JPH05152988A - Double superheterodyne radio equipment - Google Patents

Abstract

PURPOSE:To reduce an inter-code interference caused by a shift of the center frequency of a band pass filter. CONSTITUTION:An AFC circuit 1 executes the following operations after 32 executes synchronization of a transmitting frequency fTX to a receiving frequency fRX. To a ROM 11, a shift from a center frequency at each temperature of a BPF 30 is set together with that which is caused by a manufacturing error. A temperature sensor 12 allows the ROM 11 to output a deviation value at a detected temperature. An adding circuit 10 adds a count value of a counter 52 and an output value of the ROM 11. A large/small relation of its added value and a prescribed value is decided by a magnitude comparator 13, and based on a result of its decision, a prescribed pulse is outputted from a pulse generator 14, the number of its pulses is subjected increase/decrease count by an up/down counter 15, its count value is analogized by a C/A converter 16, and an oscillation frequency of an oscillator 2 is set. The oscillator 2 generates a second local frequency f2LO in a state synchronized with the center frequency of the BPF 30. As a result, the center frequency of the BPF 30 and a second IF frequency f2IF coincide with each other, and an inter-code interference is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double superheterodyne radio having an automatic frequency control circuit for synchronizing a transmission frequency with a reception frequency, and more particularly to a technique for reducing intersymbol interference in a bandpass filter.

[0002]

2. Description of the Related Art As a double superheterodyne radio having an automatic frequency control (hereinafter referred to as "AFC") circuit for synchronizing a transmission frequency with a reception frequency, the one shown in FIG. 2, for example, is conventionally known. In FIG. 2, 21 is an antenna, 22 is a transmission / reception switch, 23 is a transmission mixer, 24 and 25 are synthesizers, 26 is a reference oscillator, 27 is a first mixer, 28 is a second local oscillator, 29 is a second mixer, and 30 is an intermediate frequency. Band (IF) band pass filter (BPF), 31 is a second IF amplifier, 32 is A
It is an FC circuit.

The reference oscillator 26 comprises a crystal oscillator,
Output of AFC circuit 32 (output of D / A converter 57)
A reference signal having a frequency determined by is generated and given to both synthesizers (24, 25). The synthesizer 24 operates as a fast local oscillator, and supplies a fast local signal (frequency f _LO ) to the transmission mixer 23 and the reception-side fast mixer 27. Also, synthesizer 25
Generates a signal of a predetermined frequency and supplies it to the transmission mixer 23. As a result, the transmission mixer 23 transmits the transmission frequency f _TX.
Is formed and is wirelessly transmitted from the antenna 21 via the transmission / reception switch 22.

On the other hand, the signal wirelessly received by the antenna 21 (reception frequency f _RX ) is input to the fast mixer 27 via the transmission / reception switch 22, where the fast IF signal f _{1IF is fed} by the fast local signal of the frequency f _LO. Signal is frequency-converted to a second mixer 29, and is further frequency-converted by the second local signal (frequency f _2LO ) given from the second local oscillator 28, filtered by the BPF 30, and amplified by the second IF amplifier 31. And becomes a signal of the second IF frequency f _2IF . Here, the second local oscillator 28 has a predetermined frequency f _2LO defined as the second local oscillation frequency.
The second local signal is generated and is supplied to the counter 52 of the AFC circuit 32 in addition to the second mixer 29. Also, the signal of the second IF frequency f _2IF is A
It is given to the counter 51 of the FC circuit 32.

Now, the AFC circuit 32 has the above-mentioned counter 5
1 and 52, an addition circuit 53, a magnitude comparator 54, a pulse generator 55, an up / down counter 56 and a D / A converter 57 are provided, and operate so that the transmission frequency f _TX is synchronized with the reception frequency f _RX. ..

Namely, the counter 51 counts the second IF frequency f _2IF, also the counter 52 counts the second local frequency f _2LO, two count values are added by the adding circuit 53, is greater than the prescribed value and the added value Whether or not it is determined by the magnitude comparator 54, a predetermined pulse is output from the pulse generator 55 based on the determination result, the number of pulses is increased / decreased by the up / down counter 56, and the count value is D / A.
It is converted into an analog signal by the converter 57, whereby the oscillation frequency of the reference oscillator 26, that is, the first local oscillation frequency f _{LO of the} synthesizer 24 is set.

[0007] In summary, the AFC circuit 32, (the output of the reference oscillator 26) the reference frequency of the synthesizer 24 as the sum of the second IF frequency f _2IF and second local frequency f _2LO becomes a predetermined value by varying the, first The local oscillation frequency f _LO and the reception frequency f _RX and the fast I
The transmission frequency f _TX is synchronized with the reception frequency f _RX by matching the difference frequency with the F frequency f _1IF .

