JPH026460B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a circuit that varies the reception bandwidth according to the rate of frequency change during tuning of a wireless communication device or a wireless transceiver.

[Conventional technology]

Today's wireless receivers have become capable of extremely narrow band reception due to the development of various filters, and are not suitable for CW communication.
Frequency within 500Hz is used. In such narrow-bandwidth reception, unless the frequency adjustment is made extremely finely when selecting a channel, the signal may be missed. To prevent this, in actual operation, the reception bandwidth is set wide when selecting a channel, and when the target signal is received, the bandwidth is switched to a narrow one.
It is common practice to reduce noise and protect against interference. This is not a problem in commercial communications where communication is carried out over a long period of time with a specific station, but in amateur radio communications where communication is constantly changing with the other station, the complexity is unbearable.

[Problem to be solved by the invention]

In order to eliminate the complexity at the time of tuning as described above, the present invention aims to provide a wireless communication device that automatically varies the receiving bandwidth according to the rate of frequency change at the time of tuning and facilitates the tuning operation.

[Means to solve the problem]

The circuit that uses an electronic switch to select and operate intermediate frequency circuits with multiple different frequency bandwidths measures clock pulses from a dial, etc. that are input to a CPU-controlled PPL oscillator for a certain period of time. Output terminals corresponding to the number of output terminals are connected to the electronic switches and the corresponding electronic switches are operated to operate one intermediate frequency circuit.

Another method is a circuit that continuously varies the intermediate frequency bandwidth by changing the local oscillation frequency.
This method measures clock pulses input to the CPU for a certain period of time, converts the output according to the number of measurements, and supplies an analog voltage to a voltage controlled oscillator to change the local oscillation frequency and change the intermediate frequency bandwidth. be.

〔Example〕

For example, even if the bandwidth of the intermediate frequency is 500Hz (CW filter) during CW reception, the bandwidth will automatically change to 2.4kHz when you move the tuning dial.
(SSB filter), and if you turn the dial more rapidly, it becomes 5kHz (broadcasting filter), and when you stop the dial, it returns to 500Hz.When selecting a channel, the bandwidth is wide, so it is easy to operate. Therefore, the first claim will be explained with reference to the example of the implementation circuit shown in FIG.

FL ₁ , FL ₂ , and FL ₃ are intermediate frequency stage filters, where FL is for a narrow band, FL ₂ is for an intermediate band, and FL ₃ is for a wide band. D ₁ , D ₂ , D ₃ on the input side, and on the output side
D ₄ , D ₅ , D ₆ are for switching the filter circuit.
This is a switching diode, which is a type of electronic switch, and performs switching operations by applying a reverse bias and cutting off the diode, and then applying a forward bias only to the diode that should be conductive. Normally, forward bias circuit switching is made using a manual switch, but in the circuit of the present invention, a CPU (a type of microcomputer) is used for the frequency setting circuit.
Utilizes the extra capacity of the dial encoder or up-down switch to count the number of clocks per unit time of the pulse clock (hereinafter referred to as CK), and if the number of cycles is below a certain level, output _A1 is active. , A ₂ becomes active when the number of cycles increases to a certain extent, and A ₃ becomes active when the number of cycles exceeds a certain level, and the input and output diodes D ₁ and D ₄ of the narrow band filter FL ₁ are controlled by the output of A ₁ . The _A2 output controls the input and output diodes _D2 and _D5 of the intermediate band filter _FL2 , and the _A3 output controls the input and output diodes _{D3 and D6} of the wide band filter FL3. Therefore, since CK is zero except during frequency adjustment, output A ₁ is active, and diodes D ₁ and D ₄ in contact with it are active.
conducts and the narrowband filter FL ₁ enters the circuit. Next, in order to change the frequency, CK is input, so the output A ₂ becomes active, and the diodes D ₂ and D ₅ connected to it become conductive, and the intermediate band filter enters the circuit, changing from the narrow band to the intermediate band. Change. When the frequency changes further and the CK cycle exceeds a certain level, the output A ₃ becomes active, and the diodes D ₃ and D ₆ connected to it become conductive, and a broadband filter enters the circuit, resulting in a broadband state. In this way, switching the intermediate frequency filter is
Since it depends on the CK cycle, if the cycle slows down or stops, the filter automatically returns from wideband to narrowband, and automatically changes the receiving bandwidth according to the change in frequency adjustment speed. .

