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

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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

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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

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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

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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.

1.1Convenience 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

Table 1).

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

Table 1.	Permissible values for unwanted emission intensity
	Frequency band	Spurious emission strength (average power)	Reference bandwidth

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		-55 dBm	100 kHz
(except for \|f-fc\| ≤ (200+100xn) kHz)		-55 dBm	100 kHz
(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

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An overview of ARIB STD-T108 regulation				AN4133

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

	Frequency band		Limit on secondary radiated	Reference bandwidth
	Frequency band		emissions, etc. (antenna input)	Reference bandwidth
			emissions, etc. (antenna input)

	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

1.2Low-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.

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

Table 3).

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

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AN4133			An overview of ARIB STD-T108 regulation

	Table 3.	Permissible values for unwanted emission intensity

		Frequency band	Spurious emission	Reference bandwidth
		Frequency band	strength (average power)	Reference bandwidth

	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		-36 dBm	100 kHz
	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

Table 4.	Limit on secondary radiated emissions, etc. at receiver
Frequency band		Limit on secondary radiated	Reference bandwidth
Frequency band		emissions, etc. (antenna input)	Reference bandwidth
		emissions, etc. (antenna input)

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

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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

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AN4133	Application circuit

Figure 2. SPIRIT1 application daughterboard plugged into the motherboard

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Figure 3.

Daughterboard schematic

AN4133

3V3

VCC_RF

SPIRIT_DUMMY2

3V3

2 4 6 8 10

C20

C21

C_1U_0603_X7R_K_6V3

C_100p_0402_C0G

R12

HEADER 5X2

R_TBD_0402

1 3 5 7 9

DUMMY3

SDn

R13

R_TBD_0402

DUMMY3

C22

C_330p_0402_C0G

C_100n_0402_X7R

SPIRIT_DUMMY1

GPIO3

GPIO2

GPIO1

GPIO0

GPIO 1

GPIO 2

GPIO 3

VREG

VBAT1

SDn

Doc

GPIO_0

2 4 6 8 10

SDO

SMPS1

L_10U_0805

L_TBD_0402

C11

C12

SDI

SMPS2

C13

HEADER 5X2

C_1U_0603_X7R_K_6V3

C_100n_0402_X7R

C_TBD_0402_X7R

SCLK

023362

1 3 5 7 9

CSn

REXT

VBAT2

L_TBD_0402_50M

XOUT

GND

SDO

XIN

RXP

RXN

C14

C_TBD_0402_C0G

SDI

SPIRIT1_2

SCLK

Rev

CSn

L_TBD_0402

NX3225GA-xxMHz (XTAL)

L3 L_TBD_0402

RF_IN/OUT

XTAL

C15

L_TBD_0402

C_TBD_0402_C0G

C10

C_TBD_0402_C0G

C_12P_0402_C0G_J_50

C_10P_0402_C0G_J_50

L_TBD_0402

C19

C_TBD_0402_C0G

B0=169MHz

B3=868MHz

R_0R0_0402

Application

L_TBD_0402

B1=315MHz

R10

Mount

B3=915MHz

resistor

R_0R0_0402

relative to

L_TBD_0402

used band

C_TBD_0402_C0G

B2=433MHz

R11

B3=920MHz

R_0R0_0402

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circuit

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.

3.1Adjacent 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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