JP4323972B2 - Modulation circuit and modulation method - Google Patents

Description

  The present invention relates to a modulation circuit in a UWB (Ultra Wide Band) transceiver device. In particular, the present invention relates to a modulation circuit for suppressing a direct transmission component (Direct Feed-Through Wave) of an input signal generated by a parasitic capacitance between input and output terminals when a SAW (Surface Acoustic Wave) matched filter is used as a modulation circuit.

Conventionally, a filter connection method for preventing propagation of direct waves in a SAW matched filter is known. For example, according to the invention described in Patent Document 1, in a multi-stage connection configuration of SAW matched filters, two or more stages of SAW matched filters are connected in cascade, and input / output signals connecting between the stages of the SAW matched filter An unbalanced connection is established by connecting at least one of the connection lines to the ground potential. With this configuration, it is possible to prevent propagation of an electrical direct wave from the input to the output of the device.
JP 2000-196411 A

By the way, in recent years, development of UWB transmission / reception apparatuses having a high use frequency band of several GHz has been performed. The applicant has filed an application (Japanese Patent Application No. 2002-262680) relating to a UWB transceiver that employs a SAW matched filter as a modulation circuit.
FIG. 9 is a configuration diagram of a SAW matched filter type UWB transmitter. FIGS. 10 and 11 show electrode patterns of a SAW matched filter used as a pulse modulator (Pulse Modulator).
The upper pattern is a SAW matched filter for generating a reference pulse train, and the middle stage is, for example, data for transmitting information “0” (transmitted at a timing earlier than the reference pulse train). The lower row is a SAW matched filter for pulse generation, for example, data for transmitting information “1” (transmitted at a timing later than the reference pulse train).
The parasitic capacitance generated in the three-stage SAW matched filter is whether the signal input / output method is unbalanced (see Single Ended Signal) (see FIG. 10) or balanced (Balanced Signal) (see FIG. 11). In any case, if a high frequency signal of 3 GHz or higher is input to such a SAW matched filter, the input / output terminal open capacitive coupling is affected by the parasitic capacitance as shown in the figure. As a result, a signal component (direct wave) that is directly transmitted from the input terminal to the output terminal is generated.

  As a result, when a single pulse is input to the SAW matched filter for pulse modulation as shown in FIG. 12, a direct wave is output first, and in most cases, it is larger than the desired wave pulse train output thereafter. It becomes an amplitude. Then, there was a problem that the transmission power specified by the Radio Law was exceeded. Further, when adjustment is made so that the prescribed transmission power is not exceeded, there is a problem that the desired wave pulse train signal becomes small and the communication distance becomes extremely short. Furthermore, there is a problem that the direct wave has an adverse effect as an interference wave when demodulating by the receiver.

  In addition, in the balanced input / output type shown in FIG. 11, the unbalanced input / output type shown in FIG. 10 can be obtained as long as the values of the capacitances Cz and Cy are made equal and the values of the capacitances CX and Cw can be made equal. However, there is a problem that it is very difficult to make the distances of the two paths equal from the viewpoint of pattern layout.

  The present invention has been made in consideration of such circumstances, and the object thereof is from a direct wave generated due to parasitic capacitance in a SAW matched filter, which is a pulse modulator, that is, from an input terminal. An object of the present invention is to provide a modulation circuit and a modulation method that do not radiate a signal component that is directly transmitted to an output terminal to an antenna as a transmission radio wave.

  The present invention has been made to solve the above-described problems. The present invention provides a single pulse generator that generates a single pulse having a positive phase and a single pulse having a reverse phase, and the single pulse generator. The first SAW matched filter that inputs the single pulse of the positive phase or the antiphase from the first pulse and modulates it to a reference pulse train, and the single SAW matched filter from the single pulse generator that has the single phase opposite to the first SAW matched filter A pulse modulation unit including second and third SAW matched filters for inputting a pulse and modulating the pulse to a data pulse train; the reference pulse train from the first SAW matched filter; and the second SAW match And an adder for inputting and adding a data pulse train from either the first filter or the third SAW matched filter.

  Further, according to the present invention, the single pulse generation unit inputs a single pulse from the single pulse generator and generates a single pulse from the single pulse generator. It comprises an unbalanced to balanced converter that generates a single pulse in phase and a single pulse in antiphase.

