JP2868238B2 - Voltage controlled oscillator unit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a voltage-controlled oscillator unit built in an electronic device such as a transmitter or a receiver.

[Prior Art] In a conventional voltage controlled oscillator unit, an oscillation circuit having an oscillation transistor, an amplification circuit having an amplification transistor and amplifying an output of the oscillation circuit, and an output of the oscillation circuit according to a change in an input signal are provided. An electronic component that constitutes an oscillation control circuit that modulates the signal is mounted on one surface of a single circuit board. An earth pattern is formed on the other surface of the circuit board.

[Problems to be Solved by the Invention] In recent years, with the spread of car phones and mobile phones,
There has been a strong demand for downsizing the voltage controlled oscillator unit. However, in the conventional configuration in which all the electronic components are arranged on one surface of the circuit board, there is a limit to downsizing the unit.

The inventor has conceived of miniaturizing the unit by distributing electronic components on both sides of the circuit board and reducing the shape of the circuit board. However, it has been found that when electronic components are appropriately mounted on both sides of the circuit board, parasitic oscillation often occurs and a phenomenon in which the frequency fluctuates suddenly (frequency jump) occurs.

SUMMARY OF THE INVENTION An object of the present invention is to provide a voltage controlled oscillator unit that can prevent occurrence of parasitic oscillation and frequency skipping when electronic components are mounted on both sides of a circuit board to reduce the size of the unit. .

Means for Solving the Problems A voltage controlled oscillator unit to be improved by the present invention is an oscillation circuit having an oscillation transistor, an amplification circuit including an amplification transistor and amplifying an output of the oscillation circuit, and an input circuit. A voltage-controlled oscillator unit in which electronic components constituting an oscillation control circuit that modulates an output of the oscillation circuit in accordance with a change in a signal are mounted on both sides of a circuit board.

According to the first aspect of the present invention, the circuit board is divided into a first double-sided mounting portion and a second double-sided mounting portion. The first double-sided mounting portion includes at least an oscillation transistor and an electronic component forming an output side circuit of the oscillation transistor among electronic components forming an oscillation circuit and a circuit pattern for mounting an electronic component forming an amplification circuit. A circuit pattern to be mounted is formed. A circuit pattern on which electronic components forming the oscillation control circuit are mounted and a circuit pattern on which electronic components forming the input-side circuit of the oscillation transistor of the oscillation circuit are mounted are formed on the second double-sided mounting portion. I have.

According to the second aspect of the present invention, a circuit pattern on which an electronic component constituting a bias circuit of the oscillation transistor is mounted is formed on at least one of the first double-sided mounting portion and the second double-sided mounting portion.

According to the third aspect of the present invention, of the electronic components constituting the bias circuit of the oscillation transistor and the bias circuit of the amplification transistor, the electronic component is disposed on the surface of the circuit board opposite to the surface of the circuit board on which the corresponding transistor is mounted. The electronic components to be arranged are centrally arranged close to the corresponding transistors.

[Operation of the Invention] The inventor of the present application has found that the cause of the occurrence of the parasitic oscillation and the frequency jump is the arrangement state of the electronic components, that is, the arrangement state of the circuit patterns formed on both surfaces of the circuit board. The variation of the output voltage (variation of several volts) of the oscillation transistor of the oscillation circuit and the amplification transistor of the amplification circuit constituting the voltage controlled oscillator unit is the variation of the voltage signal (of several mV width) in the oscillation control circuit. (Amount of fluctuation), and the output of the oscillation transistor and the amplification transistor is a high frequency (for example, 1 MHz to 800 MHz). Therefore, a circuit pattern having a large voltage fluctuation and a high-frequency signal flows and a circuit pattern having a small voltage fluctuation coexist on the same circuit board.