[0008]

In the above-mentioned conventional radio equipment, the second local oscillator is adjusted and set so as to oscillate at a frequency determined as the second local signal, and B
The AFC circuit is provided on the assumption that the center frequency of the PF and the second IF frequency f _2IF match. However, if there is an error in the oscillation frequency of the second local oscillator, it will add to the second IF frequency f _2IF . Also, BPF
Also, there is an error in the center frequency due to the influence of manufacturing error and temperature. Therefore, in many cases, the center frequency of the BPF and the second IF frequency do not actually match. As a result, in data transmission, there is a problem that intersymbol interference in the BPF increases, which increases fixed deterioration and deteriorates the bit error rate at a predetermined C / N value.

An object of the present invention is to provide a double superheterodyne radio equipped with means for reducing deterioration due to intersymbol interference in BPF.

[0010]

In order to achieve the above-mentioned object, the table super-heterodyne radio set according to the present invention has the following configuration. That is, the tableable super-heterodyne radio device of the first invention comprises a fast mixer that frequency-converts a received signal received by an antenna with a fast local signal and outputs a fast IF signal, and an output of this fast mixer as a second local signal. A second mixer for performing frequency conversion by means of frequency conversion, a band-pass filter for filtering the output of the second mixer, and an amplifier for amplifying the output of the band-pass filter and outputting a second IF signal; A reference oscillator that generates a reference signal of a predetermined frequency according to a setting signal, a fast local oscillator that generates the first local signal based on the output of the reference oscillator, and a transmission signal of a predetermined frequency that is based on the output of the reference oscillator The frequency is converted to a signal with a predetermined transmission frequency by the first local signal, and A transmission system including a transmission mixer for outputting to an antenna; the second I
The frequency of the first local signal is the difference between the reception frequency and the first IF frequency by generating the setting signal having a value according to the magnitude relationship between the sum of the frequency of the F signal and the frequency of the second local signal and the specified value. A first automatic frequency control (AFC) circuit for changing the transmission frequency to match the reception frequency and synchronizing the transmission frequency with the reception frequency; and; in a double superheterodyne radio device; generating center frequency information of the band-pass filter. Means for controlling the frequency of the second local signal in accordance with the magnitude relationship between the sum of the frequency of the second local signal and the center frequency information and a specified value, and filtering the frequency of the second local signal by the band-pass filtering. A second AFC circuit for synchronizing with the center frequency of the container.

The table super-heterodyne radio of the second invention is the double super-heterodyne radio of the first invention; the means for generating the center frequency information comprises a setting device for setting the center frequency information. It is a feature.

[0012] The tableable super-heterodyne radio of the third invention is the double super-heterodyne radio of the first invention; the means for generating the center frequency information is a temperature sensor; And a memory for outputting center frequency information according to the output of the sensor.

[0013]

Next, the operation of the table super-heterodyne radio apparatus of the present invention constructed as described above will be described. In the present invention, the second AFC circuit controls the frequency of the second local signal according to the center frequency information of the band pass filter, synchronizes the frequency of the second local signal with the center frequency of the band pass filter, and passes the band pass filter. Match the center frequency of the wave filter with the second IF frequency. Therefore, even if the center frequency of the bandpass filter has a deviation due to a manufacturing error or a temperature change, it can be corrected, so that it is possible to reduce the intersymbol interference due to the deviation of the center frequency of the bandpass filter. It is possible to provide a portable super heterodyne radio device.

The center frequency information of the band-pass filter may be either a deviation value due to manufacturing error or temperature, or a center frequency including the deviation value. Regarding the generation of the center frequency information, May detect the deviation from the theoretical center frequency by, for example, monitoring the output of the bandpass filter, but when the manufacturing error is the main factor, the setting is made in a setting device such as a switch or a memory (second (Invention), or when the temperature change is the main, the center frequency information (including the deviation value according to the manufacturing error if necessary) corresponding to the temperature is set in the memory, and the memory content is taken out by the output of the temperature sensor. (Third invention) This is practical.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a tabletop superheterodyne radio according to an embodiment of the present invention. The same components as those of the conventional apparatus of FIG. 2 are designated by the same reference numerals. In the present invention, a (second) AFC circuit 1 is provided in addition to the conventional (first) AFC circuit 32. The AFC circuit 1 includes a second local oscillator 2 so that the second local oscillator 2 generates a second local frequency f _2LO defined as an oscillation frequency in synchronization with the center frequency of the BPF 30.
To control. In this respect, the conventional second local oscillator 2
8 is simply set to generate the frequency f _2LO .

