JPH0773231B2 - All duplex wireless transmission / reception method - Google Patents

Description

The present invention relates to a method of transmitting and receiving by a full-duplex system in the field of mobile radio, and an improvement of transmission spurious characteristics.
The purpose is to simplify the modulation circuit and to make the intermediate frequency selectable.

"Prior Art" A conventional full-duplex radio transceiver is a mixer in which the crystal oscillator 21 of the transmission stage Tx is modulated to produce the first intermediate frequency of the superheterodyne reception stage Rx in FIG.
The output frequency of the voltage-controlled oscillator 22 that also functions as the local oscillator of 202 is mixed with the oscillation frequency of the crystal oscillator 21 by the mixer 201 to generate the transmission frequency. Therefore, a spurious characteristic is bad because a mixer is inserted in the transmission stage, and a narrow band filter can be used as a means for remedying this, but it is economically expensive to prepare a filter having good characteristics. It has a built-in drawback such as being stuck.

Therefore, in order to compensate the above-mentioned drawback, as shown in FIG. 3, a mixer that deteriorates spurious characteristics is eliminated from the transmission stage Tx,
Since the voltage controlled oscillator 32 and the crystal oscillator 31 are modulated by the frequency of the voice band and only filtered by the filter 311 via the amplifier 310, only a limited high frequency component appears and the spurious characteristic is improved. It
However, the transmission frequency, that is, the output frequency of the voltage controlled oscillator is used as the first local oscillator frequency of the superheterodyne receiving stage for the first mixer 301, and from the crystal oscillator 31 for the second local oscillator frequency after reception as the second local oscillator frequency to the second mixer 302. Since the same modulation as the transmission frequency is added to the receiving stage, the crystal oscillation frequency is demodulated by adding it to the receiving stage second mixer as the second local oscillation frequency of the receiving stage in order to cancel this. . However, the first intermediate filter at the receiving stage
Since the crystal oscillator 31 is modulated with the characteristics including the phase characteristics of 313, the modulation circuit itself becomes complicated, and there is no freedom to select the first intermediate frequency. Therefore, the first intermediate frequency can be freely selected. And it is also vulnerable to interference with other radios from the same system. That is, when the transmission frequencies of both the parent device and the child device are received at the same time, interference often occurs because the difference between the two radio waves is equivalent to the first intermediate intermediate frequency.

"Problem to be Solved by the Invention" Therefore, in the conventional full-duplex transmission / reception method, the present invention eliminates the frequency mixing action from the transmission stage that causes deterioration of spurious characteristics, and selects the first intermediate frequency of the superheterodyne reception stage. In order to improve the degree and prevent the crystal oscillator and the modulation circuit of the voltage controlled oscillator from becoming complicated,
(EN) A transmission / reception method in which transmission / reception frequencies are organized so as to release the above-mentioned modulation by the first and second mixers provided in the reception stage. The duplex wireless transmission / reception method of the present invention will be described below with reference to the drawings.

[Embodiment] FIG. 1 is a circuit configuration diagram of an all-duplex type wireless handset for explaining the method of the present invention, and 11 is a crystal oscillator X _1.
1 is a voltage controlled oscillator, 1 is a voltage controlled oscillator, 2 is an amplifier, 3 is an LP filter, and 4 is a duplexer which switches a transmission Tx and a reception Rx in a non-contact manner to form a transmission stage. On the other hand, the receiving stage is a bandpass filter 5, an amplifier 6, a first mixer 7,
The signal is transmitted to the bandpass filter 10 and the second mixer 13. Reference numeral 12 is a second local oscillator that offsets the frequency of the signal passed through the bandpass filter 10 to create a second intermediate frequency.

Both the voltage-controlled oscillator 1 and the crystal oscillator 11 are modulated by the frequency of the voice band and added to the mixer 8 which forms the first local oscillation frequency source of the receiving stage to release the above-mentioned modulation and remove the band pass filter 9. After that, it is offset to the first mixer 7 of the receiving stage.