As shown in FIG. 3A, a circuit pattern CP1 to which an amplifying transistor Tr is attached is formed on one surface of a part of the circuit board 4, and an oscillation control circuit is provided on the other surface of the circuit board 4. Considering a case where a circuit pattern CP2 with a small voltage fluctuation to which the constituent electronic components (for example, the capacitor C is shown) are attached is provided so as to face the circuit pattern CP1, the circuit patterns CP1 and CP2 Between the floating capacitances C11, C12,. These stray capacitances can be considered that the stray capacitance components are connected in parallel to the capacitor C when viewed from the capacitor C. As a result, the characteristics of the electronic components forming the input side circuit of the oscillation transistor and the oscillation control circuit apparently change in accordance with the change in the stray capacitance. The inventor has found that this change in stray capacitance is a cause of large occurrence of parasitic oscillation and frequency jump.

According to the first aspect of the present invention, in order to eliminate the cause as much as possible, the circuit board is divided into a first double-sided mounting portion and a second double-sided mounting portion, and the circuit pattern of each circuit constituting the unit is set as described above. With this arrangement, a circuit pattern having a large voltage fluctuation and flowing a high-frequency signal is not substantially opposed to a circuit pattern having a small voltage fluctuation via a substrate. As a result, when electronic components are mounted on both sides of the circuit board, it prevents the electronic components mounted on the circuit pattern with small voltage fluctuations from being affected by stray capacitance fluctuations and causing parasitic oscillations and frequency jumps. Is done.

The circuit pattern on which the electronic components constituting the bias circuit of the oscillation transistor are mounted has neither large voltage fluctuation nor high-frequency signals. Therefore, this circuit pattern may be formed on either the first double-sided mounting part or the second double-sided mounting part.

FIG. 3B shows an electronic component provided on a surface (rear surface) opposite to a surface of a circuit board on which a corresponding transistor is provided, among electronic components constituting a bias circuit of an oscillation or amplification transistor. 4 shows an example of the best mounting mode of a component. Incidentally C ₀ is a bypass capacitor in FIG, H is a through-hole conductors. As shown, when electronic components constituting a bias circuit provided on the back surface of the circuit board 4 are concentratedly arranged close to the corresponding transistor as shown in the figure, stray capacitances C21 and C22 between circuit patterns opposed to each other on both surfaces of the board 4 are provided. Can be minimized. Also the capacitor C ₀ to the stray capacitance C21, C22 are connected in parallel, Q value stray capacitance when viewed in [= R / ωL = R ( C / L) 1/2] plays an effect of increasing the Q value, C / N ratio and S / N ratio can be increased. In the experimental example, the C / N ratio is 80d at 380MHz to 255MHz.
It was confirmed that the B / S / N ratio can be increased by 50 dB in the same range from 380 MHz to 255 MHz. Further, since the length of the wiring portion connecting the electronic components arranged on both sides of the substrate is shortened, the impedance between the circuit patterns can be minimized. Therefore, it is sufficient to use a component having a constant close to the design theoretical value, and it is not necessary to determine the component constant from the actually measured value, and the design is very easy.

Embodiment An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a circuit diagram of a voltage controlled oscillator unit according to an embodiment of the present invention in which electronic components are dispersedly arranged on both sides of one circuit board. In FIG. 1, reference numeral 1 denotes an oscillation control circuit, and 2 denotes a Colpitts type LC. An oscillation circuit, and 3 is an amplification circuit. The oscillation control circuit 1 includes a modulation circuit 1a and a tuning circuit 1b. The modulation circuit 1a includes resistors R1 to R3 and capacitors C1 and C2.
And a varactor diode that is a variable capacitance diode, that is, a varicap D1. The signal input from the control terminal t1 is divided by the voltage dividing ratio between the resistors R1 and R2 and applied to the varicap D1. Capacitor C2 is a coupling capacitor and has a much larger capacity than capacitor C3. In the present embodiment, the capacitor C2 is connected to the varicap D1 of the modulation circuit 1a and the transistor Tr of the oscillation circuit 2.
Although the capacitor C2 is connected to the base 1, the capacitor C2 may be disposed between the varicap D1 and the connection point of the capacitors C3 to C5. The tuning circuit 1b includes a resistor R3, a capacitor C3, and a varicap D2.