The AFC circuit 1 shares the counter 52,
An adder circuit 10, a ROM 11, a temperature sensor 12, a magnitude comparator 13, a pulse generator 14, an up / down counter 15, and a D / A converter 16 are provided.

In the ROM 11, center frequency information at each temperature of the BPF 30, for example, a deviation from the center frequency is set together with information due to a manufacturing error. The temperature sensor 12 detects the temperature of the device and outputs the deviation value at that temperature to the ROM 11.

The adder circuit 10 adds the count value of the counter 52 and the output value of the ROM 11. The magnitude comparator 13 determines the magnitude relationship between the added value and the specified value, and based on the determination result, the pulse generator 1
4 outputs a predetermined pulse, the up / down counter 15 increases or decreases the number of pulses, and the D / A converter 16 analogizes the count value, whereby the oscillation frequency of the second local oscillator 2 is set. It That is, the second local oscillator 2 has the BPF3
The second local frequency f _2LO is generated in synchronization with the center frequency of 0. As a result, match the center frequency and the second IF frequency f _2IF the BPF 30, the intersymbol interference is reduced.

The synchronization operation of the AFC circuit 1 described above is performed after the first local frequency f _LO is synchronized with the reception frequency f _RX by the AFC circuit 32 described above. Even if the synchronization operation is performed, the synchronization state realized by the AFC circuit 32 is maintained as it is.

When the center frequency of the BPF 30 at each temperature is set in the ROM 11, the AFC loop may be constructed so that the content of the counter 51 matches the content of the ROM 11.

[0021]

As described above, according to the table super-heterodyne radio of the present invention, the frequency of the second local signal is controlled by the center frequency information of the bandpass filter, and the frequency of the second local signal is bandpassed. Since the second AFC circuit that synchronizes with the center frequency of the filter is provided so that the center frequency of the bandpass filter matches the second IF frequency, the center frequency of the bandpass filter has a manufacturing error or Even if there is a shift due to temperature change, it can be corrected. Therefore, there is an effect that intersymbol interference due to the shift of the center frequency of the bandpass filter can be reduced and a practical double superheterodyne radio can be provided.

[Brief description of drawings]

FIG. 1 is a configuration block diagram of a tablet super-heterodyne wireless device according to an embodiment of the present invention.

FIG. 2 is a configuration block diagram of a conventional tableable super-heterodyne radio device.

[Explanation of symbols]

 1 AFC Circuit 2 Second Local Oscillator 10 Addition Circuit 11 ROM 12 Temperature Sensor 13 Magnitude Comparator 14 Pulse Generator 15 Up / Down Counter 16 D / A Converter 32 AFC Circuit 52 Counter

Claims (3)

[Claims] 1. A first mixer that frequency-converts a reception signal received by an antenna with a first local signal to output a first IF signal, and a second mixer that frequency-converts an output of this first mixer with a second local signal. A receiving system including a bandpass filter for filtering the output of the second mixer and an amplifier for amplifying the output of the bandpass filter and outputting a second IF signal; A reference oscillator that generates a reference signal, a fast local oscillator that generates the fast local signal based on the output of the reference oscillator, and a transmission signal of a predetermined frequency that is based on the output of the reference oscillator, is a predetermined transmission frequency of the first local signal. And a transmission mixer that converts the frequency of the signal into a signal and outputs the signal to the antenna. A communication system; the setting signal having a value corresponding to a magnitude relation between a sum of the frequency of the second IF signal and the frequency of the second local signal and a prescribed value is generated, and the frequency of the first local signal is the reception frequency and the frequency of the reception signal. A first automatic frequency control (AFC) circuit that is variable so as to match the frequency of the difference from the first IF frequency and that synchronizes the transmission frequency with the reception frequency; and a double superheterodyne radio device comprising: the bandpass filter Of the second local signal, the frequency of the second local signal is controlled according to the magnitude relationship between the sum of the frequency of the second local signal and the center frequency information and a specified value. A second A for synchronizing the center frequency of the bandpass filter with
A double super-heterodyne radio having an FC circuit; 2. The double super-heterodyne radio device according to claim 1, wherein said means for generating center frequency information comprises a setter for setting center frequency information;
A double superheterodyne radio characterized by this. 3. The double super-heterodyne wireless device according to claim 1, wherein the means for generating the center frequency information is a temperature sensor; and the center frequency information is set, and the center frequency information according to the output of the temperature sensor is set. A double super-heterodyne wireless device comprising: a memory for outputting.