Learning Time Mobile Phone RF Cellular (part 1)

Learning Time > Mobile Phone RF Cellular part 1 <

Radio Frequency ( RF ) technology has been applied into many device in our life including our mobile phone, The same Radio Frequency that has been developed from long time ago, Radio frequency ( RF ) is the oscillation rate of an alternating electric currrent / voltage or of a magnetic, electric or electromagentic field or mechanical system in the frequency range from 20 KHz to 300 Ghz. This roughly between the audio frencuencies and the lower limit infrared frequencies. These are the frequencies at which energy from an oscillating current can radiate off a conductor into space as radio waves. Different sources specify different upper and lower bounds for the frequency range. Energy from RF currents in conductors can radiate into space as electromagnetic waves (radio waves). This is the basic of radio technology. The radio spectrum of frequencies is divided into bands with conventional names designated by the International Telecommunications Union ( ITU ) :

Mobile networks based on different standards may use the same frequency range; for example, AMPS, D-AMPS, N-AMPS and IS-95 many of country use the 800 MHz frequency band. Moreover, people can find both AMPS and IS-95 networks in use on the same frequency in the same area that do not interfere with each other. This is achieved by the use of different channels to carry data. The actual frequency used by a particular phone can vary from place to place, depending on the settings of the carrier's base station. Cellular frequencies are the sets of frequency ranges within the Ultra High Frequency ( UHF ) band that have been assigned for cellular-compatible mobile devices, such as mobile phones, to connect to cellular networks. Most mobile networks worldwide use portions of the radio frequency spectrum, allocated to the mobile service, for the transmission and reception of their signals. Radio frequencies used for cellular networks differ in ITU Regions (Americas, Europe, Africa and Asia). The GSM standard, which appeared in Europe to replace NMT-450 and other standards, initially used the 850 Mhz ( Known as GSM ) 900 MHz ( known as EGSM ) band and 1,800 MHZ ( known as DCS ) in the beginning, besides The AMPS standard that used the cellular band ( 800 MHZ ) was replaced by IS-95 or CDMA and IS-136 or D-AMPS as Digital AMPS / TDMA. Many GSM phones support three bands that permited to use in many cpunties ( 900/1,800/1,900 MHz or 850/1,800/1,900 MHz) or four bands ( 850/900/1,800/1,900 MHz ) and more, for their mobilephone usually referred to as tri-band, quad-band phones and multiband phones or world phones with this such a phone people can travel internationally and use the same mobilephone.

Modern mobile phone networks use cells because radio frequencies are a limited, shared resource. Cell-sites and handsets change frequency under computer control and use low power transmitters so that the usually limited number of radio frequencies can be simultaneously used by many callers with less interference. A cellular network is used by the mobile phone operator to achieve both coverage and capacity for their subscribers. Large geographic areas are split into smaller cells to avoid line-of-sight signal loss and to support a large number of active phones in that area. All of the cell sites are connected to telephone exchanges (or switches), which in turn connect to the public telephone network. In cities, each cell site may have a range of up to approximately 0.80 km, while in rural areas, the range could be as much as 8.0 km. It is possible that in clear open areas, a user may receive signals from a cell site 25 miles (40 km) away. There are a number of different digital cellular technologies, including: Global System for Mobile Communications (GSM), General Packet Radio Service (GPRS), cdmaOne, CDMA2000, Evolution-Data Optimized (EV-DO), Enhanced Data Rates for GSM Evolution (EDGE), Universal Mobile Telecommunications System (UMTS), Digital Enhanced Cordless Telecommunications (DECT), Digital AMPS (IS-136/TDMA), Integrated Digital Enhanced Network (iDEN) and Long term Evolution ( LTE ) based on FDD or TDD, The transition from existing analog to the digital standard followed a very different path in Europe and the US.[19] As a consequence, multiple digital standards surfaced in the US, while Europe and many countries converged towards the GSM standard. The effect of frequency on cell coverage means that different frequencies serve better for different uses, each frequency provide different cell radius, cell area and relative cell count

Any phone connects to the network via an RBS (Radio Base Station) at a corner of the corresponding cell which in turn connects to the Mobile switching center (MSC). The MSC provides a connection to the public switched telephone network (PSTN). The link from a phone to the RBS is called an uplink while the other way is termed downlink. Radio channels effectively use the transmission medium through the use of the following

multiplexing and access schemes: frequency division multiple access (FDMA), time division multiple access (TDMA), code division multiple access (CDMA), and space division multiple access (SDMA). As the phone user moves from one cell area to another cell while a call is in progress, the mobile station will search for a new channel to attach to in order not to drop the call. Once a new channel is found, the network will command the mobile unit to switch to the new channel and at the same time switch the call onto the new channel, this is called Cellular handover.