  Further, according to the present invention, the second SAW matched filter receives a single pulse having an opposite phase to the first SAW matched filter from the single pulse generation unit, and receives a predetermined time from the reference pulse train. The third SAW matched filter receives a single pulse having a phase opposite to that of the first SAW matched filter from the single pulse generation unit, and modulates the data pulse train early. The data pulse train is modulated after being delayed by a predetermined time and output.

  Further, according to the present invention, in a UWB wireless communication apparatus using a SAW matched filter as a modulation circuit, a single pulse generation unit generates a single pulse having a positive phase and a single pulse having a reverse phase, and a plurality of SAWs are generated. A pulse modulation unit including a matched filter modulates the single pulse having the positive phase or the reverse phase to the reference pulse train, and modulates the modulated single pulse and the single pulse having the opposite phase to the data pulse train, and the addition unit. However, the reference pulse train and the data pulse train are added and output.

  The present invention also provides that a single pulse generator generates a single pulse, an unbalanced-balanced converter receives a single pulse from the single pulse generator, an unbalanced-balanced conversion, and a positive phase. A single pulse and an antiphase single pulse are generated.

  According to the present invention, the pulse modulation unit includes first to third SAW matched filters. The first SAW matched filter receives the single pulse of the positive phase or the negative phase, The second SAW matched filter receives a single pulse having a phase opposite to that of the first SAW matched filter, modulates the data pulse train by a predetermined time earlier than the reference pulse train, The third SAW matched filter receives a single pulse having a phase opposite to that of the first SAW matched filter, and modulates the pulse to a data pulse train by a predetermined time later than the reference pulse train.

As described above, according to the present invention, a single pulse having a positive phase and a single pulse having a negative phase are generated, and a single pulse having a positive phase or a negative phase is modulated into a reference pulse train, and the modulation is performed. A single pulse and a single pulse of opposite phase are modulated into a data pulse train, added and output.
By configuring in this way, the direct wave generated from the SAW matched filter that generates the reference pulse train and the direct wave generated from the SAW matched filter that generates the data pulse train are in antiphase, and compared on the time axis, Direct waves having exactly opposite phases are generated at the same time timing, and the subsequent data pulse trains are shifted by a set delay time. As a result, when they are added, the direct waves are canceled each other and only the transmission pulse train in which the other pulse train is inserted between the gaps of one pulse train is output.
Therefore, the radiated power value specified by the Radio Law may be exceeded due to the direct wave having an amplitude larger than the desired wave pulse train, which may interfere with other wireless communication systems, or the direct wave may be changed to the radiated power specified value. To prevent such a phenomenon that the desired signal pulse train becomes too small due to the combination, the communication distance is shortened, and further, the direct wave becomes an interference wave when demodulating on the receiving side and the communication performance deteriorates. The effect that can be obtained.

  Hereinafter, the best mode for carrying out the present invention will be described.

Hereinafter, an embodiment of a UWB wireless communication device to which a modulation circuit of the present invention is applied will be described with reference to the drawings. FIG. 1 is a configuration diagram of a modulation circuit 1 of the present embodiment.
The modulation circuit 1 of this embodiment includes a single pulse generation unit 2, a pulse modulation unit 3, a data control unit 4, and an addition unit 5.
The single pulse generation unit 2 includes a single pulse generator 10 and an unbalance-balancer 20, and generates a single pulse having a positive phase and a single pulse having an opposite phase simultaneously. 3 is supplied. Specifically, as shown in FIG. 2, the single pulse generator 10 generates a single pulse, and the unbalance-balancer 20 inputs the generated single pulse to perform unbalance-balance conversion. Thus, a single pulse having a positive phase and a single pulse having a reverse phase are simultaneously generated.
FIG. 2 shows a more specific implementation example of the modulation circuit 1 shown in FIG. In the circuit configuration of FIG. 2, a transformer is used as the unbalanced-balanced converter 20.
However, since the frequency bandwidth of the transformer is generally narrow, it is not suitable for handling a signal having a very wide bandwidth such as a pulse wave for UWB communication. For this reason, it is conceivable that the operating characteristics are better when a differential amplifier using a broadband transistor as shown in FIG. 3 is applied. In addition to this, even if a 0 ° -180 ° distributor (Hybrid Power Splitter), a 3 dB Hybrid Coupler, or the like is used, the same function is achieved.

