JPH04281636A - Transmitter-receiver - Google Patents

Abstract

PURPOSE:To prevent the deterioration in the reception characteristic due to a leakage signal from a transmission circuit in the TDD system transmitter- receiver. CONSTITUTION:A transmission circuit 10 of the TDD system transmitter-receiver is provided with a modulation circuit 12 converting a sent digital sound signal Sa into a modulated signal Sf, a 1st mixer circuit 13 frequency-converting the modulated signal Sf into a 1st intermediate frequency signal Sit, and a 2nd mixer circuit 15 frequency-converting the 1st intermediate frequency signal Sit into a prescribed channel of transmission signal St to configurate the system in a double superheterodyne system. The generation of a 1st local oscillation signal Sk is allowed only for a period of a transmission slot.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a TDD type transmitter/receiver.

0002

2. Description of the Related Art Digital mobile telephones such as telepoint systems generally use the TDD system or TDMA/TDD system, which uses the same frequency for transmission and reception, and performs so-called ping-pong transmission.

That is, in the case of the TDD method, for example, as shown in FIG.
As shown in , one channel (frequency) is temporally divided into a transmission slot T and a reception slot R, and these slots T and R are alternately repeated, and between these slots T and R, Guard band time Tg
will be provided. As an example, the transmission slot T and the reception slot R are 1 msec, and the guard band time Tg is several tens of microseconds. Then, the mobile phone transmits to the base station in the transmission slot T, and receives from the base station in the reception slot R.

[0004] Since such transmission and reception are performed, T
A transmitting circuit and a receiving circuit of a DD type transmitting/receiving device are configured as shown in FIG. 4, for example.

That is, in the figure, 10 is a transmitting circuit, 20 is a receiving circuit, and 31 is a system controller. The system controller 31 controls the overall operation of this transmitting/receiving device, and is composed of a microcomputer. Further, the system controller 31 also forms various timing signals and clocks, and the signals from the system controller 31 are supplied to respective circuits, although not shown.

[0006] Then, in the transmitting circuit 10, the audio signal Sa is supplied to the transmitting processing circuit 11, where processing for transmission such as A/D conversion, time axis compression, and addition of control data from the system controller 31 is performed. The processed digital audio signal Sa is extracted for each transmission slot T, and this signal Sa is supplied as a modulation signal to the modulation circuit 12. From the modulation circuit 12, the digital audio signal Sa is subjected to FSK modulation, for example, for each transmission slot T. modulated signal S
it (carrier frequency fi is, for example, 80 MHz) is extracted.

[0007] Then, this signal Sit is sent to the mixer circuit 15.
At the same time, a local oscillation signal Sc of frequency fc is taken out from the synthesizer oscillation circuit 33 for setting transmission and reception channels, and this signal Sc is supplied to the mixer circuit 15.
and the signal Sit is a transmission signal St of frequency fs
The frequency is converted to Note that in this frequency conversion, fs = fi + fc, for example, fc = 2.6 GHz. Further, the frequency fc, that is, the channel, is set by the synthesizer oscillation circuit 33 being controlled by the system controller 31.

The transmission signal St is then supplied to the antenna 35 through the signal line of the bandpass filter 16 → power amplifier 17 → high frequency switch circuit 34.
transmitted to the base station.

At this time, the switch circuit 34 is switched between the transmission slot T and the reception slot R by a control signal from the system controller 31, and the antenna 35 is switched between the transmission circuit 10 and the reception circuit 20.

[0010] Then, in the receiving circuit 20, the transmission signal Sr (
The frequency fs) is received by the antenna 35, and this signal Sr is supplied to the first mixer circuit 23 through the signal line of the switch circuit 34 → band pass filter 21 → high frequency amplifier 22, and the signal Sr from the oscillation circuit 33 The oscillation signal Sc is supplied to the first mixer circuit 23, and the signal Sr is frequency-converted into a first intermediate frequency signal Sir. Note that in this case, the intermediate frequency of the signal Sir is equal to the signal S
It is equal to the frequency fi of it.

Then, this signal Sir is supplied to the second mixer circuit 25 through the first intermediate frequency filter 24, and the second local oscillation signal Sj is supplied from the second local oscillation circuit 26 to the mixer circuit 25 to generate the signal. Sir is the second
Intermediate frequency signal Sjr (intermediate frequency is, for example, 450 kHz)
z), and this signal Sjr is supplied to the demodulation circuit 28 through the second intermediate frequency filter 27 to demodulate the digital audio signal Sb for each reception slot R, and this signal Sb is supplied to the reception processing circuit 29. Processing for reception is performed and the original audio signal Sb is extracted. Control data is also taken out from the processing circuit 29 and supplied to the system controller 31.

