JP2012195638A - Transmitter-receiver circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform desired frequency conversion when the frequency of a local oscillation signal changes over a wide range.SOLUTION: A transmitter-receiver circuit includes: a synthesizer to output a local oscillation signal; first multiphase signal generation means having a plurality of delay circuits connected in multiple stages, which generates from the local oscillation signal fed into the delay circuits a multiphase local oscillation signal; a transmit circuit containing a first mixer circuit which accepts the multiphase signal as its input and converts a transmit signal in baseband bandwidth to a carrier frequency; second multiphase signal generation means which generates from the local oscillation signal fed thereinto a multiphase local oscillation signal; and a receive circuit containing a second mixer circuit which converts the frequency of a received signal at the carrier frequency to a baseband bandwidth. The delay circuits, which are used for generating a first delay time and a second delay time, generates the first delay time or the second delay time whichever is selected.

Description

  The present invention relates to a transmission / reception circuit using frequency conversion by a multiphase signal.

  As a radio technology capable of short-distance high-speed communication, an ultra-wide band radio (UBW) has been developed. In ultra-wideband radio, there are two different standards, the MB-OFDM (MultiBand Orthogonal Frequency Division Multiplexing) method and the DS-UWB (Direct Sequence UWB) method, but the following description assumes the MB-OFDM method.

  The band used in the ultra-wideband radio is different from each other in the world in detail, but is extremely wide as 3 to 11 GHz. With the development of ultra-wideband radio, various ultra-wideband radio transceiver chips are also being developed. In this transmission / reception chip, when a direct conversion method with a simple configuration is adopted, the transmission / reception chip generates a local oscillation signal of 3 to 11 GHz by a synthesizer, and performs frequency conversion by a frequency conversion circuit. For example, Patent Document 1 describes a transmission / reception system that transmits a local oscillation signal having a frequency of 1 / n times and performs frequency conversion based on output signals of n phase shifters in series.

  However, the synthesizer that generates a local oscillation signal of 3 to 11 GHz and the buffer circuit that transmits the signal to each frequency conversion circuit for transmission and reception increase the power consumption because the signal handled is high frequency and wideband, There is a problem that the area of the circuit becomes large.

  Conventionally, as a solution to this problem, a 1 / N frequency of the carrier frequency is generated by a synthesizer, and this is converted into N signals whose phases are shifted by a multiphase signal generation circuit (multiphase), and the frequency conversion circuit is used. Thus, a technique for adding the multiphase components simultaneously with the frequency conversion is already known. According to this solution, frequency conversion equivalent to frequency conversion at the original carrier frequency can be realized.

  Among these, the multiphase signal generation circuit has a configuration in which delay circuits having variable delay times are connected in multiple stages. With this configuration, a multiphase signal can be obtained by taking out the output of each delay circuit. In addition, the delay time of the delay circuit can be controlled to generate a multiphase signal having a desired phase interval.

  A conventional transmission / reception chip will be described below with specific examples. In the following description, it is assumed that the transmission / reception chip is mounted with a synthesizer that only supports transmission / reception of a local oscillation signal of approximately 6 to 11 GHz.

  Specifically, there are eight carrier frequencies: 6600 MHz, 7128 MHz, 7565 MHz, 8184 MHz, 8712 MHz, 9240 MHz, 9768 MHz, and 10296 MHz. In this transmission / reception chip, a synthesizer generates a 1/3 frequency of the carrier frequency. That is, there are eight types of local oscillation signals output from the synthesizer: 2200 MHz, 2376 MHz, 2552 MHz, 2728 MHz, 2904 MHz, 3080 MHz, 3256 MHz, and 3432 MHz.

  In this case, the multi-phase signal generation circuit needs to generate a 12-phase (30-degree interval) multi-phase signal with the local oscillation signal from the synthesizer as an input. Since this is a quadrature modulation method, 2 × 2 × 3 = 12 phases are required because it is a differential signal and the synthesizer generates a local oscillation signal having a frequency of 1/3 of the carrier frequency. Because.

  In this transmission / reception chip, assuming that the phase is delayed by 30 degrees per stage of the delay circuit, the delay time is about 37.9 psec when the signal frequency is 2200 MHz and about 24.3 psec when the signal frequency is 3432 MHz. In order to do this, the delay time that must be achieved varies by approximately 1.6 times.

