Handheld FM RDS Signal Generator
Introduction:
In car radio software development, one of the expensive and important instrument is FM
RDS signal generator. Some suppliers like R&S provide instruments with integrated RF and FM
MPX with RDS signal generating capabilities. And other suppliers provide FM modulators and FM
MPX with RDS signal generators separately.These instruments are bulky and occupies lots of
space, often these instrument are stacked in huge racks and fixed at one place in the lab. Thereby
causing lots of inconvinience to software developers during software development.
The objective of this project is to implement a protable, battery powered and low cost FM
RDS signal generator with almost similar capabilities of expensive signal generators from R&S,
Panasonic, Philips etc.
Concept and design:
Figure above shows the block diagram for FM RDS signal genrator. The main blocks are
microcontroller, FM RDS signal generator and the AF generator. A PC interface is added to control
the RDS coder, it can also be used to store RDS programs into the EEPROM, so the instrument
can be used without PC instead the intrument can be controller from panel. The design is mainly
based on NXP's low cost ARM based LPC1100 series microcontroller and the silicon labs Si4721
AM/FM RDS transmitter chip. The purpose of each block is as explained below.
LPC1100 microcontroller:
The LPC11 00 is the world’s first Cortex-M0 based microcontroller series offering users a cost
effective, very easy to use 32-bit MCU which is code and tool compatible with other NXP
ARMbased MCU products.With 32-bit performance combined with multiple power modes and very
low Deep sleep power, the LPC11xx offers industry leading energy efficiency greatly extending
battery life.The LPC11xx sets new benchmarks in performance efficiency with dramatically
improved code density enabling longer battery life and lower system costs.
LPC 1100 controls all the peripherals connected to it. It is the heart of this projects.
Si4721: Broadcast FM Radio Transceiver for Portable Applications
Features
Integrated FM antenna support Excellent real-world performance Only two external components
required Worldwide FM band support (76 to 108 MHz) RDS/RBDS processor (Si4721) Frequency
synthesizer with integrated VCO Adjustable seek parameters Adjustable mono/stereo blend
Adjustable soft mute Programmable transmit output voltage control Audio dynamic range control
Advanced modulation control Analog/digital audio interface Programmable reference clock input
Programmable pre/de-emphasis (50/75 μs) 2-wire and 3-wire control interface Integrated LDO
regulator 2.7 to 5.5 V supply voltage 3x3x0.55 mm 20-pin Pb-free QFN package.
Description
The Si4721 is the first single chip FM radio transceiver. The digital architecture of the Si4721
combines the functionality of the Si470x FM radio receiver with the Si471x FM transmitter, offering
full FM receive and transmit capabilities in a single, ultra-small 3x3x0.55 mm QFN package. The
device offers unmatched integration and performance allowing FM receive and transmit to be
added to any portable device by using a single chip. The Si4721 offers industry leading size,
performance, low power consumption, and ease of use. The Si4721's digital integration reduces
the required external components of traditional offerings, resulting in a solution requiring only an
external inductor and bypass capacitor, and a PCB space of approximately 15 mm2. High yield
manufacturability, unmatched performance, easy design-in, and software programmability are key
advantages of the Si4721.
The Si4721 is the industry's first single-chip integrated FM radio transceiver including both
receive and transmit support for the European Radio Data System (RDS) and the U.S. Radio
Broadcast Data System (RBDS). RDS allows digital information sent from the broadcaster to be
displayed, such as station ID, song name and music category. In Europe, alternate frequency (AF)
information is also provided to automatically change stations in areas where broadcasters use
multiple frequencies. In transmit mode, digital information such as artist name, song title, music
category, and branded messaging can be transmitted and displayed on any RDS/RBDS receiver.
In this project Si4721 is only used as a tranmitter. LPC1100 controls this chip via SPI
interface. The various controls include,
1. RF Frequency (76 to 108 MHz) and level (0 to 105dBuV) setting.
2. AF input type selection (Analog or Digital).
3. RDS group programming.
AF generator XR2206:
The XR-2206 is a monolithic function generator integrated circuit capable of producing high
quality sine, square, triangle, ramp, and pulse waveforms of high-stability and accuracy. The
oscillator frequency can be linearly swept over a 2000:1 frequency range with an external control
voltage, while maintaining low distortion. The frequency sweep is proportional to the current drawn
from pin 7 as shown in figure below.
