ST AN4133 Application note

AN4133

Application note

Using the SPIRIT1 transceiver under ARIB STD-T108 in the

920 MHz band

By Placido De Vita

Introduction

SPIRIT1 is a very low power RF transceiver, intended for RF wireless applications in the sub-1 GHz band. It is designed to operate both in the license-free ISM and SRD frequency bands at 169, 315, 433, 868, 915 and 920 MHz.

The Japanese Association of Radio Industries and Businesses (ARIB) was established in response to several trends such as the growing internationalization of telecommunications, the convergence of telecommunications and broadcasting and the need for promotion of radio-related industries. The ARIB organism defines the basic technical requirements for standard specifications of radio equipment.

This application note outlines the expected performance when using the Spirit1 under ARIB STD-T108 (see References on page 33) in the 920 MHz band. For details on the regulatory limits in the 920 MHz frequency band, please refer to the ARIB STD-T108 regulation in

References on page 33.

These can be downloaded from www.arib.or.jp/english/index.html.

July 2012 Doc ID 023362 Rev 1 1/35

www.st.com

Contents AN4133

Contents

1 An overview of ARIB STD-T108 regulation . . . . . . . . . . . . . . . . . . . . . . . 5

1.1 Convenience radio stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

1.2 Low-power radio stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2 Application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

3 Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

3.1 Adjacent channel leakage power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

4 Permissible values for unwanted emission intensity . . . . . . . . . . . . . 20

5 Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

5.1 Limit on secondary radiated emission . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

6 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

7 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

2/35 Doc ID 023362 Rev 1

AN4133 List of tables

List of tables

Table 1. Permissible values for unwanted emission intensity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Table 2. Limit on secondary radiated emissions, etc. at receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Table 3. Permissible values for unwanted emission intensity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Table 4. Limit on secondary radiated emissions, etc. at receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Table 5. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Doc ID 023362 Rev 1 3/35

List of figures AN4133

List of figures

Figure 1. SPIRIT1 application daughterboard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Figure 2. SPIRIT1 application daughterboard plugged into the motherboard . . . . . . . . . . . . . . . . . . . 9

Figure 3. Daughterboard schematic. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Figure 4. Convenience radio station channel mask of a radio channel whose frequency is

from 920.5 MHz to 922.3 MHz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Figure 5. Convenience radio station channel mask of a radio channel at 922 MHz . . . . . . . . . . . . . 13

Figure 6. Convenience radio station channel mask of a radio channel whose frequency is

from 922.3 MHz to 923.5 MHz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Figure 7. Convenience radio station channel mask of a radio channel at 923 MHz . . . . . . . . . . . . . 14

Figure 8. Low-power radio station channel mask of a radio channel whose frequency is

from 915.9 MHz to 916.9 MHz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Figure 9. Low-power radio station channel mask of a radio channel at 916.5 MHz. . . . . . . . . . . . . . 15

Figure 10. Low-power radio station channel mask of a radio channel whose frequency is

from 920.5 MHz to 922.3 MHz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Figure 11. Low-power radio station channel mask of a radio channel at 921.5 MHz . . . . . . . . . . . . . 16

Figure 12. Low-power radio station channel mask of a radio channel whose frequency is

from 922.3 MHz to 928.1 MHz (antenna power is 1 mW or less)l . . . . . . . . . . . . . . . . . . . 17

Figure 13. Low-power radio station channel mask of a radio channel at 928 MHz . . . . . . . . . . . . . . . 17

Figure 14. Low-power radio station channel mask of a radio channel whose frequency is

from 922.3 MHz to 928.1 MHz (antenna power is more than 1 mW and 20 mW or less). . 18

Figure 15. Low-power radio station channel mask of a radio channel at 925 MHz . . . . . . . . . . . . . . . 18

Figure 16. Low-power radio station channel mask of a radio channel whose frequency is

from 928.1 MHz to 929.7 MHz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Figure 17. Low-power radio station channel mask of a radio channel at 929 MHz . . . . . . . . . . . . . . . 19

Figure 18. Convenience radio station emission in the 10 - 710 MHz bandwidth . . . . . . . . . . . . . . . . . 20

Figure 19. Convenience radio station emission in the 710 - 900 MHz bandwidth . . . . . . . . . . . . . . . . 21

