JPH09219729A - Radio modulator/demodulator circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio modulator/demodulator circuit capable of reducing circuit scale and cost by staring an orthogonal demodulator and an orthogonal modulator in a transmitter-receiver to be applied for a communication terminal equipment used in an TDD-type radio communication system. SOLUTION: An orthogonal modulator/demodulator 25 is constituted of transmission/reception change-over switches 251-254, multipliers 255 and 256, an adder 257 and a 90 deg. phase shift equipment 258. In the orthogonal modulator/ demodulator 25, the transmission/reception change-over switches 251-254 are changed-over and controlled by a transmission/reception change-over signal inputted from a control part. In the case of being connected to a reception side (RX), the orthogonal demodulator is constituted for a receiving circuit part by the multipliers 255 and 256 and the 90 deg. phase shift equipment 258. In the case of being connected to a transmission side (TX), the orthogonal modulator is constituted for a transmitting circuit part by the multipliers 255 and 256, the adder 257 and the 90 deg. phase shift equipment 258.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless modulation / demodulation circuit applied to a communication terminal used in a TDD wireless communication system.

[0002]

2. Description of the Related Art Conventional TDD (Time Division Duplex:
In a transmitter / receiver applied to a communication terminal used in a wireless communication system of a time division multiplex system, there are an indirect modulation system or a direct modulation system as a transmission system modulation system, and a heterodyne system or a direct conversion system as a reception system demodulation system. There is a system, and a combination of each modulation system and demodulation system is possible as a transmission / reception device.

As a transmission / reception apparatus using such conventional modulation and demodulation methods, for example, as shown in FIG. 4, a time division multiplex direct conversion method (orthogonal demodulation method) is used as a demodulation method, and modulation is performed. There is a circuit configuration using a quadrature modulation system as a system.

In FIG. 4, the transmitter / receiver 1 has an antenna 2 with a receiving circuit side (RX) and a transmitting circuit side (TX).
Switch 3 which is switched to one side and connected, band pass filter (BPF) 4, low noise amplifier (LNA)
5, quadrature demodulator 6, low-pass filter (LPF) 7,
8, a gain control amplifier (GCA) 9, 10 and a receiving circuit section composed of analog-digital converters (ADC) 11, 12 and a low-pass filter (LP).
F) 13, power amplifier (PA) 14 and quadrature modulator 15
And a local oscillator (LO) 16 that supplies a local oscillation signal for channel selection to the quadrature demodulator 6 and the quadrature modulator 15.

A radio signal received from the antenna 2 is input to the receiving circuit section through the switch 3, and a bandpass filter (BPF) 4 of the receiving circuit section extracts a signal in a predetermined frequency band including a carrier frequency band, The low-noise amplifier (LNA) 5 amplifies the signal at a predetermined amplification rate, and the 90 ° phase shifter (π / 2) 6a and the multipliers (MULT) 6b and 6c.
The quadrature demodulator 6 constituted by the above is converted into baseband signals I and Q in the baseband band. The baseband signals I and Q are low pass filters (LP
F) 7, 8, gain control amplifier (GCA) 9,
10 and an analog-to-digital converter (ADC) 11,
A baseband processing circuit composed of 12 converts the signal into a band-limited and digital signal and sends it to a baseband signal processing circuit (not shown).

Gain control amplifier (GCA) 9,
In 10, the control is performed to the optimum input level to be input to the analog-digital converters (ADC) 11 and 12 corresponding to the signal strengths of the baseband signals I and Q input from the low pass filters (LPF) 7 and 8. Circuit.

On the other hand, at the time of transmission, the baseband signals I and Q input from the baseband signal processing circuit (not shown) are multiplied by the multipliers (MULT) 15a and 15b and the adder (ADD) 1.
5c and a 90 ° phase shifter (π / 2) 15d.
A) Amplifies the signal at a predetermined amplification rate by a low-pass filter (LPF) 13 to remove spurious components (extra frequency signal components generated in the vicinity of the main carrier frequency), and then transmits the antenna 2 through a TX port of a switch 3. Is transmitted as a radio signal according to the carrier frequency band.