In this project, LPC1100 controls the current sink through ADC (AD5328), thereby adjusting
the AF frequency input to FM generator. Two XR2206 are used to generate stereo signal (Left and
Right).
AD5328 DAC :
AD5328 is 12 bit buffered output DAC. It's output is used as a control voltage for the
current sink circuit of AF generator thereby controlling the AF input frequency to the FM
generator. This DAC is interfaced to the LPC1100 controller via SPI interafce.
The SW in LPC controller shall control the frequency sweep of AF generator.
PC Interface MAX232:
This product will have a interface to PC via RS232 for controlling various RDS coder
functionalities.as mentioned below,
● Programming RDS groups into the EEPROM.
● Setting TA, PTY, PS names, TMC,Radiotext,AF frequencies, REG, EON TA, and EON PTY etc.
● Selection of Modulation input (Internal or External). And setting of Frequency deviation.
● Setting value for RF frequency and RF level.
● For internal modulation, frequency setting to fixed frequency or for auto sweep from 20Hz to
20kHz. For fixed frquency, both left and right channels can be controlled independently.
EEPROM :
Different RDS groups can be arranged as programs and stored in the EEPROM, so that the
device can be used without PC interface. An EEPROM size of 1MB would be provided to store
RDS programs and other SW specific data.
Display and Keyboard:
Display and Keyboard will be the human machine interface when the is used offline without
PC. The user can use this interface to,
● Set the coder frequency and level.
● Set RDS programms from EEPROM.
● Set RDS data like PI, PS, TA, TP, PTY, AF, REG and Radio text etc.
● Set modulation source to internal or external
● Set modulation frequency and lvel for internal source.
● Set RF frequency and level
● Set Pilot frequency, frequency deviation.
Power Supply
This section of the unit powers all the circuits. It also contains a NiMH battery charger. When
the unit is connected to mainsl power, the circuit supply is taken directly from mains power. The on
board battery gets charged in this case. When unit is not connected to AC mains power, circuits are
powered by the NiMH battery.
Introduction:
In car radio software development, one of the expensive and important instrument is FM
RDS signal generator. Some suppliers like R&S provide instruments with integrated RF and FM
MPX with RDS signal generating capabilities. And other suppliers provide FM modulators and FM
MPX with RDS signal generators separately.These instruments are bulky and occupies lots of
space, often these instrument are stacked in huge racks and fixed at one place in the lab. Thereby
causing lots of inconvinience to software developers during software development.
The objective of this project is to implement a protable, battery powered and low cost FM
RDS signal generator with almost similar capabilities of expensive signal generators from R&S,
Panasonic, Philips etc.
Concept and design:
Figure above shows the block diagram for FM RDS signal genrator. The main blocks are
microcontroller, FM RDS signal generator and the AF generator. A PC interface is added to control
the RDS coder, it can also be used to store RDS programs into the EEPROM, so the instrument
can be used without PC instead the intrument can be controller from panel. The design is mainly
based on NXP's low cost ARM based LPC1100 series microcontroller and the silicon labs Si4721
AM/FM RDS transmitter chip. The purpose of each block is as explained below.
LPC1100 microcontroller:
The LPC11 00 is the world’s first Cortex-M0 based microcontroller series offering users a cost
effective, very easy to use 32-bit MCU which is code and tool compatible with other NXP
ARMbased MCU products.With 32-bit performance combined with multiple power modes and very
low Deep sleep power, the LPC11xx offers industry leading energy efficiency greatly extending
battery life.The LPC11xx sets new benchmarks in performance efficiency with dramatically
improved code density enabling longer battery life and lower system costs.
LPC 1100 controls all the peripherals connected to it. It is the heart of this projects.
Si4721: Broadcast FM Radio Transceiver for Portable Applications
Features
Integrated FM antenna support Excellent real-world performance Only two external components
required Worldwide FM band support (76 to 108 MHz) RDS/RBDS processor (Si4721) Frequency
synthesizer with integrated VCO Adjustable seek parameters Adjustable mono/stereo blend
Adjustable soft mute Programmable transmit output voltage control Audio dynamic range control
Advanced modulation control Analog/digital audio interface Programmable reference clock input
Programmable pre/de-emphasis (50/75 μs) 2-wire and 3-wire control interface Integrated LDO
regulator 2.7 to 5.5 V supply voltage 3x3x0.55 mm 20-pin Pb-free QFN package.
