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Study on 0.4GHz to 2.7GHz High Linearity Upconverting Mixer
This document summarizes a study on the Linear Technology LT5578 0.4GHz to 2.7GHz high linearity upconverting mixer. It provides details on the mixer's features such as high output IP3, low noise floor, and high conversion gain. The document describes the mixer's block diagram, IF and LO input interfaces, and RF output interface. It also provides typical performance curves and an application circuit example for a 450MHz RF application.
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Study on 0.4GHz to 2.7GHz High Linearity Upconverting Mixer
- 1. Study on 0.4GHzto 2.7GHz High Linearity Upconverting Mixer. Source: Linear Technology
- 2. Introduction Purpose Studyon 0.4GHz to 2.7GHz High Linearity Upconverting Mixer. Outline Features and Application. Block Diagram of the device. IF and LO Input interface. RF output interface. Typical Performance Curve. Application Circuit. Content 13 pages
- 3. Features High OutputIP3: 27dBm at 0.9GHz and 24.3dBm at 1.95GHz. Low Noise Floor: –158dBm/Hz (POUT = –5dBm). High Conversion Gain: 1.4dB at 0.9GHz. Noise Figure: 8.6dB. Low LO-RF Leakage: –43dBm. Single-Ended RF and LO Ports. Low LO Drive Level: –1dBm. Single 3.3V Supply. 5mm × 5mm QFN24 Package (Pin Compatible with LT5579).
- 4. Applications GSM900PCS/1800PCS and W-CDMA Infrastructure. LTE and WiMAX Basestations. Wireless Repeaters. Public Safety Radios.
- 5. Block Diagram Themixer has 1.4dB conversion gain with integrated RF balun transformers that provide a single-ended RF output and LO. LT5578 delivers high dynamic range performance from 400MHz to 2.7GHz, supporting all of the allocated LTE broadband wireless services. At 900MHz, the mixer offers 27dBm Output IP3 linearity and best-in-class noise floor of -160.5dBm/Hz at an output level of -5dBm, enabling outstanding transmitter dynamic range.
- 6. IF Input InterfaceThe IF input is differential. Internal baluns are used to provide single- ended LO input and RF output ports. The LT5578 is intended for operation in the 0.4GHz to 2.7GHz frequency range. The IF inputs are tied to the emitters of the double-balanced mixer transistors. The optimum DC current in the mixer core is approximately 40mA per side, and is set by the external resistors, R1 and R2. The inductors and resistors must be able to handle the anticipated current and power dissipation.
- 7. LO Input InterfaceIF Input Return Loss with 70MHz LO Input Return Loss with 520MHz LO Input Circuit
- 8. RF Output InterfaceRF Output Circuit An internal RF transformer reduces the mixer core output impedance to simplify matching of the RF output pin. A center tap in the transformer provides the DC connection to the mixer core and the transformer provides DC isolation to the RF output. The low inductance of the internal transformer limits the performance at lower frequencies. The LT5578 relies on the back side ground for both RF and thermal performance. RF Output Return Loss with 450MHz
- 9. Application: 700to 950 MHz Output Matching 700 to 950 MHz Output Matching
- 10. 450MHz Application Schematicfor 450MHz RF Application with 70MHz IF and 520MHz LO To tune the LO port, a series 6.8pF and shunt 4.7pF capacitor are used. The LO port is tuned for high side LO injection at 520MHz. The matching networks for the three ports are shown. At the IF input, the 560pF capacitors are used mainly as DC blocks, but also help tune out the parasitic inductance of the transformer.
- 11. Typical Performance Gain, Noise Figure and OIP3 vs RF Frequency for the 2600MHz Application Return Loss Comparison: 740MHz (a), 900MHz (b) and 700MHz to 950MHz (c)
- 12. LT5578 Evaluation Board(DC1545A) LT5578 Evaluation Board (DC1545A)
- 13. Additional Resource Forordering LT5578, please click the part list or Call our sales hotline For more product information go to http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1011,C1723,P89043 Visit Element 14 to post your question www.element-14.com For additional inquires contact our technical service hotline or even use our “Live Technical Chat” online facility Newark Farnell
Editor's Notes
- #2 This is a study on the Linear Technology 0.4Ghz to 2.7Ghz High Linearity Upconverting Mixer.
- #3 Welcome to the training module on the LT5578. This training module Introduces the 0.4 GHz to 2.7GHz frequencies Upconverting Mixer Device and its typical applications.
