JPS6345132B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a passband adjustment circuit, and in particular has a function generally referred to as shift and width for removing interference signals adjacent to a desired signal.
The present invention relates to a passband adjustment circuit mainly applied to radio receivers.

Normally, the occupied frequency bandwidth of a communication receiver is determined according to the radio wave format, and the main path of the receiving circuit is designed so that the received signal can pass through this occupied frequency bandwidth.
Various circuits are provided according to the format of f _i . The main path of the receiving circuit consists of an antenna 1, an RF unit 2, a mixer 3, a bandpass filter 4, a mixer 5, a bandpass filter 6, and a demodulator 7, as shown in FIG. The frequency of each oscillation signal injected from the local side terminals 3a, 5a, 7a of the mixers 3, 5 and the demodulator 7 to the mixers 3, 5 and the demodulator 7 and the characteristics of the bandpass filters 4, 5 are selected. The passband of the received signal is determined. Focusing on the first and second frequency conversion means provided before and after the bandpass filter, that is, the bandpass filter 4, the mixers 3 and 4 are involved, and the bandpass filter 6 is related to the mixer 5 and the demodulator 7. The frequency of the first and second local signals determines the positional relationship between the center frequency of the bandpass filter and the carrier wave of the received signal _fi , so by operating the width variable resistor 21 or the shift variable resistor 22, the VCO1
It is possible to perform a width operation in which the frequency of the oscillation signal of VCO 7 or VCO 18 is shifted from the normal frequency to change the passband width, or a shift operation in which the positional relationship between the center frequency and the carrier wave is changed. The shift and width remove interfering signals adjacent to the desired signal.

Generally, circuits that convert the frequency of oscillation signals, such as mixers, have the risk of generating unnecessary harmonics. For this reason, the mixers 3, 5 and demodulator 7 provided in the main path are essential circuits and cannot be avoided.
Mixer 1 installed in the PLL loop of PLL circuit 8
2 and 13 can be removed if there is a functionally replaceable circuit, and the multi-signal characteristics can be improved. 1st
In the figure, reference numeral 9 is a phase comparator, 10 is a low-pass filter, 11 is a VCO, 14 is a programmable counter, 15 is a pulse integration counter that forms program information that determines the division ratio of the programmable counter 15, and 16 is a pulse integration counter 15. A pulse generator 20 is a frequency adjustment dial that determines the number and polarity of the cumulative pulses sent from the pulse generator 16 to the pulse cumulative counter 15.

The present invention has been made in consideration of the above-mentioned points, and provides a passband adjustment circuit that can be applied to a wireless communication device incorporating a PLL circuit for local signal generation, and that reduces the need for frequency conversion circuits such as mixers. The purpose is to provide.

The passband adjustment circuit according to the present invention has first and second frequency conversion means provided before and after the bandpass filter as a basic circuit. 1st, 2nd
The first and second VCOs generate first and second local signals to be injected into the frequency conversion means. Voltage variable means such as a variable resistor is provided to control the second voltage controlled oscillator. Analog-to-digital conversion means is provided to convert the amount of voltage change by the voltage variable means into a digital amount. Since the first voltage controlled oscillator is incorporated into the PLL loop together with a programmable counter and is controlled by digital program information, it is configured to add the voltage change amount converted into a digital amount by the analog-to-digital conversion means to this program information. has been done.

An embodiment of the passband adjustment circuit according to the present invention will be described below with reference to FIG.

In FIG. 2, 21 is a width variable resistor. Variable resistor 21 for width changes to VCO1 by operation.
7 and the level of the control signal to the analog-to-digital converter 23. In addition, the shift variable resistor 22 is connected to the analog-to-digital converter 24 and the VCO 18.
Sends control signals to. Note that the control signal forms a control amount using an analog amount such as a DC voltage.

The analog-to-digital converters 23 and 24 convert the control signals input from the width variable resistor 21 and the shift variable resistor 22 into digital quantities, and output the digital quantities to the digital adder 25 via data buses 23a and 24a.

Digital adder 25 is pulse integration counter 15
The program information formed by the data bus 15a
This program information and the digital amounts of the data buses 23a and 24a are added together and sent to the programmable counter 14 of the PLL circuit 8 via the data bus 25a as program information including passband adjustment information.

Here, if an oscillation signal that does not shift is injected into the local side terminals 5a and 7a, the passband width is normal and the center frequency of the passband does not change. When the frequency adjustment dial 20 is rotated forward or backward, the pulse generator 16 sends an integrated pulse to the pulse integration counter 15, and the pulse integration counter 15 forms program information in accordance with the integrated pulse.
The programmable counter 14 of the PLL circuit 8 is provided in the PLL loop with a frequency division ratio according to the program information formed by the pulse integration counter 15.
Divide the frequency of the oscillation signal of the VCO (not shown). Therefore, the frequency of the oscillation signal of the local side terminal 3a is determined following the operation of the frequency adjustment dial 20, and a desired signal can be selected.