GSM ( Global System for mobile communication )
GSM is the second generation ( 2G ) of cellular network system using multyplexing Time Division Multiple access (TDMA) technology, usually use Very Large Scale Integration (VLSI) Frequency Range / Band : 850 Mhz ( GSM ),, 900 Mhz ( EGSM ), 1800 Mhz (DCS) and 1900 MHZ (PCS) , the Group / Band of Frequency range for 2G mention below :
  1. 850, TX: 824-849 Mhz, RX: 869-894 Mhz ( GSM ) > Lowband ( LB ) Band 5
  2. 900, TX: 870-915 Mhz, RX: 935-960 Mhz ( E-GSM ) > Lowband LB ( LB ) Band 8
  3. 1800, TX: 1710-1785 Mhz, RX: 1805-1880 Mhz (DCS) > Highband ( HB ) Band 3
  4. 1900, TX: 1850-1910 Mhz, RX: 1930-1990 Mhz (PCS) > Highband ( HB ) Band 2
This GSM protocol also have advanced data packet service technology inside of it :
  • High Speed Circuit Switch Data (HSCSD) : 64 Kbps - 100 Kbps ( long time ago )
  • General Packet Radio Service ( GPRS ) : 171.2 kbps
  • Enhanced Data rates for GSM Evolution (EDGE) : 384 kbps

UMTS (Universal Mobile Telecommunications System)
UMTS is the third generation (3G ) cellular technology that establishes by ITU. Use the new radio spectrum to increase the number of subscribers. This is in line with the industry's future needs for data service requests for the future. The UMTS system uses the same core as GPRS but uses a new radio interface. Core network that allows switching, routing, transport, and database functions for user traffic. The Core network consists of automatic circuit systems, such as MSC, VLR, and MSC Gateway (GMSC). The new radio network system at UMTS is called the UTRAN (UMTS Terrestrial Radio Access Network) and is connected to the Core network (CN) by GPRS via the IU ( UTRAN ) interface, which connects the Radio Control Network (RNC) and the Core Network. The new Radio network is WCDMA (Wide - Code Division Multiply Access) the Wide band CDMA technology was chosen as a liaison UTRAN in the air. UMTS-WCDMA is a Direct Sequence CDMA system where user data is reproduced by random bits to obtain a random code in the style of WCDMA. In UMTS, in addition to channeling, codes are used for data matching and contention. WCDMA is a third generation (3G) technology based on packet service using the standard Direct Sequence Spread Spectrum and RF modulation used is QPSK when uplink or downlink. The bandwidth standard used is 5 Mhz which can be increased up to 10 Mhz, 15 Mhz and 20 Mhz. While mobility support can be served up to 120 km / hour. HSDPA ( High-Speed Downlink Packet Access ) Implemented in UMTS ( 3G ) This mobile phone protocol sometimes called as 3.5G technology. The first phase HSDPA has a capacity of 4.1 Mbps, then next phase with acapacity of 11 Mbps and maximum peak data rate downlink capacity up to 14 Mbit/s. HSDPA provides an evolutionary path for the Universal Mobile Telecommunications System ( UMTS ) network that allows for greater data capacity usage (up to 14.4 Mbit / sec downward direction). designed to increase data transfer speeds 5x higher. HSDPA defines a new WCDMA channel, the high-speed downlink shared channel ( HS-DSCH ), which operates differently from the existing W-CDMA channel. Until now the use of HSDPA technology is only in the downstream direction of communication to mobile phones. In a static position this technology can download data up to 3.7 Mbps. and In a mobile state, someone who is driving on a toll road with a speed of 100 km / h, can access the internet with a speed of 1.2 Mbps, Range of data speed (DL) in UMTS up to 2.4 Mbps, Range of data speed ( DL ) HSDPA up to 4.8 Mbps. 2100 Mhz ( Band 1 / IMT ) is the Most General Band that use for 3G