[0008]

However, in the transmitter / receiver shown in FIG. 4 applied to a communication terminal used in such a conventional TDMA-TDD type wireless communication system, a receiving circuit section and a transmitter are provided. Since the circuit configuration has the quadrature demodulator 6 and the quadrature modulator 16, respectively, the circuit configuration is complicated and the circuit scale is increased, and the cost of the transceiver is increased.

An object of the present invention is to use a quadrature demodulator and a quadrature modulator in a transmission / reception apparatus which are applied to a communication terminal used in a TDD wireless communication system in common to reduce the circuit scale and cost. It is to provide a modulation / demodulation circuit.

[0010]

According to the first aspect of the present invention,
In a TDD wireless modulation / demodulation circuit, an I-phase multiplier that multiplies an input signal by a local signal in a carrier frequency band and outputs the result, and a Q-phase multiplication that multiplies the input signal by the π / 2 phase-shifted local signal and outputs the result. And an adder for adding the first and second input signals and outputting as a transmission signal,
At the time of reception, the received signal is input as an input signal to each of the I-phase multiplier and the Q-phase multiplier, and the output from each of the multipliers is directly output as the I-phase and Q-phase baseband signals. The phase and Q phase baseband signals are input to the I phase multiplier and the Q phase multiplier, and the outputs from the respective multipliers are input as the first and second input signals of the adder. And a switching circuit for switching the input and output of each of the multipliers.

According to the radio modulation / demodulation circuit of the invention described in claim 1, in the radio modulation / demodulation circuit of the TDD system, the input signal is multiplied by an I-phase multiplier for multiplying the input signal by the local signal in the carrier frequency band and output. a Q-phase multiplier that multiplies the local signal that is phase-shifted by π / 2 and outputs the multiplied signal;
And an adder that adds the second input signal and outputs the added signal as a transmission signal, and the reception signal is input as an input signal to each of the I-phase multiplier and the Q-phase multiplier by the switching circuit during reception. At the same time, the outputs from the respective multipliers are directly output as I-phase and Q-phase baseband signals, and the I-phase and Q-phase baseband signals are input to the I-phase and Q-phase multipliers during transmission. In addition, the input and output of each of the multipliers are switched so that the output from each of the multipliers is input as the first and second input signals of the adder.

Therefore, in a radio modulation / demodulation circuit applied to a communication terminal used in a conventional TDD radio communication system, a quadrature demodulation circuit provided in a reception circuit section and a quadrature modulation provided in a transmission circuit section are provided. It is not necessary to separately provide a circuit and a quadrature demodulation circuit and a quadrature modulation circuit can be collectively configured as a quadrature modulator / demodulator,
The circuit scale can be reduced, and the manufacturing cost of the transmission / reception device can be reduced.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings.

1 to 3 are diagrams showing an embodiment of a radio modulation / demodulation circuit to which the present invention is applied.

First, the configuration will be described.

FIG. 1 is a diagram showing a block configuration of a main circuit of a transmission / reception device 20 of this embodiment.

In FIG. 1, the transmitter / receiver 20 includes an antenna 21, a changeover switch 22, a receiving circuit section including a bandpass filter 23, a low noise amplifier 24 and a quadrature modulator / demodulator 25, and a lowpass filter 26.
27, gain control amplifiers 28, 29 and analog-digital converters 30, 31 for baseband processing circuit section, quadrature modulator / demodulator 25, power amplifier 32, and low-pass filter 33 for transmission circuit section, and local section And an oscillator 34.

The changeover switch 22 is switch-controlled by a transmission / reception changeover signal input from a control unit (not shown), and connects the antenna 21 by switching it between one of the receiving circuit unit side and the transmitting circuit unit side.