  However, in the above conventional transmitter / receiver chip, it is possible to change the delay time over a wide range as described above, and to design a polyphase signal generation circuit with an operational margin in consideration of manufacturing variations. Is difficult. Therefore, in the conventional transmission / reception chip, it may be difficult to perform desired frequency conversion when the local oscillation frequency changes in a wide range.

  The present invention has been made in view of the above circumstances, and provides a transmission / reception circuit capable of performing desired frequency conversion when the frequency of a local oscillation signal changes in a wide range. It is aimed.

  The present invention employs the following configuration in order to achieve the above object.

  The present invention includes a synthesizer that outputs a local oscillation signal and a plurality of delay circuits connected in multiple stages, and the first oscillation signal is generated by inputting the local oscillation signal to each of the delay circuits. Multi-phase signal generation means, a transmission circuit including a first mixer circuit that receives the multi-phase signal generation and converts a baseband transmission signal into a carrier frequency, and inputs the local oscillation signal. A second multi-phase signal generating means for generating a phase local oscillation signal, and a receiving circuit including a second mixer circuit for frequency-converting the received signal of the carrier frequency to a baseband, the delay circuit being The first delay time and the second delay time are generated, and the selected one of the first delay time and the second delay time is generated.

  The transmission / reception circuit of the present invention has baseband digital processing means for processing a baseband signal which is a signal in the baseband band, and the baseband digital processing means has the second delay time selected. Then, the phase of the baseband signal is switched.

  In the transmission / reception circuit of the present invention, the amount of phase change corresponding to the first delay time is 150 degrees, and the amount of phase change corresponding to the second delay time is 210 degrees.

  According to the present invention, desired frequency conversion can be performed when the frequency of the local oscillation signal changes in a wide range.

It is a figure which shows the transmission / reception circuit of this embodiment. It is a figure explaining the mixer circuit of the transmission system of this embodiment. It is a figure explaining the mixer circuit which does not use a polyphase signal. It is a figure explaining operation | movement of the mixer circuit shown in FIG. 2, and the mixer circuit shown in FIG. It is a figure explaining the conventional multiphase signal generation circuit. It is a figure explaining the multiphase signal generation circuit of this embodiment. It is a 1st figure explaining operation | movement of the multiphase signal generation circuit of this embodiment. It is a 2nd figure explaining operation | movement of the multiphase signal generation circuit of this embodiment. It is a flowchart explaining the calibration of the transmission / reception circuit of this embodiment. It is a figure explaining the bias circuit of this embodiment. It is a figure explaining the delay time of the conventional delay circuit. It is a figure explaining the delay time of the delay circuit of this embodiment.

  In the transmission / reception circuit of this embodiment, the phase change difference per delay circuit can be selected by the multiphase signal generation circuit, and the phase of the baseband signal is switched in accordance with the phase change amount.

(Embodiment)
The transmission / reception circuit of this embodiment will be described below with reference to the drawings. FIG. 1 is a diagram illustrating a transmission / reception circuit according to the present embodiment.

  The transmission / reception circuit 100 of the present embodiment has a configuration in which a frequency conversion circuit using a multiphase signal is applied based on a general direct conversion method.

  The transmission / reception circuit 100 of the present embodiment includes a multiphase signal generation circuit 110, 120, a synthesizer 130, a mixer circuit 140, 150, a smoothing filter 160, 190, a variable gain amplifier 170, an ADC (Analog to Digital Converter) 180, a DAC ( Digital to Analog Converter) 195, baseband digital processing unit 197, and antenna 199.

  The multiphase signal generation circuits 110 and 120 generate multiphase signals. The synthesizer 130 generates a local oscillation signal. The mixer circuit 140 performs frequency conversion of the received signal. The smoothing filter 160 is a reception system filter, and smoothes the signal output from the mixer circuit 140. The mixer circuit 150 performs frequency conversion of the transmission signal. The smoothing filter 190 is a transmission filter, and smoothes the signal output from the DAC 195. The baseband digital processing unit 197 is a circuit that handles baseband signals.