LTE ( Long Term Evolution )
This technology known as Forth Generation ( 4G ) in the celluler networks technology, 3GPP Long Term Evolution is a high-level wireless data access communication standard based on GSM / EDGE and UMTS / HSPA networks. The network interface is incompatible with 2G and 3G networks, so it must be operated through a separate wireless spectrum. This technology is capable of downloading up to 300 Mbps speeds and 75 Mbps uploads. 3GPP Long Term Evolution, or better known as LTE and marketed as 4G LTE is a wireless communication standard based on GSM / EDGE and UMTS /HSDPA networks for high speed data access using cellular phones or other mobile devices. LTE uses Orthogonal Frequency Division Mutiplexing (OFDM) which transmits data through many radio spectrum operators, each of which is 180 kHz. OFDM transmits by dividing the data stream into many slower streams that are transmitted simultaneously. By using OFDM minimize the possibility of multi path effects. Increase the overall transmission speed, the transmission channel used by LTE is enlarged by increasing the quantity of radio spectrum operators without changing the radio spectrum channel parameters themselves.

as Mobilphone Technician you already know, When mobilephone connected to some cellular provider and said EDGE or maybe GPRS in the Signal Bar, it still connected to the networks use same 2G or GSM protocol, not the 3G or 4G when you trace this line on the schematics you only need to looking for "2G" words, or maybe "GSM" words or some other use LB and HB to mention the electronics circuit of 2G networks on their mobilephone schematics. On the other side 3G or 4G will use prefix UMTS / WCDMA and LTE for 4G, or some other will mention Band ( B1, B3, B7, B8, B38, B40, etc ) name only, or some other maybe use prefix words PRX ( primary rx ) and DRX ( diversity rx ) in the Netname to mention the use of this frequencies for 3G and 4G, or some other mention name of the networks, such as DCS ( 1800 Mhz ), PCS ( 1900 Mhz ), IMT ( 2100 Mhz ) etc.

This is Table of Band ( range / group of frequencies ) that used for cellular RF, including their Range of Upling and Downlink, all Cellular operator / Provide need to choose whic Frequencies that they wanna use to provides their services, ofcourse they need to follow the regulation in their countries.

Please note that your 4G ( LTE ) maybe use same frequencies with 2G ( GSM ) in your countries, its depend on Telecomunicaton Ministry / Departement on your country, some countries already 2300 Mhz and 2600 Mhz ( recomended ) some countries not using it yet, 4G networks / LTE support both frequency division duplexing (FDD) and time-division duplexing (TDD). I hope from now on, we know what the meaning of thoose Band 1 / B1, Band 2 / B2, Band 3 / B3, Band 8 / B8 etc, ww know LTE, UMTS / WCDMA, PRX, DRX, FDD, TDD, and all things that mention in this post, in any of mobilephone schematics specially RF cellular blocks, atleast i hope this simple post motivate you search more of literature of it

Lets learn togather

Yongky Felaz
Pragmafix team

Over the past few years, there has been an explosion in the mobile data usage mostly due to the increasing number of tablets and smart phones in use. To support such demand, wider transmission bandwidths are needed, and hence, the technique of Carrier Aggregation (CA) has been introduced in 4G cellular systems. This enables scalable bandwidth expansion beyond the single LTE carrier by aggregating two or more LTE component carriers of similar or different baseband bandwidth, which can be chosen from the same 3GPP frequency band (intra-band) or different 3GPP frequency bands (inter-band). Furthermore, CA is supported by both FDD and TDD modes, and this offers the optimum flexibility in the way the spectrum is utilized and how the network scheduling is configured. In order to push towards 5G data rates (>1Gbps), leveraging more antennas and transmitting more bits per symbol to increase spectral efficiency requires the use of MIMO and higher-order modulation techniques. This presentation focuses on discussing the RF system architectural challenges for Advanced-LTE based user equipment (UE) radio, and the resultant increased complexity in the radio due to the use of CA, MIMO, and higher order modulation techniques; furthermore, concurrency and coexistence scenarios with other radio access technologies (RAT) are considered in how they further add to the complexity of the RF frontend and to its linearity requirements. In order to address this explosive demand for data rates and total mobile data consumption, manufacturers are called to increase data throughput of consumer
UE. A number of enabling features are being standardized and rolled out in commercial handset products.