The LC oscillation circuit 2 includes an oscillation transistor Tr1 and a resistor R5
R8, capacitors C4 to C9, and a coil L1 for tuning. The capacitor C4 and the coil L1 form a coupling circuit. Capacitor C5 is a coupling capacitor, resistors R5 and R6 are base bias resistors, resistor R7 is an emitter resistor, resistor R8 is a collector bias resistor, capacitors C5 and C7 are coupling capacitors, capacitors C8 and C10.
Is a bypass capacitor. In this embodiment, the coil
By changing the inductance of L4, the oscillation frequency of the carrier to be modulated is determined. Then, the oscillation frequency of the oscillation circuit 2 fluctuates according to the modulation signal from the oscillation control circuit. Incidentally, the frequency increases as the signal input to the control terminal t1 increases, and conversely, the frequency decreases as the input signal decreases.

The amplifier circuit 3 includes a transistor Tr2, resistors R9 to R11,
Consists of capacitors C10 and C11 and a load coil L2,
One end of the coil L2 is connected to the DC power supply terminal t2, and one end of the coupling capacitor C11 between the outputs is connected to the output terminal t3. Resistor R10 is a base bias resistor, resistor R11 is an emitter resistor, and capacitor C10 is a bypass capacitor.

In the circuit diagram, H1 to H8 are through-hole connecting portions for electrically connecting circuit patterns formed on both surfaces of the substrate. The through-hole connection portions H1 and H2 are provided on the back surface of the substrate for disposing the oscillation control circuit 3, and the through-hole connection portions H3 and H5 are provided on the back surface of the substrate for disposing the oscillation circuit bias circuit. The through-hole connection H4 is provided to reduce the mounting density of the board surface by mounting components such as the bypass capacitor C8 on the back of the board, and the through-hole connection H6 and H7 are amplified on the back of the board. The through-hole connecting portion H8 is provided for arranging a bias circuit of the circuit, and is provided for mounting components such as the bypass capacitor C8 on the back surface of the substrate to reduce the mounting density on the surface of the substrate.

A case in which electronic components forming the above circuit are mounted on a circuit board will be described. In order to downsize the unit,
Electronic components use chip components. A printed resistor can be used as the resistor. A predetermined circuit pattern is printed and formed on both sides of the circuit board, and the chip electronic components are soldered by reflow soldering or the like to mount the electronic components. FIG. 2A is a schematic plan view showing an example of a mounting mode of the chip electronic component on the circuit board 4, and FIG. 2B is a schematic side view. In this embodiment, the circuit board 4 is divided into a first double-sided mounting part 4a and a second double-sided mounting part 4b, and the electronic parts constituting the amplifier circuit 3 are mounted on the first double-sided mounting part 4a. A circuit pattern and a circuit pattern for mounting at least the oscillating transistor Tr1 of the electronic components forming the oscillating circuit 2 and the electronic components (capacitors C7, C8...) Forming the output side circuit of the oscillating transistor are formed. In the second double-sided mounting portion 4b, a circuit pattern on which electronic components constituting the oscillation control circuit 1 are mounted and electronic components (capacitors C4, C5, coils) constituting the input side circuit of the oscillation transistor Tr1 of the oscillation circuit 2 L1 etc.) are formed. Oscillation transistor
Electronic components that make up the bias circuit of Tr1 (resistances R5, R6, etc.)
May be attached to either the first double-sided mounting part 4a or the second double-sided mounting part 4b.

Looking specifically at the state of attachment of the electronic components, the first
On one surface (front surface) of the double-sided mounting portion 4a, an electronic component excluding a coupling circuit (C4, L1) of the oscillation circuit 2 and an electronic component constituting a part 2a of the bias circuit, and a bias circuit 3a are provided. The electronic components constituting the removed amplifier circuit 3 are mounted and the second
On the surface of the double-sided mounting portion 4b, a coil L1 and a capacitor C4 that constitute a coupling circuit of the oscillation circuit 2 and a transistor Tr1
Part of the electronic components (capacitor
C5, C6, etc.) are implemented.

