Texas Instruments TRF1500 Surface Acoustic Wave SAW Filter, Low-Band LNA Output Configuration

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SWRA004A

Figure 5. Low-Band LNA Output Configuration

Surface Acoustic Wave (SAW) Filter

The SAW filter is used primarily as an image-reject filter (IRF). The image frequency (fIM) is located at the desired channel frequency (fCH) plus two times the IF frequency (fIF); fIM = fCH + (2 x fIF). The image frequency acts as an interferer to the system. During the down-conversion process, the image and the desired channel are both converted to a common IF. Left unfiltered, the image could completely mask the desired signal. The IRF rejects this image before the RF signal is introduced to the mixer.

By minimizing the image before it reaches the mixer, the sensitivity of the receiver is enhanced. To further minimize potential interferers, a band-select filter is typically used at the front of the receiver, before the LNA. The band-select filter passes only those frequencies that fall within the system receive band. In many TDMA systems, the duplexor acts as the band-select filter.

The off-chip SAW image-reject filter used on the TRF1500 applications board has a 3dB nominal insertion loss and a 25 MHz bandwidth at a center frequency of 880 MHz as shown in Figure 6.

Figure 6. SAW Filter Insertion Loss

S AW F ilter In sertio n L oss

	0
	-5
	-10
	-15
(dB)	-20
(dB)	-25
Loss	-25
Loss	-30
Insertion	-30
	-35
	-40

	-45
	-50
	-55
	-60
	860	900
		F req uen cy (M Hz)

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 Figures TablesTRF1500 Integrated Dual-Band RF Receiver User’s Guide AbstractProduct Support Ingl E Chip Anal OG AS E BRelated Documentation World Wide WebIntroduction Board Design and Impedance Matching Design ConsiderationsExternal Components TRF1500 Dual-Band Receiver Block Diagram TRF 1500 Dual-Band ReceiverPin Descriptions Pin Number Name DescriptionStrong Signal TRF1500 Control State Control State and the Corresponding Active CircuitsCascaded Block Diagram of the Low-Band Receiver Section Low-Band LNA Low-Band LNA Turn on TimeLow-Band LNA Input Low-Band LNA OutputLow-Band LNA Output Configuration Surface Acoustic Wave SAW FilterLow-Band Mixer Low-Band Mixer RF InputLow-Band Mixer LO Input Low-Band if OutputLow-Band if Output Configuration Low-Band LO Buffer Amplifier OutputLow-Band Buffer Amplifier Output Configuration LB LNA, LB Mixer, SAW Filter, and LB if Amp Parameters LOW-Band Cascaded Power Conversion GainLow-Band Cascaded Test Guide Low-Band Cascaded Power Conversion Gain Reduction Low-Band Cascaded Noise Figure TRF1500 Integrated Dual-Band RF Receiver User’s Guide Low-Band Cascaded RF Input Return Loss Low-Band Cascaded LO Input Return LossLOW Band LO Buffer Output Power Low-Band Power Leakage LO In to RFLow-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 RF Input High-Band LO InputHigh-Band LO Frequency Doubler Driven Configuration High-Band if Output Configuration High-Band if OutputHigh-Band LO Buffer Amplifier Output Configuration High-Band LO Buffer Amplifier OutputHB LNA, HB mixer, HB if amp High-Band Cascaded Power Conversion GainHigh-Band Cascaded Test Guide 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 Power Leakage LO In to RF High-Band Cascaded Third Order Input Intercept Point IIP3High-Band Cascaded 1dB Input Compression Point High-Band Cascaded 2X2 Spur Performance High Band 3X3 Spur Performance Low-Band and High-Band Transmit Mixer RF Input Low-Band and High-Band TransmitLow- and High-Band Transmit Mixer Low- and High-Band Transmit Mixer RF Input Configuration Low- and High-Band Transmit Mixer if Output ConfigurationLow-Band Transmit Performance Parameters Low-Band Transmit Mixer Power Conversion GainLow-Band Transmit Mixer Test Guide Low-Band Transmit Mixer Noise Figure Low-Band Transmit Mixer Input Return Loss Low-Band Transmit Mixer Power Leakage LO In to TX Low-Band Transmit Mixer Power Leakage TX In to LOLow-Band Transmit Mixer 1dB Input Compression Point See Appendix a Test Bench Setups See Appendix a Test Bench Setups High-Band Transmit Mixer Test Guide High-Band Transmit Mixer Performance ParametersLow-Band LNA Stand-Alone Test Guide Low-Band LNA GainLow-Band LNA Input Return Loss Low-Band LNA ParametersLow-Band LNA 1dB Input Compression Point Low-Band LNA Output Return LossLow-Band LNA Isolation 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 Parameters Low-Band Receiver Mixer Power Conversion GainLow-Band Receiver Mixer Stand-Alone Test Guide Low-Band Receiver Mixer Input Return Loss Low-Band Receiver Mixer Power Leakage LO In to RF Low-Band Receiver Mixer Noise FigureTRF1500 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