The highest priority to date has been deployment of carrier aggregation (CA), which was introduced in the Third Generation Partnership Project’s (3GPP’s) Release 10, and involves the addition of more and more carrier bandwidth. CA essentially allows mobile operators to “widen the pipe” and enable higher data rates simply by the simultaneous use of more spectrum as a dedicated resource to a single user.
LTE is defined to support flexible channel band- widths from 1.4 MHz to a maximum of 20 MHz, but these critical extra channels (each up to 20 MHz wide) can be added within a defined band of operation (intra-band CA) or in additional different bands of operation (inter-band CA). The number of combinations of the channel allocations and combinations of bands employed for CA in the standard has exponentially grown over the last several years, The option for 4G ( LTE ) that implemented in our phone cellular RF part circuit :

1. HB ( High Band ) and LB ( Low Band ) inter-band CA with diversity / MIMO

2. Quad antenna RF Front End : 3 x CA + MIMO support

this circuit of RF need 4 antenna, additional filters on PRx, DRx and MIMO path ) This design of RF part inside our phone will use HB ( High Band ), MB ( Mid Band ) and LB ( Low Band ) will use 2x CA ( Band 1 + Band 3, Band 39 + Band 41, Band 3 + 41 , Band 1 + 26, Band 3 + Band 26 ) for example, and use 3 x CA ( Band 1 + Band 3 + Band 41, Band 1 + Band 3 + Band 26 ) and can be use 4 x 4 MIMO use Band 41, all thing that mention on picture above.

The application of multiple-input multiple-output (MIMO) spatial multiplexing effectively transmits multiple data streams (or layers) from a number of antennas at the transmitter to multiple antennas on the receiver. This application uses the spatial differences of the antenna reception and multi-path through varying radio environments of each data stream in order to separate out the overlying signals even though they are transmitted at the same frequency. This digital extraction of the signals based on known unique radio path transfer functions (derived from reference signals within each link) enables
a further multiplication factor of the data rate according to the number of transmit/receive antennas that are employed. As an example of the DL signals, if four data streams are transmitted from the base station (eNodeB) and four separated antennas with low envelope correlation coefficient are used for reception at the UE handset, this 4 x 4 DL MIMO link will be able to support two times the data rate of a 2 x 2 DL MIMO link (two antennas at the eNodeB and two antennas at the UE) and four times a single ( 1 x 1, or single-input single-output [SISO] ) antenna reception. The application of MIMO requires SNR to function adequately and may require stronger signals with less interference and closer proximity to the eNodeB than a corresponding lower data rate SISO operation

Another RF design path, will use VLB ( Very Low Band ), VHB ( Very High Band ) and maybe UHB ( Ultra High Band ) based on distribution market countries. For Mobilephone RF platform that supports 2G / 3G / 4G cellular with diversity plus other RF connectivity ( WIFI / BT ) and GPS, at least fours / five antenna is needed.

1. Main LB / MB antenna ( lower )
Low Band : 700 MHz - 960 MHz
Mid Band : 1700 MHz - 2200 MHz

2. Main HB antenna ( upper )
High Band : 2300 MHz - 2700 Mhz

3. Diversity LB / MB antenna
Low Band : 700 MHz - 960 MHz
Mid Band : 1700 MHz - 2200 MHz

4. Diversity HB and GPS antenna
High Band : 2300 MHz - 2700 Mhz
GPS L1 Band: 1575.42 MHz
GPS L2 Band: 1227.6 MHz
GPS L5 Band: 1176.45 MHz

5. WiFi ( WLAN ) 2G / 5G & Bluetooth
Bluetooth Standart 802.15.1 : 2400 MHz - 2480 MHz
WiFi Standart 802.11 b/ g /ax : 2400 MHz - 2480 MHz
WiFi Standart 802.11 a / h / j / n / ac : 5100 MHz - 5900 MHz


Yongky felaz
pragmafix team

I Have Two Example implementation options for primary PA+Duplexer+ASM module (PAiD) carrier aggregation support of
B8/B1, B8/ B3, B8/B7, B1/B3/B7, B1/B3/B40, B7/B40, B1/B41, B3/B41, and B39/B41 :

a) Permanently ganged N-plexer filter configuration
b) More optimal switch-combined approach having lower loading loss and less filter duplication