FIGS. 2A and 2B show transistors Tr1 and Tr
2, mounting positions or modes of the coil L1 and the like are shown as examples. Most of the electronic components constituting the oscillation control circuit 1 are mounted on the other surface (back surface) of the second double-sided mounting portion 4b of the circuit board 4, and the oscillation circuit is mounted on the back surface of the first double-sided mounting portion 4a. Part 2a of the bias circuit 2 and the bias circuit of the amplifier circuit 3
3a has been implemented. The electronic components (C9 to C1) constituting the bias circuits 2a and 3a mounted on the back surface of the circuit board 4
1, R5, R10,) are concentrated and mounted as close to the corresponding transistor as possible.

In the present embodiment, most of the electronic components constituting the oscillation control circuit 1 are replaced with a second voltage-insensitive second-sided mounting portion 4a which is not affected by the first double-sided mounting portion 4a on which a circuit pattern through which a high-frequency signal flows is formed. Since it is mounted on the back side of the double-sided mounting part 4b, the area ratio is 2/3 compared to the conventional unit
The substrate can be made as small as possible.

The voltage fluctuation of the circuit pattern to which the electronic component (C4, L1) mounted on the surface of the second double-sided mounting part 4b is attached is
It is about 40-50mV for power supply voltage 5V, and transistor
It is very small compared to the voltage fluctuation (1 to 5 V) of the output of Tr1 and Tr2. Therefore, the stray capacitance between the circuit patterns formed on both surfaces of the second double-sided mounting portion 4b is small, and the fluctuation is very small. Therefore, on the back surface of the second double-sided mounting portion 4b, an electronic component (for example, a varicap or a capacitor) whose apparent capacitance fluctuates due to the addition of stray capacitance.
There is no problem if is implemented. First double-sided mounting part 4a
When the circuit pattern of the oscillation control circuit 3 is formed on the back surface of
It is greatly affected by stray capacitance. For example, the second
The electronic component constituting the oscillation control circuit 3 is mounted on the back surface of the double-sided mounting portion 4b of
If the varicap D1 or D2 is mounted on the back surface of the first double-sided mounting portion 4a and especially at a position opposite to the circuit pattern on which the transistor Tr1 or Tr2 is mounted, the change in the capacitance will be wide if it is assumed to change within the range of pF to 10pF. Has been experimentally confirmed to be between 2 pF and 11 pF. This increase in capacitance is due to the effect of the stray capacitance, and the transistor Tr1 or T1
The effect decreases as the distance from r2 increases. By the way, the transistor Tr1 or T
It was confirmed that the stray capacitance was reduced by almost 70% even if the mounting position of the varicap was shifted by 1 mm from the position facing the circuit pattern where r2 was mounted to the position not facing it. The length dimensions of the chip transistor and the varicap used in the experiment are about 1 to 2 mm.

In this embodiment, basically, an electronic component (AC element component) for flowing an AC signal is arranged on one surface (front surface) of the circuit board 4 along the flow of the signal, and the other surface (back surface) of the substrate is provided. The arrangement of the electronic components is determined under the design concept of arranging the electronic components (direct current component components) that flow the DC signal. For this reason, there is no electrical influence that may cause a malfunction between the electronic component and the circuit pattern arranged on the same surface side, and the reliability can be improved.

In the present embodiment, all of the electronic components constituting the oscillation control circuit 1 are mounted on the back side of the circuit board 4. However, some of the components may be mounted on the front side of the board 4. It is.

The present invention is not limited to the above embodiment,
As shown in FIG. 2 (C), most or all of the electronic components constituting the oscillation control circuit are placed on the same side (surface) as the surface on which the transistors Tr1 and Tr2 of the second double-sided mounting portion 4b of the circuit board 4 are arranged. Side). When the coil L1 and the capacitor C4 are mounted on the back side of the board, the second double-sided
Mount on the back side of 4b. It has been confirmed that the coil L1 is also affected by the stray capacitance similarly to the capacitor.

In each of the above embodiments, the transistors Tr1 and Tr2 are arranged on the same surface of the circuit board. However, it goes without saying that each transistor may be arranged on a different surface of the circuit board.

The unit in which the electronic component is mounted on the substrate as described above is housed in a tinable shield case that can be soldered. In the above embodiment, in order to determine the oscillation frequency by adjusting the interval between turns of the coil L1,
A window is provided in the shield case at a position corresponding to the coil L1.