The pulse modulation unit 3 includes a plurality of SAW matched filters 30-1 to 30-3. The single pulse generation unit 2 receives a single pulse having a positive phase and a single pulse having a reverse phase, and outputs a positive phase or a reverse phase. A single pulse having a phase is modulated into a reference pulse train, and a single pulse having a phase opposite to that of the modulated single pulse is modulated into a data pulse train.
Specifically, the SAW matched filter 30-1 receives a single pulse having a positive phase or an antiphase from the single pulse generation unit 2, modulates the pulse to a reference pulse train, and either of the SAW matched filters 30-2 and 3 The single pulse generator 2 inputs a single pulse having a phase opposite to that of the SAW matched filter 30-1 and modulates it into a data pulse train.

The data control unit 4 includes a logic data generator 40 and switches 50-1 and 50-2. The data control unit 4 selects either the SAW matched filter 30-2 or the SAW matched filter 30-3 based on which level of the binary logical level the input transmission data is input, and the switch 50 1 is output to the selected SAW matched filter and is modulated by the selected SAW matched filter. The data pulse train is output to the adder 5 via the switch 50-2.
Specifically, depending on whether the data is “O” or “1”, the logic data generator 40 determines whether the data “O” matched filter 30-2 or the data “1” matched filter 30- 3 is selected and switches 50-1 and 50-2 are switched.

  The adder unit 5 includes an adder / synthesizer 60. The adder unit 5 receives the reference pulse train from the SAW matched filter 30-1, and the SAW matched filter 30-2 or the SAW matched filter 30 selected by the data control unit 4. The data pulse train is input from any of -3 and added.

  In the implementation example shown in FIG. 2, a single pulse generator (SRC1, 2), an unbalanced-balanced converter (TF1), a SAW matched filter (SNP1 to 3), a switch (SWITCH1, 2), addition synthesis In addition to the device (PWR1), signal amplifiers (AMP1 to AMP3) and isolators (ISO1 to ISO6) are appropriately added. Moreover, Vi1, Point 2, Vi3, Mod3, Mod1, Mod2 and Tx points indicate acquisition points of signal waveforms (FIGS. 4 to 8) of the computer simulation results executed with the circuit configuration of FIG.

Next, the operation of the conversion circuit 1 of the present embodiment will be described with reference to the drawings. 4 to 8 are signal waveform diagrams showing the process of signal processing in the conversion circuit 1 of the present embodiment.
First, the single pulse generator 2 generates a single pulse having a positive phase for generating a reference pulse train (see FIG. 4) at the point Vi1 before the matched filter 1 and an anti-phase for generating a data pulse train. The single pulse (see FIG. 5) is generated at the point Vi2 before the matched filter 2 or the point Vi3 before the matched filter 3.
Whether a single pulse having an antiphase for generating a data pulse train is generated at the Vi2 point or the Vi3 point depends on whether the transmission data is “O” or “1”. , 2 to select.

When each of the generated single pulses is input to the SAW matched filter 30-1, 2 or 3, a reference pulse train (see FIG. 6) obtained by modulating the single pulse of the positive phase is output to the Mod1 point and the reverse. A data pulse train (see FIG. 7) obtained by modulating a single pulse in phase is output to the Mod2 point. At this time, in the SAW matched filters 30-1, 2 or 3, the direct wave is immediately output regardless of the delay amount set in each of the SAW matched filters 30-1 to 30-3.
When the signal at the Mod 1 point and the signal at the Mod 2 point are compared on the time axis, direct waves having exactly the opposite phase relationship are generated at the same time timing.
On the other hand, the subsequent desired wave pulse trains (reference pulse train and data pulse train) are generated by being shifted by the delay time set in each of the SAW matched filters 30-1 to 30-3.

Therefore, when direct waves having exactly the opposite phase relation generated at the same time timing are added by the adder / synthesizer, the direct waves are canceled each other. 4 to 8, after a large direct wave at the head of the time axis waveform at the Mod 1 point (see FIG. 6) and Mod 2 point (see FIG. 7) is added and synthesized. At the Tx point (see FIG. 8), it can be seen that it has been canceled.
On the other hand, only the transmission pulse trains in which the other pulse train is inserted between the gaps of one pulse train can be output without canceling the desired wave pulse trains (see FIG. 8).