For the first case, where the harmonic of a lower frequency band falls into a CA partnerreceive band, there is an example shown in Fig.3 depicting the specific cases of B8/B3 (2nd harmonic of B8 Tx 880–915 MHz falls into the B3 Rx band 1805–1880 MHz) and B8/B7 (3rd harmonic of B8 Tx 880-915 MHz falls into the B7 Rx band 2620–2690 MHz). The harmonic levels (around–10 dBm) are significantly higher than the typicalnoiseof the transmitter and must be attenuated to a level below –85 dBm before the low band input of the diplexer in order to avoid desensing theB3 and/or B7 primary/diversity receivers. Multiple additional isolations within the front-end mustbe well below this challenging attenuation of the conductive path. Overall harmonic management is a difficult balance of shielding, distributed lowloss
harmonic filtering, and grounding for optimal isolation that is critically aided by integrationand proper partitioning of PA+Duplexer+Switchmodule packages (PAiDs). The second primary challenge is related to the merging of closely spaced bands, and an example of this is alsoshown in the two example implementations on the picture above, On the left a), closely spaced bands are permanently ganged together in large groups, so-called N-plexer filter arrays, demonstrated here with a 7-plex to deliver B1/B3/B7, B1/B3/B40,and B7/B40, a 5-plexer to deliver B1/B41 andB3/B41, and a diplexer to deliver B39/B41. Thisapproach is a common brute force architecturethat leverages a fixed set of specific CA combinations, and enables less calibration for thefewer possible RF path configurations, but with-
out co-design with the antenna switch to enable reconfiguring or switching filter combinations inand out using the switch. The increasing loadinglosses as more filters are ganged, along with theinflexible configuration to address additional CA,is compounded here by the inability to gang filters whose passbands overlap, such as B39/B1/B3 and B7/B41. In order to deliver all of thesecombinations,
filters need to be duplicated in theganged arrangements at some cost and area penalty. In contrast, the solution on the right employs a flexibly configured switch able to simultaneously engage two arms to connect and join variouscombinations of filters for different CA pairings(e.g., the ASM switch arms on the picture below ( b ) connecting to both the B1B3 quadplexer and the B7 duplexer to achieve B1/B3/B7 3DL CA) . In the picture below you can see there was two option that might be implemented to various mobilephone : a) RFIC integrated LNA and optopn b) is external LNA in the RFFE.

Receiver antenna connectivity and link budget for 4 4 MIMO DL support

The design of these advanced diversity receive modules requires multiple technologies optimized for switching, acoustic filtering, and active LNAs, which must be co-designed to leverage the benefits of hybrid assembly in multi-chip module packaged integration. The filter itself is specifically matched to the input impedance of the LNA, minimizing trace loss and other matching transformation insertion losses for the lowest noise figure. Thus, managing out-of-band attenuation requirements, all with careful co-design of other filters that may be switch-combined in CA pair- ing within the same module as described earlier,
is important. The discrete solution is unable to switch-combine filters in flexibly programmed CA pairings due to long trace losses and phase shifts on the phone PCB, and the overall discrete solution
is commonly twice as large as the integrated module containing comparable band support. As more bands become required, the size advantage of the integrated solution will become even greater.

The higher frequency bands (> 1.7 GHz) within the UE are all candidates to support 4 x 4 MIMO on the DL. However regional operator demand for the feature and whether the UE is designed as a global smartphone to support all regional requirements will determine the number of bands, and which ones, are populated to support 4 x 4 MIMO. An example of a global diversity receive module is shown in the block diagram on the previous picture that supports B1/B25/B3/B4/B39 (mid bands) and B30/B40A/B7/B41 (high bands) and all associated globallyrequired CA combinations. This module serves asa CA-capable MB/HB diversity receive module,but can also be placed additionally to support 4 4 MIMO in the DL of these same bands withconnection to the other available antenna feed.

Many of mobilephone technician doesnt know about the basic of RF circuit inside mobilephone, so they have some difficulties to repair RF problem, after this chapter I will continue to explain the RF circuit inside mobilephone, i will use some mobilephone models, we wil explore all things of RF part, and will found many netname and components such as : ASM ( Antenna Switch Module ) Filter, Front End Module ( FEM ) Diversity RX ( DRX ) , Primary RX ( PRX ), Low Noise Amplifier ( LNA ), Duplexer , Power Amplifier ( PA ) i will select some of mobilephones to explain use schematics and bitmap inside pragmafix, let me know if you have special request which of mobilephone models / type that you want me to explain, please reply here


Yongky Felaz