- #4 The LT5578 mixer is a high performance up-converting mixer optimized for frequencies in the 0.4GHz to 2.7GHz range. The single-ended LO input and RF output ports simplify board layout and reduces system cost. The mixer needs only –1dBm of LO power and the balanced design results in low LO signal leakage to the RF output. The LT5578 offers a high performance alternative to passive mixers. Compared to alternative passive mixers' more than 8dB of conversion loss, the LT5578's 1.4dB conversion gain produces 9dB higher signal power without the need of an external high power, high linearity RF output amplifier stage.
- #5 The LT5578 is designed to satisfy the requirements of next generation LTE wireless base-station transmitters and improves the performance of wireless equipment including W-CDMA/UMTS, TD-SCDMA, CDMA2000, CDMA, and GSM/EDGE base-stations. The mixer is also ideal for a wide range of communications gear such as cable headend transmitters, microwave broadband transmitters, wireless repeaters, military radios, digital video broadcast systems, 2.4GHz ISM band transmitters, test instrumentation, micro-cell and pico-cell base-station applications.
- #6 The LT5578 operates from a single 3.3V supply, Typical quiescent supply current is 152mA. the mixer has 1.4dB conversion gain with integrated RF balun transformers that provide a single-ended RF output and LO (Local Oscillator) input to simplify designs while reducing external component count. Moreover, the device's LO input is internally buffered, requiring a drive level of only -1dBm. This results in an outstanding LO-to-RF leakage of -43dBm.
- #7 The IF input is differential. The LT5578 is intended for operation in the 0.4GHz to 2.7GHz frequency range, The purpose of the inductors (L1 and L2) is to reduce the loading effects of R1 and R2. The impedances of L1 and L2 should be at least several times greater than the IF input impedance at the desired IF frequency. The IF inputs are tied to the emitters of the double-balanced mixer transistors. The optimum DC current in the mixer core is approximately 40mA per side, and is set by the external resistors, R1 and R2. The inductors and resistors must be able to handle the anticipated current and power dissipation.
- #8 The simplified schematic for the single-ended LO input port is shown in this page. An internal transformer provides a broadband impedance match and performs single-ended to differential conversion. The primary winding is internally grounded, thus an external DC block may be necessary in some applications. The transformer secondary feeds the differential limiting amplifier stages that drive the mixer core. The measured return loss of the LO input port is plotted in this page for different application frequencies. The impedance match is acceptable from about 1.5GHz to beyond 3GHz, with a minimum return loss.
- #9 An internal RF transformer reduces the mixer core output impedance to simplify matching of the RF output pin. A center tap in the transformer provides the DC connection to the mixer core and the transformer provides DC isolation to the RF output. The RF pin is internally grounded through the secondary winding of the transformer, thus a DC voltage should not be applied to this pin.
- #10 The application shown in this page has a wider bandwidth than the 740MHz and 900MHz configurations. Using two additional components at the RF output allows the bandwidth to be extended to cover the range from 700MHz to 950MHz. Figure 11 compares the broadband return loss to the typical 740MHz and 900MHz return loss performance.
- #11 The LT5578 was evaluated for an application with an IF input at 70MHz, an RF output of 450MHz and a high side LO. The LO port is tuned for high side LO injection at 520MHz. At the IF input, the 560pF capacitors are used mainly as DC blocks, but also help tune out the parasitic inductance of the transformer. The 82pF differential capacitor and 3.3nH chip inductors provide an impedance transformation between the IF input pins and the transformer.
- #12 This Page gives typical Performance characteristics for the 2600MHz Application. The measured room temperature performance is plotted for both low side and high side LO drive. At 2600MHz, the gain is approximately –2.8dB with a noise figure of 11.2dB and OIP3 of about 22.2dBm. Low side LO yields slightly better overall performance than high side LO. The second curve compares the broadband return loss to the typical 740MHz and 900MHz return loss performance.
- #13 This page shows Evaluation Board details for the device LT5578.
- #14 Thank you for taking the time to view this presentation on “ LT5578 ” . If you would like to learn more or go on to purchase some of these devices, you may either click on the part list link, or simply call our sales hotline. For more technical information you may either visit the Linear Technologies site, or if you would prefer to speak to someone live, please call our hotline number, or even use our ‘live chat’ online facility. You may visit Element 14 e-community to post your questions.