide a switch diode (D3).

As described in detail, according to the present invention, the variable range of oscillation frequency can be expanded with a simple configuration, and there is almost no increase in cost.

[Brief explanation of the drawing]

Figure m1 is a circuit diagram of a local oscillation device in an embodiment of the present invention, Figure 2 is an explanatory diagram of the relationship between oscillation frequency and tuning voltage,
Figure 8 is an explanatory diagram of the relationship between VCB and Cob of a transistor, Figure 4 is an impedance characteristic diagram of a single-sided terminated ^/4 line, and Figures 6 and 6 are circuit diagrams of conventional local oscillator devices, respectively. be. (2)...Resonator section, only...Amplification section, CL+)--
resonant line.

Claims (1)

[Claims] 1. A tuning diode whose capacitance is varied by a first external DC potential, a resonant line, and a second external DC potential that conducts each other.
A series circuit in which a switch diode that can be switched to non-conduction is connected in series, this series circuit is connected to an amplifying transistor in series to the base or collector, and A local oscillation device comprising control means for increasing and decreasing base current by switching the base voltage of an amplifying transistor. 2. The local oscillation device according to claim 1, wherein the control means is configured to supply the second external DC potential to the base of the amplification transistor via a resistor. 3. The local oscillation device according to claim 1, wherein the control means is configured to supply the second external DC potential to the base of the amplification transistor via a resistor and a diode.