A unique single sideband upconversion architecture

24 April 2002 Telecoms, Datacoms, Wireless, IoT

In traditional transmit applications, a two-step upconversion occurs in which a baseband signal is modulated by one carrier to an IF then modulated a second time to the transmit frequency. The single-sideband upconversion architecture eases the filtering requirements by suppressing one of the unused sidebands. Coupling this approach with a direct RF analog modulator eliminates one mixing stage and can realise significant cost savings while maintaining exceptional performance.

Analog Devices is the only chip manufacturer that offers a two-chip solution to realise this architecture, with its AD9777 family of TxDAC+ converters and AD8345/AD8346 Direct RF analog modulators.

How it works

The idea behind image rejection or sideband suppression is to cancel out energy created in the sampling and mixing process.

The signal starts as a baseband I and Q component signal with a finite bandwidth. This baseband I/Q signal is mixed in the AD977x TxDAC+ at a fraction of the sampling clock, placing the carrier at a low IF. Without doing a complex mix, the DAC output spectrum would look like that shown in Figure B.

By engaging the complex mixer in the AD977x DAC, the orthogonal opposite sideband is produced in the selected channel (real or imaginary). When the complex signal is then mixed in an analog quadrature modulator, one of the sidebands is cancelled and the desired band is increased in power by 3 dB. The LO leakage can be minimised by calibrating the I/Q channel offset matching and filtering using a single SAW filter stage.

Further reading:

Sigfox SA powers smart connectivity
Editor's Choice Telecoms, Datacoms, Wireless, IoT
Sigfox South Africa is carving out a unique role, delivering low-power, wide-area network connectivity designed specifically for Internet of Things applications.

Read more...

---

Modern LTE connectivity for IoT
Otto Wireless Solutions Telecoms, Datacoms, Wireless, IoT
Designed to meet the evolving requirements of industrial and commercial applications, the SIMCom A7681E LTE Cat-1bis module combines simplified hardware architecture with long lifecycle support in a compact package.

Read more...

---

Seeing through the noise
RF Design Editor's Choice Telecoms, Datacoms, Wireless, IoT
How Adaptive Long Coherent Integration (ALCI) delivers superior measurement and positioning performance where conventional receivers fall short.

Read more...

---

Optical Ethernet connectivity for rugged environments
Hiconnex Telecoms, Datacoms, Wireless, IoT
The rugged Stratos T2 Series media converter maintains high data throughput and durability in mission-critical applications in security, tactical, and military communications.

Read more...

---

Next-gen SPE
Altron Arrow Telecoms, Datacoms, Wireless, IoT
Next-generation 100/1000BASE-T1 Single Pair Ethernet PHYs integrate MACsec security, time sensitive networking, and functional safety.

Read more...

---

LTE migration for legacy devices
iCorp Technologies Telecoms, Datacoms, Wireless, IoT
Quectel’s EG800Q-GL offers a low-cost upgrade path from 2G communication for legacy M2M devices and payment terminals.

Read more...

---

Contactless IO-Link without wear
IOT Electronics Telecoms, Datacoms, Wireless, IoT
Phoenix Contact’s IO-Link couplers transmit up to 18 W of power and IO-Link data at speeds of up to 230,4 kbps across an air gap.

Read more...

---

High-power RF amplifier design best practices
RFiber Solutions Telecoms, Datacoms, Wireless, IoT
By focusing on practical design considerations and planning for real-world conditions, engineers can build amplifiers that perform consistently and remain reliable over time.

Read more...

---

Bluetooth Classic and LE Audio module
RF Design Telecoms, Datacoms, Wireless, IoT
Refresh legacy Bluetooth designs and unlock Bluetooth Core 6.0 LE Audio in one rugged, ready to implement module.

Read more...

---

HackRF Pro targets advanced RF
IOT Electronics Telecoms, Datacoms, Wireless, IoT
The SDR can operate across an extensive frequency range from 100 kHz to 6 GHz, making it suitable for a broad range of applications, including wireless testing, signal analysis, and emerging communications technologies.

Read more...

---