JPS58139535A - Frequency synthesizer of radio equipment - Google Patents

Abstract

PURPOSE:To decrease the variable frequency range of a VCO compared with a desired band width, by presetting the oscillating frequency at a level near the desired oscillating frequency for transmission and reception. CONSTITUTION:The oscillating frequency of an oscillator 1 is divided by a fixed frequency divider 2 to produce a reference frequency. This reference frequency and the oscillating frequency of a VCO3 are divided by a variable frequency divider 4 based on the frequency that is decided in response to a channel selecting signal supplied to a controller 5 from a control input terminal 8. Thus a comparing frequency is produced. Then a comparison is carried out through a phase comparator 6, and the control voltage proportional to the difference of comparison is obtained. This voltage is fed back to the VCO3 via an input terminal 18 to form a PLL loop. In addition to a variable capacity diode 16 which forms a part of the PLL loop which varies the frequency, an inductance varying means consisting of PIN diodes 21 and 22 is provided to control the inductance of an oscillating coil 24 in response to the polarity of a transmission/reception changeover control signal that is applied to a terminal 25.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a frequency synthesizer for a two-wave simplex radio.

In general, in two-wave simplex communication in which the oscillation frequency of one frequency synthesizer is switched and shared between transmitting and receiving, in order to secure multiple channels, the VCO (voltage-controlled variable frequency oscillator) of the PLL circuit that constitutes the frequency synthesizer is variable. A wide control range is required. On the other hand, however, if the variable control range is wide, the modulation sensitivity of the VCO becomes large, and the loop gain of the PLL circuit cannot yet be made sufficiently large, so that there is a drawback that the operation becomes unstable or the S/N ratio deteriorates.

The present invention aims to provide a frequency synthesizer for radio equipment in which the entry point is eliminated, and will be described below along with embodiments thereof.

FIG. 1 shows a schematic configuration of a frequency synthesizer according to an embodiment of the present invention, in which 1 is an oscillator that generates a reference frequency, 2 is a fixed frequency divider with a fixed frequency division ratio, and 3 is a VCO.
14 is a variable frequency divider whose frequency division ratio can be varied, 6 is a controller that controls the frequency division ratio of the variable frequency divider, 6 is a phase comparator, 7 is a terminal where an oscillation output is generated, and 8 is a channel selection terminal. An input terminal to which a control signal is applied, 18 is an input terminal to which a phase comparison signal is input, and 26 is an input terminal to which a transmitter/receiver 1 converter blade is applied (described later).

With the above configuration, the oscillation frequency of the oscillator 1 is divided by the fixed frequency divider 2 to generate a reference frequency.

and the oscillation frequency of VCO3 from control input terminal 8! fil
In response to the channel selection signal to the controller 6, the electronic 1,
The variable frequency divider 4 divides the frequency L2 to generate an upper axis frequency of 1, and the phase comparator 6 compares the ratio iiQl-1 to obtain a control voltage proportional to the difference of 2, which is applied to the VCO 3. The signal is fed back through the JJ terminal 18, forming a PLL loop.

FIG. 2 shows the yc of the frequency/sensizer.

3 is a circuit diagram showing a specific configuration example of No. 3, in which 11 is an oscillation transistor, 12 is a high frequency choke coil connected to the collector of this transistor 11, and 13 is a transistor 11.
emitter resistance, 14.16 is the tuning capacitor, 1
6 is a variable capacity diode, 17 is a high frequency choke, 19
is a coupling capacitor, 20 is an oscillation coil, 21.22
is a PIN diode for grounding the intermediate point and terminal point of the oscillation coil 2o to ground t1. 23 is a high frequency choke coil, 24 is a resistor for current control, and 26 is an input terminal for a transmission/reception switching signal corresponding to transmission/reception from a call switch (not shown). Controlled by Talk Bokun. 26, 2 is a voltage dividing resistor for setting the base voltage of the oscillation transistor 11, 2 is a bypass capacitor for the base of the transistor 11, and 29 is a power supply terminal of the power supply VB.