Description
The Si4721 is the first single chip FM radio transceiver. The digital architecture of the Si4721
combines the functionality of the Si470x FM radio receiver with the Si471x FM transmitter, offering
full FM receive and transmit capabilities in a single, ultra-small 3x3x0.55 mm QFN package. The
device offers unmatched integration and performance allowing FM receive and transmit to be
added to any portable device by using a single chip. The Si4721 offers industry leading size,
performance, low power consumption, and ease of use. The Si4721's digital integration reduces
the required external components of traditional offerings, resulting in a solution requiring only an
external inductor and bypass capacitor, and a PCB space of approximately 15 mm2. High yield
manufacturability, unmatched performance, easy design-in, and software programmability are key
advantages of the Si4721.
The Si4721 is the industry's first single-chip integrated FM radio transceiver including both
receive and transmit support for the European Radio Data System (RDS) and the U.S. Radio
Broadcast Data System (RBDS). RDS allows digital information sent from the broadcaster to be
displayed, such as station ID, song name and music category. In Europe, alternate frequency (AF)
information is also provided to automatically change stations in areas where broadcasters use
multiple frequencies. In transmit mode, digital information such as artist name, song title, music
category, and branded messaging can be transmitted and displayed on any RDS/RBDS receiver.
In this project Si4721 is only used as a tranmitter. LPC1100 controls this chip via SPI
interface. The various controls include,
1. RF Frequency (76 to 108 MHz) and level (0 to 105dBuV) setting.
2. AF input type selection (Analog or Digital).
3. RDS group programming.
AF generator XR2206:
The XR-2206 is a monolithic function generator integrated circuit capable of producing high
quality sine, square, triangle, ramp, and pulse waveforms of high-stability and accuracy. The
oscillator frequency can be linearly swept over a 2000:1 frequency range with an external control
voltage, while maintaining low distortion. The frequency sweep is proportional to the current drawn
from pin 7 as shown in figure below.
In this project, LPC1100 controls the current sink through ADC (AD5328), thereby adjusting
the AF frequency input to FM generator. Two XR2206 are used to generate stereo signal (Left and
Right).
AD5328 DAC :
AD5328 is 12 bit buffered output DAC. It's output is used as a control voltage for the
current sink circuit of AF generator thereby controlling the AF input frequency to the FM
generator. This DAC is interfaced to the LPC1100 controller via SPI interafce.
The SW in LPC controller shall control the frequency sweep of AF generator.
PC Interface MAX232:
This product will have a interface to PC via RS232 for controlling various RDS coder
functionalities.as mentioned below,
● Programming RDS groups into the EEPROM.
● Setting TA, PTY, PS names, TMC,Radiotext,AF frequencies, REG, EON TA, and EON PTY etc.
● Selection of Modulation input (Internal or External). And setting of Frequency deviation.
● Setting value for RF frequency and RF level.
● For internal modulation, frequency setting to fixed frequency or for auto sweep from 20Hz to
20kHz. For fixed frquency, both left and right channels can be controlled independently.
EEPROM :
Different RDS groups can be arranged as programs and stored in the EEPROM, so that the
device can be used without PC interface. An EEPROM size of 1MB would be provided to store
RDS programs and other SW specific data.
Display and Keyboard:
Display and Keyboard will be the human machine interface when the is used offline without
PC. The user can use this interface to,
● Set the coder frequency and level.
● Set RDS programms from EEPROM.
● Set RDS data like PI, PS, TA, TP, PTY, AF, REG and Radio text etc.
● Set modulation source to internal or external
● Set modulation frequency and lvel for internal source.
● Set RF frequency and level
● Set Pilot frequency, frequency deviation.
Power Supply
This section of the unit powers all the circuits. It also contains a NiMH battery charger. When
the unit is connected to mainsl power, the circuit supply is taken directly from mains power. The on
board battery gets charged in this case. When unit is not connected to AC mains power, circuits are
powered by the NiMH battery.
nice concepts
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