This will be described below using mathematical expressions.

That is, in FIG. 1, the signal x (t) generated by the voltage controlled oscillator 1 is expressed by the following equation using the voice band signal w _A (t).

x (t) = sin [{w _T + w _A (t)} t] Similarly, the signal y (t) generated by the crystal oscillator 11 is given by the following equation.

y (t) = sin [{w _O + w _A (t)} t] where w _T and w _O are carrier wave components of the voltage controlled oscillator 1 and the crystal oscillator 11.

When the x (t) and y (t) is input to the mixer 8, z (t) = x (t) · y (t) = (1/2) [- cos {(w T + w O + 2w A (t)) t} + cos {(w T -w O) t}] becomes the signal z (t) is obtained as the output of the mixer 8.

Since the first term of z (t) is cut by the BP filter 9,
The following equation is obtained as the local oscillation signal z '(t) of the receiving system.

z ′ (t) = (1/2) cos {(w _T −w _O ) t} As can be seen from the above equation, in this method, the outputs of the voltage controlled oscillator and the crystal oscillator do not need to pass through another filter or the like. , The direct modulation results in the demodulated signal.

Thus, the transmission output frequency propagated from the transmitting stage through the antenna maintains the difference between the input frequency, which is the incoming radio wave captured by the antenna, and the first intermediate frequency of the receiving stage, that is, the difference, so that simultaneous communication is possible on any channel. it can.

[Effect] Thus, the present invention has a voltage-controlled oscillation frequency that is modulated without providing a mixer at the transmission stage even if a large number of stations start communicating at the same frequency band, for example, between a base station and a mobile station all at once. Since it is used directly as the transmission frequency, it has excellent transmission spurious characteristics.In order to prevent the occurrence of phase shift, the oscillation frequency of the crystal oscillator and the output frequency of the voltage controlled oscillator should be passed through a filter that generates the phase shift. Instead of mixing directly in the mixer and using the output as the local oscillation frequency to obtain the first intermediate frequency of the heterodyne receiving stage, there is no phase shift in the mixer, so the phase characteristics are superior to the conventional technology and Not only does the use of a filter with a large frequency selectivity and a shield that has been conventionally required to prevent interference due to frequency, but also a modulation circuit It is not complicated, and moreover, by changing the frequency of the crystal oscillator 11, the degree of freedom in arbitrarily changing and selecting the first intermediate frequency is increased, and the difference between the transmission and reception frequencies does not become almost the first intermediate frequency, which is different from the conventional one. The occurrence of interference is almost eliminated, and it has a very practical and beneficial effect.

Therefore, the present invention can be applied to all duplex type wireless handsets to exert excellent effects.

[Brief description of drawings]

FIG. 1 is a circuit block diagram of a duplex transmission / reception unit in which the method of the present invention is implemented, and FIGS. 2 and 3 are explanatory views of a conventional example in which the duplex transmission / reception method is implemented by different circuit configurations. . 1 ... Voltage controlled oscillator, 2,6 ... Amplifier, 3 ... LP filter, 4 ... Duplexer, 5,9,10 ... Band pass filter, 7,8,13 ... Mixer, 11,12 ... Crystal oscillator.

Claims (1)

[Claims] 1. A radio transmitter / receiver which is used as a local oscillation frequency for transforming a voltage controlled oscillation frequency into a transmission frequency and mixing with a crystal oscillation frequency to form a first intermediate frequency of a heterodyne reception system, the radio transceiver comprising: In the all-duplex wireless transmission / reception method of communicating between slave stations, the crystal oscillator and the voltage-controlled oscillator are individually modulated by the voice band frequency, and the output frequency of the voltage-controlled oscillator is used as the transmission frequency, and the occurrence of phase shift is prevented. In order to achieve this, the oscillating frequency of the crystal oscillator and the output frequency of the voltage controlled oscillator are directly mixed by a mixer and used as the first intermediate frequency of the heterodyne receiving stage.