JPS5842326A - Converter circuit - Google Patents

Abstract

PURPOSE:To obtain a converter circuit which can receive stable signals with high gain for a high frequency stage, through the correction of oscillation phase of a local oscillator. CONSTITUTION:A high frequency signal received at a bar antenna 1 is amplified at a high frequency stage including a transistor (TR) 8 and inputted to a mixing oscillation TR9. An intermediate frequency component out of outputs of the TR9 is picked up at an IFT7 and the TR9 is oscillated at the resonance frequency of a local oscillation coil 6. The secondary winding of the local oscillation coil 6 becomes a voltage source equivalently, one side (a) of the said winding is connected to an equivalent circuit consisting of an output resistor of the TR8, load resistors 11, 13 and correction capacitors 12, 14 and another side (b) is connected to an input equivalent circuit of the TR9. The value of the correction capacitor 12 is selected in the range that the local oscillation can stably be set at the upper limit of the local oscillation frequency without decreasing the load impedance of the TR8 to a value than required. The value is about 2-50pF.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a mixed generator equipped with a high frequency amplifier circuit with a resistive load.
Concerning phase correction in circuits.

In recent years, there has been a strong trend toward miniaturization of receivers, and pocket radios and ultra-compact radios are increasingly using high-frequency amplification circuits with resistive loads that do not require high-frequency transformers or triple variable capacitors. In addition, in order to reduce costs, increase power, and reduce size, circuit systems that use a small number of components (that is, one amplifier circuit performs local oscillation and frequency conversion) have become mainstream.

Conventionally, a converter circuit has the configuration shown in FIG. 1, and a bar antenna 1 captures a target frequency, a transistor 4 amplifies the high frequency, and inputs it to a mixed oscillation transistor 5. The resistor 2 serves as a load resistor for the high-frequency amplification transistor 4, and at the same time forms an oscillation loop tube for the transistor 6 together with the S8 oscillation coil 3. It is necessary to input the gain of the high frequency amplification (K requires a large resistance 2). However, in order for the tone XI5 to stably locally oscillate at a high frequency that falls below the kf- of the tone I in the Q of the local oscillator coil, The resistance in the feedback loop must be small, and the input capacitance of the transistor Is causes a phase shift of the feedback signal to prevent local oscillation from occurring at high frequencies.
+? If resistor 2 is made smaller than 6, the oscillation will be stabilized, but the disadvantage is that the gain cannot be obtained). The problem is that high frequencies cannot be received;

There was a drawback that the operating point of transistor 5 changed too much depending on the input.

An object of the present invention is to eliminate the above-mentioned drawbacks (by phase correction) and realize a compact 2-geo converter circuit with a large high frequency gain and a stable local oscillator.

The present invention will be explained in detail below based on FIGS. 2 to 4. FIG. 2 shows an embodiment of the present invention, which is an example of application to a medium-wave AM band ultra-compact radio. 1 #i bar antenna, 6 is local oscillator coil, 7 is 11 pieces (intermediate same wave transformer), 8 is 4-
A transistor for noise high frequency amplification, 9 a transistor for mixed oscillation, 10 F1 radio circuit integrated circuit radio 10, 11 resistance for load of high frequency amplification transistor 8, 13 for bias of mixed oscillation transistor 9. The resistors 12 and 14 are phase correction capacitors that correct the phase delay of the oscillation feedback signal of the transistor 9).If the capacitance is small, it is necessary to connect the resistors 12 and 14 between the opposing patterns formed on the front and back sides of the double-sided printed circuit board. , Utilizes the capacitance of the mesh wiring pattern to reduce the number of parts and space. Also, it may be connected in parallel with either of the phase correction capacitor resistor 11 and the resistor 13. Furthermore, when using the wiring capacitance of a printed circuit board, it can be connected from the collector of the transistor 8 to the local coil 6. If all the capacitances at wiring point Ca] t are equivalently expressed as phase correction capacitances 12 and 14, it is necessary for correction! Divide the capacitance t2 and resistor 1
2.13 Kt stones connected in parallel.

Next, the operation will be explained. A necessary electromagnetic wave signal is picked up by the antenna 1, amplified by a high frequency amplifier circuit including a transistor 8, and inputted to a transistor 9 for mixed oscillation via the oscillation feedback e-line of the local oscillation coil 6. Out of the output of the transistor, the intermediate frequency component is extracted by the 1-tare, and the oscillating frequency component is extracted by the local oscillator coil 6.0 local oscillator coil 60 The polarity of the first and second windings becomes positive feedback. Dear KWI!
Therefore, the transistor 9 oscillates at the resonant frequency of the local oscillator coil 6.