According to this TDD system, the transmitting signal St and the receiving signal Sr both have the same frequency fs, so that the base station can perform uplink and downlink diversity communication simply by performing antenna diversity. can be realized. Furthermore, frequencies can be allocated continuously to uplink channels and downlink channels without dividing the frequency bands, resulting in good frequency usage efficiency.

[0013]

By the way, in the transmitting/receiving apparatus as described above, the period of the receiving slot R, as shown in FIG.
As shown by a broken line 41 in FIG.
The signal leaks to the intermediate frequency filter 24 through the line and interferes with the intermediate frequency signal Sir.

Furthermore, the period of the reception slot R is indicated by a broken line 42.
As shown in , the modulated signal Sit from the modulation circuit 12 is frequency-converted in the mixer circuit 15 into a signal with a frequency fs equal to the original transmission signal St, and then the signal line from the filter 16 to the amplifier 17 to the switch circuit 34 is converted. leaks to the filter 21 through the receiving circuit 20.
The actual reception sensitivity of the signal will decrease.

Therefore, in order to eliminate such reception interference, (1) during the reception slot R, the power to the modulation circuit 12 is turned off so that no carrier signal is formed in the modulation circuit 12;

(2) The oscillation frequency fc of the synthesizer oscillation circuit 33 in the transmission slot T and the reception slot R
Even if the carrier signal Si leaks to the receiving circuit 20 as shown by the broken line 41, the intermediate frequency filters 24 and 27
so that it is removed.

(3) During the reception slot R, the unmodulated carrier signal Sit is cut off in the mixer circuit 15 by turning off the power to the mixer circuit 15. Possible methods include:

However, in the method (1), it is necessary to start the oscillation of the modulation circuit 12 during the guard band time Tg, that is, a period of several tens of microseconds, but since the modulation circuit 12 has a high carrier frequency fi, Such a start-up is impossible, and it becomes impossible to obtain a normal local oscillator signal Sc during the transmission slot T period.

Furthermore, in the method (2), the frequency fc of the oscillation circuit 33 must be changed during the guard band time Tg, but the carrier frequency fc
Since it is a quasi-microwave, such a change is impossible, and it becomes impossible to obtain a normal local oscillation signal Sc. Furthermore, in this method, the transmission channel and the reception channel are different.

Furthermore, in the method (3), it is necessary to maintain an isolation of about 110 to 120 dB, but such a large isolation varies depending on the shielding effect, the configuration and pattern of the printed wiring board, etc. Easy and unreliable. Further, even if isolation is achieved against the leakage signal shown by the broken line 41, it is quite difficult to provide isolation against the leakage signal shown by the broken line 42 in the switch circuit 34 because the frequency fs of the transmission signal St is in the quasi-microwave band. It is. This invention attempts to solve the above problems.

[0021]

[Means for Solving the Problems] Therefore, in the present invention, one channel is time-divided into a transmission slot T and a reception slot R, if the reference numerals of each part correspond to the embodiments described below. Transmission slot T and reception slot R
In a transmitting/receiving device that performs transmission and reception in a time-division manner, the transmitted digital audio signal Sa is converted into a modulated signal S.
a first mixer circuit 13 that converts the frequency of the modulated signal Sf into a first intermediate frequency signal Sit, and a first mixer circuit 13 that converts the frequency of the first intermediate frequency signal Sit into a transmission signal St of a predetermined channel. 2 mixer circuit 15, the first mixer circuit 13, a forming circuit 18 that forms a first local oscillation signal Sk for frequency conversion, and a forming circuit 18 that controls the formation of the first local oscillation signal Sk in this forming circuit 18. A control circuit 31 is provided, and the control circuit 31 allows the formation circuit 18 to form the first local oscillation signal Sk 2 only during the transmission slot T.

[0022]

[Operation] During the period of the transmission slot T, the digital audio signal is converted into the transmission signal St of a predetermined channel by the double superheterodyne method and is transmitted. However, during the period of the reception slot R, the formation of the first local oscillation signal Sk in the transmission circuit 10 is prohibited, and therefore, unnecessary signals are prevented from leaking to the reception circuit 20 or the outside during the period of the reception slot R. Ru.