  The synthesizer 130 of the present embodiment can generate local oscillation signals having eight frequencies of 2200 MHz, 2376 MHz, 2552 MHz, 2728 MHz, 2904 MHz, 3080 MHz, 3256 MHz, and 3432 MHz, which are 1/3 of the carrier frequency.

  In the present embodiment, the multiphase signal generation circuits 110 and 120 are arranged in the vicinity of the mixer circuits 140 and 150 for reception and transmission, respectively. In the present embodiment, this configuration can reduce the phase shift due to the influence of parasitic elements that occur in the layout of the multiphase signal.

  Next, the mixer circuits 140 and 150 of this embodiment will be described. In the present embodiment, the configuration of the receiving mixer circuit 140 and the transmitting mixer circuit 150 is the same. Therefore, in the following description, the mixer circuit 150 will be described as an example. FIG. 2 is a diagram for explaining a transmission-system mixer circuit according to the present embodiment.

  The mixer circuit 150 of this embodiment performs frequency conversion using a tripled multiphase signal.

  The mixer circuit 150 shown in FIG. 2 has a configuration using multiphase signals corresponding to the IQ orthogonal transform method.

  In the mixer circuit 150 of this embodiment, the transistors 12 to 15 convert the voltage of the baseband signal into a current. In this embodiment, I-phase and Q-phase baseband signals are input to the gates of the transistors 12 and 13 and the transistors 14 and 15, respectively. The transistors 16 to 63 are a signal A +, a signal A−, a signal B +, a signal B−, a signal C +, a signal C−, a signal D +, a signal D−, and a signal E + that are multiphase signals generated by the multiphase signal generation circuit 120. , The switching operation is performed by the signal E−, the signal F +, and the signal F−. In the mixer circuit 150 of this embodiment, frequency conversion is performed by this switching operation.

  Next, in order to describe the operation of the mixer circuit 150 of the present embodiment, a mixer circuit that performs frequency conversion equivalent to the mixer circuit 150 shown in FIG. 2 without using multiphase signals will be described. FIG. 3 is a diagram illustrating a mixer circuit that does not use multiphase signals.

  In the mixer circuit 150A shown in FIG. 3, the transistors 64 to 67 convert the voltage of the baseband signal into a current. I-phase and Q-phase baseband signals are input to the gates of the transistors 64 and 65 and the transistors 66 and 67, respectively. The mixer circuit 150A performs frequency conversion by the transistors 68 to 75 performing switching operations according to the signals (1) to (4) from the local oscillator.

  Next, operations of the mixer circuit 150 and the mixer circuit 150A of this embodiment will be described with reference to FIG. 4 is a diagram for explaining the operation of the mixer circuit shown in FIG. 2 and the mixer circuit shown in FIG.

  Signals A ± to F ± and signals (1) to (4) illustrated in FIG. 4 are signals that cause the mixer circuit 150 and the mixer circuit 150A to perform an equivalent operation.

  As shown in FIG. 4, in order for the mixer circuit 150 and the mixer circuit 150A to perform equivalent frequency conversion, for example, the duty ratio of the signal A +, the signal C−, and the signal E + is 50%, and the phases are 120 degrees each other. As long as it is off. The frequency of the signals A ± to F ± is 1/3 times the frequency of the signals (1) to (4).

  Hereinafter, the comparison between the operation of the transistors 22 to 27 of the mixer circuit 150 and the operation of the transistor 69 of the mixer circuit 150A will be described as being equivalent to each other.

  In the transistors 22 to 27 of the mixer circuit 150, when the transistor 22 and the transistor 23 are on, the transistor 24 and the transistor 25 are on, or the transistor 26 and the transistor 27 are on, the current as a whole is Can be turned on.

  That is, in the mixer circuit 150A, it is understood that the transistor 69 is in the same state as the state in which the transistor 69 is turned on by the signal (1), and both are equivalent.

  Next, the multiphase signal generation circuits 110 and 120 of this embodiment will be described. First, a conventional multiphase signal generation circuit will be described for comparison with the multiphase signal generation circuits 110 and 120 of the present embodiment. FIG. 5 is a diagram for explaining a conventional multiphase signal generation circuit.