Next, the cause and correction method of the occurrence of the phase deviation of the oscillation feedback signal will be explained with reference to Fig. 3, Fig. 4, and Fig. 5. The 3rd WJ is y of phase luck due to the equal path! , jl', FIG. 4 shows the phase with respect to frequency, and FIG. 5 shows the oscillation intensity with respect to frequency. In FIG.
The secondary *m indicates a voltage source, and 16 is a transistor!
This is an output equivalent circuit with a time constant consisting of a parallel resistance of 1 and 13, and a phase correction capacitor 9° or (Os and input capacitance 0 (input equivalent circuit with time constant tube consisting of external 0) 1 point and 6 regardless of frequency
Since the phases of the points are the same, the time constants of the input equivalent circuit 16 and the output equivalent circuit must be equal to each other. For example, '*t/Rg/Rs in Ra*/R11 3 e 5
K QRjs=+500KQ O4n=2.5P'! However, if R6 is the output resistance of the collector of transistor 8, O4s in O1 x R4s: ' u / 3 in Ru
60F? As shown in Figure 4, if 0 carbon dioxide is smaller than this, then
The voltage at 6 points will have a phase delay at high frequencies. This is because a delay circuit is formed by the resistance of the output equivalent circuit 16, O(s) of the input equivalent circuit 17, and the long sword resistance R(s. Therefore, when O,==Q, the phase is delayed from 8QQKEIm, and @MEN The K that prevents the local oscillation from stopping at a frequency higher than the amount of 1 phase delay n, which causes a phase delay close to 90@ in the oscillation feedback signal and stops oscillation, is 0□m5s.
If it is oyy, it is perfect, but CI may reduce the load impedance of the transistor 8 and reduce the gain of high frequency amplification. Above the reception frequency wL number @l, gMH
Regarding z, the impedance according to OK is Z 11-1 / 2 K f (1-27 @ QOl
Since the load resistance without it is 351CO, the high frequency gain will drop by 2f)48 or more. 1).

, x3fiQp7 is not appropriate, as shown in Saba4W4, 27F≦0. ≦59FF fFio, -00 o'clock and a, -3@0? As shown in Fig. 5, the upper limit of the local oscillation frequency is about 'l, the phase delay n is within the range where stable oscillation can be achieved, and the load of transistor 8 There is a condition C that the impedance cannot be lowered to an extremely low value.

(Experimental results show that '1 is in the range NK optimal fI of 2 to 50 Pν
For example, assume that 0 IQ P F i is selected from the conditions for stable oscillation at 2 MHm (often with IIL). 0 at the time of Jin. The impedance is 1.6MH! +
So, when there is no Ω01 in 10 in Za, the load resistance of transistor 8 is 3゜5xΩ
Therefore, the drop in high frequency amplification gain is 1.6M! , but 3
dB gain, and the gain decreases even less under sx-6MnMn.

Moreover, when 0- is about 10P1, the capacitance due to the pairing patterns and wiring patterns formed on the front and back sides of the double-sided printed circuit board can be used. A different way to achieve this is (1) by making the land of the chip component a little larger, and by adding a batanine control space and a power supply pattern on the back side of the land.

(2 lines, 1IIt, thick and long K, and the pattern on the back side is the 7-space or power supply pattern.

(3) Using the pattern under the parts such as a molded tantalum capacitor or a molded tantalum capacitor, tag the opposite patterns on the front and back of the board.

There are other methods.

According to the present invention, the following effects are achieved.

(1) The high frequency amplification section has a high gain (20 to 30
dB) is obtained.

In particular, ultra-compact radios can compensate for the decrease in sensitivity due to the small size of the antenna.

(2) Since the mixed oscillation is performed using one amplifier circuit, the number of components is small and a triple-variable mid-high frequency tuning coil is not required, making it suitable for ultra-miniaturization.

(3) The oscillation stop that occurs at 5g1m due to OR coupling can be corrected without increasing the number of parts by using a butter 7-meter t formed on the substrate. Because liquid tonges! is distal), xO for radio can be made with low power and low cost.

[Brief explanation of the drawing]

Fig. 1 shows a conventional example, Fig. 2 shows a circuit diagram of an embodiment of the present invention, Fig. 3 shows the principle of phase retarding grinding using an equivalent circuit, and Fig. 4 shows the phase with respect to frequency. 5 Figure 1 [Oscillation intensity tube showing wave number 1, Par antenna 2.
. Resistance 3.6. . Local oscillator coil 4,5. . F run shift 0. Engineering FT Q, 9°. 2 Star 10, I for radio
On resistors 11, 13°, resistors 12, 14,. More than phase correction capacitor amount

Claims (1)

[Claims] (1) A high-frequency amplifier with a resistive load, which performs local oscillation and mixing in the same amplifier circuit and performs an OR combination with the high-frequency amplifier to generate a 9 mixed oscillator circuit, a load resistance of the high-frequency amplifier, or a mixed oscillator 11 circuit in the next stage. The resistance-coupled mixed oscillator circuit KjiP, which is equipped with a phase correction circuit connected in parallel with the piping resistor, a local oscillation transformer, and an intermediate frequency transformer, can reach the upper limit of the receiving frequency range due to the significant phase delay of the station S output. A converter circuit characterized in that stoppage of local oscillation that occurs in P is prevented by the phase correction capacitor. @The impedance due to the capacitance of the phase correction capacitor is larger than the load resistance of the high frequency amplifier.
And #i2.2M1 at the upper limit frequency of local oscillation, that is, medium wave
Kll to stably local oscillate about the frequency at imj
lI of 50Pν from the value of phase correction coydenna 12py
! It is characterized by the opposing pads formed on the front and back of the board! The converter circuit according to claims N and 2, characterized in that the converter circuit uses a capacitance between the terminal and the terminal.