[0023]

[Embodiment] In FIG. 1, a transmitting circuit 10 is of a double superheterodyne type, and a modulating circuit 12,
A first mixer circuit 13 and a bandpass filter 14 are provided on the signal line between the mixer circuit 15 and a forming circuit 18 as a first local oscillation circuit.

Specific examples of the forming circuit 18 and mixer circuit 15 will be described later, but the forming circuit 18 is connected to the system controller 3.
1, the first local oscillation signal Sk is controlled by the control signal Ss from 1, and the first local oscillation signal Sk is generated and output only during the period of the transmission slot T (and the guard band time Tg immediately before it). Then, this local oscillation signal Sk is sent to the mixer circuit 13
is supplied to

In this case, Sf: output signal (FSK signal) of the modulation circuit 12 ff
: Carrier frequency fk of signal Sf : Frequency of local oscillation signal Sk, fit=ff + fk, and frequency fk is fk
>BW/2 to BW BW: Channel band of transmitted and received signals St and Sr. For example, at 4MHz fk, image suppression is easy in the filter 14;
In addition, the ON/OFF state of the signal Sk is set to a value that is easily satisfied.

Furthermore, the control signal Ss from the system controller 31
is supplied to the mixer circuit 13, and the mixer circuit 13 receives the transmission slot T (and the immediately preceding guard band time Tg).
), the operating voltage is supplied only during the period.

In reality, there is a slight time difference between the control signal Ss supplied to the forming circuit 18 and the control signal Ss supplied to the mixer circuit 13 due to the group delay characteristics of the main signal line. Although a phase difference is required, it is not relevant to the essence of the invention, so in this example, both control signals Ss and Ss are assumed to be equal. Further, the mixer circuit 15 is a second mixer circuit.

According to such a configuration, the transmission slot T
During the period, the operating voltage is supplied to the mixer circuit 13 by the control signal Ss, so the mixer circuit 13 can perform its original operation.

Also, during the transmission slot T, a local oscillator signal Sk is formed in the forming circuit 18 by the control signal Ss, and this signal Sk is supplied to the mixer circuit 13.

Therefore, during the transmission slot T,
The digital audio signal Sa from the transmission processing circuit 11 is converted into an FSK signal Sf (carrier frequency f
f), and this FSK signal Sf is frequency-converted into an intermediate frequency signal Sit by the local oscillation signal Sk in the first mixer circuit 13. This intermediate frequency signal Sit is then supplied to the second mixer circuit 15 after unnecessary signal components are removed by the bandpass filter 14.
The frequency is converted into a transmission signal St and transmitted from the antenna 35.

On the other hand, during the reception slot R, the reception circuit 20 performs the reception operation as described above.

Furthermore, during the reception slot R, the operating voltage of the mixer circuit 13 is cut off by the control signal Ss, so the mixer circuit 13 stops its original operation.

Furthermore, during the reception slot R, the formation of the local oscillator signal Sk in the formation circuit 18 is stopped by the control signal Ss, and the signal Sk is no longer supplied to the mixer circuit 13.

Therefore, during the reception slot R,
The mixer circuit 13 does not operate, and the local oscillator signal Sk
Since the signal Sit itself is not supplied, the signal Sit itself is not formed. Therefore, during the reception slot R, as shown by broken lines 41 and 42 in FIG.
There is no leakage to the receiving circuit 20, and no reception disturbances such as interference or reduction in reception sensitivity occur.

Thus, according to the present invention, the transmitting circuit 1
0 is configured to be double superheterodyne, and during the period of the reception slot R, the operation of the first mixer circuit 13 is prohibited and the first local oscillation signal Sk is not supplied, so that the signal Sit itself is not formed. No reception interference occurs in the reception circuit 20.

[0036] Also, during the reception slot R, the transmission signal S
t will not be radiated to the outside from the antenna 35 and cause interference to other systems. Further, even if the local oscillator signal Sk leaks through the mixer circuit 13 with the frequency fk, it is sufficiently attenuated by the bandpass filter 14, so that it does not cause reception interference.

Furthermore, the mixer circuit 13 is intermittently supplied with power supply voltage in the transmission slot T and the reception slot R, but since the mixer circuit 13 only mixes the two signals Sf and Sk, the guard band time is The voltage rises sufficiently within Tg, and a sufficiently normal frequency conversion operation can be performed during the transmission slot T.

Further, the forming circuit 18 forms the local oscillator signal Sk only during the transmission slot T, but the local oscillator signal Sk
Since the frequency fk can be made low, the local oscillator signal Sk also rises sufficiently within the guard band time Tg, and the local oscillator signal Sk is sufficiently stable and normal during the transmission slot T.
It can be done.