As described above, according to the modulation circuit 1 of the present embodiment, the parasitic capacitance in the SAW matched filter is used when a UWB communication pulse modulator using a SAW matched filter handles a high frequency signal of about 3 GHz or more. The direct wave generated due to the signal, that is, the signal component transmitted directly from the input terminal to the output terminal can be canceled, so that the desired wave pulse train can be obtained without any special design in the SAW matched filter. Can only send.
As a result, in most cases, a direct wave with an amplitude larger than the desired wave pulse train will cause the radiation power value specified by the Radio Law to be exceeded, and other radio communication systems will be disturbed. Can be prevented.
Further, since the direct wave is matched with the radiated power regulation value, it is possible to prevent the desired wave pulse train from becoming too small and the communication distance from being shortened.
Furthermore, it is possible to prevent a phenomenon in which the direct wave becomes an interference wave when demodulating on the receiving side and the communication performance is deteriorated.

1 is a configuration diagram of a modulation circuit 1. FIG. FIG. 2 is a configuration diagram of the modulation circuit 1 in more detail. The block diagram of the unbalance-balance converter by the differential amplifier using a wideband transistor. The positive phase single pulse waveform diagram at the Vi1 point. The single pulse waveform figure of the antiphase in Vi2 point. FIG. 4 is a waveform diagram of a reference pulse SAW modulator output at Mod point. FIG. 4 is a waveform diagram of output of a SAW modulator for data pulses at Mod2 point. The pulse modulator transmission waveform figure in the Tx point. The block diagram of a SAW matched filter system UWB transmission part. Parasitic capacitance of SAW matched filter type modulator of unbalanced signal input / output type. Parasitic capacitance of balanced signal input / output type SAW matched filter type modulator. The modulation waveform figure by the conventional modulator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Modulation circuit 2 ... Single pulse generation part 3 ... Pulse modulation part 4 ... Data control part 5 ... Addition part 10 ... Single pulse generator (SRC1,2)
20: Unbalance-balance converter (TF1)
30-1 to 3 ... SAW matched filter (SNP1 to 3)
40: Logic data generators 50-1, 2 ... switch (SWITCH1, 2)
60. Addition synthesizer (PWR1)

Claims (6)

A single pulse generator that generates a single pulse in the positive phase and a single pulse in the reverse phase;
A first SAW matched filter that inputs a single pulse of the positive phase or the reverse phase from the single pulse generation unit and modulates the pulse to a reference pulse train, and the first SAW matched filter from the single pulse generation unit A pulse modulation unit composed of second and third SAW matched filters that input a single pulse having an opposite phase to and modulates the data pulse train,
An adder that inputs the reference pulse train from the first SAW matched filter and inputs and adds a data pulse train from either the second SAW matched filter or the third SAW matched filter. A modulation circuit. The single pulse generator includes a single pulse generator that generates the single pulse, a single pulse input from the single pulse generator, and an unbalance-balance conversion to generate a positive-phase single pulse. The modulation circuit according to claim 1, further comprising: an unbalanced-balanced converter that generates a single pulse having an opposite phase. The second SAW matched filter receives a single pulse having a phase opposite to that of the first SAW matched filter from the single pulse generation unit, and modulates the data pulse train by a predetermined time earlier than the reference pulse train. Output,
The third SAW matched filter receives a single pulse having a phase opposite to that of the first SAW matched filter from the single pulse generation unit, and modulates the data pulse train by a predetermined time later than the reference pulse train. The modulation circuit according to claim 1, wherein the modulation circuit outputs the output. In a UWB wireless communication device using a SAW matched filter as a modulation circuit,
A single pulse generation unit generates a single pulse having a positive phase and a single pulse having a reverse phase,
A pulse modulation section composed of a plurality of SAW matched filters modulates the single pulse of the positive phase or the reverse phase into a reference pulse train, and modulates the modulated single pulse and the single pulse of the opposite phase into a data pulse train. ,
A modulation method, wherein an adder adds and outputs the reference pulse train and the data pulse train. A single pulse generator generates a single pulse,
An unbalanced-balanced converter receives a single pulse from the single pulse generator and generates unbalanced-balanced conversion to generate a positive-phase single pulse and an anti-phase single pulse. The modulation method according to claim 4. The pulse modulation unit includes first to third SAW matched filters,
The first SAW matched filter inputs the positive-phase or anti-phase single pulse and modulates it to a reference pulse train,
The second SAW matched filter receives a single pulse having a phase opposite to that of the first SAW matched filter, and modulates the data pulse train a predetermined time earlier than the reference pulse train,
The third SAW matched filter receives a single pulse having a phase opposite to that of the first SAW matched filter, and modulates it to a data pulse train by a predetermined time later than the reference pulse train. The modulation method according to claim 4 or 5.

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