6 superhetero dyne receiver and lo frequencies

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Unformatted text preview: cy (TRF) receiver architecture. 2.1.3 Regenerative Receiver The TRF receiver became a practical commercial device only when the cost, and availability, of triode vacuum tubes made these devices available to the general public. Even before the dawn of AM broadcasting, and the subsequent popularity of the TRF receiver, a particularly ingenious concept was developed by Edwin Howard Armstrong, in 1912, which allowed him to develop a receiver with high gain, and narrow bandwidth, using only a single trio de. 2.3. THE SUPERHETERODYNE RECEIVER Radio Frequency (RF) section 71 Intermediate Frequency (IF) section Preselector RF amplifier filter IF filter IF amplifier Mixer Demodulator fI F fc Local Oscillator (LO) fLO Figure 2.6: Superhetero dyne receiver and LO frequencies. Consider a modulated input signal with carrier frequency fc which may be both angle- and amplitude-mo dulated in general: BB207 FM variable capacitance double diode Rev. 02 — 27 April 2004 Product data sheet 1. Product profile 1.1 General description The BB207 is a variable capacitance double diode with a common cathode, fabricated in silicon planar technology, and encapsulated in the SOT23 small plastic SMD package. 1.2 Features ! ! ! ! ! Excellent linearity Cd(1V): 81 pF; Cd(7.5V): 27.6 pF Cd(1V) to Cd(7.5V) ratio: min. 2.6 Very low series resistance Small plastic SMD package. 1.3 Applications ! Electronic tuning in FM-radio. 2. Pinning information Table 1: Discrete pinning BB207 Philips Semiconductors FM variable capacitance double diode 001aaa620 100 Cd (pF) 80 60 40 20 0 10!1 1 102 10 VR (V) f = 1 MHz; Tj = 25 °C. Fig 1. Diode capacitance as a function of reverse voltage; typical values. 103 IR (nA) 102 001aaa621 10!2 TCd (K-1) 10!3 001aaa622 frequency range that the receiver is to cover. In practice the IF frequency will either be smaller than fcmin or larger than fcmax . These two cases can be further subdivided, because there are two possible choices for the LO tuning range for each choice of IF. The image frequency and the separation between the desired and image frequencies (|f I M − fc |) are summarized in Table 2.1 for each of the four cases. Four types of single-conversion superhets Table 2.1: Generic Configurations for a Single-conversion Superheterodyne Receiver (1) High LO Low LO Up - conversion: (1a) fLO = fIF + fc (1b) fLO = fIF − fc fIF > fcmax > fcmin fI M = fc + 2f I F fI M = 2f I F − fc (2) High LO Low LO Down - conversion: (2a) fLO = fIF + fc (2b) fLO = fc − fIF fIF < fcmin < fcmax fI M = fc + 2 f I F fI M = |fc − 2fI F | |fI M − fc | = 2fI F |fI M − fc | = 2fLO |fI M − fc | = 2fI F |fI M − fc | = 2fI F |fI M − fc | = 2fLO if if fc > 2f I F fc < 2f I F Note: In cases (1a) and (1b) (i.e. upconversion) fIM > fcmax . This means that images are always above the highest carrier frequency of interest and therefore outside the band of interest. A fixed preselector filter can be used to pass the entire band of interest while still rejecting images. LPF Superheterodyne A/D BW/2 0◦ DSP-Demodulator 90◦ LPF fIF A/D BW/2 (a) Digital Signal Processor LPF Low IF Image-reject mixer BW/2 A/D 0◦ Demodulator 90◦ LPF fIF BW/2 (b) LPF Zero-IF A/D BW/2 0◦ DSP-Demodulator 90◦ LPF A/D BW/2 (c) 19-2135; Rev 1; 8/02 315MHz Low-Power, +3V Superheterodyne Receiver The MAX1470 is a fully integrated low-power CMOS superheterodyne receiver for use with amplitude-shiftkeyed (ASK) data in the 315MHz band. With few required external components, and a low-current power-down mode, it is ideal for cost- and power-sensitive applications in the automotive and consumer markets. The chip consists of a 315MHz low-noise amplifier (LNA), an image rejection mixer, a fully integrated 315MHz phase-lock-loop (PLL), a 10.7MHz IF limiting amplifier stage with received-signal-strength indicator (RSSI) and an ASK demodulator, and analog baseband data-recovery circuitry. The MAX1470 is available in a 28-pin TSSOP package. Applications Remote Keyless Entry Features o Operates from a Single +3.0V to +3.6V Supply o Built-In 53dB RF Image Rejection o -115dBm Receive Sensitivity* o 250µs Startup Time o Low 5.5mA Operating Supply Current o 1.25µA Low-Current Power-Down Mode for Efficient Power Cycling o 250MHz to 500MHz Operating Band (Image Rejection Optimized at 315MHz) o Integrated PLL with On-Board Voltage-Controlled Oscillator (VCO) and Loop Filter o Selectable IF Bandwidth Through External Filter o Complete Receive System from RF to Digital Data Out Garage Door Openers Remote Controls *See Note 2, AC Electrical Characteristics. Wireless Sensors Wireless Computer Peripherals Ordering Information Security Systems Toys Video Game Controllers Medical Systems PART TEMP RANGE PIN-PACKAGE MAX1470EUI -40°C to +85°C 28 TSSOP Typical Application Circuit appears at end of data sheet. Pin Configuration appears at end of data sheet. Functional Diagram LNAOUT 6 MIXIN1 8 MIXIN2 9 MIXOUT IFIN1 IFIN2 12 17 18 MAX1470 General Description Ordering Information Wireless Computer Peripherals Security Systems Toys Video Game Controllers PART TEMP RANGE PIN-PACKAGE MAX1470EUI -40°C to...
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This test prep was uploaded on 03/13/2014 for the course ECE 453 taught by Professor Staff during the Spring '08 term at University of Illinois, Urbana Champaign.

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