Figure 20. Convenience radio station emission in the 900 - 915 MHz bandwidth . . . . . . . . . . . . . . . . 21

Figure 21. Convenience radio station emission in the 915 - 920.3 MHz bandwidth . . . . . . . . . . . . . . 22

Figure 22. Convenience radio station emission in the 920.3 - 924.3 MHz bandwidth . . . . . . . . . . . . . 22

Figure 23. Convenience radio station emission in the 924.3 - 930 MHz bandwidth . . . . . . . . . . . . . . 23

Figure 24. Convenience radio station emission in the 930 - 1000 MHz bandwidth . . . . . . . . . . . . . . . 23

Figure 25. Convenience radio station emission in the 1 - 1.215 GHz bandwidth. . . . . . . . . . . . . . . . . 24

Figure 26. Convenience radio station emission in the 1.215 - 6 Hz bandwidth . . . . . . . . . . . . . . . . . . 24

Figure 27. Low-power radio station emission in the 10 - 710 MHz bandwidth. . . . . . . . . . . . . . . . . . . 25

Figure 28. Low-power radio station emission in the 710 - 900 MHz bandwidth. . . . . . . . . . . . . . . . . . 25

Figure 29. Low-power radio station emission in the 900 - 915 MHz bandwidth. . . . . . . . . . . . . . . . . . 26

Figure 30. Low-power radio station emission in the 915 - 930 MHz bandwidth. . . . . . . . . . . . . . . . . . 26

Figure 31. Low-power radio station emission in the 930 - 1000 MHz bandwidth. . . . . . . . . . . . . . . . . 27

Figure 32. Low-power radio station emission in the 1 - 1.215 GHz bandwidth . . . . . . . . . . . . . . . . . . 27

Figure 33. Low-power radio station emission in the 1.215 - 6 GHz bandwidth . . . . . . . . . . . . . . . . . . 28

Figure 34. Receiver radiated emission in the 10 - 710 MHz bandwidth. . . . . . . . . . . . . . . . . . . . . . . . 29

Figure 35. Receiver radiated emission in the 710 - 900 MHz bandwidth. . . . . . . . . . . . . . . . . . . . . . . 30

Figure 36. Receiver radiated emission in the 900 - 915 MHz bandwidth. . . . . . . . . . . . . . . . . . . . . . . 30

Figure 37. Receiver radiated emission in the 915 - 930 MHz bandwidth. . . . . . . . . . . . . . . . . . . . . . . 31

Figure 38. Receiver radiated emission in the 930 - 1000 MHz bandwidth. . . . . . . . . . . . . . . . . . . . . . 31

Figure 39. Receiver radiated emission in the 1 - 6 GHz bandwidth. . . . . . . . . . . . . . . . . . . . . . . . . . . 32

4/35 Doc ID 023362 Rev 1

AN4133 An overview of ARIB STD-T108 regulation

1 An overview of ARIB STD-T108 regulation

Radio equipment defined in this standard utilizes 915 to 930 MHz bandwidth. The ARIB

STD-T108 defines two different types of possible categories of application:

1. Convenience radio stations

2. Low-power radio stations

A short description of the two different categories is given in the following sections. The

main difference concerns the output power and band frequency used.

1.1 Convenience radio stations

Devices that operate in convenience radio stations will work in using either a simplex,

duplex, or semi-duplex broadcast method. The contents of communications are primarily the

signals for telemetry, telecontrol and data transmission systems. The operating frequency

band is between 920.5 MHz and 923.5 MHz. The maximum permitted antenna power is

250 mW (+24 dBm on a 50 ohm load, +27 dBm EIRP considering an antenna of 3 dBi gain).

A radio channel consists of up to 5 consecutive unit radio channels which are defined such

that their center frequency is located from 920.6 MHz to 923.4 MHz with 200 kHz separation

and a bandwidth of 200 kHz. There aren't specific requirements for the modulation method,

while the permissible value for occupied bandwidth is (200 x n) kHz or less, where n is the

number of unit radio channels constituting the entire radio channel and is an integer from 1

to 5.

An adjacent channel leakage power is permitted: two different channel masks are defined,

one for systems that work in the 920.5 MHz to 922.3 MHz band and a second one for the

systems that work in the 922.3 to 923.5 MHz band. For the two different masks refer to the

figures 3-1 and 3-2 of the ARIB STD-T108 regulation cited in References on page 33.

