Dual-band Single-Ended-Input Direct-Conversion DVB-H Receiver

Abstract

Microtune, Plano, TXDVB-H is a new standard that is expected to be widely deployed in future mobile devices. The first DVB-H field trials were held in Europe and used the UHF band. Since then, DVB-H has also been targeted for deployment in the United States using L-band spectrum between 1670MHz and 1675MHz. There has also been discussion of reallocating European L-band DAB frequencies for DVB-H service. In this paper, a dual-band DVB-H tuner, designed to cover UHF band IV, V, and L-band applications, is presented.During the initial phase of UHF DVB-H deployment, it is expected that the existing DVB-T infrastructure will be leveraged. DVB-H receivers require a lower NF than stationary antenna DVB-T systems that take advantage of line-of-sight reception [1]. The mobile nature of DVB-H receivers requires that components be small and the consumer markets require that they be inexpensive. Previous published work relied on a 2-chip solution with an external balun for single-ended to differential conversion [2]. The presented solution is a single chip that eliminates the need for an external LNA and balun.The architecture of the receiver is shown in Fig. 33.3.1. The RF signal is routed to one of the three parallel cascode LNAs. The frequency band and the signal power determine the active LNA. For weak signals in the UHF band, a fixed-gain UHF LNA is available. For stronger signals, a similar LNA with a resistive divider input attenuator is selectable. This LNA maintains its OIP3 over the gain range at the expense of higher NF. The Lband LNA has a parallel LC load to provide a low NF and high gain at the resonant frequency.The receiver has 2 direct-conversion mixers to generate baseband quadrature signals. The mixer transconductance stage is shown in Fig. 33.3.2. To facilitate connection to the single-ended LNAs, each mixer has a single-ended voltage input and provides differential current outputs. Signals from the L-band and UHF paths are converted to differential currents by the differential pairs formed by Q1, Q2, and Q3. The mixer is the only device in the signal path that has to cover the entire frequency range from 470MHz to 1900MHz. The low-frequency operation requires a large capacitor to be connected to the base of Q3. An external capacitor is chosen because it is more cost effective. The differential currents are folded into the emitters of the mixing quad current sources Q4 and Q5 creating a low impedance at the collectors of the differential pairs. This low impedance provides several advantages. First, it minimizes the voltage swing at the collectors of Q1, Q2, and Q3 preventing saturation and allowing low voltage operation. Second, the low impedance helps extend the frequency range. Third, it reduces distortion contribution due to voltage modulation of the nonlinear collector-base capacitance. Fourth, LO-RF isolation is improved because Q4 and Q5 isolate the differential pairs from the mixing quad.The baseband anti-aliasing and channel selection filter is a 7 th -order Chebyshev type II filter with 80dB stop...

UHF Receiver Front-End: Implementation and Analog Baseband Design Considerations

“…1) If the undesired input power is dominated by channels dB 10 dB , then the first adjacent channel power is easily filtered by both Butterworth and inverse Chebyshev filters. In this case, lower order Butterworth filters (3)(4)(5) are quite effective compared with inverse Chebyshev filters.…”

Wideband VHF and UHF RF Front-End Receiver for DVB-H Application

“…But the thirdinput intercept point increases as much as the gain decreases. In low2 gain step,the biases of all transistors are turned offand all switches are off except SW 4 . The input signal passes through the passive elements to the output of LNA with 2 dB loss.…”

“…However, the size and costcompetitivenesscan be increased with the reduced number of required componentsif multiple bands,such as VHF and UHF bands, can be accommodated in asingle antenna and a single LNA [3][4][5].…”

A divide-by-3 frequency divider for I/Q generation in a multi-band frequency synthesizer

“…For example in some of the digital TV systems, the frequency bands of UHF (IV and V), VHF (III) and L-band have been allocated as is shown in Fig.1. As the frequency range of these systems is rather wide, most of the reported multi-band frequency synthesizers contain two or more VCO's with multiple inductors to cover the specified range ( [1], [2]). In these synthesizers, quadrature (I/Q) signals are usually generated by dividing the VCO's frequency by 2 n , using conventional divider stages.…”