  The conventional multiphase signal generation circuit 110A shown in FIG. 5 includes a delay circuit 76, an output buffer 77, a phase comparator 78, a smoothing filter 79, and a bias circuit 80.

  In the delay circuit 76, a fixed delay time is generated from the input to the output, and the delay time (phase change amount) can be controlled by the bias circuit 80. In the multiphase signal generation circuit 110A shown in FIG. 5, the delay time is controlled so that the phase of the input signal is delayed by 30 degrees per stage of the delay circuit 76 in the entire multiphase signal generation circuit 110A. Shall. That is, the delay amount per stage of the delay circuit 76 is 30 degrees.

  The buffer 77 amplifies and takes out the output of the delay circuit 76. The phase comparator 78 compares the phases of the multiphase signals and outputs the result. Here, the phase comparator 78 compares the phase change amount (delay amount) of the delay circuit 76 for three stages, and has an input / output characteristic such that the output becomes zero when the delay amount is 90 degrees. It was. The smoothing filter 79 smoothes the phase comparison result. The bias circuit 80 changes the delay time of the delay circuit 76 in proportion to the output voltage of the smoothing filter 79.

  Next, the multiphase signal generation circuits 110 and 120 included in the transmission / reception circuit 100 of this embodiment will be described. In the present embodiment, since the multiphase signal generation circuits 110 and 120 have the same configuration, FIG. 6 will be described using the transmission multiphase signal generation circuit 110 as an example.

  FIG. 6 is a diagram illustrating the multiphase signal generation circuit according to the present embodiment.

  The multiphase signal generation circuit 110 of this embodiment includes a delay circuit 76A, an output buffer 77, a phase comparator 78, a smoothing filter 79, and a bias circuit 80. Since the output buffer 77, the phase comparator 78, the smoothing filter 79, and the bias circuit 80 of this embodiment are the same as the multiphase signal generation circuit 110A described with reference to FIG.

  The delay circuit 76A of this embodiment can select either 150 degrees or 210 degrees as the delay amount per stage of the delay circuit 76A. In the present embodiment, the one-stage delay circuit 76A includes a plurality of delay circuits. In the present embodiment, the delay circuit 76A includes delay circuits 76a and 76b. In the present embodiment, the delay amount can be set to 150 degrees or 210 degrees by configuring the one-stage delay circuit 76A with a plurality of delay circuits in this way.

  The phases of the signals A ± to F ± output from the multiphase signal generation circuit 110 are different depending on whether the delay amount of the delay circuit 76A is 150 degrees or 210 degrees.

  The operation of the multiphase signal generation circuit 110 of this embodiment will be described below with reference to FIGS. FIG. 7 is a first diagram for explaining the operation of the multiphase signal generation circuit of this embodiment, and FIG. 8 is a second diagram for explaining the operation of the multiphase signal generation circuit of this embodiment. FIG. 7 shows the operation of the multiphase signal generation circuit 110 when the delay amount of the delay circuit 76A is 150 degrees, and FIG. 8 shows the operation of the multiphase signal generation circuit 110 when the delay amount of the delay circuit 76A is 210 degrees. The operation is shown. Further, the signals (1) to (4) shown in FIGS. 7 and 8 are the signals (1) shown in FIG. ) To (4).

  Signals (1) to (4) in FIG. 7 have the same phase as signals (1) to (4) in FIG. 4, and signals (1) to (4) in FIG. 8 are signals (1) to (4) in FIG. Compared with 4), (3) and (4) are reversed.

  In other words, if the multiphase signal generation circuit 110 of this embodiment is used, it can be said that when the delay amount of the one-stage delay circuit 76A is 150 degrees, it is equivalent to the multiphase signal generation circuit 110A. Further, in the multiphase signal generation circuit 110 of the present embodiment, when the delay amount of the one-stage delay circuit 76A is 210 degrees, the signal (3) and the signal (4) are switched in the mixer circuit 150A of FIG. Or, if the Q phase of the baseband signal is inverted, it is equivalent to the multiphase signal generation circuit 110A.