For the transmitter a permissible value for unwanted emission intensity is defined (see

Ta bl e 1 ).

For the receiver a limit for the secondary radiated emissions is defined (see Tab l e 2).

Table 1. Permissible values for unwanted emission intensity

f <= 710 MHz -36 dBm 100 kHz

710 MHz < f ≤ 900 MHz -55 dBm 1 MHz

900 MHz < f ≤ 915 MHz -55 dBm 100 kHz

915 MHz < f ≤ 920.3 MHz -36 dBm 100 kHz

920.3 MHz < f ≤ 924.3 MHz (except for |f-fc| ≤ (200+100xn) kHz)

924.3 MHz < f ≤ 930 MHz -36 dBm 100 kHz

930 MHz < f ≤ 1000 MHz -55 dBm 100 kHz

1000 MHz < f ≤ 1215 MHz -45 dBm 1 MHz

1215 MHz < f -30 dBm 1 MHz

Frequency band Spurious emission strength (average power) Reference bandwidth

-55 dBm 100 kHz

Doc ID 023362 Rev 1 5/35

An overview of ARIB STD-T108 regulation AN4133

Table 2. Limit on secondary radiated emissions, etc. at receiver

Frequency band

f ≤ 710 MHz -54 dBm 100 kHz

710 MHz < f ≤ 900 MHz -55 dBm 1 MHz

900 MHz < f ≤ 915 MHz -55 dBm 100 kHz

915 MHz < f ≤ 930 MHz -54 dBm 100 kHz

930 MHz < f ≤ 1000 MHz -55 dBm 100 kHz

1000 MHz < f -47 dBm 1 MHz

Limit on secondary radiated

emissions, etc. (antenna input)

1.2 Low-power radio stations

Low-power radio stations differ from convenience radio stations in output power and usable

frequency band.

Regarding the output power, two different values are permitted as follows.

● An output power of 1 mW (0 dBm on a 50 ohm load, +3 dBm EIRP considering an

antenna of 3 dBi gain) is permitted in the band greater than or equal to 915.9 MHz to less than or equal to 916.9 MHz , and greater than or equal to 920.5 MHz and less than or equal to 929.7 MHz.

● An output power of 20 mW (+13 dBm on a 50 ohm load, +16 dBm EIRP considering an

antenna of 3 dBi gain) is permitted in the band greater than or equal to 920.5 MHz to less than or equal to 928.1 MHz.

Reference bandwidth

As for convenience radio stations, an entire radio channel consists of up to 5 consecutive

unit radio channels which are defined such that their center frequency is located from 916.0

MHz to 916.8 MHz and from 920.6 MHz to 928.0 MHz with 200 kHz separation and a

bandwidth of 200 kHz, or which are defined such that their center frequency is located from

928.15 MHz to 929.65 MHz with 100 kHz separation and a bandwidth of 100 kHz. There

aren't specific requirements for the modulation method, while the permissible value for the

occupied bandwidth is (200 x n) kHz or less, where n is the number of unit radio channels

constituting the entire radio channel and is an integer from 1 to 5. In the case that the center

frequency is from 928.15 MHz to 929.65 MHz, it shall be (100 x n) kHz or less.

An adjacent channel leakage power is permitted: five different channel masks are defined,

functions of the usable bandwidth and of the output power. For the five different masks refer

to the figures 3-1 to 3-5 of the ARIB STD-T108 regulation, see References on page 33.

For the transmitter a permissible value for unwanted emission intensity is defined (see

Ta bl e 3 ).

For the receiver a limit for the secondary radiated emissions is defined (see Tab l e 4).

6/35 Doc ID 023362 Rev 1

AN4133 An overview of ARIB STD-T108 regulation

Table 3. Permissible values for unwanted emission intensity

Frequency band

f ≤ 710 MHz -36 dBm 100 kHz

710 MHz < f ≤ 900 MHz -55 dBm 1 MHz

900 MHz < f ≤ 915 MHz -55 dBm 100 kHz

915 MHz < f ≤ 930 MHz (Except for |f-fc| ≤ (200+100xn) kHz if

bandwidth of unit radio channel is 200 kHz, except for |f-fc| <= (100+50xn) kHz if the bandwidth of unit radio channel is 100 kHz.

