A major revolution in receiving, and watching TV programs is, ahead of us. Small TV receivers, are being integrated in dedicated, portable devices, PDAs and even, cellphones for convenient TV, viewing. These small devices can, receive digital terrestrial signals, such as DVB-T and DVB-H. It is, important for the tuner to have, excellent sensitivity, low form factor, and low power consumption.

The block diagram of a silicon, tuner that can handle 3.3V or 2.8V, power supply is shown in Figure 1 below.

Figure 1: The TUA9001 silicon tuner integrates more than 150 discrete components used in MOPLL-based tuners.

The TUA9001 includes most of, the necessary RF blocks in the IC,, integrating more than 150 discrete, components used in mixer oscillator, PLL (MOPLL)-based tuners., In an RF tuner using TUA9001,, the LNA is external, giving flexibility, to maximize the sensitivity (low noise figure) or the linearity, (Adjacent Channel Interference or, ACI performance).

One example, of the BGA728L7 LNA has low, power consumption at 1.8V to, 3.3V. Its gain can be switched between, a "high" +16dB to provide, high sensitivity (@ 1.3dB) to a "low", -5dB which provides high linearity., TUA9001, together with BGA728L7,, achieves a total noise figure of only, ~2.5dB. Also, the BGA728L7 can be, switched on and off in a few microseconds,, supporting the time, slicing feature used for DVB-H.

DVB-T tuner design
Reference designs that support, various digital standards help, reduce development time and, time-to-market. At the same, time, they ensure that constraints, required for mobile receivers are, met while complying with standards, like Mobile and Portable, DVB-T Radio Access Interface, (MBRAI) and NorDig.

Such reference, designs include network, interface modules (NIMs) for standards, such as DVB-T and China, Multimedia Mobile Broadcasting, (CMMB) including various baseband, ICs available on the market.

Figure 2: This DVB-T reference design ensures compliance with standards while achieving lower BOM, smaller form factor, and lower-power consumption than conventional CAN NIMs.

Figure 2 above shows one of these, reference designs for DVB-T., This reference design has SMD, components on only one side of, the PCB. Thus, the whole DVB-T, tuner is housed in a 2 square centimeter area.

It enables the development of a, NorDig-compliant tuner based, on the TUA9001 and achieves a, lower BOM, smaller form factor, and lower power consumption, compared with conventional CAN, NIMs. The RF signals from a single, antenna will be amplified in the, LNA using a low-cost RF transistor, such as the BFR380.

The frequency, split in the two reception bands,, VHF BIII (170MHz to 240MHz), and UHF (470MHz to 960MHz), is, performed with a diplexer, which, is needed due to the single antenna, input only (not needed, if individual VHF/UHF antennas, will be used). The performance, on this diplexer depends on the, required ACI performance; several, designs are available to cover all, ACI NorDig cases with the desired, margin.

The RF signal is lead to the, TUA9001 where it is further ampli-, fied, frequency converted in the, I/Q demodulator and filtered., The TUA9001 has two integrated, AGC blocks.

One is a, broadband RF AGC with internal, detector, which does not require, any control or feedback signal, from the baseband demodulator., The other is a narrowband, AGC that controls the gain in the, baseband programmable gain, filter.

The narrowband AGC can, be controlled by the baseband, demodulator via an analog voltage, (e. g. from a filtered PWM, signal) or by a dedicated AGC bus, for faster and disturbance-free, amplitude control. An I2C or a, three-wire-bus is used to control, the IC parameters, whereby two, different modes can be set: one, for best IC linearity performance, and the other for lowest IC power, consumption.

The choice of which, mode will be used is determined, based on system requirements., For example, STB manufacturers, may opt for high-linearity setting,, while cellphone manufacturers, would prefer the low-power consumption, setting.

The reference design includes, a 26MHz crystal for smallest size, and excellent resulting phase, noise. The measured phase noise, is around -100dBc/Hz @1kHz. It integrates, phase noise power lower, than 10mrad leading to a SNR, caused by phase noise of 40dB, and above. It is also estimated, that this performance would be, sufficient to handle a 256-QAMand, even a 1,024-QAM-OFDM as, planned in the emerging standard, DVB-T2.

The reference design in Figure 2 above could be easily adopted, directly on the PCB of an STB,, USB dongle or any other mobile, devices. The reference design is, based on a four-layer PCB. Since all, the oscillators are integrated into, the TUA9001, there is little or no, shielding necessary to avoid disturbances, that observe the basic, EMC rules.

Meeting MBRAI
Other reference designs with, TUA9001 are also available for, DVB-T and DVB-H targeting, MBRAI. Due to more stringent, requirements in sensitivity and, linearity, the high performance, BGA728L7 LNA has been used,, where sensitivities of -99dBm will, be achieved.

Test measurements, done using the BGA728L7 show, sensitivity levels of -100dBm for, CMMB. The TUA9001 is already, being adopted by customers for, mobile phone and portable media, player applications.

For applications using the time, slicing mode, the receiver will be, switched on during the reception, of the desired service only., Both TUA9001 and BGA728L7 or, BFR380 in the reference designs, have this embedded capability.

The switching time of TUA9001, and BGA728L7 is below 1ms, while, the BFR380 requires ~1.5ms. One, advantage of using the BGA728L7, is the possibility to reduce its gain, if the input signal is very high like, in the case of ACI.

First test results, showed the capability of the LNA, able to handle more than 0dBm, input level in the low-gain mode., Switching its gain from low to, high, this LNA achieves the best, of what a RF amplifier can offer: low noise and high linearity.

For, devices with strong requirements, on ESD protection at the antenna, input, the diode ESD0P4RFL in, TSLP-4 package can be used., With only 0.4pF line capacitance, and ±15kV air/contact discharge, protection, this diode suits such, application well.

The transition from conventional, MOPLL ICs to silicon, tuners has already begun for, purely digital stationary and most, mobile applications. They offer, the advantages of form factor, reduction, lower power, linearity, performance sensitivity as well as, easy implementation.

Claus Muschallik is Director of Tuner Systems and TV Receiver, System Support, at Infineon Technologies, Asia Pacific Pte Ltd