Furthermore, since the synthesizer oscillation circuit 33 can be used in common for the transmitting circuit 10 and the receiving circuit 20,
Not only can you significantly reduce costs, but you can also downsize and
It can be made lighter. Furthermore, even if the isolation of the switch circuit 34 is low, there is almost no radiation to the outside, so the circuit can be simplified, and from this point of view as well, cost reduction and size reduction can be achieved. Also, it does not interfere with other channels.

[0040]Furthermore, there is no need to divide the frequency band into uplink channels and downlink channels, and frequencies can be allocated continuously. Furthermore, since the transmitted signal St and the received signal Sr have the same frequency, antenna diversity can be achieved only by the base station. That is, T.D.
The features of the D method are not impaired at all.

FIG. 2 shows a specific example of the modulation circuit 12, mixer circuit 13, and formation circuit 18. That is, modulation circuit 1
2, the digital audio signal Sa from the transmission processing circuit 11 is supplied to the modulation degree setting circuit 122 after unnecessary signal components are removed by the filter 121. When the signal Sf is frequency-converted into the signal Sit, the setting circuit 122 sets the signal Sf so that the original modulation degree necessary for the signal Sit is obtained, since the modulation degree changes between the signal Sf and Sit. This is for setting the degree of modulation for.

Then, the digital audio signal Sa from the setting circuit 122 is transmitted to a variable crystal oscillation circuit 123 using a crystal oscillator as an oscillation element, a so-called VCXO 123.
is supplied as a modulation signal to the FSK signal Sf (carrier frequency fs), and this signal Sf is supplied to the base of the transistor 131 after unnecessary signal components are removed in a bandpass filter (tuning circuit) 124. .

This transistor 131 is connected to the mixer circuit 1
3, whose emitter is grounded, and a bandpass filter (tuned circuit) 14 is connected as its collector load, and the filter 14 and power supply line VC
A switch circuit 132 is provided between the system controller 32 and the switch circuit 132, and a control signal Ss from the system controller 32 is supplied to the switch circuit 132.

Furthermore, in the formation circuit 18, a system clock, for example, is taken out from the system controller 31, and this system clock is supplied to a frequency dividing circuit 181 and frequency-divided into a signal Sd of frequency fk, and this frequency-divided signal Sd is At the same time, the control signal Ss from the system controller 31 is supplied to the AND circuit 182. The output signal of this AND circuit 182 is then supplied to the base of the transistor 131 through a low-pass filter 183 and an amplifier 184.

Note that the control signal Ss is transmitted through the transmission slot T
It becomes "1" during the period of (and the immediately preceding guard band time Tg), and becomes "0" during the period of the reception slot R (and the immediately preceding guard band time Tg). Further, the switch circuit 132 is turned on when Ss="1".

According to such a configuration, the transmission slot T
During the period, since Ss = "1", the frequency-divided signal Sd from the frequency divider circuit 181 is supplied to the low-pass filter 183 through the AND circuit 182, and is converted into an alternating signal having only the frequency fk component, that is, a local oscillation signal. Sk is retrieved. Then, this local oscillation signal Sk is transmitted to the amplifier 18
4 to the base of transistor 131.

[0047] Also, during the transmission slot T, Ss
="1", the switch circuit 132 is on, and the transistor 131 operates as the mixer circuit 13.

Therefore, during the transmission slot T,
In the transistor 131, the bandpass filter 12
The signal Sf from the amplifier 184 is the local signal Sf from the amplifier 184.
The signal Sit is frequency-converted by k to a signal Sit having a frequency fit, and this signal Sit is supplied to the second mixer circuit 15 through the bandpass filter 14.

On the other hand, during the reception slot R, Ss
= “0”, the frequency-divided signal Sd is blocked by the AND circuit 182, and the local oscillation signal Sk is blocked by the transistor 131.
is not supplied. Furthermore, since Ss="0", the switch circuit 132 is off and the transistor 131 does not operate. Therefore, during the reception slot R, the mixer circuit 1
3, the signal Sit is never output.

Furthermore, since the AND circuit 182 can respond at a sufficient speed, the AND circuit 182 outputs the divided signal Sd at the guard band time Tg immediately before the period of the transmission slot T.
At the same time, the transistor 13
1 also becomes operational at the guard band time Tg, and therefore, during the transmission slot T, a signal Sit with sufficient characteristics can be obtained.

