{"id":1880,"date":"2019-09-09T10:31:43","date_gmt":"2019-09-09T01:31:43","guid":{"rendered":"https:\/\/micronix-jp.com\/?p=1880"},"modified":"2023-03-20T17:12:16","modified_gmt":"2023-03-20T08:12:16","slug":"msg703-vector-signalgenerator_eg","status":"publish","type":"post","link":"https:\/\/micronix-jp.com\/english\/tech\/technology\/msg703-vector-signalgenerator_eg.html","title":{"rendered":"RF signal generator MSG703 \u226aMSG703 as Vector signal generator\u226b"},"content":{"rendered":"

Any phase-modulated signal can be output.<\/p>\n

\n

Overview<\/h2>\n

Currently, the wireless communication is widely used even in consumer electronics products as well as in mobile\nphone and digital terrestrial TV. As the handling amount of data is increasing, the modulation method has\nbeen also improved. The phase modulation is a mainstream now.
\nHow a phase-modulated signal is output from MSG703 will be described in this paper. <\/p>\n<\/section>\n\n

\n

What's a vector signal generator ?<\/h2>\n

The standard signal generator generates only a sine wave signal but the vector signal generator modulates a\nsine wave signal by the phase based on IQ data (I: in-phase component, Q: quadrature-phase component).
\nIn other words, it means the following equation. <\/p>\n

Vector\uff1dIQ modulation<\/p>\n<\/section>\n\n

\n

Basic knowledge of phase modulation<\/h2>\n

In modulation system, there are AM and FM of analog method and ASK (Amplitude Shift Keying) and FSK (Frequency Shift Keying) of digital method. There is also PSK (Phase Shift Keying) of digital method as well.
\nAmong these, PSK is the most popular recently. There are BPSK, QPSK, \u03c0 \/ 4QPSK and so on in PSK system.
\nIn addition, there is QAM including the information of amplitude. <\/p>\n

The radio waves propagating in the air can be considered as single communication channel if the carrier frequency is single. However, some bits can be put on this single communication channel in PSK system.
\nIn other words, it can be considered that some communication channels exist.
\nThe number of bits is one bit in BPSK, 2 bits in QPSK and 6 bits in 64QAM. The increase of the number of bits means that the transmission amount per unit time increases. 64QAM will be six times transmission amount of BPSK. <\/p>\n

Glossary<\/span>\n<\/p>

    \n
  • PSK\uff1aPhase Shift Keying<\/li>\n
  • BPSK\uff1aBinary Phase Shift Keying, 2-level<\/li>\n
  • QPSK\uff1aQuadrature Phase Shift Keying, 4-level<\/li>\n
  • \u03c0\/4QPSK\uff1aThe orthogonal coordinate axes are rotated by 45 degrees each symbol, 4-level<\/li>\n
  • QAM\uff1aQuadrature Amplitude Modulation<\/li>\n
  • 64QAM\uff1aThe information can be sent by 64-level.<\/li>\n<\/ul>\n

    <\/p>\n<\/section>\n\n

    \n

    Explanation of IQ modulator MIQ700<\/h2>\n

    The IQ modulator MIQ700 which is an option of MSG703 series is explained below.<\/p>\n

    Block diagram<\/h3>\n

    \"Block <\/p>\n

    $$\n \\begin{cases}\n Iana\u3001Qana\uff1aAnalog IQ signal \\\\\n Idig\u3001Qdig \uff1aDigital IQ signal\u3000\\\\\n Iusb\u3001Qusb \uff1aUSB data IQ signal \\\\\n 1ST,2ND,3RD LO\uff1a1ST,2ND,3RD local oscillator \\\\ \n \\end{cases} \n $$ <\/p>\n

    Input conditions<\/h3>\n
      \n
    1. Analog input
      \nFull scale voltege\uff1aIQ each \u00b1600mV
      \nInput impedance\uff1a50\u03a9
      \nBaseband bandwidth \uff1a10MHz max\uff08RF bandwidth 20MHz max\uff09 <\/li>\n
    2. Digital input
      \nIQ bit number\uff1aeach 10 bit
      \nIQ data format\uff1a2\u2019s complement
      \nRate\uff1a80MSPS max\uff08bandwidth 10MHz max\uff09\n

      \"Input <\/p>\n<\/li>\n

    3. USB data input
      \nIt's modulated by the data written in the USB memory <\/li>\n<\/ol>\n

      Generation of\u03c0\/4QPSK modulation signal<\/h2>\n

      This section describes how to generate \u03c0\/4QPSK modulation signal used in ETC2.0. Regarding the regulation, refer to ARIB STD-T75.
      \n\uff3b0,\u03c0\/2, \u03c0, \u03c0\/2\uff3dplane is used in QPSK, but the whole of plane shifts \"\u03c0\/4\" each symbol in \u03c0\/4 QPSK.\nIn other words, if [0, \u03c0\/2, \u03c0, -\u03c0\/2] plane is used at a certain symbol, [\u03c0\/4,3\u03c0\/4, -3\u03c0\/ 4, -\u03c0\/ 4] plane is used at the next symbol. The amount of both informations of QPSK and \u03c0\/4QPSK is 2 bit (four levels), but the output amplifier will be easy to design because the transition region of data in \u03c0\/4 QPSK does not pass through zero volt as shown in the constellation figure below. <\/p>\n

      \"4QPSK <\/p>\n

      Generation of input signal to IQ modulator<\/h3>\n

      First, the IQ signal, which is supplied to IQ modulator MIQ700, should be generated.
      \nThis time, how to generate IQ signal will be described based on ARIB STD-T75 (DSRC standard) which is used\nin ETC2.0.
      \nThe circuit of block diagram described in next section can be easily realized by using FPGA (field programmable\ngate array). Analog input [Iana, Qana] or digital input [Idig, Qdig] is input to IQ modulator MIQ700.
      \nThen, \u03c0\/4QPSK signal can be output from RF OUT connector of MSG703. <\/p>\n

      Block diagram<\/h3>\n

      \"Block <\/p>\n

        \n
      • TXDATA
        \nSerial raw data. 4.096Mbps. <\/li>\n
      • S\/P conversion
        \nSerial \/ parallel conversion. Serial raw data 2 bits (I and Q) is equivalent to one symbol.<\/li>\n
      • Absolute phase address table
        \nThe phase \u0394 \u03a6 makes correspond to 3 bits of absolute phase address so that the calculation of differential\nencoding may be easy.<\/li>\n
      • Differential encoding
        \nThe current phase is added to the previous phase. The differential encoding regulation is defined as shown\nin the table below in ARIB STD-T75.\n