Journal of Electrical and Computer Engineering

Volume 2016, Article ID 2138794, 6 pages

http://dx.doi.org/10.1155/2016/2138794

## A Four Quadrature Signals’ Generator with Precise Phase Adjustment

^{1}College of Mechanical and Electrical Engineering, China Jiliang University, Hangzhou 310018, China^{2}Jiangsu Key Laboratory of ASIC Design, Nantong University, Nantong, China

Received 13 February 2016; Revised 13 April 2016; Accepted 28 April 2016

Academic Editor: Ahmed M. Soliman

Copyright © 2016 Xiushan Wu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

#### Abstract

A four-way quadrature signals generator with precise phase modulation is presented. It consists of a phase precision regulator and a frequency divider. The phase precision regulator generates two programmable currents by controlling the conduction of the tail current sources and then changes the currents into two bias voltages which are superimposed on the clock signals to adjust the phase difference of the four quadrature signals generated by the frequency divider, making the phase difference of 90 degrees. The four quadrature signals’ generator with precise phase modulation has been implemented in a 0.18 *μ*m mixed-signal and RF 1P6M CMOS technology. The size of the chip including the pads is . The circuit uses a supply voltage of 1.8 V, a bias current of 7.2 *μ*A, and the bits of phase-setting input level in the design. The measured results of the four orthogonal signals’ phase error can reach ±0.1°, and the phase modulation range can reach ±3.6°.

#### 1. Introduction

The method of integrated orthogonal signal generator is RC-CR phase-shift method, and the RC-CR phase-shift network can be achieved by the input signal phase shift of 45 degrees. In the literature [1], the design of* I/Q* generator is used in the S band, its unbalance amplitude is 0.1 dB, and the unbalance phase is 0.1 degrees. But this method cannot adjust the phase of the signals. The method of RC-CR network is complex, and once integrated, it cannot be used for phase error compensation. In addition, the capacitor and resistance should not be too large; otherwise integrated circuit is also difficult to be integrated in the chip. The second method often uses quadrature voltage-controlled oscillator cross coupling method. In the literature [2], a QVCO which is low in power consumption is manufactured and used in 2.4 GHz PLL. This design reduces power consumption and improves the noise coefficient, but the unbalance of* I/Q* phase is 2.21 degrees and the phase cannot be adjustable. Then the digital quadrature signal generator is used to generate orthogonal signals [3–6], but the phase error of the signal is not adjustable and compensated. In the previous study [7], the quadrature phase error caused by the mismatch of the capacitor is very large, and this phenomenon is more serious with the increase of the frequency. The more important problem is that the implemented integrated circuit is able to generate orthogonal signals, and the phase difference of the orthogonal signal is exactly 90 degrees in the early simulation stage. However, after the chip is processed, the phase difference often deviates from 90 degrees due to the limitation of the technology of integrated circuit production. Therefore, an integrated precise adjustment circuit structure is needed to compensate quadrature signals for the phase deviation caused by the integrated circuit process.

In this paper, an integrated four quadrature signals’ generator is presented. The generator cannot only produce four orthogonal signals, but also can generate a programmable current by controlling the conduction of the tail current sources. The current is converted into a bias voltage superimposed on the clock signal to adjust the phase difference of the four signals, so as to make the phase difference be 90 degrees.

#### 2. Circuit Design

As shown in Figure 1, the structure of the quadrature signals generator is composed of a phase precision regulator unit (Ph_reg for short) and a frequency divider. The phase precision regulator unit can produce a programmable current by controlling the conduction of the tail current sources, and then the current can be converted into a bias voltage superimposed on the clock signal to precisely adjust the phase change. The frequency divider which consists of two* D* triggers (DFFs) is used to generate the four quadrature signals. The SET_PHASE input level is represented by thick solid lines because it is an* n*-bit bus.