  That is, in the multiphase signal generation circuit 110 of the present embodiment, in order to operate equally when the delay amount of the delay circuit 76A of one stage is 150 degrees and 210 degrees, the mixer circuit shown in FIG. It is only necessary to invert the signal input to the gates of the 150 transistors 14 and 15 or the signal input to the gates of the transistors 12 and 13. Alternatively, the baseband digital processing unit 197 of the transmission / reception circuit 100 can invert the sign of the Q phase (Quadrature Phase) of the orthogonal data to be transmitted, and the delay amount of the delay circuit 76A is selected to be 150 degrees or 210 degrees. It may be reversed according to the condition.

  Hereinafter, with reference to FIG. 9, the calibration executed before the transmission / reception circuit 100 performs transmission / reception will be described. FIG. 9 is a flowchart illustrating calibration of the transmission / reception circuit of the present embodiment. The calibration is performed in response to an execution instruction from a control unit (not shown) that controls the transmission / reception circuit 100 of the present embodiment. Calibration is performed in order to select a delay amount of 150 degrees or 210 degrees because the delay amount that can be realized varies depending on variations in the manufacturing process, operating temperature, and power supply voltage conditions. The calibration is performed after the power is supplied to the transmission / reception circuit 100 and before actually transmitting / receiving data.

  The transceiver circuit 100 of this embodiment generates a local oscillation signal by the synthesizer 130 (step S901). When the respective frequencies are output from the synthesizer 130, the delay time of the delay circuit 76A of the multiphase signal generation circuit 110 is controlled and waits until the output is stabilized (step S902). Thereafter, it is determined whether the delay amount of the delay circuit 76A is 150 degrees or 210 degrees, and is recorded in the memory together with the frequency of the current local oscillation signal (step S903). The memory may be a storage area provided in the baseband digital processing unit 197, for example. Details of the determination of the delay amount will be described later.

  When step S902 and step S903 are completed for one frequency, the transmission / reception circuit 100 changes the frequency of the local oscillation signal in the synthesizer 130, and returns to step S901 (step S904). In step S904, the frequency of the local oscillation signal is changed in the order of 2200 MHz, 2376 MHz, 2552 MHz, 2728 MHz, 2904 MHz, 3080 MHz, 3256 MHz, and 3432 MHz. In this embodiment, the initial state of the transmission / reception circuit 100 is cleared at this time, so that a pseudo lock state that falls into another stable state due to a difference in the initial state is not caused.

  The above is the operation of the transmission / reception circuit 100 of the present embodiment at the time of calibration. In the normal operation of the transmission / reception circuit 100 of this embodiment, every time the synthesizer 130 changes the frequency of the local oscillation signal, the delay amount corresponding to the frequency stored in the memory is read. If the read delay amount is 210 degrees, the baseband digital processing unit 197 inverts the sign of the Q phase of the baseband signal.

  Next, the determination of the delay amount in the present embodiment will be described with reference to FIG. FIG. 10 is a diagram illustrating the bias circuit of the present embodiment.

  The bias circuit 80 of the present embodiment is provided in the multiphase signal generation circuit 110 and has a function of determining whether the delay amount of the delay circuit 76A is 150 degrees or 210 degrees. In FIG. 10, only one stage of the delay circuit 76A to which the bias circuit 80 is applied is shown as an example.

  In the bias circuit 80, the transistor 85 causes a current to flow in accordance with the voltage input Vin. During normal operation, the switch 83 is off, and the bias current is determined only by the power input Vin.

  When the control of the multiphase signal generation circuit 110 is stabilized, the bias circuit 80 generates a bias current in which the switch 83 is turned on and the constant current 82 is added. When the bias current is generated, the output of the phase detector 78 changes. In the present embodiment, the output of the phase detector 78 or the smoothing filter 79 is detected, and the delay amount per stage of the delay circuit 76A is 150 degrees depending on whether the output has changed to positive or negative. Determine if it is a degree.

  In the present embodiment, for example, the baseband digital processing unit 197 may monitor the output of the phase detector 78 or the smoothing filter 79. In this case, the baseband digital processing unit 197 may determine the delay amount based on the output of the phase detector 78 or the smoothing filter 79, and store the frequency and delay amount of the local oscillation signal at this time in the memory. . When the delay amount is 210 degrees, the baseband digital processing unit 197 inverts the sign of the Q phase of the baseband signal.