Note that the present invention is not limited to the above embodiment, and it is needless to say that the present invention can be applied to a case where a Hartley-type oscillation circuit or another oscillation circuit is used as the oscillation circuit.

According to the first aspect of the present invention, a circuit board is divided into a first double-sided mounting portion and a second double-sided mounting portion, and the first double-sided mounting portion forms an electronic component constituting an amplifier circuit. And a circuit pattern for mounting at least an oscillating transistor and an electronic component forming an output-side circuit of the oscillating transistor among the electronic components forming the oscillating circuit. Forms a circuit pattern on which the electronic components that constitute the oscillation control circuit are mounted and a circuit pattern on which the electronic components that constitute the input side circuit of the oscillation transistor of the oscillation circuit are mounted, and minimizes the adverse effects of stray capacitance. Since the circuit pattern of each circuit is formed on the circuit board so as not to occur, occurrence of parasitic oscillation and frequency jump can be effectively prevented.

According to the third aspect of the present invention, among the electronic components constituting the bias circuit of the transistor, the electronic components arranged on the other surface side of the circuit board are intensively arranged close to the corresponding transistor. Stray capacitance and circuit pattern inductance can be minimized,
There is an advantage that the design becomes very easy.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a voltage controlled oscillator unit according to an embodiment of the present invention. FIG. 2 (A) is a schematic plan view of a board for explaining a mounting method when mounting an electronic component on a circuit board.
2 (B) is a side view of FIG. 2 (A), FIG. 2 (C) is a side view of a mounting board showing a mounting state of a different embodiment, FIG.
FIGS. 7A and 7B are explanatory diagrams for explaining the effect of stray capacitance. 1 ... Oscillation control circuit, 2 ... Oscillation circuit, 3 ... Amplification circuit, 4 ... Circuit board, R1 to R11 ... Resistance, C1 to C11 ... Capacitor, Tr1 ... Oscillation transistor, Tr2 ... Amplification Transistors, L1, L2 ... coil, H1 to H8 ... through-hole connection.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification symbol FI H05K 3/46 (56) References JP-A 1-2222503 (JP, A) JP-A 2-279027 (JP, A) JP-A-3-6853 (JP, A) JP-A-63-170988 (JP, A) JP-A-3-204237 (JP, A) JP-A-55-80910 (JP, U) JP-A-2-75850 (JP, A) JP, U) Actually open 1983-25084 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H03B 1/00-5/18 H05K 3/46 H01L 27/00-27 / 04

Claims (3)

(57) [Claims] 1. An oscillation circuit having an oscillation transistor, an amplification circuit including an amplification transistor and amplifying an output of the oscillation circuit, and an oscillation control circuit for modulating an output of the oscillation circuit according to a change in an input signal. In a voltage-controlled oscillator unit having electronic components mounted on both sides of a circuit board, the circuit board is divided into a first double-sided mounting part and a second double-sided mounting part, and the first double-sided mounting part has A circuit pattern for mounting an electronic component constituting the amplifying circuit, and a circuit pattern for mounting at least the oscillation transistor and an electronic component constituting an output side circuit of the oscillation transistor among the electronic components constituting the oscillation circuit. A circuit pattern on which electronic components constituting the oscillation control circuit are mounted on the second double-sided mounting portion, and the oscillation circuit Voltage controlled oscillator unit, characterized in that the circuit pattern on which an electronic component constituting the input side circuit of the oscillation transistor is mounted is formed. 2. A circuit pattern on which an electronic component constituting a bias circuit of the oscillation transistor is mounted is the first circuit pattern.
The voltage-controlled oscillator unit according to claim 1, wherein the voltage-controlled oscillator unit is formed on at least one of the double-sided mounting part and the second double-sided mounting part. 3. An electronic component constituting a bias circuit of the oscillation transistor and a bias circuit of the amplification transistor, respectively, of the circuit board on a side opposite to a surface of the circuit board on which a corresponding transistor is mounted. 2. The voltage controlled oscillator unit according to claim 1, wherein the electronic components arranged on the surface side are centrally arranged close to the corresponding transistor.