Operate the width variable resistor 21 on the operation panel 19. If the reference potential point is set to the normal control signal level, the control signal level increases by operation, and the mixer 3
The frequencies of the oscillation signals and 5 are shifted. Note that the direction of increase/decrease in this shift and the amount of shift are determined so that the frequency of the received signal f _i does not change. Also, for the sake of explanation, if the deviation is in the frequency increasing direction, VCO17
The frequency of the oscillation signal increases as the control signal level increases. In addition, the analog-to-digital converter 23
converts the amount of increase in the control signal level into a digital amount and sends it to the digital adder 25. Therefore, the program information sent from the digital adder 25 to the programmable counter 14 of the PLL circuit 8 includes the increase in the control signal level formed by the width variable resistor 21, and is injected into the mixer 3. The frequency of the oscillation signal increases compared to the normal case. Therefore, the frequency that passes through the bandpass filter 4 is shifted from that in the normal case. In addition, since the oscillation signal of the mixer 5 is also shifted from the normal case, the shift of both cancels out and returns to the normal frequency, so apparently the carrier frequency does not change and the passband of the bandpass filter 4 shifts. It turns out. Therefore, since the frequency width passing through the bandpass filter 6 changes by the amount of the movement described above, the width function can be obtained by operating in a direction narrower than in the normal case. Furthermore, when the shift variable resistor 22 is operated, the frequency of the oscillation signal by the VCO 18 is shifted. At the same time, the analog-to-digital converter 24 converts the increase in the control signal level caused by the variable shift resistor 22 into a digital amount, and sends it to the digital adder 25 via the data bus 24a. The digital adder 25 adds the program information formed by the pulse integration counter 15, the increase due to the width variable resistor 21, and the increase due to the shift variable resistor 22, and sends the result to the programmable counter 14. Therefore, the frequency of the oscillation signal injected into the mixer 3 corresponds to the frequency adjustment dial 20, the width variable resistor 21, and the shift variable resistor 22. In this case, the frequency of the oscillation signal injected into the mixer 5 remains shifted by the operation of the width variable resistor 21, so the frequency widths of the bandpass filter 4, mixer 5, and bandpass filter 6 change. Otherwise, the operation is the same as when bandpass filter 4 is replaced with 6 and mixer 4 is replaced with demodulator 7, resulting in a shift operation.

In the above embodiment, the amounts of change in the width variable resistor 21 and the shift variable resistor 22 are each converted into digital amounts and then added by the digital adder 25, but the amounts of change in both are added as analog amounts, The added analog quantity may be converted into a digital quantity. In this case, the number of analog-to-digital converters can be reduced by one, but an additional analog adder is required.

In the passband adjustment circuit according to the present invention, the first and second local signals related to the first and second frequency conversion means provided before and after the bandpass filter are control information consisting of digital quantities and analog quantities, respectively. When changing the frequency, the control information consisting of the other analog quantity is converted into a digital quantity and added. Therefore, it has the feature that addition of frequencies can be performed by adding digital amounts. Therefore, the number of mixers and the like involved in frequency conversion can be reduced, and the generation of spurious signals caused by the mixers and the like can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional passband adjustment circuit, and FIG. 2 is a block diagram showing an embodiment of the passband adjustment circuit of the present invention. Code in the figure, 2 is RF
unit, 3 and 5 are mixers, 4 and 6 are band pass filters, 7 is a demodulator, 8 is a PLL circuit, 9 is a phase comparator, 10 is a low pass filter, 11 and 1
7 and 18 are VCO, 14 is a programmable counter, 15 is a pulse integration counter, 16 is a pulse generator, 19 is an operation panel, 20 is a frequency adjustment dial, 21 is a variable resistor for width, 22 is a variable resistor for shift, 23, 24 is an analog-to-digital converter, and 25 is a digital adder.

Claims (1)

[Claims] 1 Antenna 1, RF tuner 2, mixer 3, bandpass filter 4, mixer 5, bandpass filter 6, and demodulator 7 are connected in cascade and connected to mixer 3.
The programmable counter 14 of the PLL circuit 8 is connected to the VCO 17 to the mixer 5, and the VCO 1 is connected to the demodulator 7.
In a radio receiver in which a width variable resistor 21 and a shift variable resistor 22 provided on an operation panel 19 are connected to VCO 17 and VCO 18, pulses are generated from a frequency adjustment dial 20 provided on the operation panel 19. The control output from the width variable resistor 21 provided on the operation panel 19 is connected to the VCO 17 and analog-to-digital conversion. The output is supplied to the digital adder 25 via the converter 23 and the database 23a, and the control output of the shift variable resistor 22 provided on the operation panel 19 is controlled by the VCO.
18 to the demodulator 7, and also to the digital adder 25 via the analog-to-digital converter 24 and the data bus 24a.
5 supplies a control output to the programmable counter 14 of the PLL circuit 8 via the database 25a to digitally control the width and shift.