FM stereo broadcast and broadcast data system measurement solutions
With the development of modern technology, FM broadcasting is gradually becoming a standard feature, which is widely deployed in mobile handheld devices such as mobile phones, navigation, and car entertainment systems, and in-vehicle terminal devices. Today's mobile phones and navigation can not only be used to listen to FM radio, many also have FM transmission function, and send stored digital music, navigation reminder sound to nearby ordinary radios, car radios for listening. FM technology is also evolving. In order to transmit stereo music, FM supports the transmission of different voice content through the stereo multiplexing, that is, FM stereo (FM Stereo). In order to transmit fast data information through the FM frequency band, relevant international departments have formulated a series of standard specifications. Currently, there are mainly European Broadcast Data System (RDS) specifications and the US Radio Broadcast Digital System (RBDS) specifications. Through RDS / RBDS technology, FM can transmit text information, such as traffic, weather, radio station information, etc. These information can be displayed on the user interface of the FM terminal device. In order to ensure the reliable operation of FM Stereo and RDS / RBDS systems, how to carry out relevant tests accurately and quickly has become a very critical link in the FM industry chain, and is also a problem faced by many mobile device manufacturers. FM Stereo / RDS system overview FM Stereo is compatible with FM mono radio and supports stereo multi-channel signal transmission. To achieve this goal, the FM stereo multiplexed signal (MPX) transmits the left channel (L) and right channel (R) information (L + R) at the baseband part of 0 ~ 15kHz at the same time, making the mono radio You can also listen to stereo signals. In order to recognize the two signals of L and R, the baseband spectrum of 23 ~ 53kHz is used, and the information of (LR) is transmitted at 38kHz using the carrier suppression amplitude modulation modulation method to provide stereo sound effects. The FM stereo signal also contains a 19kHz pilot signal, which is used to assist the receiver to detect and decode the left and right channel signals. At the receiving end, the (L + R) and (LR) signals are added to recover the L signal, and the (L + R) and (LR) signals are subtracted to recover the R signal. The baseband spectrum of the MPX signal is shown in Figure 1. Figure 1: Baseband spectrum of FM stereo / wireless data broadcasting system. RBS / RBDS signals are transmitted at 57 kHz subcarrier. RDS / RBDS transmits information at a rate of 1.1875 kbps, using BPSK modulation. RDS can send various information such as station name, program type, program content, traffic information and so on. Figure 2 shows the data structure of RDS / RBDS, the largest data unit of which is a group. Each group consists of 4 blocks, each with 26 bits, containing 16 information bits and 10 check bits. The role of the parity bit is error identification, error correction, and data synchronization. Figure 2: RDS baseband coding structure. FM Stereo / RDS system test plan The FM Stereo / RDS test has two main aspects, namely the test for the transmitter and the test for the receiver. Agilent provides corresponding signal analyzers and signal sources for these two tests respectively. 1. Common test parameters of FM Stereo / RDS system FM Stereo / RDS system testing involves the measurement of multiple parameters, including power measurement, signal noise and distortion ratio (SINAD) measurement, harmonic distortion (THD) measurement, RDS BLER (block error rate) measurement, etc. SINAD / DistorTIon: SINAD / DistorTIon is an important parameter to measure audio quality. The definitions of SINAD and DistorTIon are as follows: (E1) Among them, Ptotal is the total signal power, and Punwanted is the sum of the noise signal power and the distortion signal power. The test block diagram of SINAD / DistorTIon is shown in Figure 3. First, the input signal is filtered by an audio filter to remove out-of-band interference to calculate Ptotal, and then the signal is filtered by a notch filter to remove the useful signal (including Mono / Stereo audio signal and carrier signal) to calculate Punwanted. Figure 3: SINAD measurement block diagram. SINAD is not only an important parameter to measure the performance of the transmitter, but also very important to the measurement of the receiver. When making measurements such as receiver sensitivity, adjacent channel suppression, and intermodulation, it is necessary to track the measurement results of SINAD until it is below a certain critical value. THD: THD is used to measure the harmonics in the signal, that is, the harmonic components that are more than the required signal in the measured output signal. THD is caused by the incomplete linearity of the system. It is defined as the ratio of the root-mean-square voltage value of all harmonic components to the fundamental frequency voltage value, usually expressed as a percentage. The calculation formula is as follows, (E2) Where Vn is the rms voltage of the nth harmonic component. RDS BLERTHD: RDS BLER is the ratio of the received data block (26 bits) with uncorrectable bits to the total number of received data blocks. When calculating the RDS BLER, the check word in the RDS code is used to calculate and correct the erroneous data bits. The typical threshold value for RDS testing is usually 5%. We mainly produce Fridge Thermostat, namely Ranco, Sagnomiya style, Pacific style,danfoss .style.robertshaw style,ge style.TAM style,ATEA style,E style,F2000,A2000,711,TIMER,ROOM THERMOSTAT etc. Our products are mainly used in refrigerator, home air-conditioner, car air-conditioner, freezer,watering-trough, water heater and washing machine,oven, fryer etc.96% of our products export.and sell well in Europe, America, Africa ,mid-east and other places worldwide, with VDE,CE, CQC, RoHS and ISO9001 certificates. Fridge Thermostat Fridge Thermostat,Refrigerator Thermostat,Freezer Thermostat,Refrigerator Temperature Control ZHEJIANG ICE LOONG ENVIRONMENTAL SCI-TECH CO.,LTD. , https://www.ice-loong.com
Ranco:K50-P1110 K50-P1125 K50-P1126 K50-P1127 K50-P1179 K50-P1216 K50-P1272 K50-P1346 K54-P1102 VT9(K59-L1102) K59-L3111-002 K59-P3018-003 K60-P1013 etc.
Danfoss:077B0021 077B0033 077B0407 077B1110 077B2671 077B6208 077B6706 etc.F2000,A2000