Except for |f-fc| <= (100+100xn) kHz if frequency band is 915.9 MHz ≤ f ≤ 916.9 MHz and 920.5 MHz ≤ f ≤ 922.3 MHz.

Where n is a number of unit radio channels constituting the radio channel and is an integer from 1 to 5).

930 MHz < f ≤ 1000 MHz -55 dBm 100 kHz

1000 MHz < f ≤ 1215 MHz -45 dBm 1 MHz

1215 MHz < f -30 dBm 1 MHz

Spurious emission

strength (average power)

-36 dBm 100 kHz

Reference bandwidth

Table 4. Limit on secondary radiated emissions, etc. at receiver

Frequency band

f ≤ 710 MHz -54 dBm 100 kHz

710 MHz < f ≤ 900 MHz -55 dBm 1 MHz

900 MHz < f ≤ 915 MHz -55 dBm 100 kHz

915 MHz < f ≤ 930 MHz -54 dBm 100 kHz

930 MHz < f ≤ 1000 MHz -55 dBm 100 kHz

1000 MHz < f -47 dBm 1 MHz

Limit on secondary radiated

emissions, etc. (antenna input)

Reference bandwidth

Doc ID 023362 Rev 1 7/35

Application circuit AN4133

2 Application circuit

Figure 1 shows the SPIRIT1 application board. The application is composed of two boards:

a daughterboard and a motherboard. The daughterboard holds the SPIRIT1 with the circuits

necessary for operation. In order to function properly the daughterboard has to be plugged

into the motherboard (see Figure 2) using two header 5x2 connectors (J6 and J7).

The motherboard is provided with an STM32L152VBT6 microcontroller to correctly program

the transceiver. The microcontroller is programmed with firmware developed for the SPIRIT1

application. A graphical user interface (GUI) has been developed to correctly program the

SPIRIT1.

The daughterboard is provided with a 52 MHz crystal to provide the correct oscillator to the

SPIRIT1.

The SPIRIT1 has an internal SMPS that drastically reduces power consumption making the

SPIRIT1 the best in class for the application in this bandwidth. The SMPS is fed from the

battery (1.8 V to 3.6 V) and provides a programmable voltage (1.4 V usually) to the device.

An SMA connector is present to connect the board to the antenna or to the instrumentation

to verify the correct functionality and verify the ETSI standard request.

A few passive components (inductors and capacitors) are used for matching/filtering of the

power amplifier (PA) and balun network for the receiver.

To reduce the application cost the SPIRIT1 is designed to work without an external antenna

switch. This daughterboard is designed to show the functionality of the SPIRIT1 in this

condition. Of course an application with antenna switch can be implemented, but this isn't

described in this document.

Figure 1. SPIRIT1 application daughterboard

8/35 Doc ID 023362 Rev 1

AN4133 Application circuit

Figure 2. SPIRIT1 application daughterboard plugged into the motherboard

Doc ID 023362 Rev 1 9/35

Figure 3. Daughterboard schematic

3V3

SPIRIT _DUMMY2

VCC_RF

AN4133 Application circuit

Doc ID 023362 Rev 1 10/35

246810

13579

246810

13579

R_0R0_0402

DUMMY3

SPIRIT _DUMMY1

J7 HEADER 5X2

HEADER 5X2

SCLK

B0=169MHz

B1=315MHz

B2=433MHz

J6 HEADER 5X2

HEADER 5X2

GPIO3 GPIO2 GPIO1

GPIO0

SDO SDI

CSn

SDn

C22

C_330p_0402_C0G

SPIRIT 1_2

NX3225GA-xxMHz (XTAL)

