Fast Hopping Frequency Synthesizer Research Articles

Frequency-Hopped Quadrature Frequency Synthesizer in 0.13-$\mu$m Technology

This paper presents a Wireless-USB/WiMedia-compliant fast-hopping frequency synthesizer architecture with quadrature outputs based on sub-harmonic injection-locking. The synthesizer features a cross-coupled quadrature digitally-controlled oscillator, that is injection-locked to a sub-harmonic frequency. An intuitive closed-form expression for the dynamics of the quadrature injection-locked oscillator and a technique to achieve fast frequency-hopping, are presented. The overall architecture, based on this technique, is a CMOS-only implementation and has been fabricated in a 0.13-μm SiGe BiCMOS process. On-chip mixers have been implemented to measure the quadrature accuracy of the outputs. Measurement results indicate lock-times of less than 2.5 ns, a locked phase noise of -114 dBc/Hz at 1 MHz offset and a quadrature accuracy of better than 0.5°. The frequency synthesizer (excluding output buffers) occupies an area of 0.27 mm2 and consumes 14.5 mW of power. The best and worst case spur suppression achieved are 47 and 31 dB, respectively. This is the lowest power fast-hopping quadrature frequency synthesizer that has been reported to date.

Fast hopping frequency synthesizer using difference of phase errors

Fast frequency hopped–spread spectrum (FFH-SS) communication is a system that can realize excellent interference immunity, disturbance immunity, and security. In the implementation of this system, there must be a synthesizer that can switch the frequency with high speed. From such a viewpoint, the authors previously proposed a fast hopping PLL synthesizer, based on the initial value presentation in which the phase difference obtained by the phase comparator at the same frequency output of the previous period is reproduced by utilizing the periodicity of the frequency hopping. It is shown that the hopping frequency can be raised to one-third the reference frequency. In this method, however, the phase error of the VCO output generated in frequency switching produces an error in the phase difference reproduced by the phase comparator, which results in a stepwise error in the output frequency. In order to deal with this problem, a circuit for the phase error compensation was proposed, but there remained problems such as the difficulty of high-frequency operation. This paper proposes a fast hopping frequency synthesizer that solves those problems. In the proposed method, the phase difference is not reproduced by the phase comparator, and there is no effect from phase error of the VCO output generated in frequency switching due to the use of the difference of the phase errors. Faster operation is realized, with the hopping frequency equal to one-half the reference frequency. This helps to reduce the number of bits in the A/D converter below that of the D/A converter. © 1999 Scripta Technica, Electron Comm Jpn Pt 1, 82(10): 10–19, 1999