The bandpass filter (BPF) 23 has a frequency characteristic of removing a reception interference wave from the carrier frequency band signal, removes the reception interference wave from the radio signal received by the antenna 32, and outputs the carrier frequency band signal. It is extracted and output to the low noise amplifier 24.

The low noise amplifier 24 (LNA) amplifies the carrier frequency band signal input from the band pass filter 23 with a predetermined amplification factor and outputs it to the quadrature modulator / demodulator 25.

The quadrature modulator / demodulator 25 includes transmission / reception changeover switches 251-254, multipliers 255, 256, and an adder 2.
It is composed of 57 and 90 ° phase shifters 258. In the orthogonal modulator / demodulator 25, the transmission / reception changeover switches 251-
When 254 is switched and controlled by a transmission / reception switching signal input from a control unit (not shown) and is connected to the reception side (RX), multipliers 255, 256 and 90 are provided.
The quadrature phase shifter 258 constitutes a quadrature demodulator for the receiving circuit section, and when connected to the transmission side (TX), the multipliers 255 and 256, the adder 257, and the 90 ° phase shifter 25
8 constitutes a quadrature modulator for the transmission circuit section.

That is, when the quadrature modulator / demodulator 25 functions as a quadrature demodulator for the receiving circuit section, the carrier frequency band signal amplified by the low noise amplifier 24 is transmitted / received.
Multiplier 25 through reception changeover switches 251, 253
5 and 256, the multiplier 255 multiplies the received wave generated by the local oscillator 34 by the same frequency signal <f1> and converts it into a baseband signal I in the baseband band. The same frequency signal <f1> as the received wave generated by the oscillator 34 is further multiplied by the π / 2 frequency signal 90 ° phase-shifted by the 90 ° phase shifter 258 to form a baseband signal Q in the baseband band. The converted baseband signals I and Q are output to the baseband processing circuit section through the transmission / reception changeover switches 252 and 254.

When the quadrature modulator / demodulator 25 functions as a quadrature modulator for the transmission circuit section, the baseband signals I and Q generated by a baseband signal processing circuit (not shown) are transmitted / received. Changeover switches 252, 254
When input to the multipliers 255 and 256 through the multiplier 255, the multiplier (MULT) 255 multiplies the received wave generated by the local oscillator 34 by the same frequency signal <f1> and modulates the received wave.
In the multiplier (MULT) 256, the same frequency signal <f1> as the received wave generated by the local oscillator 34 is further multiplied by the π / 2 frequency signal 90 ° phase-shifted by the 90 ° phase shifter 258 and modulated. , This multiplier 255, the multiplier 25
The modulated signals modulated by 6 are added by the adder (ADD) 257 and output to the power amplifier 32.

The baseband processing circuit unit removes signals other than the desired reception wave from the baseband signals I and Q demodulated by the quadrature modulator / demodulator 25 by the low pass filters (LPF) 26 and 27, and the gain control amplifier (GC).
A) 28, 29 sets the optimum input level corresponding to each signal strength of the baseband signals I, Q input from the low-pass filters 26, 27, and the analog-digital converter (ADC) 30, 31 The band signals I and Q are converted into digital signals and output to a baseband signal processing circuit (not shown).

The transmission circuit unit amplifies the modulated signal modulated by the quadrature modulator / demodulator 25 by the power amplifier (PA) 32 to a predetermined output level, and the low pass filter (LPF) 33.
After removing the spurious component of the modulated signal by the above, it is transmitted from the antenna 21 via the TX port of the switch 22 as a radio signal according to the carrier frequency band.

The local oscillator (LO) 34 outputs the same frequency signal <f1> as the received wave to the multiplier 2 in the quadrature modulator / demodulator 25.
Supply to the 55 and 90 ° phase shifter 258.