Next, the operation of the VCO having the one-to-one configuration will be explained. When the power supply VB is applied to the power supply terminal 29, the oscillation circuit including the transistor 11 is activated by the capacitors 14, 16, and
19. Oscillation coil 20. The oscillation frequency is determined by the value of the variable capacitance diode 16. Therefore, by applying the control voltage from the phase comparator 6 to the variable capacitance diode 16 via the terminal 18 and the high frequency choke 17, the oscillation frequency can be varied in accordance with the channel used. ! , and at the same time transmit/receive the 1J exchange signal through the input terminal 26 and the resistor 24. If the voltage is applied to the PIN diode 21 or 22 via the high frequency choke 23, either one of the PIN diodes 21 and 22 will be turned on depending on the polarity of the transmission/reception switching signal, and the oscillation coil 20 will be connected to the ground. The inductance between can be varied isometrically.

That is, according to the above configuration, the PL for making the frequency variable
In addition to the variable capacitance diode that forms part of the L loop, inductance variable means using PIN diodes 21 and 22 is provided, so the oscillation frequency can be preset near the required oscillation frequency for transmission and reception, and the oscillation frequency can be preset in the vicinity of the required oscillation frequency for transmission and reception. Since the variable frequency range can be set relatively narrowly, the drawbacks caused by the too wide variable range of conventional VCOs can be eliminated.

FIG. 3 is a main circuit diagram showing the configuration of another embodiment of the present invention, in which the circuit configuration on the right side of the capacitor 19 in FIG. 2 is partially changed. 31 and 32 are capacitors, 3
3.36 is a high frequency choke, 34.37 is a resistor, 36.
Reference numeral 38 is an input terminal for a transmission/reception switching signal, and other parts are the same as those in FIGS. 1 and 2.

By inputting a transmission/reception switching signal to the input terminal 35.38 and selectively applying these to the PIN diode 21.22 via the resistor 34.37 and the chokes 33 and 36, either of the PIN diodes 21.22 By turning on one side, the equivalent inductance of the oscillation coil 20 is switched. Other operations are similar to those in the previous embodiment. In the above configuration, the input terminal 36
The oscillation frequency can be changed depending on which side of 0.38° the voltage is applied.

FIG. 4 is a main circuit diagram showing the configuration of another embodiment of the present invention, in which 44 is an oscillation coil, 41 and 42 are capacitors, and 43
is a variable capacitance diode, and the other structures are the same as those shown in FIGS. 1 and 2. In this embodiment, the input terminal 2i
By applying a DC voltage to the variable capacitance diode 43 and changing its capacitance in accordance with the polarity of the transmission/reception switching signal applied to the oscillator coil 19, an effect similar to that of changing the inductance of the oscillation coil 19 can be obtained. be able to.

As explained below, the present invention uses a part of the PLL, . A first frequency variable means consisting of a variable capacitance diode, a PLL that changes and presets the oscillation frequency in response to the transmission/reception 1 of the i+Th talk switch, and the horn exchange.
Since the second frequency variable means that does not include a loop is provided, the variable frequency range of the VCO can be selected to be narrower than the required band [1], and therefore the loop gain of the PLL circuit can be maintained large and the oscillation frequency can be adjusted. It has advantages such as keeping the frequency stable and improving S/N well, and is particularly effective as a frequency synthesizer when the interval between transmitting and receiving frequencies is large compared to the frequency variable range due to channel changes.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a frequency synthesizer according to an embodiment of the present invention, and FIG. 2 is a circuit diagram of 700 parts of the same main part.
FIG. 3 is a circuit diagram of the main parts of the shell of the VCO section of another embodiment.
...VGO14...Variable frequency divider, 6...
・Phase comparator, 16... Town transformation (jl, diode, 2o... Oscillation coil, 21.22... PI
N diode, 18... Input terminal for phase comparison signal, 26... Input terminal for transmission/reception switching signal.

Claims (1)

[Claims] a reference frequency source, a voltage-controlled oscillator, a variable frequency divider that divides the oscillation frequency of the oscillator in accordance with the channel frequency of the radio, and a variable frequency divider that divides the oscillation frequency of the oscillator in accordance with the channel frequency of the wireless device; a phase comparator that generates a voltage, a first frequency variable means controlled by the output of the phase comparator; A frequency synthesizer for a radio device, comprising a second frequency variable means for changing the frequency by a predetermined transmission/reception frequency interval.