[0051] Then, when it comes to the period of reception slot R,
Since the AND circuit 182 immediately blocks the frequency-divided signal Sd and the transistor 131 is also turned off, no reception disturbance occurs in the receiving circuit 20.

In the above description, the input signal to the frequency dividing circuit 181 may be the reference signal used in the synthesizer oscillation circuit 33 instead of the system clock from the system controller 31. In addition, the formation circuit 18
It is also possible to obtain the signal Sk during the transmission slot T by providing a ROM in which the waveform of the local oscillator signal Sk is written and controlling its read clock.

Furthermore, the VCXO 123 can be a PLL modulation circuit or a quadrature modulation circuit. Further, the mixer circuit 13 can be a double-balanced mixer circuit or a dual-gate FET, and its specific configuration does not matter. Furthermore, fit=ff −fk
It is also possible to do this.

Alternatively, the switch circuit 132 may be omitted and the collector voltage may always be supplied to the transistor 131.
Bandpass filters 124 to 14 can also be omitted.

[0055]

According to the present invention, the transmitting circuit 10 is configured to be double superheterodyne, and during the reception slot R, the operation of the first mixer circuit 13 is prohibited, and the first local oscillation signal Sk is also supplied. Therefore, the signal Sit itself is not formed, and therefore the receiving circuit 20
There will be no reception interference.

Furthermore, during the reception slot R, the transmission signal S
t will not be radiated to the outside from the antenna 35 and cause interference to other systems. Further, even if the local oscillator signal Sk leaks through the mixer circuit 13 with the frequency fk, it is sufficiently attenuated by the bandpass filter 14, so that it does not cause reception interference.

Furthermore, the mixer circuit 13 is intermittently supplied with power supply voltage in the transmission slot T and the reception slot R, but since the mixer circuit 13 only mixes the two signals Sf and Sk, the guard band time is The voltage rises sufficiently within Tg, and a sufficiently normal frequency conversion operation can be performed during the transmission slot T.

Further, the forming circuit 18 forms the local oscillator signal Sk only during the period of the transmission slot T, but the local oscillator signal Sk
Since the frequency fk can be made low, the local oscillator signal Sk also rises sufficiently within the guard band time Tg, and the local oscillator signal Sk is sufficiently stable and normal during the transmission slot T.
It can be done.

Furthermore, since the synthesizer oscillation circuit 33 can be used in common for the transmitting circuit 10 and the receiving circuit 20,
Not only can you significantly reduce costs, but you can also downsize and
It can be made lighter. Furthermore, even if the isolation of the switch circuit 34 is low, there is almost no radiation to the outside, so the circuit can be simplified, and from this point of view as well, cost reduction and size reduction can be achieved. Also, it does not interfere with other channels.

[0060] Furthermore, there is no need to divide the frequency band into uplink channels and downlink channels, and frequencies can be allocated continuously. Furthermore, since the transmitted signal St and the received signal Sr have the same frequency, antenna diversity can be achieved only by the base station. That is, T.D.
The features of the D method are not impaired at all.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of an example of the present invention.

FIG. 2 is a system diagram showing an example of essential parts of the present invention.

FIG. 3 is a diagram for explaining transmission and reception slots.

FIG. 4 is a system diagram of a conventional example.

[Explanation of symbols]

10 Transmission circuit 12 Modulation circuit 13 First mixer circuit 15 Second mixer circuit 18 Formation circuit 20 Receiving circuit 23 First mixer circuit 24 First intermediate frequency filter 25 Second mixer circuit 27 Second intermediate frequency filter 28 Demodulation circuit 31 System controller 33 Synthesizer oscillation circuit 35 Transmitting/receiving antenna 123 VCXO 181 Frequency divider circuit

Claims (1)

[Claims] 1. A transmitting/receiving device that divides one channel into a transmitting slot and a receiving slot, and performs transmission and reception in the transmitting slot and the receiving slot of the one channel in a time-sharing manner. a modulation circuit that converts the digital audio signal into a modulated signal;
A first mixer circuit that converts the frequency of the modulated signal into a first intermediate frequency signal, a second mixer circuit that converts the frequency of the first intermediate frequency signal into a transmission signal of a predetermined channel, and the first mixer circuit, The first step to perform that frequency conversion is
It has a formation circuit that forms a local oscillation signal, and a control circuit that controls the formation of the first local oscillation signal in the formation circuit, and the control circuit controls the formation of the first local oscillation signal in the formation circuit only during the transmission slot. A transmitting/receiving device that allows formation of a local oscillation signal.