The multiplier 2 in the quadrature modulator / demodulator 25 is also used.
A specific circuit configuration of 55 and 256 is shown in FIG. This FIG. 2 is an example in which a multiplier is configured with a transistor circuit,
The frequency signal <f1> from the local oscillator (LO) 34 is applied to each base electrode of the transistors Q1 and Q2, or 90
The π / 2 frequency signal which is phase-shifted by 90 ° by the phase shifter 258 is input, the constant current source I0 is connected to the commonly connected emitter electrodes, and the carrier frequency band signal from the low noise amplifier (LNA) 24 is input. As a result, the differential outputs from the collector electrodes of the transistors Q1 and Q2 are output as the baseband signals I and Q at the time of demodulation and as the modulation signal at the time of modulation.

In the case of the circuit configuration of the multipliers 255 and 256, the constant current source I0 connected to the common emitter electrode can be used for quadrature modulation at the time of transmission because it is shared by the quadrature modulation / demodulation at the time of transmission / reception. Requires a large rated output.

Next, the operation of this embodiment will be described.

First, the operation at the time of reception will be described.

When the radio signal <f1> is received by the antenna 21, the changeover switch 22 is switched to the receiving circuit section side, the reception interference wave is removed by the band pass filter 23, the carrier frequency band signal is extracted, and low noise is generated. The signal is output to the amplifier 24, amplified by the low noise amplifier 24 at a predetermined amplification rate, and output to the quadrature modulator / demodulator 25.

Then, the amplified carrier frequency band signal is transmitted / received by the transmission / reception changeover switch 25 in the quadrature modulator / demodulator 25.
By switching from 1 to 254 to the receiving side, multipliers 255 and 25
By the quadrature demodulator composed of the 6 and 90 ° phase shifters 258, the multiplier 255 multiplies the received wave generated by the local oscillator 34 by the same frequency signal <f1> to obtain the baseband signal I of the baseband. Converted and multiplied by 256
Then, the same frequency signal <f1> as the received wave generated by the local oscillator 34 is further detected by the 90 ° phase shifter 258.
Multiplied by a phase-shifted π / 2 frequency signal and converted into a baseband signal Q in the baseband band, and the converted baseband signals I and Q are subjected to baseband processing through transmission / reception changeover switches 252 and 254. It is output to the circuit section.

Then, in the baseband processing circuit section, the baseband signals I and Q demodulated by the quadrature modulator / demodulator 25 are used.
Are removed by the low-pass filters 26 and 27 except signals desired to be received, and the gain control amplifier 2
8, 29 sets the optimum input level corresponding to each signal strength of the baseband signals I, Q, and the analog-digital converters 30, 31 set the baseband signals I, Q.
Is converted into a digital signal and output to a baseband signal processing circuit (not shown).

Next, the operation during transmission will be described.

At the time of transmission, the changeover switch 22 is changed over to the transmission circuit section side, and the transmission / reception changeover switches 251 to 254 in the quadrature modulator / demodulator 25 are changed over to the transmission side so that the multipliers 255, 256, the adder 257, and 90 ° phase shifter 25
Baseband signals I and Q are transmitted / received from a baseband signal processing circuit (not shown) to the quadrature modulator composed of 8
When input through the reception changeover switches 251, 253, the multiplier 255 multiplies and modulates the same frequency signal <f1> as the received wave generated by the local oscillator 34 and the baseband signal I, and the multiplier (MULT) 256 Then, the same frequency signal as the received wave generated by the local oscillator 34 <f1
> Is further modulated by multiplying the π / 2 frequency signal 90 ° phase-shifted by the 90 ° phase shifter 258 and the baseband signal Q, and the modulated signals modulated by the multiplier 255 and the multiplier 256 are Power amplifier 3 added by adder 257
2 is output.

Then, in the transmitting circuit section, the power amplifier 32
The quadrature modulator / demodulator 25 amplifies the modulated signal up to a predetermined output level, and the low-pass filter 33 removes the spurious component of the amplified modulated signal. Then, the antenna 21 is fed from the antenna 21 via the TX port of the switch 22. It is transmitted as a radio signal according to the carrier frequency band.