Next, regarding patent claim 2, the intermediate frequency stage is equipped with a PLL-configured local oscillator for tuning the oscillation frequency, which changes the passband width by changing the local oscillation frequency of the frequency conversion stage. This is performed using the controlled CPU output, and an example of the implementation circuit shown in FIG. 2 will be explained. In the configuration of this intermediate frequency stage, the input frequency is frequency-converted by the first mixer _M1 , passed through the filter _FL4 , and then converted by the second filter _M2 and supplied to the filter _FL5 . ₁ and the second mixer _M2 are supplied with the same frequency from a common local oscillator LO.
The input side frequency of the mixer _M1 and the output side frequency of the second mixer _M2 are exactly the same, and the frequency between the first mixer _M1 and the second mixer _M2 can be changed by the frequency of the local oscillator LO. , filter FL ₄
If you want to shift the frequency of the passing signal upwards or downwards with respect to the center frequency of LO, you can achieve your goal by moving the frequency of the local oscillator LO upwards or downwards. Now, if we use filters with approximately the same bandwidth for filter FL ₄ and filter FL ₅ , and adjust the local oscillator LO so that the passing signal passes through the center, the total bandwidth will be approximately the same as filters FL ₄ and FL ₅ . However, when the local oscillator LO is moved, the filter
This is equivalent to shifting the center frequencies of FL ₄ and filter FL ₅ , and the overlapping frequencies of both filters are passed through, but the others are cut out, so the more the center frequencies shift, the less overlap there is, and the overall bandwidth is It gets narrower. Therefore, this circuit allows the bandwidth to be varied either continuously or in steps simply by changing the frequency of the local oscillator LO, and is currently in use in many devices.

The local oscillator LO needs to have a sufficiently stable oscillation frequency, and a maximum variable frequency range of 5 kHz is sufficient, so the local oscillator LO is a crystal oscillator, and the voltage is inserted in series or parallel with the crystal blank Y. This is often done by adjusting the reverse bias voltage applied to the control capacitance diode CD. In Figure 2, in order to obtain the bias voltage to be applied to this voltage-controlled capacitance diode CD, the CK from the dial encoder or up-down switch is applied to the CPU.
Count the number of clocks per unit time and write the number of cycles in BCD or binary A ₁ to _{A 4}
This is output to an analog control voltage through a D/A converter, and a voltage control capacitance diode is output.
By adding it to CD, a control voltage that is proportional (or inversely proportional) to the cycle of CK is given to the voltage-controlled capacitance diode CD, thereby achieving the objective of the present invention to automatically widen the receiving bandwidth in response to the rate of frequency change. It is something that can be achieved.

Of course, it is necessary to set the frequency of the local oscillator LO so that the total bandwidth becomes the desired narrowest band when the control voltage from the D/A converter is zero. Since it is not limited, it is omitted from the figure.

〔Effect of the invention〕

According to this invention, by automatically changing the receiving bandwidth according to the rate of frequency change when selecting a wireless communication device, tuning operations can be made easier, and in particular, it is possible to eliminate the need to perform frequent tuning operations. It has great practical effects for certain amateur radio applications.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a receiving system showing one embodiment of the invention, and FIG. 2 is a circuit diagram of a receiving system showing another embodiment of the invention. FL ₁ , FL ₂ , FL ₃ , FL ₄ , FL ₅ ... Intermediate frequency filter, CPU ... Microcomputer, D ₁ , D ₂ ,
D ₃ , D ₄ , D ₅ , D ₆ ... Diode for switch, CD
...Voltage controlled capacitance diode, LO...Local oscillator, _M1 , _M2 ...Mixer, Y...Oscillating crystal piece.

Claims (1)

[Claims] 1 Intermediate frequency bandwidth variable means that can vary multiple reception bandwidths of the intermediate frequency stage by local oscillation frequency; In a receiver having an arithmetic processing means for inputting to INT (interrupt) or TI (timer interrupt) and performing calculations necessary for setting the frequency of a local oscillation circuit under PLL control, the clock frequency per unit time of the microcomputer is A reception method characterized in that the reception bandwidth is changed by performing a process of counting the number of inputs together with the arithmetic processing means and controlling a local oscillation frequency with an output voltage corresponding to the cycle.