Texas Instruments TRF1500 manual Low-Band Mixer RF Input

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SWRA004A

Low-Band Mixer

The purpose of the mixer in a down-conversion receiver is to translate incoming signals from one frequency to another. The low-band mixer in the TRF1500 is a three port high-side injected circuit. The mixer takes two known input signals, a radio frequency (RF) signal and a local oscillator (LO) signal and mixes them together to create a sum and difference intermediate frequency (IF). High-side injection means the LO is higher in frequency than the RF by the IF frequency. The output of the mixer is the IF and contains the difference and the sum of the RF and LO signals.

The difference of the RF and LO signals is the desired IF frequency in a down-conversion receiver. The undesired signal, the sum of the RF and LO frequencies, can be attenuated by using a low pass filter. The low-band mixer section of the TRF1500 is a Gilbert cell design with open collector outputs. The Gilbert cell structure was used for its robust isolation and harmonic suppression characteristics.

The TRF1500 mixer typically achieves a noise figure of 7.5 dB with an input third order intercept point of 3.5 dBm. Stand-alone mixer performance can be ascertained by reconfiguring the evaluation board as noted on the datasheet.

Low-Band Mixer RF Input

Figure 7 details the mixer RF input configuration. The signal from the LNA passes through the external image-reject SAW filter and back into the device’s low-band mixer input terminal (MIX_IN_LOW_BAND). Minimal mixer input impedance matching is required. A high-pass shunt-L (L11) and series-C (C13) network are used for impedance matching the SAW filter output to the mixer RF input. The shunt inductor presents a short at the IF frequency. This configuration minimizes the IF leakage and prevents unwanted interfering signals at, or near, the IF frequency from degrading the mixer’s noise figure performance.

Figure 7. Low-Band Mixer RF Input Configuration

22	TRF1500 Integrated Dual-Band RF Receiver User’s Guide

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Contents TRF1500 Integrated Dual-Band RF Receiver User’s Guide Important Notice Trademarks PIC Telephone Contents Appendix a Test Bench Configuration Tables FiguresAbstract TRF1500 Integrated Dual-Band RF Receiver User’s GuideIngl E Chip Anal OG AS E B Product SupportWorld Wide Web Related DocumentationIntroduction Design Considerations External ComponentsBoard Design and Impedance Matching TRF 1500 Dual-Band Receiver TRF1500 Dual-Band Receiver Block DiagramPin Number Name Description Pin DescriptionsStrong Signal Control State and the Corresponding Active Circuits TRF1500 Control StateCascaded Block Diagram of the Low-Band Receiver Section Low-Band LNA Turn on Time Low-Band LNALow-Band LNA Output Low-Band LNA InputSurface Acoustic Wave SAW Filter Low-Band LNA Output ConfigurationLow-Band Mixer RF Input Low-Band MixerLow-Band if Output Low-Band Mixer LO InputLow-Band LO Buffer Amplifier Output Low-Band if Output ConfigurationLow-Band Buffer Amplifier Output Configuration LOW-Band Cascaded Power Conversion Gain Low-Band Cascaded Test GuideLB LNA, LB Mixer, SAW Filter, and LB if Amp Parameters Low-Band Cascaded Power Conversion Gain Reduction Low-Band Cascaded Noise Figure TRF1500 Integrated Dual-Band RF Receiver User’s Guide Low-Band Cascaded LO Input Return Loss Low-Band Cascaded RF Input Return LossLow-Band Power Leakage LO In to RF LOW Band LO Buffer Output PowerLow-Band Cascaded Third Order Input Intercept Point IIP3 Low-Band Cascaded 1dB RF Input Compression Point Low-Band Cascaded 1dB Blocking Point Block Diagram of the High-Band Receiver Section High-Band LO Input High-Band RF InputHigh-Band LO Frequency Doubler Driven Configuration High-Band if Output High-Band if Output ConfigurationHigh-Band LO Buffer Amplifier Output High-Band LO Buffer Amplifier Output ConfigurationHigh-Band Cascaded Power Conversion Gain High-Band Cascaded Test GuideHB LNA, HB mixer, HB if amp High-Band Cascaded Power Conversion Gain Reduction High-Band Cascaded Image Rejection High-Band Cascaded Noise Figure High-Band Cascaded RF Input Return Loss High-Band LO Buffer Output Power High-Band Cascaded Third Order Input Intercept Point IIP3 High-Band Cascaded Power Leakage LO In to RFHigh-Band Cascaded 1dB Input Compression Point High-Band Cascaded 2X2 Spur Performance High Band 3X3 Spur Performance Low-Band and High-Band Transmit Low- and High-Band Transmit MixerLow-Band and High-Band Transmit Mixer RF Input Low- and High-Band Transmit Mixer if Output Configuration Low- and High-Band Transmit Mixer RF Input ConfigurationLow-Band Transmit Mixer Power Conversion Gain Low-Band Transmit Mixer Test GuideLow-Band Transmit Performance Parameters Low-Band Transmit Mixer Noise Figure Low-Band Transmit Mixer Input Return Loss Low-Band Transmit Mixer Power Leakage TX In to LO Low-Band Transmit Mixer Power Leakage LO In to TXLow-Band Transmit Mixer 1dB Input Compression Point See Appendix a Test Bench Setups See Appendix a Test Bench Setups High-Band Transmit Mixer Performance Parameters High-Band Transmit Mixer Test GuideLow-Band LNA Gain Low-Band LNA Stand-Alone Test GuideLow-Band LNA Input Return Loss Low-Band LNA ParametersLow-Band LNA Output Return Loss Low-Band LNA IsolationLow-Band LNA 1dB Input Compression Point Low-Band LNA Noise Figure Low-Band LNA Third Order Input Intercept Point IIP3 TRF1500 Integrated Dual-Band RF Receiver User’s Guide Low-Band Receiver Mixer Power Conversion Gain Low-Band Receiver Mixer Stand-Alone Test GuideLow-Band Receiver Mixer Parameters Low-Band Receiver Mixer Input Return Loss Low-Band Receiver Mixer Noise Figure Low-Band Receiver Mixer Power Leakage LO In to RFTRF1500 Integrated Dual-Band RF Receiver User’s Guide Low-Band Receiver Mixer 1dB RF Input Compression Point 12.2 11.4 10.4 ←1dB Compression Point TRF1500 Integrated Dual-Band RF Receiver User’s Guide Appendix a Test Bench Configuration Test Bench Setup Noise Figure Test Bench Setup Power Leakage RF In to LO In Measurements Test Bench Setup LNA 1dB Input Compression Point