As described above, in the transmitter / receiver 20 of this embodiment, the multipliers 255, 256 and the adders 257 and 9 are used.
A 0 ° phase shifter 258 is provided, and the connection relationship of each circuit block is connected to the receiving circuit section as a quadrature demodulator or is connected to the transmitting circuit section as a quadrature modulator.
Since the quadrature modulator / demodulator 25 including the reception changeover switches 251 to 254 is used, the quadrature modulator / demodulator of the present invention shares the multiplier, adder and 90 ° phase shifter which have been conventionally used in the quadrature demodulator and the quadrature modulator. The container 25 can be easily configured.

Therefore, it is no longer necessary to separately provide the quadrature demodulation circuit provided in the conventional receiving circuit section and the quadrature modulation circuit provided in the transmission circuit section, and the quadrature demodulation circuit and the quadrature modulation circuit are orthogonalized. The modulator / demodulator 25 can be configured as a whole, the circuit scale can be reduced, and the manufacturing cost of the transceiver 20 can be reduced.

In the transistor circuit constituting the multipliers 255 and 256 shown in FIG. 2 of the above embodiment, the constant current source I0 needs to have a large rated output so that it can be used for quadrature modulation during transmission. However, in this case, the constant current source I0 consumes a similar current at the time of transmission at the time of quadrature demodulation at the time of reception. In order to suppress the current consumption, for example, multipliers 255 and 25 having a circuit configuration as shown in FIG.
6 is considered.

In the circuit of FIG. 3, a constant current source I0 having a large rated output for quadrature modulation at the time of transmission and a constant current source I1 having a small rated output for quadrature demodulation at the time of reception are provided. By switching and connecting I0 and I1 at the time of transmission and at the time of reception by the changeover switch SW, it is possible to suppress current consumption during quadrature demodulation during reception.

[0041]

According to the radio modulation / demodulation circuit of the first aspect of the present invention, in the radio modulation / demodulation circuit applied to the communication terminal used in the conventional TDD radio communication system, the quadrature provided in the receiving circuit section is used. It is not necessary to separately provide the demodulation circuit and the quadrature modulation circuit provided in the transmission circuit section, and the quadrature demodulation circuit and the quadrature modulation circuit can be collectively configured as a quadrature modulator / demodulator, which reduces the circuit scale. It is possible to reduce the manufacturing cost of the transceiver.

[Brief description of drawings]

FIG. 1 is a diagram showing a circuit block configuration of a transmission / reception device to which the present invention is applied.

FIG. 2 is a diagram showing a circuit configuration when the multiplier of FIG. 1 is configured by a transistor circuit.

FIG. 3 is a diagram showing another circuit configuration when the multiplier of FIG. 1 is configured by a transistor circuit.

FIG. 4 is a circuit configuration diagram of a transmission / reception device applied to a communication terminal used in a conventional wireless communication system.

[Explanation of symbols]

 20 transmitter / receiver 21 antenna 22 changeover switch 23 band pass filter 24 low noise amplifier 25 quadrature modulator / demodulator 26, 27 low pass filter 28, 29 gain control amplifier 30, 31 analog-digital converter 32 power amplifier 33 low pass filter 34 local oscillator 251 to 254 Transmission / reception switch 255, 256 Multiplier 257 Adder 258 90 ° phase shifter

Claims (1)

[Claims] 1. In a TDD wireless modulation / demodulation circuit, an I-phase multiplier that multiplies an input signal by a local signal in a carrier frequency band and outputs the result, and an input signal is multiplied by the local signal that is phase-shifted by π / 2. A Q-phase multiplier for outputting, an adder for adding the first and second input signals and outputting as a transmission signal, and a reception signal during reception as an input signal for each of the I-phase and Q-phase multipliers. When input, the outputs from the respective multipliers are directly output as I-phase and Q-phase baseband signals, and the I-phase and Q-phase baseband signals are input to the I-phase and Q-phase multipliers during transmission. And a switching circuit that switches the input and output of each of the multipliers so that the output from each of the multipliers is input as the first and second input signals of the adder. A wireless modulation / demodulation circuit characterized by the above.