RF Front End

Multi-mode multi-frequency requirements after joining LTE:

After joining LTE, the terminal not only requires the end to increase the LTE working frequency band on the basis of multimode, but also increases the frequency bands which can ensure the user to realize the international roaming. However

The global distribution of LTE bands is more and more discrete.

	Band	Upstream operating frequency	Downstream operating frequency	Use
Td_lte	40	2300-2400	2300-2400	China and overseas deployment bands
	38	2570-2620	2570-2620	China and overseas deployment bands
	41	2496-2690	2496-2690	Overseas Deployment Band
Fdd-lte	1	1920-1980	2110-2170	Japan, European Band
	7	2500-2570	2620-2690	Frequency bands in the European region
	17	704-716	734-746	US regional Band
	13	777-787	746-756	US regional Band
	20	832-862	791-821	Frequency bands in the European region
	4	1710-1755	2110-2155	North and South America bands
Td_wcdma	39	1880-1920	1880-1920	China Regional Band
	34	2010-2025	2010-2025	China Regional Band
Wcdma	1	1920-1980	2110-2170	Europe, Japan. Korea Regional deployment
	2	1850-1910	1930-1990	US regional Band
	5	824-849	869-894
Gsm	2	1850-1910	1930-1990	Overseas Deployment Band
	3	1710-1785	1805-1880	China and overseas deployment
	5	824-849	869-894	Overseas Deployment Band
	8	880-915	925-960	China and overseas deployment bands

Spectral division, in order to better utilize the radio wave resources.

High frequency and low frequency difference: The high frequency is more easily attenuated, so the need for greater transmission power, the corresponding need for more base to ensure signal quality.

But low frequency spectrum resources are not much, so LTE basically in high frequency.

The transmission rate of the data is independent of the frequency spectrum, which is only related to the spectral width, and the larger the frequency band, the more information can be carried in a single transmission.

Wireless communication module consists of chip platform, RF front-end, antenna.

The chip platform includes baseband chip, RF chip, power management chip. Baseband chip is responsible for the physical layer algorithm and high-level protocol processing, involving multi-mode interoperability implementation.

The RF chip is responsible for the mutual conversion between the RF signal and the baseband signal.

RF front end includes saw (surface acoustic wave, surface wave) filter, duplexer (duplexer), low pass filter (lower pass FILTER,LPF)

Amplifier (Power amplifer), switch. Saw is responsible for the RF signal filtering of the TDD system receiving channel, the duplexer is responsible for the duplex switching and receiving/transmitting of FDD system.

Channel RF signal filtering, the amplifier is responsible for the transmission channel RF signal amplification, switch is responsible for the receiving channel and the transmission channel mutual conversion.

The antenna is responsible for the mutual conversion between the RF signal and the electromagnetic signal.

The implementation of MULTIMODE interoperability relies mainly on baseband chips, and the increase in frequency bands has no effect on the area and cost of baseband chips, only the software needs to be upgraded.

Tdd-lte and Fdd-lte protocols differ little, mainly in duplex mode, in the physical layer.

The introduction of multimode and multi-frequency bands will have an effect on the RF chip, increasing the receiving channel and transmitting channel.

For TDD systems, the RF front-end is mainly composed of amplifiers, SAW, low-pass filters, switches.

For FDD systems, the RF front-end is mainly composed of amplifiers, duplexer, switches.

The multi-band realization mainly relies on the RF chip, the RF front end, the antenna.

RF Front End