  As described above, in the present embodiment, the multiphase signal generation circuit 110 selects the delay amount per stage of the delay circuit 76A to be either 150 degrees or 210 degrees, and the multiphase signal is selected. Generate. In the present embodiment, the delay amount of the delay circuit 76A may be either 150 degrees or 210 degrees. In the present embodiment, the delay amount of the delay circuit 76A is selected according to the frequency of the local oscillation signal. In the present embodiment, either delay amount may be selected as long as both the delay amount of 150 degrees and the delay amount of 210 degrees can be realized by the delay circuit 76A.

  Below, the effect of this embodiment is demonstrated with reference to FIG. 11, FIG. FIG. 11 is a diagram for explaining the delay time of the conventional delay circuit, and FIG. 12 is a diagram for explaining the delay time of the delay circuit of this embodiment.

  In this embodiment, the delay time of the delay circuit is the fastest and the slowest, for example, 1.3 times due to variations in the manufacturing process, variations in the power supply voltage supplied to the transmission / reception circuit 100, ambient temperature changes, and the like. Be different.

  Both FIG. 11 and FIG. 12 show the delay time per stage of the delay circuit in the horizontal axis direction, and the variable delay time range of the delay circuit is indicated by the double-ended arrow line segment. In addition, delay times corresponding to 30 degrees, 150 degrees, and 210 degrees of the delay amount when the local oscillation signal frequency input from the synthesizer 130 is 2200 MHz, 2376 MHz, 2552 MHz, 2728 MHz, 2904 MHz, 3080 MHz, 3256 MHz, and 3432 MHz are shown.

  As in the example shown in FIG. 11, the delay time variable range to be satisfied by the conventional delay circuit is 24.3 ps (corresponding to a delay amount of 30 degrees) in both the case where the delay time is the shortest and the case where the delay time is the longest. (When the signal frequency is 3432 MHz) to 37.9 ps (when the signal frequency is 2200 MHz). Therefore, in the conventional delay circuit, including the margin, the variable delay time range is approximately 2.0 times the shortest delay time.

  On the other hand, in the example shown in FIG. 12, the delay time variable range to be satisfied by the delay circuit 76A of this embodiment is narrower than the conventional one because the delay amount is selected from either 150 degrees or 210 degrees. be able to. In the delay circuit 76A of the present embodiment, including a margin, the delay time variable range is about 1.5 times the shortest delay time. This facilitates the realization of the delay circuit 76A.

  Therefore, the transmission / reception circuit 100 according to the present embodiment can perform desired frequency conversion when the frequency of the local oscillation signal changes in a wide range.

  As mentioned above, although this invention has been demonstrated based on each embodiment, this invention is not limited to the requirements shown in the said embodiment. With respect to these points, the gist of the present invention can be changed without departing from the scope of the present invention, and can be appropriately determined according to the application form.

DESCRIPTION OF SYMBOLS 100 Transmission / reception circuit 110,120 Polyphase signal generation circuit 140,150 Mixer circuit 160,190 Smoothing filter 170 Variable gain amplifier 170
180 ADC
195 DAC
197 Baseband digital processor

JP 2007-150663 A

Claims (3)

A synthesizer that outputs a local oscillation signal;
A plurality of delay circuits connected in multiple stages, a first multiphase signal generating means for generating a multiphase local oscillation signal by inputting the local oscillation signal to each of the delay circuits;
A transmission circuit including a first mixer circuit that receives the polyphase signal raw and converts a transmission signal in a baseband to a carrier frequency;
A second multiphase signal generating means for generating a multiphase local oscillation signal by inputting the local oscillation signal;
A receiving circuit including a second mixer circuit that converts the received signal of the carrier frequency into a baseband frequency, and
The delay circuit generates a first delay time and a second delay time, and transmits and receives a delay time selected from the first delay time and the second delay time. circuit. Baseband digital processing means for processing a baseband signal that is a signal of the baseband,
The baseband digital processing means includes
The transmission / reception circuit according to claim 1, wherein when the second delay time is selected, the phase of the baseband signal is switched.   The transmission / reception circuit according to claim 1 or 2, wherein a phase change amount corresponding to the first delay time is 150 degrees and a phase change amount corresponding to the second delay time is 210 degrees.

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