Linear Technology baner vej for konfigurerbare LTE-platforme
Linear Technology introducerer LTC6946 synthesizeren med integrated VCO og mulighed for tuning over et meget bredt frekvensområde, så multiband applikationer kan adresseres (in english).
The relentlessly accelerating use of smart phones, tablets and network-centric devices continues to put pressure on mobile wireless network upgrades to alleviate congestion. The rush to deploy the next generation LTE network is gaining momentum. Virtually all wireless carriers have some sort of deployment plan for LTE, and the nascent LTE-ready smart phones further reinforce this trend.
But carriers are struggling to manage dissimilar standards and frequency spectrum as the industry navigates through successions of consolidation. The core issue facing carriers is that LTE is a new network overlay and carries with it an enormous build-out cost. Investments of such magnitude are warranted only if the new network has built in as much obsolescence-proof features as is reasonable. One cost-allaying strategy is to have a single, universally configurable platform – independent of standards.
Such requirements are rapidly gaining endorsements. Previously, specific carriers owned different 20MHz slivers out of the total available 60MHz frequency spectrum, allocated to serve various markets. The 60MHz may be divided among multiple carriers competing within a market. To realize a single platform, the bandwidth must increase from 20MHz to as high as 60MHz. Moreover, the system must now be made software-configurable to accommodate the different standards.
Increasing the operating bandwidth has significant performance impact. The technical reality is that for every doubling of the channel bandwidth, the wideband noise floor increases by a factor of 3dB. And as the industry pushes bandwidth to 60MHz, the network system degradation will be negatively impacted by a factor of about 4.8dB.
This degradation is a tough challenge to overcome. Engineers are already pushing their designs to the limit of their existing components by squeezing the last dB out of their transmitter and receiver performance. Clearly innovation is needed. The frequency carriers that are synthesized to power the transceivers often establish the fundamental noise floor by which the transceivers operate. Hence it is an important milestone that
LTC6946 synthesizer with integrated VCO has a built in wide frequency tunability range
Linear Technology’s new synthesizers with integrated VCO deliver phase noise and spurious product levels that improve on the current state of the technology. This enables the transmitters and receivers to operate at a lower noise floor, hence counteracting the negative noise impact by the opening of the bandwidth. So basestations can achieve their bandwidth goals without trading off performance.
The LTC6946 synthesizer with integrated VCO has a built in wide frequency tunability range to address the multiband requirement. LTC6946, the first device in a family of high performance integer-N frequency synthesizers with integrated VCO, delivering -226dBc/Hz normalized closed-loop in-band phase noise, superior -274dBc/Hz normalized in-band 1/f noise, and best-in-class -103dBc spurious output.
In a typical 900MHz application, these performance attributes help to achieve a closed-loop phase noise of -100dBc/Hz at 1kHz offset. The device is available in three frequency options: the LTC6946-1 tunes from 2.240GHz to 3.740GHz; the LTC6946-2 from 3.080GHz to 4.910GHz; and the LTC6946-3 covers 3.840GHz to 5.790GHz. In addition, each part has an on-chip output divider that is programmable from 1 through 6 to extend frequency coverage to as low as 373MHz.
This family of devices integrates a low noise 5.7GHz phase-locked loop (PLL), which includes a reference divider, phase-frequency detector (PFD) with phase-locked indicator, ultralow noise charge pump, and integer feedback divider to attain very low noise PLL operation. The PLL circuit is tightly coupled to a low noise VCO as well as internal self-calibration to ensure optimum VCO resonator tuning for best phase noise performance. The VCO requires no external components. The on-chip SPI compatible bidirectional serial port allows frequency tuning and control, and read back of register and loop status information.
The low phase noise and spurious capabilities of this family of frequency synthesizers enhance the performance of multiband basestations supporting LTE, W-CDMA, UMTS, CDMA, GSM and WiMAX standards. Its high frequency capability also supports point-to-point broadband wireless access, military, avionics, and high performance test and measurement applications.
The PLLWizard comprehensive PC-based design tool software is available to facilitate interactive control and interface with the LTC6946’s evaluation board. Designers can perform simulations and optimization with the PLLWizard software, and then interactively verify their designs on the actual demonstration circuit. The PLLWizard design tool software is available for download free of charge from the Linear Technology website at www.linear.com/synthesizers.
All versions of the LTC6946 are specified over the full case temperature range from
-40°C to 105°C. The products are available in a 4mm x 5mm, 28-lead plastic QFN package.
www.linear.com/product/LTC6946