C_12P_0402_C0G_J_50

R10

R11

R_0R0_0402

B3=868MHz

B3=915MHz

B3=920MHz

C20

C20 C_1U_0603_X7R_K_6V3

C_1U_0603_X7R_K_6V3

C_100n_0402_X7R

GPIO_0

SDO

SDI

SCLK

CSn

GPIO_318GPIO_219GPIO_1

VBAT2

XOUT6XIN7RXP9RXN

XTALY1XTAL

Mount resistor relative to used band

C21

C21 C_100p_0402_C0G

C_100p_0402_C0G

VREG

VBAT1

SDn

SMPS1

SMPS2

REXT

GND

C10

C_10P_0402_C0G_J_50

L_10U_0805

C19

C_TBD_0402_C0G

3V3

R12

R12 R_TBD_0402

L0 L_TBD_0402_50M

L_TBD_0402_50M

C_TBD_0402_C0G

L_TBD_0402

C_TBD_0402_C0G

R_TBD_0402

R13

R13 R_TBD_0402

R_TBD_0402

C11

C11 C_1U_0603_X7R_ K_6V3

C_1U_0603_X7R_ K_6V3

L_TBD_0402

C_TBD_0402_C0G

C12

C12 C_100n_0402_X7R

C_100n_0402_X7R

C14 C_TBD_0402_C0GC14 C_TBD_0402_C0G

L_TBD_0402

L3 L_TBD_0402L3 L_TBD_0402

C_TBD_0402_C0G

C13

C13 C_TBD_0402_X7R

C_TBD_0402_X7R

C_TBD_0402_C0G

RF_IN/OUT

DUMMY3

L_TBD_0402

C15

C_TBD_0402_C0G

L5 L_TBD_0402L5 L_TBD_0402

C6 C_TBD_0402_C0GC6 C_TBD_0402_C0G

L_TBD_0402

AN4133 Transmitter

3 Transmitter

All the measurements given are measured under the following conditions: Tc = 25 °C, Vdd =

3.0 V, f = 922 MHz (middle frequency of the bandwidth used), unless otherwise specified.

The maximum output power of the SPIRIT1 in this band is 10 dBm, so all the measurements

for the convenience radio stations and low-power radio stations with +24 dBm or +13 dBm

output power will be performed at +10 dBm. Low-power radio stations with output power of 0

dBm will be performed with the correct output power.

A radio channel consists of up to 5 consecutive unit radio channels which are defined such

that their center frequency is located from 920.6 MHz to 923.4 MHz with 200 kHz separation

and a bandwidth of 200 kHz. SPIRIT1 fully supports the center frequency, separation and

bandwidth requirements. No measurement in that sense will be done.

There aren't specific requirements for the modulation method, while the permissible value

for the occupied bandwidth is (200 x n) kHz or less, where n is the number of unit radio

channels constituting the entire radio channel and is an integer from 1 to 5. The

measurement in this case will be done with a GFSK (BT = 0.5) modulation with 100 kbps

data rate, 50 kHz frequency deviation. Different combinations of modulation, data rate and

frequency deviation creates signals that have a bandwidth lower than 200 kHz: a specific

check has to be done for each case.

There are no specific requirements in the standard about setting the detector, resolution

bandwidth (RBW) or video bandwidth (VBW) of the spectrum analyzer. The detector will be

set to peak, the resolution and video bandwidths will be set sufficiently large to ensure the

correctness of the measurement, and the display will be set to peak hold.

3.1 Adjacent channel leakage power

The adjacent channel leakage power is defined as the amount of the modulated RF signal

power which falls within a given adjacent channel. This power is the sum of the mean power

produced by the modulation, hum and noise of the transmitter.

Different masks are defined for the two types of operating modes. For the convenience radio

stations the masks given in Figure 4 and 6 are defined. The first one defines the channel

mask of a radio channel whose frequency is from 920.5 MHz to 922.3 MHz. The second one

defines the channel mask of a radio channel whose frequency is from 922.3 MHz to 923.5

MHz. The max output power permitted for the convenience radio station is 250 mW (+24

dBm), the SPIRIT1 doesn't support this output power, so the mask compliance is verified

with an output power of 10 dBm. An external PA should be used to reach the maximum

output power.

Figure 5 and 7 show the compliance measurement with the two masks and that the SPIRIT1

complies. If an external power amplifier is used to burst the output power to +24 dBm a

verification of the channel masks has to be done. If the mask requirements aren't met, a

reduction of the data rate and/or frequency deviation is necessary.

For the low-power radio stations the masks printed in Figure 8, 10, 12, 14, and 16 are

defined.

Figure 8 defines the channel mask of a radio channel whose frequency is from 915.9 MHz

to 916.9 MHz. In this case the maximum permitted output power is 1 mW (0 dBm), so the

measurement is performed with this output power level. Figure 9 shows the SPIRIT1

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